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  • 1
    Electronic Resource
    Electronic Resource
    Transcription Rates and Transcript Stabilities of Macronuclear Genes in Vegetative Euplotes crassus Cells (1995)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 42 (1995), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . In hypotrichous ciliates such as Euplotes crassus genes in the transcriptionally active macronucleus are present on individual minichromosomes which occur in gene-specific copy numbers. This different degree of gene amplification can be understood as a means to preset the expression potential of the respective genetic information. In addition, the actual steady state transcript amounts are governed by the transcription rates and transcript stabilities. To establish the relative effects of these three parameters the copy numbers of genes transcribed by the three different polymerases were determined. The transcript levels of growing or starving vegetative cells were then determined, and nuclear run-on assays were performed to determine the transcription rates of the genes in the different nutritional states. A weak correlation between the gene copy numbers and transcription rates was found. The transcripts of genes synthesized by RNA polymerase II exhibited different stabilities upon starvation of the cells, compared to the supposedly stable ribosomal 5S and 26S RNA. Refeeding of the cells after starvation also resulted in a differential response with respect to the accumulation of the transcripts of different genes transcribed by RNA polymerase II, which can be interpreted in the context of the gene functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1995.tb01617.x
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  • 2
    Electronic Resource
    Electronic Resource
    On a Two-Queue Priority System with Impatience and its Application to a Call Center* (1999)
    Springer
    Methodology and computing in applied probability 1 (1999), S. 191-210 
    Details
    ISSN: 1387-5841
    Keywords: two queues ; many-server ; server reservation ; impatience ; occupancy distribution ; waiting time distribution ; approximate system ; M(n)/M(n)/s+GI ; call center application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We consider an s-server priority system with a protected and an unprotected queue. The arrival rates at the queues and the service rate may depend on the number n of customers being in service or in the protected queue, but the service rate is assumed to be constant for n 〉 s. As soon as any server is idle, a customer from the protected queue will be served according to the FCFS discipline. However, the customers in the protected queue are impatient. If the offered waiting time exceeds a random maximal waiting time I, then the customer leaves the protected queue after time I. If I is less than a given deterministic time, then he leaves the system, else he will be transferred by the system to the unprotected queue. The service of a customer from the unprotected queue will be started if the protected queue is empty and more than a given number of servers become idle. The model is a generalization of the many-server queue with impatient customers. The global balance conditions seem to have no explicit solution. However, the balance conditions for the density of the stationary state process for the subsystem of customers being in service or in the protected queue can be solved. This yields the stability conditions and the probabilities that precisely n customers are in service or in the protected queue. For obtaining performance measures for the unprotected queue, a system approximation based on fitting impatience intensities is constructed. The results are applied to the performance analysis of a call center with an integrated voice-mail-server.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010009304213
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  • 3
    Electronic Resource
    Electronic Resource
    On the distribution of the number of packets in the fluid flow approximation of packet arrival streams (1994)
    Springer
    Queueing systems 17 (1994), S. 275-315 
    Details
    ISSN: 1572-9443
    Keywords: Fluid flow approximation ; superposition ; Markov modulated rate processes ; counting process ; bursty traffic ; asymptotical normality ; complex integration ; numerical integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Fluid flow approximations are widely used for approximating models of communication systems where packet arrival streams are generated in a regular manner over certain intervals (constant rate). The appropriate mathematical model for describing those bursty arrival streams in the fluid flow framework are the well-known Markov modulated rate processes (MMRP). The paper deals with the distribution of the numberN(t) of packets in the interval [0,t] of MMRP. For two-state MMRPs and their superpositions we derive formulas for the distribution ofN(t) and its density. Further we give asymptotic results. The presented numerical results and simulation studies illustrate the goodness of the fluid flow approximation and show that the proposed numerical algorithms work well even in the case of multiplexing a large number of burst silence sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158697
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  • 4
    Electronic Resource
    Electronic Resource
    A single server model for packetwise transmission of messages (1990)
    Springer
    Queueing systems 6 (1990), S. 287-310 
    Details
    ISSN: 1572-9443
    Keywords: Single server queue ; discrete time ; batch arrivals ; spaced packets ; embedded Markov chain ; functional equation ; stationary mean queue length ; limiting results
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We study a discrete-time single-server queue where batches of messages arrive. Each message consists of a geometrically distributed number of packets which do not arrive at the same instant and which require a time unit as service time. We consider the cases of constant spacing and geometrically distributed (random) spacing between consecutive packets of a message. For the probability generating function of the stationary distribution of the embedded Markov chain we derive in both cases a functional equation which involves a boundary function. The stationary mean number of packets in the system can be computed via this boundary function without solving the functional equation. In case of constant (random) spacing the boundary function can be determined by solving a finite-dimensional (an infinite-dimensional) system of linear equations numerically. For Poisson- and Bernoulli-distributed arrivals of messages numerical results are presented. Further, limiting results are derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411479
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  • 5
    Electronic Resource
    Electronic Resource
    On the gi/m/∞ service system with batch arrivals and different types of service distributions (1989)
    Springer
    Queueing systems 4 (1989), S. 351-365 
    Details
    ISSN: 1572-9443
    Keywords: GI GI /M 1...M s /∞ ; batch arrivals ; different types of customers ; binomial moments ; batch arrival- and time-stationary probabilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We study the infinite-server system with batch arrivals ands different types of customers. With probabilityp i an arriving customer is of typei (i=1,..., s) and requires an exponentially distributed service time with parameterμ i (G GI /M 1 ...M s /∞). For theGI GI /M 1...M s /∞ system it is shown that the binomial moments of thes-variate distribution of the number of type-i customers in the system at batch arrival epochs are determined by a recurrence relation and, in steady state, can be computed recursively. Furthermore, forG GI /M 1...M s /∞, relations between the distributions (and their binomial moments) of the system size vector at batch arrival and random epochs are given. Thus, earlier results by Takács [14], Gastwirth [9], Holman et al. [11], Brandt et al. [3] and Franken [6] are generalized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159473
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  • 6
    Electronic Resource
    Electronic Resource
    A note on the stability of the many-queue head-of-the-line processor-sharing system with permanent customers (1999)
    Springer
    Queueing systems 32 (1999), S. 363-381 
    Details
    ISSN: 1572-9443
    Keywords: head-of-the-line processor-sharing ; many queues ; permanent customers ; marked point process ; stability condition ; Loynes’ construction ; ergodicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider a single server system consisting of n queues with different types of customers and k permanent customers. The permanent customers and those at the head of the queues are served in processor-sharing by the service facility (head-of-the-line processor-sharing). By means of Loynes’ monotonicity method a stationary work load process is constructed and using sample path analysis general stability conditions are derived. They allow to decide which queues are stable and, moreover, to compute the fraction of processor capacity devoted to the permanent customers. In case of a stable system the constructed stationary state process is the only one and for any initial state the system converges pathwise to the steady state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019155524681
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  • 7
    Electronic Resource
    Electronic Resource
    On the sojourn times for many-queue head-of-the-line Processor-sharing systems with permanent customers (1998)
    Springer
    Mathematical methods of operations research 47 (1998), S. 181-220 
    Details
    ISSN: 1432-5217
    Keywords: head-of-the-line processor-sharing ; many queues ; permanent customers ; sojourn times ; pseudo conservation law ; Riemann-Hilbert problem ; Dirichlet problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract We consider a single server system consisting of e queues with different types of customers (Poisson streams) andk permanent customers. The permanent customers and those at the head of the queues are served in processor-sharing by the service facility (head-of-the-line processor-sharing). The stability condition and a pseudo work conservation law will be given for arbitrary service time distributions; for exponential service times a pseudo conservation law for the mean sojourn tunes can be derived. In case of two queues and exponential service times, the generating function of the stationary occupancy distribution satisfies a functional equation being a Riemann-Hilbert problem which can be reduced to a Dirichlet problem for a circle. The solution yields the mean sojourn times as an elliptic integral, which can be computed numerically very efficiently. In case ofn ≥ 2 a numerical algorithm for computing the performance measures is presented, which is efficient forn ≤ 3. Since forn ≥ 4 an exact analytical or/and numerical treatment is too complex a heuristic approximation for the mean sojourn times of the different types of customers is given, which in case of a (completely) symmetric system is exact. The numerical and simulation results show that, over a wide range of parameters, the approximation works well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194397
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  • 8
    Electronic Resource
    Electronic Resource
    Individual blocking probabilities in the loss system $$GI + M|\vec M|N|0$$ (1996)
    Springer
    Mathematical methods of operations research 44 (1996), S. 49-74 
    Details
    ISSN: 1432-5217
    Keywords: Individual blocking probabilities ; loss system ; superposition ; embedded Markov chain ; time stationary probabilities ; intensity conservation principle ; supplemented variables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper we investigate anN server loss system, where the input is a superposition of two types of traffics, namely of a renewal process and a Poisson process. The holding times of the two customer types are exponentially distributed with different parameters. For this model, denoted by $$GI + M|\vec M|N|0$$ , we derive a numerical algorithm for computing the individual blocking (loss) probabilities. The analysis is given by constructing a two-dimensional embedded Markov chain and by using the intensity conservation principle as well as point process arguments. The results generalize those of Kuczura [8] and Willie [11]. Finally, for the $$GI + GI + M|\vec M|N|0$$ loss system we give a system of partial differential equations for the densities of the steady state distribution and discuss a special case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01246329
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  • 9
    Electronic Resource
    Electronic Resource
    Particle Image Velocimetry Applied to a Spray Jet (1994)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 11 (1994), S. 156-158 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments are described in which particle image velocimetry (PIV) is applied to the measurement of liquid droplets in a spray jet. The two velocity components in planes formed by the light sheet originating from a double-pulsed ruby laser are determined. The PIV records are evaluated with the method of Young's fringes. It is shown that this procedure allows the simultaneous measurement of the droplet size within a certain size range.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19940110208
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    Paper (German National Licenses)
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  • 10
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    On the M(n)/M(m)/s Queue with impatient Calls (1997)
    Details
    Publication Date: 2014-02-26
    Description: The paper is concerned with the analysis of an $s$ server queueing system in which the calls become impatient and leave the system if their waiting time exceeds their own patience. The individual patience times are assumed to be i.i.d.\ and arbitrary distributed. The arrival and service rate may depend on the number of calls in the system and in service, respectively. For this system, denoted by $M(n)/M(m)/s+GI$, where $m=\min(n,s)$ is the number of busy servers in the system, we derive a system of integral equations for the vector of the residual patience times of the waiting calls and their original maximal patience times. By solving these equations explicitly we get the stability condition and, for the steady state of the system, the occupancy distribution and various waiting time distributions. As an application of the \mbox{$M(n)/M(m)/s+GI$} system we give a performance analysis of an Automatic Call Distributor system (ACD system) of finite capacity with outbound calls and impatient inbound calls, especially in case of patience times being the minimum of constant and exponentially distributed times.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
    Format: application/pdf
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