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  • 2015-2019
  • 2000-2004  (57)
  • 1955-1959  (621)
  • 1890-1899  (177)
  • 1830-1839
  • 2003  (57)
  • 1957  (621)
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  • Chemical Engineering  (111)
  • ddc:000  (57)
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  • 2015-2019
  • 2000-2004  (57)
  • 1955-1959  (621)
  • 1890-1899  (177)
  • 1830-1839
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  • 1
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    On Non-Rank Facets of Stable Set Polytopes of Webs with Clique Number Four (2003)
    Details
    Publication Date: 2014-11-10
    Description: Graphs with circular symmetry, called webs, are relevant w.r.t. describing the stable set polytopes of two larger graph classes, quasi-line graphs and claw-free graphs. Providing a decent linear description of the stable set polytopes of claw-free graphs is a long-standing problem. However, even the problem of finding all facets of stable set polytopes of webs is open. So far, it is only known that stable set polytopes of webs with clique number $\leq 3$ have rank facets only while there are examples with clique number $〉4$ having non-rank facets.
    Keywords: ddc:000
    Language: English
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  • 2
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    Multiscale Analysis for the Bio-Heat Transfer Equation (2003)
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    Publication Date: 2014-02-26
    Description: The bio-heat transfer equation is a macroscopic model for describing the heat transfer in microvascular tissue. In [{\sl Deuflhard, Hochmuth 2002}] the authors applied homogenization techniques to derive the bio-heat transfer equation as asymptotic result of boundary value problems which provide a microscopic description for microvascular tissue. Here those results are generalized to a geometrical setting where the regions of blood are allowed to be connected. Moreover, asymptotic corrector results are derived.
    Keywords: ddc:000
    Language: English
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  • 3
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    Polyhedral Investigations on Stable Multi-Sets (2003)
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    Publication Date: 2014-11-10
    Description: Stable multi-sets are an evident generalization of the well-known stable sets. As integer programs, they constitute a general structure which allows for a wide applicability of the results. Moreover, the study of stable multi-sets provides new insights to well-known properties of stable sets. In this paper, we continue our investigations started in [{\sl Koster and Zymolka 2002}] and present results of three types: on the relation to other combinatorial problems, on the polyhedral structure of the stable multi-set polytope, and on the computational impact of the polyhedral results. First of all, we embed stable multi-sets in a framework of generalized set packing problems and point out several relations. The second part discusses properties of the stable multi-set polytope. We show that the vertices of the linear relaxation are half integer and have a special structure. Moreover, we strengthen the conditions for cycle inequalities to be facet defining, show that the separation problem for these inequalities is polynomial time solvable, and discuss the impact of chords in cycles. The last result allows to interpret cliques as cycles with many chords. The paper is completed with a computational study to the practical importance of the cycle inequalities. The computations show that the performance of state-of-the-art integer programming solvers can be improved significantly by including these inequalities.
    Keywords: ddc:000
    Language: English
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  • 4
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    Formation and structure of quasi-static cloud-layers in brown dwarf atmospheres (2003)
    Details
    Publication Date: 2014-02-26
    Description: In this paper, first solutions of the dust moment equations developed in [{\sl Woitke & Helling 2002}] for the description of dust formation and precipitation in brown dwarf and giant gas planet atmospheres are presented. We consider the special case of a static brown dwarf atmosphere, where dust particles continuously nucleate from the gas phase, grow by the accretion of molecules, settle gravitationally and re-evaporate thermally. Applying a kinetic description of the relevant microphysical and chemical processes for TiO$_2$-grains, the model makes predictions about the large-scale stratification of dust in the atmosphere, the depletion of molecules from the gas phase, the supersaturation of the gas in the atmosphere as well as the mean size and the mass fraction of dust grains as function of depth. Our results suggest that the nucleation occu in the upper atmosphere where the gas is cool, strongly depleted, but nevertheless highly supersaturated ($S\!\gg\!1$). These particles settle gravitationally and populate the warmer layers below, where the in-situ formation (nucleation) is ineffective or even not possible. During their descent, the particles grow up to radii $\approx\!0.3\,\mu{\rm m}\,...\,150\,\mu{\rm m}$, depending gas around the cloud base. The particles finally sink into layers which are sufficiently hot to cause their thermal evaporation. Hence, an effective transport mechanism for condensable elements exi considered solid/liquid material. In the stationary case studied here, this downward directed element transport by precipitating dust grains is balanced by an upward directed flux of condensable elements from the deep interior of the star via convective mixing (no dust without mixing). We find a self-regulation mechanism which leads to an approximate phase equilibrium ($S\!\approx\!1$) around the cloud base. The mass fraction of dust present in the atmosphere results be to approximately given by the mass fraction of condensable elements in the gas being mixed up.
    Keywords: ddc:000
    Language: English
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  • 5
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    Visualization of Time-Dependent Adaptive Mesh Refinement Data (2003)
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    Publication Date: 2020-03-09
    Description: Analysis of phenomena that simultaneously occur on quite different spatial and temporal scales require adaptive, hierarchical schemes to reduce computational and storage demands. For data represented as grid functions, the key are adaptive, hierarchical, time-dependent grids that resolve spatio-temporal details without too much redundancy. Here, so-called AMR grids gain increasing popularity. For visualization and feature identification/tracking, the underlying continuous function has to be faithfully reconstructed by spatial and temporal interpolation. Well designed interpolation methods yield better results and help to reduce the amount of data to be stored. We address the problem of temporal interpolation of AMR grid data, e.g.\ for creation of smooth animations or feature tracking. Intermediate grid hierarchies are generated by merging the cells on all refinement levels that are present in the key frames considered. Utilizing a clustering algorithm a structure of nested grids is induced on the resulting collection of cells. The grid functions are mapped to the intermediate hierarchy, thus allowing application of appropriate interpolation techniques.
    Keywords: ddc:000
    Language: English
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  • 6
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    Tensor Splats (2003)
    Details
    Publication Date: 2020-03-09
    Description: An improved general-purpose technique for the visualization of symmetric positive definite tensor fields of rank two is described. It is based on a splatting technique that is built from tiny transparent glyph primitives which are capable to incorporate the full directional information content of a tensor. The result is an information-rich image that allows to read off the preferred directions in a tensor field at each point of a three-dimensional volume or two-dimensional surface. It is useful for analyzing slices or volumes of a three-dimensional tensor field and can be overlayed with standard volume rendering or color mapping. The application of the rendering technique is demonstrated on general relativistic data and the diffusion tensor field of a human brain.
    Keywords: ddc:000
    Language: English
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  • 7
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    A construction for non-rank facets of stable set polytopes of webs (2003)
    Details
    Publication Date: 2014-11-10
    Description: Graphs with circular symmetry, called webs, are relevant for describing the stable set polytopes of two larger graph classes, quasi-line graphs [{\sl Giles and Trotter 1981, Oriolo 2001}] and claw-free graphs [{\sl Galluccio and Sassano 1997, Giles and Trotter 1981}]. Providing a decent linear description of the stable set polytopes of claw-free graphs is a long-standing problem [{\sl Grötschel, Lov\'asz, and Schrijver 1988}]. However, even the problem of finding all facets of stable set polytopes of webs is open. So far, it is only known that stable set polytopes of webs with clique number $\leq 3$ have rank facets only [{\sl Dahl 1999, Trotter 1975}] while there are examples with clique number $\geq 4$ having non-rank facets [{\sl e.g. Liebling et al. 2003, Oriolo 2001, P\^echer and Wagler 2003}]. In this paper, we provide a construction for non-rank facets of stable set polytopes of webs. We use this construction to prove, for several fixed values of $\omega$ including all odd values at least 5, that there are only finitely many webs with clique number $\omega$ whose stable set polytopes admit rank facets only.
    Keywords: ddc:000
    Language: English
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  • 8
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    Automatic Construction of Boundary Parametrizations for Geometric Multigrid Solvers (2003)
    Details
    Publication Date: 2020-11-13
    Description: We present an algorithm that constructs parametrizations of boundary and interface surfaces automatically. Starting with high-resolution triangulated surfaces describing the computational domains, we iteratively simplify the surfaces yielding a coarse approximation of the boundaries with the same topological type. While simplifying we construct a function that is defined on the coarse surface and whose image is the original surface. This function allows access to the correct shape and surface normals of the original surface as well as to any kind of data defined on it. Such information can be used by geometric multigrid solvers doing adaptive mesh refinement. Our algorithm runs stable on all types of input surfaces, including those that describe domains consisting of several materials. We have used our method with success in different fields and we discuss examples from structural mechanics and biomechanics.
    Keywords: ddc:000
    Language: English
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  • 9
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    Combinatorial Packing Problems (2003)
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    Publication Date: 2020-08-05
    Description: This article investigates a certain class of combinatorial packing problems and some polyhedral relations between such problems and the set packing problem.
    Keywords: ddc:000
    Language: English
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  • 10
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    Small Examples of Non-Constructible Simplicial Balls and Spheres (2003)
    Details
    Publication Date: 2014-02-26
    Description: We construct non-constructible simplicial $d$-spheres with $d+10$ vertices and non-constructible, non-realizable simplicial $d$-balls with $d+9$ vertices for $d\geq 3$.
    Keywords: ddc:000
    Language: English
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  • 11
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    A Lagrangian Approach for Integrated Network Design and Routing in IP Networks (2003)
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    Publication Date: 2014-11-11
    Description: We consider the problem of designing a network that employs a non-bifurcated shortest path routing protocol. The network's nodes and the set of potential links are given together with a set of forecasted end-to-end traffic demands. All relevant hardware components installable at links or nodes are considered. The goal is to simultaneously choose the network's topology, to decide which hardware components to install on which links and nodes, and to find appropriate routing weights such that the overall network cost is minimized. In this paper, we present a mathematical optimization model for this problem and an algorithmic solution approach based on a Lagrangian relaxation. Computational results achieved with this approach for several real-world network planning problems are reported.
    Keywords: ddc:000
    Language: English
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  • 12
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    Comparing Restoration Concepts using Optimal Network Configurations with Integrated Hardware and Routing Decisions (2003)
    Details
    Publication Date: 2014-02-26
    Description: We investigate the impact of link and path restoration on the cost of telecommunication networks. The surprising result is the following: the cost of an optimal network configuration is almost independent of the restoration concept if (i) the installation of network elements (ADMs, DXCs, or routers) and interface cards, (ii) link capacities, and (iii) working and restoration routings are simultaneously optimized. We present a mixed-integer programming model which integrates all these decisions. Using a branch-and-cut algorithm (with column generation to deal with all potential routing paths), we solve structurally different real-world problem instances and show that the cost of optimal solutions is almost independent of the used restoration concept. In addition, we optimize spare capacities for given shortest working paths which are predetermined with respect to different link metrics. In comparison to simultaneous optimization of working and restoration routings, it turns out that this approach does not allow to obtain predictably good results.
    Keywords: ddc:000
    Language: English
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  • 13
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    Average Case Analysis of a Hard Dial-a-Ride Problem (2003)
    Details
    Publication Date: 2020-11-13
    Description: In the dial-a-ride-problem (DARP) objects have to be moved between given sources and destinations in a transportation network by means of a server. The goal is to find a shortest transportation for the server. We study the DARP when the underlying transportation network forms a caterpillar. This special case is strongly NP-hard in the worst case. We prove that in a probabilistic setting there exists a polynomial time algorithm which almost surely finds an optimal solution. Moreover, with high probability the optimality of the solution found can be certified efficiently. We also examine the complexity of the DARP in a semi-random setting and in the unweighted case.
    Keywords: ddc:000
    Language: English
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  • 14
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    Asymptotic Mesh Independence of Newton's Method Revisited (2003)
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    Publication Date: 2019-01-29
    Description: The paper presents a new affine invariant theory on asymptotic mesh independence of Newton's method in nonlinear PDEs. Compared to earlier attempts, the new approach is both much simpler and more natural from the algorithmic point of view. The theory is exemplified at collocation methods for ODE boundary value problems and at finite element methods for elliptic PDE problems.
    Keywords: ddc:000
    Language: English
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  • 15
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    Smoothening Helps: A Probabilistic Analysis of the Multi-Level Feedback Algorithm (2003)
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    Publication Date: 2014-02-26
    Description: In this paper we introduce the notion of smoothed competitive analysis of online algorithms. Smoothed analysis has been proposed by [{\sl Spielman and Teng} STOC 2001] to explain the behaviour of algorithms that work well in practice while performing very poorly from a worst case analysis point of view. We apply this notion to analyze the Multi-Level Feedback (MLF) algorithm to minimize the total flow time on a sequence of jobs released over time when the processing time of a job is only known at time of completion. The initial processing times are integers in the range $[1,2^K]$. We use a partial bit randomization model, where the initial processing times are smoothened by changing the $k$ least significant bits under a quite general class of probability distributions. We show that MLF admits a smoothed competitive ratio of $O(max((2^k/\sigma)^3, (2^k/\sigma)^2 2^K-k))$, where $\sigma$ denotes the standard deviation of the distribution. In particular, we obtain a competitive ratio of $O(2^K-k)$ if $\sigma = \Theta(2^k)$. %The analysis holds for an oblivious as well as for a stronger adaptive %adversary. We also prove an $\Omega(2^{K-k})$ lower bound for any deterministic algorithm that is run on processing times smoothened according to the partial bit randomization model. For various other smoothening models, including the additive symmetric smoothening model used by [{\sl Spielman and Teng}], we give a higher lower bound of $\Omega(2^K)$. A direct consequence of our result is also the first average case analysis of MLF. We show a constant expected ratio of the total flow time of MLF to the optimum under several distributions including the uniform distribution.
    Keywords: ddc:000
    Language: English
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  • 16
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    A sample path relation for the sojourn times in G/G/1-PS systems and its applications (2003)
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    Publication Date: 2014-11-11
    Description: For the general G/G/1 processor sharing (PS) system a sample path result for the sojourn times in a busy period is proved, which yields a relation between the sojourn times under PS and FCFS discipline. In particular, the result provides a formula for the mean sojourn time in G/D/1-PS in terms of the mean sojourn time in the corresponding G/D/1-FCFS, generalizing known results for GI/M/1 and M/GI/1. Extensions of the formula provide the basis for a two-moment approximation of the mean sojourn time in G/GI/1-PS in terms of a related G/D/1-FCFS.
    Keywords: ddc:000
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  • 17
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    Molecular Conformation Dynamics and Computational Drug Design (2003)
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    Publication Date: 2014-02-26
    Description: The paper surveys recent progress in the mathematical modelling and simulation of essential molecular dynamics. Particular emphasis is put on computational drug design wherein time scales of $msec$ up to $min$ play the dominant role. Classical long-term molecular dynamics computations, however, would run into ill-conditioned initial value problems already after time spans of only $psec=10^{-12} sec$. Therefore, in order to obtain results for times of pharmaceutical interest, a combined deterministic-stochastic model is needed. The concept advocated in this paper is the direct identification of metastable conformations together with their life times and their transition patterns. It can be interpreted as a {\em transfer operator} approach corresponding to some underlying hybrid Monte Carlo process, wherein short-term trajectories enter. Once this operator has been discretized, which is a hard problem of its own, a stochastic matrix arises. This matrix is then treated by {\em Perron cluster analysis}, a recently developed cluster analysis method involving the numerical solution of an eigenproblem for a Perron cluster of eigenvalues. In order to avoid the 'curse of dimension', the construction of appropriate boxes for the spatial discretization of the Markov operator requires careful consideration. As a biomolecular example we present a rather recent SARS protease inhibitor.
    Keywords: ddc:000
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  • 18
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    Nonlinear Optimization in Gas Networks (2003)
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    Publication Date: 2021-02-01
    Description: The operative planning problem in natural gas distribution networks is addressed. An optimization model focusing on the governing PDE and other nonlinear aspects is presented together with a suitable discretization for transient optimization in large networks by SQP methods. Computational results for a range of related dynamic test problems demonstrate the viability of the approach.
    Keywords: ddc:000
    Language: English
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  • 19
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    RNA 3D-Modeling (2003)
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    Publication Date: 2014-02-26
    Description: This article presents a new computational approach to the three-dimensional (3D) modeling of ribonucleic acid (RNA) sequences with unknown spatial structure. The main concept is a mapping of the query sequence onto the 3D structures of a suitable template RNA molecule. This technique called \textit{threading} has originally been developed for the modeling of protein 3D structures. The application to RNA systems bridges the information gap between the growing mass of RNA sequence data and the relatively limited number of available 3D structures. The new RNA threading method is demonstrated on a tRNA model system because sufficient representative 3D structures have experimentally been elucidated and deposited in the public databases. Nevertheless, the method is in principle transferable on all other RNA species. Algorithms are developed that decompose these template structures into their secondary structure elements and gather this information in a specific template database. The best template is chosen with public alignment and secondary structure prediction tools which are integrated in the RNA modeling module. The structural information gathered from the template and the best alignment is combined to establish a comprehensive 3D model of the query sequence. A range of complete tRNA structures has successfully been modeled with the RNA threading method. The prototype module visualizes the models and provides convenient access to the proposed 3D structures. Therefore, the method could give new insight into a variety of RNA systems which in the recent years have become increasingly important as potential new pharmaceutical agents.
    Keywords: ddc:000
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  • 20
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    Korean-German Bilateral Symposium on Scientific Computing (2003)
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    Publication Date: 2014-02-26
    Description: Collection of abstracts of the Korean-German Bilateral Symposium on Scientific Computing, Berlin January 15/16, 2004
    Keywords: ddc:000
    Language: English
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  • 21
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    Planung kostenoptimaler Informations- und Kommunikations-Infrastrukturen (2003)
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    Publication Date: 2014-11-11
    Description: Beim Entwurf und Ausbau von Informations- und Kommunikationsnetzwerken m{ü}ssen zahlreiche interdependente Entscheidungen getroffen und gleichzeitig mannigfaltige Bedingungen ber{ü}cksichtigt werden. Die verf{ü}gbaren technischen und organisatorischen Alternativm{ö}glichkeiten sind normalerweise so vielf{ä}ltig und komplex, dass eine manuelle Planung praktisch nicht m{ö}glich ist. In diesem Artikel wird das Potential und die Methodik der mathematischen Optimierung bei der kostenoptimalen Planung von Kommunikationsnetzen vorgestellt. Als Ausgangspunkt wird exemplarisch eine typische praktische Aufgabe, die Struktur- und Konfigurationsplanung mehrstufiger Telekommunikationsnetzwerke, dargestellt. Anschließend werden kurz die wesentlichen Modellierungstechniken und Verfahrensans{ä}tze der mathematischen Optimierung skizziert. Abschließend gehen wir auf die Planung einer ad{ä}quaten Informations- und Kommunikations- Infrastruktur f{ü}r ein dezentrales Energieversorgungsnetz ein.
    Keywords: ddc:000
    Language: German
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  • 22
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    Chromatic Scheduling Polytopes coming from the Bandwidth Allocation Problem in Point-to-Multipoint Radio AccessSystems (2003)
    Details
    Publication Date: 2020-08-05
    Description: Point-to-Multipoint systems are one kind of radio systems supplying wireless access to voice/data communication networks. Such systems have to be run using a certain frequency spectrum, which typically causes capacity problems. Hence it is, on the one hand, necessary to reuse frequencies but, on the other hand, no interference must be caused thereby. This leads to the bandwidth allocation problem, a special case of so-called chromatic scheduling problems. Both problems are NP-hard, and there exist no polynomial time approximation algorithms with a guaranteed quality. One kind of algorithms which turned out to be successful for many other combinatorial optimization problems uses cutting plane methods. In order to apply such methods, knowledge on the associated polytopes is required. The present paper contributes to this issue, exploring basic properties of chromatic scheduling polytopes and several classes of facet-defining inequalities.
    Keywords: ddc:000
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  • 23
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    Optimization Methods for UMTS Radio Network Planning (2003)
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    Publication Date: 2020-02-11
    Description: The UMTS radio network planning problem poses the challenge of designing a cost-effective network that provides users with sufficient coverage and capacity. We describe an optimization model for this problem that is based on comprehensive planning data of the EU project MOMENTUM. We present heuristic mathematical methods for this realistic model, including computational results.
    Keywords: ddc:000
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  • 24
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    Assessing Capacity Improvements by Relaying in Cellular Networks (2003)
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    Publication Date: 2014-02-26
    Description: Relaying -- allowing multiple wireless hops -- is a protocol extension for cellular networks conceived to improve data throughput. Its benefits have only been quantified for small example networks. For assessing its general potential, we define a complex resource allocation\slash{}scheduling problem. Several mathematical models are presented for this problem; while a time-expanded MIP approach turns out intractable, a sophisticated column generation scheme leads to good computational results. We thereby show that for selected cases relaying can increase data throughput by 30\% on the average.
    Keywords: ddc:000
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  • 25
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    Minimum Converter Wavelength Assignment in All-Optical Networks (2003)
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    Publication Date: 2014-02-26
    Description: Finding conflict-free wavelength assignments with a minimum number of required conversions for a routing of the lightpaths is one of the important tasks within the design of all-optical networks. We consider this problem in multi-fiber networks with different types of WDM systems. We give a detailed description of the problem and derive its theoretical complexity. For practical application, we propose several sequential algorithms to compute appropriate wavelength assignments. We also perform computational experiments to evaluate their performance. For the iterative algorithms, we identify characteristic patterns of progression. Two of these algorithms qualify for application in practice.
    Keywords: ddc:000
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  • 26
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    Rigid body docking for Virtual Screening (2003)
    Details
    Publication Date: 2014-09-30
    Description: A recently developed algorithm allows Rigid Body Docking of ligands to proteins, regardless of the accessibility and location of the binding site. The Docking procedure is divided into three subsequent optimization phases, two of which utilize rigid body dynamics. The last one is applied with the ligand already positioned inside the binding pocket and accounts for full flexibility. Initially, a combination of geometrical and force-field based methods is used as a Coarse Docking strategy, considering only Lennard-Jones interactions between the target and pharmaceutically relevant atoms or functional groups. The protein is subjected to a Hot Spot Analysis, which reveals points of high affinity in the protein environment towards these groups. The hot spots are distributed into different subsets according to their group affiliation. The ligand is described as a complementary point set, consisting of the same subsets. Both sets are matched in $\mathrm{I\!R}^{3}$, by superimposing members of the same subsets. In the first instance, steric inhibition is nearly neglected, preventing the system's trajectory from trapping in local minima and thus from finding false positive solutions. Hence the exact location of the binding site can be determined fast and reliably without any additional information. Subsequently, errors resulting from approximations are minimized via finetuning, this time considering both Lennard-Jones and Coulomb forces. Finally, the potential energy of the whole complex is minimized. In a first evaluation, results are rated by a reduced scoring function considering only noncovalent interaction energies. Exemplary Screening results will be given for specific ligands.
    Keywords: ddc:000
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    Integrated Optimization of Hardware Configuration and Capacity. Dimensioning in SDH and opaque WDM networks (2003)
    Details
    Publication Date: 2014-02-26
    Description: We suggest a new model for the design of telecommunication networks which integrates decisions about the topology, configuration of the switching hardware, link dimensioning, and protected routing of communication demands. Applying the branch-and-cut-algorithm implemented in our network planning and optimization tool DISCNET, we demonstrate that real-world based network planning instances of such an enhanced model can be solved.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Verteilter Dokumenten-Speicher, Erfahrungen mit den Kluwer-Daten des Friedrich-Althoff-Konsortiums (2003)
    Details
    Publication Date: 2020-02-11
    Description: Dieser Bericht beschreibt die Erfahrungen und Schlussfolgerungen,die im Rahmen der VDS-Vorstudie bei der Speicherung der vom Friedrich-Althoff-Konsortium lizenzierten Zeitschriften des Kluwer-Verlages gewonnen wurden.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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    Endnutzerbasierte Online-Fernleihe im KOBV - Kurzbeschreibung (2003)
    Details
    Publication Date: 2020-11-13
    Description: Der KOBV setzt für die endnutzerbasierte Online-Fernleihe den Sisis ZFL-Server (Zentraler Fernleih-Server) ein. Mit dem Einsatz des ZFL-Servers können in den Bibliotheken echte Rationalisierungseffekte erzielt werden: Der Server ist in der Lage, Fernleih-Bestellungen an lokale Systeme zu übergeben, so dass sie im lokalen System automatisch - ohne Eingreifen von Bibliotheksmitarbeitern - weiterverarbeitet werden können. Im KOBV können derzeit Sisis- und Aleph-Lokalsysteme diese Schnittstelle voll bedienen. Andere Bibliothekssysteme im KOBV, die diese Schnittstelle nicht bedienen können, werden mittels eines E-Mail-Verfahrens in die Online-Fernleihe integriert. Die vorliegende Kurzbeschreibung der Online-Fernleihe im KOBV soll - im Gegensatz zur Spezifikation, die möglichst vollständig sein sollte - einen leicht verständlichen Einblick in die Abläufe der Online-Fernleihe vermitteln. Nach einem Überblick über zu erwartende Rationalisierungseffekte ist der Ablauf einer Online-Fernleih-Bestellung - veranschaulicht durch eine Graphik mit dem technischen Aufbau im KOBV - kurz dargestellt. \vspace{6mm} {\it Hinweis:} Die von einer Arbeitsgruppe des KOBV erstellte Spezifikation zur Online-Fernleihe ist als ZIB Report 02-30 auf dem Preprint-Server des ZIB veröffentlicht. Siehe: Monika Kuberek (Red.) {\begin{rawhtml} 〈a href="http://www.zib.de/Publications/Reports/ZR-02-30.pdf"〉 〈i〉 Spezifikation für eine Verbund-Fernleih-Software im KOBV〈/i〉 〈/a〉 \end{rawhtml}}
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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    Improved Perron Cluster Analysis (2003)
    Details
    Publication Date: 2014-02-26
    Description: The problem of clustering data can often be transformed into the problem of finding a hidden block diagonal structure in a stochastic matrix. Deuflhard et al. have proposed an algorithm that state s the number $k$ of clusters and uses the sign structure of $k$ eigenvectors of the stochastic matrix to solve the cluster problem. Recently Weber and Galliat discovered that this system of eigenvectors can easily be transformed into a system of $k$ membership functions or soft characteristic functions describing the clusters. In this article we explain the corresponding cluster algorithm and point out the underlying theory. By means of numerical examples we explain how the grade of membership can be interpreted.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Zur Zugriffskontrolle im KOBV (2003)
    Details
    Publication Date: 2014-02-26
    Description: Mit der Entwicklung des KOBV-Informationsportals soll den Benutzern in der Region Berlin-Brandenburg ein verbesserter Zugang zu Informationsressourcen geboten werden. Einen wesentlichen Anteil diese Auf der Grundlage der Analyse der Rahmenbedingungen werden Anforderungen an die Zugriffskontrolle im KOBV definiert und Lösungsmöglichkeiten auf der Ebene allgemeiner Modelle diskutiert.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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    Navigation in the KOBV-Informationsportal Conceptual View (2003)
    Details
    Publication Date: 2014-02-26
    Description: The KOBV Informationsportal aims to be a universal gateway to the sources of information hosted by the partner libraries from the Berlin-Brandenburg area. Due to the large number of these sources, an intuitive navigation is an essential component of the portal. The navigation-component should preserve the partner libraries? independence and overcome their administrative and technical differences. This paper proposes a collection-level navigation with four dimensions: the sources? subject areas (e.g. the first two levels of DDC), the sources? type (e.g. e-journals, databases, OPACs, etc.), the sources? location (e.g. Berlin, Brandenburg) / the library that hosts that source and the sources? accessing state (e.g. free, restricted, etc.).
    Keywords: ddc:000
    Language: English
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    Polynomial Inequalities Representing Polyhedra (2003)
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    Publication Date: 2014-02-26
    Description: Our main result is that every n-dimensional polytope can be described by at most (2n-1) polynomial inequalities and, moreover, these polynomials can explicitly be constructed. For an n-dimensional pointed polyhedral cone we prove the bound 2n-2 and for arbitrary polyhedra we get a constructible representation by 2n polynomial inequalities.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    The final NETLIB-LP results (2003)
    Details
    Publication Date: 2020-02-11
    Description: The NETLIB has now served for 18 years as a repository of LP problem instances. From the beginning to the present day there was some uncertainness about the precise values of the optimal solutions. We implemented a program using exact rational arithmetic to compute proofs for the feasibility and optimality of an LP solution. This paper reports the \emph{exact} optimal objective values for all NETLIB problems.
    Keywords: ddc:000
    Language: English
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    Dust formation in brown dwarf atmospheres under conditions of driven turbulence (2003)
    Details
    Publication Date: 2014-02-26
    Description: Based on the knowledge gained from direct numerical simulations which are only possible in the microscale regime, a concept of driven turbulence is presented which allows to enter the mesoscopic scale regime. Here, dust formation under stochastic hydro- and thermodynamic conditions is studied: constructively superimposed stochastic waves initiate dust formation by the creation of singular nucleation events. It, hence, results a varying mean grain size and dust density in space and time. The newly formed dust changes the thermodynamic behavior from almost isotherm to adiabatic and chemically depletes the gas phase.
    Keywords: ddc:000
    Language: English
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    Kosten- und Qualitätsoptimierung in Kommunikationsnetzen (2003)
    Details
    Publication Date: 2014-11-11
    Description: Der scharfe Wettbewerb innerhalb der Telekommunikationsbranche zwingt die Netzbetreiber dazu, ihre Investitionen genau zu planen und immer wieder Einsparungsmanahmen durchzuführen. Gleichzeitig ist es jedoch wichtig, die Qualität der angebotenen Dienste zu verbessern, um neue Kunden zu gewinnen und langfristig an sich zu binden. Die mathematische Optimierung bietet sich für viele solcher Aufgabenstellungen als hervorragend geeignetes Planungswerkzeug an. Ziel dieses Artikels ist es, ihre Methodik und ihre Anwendung speziell zur Kosten- und Qualitätsoptimierung in Kommunikationsnetzen vorzustellen. Anhand von vier konkreten Planungsaufgaben aus dem Bereich der Festnetzplanung wird aufgezeigt, wie sich komplexe Zusammenhänge in flexiblen mathematischen Modellen abbilden lassen und welche Verfahren zur automatisierten Bearbeitung der Probleme eingesetzt werden können. Die hier vorgestellten Methoden zeichnen sich insbesondere dadurch aus, dass sie neben hochwertigen Lösungen auch eine Qualittsgarantie liefern, mit der sich die Lsungen fundiert bewerten lassen. Die dokumentierten Ergebnisse aus verschiedenen Industrieprojekten belegen die Eignung und Güte der mathematischen Optimierung für die Praxis.
    Keywords: ddc:000
    Language: German
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    Dust in Brown Dwarfs IV. Dust formation and driven turbulence on mesoscopic scales (2003)
    Details
    Publication Date: 2014-02-26
    Description: Dust formation {in brown dwarf atmospheres} is studied by utilizing a model for driven turbulence in the mesoscopic scale regime. We apply a pseudo-spectral method where waves are created and superimposed {within} a {limited} wavenumber interval. The turbulent kinetic energy distribution follows the Kolmogoroff spectrum which is assumed to be the most likely value. Such superimposed, stochastic waves may occur in a convectively active environment. They cause nucleation fronts and nucleation events and thereby initiate the dust formation process which { continues until} all condensible material is consumed. Small disturbances {are found to} have a large impact on the dust forming system. An initially dust-hostile region, which may originally be optically thin, becomes optically thick in a patchy way showing considerable variations in the dust properties during the formation process. The dust appears in lanes and curls as a result of the interaction with waves, i.e. turbulence, which form larger and larger structures with time. Aiming on a physical understanding of the variability of brown dwarfs, related to structure formation in substellar atmospheres, we work out first necessary criteria for small-scale closure models to be applied in macroscopic simulations of dust forming astrophysical systems.
    Keywords: ddc:000
    Language: English
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    The multi-scale dust formation in substellar atmospheres (2003)
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    Publication Date: 2014-02-26
    Description: Substellar atmospheres are observed to be irregularly variable for which the formation of dust clouds is the most promising candidate explanation. The atmospheric gas is convectively unstable and, last but not least, colliding convective cells are seen as cause for a turbulent fluid field. Since dust formation depends on the local properties of the fluid, turbulence influences the dust formation process and may even allow the dust formation in an initially dust-hostile gas. A regime-wise investigation of dust forming substellar atmospheric situations reveals that the largest scales are determined by the interplay between gravitational settling and convective replenishment which results in a dust-stratified atmosphere. The regime of small scales is determined by the interaction of turbulent fluctuations. Resulting lane-like and curled dust distributions combine to larger and larger structures. We compile necessary criteria for a subgrid model in the frame of large scale simulations as result of our study on small scale turbulence in dust forming gases.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    HelmPole - A finite element solver for scattering problems on unbounded domains: Implementation based on PML (2003)
    Details
    Publication Date: 2019-01-24
    Description: The solution of scattering problems described by the Helmholtz equation on unbounded domains is of importance for a wide variety of applications, for example in electromagnetics and acoustics. An implementation of a solver for scattering problems based on the programming language Matlab is introduced. The solver relies on the finite-element-method and on the perfectly-matched-layer-method, which allows for the simulation of scattering problems on complex geometries surrounded by inhomogeneous exterior domains. This report gives a number of detailed examples and can be understood as a user manual to the freely accessible code of the solver HelmPole.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Progressive Retrieval and Hierarchical Visualization of Large Remote Data (2003)
    Details
    Publication Date: 2020-03-09
    Description: \noindent The size of data sets produced on remote supercomputer facilities frequently exceeds the processing capabilities of local visualization workstations. This phenomenon increasingly limits scientists when analyzing results of large-scale scientific simulations. That problem gets even more prominent in scientific collaborations, spanning large virtual organizations, working on common shared sets of data distributed in Grid environments. In the visualization community, this problem is addressed by distributing the visualization pipeline. In particular, early stages of the pipeline are executed on resources closer to the initial (remote) locations of the data sets. \noindent This paper presents an efficient technique for placing the first two stages of the visualization pipeline (data access and data filter) onto remote resources. This is realized by exploiting the ``extended retrieve'' feature of GridFTP for flexible, high performance access to very large HDF5 files. We reduce the number of network transactions for filtering operations by utilizing a server side data processing plugin, and hence reduce latency overhead compared to GridFTP partial file access. The paper further describes the application of hierarchical rendering techniques on remote uniform data sets, which make use of the remote data filtering stage.
    Keywords: ddc:000
    Language: English
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    The Potential of Relaying in Cellular Networks (2003)
    Details
    Publication Date: 2014-02-26
    Description: Relaying is a protocol extension for cellular wireless computer networks; in order to utilize radio resources more efficiently, several hops are allowed within one cell. This paper investigates the principle potential of relaying by casting transmission scheduling as a mathematical optimization problem, namely, a linear program. We analyze the throughput gains showing that, irrespective of the concrete scheduling algorithm, performance gains of up to 30\% on average for concrete example networks are achievable.
    Keywords: ddc:000
    Language: English
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    Critical and Anticritical Edges with respect to Perfectness (2003)
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    Publication Date: 2014-02-26
    Description: We call an edge $e$ of a perfect graph $G$ critical if $G-e$ is imperfect and call $e$ anticritical if $G+e$ is imperfect. The present paper surveys several questions in this context. We ask in which perfect graphs critical and anticritical edges occur and how to detect such edges. The main result by [{\sl Wagler, PhD thesis 2000}] shows that a graph does not admit any critical edge if and only if it is Meyniel. The goal is to order the edges resp.~non-edges of certain perfect graphs s.t. deleting resp.~adding all edges in this order yields a sequence of perfect graphs only. Results of [{\sl Hayward 1985}] and [{\sl Spinrad & Sritharan 1995}] show the existence of such edge orders for weakly triangulated graphs; the line-perfect graphs are precisely these graphs where all edge orders are perfect [{\sl Wagler 2001}]. Such edge orders cannot exist for every subclass of perfect graphs that contains critically resp.~anticritically perfect graphs where deleting resp.~adding an arbitrary edge yields an imperfect graph. We present several examples and properties of such graphs, discuss constructions and characterizations from [{\sl Wagler 1999, Wagler PhD thesis 2000}]. An application of the concept of critically and anticritically perfect graphs is a result due to [{\sl Hougardy & Wagler 2002}] showing that perfectness is an elusive graph property.
    Keywords: ddc:000
    Language: English
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    Accelerating Hasenbusch's Acceleration of Hybrid Monte Carlo (2003)
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    Publication Date: 2014-02-26
    Description: Hasenbusch has proposed splitting the pseudo-fermionic action into two parts, in order to speed-up Hybrid Monte Carlo simulations of QCD. We have tested a different splitting, also using clover-improved Wilson fermions. An additional speed-up between 5 and 20\% over the original proposal was achieved in production runs.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Safe separators for treewidth (2003)
    Details
    Publication Date: 2014-11-10
    Description: A set of vertices $S\subseteq V$ is called a safe separator for treewidth, if $S$ is a separator of $G$, and the treewidth of $G$ equals the maximum of the treewidth over all connected components $W$ of $G-S$ of the graph, obtained by making $S$ a clique in the subgraph of $G$, induced by $W\cup S$. We show that such safe separators are a very powerful tool for preprocessing graphs when we want to compute their treewidth. We give several sufficient conditions for separators to be safe, allowing such separators, if existing, to be found in polynomial time. In particular, every minimal separator of size one or two is safe, every minimal separator of size three that does not split off a component with only one vertex is safe, and every minimal separator that is an almost clique is safe; an almost clique is a set of vertices $W$ such that there is a $v\in W$ with $W-\{v\}$ a clique. We report on experiments that show significant reductions of instance sizes for graphs from proba! bilistic networks and frequency assignment.
    Keywords: ddc:000
    Language: English
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    Interior Point Methods in Function Space (2003)
    Details
    Publication Date: 2019-01-29
    Description: A primal-dual interior point method for optimal control problems is considered. The algorithm is directly applied to the infinite dimensional problem. Existence and convergence of the central path are analyzed, and linear convergence of a short step pathfollowing method is established.
    Keywords: ddc:000
    Language: English
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    Triangulated Manifolds with Few Vertices: Geometric 3-Manifolds (2003)
    Details
    Publication Date: 2014-02-26
    Description: We explicitly construct small triangulations for a number of well-known $3$-dimensional manifolds and give a brief outline of some aspects of the underlying theory of $3$-manifolds and its historical development.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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    Lastbalancierung in Peer-to-Peer Systemen (2003)
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    Publication Date: 2016-06-30
    Description: Peer-to-Peer (P2P) Systeme werden u.a. zur Verwaltung von großen Datenmengen benutzt, die auf verschiedene Rechner verteilt sind. Benutzern soll damit der Zugriff auf Daten innerhalb des Systems leicht ermöglicht werden. Damit in P2P Systemen die Daten effizient verteilt und gesucht werden können, existieren Distributed Hash Tables. Distributed Hash Tables (DHT) sind eine Methode, um globale Informationen persistent speichern zu können. Der Wertebereich der Hashfunktion, welche die zu veröffentlichenden Einträge auf Werte abbildet, wird in Abschnitte aufgeteilt, die einzelnen Knoten zugeteilt werden. Die meisten DHTs haben aber ein Problem bei der Verteilung der Last. Die verschiedenen DHT Systeme beruhen meist auf einem identischen Ansatz der Lastverteilung. Die Last wird nur mit Hilfe einer Hashfunktion verteilt. Es wird davon ausgegangen, dass diese Funktion die Last gleichmäßig verteilt. Im Rahmen dieser Arbeit wurde ein Verfahren zur Last Verteilung entwickelt, simuliert und implementiert. Bei dem Verfahren wird die Last wie bei der Verteilung von Wärme an die Umgebung abgegeben. Es wird mit existierenden Lastbalancierungsalgorithmen verglichen. Mit diesem neuen Verfahren ist es möglich, Last in DHTs besser zu verteilen ohne große Änderungen an den DHTs vorzunehmen. Es wird gezeigt, wie mit dem Verfahren zusätzlich die Fehlertoleranz des P2P Systems erhöht werden kann.
    Description: One of the many uses of Peer-to-Peer (P2P) systems is the administration of large data sets that are distributed across different computers, with the goal of facilitating user access to files within the system. Distributed Hash Tables (DHT) are designed to enable the efficient distribution and search of files, by allowing global information to be persistently stored. The range of values of the hash function (the possible entries in the published hash table) are assigned to individual nodes. Most DHTs, however, have a problem with load distribution. The various DHT systems usually operate by distributing load equally among nodes. Thus the load is distributed using the help of the hash function. One assumes this function distributes the load evenly. In the context of this work a method of distributing load has been developed, simulated and implemented. With this method load is transferred in a fashion analogous to the dissipation of heat into the environment. Comparisons with existing algorithms for load balancing are drawn. With the new procedure it is possible to better distribute load in DHTs without requiring major changes to the DHTs themselves. It is shown that with the procedure the fault tolerance of P2P systems may also be increased.
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
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    Robust Perron Cluster Analysis in Conformation Dynamics (2003)
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    Publication Date: 2014-02-26
    Description: The key to molecular conformation dynamics is the direct identification of metastable conformations, which are almost invariant sets of molecular dynamical systems. Once some reversible Markov operator has been discretized, a generalized symmetric stochastic matrix arises. This matrix can be treated by Perron cluster analysis, a rather recent method involving a Perron cluster eigenproblem. The paper presents an improved Perron cluster analysis algorithm, which is more robust than earlier suggestions. Numerical examples are included.
    Keywords: ddc:000
    Language: English
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    Demand-wise Shared Protection for Meshed Optical Networks (2003)
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    Publication Date: 2014-11-11
    Description: In this paper, a new shared protection mechanism for meshed optical networks is presented. Significant network design cost reductions can be achieved in comparison to the well-known 1+1 protection scheme. Demand-wise Shared Protection (DSP) bases on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of prorection. Computational experiments approve the benefits of the concept DSP for cost efficient optical network designs.
    Keywords: ddc:000
    Language: English
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    Simulation of the Human Mandible: Comparison of Bone Mineral Density and Stress/Strain Profiles due to Masticatory Muscles' Traction (2003)
    Details
    Publication Date: 2019-05-10
    Description: The correlation of the inner architecture of bone and its functional loading was already stated by Wolff in 1892. Our objective is to demonstrate this interdependence in the case of the human mandible. For this purpose, stress/strain profiles occuring at a human lateral bite were simulated. Additionally, by a combination of computer graphics modules, a three--dimensional volumetric visualization of bone mineral density could be given. Qualitative correspondences between the density profile of the jaw and the simulated stress/strain profiles could be pointed out. In the long run, this might enable the use of the simulation for diagnosis and prognosis. The solution of the underlying partial differential equations describing linear elastic material behaviour was provided by an adaptive finite element method. Estimates of the discretization errors, local grid refinement, and multilevel techniques guaranteed the reliability and efficiency of the method.
    Keywords: ddc:000
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    MoDySim - A parallel dynamical UMTS simulator (2003)
    Details
    Publication Date: 2014-02-26
    Description: UMTS is a 3rd generation mobile telecommunication system which enables multi-service and multi-bit rate communication going beyond the possibilities of previous systems. The simulator MoDySim models UMTS in great detail. Characteristics of UMTS such as soft hand-over and the interdependency of load and capacity among neighbouring cells are challenges for the parallelisation of such a system. In this paper we explain how the software was parallelised and present performance results of a UMTS simulation for the city of Berlin.
    Keywords: ddc:000
    Language: English
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  • 52
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    A numerical reinvestigation of the Aoki phase with $N_f=2$ Wilson fermions at zero temperature (2003)
    Details
    Publication Date: 2014-02-26
    Description: We report on a numerical reinvestigation of the Aoki phase in lattice QCD with two flavors of Wilson fermions where the parity-flavor symmetry is spontaneously broken. For this purpose the Hybrid Monte Carlo algorithm was used and an explicit symmetry-breaking source term $h\bar{\psi} i \gamma_{5} \tau^{3}\psi$ was added to the Wilson fermion action. The order parameter $\langle\bar{\psi}i\gamma_{5}\tau^{3}\psi\rangle$ was studied at several values of $(\beta,\kappa,h)$ on lattices of sizes $4^4$ to $12^4$. Our largest lattices can be considered as infintely large allowing to extrapolate to $h=0$. The existence of a parity-flavor-breaking phase can be confirmed at $\beta=4.0$ and $\beta=4.3$ while we find no sign of parity-flavor-breaking at $\beta=4.6$ and $\beta=5.0$.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 53
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    Clustering by using a simplex structure (2003)
    Details
    Publication Date: 2014-02-26
    Description: In this paper we interpret clustering as a mapping of data into a simplex. If the data itself has simplicial struture this mapping becomes linear. Spectral analysis is an often used tool for clustering data. We will show that corresponding singular vectors or eigenvectors comprise simplicial structure. Therefore they lead to a cluster algorithm, which consists of a simple linear mapping. An example for this kind of algorithms is the Perron cluster analysis (PCCA). We have applied it in practice to identify metastable sets of molecular dynamical systems. In contrast to other algorithms, this kind of approach provides an a priori criterion to determine the number of clusters. In this paper we extend the ideas to more general problems like clustering of bipartite graphs.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 54
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    Ein neues Verfahren zur Lösung des Streuproblems der Maxwell-Gleichungen (2003)
    Details
    Publication Date: 2016-06-09
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
    Format: application/pdf
    Format: application/postscript
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    Jahresbericht 2002 (2003)
    Details
    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
    Format: application/pdf
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  • 56
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    Semantic Annotation in Mathematics and Math-Net (2003)
    Details
    Publication Date: 2022-04-11
    Description: The Web of the future will provide a huge amount of information. We need better ways for dealing with and managing the information. A qualified semantic annotation of the information plays a key role for the Web of the future. This article gives an overview about the efforts of the mathematical community to build up a distributed and open information and communication system for mathematics: the Math-Net. The Math-Net Initiative has developed metadata schemas for some classes of Web resources which are relevant in mathematics. Math-Net Services process this information and enable the user to efficiently search and access the information.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 57
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    A new Finite Element realization of the Perfectly Matched Layer Method for Helmholtz scattering problems on polygonal domains in 2D (2003)
    Details
    Publication Date: 2022-07-07
    Description: In this paper we propose a new finite element realization of the Perfectly Matched Layer method (PML-method). Our approach allows to deal with arbitrary shaped polygonal domains and with certain types of inhomogeneous exterior domains. Among the covered inhomogeneities are open waveguide structures playing an essential role in integrated optics. We give a detailed insight to implementation aspects. Numerical examples show exponential convergence behavior to the exact solution with the thickness of the PML sponge layer.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 58
    Electronic Resource
    Electronic Resource
    Heat transfer to non-newtonian fluids (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 92-100 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the first theoretical analyses combined with an experimental study of the variables controlling heat transfer rates to non-Newtonian fluids in the streamline-flow region. The theoretical analyses, for the limiting types of non-Newtonian materials, were related to the intermediate case of Newtonian behavior to form a coherent theory applicable to Newtonian and non-Newtonian fluids alike.The experimental data covered Graetz numbers between 100 and 2,000 and were correlated with a mean deviation of 13.5%. The flow-behavior indexes of the three non-Newtonian fluids used varied form 0.18 to 0.70.Some preliminary non-Newtonian results are presented on the problems of nonisothermal fluid-flow pressure losses and heat transfer outside the laminar-flow region. Further theoretical work is recommended in both these areas. Additional experimental data would be of value in all of the problems discussed.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030116
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  • 59
    Electronic Resource
    Electronic Resource
    Heat-conduction losses in reactor waste basins (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 143 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030123
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  • 60
    Electronic Resource
    Electronic Resource
    Dispersed-phase holdup (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 144 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030125
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  • 61
    Electronic Resource
    Electronic Resource
    Unit operations of chemical engineering. Warren L. McCabe and Julian C. Smith. McGraw-Hill Book Company, Inc., New Yark (1956). 945 pages. $10.50 (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 9M 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030126
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  • 62
    Electronic Resource
    Electronic Resource
    Computing machines and the patterns of research (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 145-145 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030202
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  • 63
    Electronic Resource
    Electronic Resource
    Performance of packed columns. IV. Effect of gas properties, temperature, and pressure on gasphase mass transfer coefficients (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 157-161 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To test the applicability, over a wide range of temperatures, pressures, and gas physical properties, of the mass transfer correlation presented earlier, 0.5-in. naphthalene Berl saddles were vaporized into air, carbon dioxide, and Freon-12 in a 4.0-in. column. Temperatures from 15° to 73°C. and pressures from 0.26 to 1 atm. were covered.The correlation was found to represent all the experimental data when the surface temperature of the naphthalene was used to evaluate the correct driving force.This correlation, when combined with effective interfacial areas presented previously, makes it possible to estimate the volumetric mass transfer coefficeint, kGa, for any gas-liquid-solute system.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030205
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  • 64
    Electronic Resource
    Electronic Resource
    A study of laminar-flow heat transfer in tubes (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 172-175 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The general problem of heat transfer to fluids in laminar flow in tubes is discussed, a new procedure for the measurement of local laminar-flow heat transfer coefficients is described, and an empirical equation is presented for the correlation of data for local heat transfer rates to liquids flowing upward in laminar flow in vertical tubes under conditions of constant heat flux at the tube wall.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030208
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  • 65
    Electronic Resource
    Electronic Resource
    Ion exclusion equilibria in the system glycerol-sodium chloride-water-Dowex-50 (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 183-186 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ion exclusion is an operation in which an ion exchange resin is used to separate an electrolyte from a nonelectrolyte in a polar solvent. An ion exchange resin tends to absorb a nonelectrolyte and to exclude an electrolyte. This is described quantitatively by the equilibrium distribution of the electrolyte, the nonelectrolyte, and the solvent between the resin phase and the liquid phase surrounding the resin.As no ternary distribution data applicable to ion exclusion are available, and only a few binary data have been published, a principal purpose of this investigation was to determine the distribution data for a typical system: glycerol-sodium chloride-water-Dowex-50.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030211
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  • 66
    Electronic Resource
    Electronic Resource
    Diffusion in three-component gas mixtures (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 198-207 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A solution to the Stefan-Maxwell diffusion equations for equimolal countercurrent diffusion in a three-component gas mixture is obtained which is similar in form to Gilliland's equation for diffusion of two gases through a third inert gas. The important features of both types of diffusion are investigated and the conditions under which the following phenomena occur are determined: (1) diffusion barrier (the rate of diffusion of a component is zero even though its concentration gradient is not zero); (2) osmotic diffusion (the rate of diffusion of a component is not zero even though its concentration gradient is zero); (3) reverse diffusion (a component diffuses against the gradient of its concentration).A generalized driving force which describes these phenomena is introduced, and approximate equations are developed which give the individual rates of diffusion directly.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030214
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  • 67
    Electronic Resource
    Electronic Resource
    Control of continuous-flow chemical reactors. II. Frequency-response relations for reactor chains, tubular reactors, and unit reactor control loops (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 256-261 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030222
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  • 68
    Electronic Resource
    Electronic Resource
    Some remarks on longitudinal mixing or diffusion in fixed beds (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 280-282 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been shown both theoretically and experimentally that the radial Peclet number in a packed bed approaches about 11. If it is assumed that the interstitial volume of the bed forms mixing cells, then a comparison of the solutions obtained from the mixing and turbulent diffusive mechanisms shows that the axial Peclet number for agreement of the two must be about 2, as a limiting case for high Reynolds numbers. This is substantiated by experiment.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030226
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  • 69
    Electronic Resource
    Electronic Resource
    A rate equation for molecular diffusion in a dispersed phase (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 8J 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030231
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  • 70
    Electronic Resource
    Electronic Resource
    Approximate operational calculus in chemical engineering (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 289-293 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Approximations are suggested to extend the usefulness of operational calculus in solving boundary-value problems of interest to the chemical engineer. General approximations are outlined and specific ones illustrated. The use of computing machines with operational calculus is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030229
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  • 71
    Electronic Resource
    Electronic Resource
    Fluidization and sedimentation of spherical particles (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 293-296 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Data are presented in support of an expression describing the relation between the sedimenting velocity or the fluidizing velocity and the fraction voids. This expression which contains no empirical constants may be obtained by considering a particle in a fluid having the average properties of the suspension. Stokes's law is used to calculate the force on the particle, and an equation derived by Vand is used to describe the viscosity of the suspension. The equation based on this model is valid for particle Reynolds numbers less than 0.07. The model may be used as an approximation of bed behavior at higher Reynolds numbers by application of a correction to Stokes's law.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030230
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  • 72
    Electronic Resource
    Electronic Resource
    Errata (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 7S 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030326
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  • 73
    Electronic Resource
    Electronic Resource
    Masthead (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030401
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  • 74
    Electronic Resource
    Electronic Resource
    Prediction of cake-washing results with continuous filtration equipment (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 433-438 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper proposes a theory of filter-cake washing on continous filtration equipment based upon the assumption that mixing of the strong liquor and wash fluid is controlling. The theory can be conventiently applied to experimental filtration leaf tests for determining wash efficiency and is easily extrapolated to full-scale results with the normally experienced uneven cake thickness and wash-fluid distribution taken into account.To obtain the necessary wash-fluid volume for proper soluble removal, a correlation method of wash time as a function of wash ratio with parameters of cake-formation time has been derived from commonly accepted filtration theory. Experimental and plant data indicate a close agreement with the theory, and the method can be employed to predict filtration rate as a function of wash ratio. A typical illustration has been given to determine filtration requirements for recovering soluble uranium after leaching of the ore by continuous filtration. Washing rate was proved to be conrolling, and this design based only on cake-formation rate would yield insufficient wash ratios and excessive soluble uranium loss. Final filter and flow-sheet design must be based on uranium recovery which can be predicted by the proposed methods.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030403
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  • 75
    Electronic Resource
    Electronic Resource
    Masthead (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957) 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030101
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  • 76
    Electronic Resource
    Electronic Resource
    Engineering in history (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 1-1 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030102
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  • 77
    Electronic Resource
    Electronic Resource
    Mass transfer in a continuous-flow mixing vessel (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 283-286 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer coefficients have been determined for the dissolution of Na2S2O3·5H2O crystals in water under conditions of turbulent agitation in a mixing vessel. The dissolution was carried out in a steady-flow process in which the area of selt crystals and the concentration of the solution in the mixing vessel were constant during each run. A comparison is made with previously unpublished results for batch runs in a similar system, and a method is developed for calculating the surface area of salt particles suspended in the mixing vessel under steady-flow conditions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030227
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  • 78
    Electronic Resource
    Electronic Resource
    Grimm and Andersen: Move over (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 297-297 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030302
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  • 79
    Electronic Resource
    Electronic Resource
    Nusselt values for estimating turbulent liquid metal heat transfer in noncircular ducts (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 313-317 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple expression for estimating the turbulent forced-convection heat transfer performance of liquid metals flowing through noncircular ducts is presented. This equation requires the knowledge of the slug Nusselt number evaluated for the specific geometry and for the pertinent boundary conditions. Such Nusselt values are presented herein for a number of technically important geometries. One check on the heat transfer prediction given by Equation (4) is in the case of an annular duct with constant heat flow through the outer wall with the inner wall insulated, for which experimental data exist. The prediction agrees within 20% with the experimental data.Several possible boundary conditions that may exist in noncircular cross sections are throughly discussed, and it is hoped that as a result this paper may serve to clarify some of the confusion existing in the literature.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030305
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  • 80
    Electronic Resource
    Electronic Resource
    Simple theory of an idealized turbulent mixer (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 329-330 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With stationary isotropic turbulence postulated, the rate of decrease in concentration fluctuations of a scalar contaminant is estimated in terms of the turbulence scale and the power input to the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030309
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  • 81
    Electronic Resource
    Electronic Resource
    Measured plate efficiencies and values predicted from single-phase studies (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 336-342 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plate efficiencies measured on 18-in.-diam. sieve plates are reported for the acetic acid-water system and for the methyl isobutyl ketone-water system at atmospheric pressure. In the former system the major resistance to mass transfer is in the gas phase; liquid-phase resistance to mass transfer is controlling in the latter. Efficiencies are also reported for the aniline-nitrobenzene system (gas-phase resistance controlling) at 5 mm. Hg absolute on 6-in.-diam. sieve plates. Pure gas- and liquid-phase efficiencies for both plate designs were determined by the adiabatic humidification of air and the desorption of oxygen from water into air. Predicted values of plate efficiency for each of the binary systems studied were computed from the pure phase efficiencies according to the procedure outlined by Gerster et al. A comparison between measured and predicted efficiencies is presented as a guide for future research in this field.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030311
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  • 82
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    Electronic Resource
    Heat transfer coefficients for condensing organic vapors of pure components and binary mixtures (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 348-352 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The behavior of the film coefficient of heat transfer for the condensation of organic vapor mixtures was investigated experimentally to establish a satisfactory basis for applying the Nusselt equation to binary systems. Five ideal and nonideal pairs, all of which gave miscible condensates, were studied; the work was carried out under conditions of almost total condensation on a horizontal condensing surface designed to comply as rigidly as possible with the conditions for which Nusselt's equation is valid.The same behavior was observed for all systems and all concentrations studied: the experimental coefficients fell between those for the pure components and followed the behavior pattern for pure components when the temperature difference was taken as that between the bubble point of the condensate and the surface temperature, rather than between the dew point or the measured vapor temperature and the surface temperature, Correlation of the film coefficient showed it to vary approximately linearly with composition if the coefficients were compared at a constant value of the temperature difference, defined as above. This permits determination of the coefficient for a mixture by interpolation between the coefficients for the pure components, which are easily obtained, in preference to making the calculations with the properties of the mixture obtained by laborious and uncertain weighting of the corresponding properties of the pure components.When results are interpreted in the light of the theories of Colburn and Drew, the presence of a vapor-phase resistance to heat and mass transfer, as postulated by them, is indicated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030313
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  • 83
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    Electronic Resource
    Catalyzed gas-liquid reactions in trickling-bed reactors (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 366-372 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic studies were made in a differential flow reactor of the hydogenation of α-methyl-styrene with the liquid trickling over a bed of catalyst pellets countercurrent to a stream of hydrogen. The catalysts consisted of palladium, platinum, rhodium, ruthenium, and nickel supported on the external surfaces of aluminal pellets.With palladium at pressures above 3 atm. the apparent rate-controlling step was a surface reaction between dissociated hydrogen and α-methylstyrene both adsorbed on different type of active sites. Below 3 atm. pressure the reactants competed for similar active sites. With platinum the apparent rate-controlling step was a surface reaction between dissociated hydrogen and α-methylstyrene on similar active sites. Rhodium and nickel catalyzed the polymerization α-methylstyrene together with slow hydrogenation. Ruthenium had negligible activity for catalyzing the hydrogenation under the moderate conditions used in this work.In all cases mass transfer resistances were negligible.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030316
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  • 84
    Electronic Resource
    Electronic Resource
    Determination of the chemical properties of an oxide catalyst in a closed system (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 386-390 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The bulk chemical properties of an impregnated chromia-alumina catalyst with respect to several gases, CO, CO2, C3H6, were determined as a function of the degree of oxidation of the surface of the catalyst. The importance of the results lies in the demonstration that a simple method described herein can be used to obtain significant data on catalytic surfaces. Briefly, the prior adsorption of oxygen by the catalyst tended to promote the adsorption of carbon monoxide and to prohibit the adsorption of carbon dioxide. Far more carbon monoxide was adsorbed by the highly oxidized surface than could be accounted for on the basis of adsorbed carbon dioxide. The quantity of propylene adsorbed also increased with an increase in the oxidation of the surface. The results are explained on the basis of two types of adsorbed oxygen atoms.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030319
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  • 85
    Electronic Resource
    Electronic Resource
    Effects of bubbling and stirring on mass transfer coefficients in liquids (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 411-417 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the hydrogenation of α-methylstyrene by means of a suspended palladium-alumina catalyst in a stirred reactor the mass transfer of hydrogen through the liquid is the rate-controlling step and the resistance to chemical reaction at the catalyst surface is negligible except at extremely rapid rates of stirring. This system therefore provides an excellent means of establishing the effects of operating variables and mechanical construction on mass transfer coefficients in liquids in stirred reactors. It is convenient to consider the total resistance to mass transfer as consisting of two separate resistaces: in the liquid adjoining the bubbles and in the liquid adjoining the suspended solid particles; thus R = Rb + Rs.A general equation was evaluated from experimental data based upon unit volume of liquid.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030323
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  • 86
    Electronic Resource
    Electronic Resource
    Critical constants of the aromatic hydrocarbons (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 428 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Following an approach similar to that presented for the aliphatic (6, 7) and naphthenic (8) hydrocarbons, methyl-group contributions have been developed that now make possible the calculation of van der Waals' constants for aromatic hydrocarbons of considerable size and complexity. These constants are then utilized to calculate the critical temperatures, pressures, and volumes for these aromatic hydrocarbons.In addition, simple relationships have been developed that permit the evaluation of both van der Waals' constants for the unsubstituted linearly fused aromatic hydrocarbons.Comparisons of calculated critical constants with values presented in the literature for over twenty aromatic hydrocarbons produced average absolute deviations of 0.70% for the critical temperature and 2.14% for the critical pressure.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030325
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  • 87
    Electronic Resource
    Electronic Resource
    Chemical engineering kinetics. J. M. Smith. McGraw-Hill Book Cpmpany, Inc., New York (1956). 402 pages. $8.00. (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 12S 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030328
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  • 88
    Electronic Resource
    Electronic Resource
    Viscous flow in multiparticle systems: Motion of spheres and a fluid in a cylindrical tube (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 506-513 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An approximate theory for the behavior of multiparticle systems suspended in a viscous fluid is developed, based on a rigorous treatment for the case of a single sphere occupying any position in a cylindrical tube. The results obtained include estimates of the effect of some of the parameters involved on the particle velocities and spatial distribution of particles in very dilute sedimenting and fluidized beds as well as on the pressure drop resulting from passage of fluid. The conclusions presented are in agreement with such experimental data as are available and suggest a basis for more exact treatment of these systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030415
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  • 89
    Electronic Resource
    Electronic Resource
    Diffusion coefficients in hydrocarbon systems: Methane in the liquid phase of the methane-n-heptane system (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 449-453 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production and refining of petroleum involve many processes in which conditions deviate markedly from equilibrium. For prediction of the behavior of such nonequilibrium systems, information concerning the molecular-transport characteristics of the paraffin hydrocarbons is of practical interest.Fick diffusion coefficients for methane were measured in the liquid phase of the methane-n-heptane system at temperatures between 40° and 340°F. at pressures up to 3,500 lb./sq. in., but the pressure range was limited at the higher temperatures by approach to the critical state of this binary system.The measurements obtained confirmed the fact that the Fick diffusion coefficients for methane decrease with an increase in the concentration of this component and increase rapidly with an increase in temperature for a constant composition. These data together with similar information for other binary paraffin hydrocarbon systems indicate that the Fick diffusion coefficients for methane decrease with an increase in the molecular weight of the less volatile component.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030406
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  • 90
    Electronic Resource
    Electronic Resource
    Thermal-conductivity-reduced-state correlation for the inert gases (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 454-461 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fragmentary thermal-conductivity data for argon available in the literature have been correlated by use of a residual thermal conductivity k - k* vs. density ρ relationship. This correlation produced a unique continuous curve which was found to be singularly independent of temperature and pressure for both gaseous- and liquid-state data. From low-pressure thermal-conductivity values k* and the relationship given above, it is possible to determine thermal conductivities at any condition of temperature and pressure for which a corresponding density is available. This procedure was used to calculate reliable thermal conductivities k for high-pressure regions where experimental data were lacking.In a similar manner the critical thermal conductivity kc for argon was established directly from the critical density and the quantity kTc*. The kc value permitted the calculation of reduced thermal conductivities kR and made possible the construction of an extensive reduced-state chart. Although this correlation was developed mainly from data for argon, it was found to apply equally as well to the other inert gases as postulated from the theory of corresponding states.A comparison of thermal conductivities calculated from the reduced-state plot with over 200 experimental points produced an average deviation of 1.8% for all the inert gases. This chart was also found applicable to the diatomic gases and their mixtures but produced significant deviations for substances having more than two atoms per molecule.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030407
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  • 91
    Electronic Resource
    Electronic Resource
    Mass transfer between two liquids with chemical reaction (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 490-496 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030413
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  • 92
    Electronic Resource
    Electronic Resource
    Unsteady state heat transfer in stationary packed beds (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 513-516 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new solution is presented of the differential equations describing unsteady state heat transfer in stationary beds of small granular solid particles through which a fluid is flowing. Arbitrary initial solid temperature distribution and arbitrary variation of inlet gas temperature are allowed. The solution presented appears easier to apply in practice than those previously published and affords an example of the versatility of Fourier integrals and series. An application of the solution to the regeneration of Dow type-B butylene dehydrogenation catalyst is described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030416
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  • 93
    Electronic Resource
    Electronic Resource
    Thermal resistance of an eddy (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 523-527 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By experimental means a relation is obtained between the thermal resistance of an eddy and its angular momentum. The eddy is stationary, and no extraneous motion is present. The secondary motion which may develop in the annulus between concentric rotating cylinders is used to obtain the eddies. The fluid motion is well defined at all times and at all points of space. Heat is passed through the eddies, and the Nusselt number is obtained, which varies linearly with the angular momentum. Both Nusselt number and angular momentum vary linearly with the peripheral velocity of the inner rotating cylinder, which can be interpreted in terms of a Reynolds number associated with fluid flow perpendicular to a cylinder.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030418
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  • 94
    Electronic Resource
    Electronic Resource
    Viscous flow theory: I, Laminar Flow. Shih-I Pai. D. Van Nostrand Company, Inc., New York (1956). 384 pages. $7.75. (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 9D-9D 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030421
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  • 95
    Electronic Resource
    Electronic Resource
    Heats of vaporization of hydrogen-bonded substances (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 473-479 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method is proposed for the calculation of the heat of vaporization of hydroxylated compounds to an accuracy of about ±0.5 kcal./mole from no more data than the molecular structure and a boiling point. The older methods, by comparison, achieved an accuracy of about ±1 kcal./mole with a far greater computational effort, since they required the (usually hypothetical) critical temperature and critical pressure in addition to a boiling point.The method is here applied to aliphatic and aromatic alcohols, to ether-alcohols (e.g., the cellosolves), and to alcohols conaining keto or aldehyde groups (e.g., salicylaldehyde) and supersedes previous correlations covering the heats of vaporization of these compounds. The method can also be used to assess the quality of vapor-pressure data of the compounds covered by it.The method is based on the assumption that the heat of vaporization consists of two terms, the dispersion energy and the hydrogen-bond increment (close but not equal to the hydrogen-bond strength). The first term is calculated from a knowledge of the heat of vaporization of the equistructural hydrocarbon, now easily available from the Tables of A.P.I. Research Project 44. The hydrogen-bond term is calculated from a set of rules given in the report.The application of the increment method of this report to other properties and other functional groups is the subject of a continuing investigation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030410
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  • 96
    Electronic Resource
    Electronic Resource
    Continuous-flow stirred tank reactors: Solid-liquid systems (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 497-505 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The theory and design of continuous stirred tank reactors are extended to the complex but industrially important field of continuous-heterogeneous-reaction systems. The present investigation is concerned with the elementary process occurring when solid particles and a liquid flow into and from a single reactor or a chain of these reactors. The equations are developed for dissolution processes, and the theoretical size distributions and specific areas are confirmed experimentally. Performance is also related to operating conditions and reactor design.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030414
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  • 97
    Electronic Resource
    Electronic Resource
    Vapor-liquid equilibria and heat of mixing: n-octane-ethylbenzene-cellosolve system (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 517-522 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Vapor-liquid equilibria of the systems n-octane-Cellosolve, ethylbenzene-Cellosolve, and n-octane-ethylbenzene-Cellosolve were determined at 760 mm. Hg. The activity coefficient data of Yang and Van Winkle (23) for the system n-octane-ethylbenzene and the data of this work on other systems were expressed by Wohl's three-suffix Margules equations. The ternary data are predicted satisfactorily from the binary constants and no noticeable ternary effects seem to exist for this ternary system.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030417
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  • 98
    Electronic Resource
    Electronic Resource
    Hydroextraction: Flow in submerged cakes (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 528-534 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow equations have been proposed for hydroextractor cakes wherein the pores are filled with moving liquid. These equations have been confirmed for the effect of each variable by use of different experimental techniques. The critical wetting rate has provided the most informative steady state, in which the cake is fed with liquid to maintain the inner surface of the liquid at radius rL coincident with that of the cake at radius rc. Transient techniques have also been used wither with a probe to time the movement of a liquid level between two radii less than rc, or with a photoelectric detector to observe the coincidence of rL = rc. The tests have proved the validity of the hydrodynamic assumptions involved in the equations and have provided both precise methods for research and practical methods for industrial purposes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030419
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  • 99
    Electronic Resource
    Electronic Resource
    Agitation of non-Newtonian fluids (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 3-10 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Since the shear rate of a non-Newtonian fluid is of importance in fixing the rheological or viscometric behavior of such a material, the present study has been concerned with the development of a general relationship between impeller speed and the shear rate of the fluid. The resulting relationship was then used to interpret and correlate power-consumption data on three non-Newtonian fluids by use of a generalized form of the conventional power-number-Reynolds-number plot for Newtonians.Flat-bladed turbines from 2 to 8 in. in diameter were used exclusively. Tank diameters ranged from 6 to 22 in. and power inputs from 0.5 to 176 hp./1,000 gal. The study encompassed a 130-fold range of Reynolds numbers in the laminar and transition regions. The results to date indicate that power requirements for the rapid mixing of non-Newtonian fluids are much greater than for comparable Newtonian materials.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030103
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  • 100
    Electronic Resource
    Electronic Resource
    Material transport in turbulent gas streams: Radial diffusion in a circular conduit (1957)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 3 (1957), S. 11-15 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental studies of the mixing of coaxial streams of a natural gas and air at atmospheric pressure were made at Reynolds numbers of 44,000 and 79,000 under conditions where the turbulent-velocity profile of nearly uniform flow was altered as little as feasible by the blending of the two streams.Total diffusivities of natural gas in air for the region near the center of the conduit were computed from the data for turbulent, steady, nonuniform flow. The total diffusivities were found to be rather complicated functions of the conditions of flow. Limitations in the configuration of the apparatus did not permit a study of the behavior of the total diffusivities to be made over as wide a range of flow rates as would be necessary to investigate the large-scale trends indicated by this study.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690030104
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