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  • 1
    Electronic Resource
    Electronic Resource
    Experimental determination and modeling of the heat capacity of coal in various atmospheres (1987)
    Springer
    International journal of thermophysics 8 (1987), S. 133-145 
    Details
    ISSN: 1572-9567
    Keywords: atmospheric effects ; coal ; heat capacity ; modeling ; water desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the development of transferable measurement techniques for the heat capacity of raw coal, it was observed that the atmosphere in sealed sample cells affected the thermal behavior, particularly during the initial measurements. The model which had been used to represent the specific heat of coal did reproduce the results in air but failed to reproduce the deep exotherm of the thermograms obtained in nitrogen. The specific heat of coal has been determined in helium, argon, and carbon monoxide to provide insight into possible modifications to the model. The results of initial and repeat runs in the five different atmospheres and the impact of these results on the modeling are presented and discussed. The agreement between the experimental heat capacity and that predicted by the model, up to 500 K, is excellent and supports Merrick's predictions for the heat capacity of coal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503229
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Computer model of a porous medium (1988)
    Springer
    International journal of thermophysics 9 (1988), S. 1061-1069 
    Details
    ISSN: 1572-9567
    Keywords: clusters ; diffusivity ; fractal dimension ; percolation threshold ; porous model ; random channel widths ; random walk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A computer model has been set up to represent a porous medium. The basis for this model is a two-dimensional square network (100×100) of channels that have randomly assigned widths between the value of zero (closed) and the value of one (open, unrestricted flow). The channel width assignments have been made by a random selection from five different distributions:f(q)=q, f(q)=sinq, f(q)=erf(q),f(q)=1−sinq, andf(q)=1 −erf(q). Diffusion of particles in the network has been studied by a random-walk procedure for each realization of the channel width assignments. The diffusivity is quite sensitive to the distribution of channel widths. The percolation properties of the networks obtained from the three most restrictive distributions have been investigated and the independent, linked clusters within the network have been determined. For cluster sizes that are less than the full width of the network, the network does not percolate and either the flow is not diffusive or the diffusivity is severely reduced. An approximate value for the percolation threshold has been determined in each case and the fractal dimension has been calculated also.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133273
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Anti-IgA antibodies in IgA-deficient children (1988)
    Springer
    Journal of clinical immunology 8 (1988), S. 356-361 
    Details
    ISSN: 1573-2592
    Keywords: IgA deficiency ; anti-IgA antibodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract IgG and IgM isotype antibodies to polyclonal human IgA, myeloma IgA1, and myeloma IgA2 were estimated in 38 IgA-deficient children aged between 0.9 and 15 years. All children had IgM anti-IgA antibodies. IgG antibodies against either polyclonal IgA, IgA1, or IgA2 were present in 63% of the IgA-deficient children. IgG anti-IgA antibodies were detected against all three antigens in 8 of 11 severely IgA-deficient children and in 7 of 27 partially IgA-deficient children, but in only 1 of 23 healthy adult controls. The proportion of children with IgG anti-IgA antibodies was significantly greater in the severely IgA-deficient group in comparison with the partially IgA-deficient group and the adult controls (chi-square test,P〈0.01 andP〈0.005, respectively). There was a strong correlation within each IgG subclass between antibody responses toward each of the three IgA antigens. Twenty-four children were followed over a period ranging from 0.9 to 11 years (mean, 2.3 years). Three children who were initially IgG anti-IgA antibody negative became antibody positive and three who were antibody positive became antibody negative. Five children with severe IgA deficiency remained severely IgA deficient and IgG antibodies to IgA persisted in all five at follow-up. The presence of IgG anti-IgA antibodies did not influence the normalization of serum IgA at follow-up in 14 of 19 children who were initially partially IgA deficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00917151
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A “gel” model for coal (1985)
    Springer
    International journal of thermophysics 6 (1985), S. 673-679 
    Details
    ISSN: 1572-9567
    Keywords: aggregate structure ; coal ; equation-of-motion method ; density dependence ; frequency spectrum ; “gel” model ; harmonic nearest-neighbor forces ; heat capacity ; hexagonal structure ; porous structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coal is a sedimentary, organic “rock” which is almost never in a state of thermal equilibrium. Because of its importance, the thermal properties of this ill-characterized substance are of great interest. Recent work has shown that coal has many of the characteristics of a gel-type structure. We have made this observation the basis for a model study of the thermal properties of a gel system, using the equation-of-motion method to determine the density of states for the system and, thereby, its heat capacity. This model has one of the essential features of a model of coal, namely, a porous structure. With a hexagonal close-packed lattice as the basis for our gel, we have calculated the frequency spectrum for several particle densities. The disorder in the system has a marked effect on the frequency spectrum, shifting a larger number of modes from high to low frequencies. Also, for a gel with 3% vacancies, and in-plane, out-of-plane bond strengths at the ratio 2∶ 1, there is a further shift to lower frequencies and the two-peaked spectrum expected for such an anisotropic structure develops. The heat capacity is affected only at low temperatures. We conclude that the gel model provides a satisfactory basis for development as a model of coal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500338
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Experiments with microcomputer-based artificial intelligence environments (1988)
    Springer
    Mathematical geology 20 (1988), S. 1037-1047 
    Details
    ISSN: 1573-8868
    Keywords: artificial intelligence ; data bases ; microcomputer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The U.S. Geological Survey (USGS) has been experimenting with the use of relatively inexpensive microcomputers as artificial intelligence (AI) development environments. Several AI languages are available that perform fairly well on desk-top personal computers, as are low-to-medium cost expert system packages. Although performance of these systems is respectable, their speed and capacity limitations are questionable for serious earth science applications foreseen by the USGS. The most capable artificial intelligence applications currently are concentrated on what is known as the “artificial intelligence computer,” and include Xerox D-series, Tektronix 4400 series, Symbolics 3600, VAX, LMI, and Texas Instruments Explorer. The artificial intelligence computer runs expert system shells and Lisp, Prolog, and Smalltalk programming languages. However, these AI environments are expensive. Recently, inexpensive 32-bit hardware has become available for the IBM/AT microcomputer. USGS has acquired and recently completed Beta-testing of the Gold Hill Systems 80386 Hummingboard, which runs Common Lisp on an IBM/AT microcomputer. Hummingboard appears to have the potential to overcome many of the speed/capacity limitations observed with AI-applications on standard personal computers. USGS is a Beta-test site for the Gold Hill Systems GoldWorks expert system. GoldWorks combines some high-end expert system shell capabilities in a medium-cost package. This shell is developed in Common Lisp, runs on the 80386 Hummingboard, and provides some expert system features formerly available only on AI-computers including frame and rule-based reasoning, on-line tutorial, multiple inheritance, and object-programming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00892978
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    Paper (German National Licenses)
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