bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and Catalysis of Urethane Foam Reactions
Authors: Willeboordse F.G. , Critchfield F.E. , Meeker R.L. 
Published: March 2007

Since the rates of chemical reactions in volved in cellular urethane formation are decisive for product quality, model reactions were kinetically investigated and the mech anism of catalysis was studied. A simple rela tionship found between the specific rate con stant and the molar ratio of alcohol/catalyst for an alcohol/isocyanate reaction catalyzed by stannous octoate suggests the formation of an activated intermediate complex. The balance between the alcohol/isocyan ate and water/isocyanate reaction rates is important. Organotin compounds promote the former rate more than the latter whereas the reverse holds for amine catalysts. The rates of both reactions, catalyzed by amines with and without stannous octoate as co catal yst, demonstrate a synergistic effect ex plained by the extra stability imparted to the activated intermediate complex by attach ment of the amine.
Microcellular Urethane— Processing and Applications
Authors: Reuter G. 
Published: March 2007

The basic chemical and physical proper ties of microcellular urethane are described. The methods of processing and the produc tion sequence are outlined. The ability of microcellular urethane to replace rubber and other materials in auxiliary springs, damping devices, and seals is discussed. A number of examples of current applications, particularly in the automotive industry, are given. A direct comparison between the compres sion, shear, cold flow, permanent set, fatigue strength, and effect of temperature on natural rubber and microcellular urethane is given.
Perspectives on Cultural and Individual Determinants of Teaching Style
Authors: Kennedy Judith 
Published: March 2007

Douglas Barnes and Denis Schemilt (1974) have distinguished between 'Transmission and Interpretation' Teachers. It may be that this distinction (assuming that we accept it) has its origins in an indi vidual's sense of autonomy or 'locus of control' (Rotter 1965) which may, in turn, be culturally determined. The concept of locus of con trol refers to the extent to which an individual sees his behaviour as being initiated by factors within himself (an internal locus of control), or how far he sees it as determined by external forces (an external locus of control). In order to investigate any possible relationship between a teacher's or individual's position on the Transmission-Interpretation dimension, his locus of control and culture, a pilot study was con ducted by means of a questionnaire with two groups of undergraduate (B.Ed.) students - one group from Malaysia and one from the UK. Implications of the results for teacher education and the in troduction of new methodologies are discussed.
A new line of high-accuracy computing elements based on modern semiconductor technology by
Authors: Giloi W.K. , Waldschmidt K. 
Published: March 2007

The computing elements for nonlinear operations presented in this paper are a combination of analog and digital components which combine the advantages of both techniques: large bandwidth and continuous representation of variables provided by analog techniques with accuracy and stability provided by digital techniques. The basic principle underlying these elements is to approximate functions by an appropriate power series, leading to a segmentation technique in which break-point values are calculated at high accuracy by operational digital-to-analog converters, while an interpolating increment is generated by medium-precision analog components. A whole family of high-precision multipliers, dividers, resolvers, and digitally settable function generators based on this principle will be described, as will the standard modules of which these computing elements are composed. Measured accuracies and bandwidths will be given. The new devices have good thermal stability.
Can a Shorter Workweek Reduce Unemployment?
Authors: Henize John 
Published: March 2007

A simulation model of the West German economy is being used to evaluate alternative policies for attacking the unemployment problem by reducing normal working hours. This paper reports the analysis of five policies to assess their effect on unemployment, on finances, on inflation, and on the overall economy of the country. The model includes feedback paths that have been neglected in much of the current literature, and it has yielded many surprising results. One is that a 5% reduction of the workweek would have little effect on real aggregate demand for goods and services, whether or not workers were compensated fully for the reduction in hours. Simulation results were that such a reduction in hours increased employment 3.6% if hourly pay remained unchanged and 4.4% if workers were compensated for lost wages. Not sur prisingly, the latter alternative was the more in flationary of the two. A 2.5% annual reduction in working hours was very effective in reducing unemployment. The paper goes on to discuss deficiencies in economic theory, their relation to modeling, and practical problems in forecasting. It concludes with observa tions on the role of simulation in establishing public policy.
A Second-Generation Model of Timber Harvesting
Authors: Hines Gail S. , Webster Dennis B. , Goulet Daniel V. , Sirois Donald L. 
Published: March 2007

Increased demand for wood and wood products coupled with changes in timber harvesting systems in the Southeastern United States from a labor-intensive to a more costly, almost totally mechanized opera tion requires optimal use of harvesting equipment. Simulation can provide an inexpensive tool for evaluating harvesting procedures or use of new equipment. Existing harvesting simulation models were evaluated and found to be insufficiently documented and diffi cult for one lacking computer experience to use. No consensus of what constitutes the essential elements of a model exists. This paper presents the design criteria for a new second-generation model that will be modular, user- oriented, and uniform in the level of detail it provides.
RSMM: A network language for modeling pollutants in river systems
Authors: Rao Narasinga B. , Standridge Charles R. , Schnoor Jerald L. 
Published: March 2007

Predicting the steady state distribution of pollutants in rivers is important for water quality managers. A new simulation lan guage, the River System Modeling Methodology (RSMM), helps users construct simulation models for analyzing river pollution. In RSMM, a network of nodes and branches represents a river system. Nodes represent elements such as junctions, dams, withdrawals, and pollutant sources; branches represent homo geneous river segments, or reaches. The RSMM processor is a GASP V program. Models can employ either the embedded Streeter-Phelps equations or user supplied equations. The user describes the network diagram with GASP- like input cards. RSMM outputs may be printed or stored in an SDL™* database. An interface between SDL and DISSPLA provides high quality graphical output.
Simulation based design of hydraulic servo-controlled apparatus for damping measurement
Authors: Foster Colin G. , Hooker Robert J. 
Published: March 2007

An apparatus for the measurement of damping properties of materials under biaxial stress conditions utilizes three electro- hydraulic servo-systems to apply fluctuating internal, external, and axial pressures to a hollow cylindrical specimen. The ar rangement imposes difficulties with respect to specimen loading, system interactions, stability and control. An analog simulation was conducted as a direct step in the design procedure in order to prove the feasibility of the apparatus, to provide guidance in the choice of design parameters, and to investigate system operating conditions and procedures. The simulation and its use with respect to both design and opera tion of the apparatus are described. In the simulation, account is taken of servo-valve characteristics, fluid leakage paths, specimen deflection, chamber volumes, and fluid compressibil ity. The (successful) performance of the apparatus as built is also described, and the similarity of simulated and actual behaviour is apparent.
Microcomputer implementation of simulation benchmarks in heat-transfer and dynamic process analysis
Authors: Jacques Michael St. 
Published: March 2007

In order to foster a better understanding of realistic microcom puter capability, a diverse group of mathematical models, writ ten in FORTRAN, are considered from the standpoint of run ning efficiency. Benchmark results are reported for a variety of computer systems including a mainframe, two minicomputers, and two microcomputers. A description of the simulations, which cover a wide range of complexity, is included. One of the models is a dynamic, two- component material balance of a paper machine. Eleven variable level chests (tanks), a number of intricate controls, and about one hundred stream equations make this model comprehen sive enough to be generally associated with a mainframe, or with very powerful minicomputer systems. Another dynamic simula tion emulates the thermal and stress behavior of flat, injection- molded parts during cooling. It is representative of models based on the one-dimensional, transient heat-conduction equation. Also considered is a steady-state, finite-difference model for prediction of temperature profiles in shell and tube heat ex changers. This simulation employs an efficient, sparse-matrix technique similar to equation solution methods found in finite- element software. Other less comprehensive models, often used as subroutines in process analysis and control, are examined. These include a pump curve versus system resistance search, and a control valve position versus flow computation. Both of these subroutines use iterative solution techniques. The advantages and disadvantages of using the microcomputer are discussed. A range of bounds is established on the feasibil ity of implementing and using a model on a microcomputer in terms of real simulations and run times. The results of this work are very encouraging and indicate a definite place for the microcomputer in simulation work.
Simulation modeling for hospital bed planning
Authors: Dumas M. Barry 
Published: March 2007

A computer simulation model was developed to address the problem of allocating beds to hospital services, by bed type and sex. The model, written in Simscript II.5, was designed to per mit experimentation with and evaluation of bed usage policies and admissions rules as well as allocation plans. Using the model, hospital beds at the Mount Sinai Medical Center, New York City, were reallocated. Incorporated in this reallocation was the creation of a new service. Also developed was a revised elective admissions reservation board. An altered view of measures of performance was another outcome. Discussion in this paper will center around the allocation prob lem, the simulation model, the performance measures, the hos pital configurations, the experiments and the results obtained.
A practical methodology for ambulance location
Authors: Uyeno Dean H. , Seeberg C. 
Published: March 2007

An ambulance location system was created for the British Co lumbia Provincial Ambulance Service. It was applied in the Capital Regional District (an area of about 937 square miles). The system helps administrators locate ambulances to improve response to calls. The system consists of three parts: a means to reduce data to manageable proportions, a P-Median model for the determina tion of rough locations, and a computer simulation model for fine tuning of locations. The system worked well. The method of data reduction proved both practical and efficient. The rough locations provided by the P-Median model provided an excellent starting solution. The simulation model was shown to be ac curate in comparison with actual Capital Regional District data. The model was used with confidence to do a number of useful experiments concerning optimal ambulance locations and system response to changes in demand levels. The validated system was used to answer many "what if" ques tions such as those that follow: Are vehicles located in the best manner? If we move one unit to reduce complaints from area A, how will this affect service in area B? If we get more units, should we locate them incremen tally or would it be better to relocate all bases? How much can we hedge against expected future demands? How should we space shifts? How should we determine the number of crews per shift?
Developing generalized reactor modules for a process simulator
Authors: Upadhye R.S. , Anselmo K.J. , Schiesser W.E. 
Published: March 2007

Reactors, essential in chemical process simulation, are complex equipment characterized by simultaneous heat, mass and momentum transfer, and by chemical reactions. Traditionally, reactors have been modeled on an individual basis determined by the reactor type and the application. A process simulator, however, requires complete reactor capabilities; the classical ap proach leads to a bewildering array of special reactor unit modules both expensive to develop and to maintain. Consequently, the authors have developed the concept of generalized reactor modules; this paper presents the concept and a methodology for implementing it. Conceptually, reactor simulation is divided into six parts: equipment, stoichiometry, kinetics, data, mathematical software and executive routine. The conservation and equilibrium relationships are built into the equipment modules; system stoichiometry and reaction kinetics are user defined; kinetic parameter data are either input by the user or can be read from a user-specified kinetic data file; quality mathematical software from commerically available packages is used to solve the model equations; and the executive routine puts all these pieces together, manages the calculations scheme, and outputs the desired results. Carberry' and Levenspiel2 discuss models for various reactor types as well as the reaction kinetics needed in these models; they also address the important issue of how these idealized models can be used to simulate real reactors. This approach has been applied in developing several reactor modules for a process simulator. These include steady state CSTR, plug flow, and dispersion reactors and a transient tubular dispersion reactor with continuous catalyst deactivation. Research and process engineers use these modules to simulate reactors with arbitrary stoichiometry, kinetics and kinetic data. An important feature of all these modules is that quality, commercially available software was used wherever possible. This allowed more time to be devoted to model formulation and user support and to quickly develop very sophisticated modules which are easily maintained.
A disaggregate population model of China
Authors: Qifan Wang  , Sterman John D. 
Published: March 2007

A disaggregate population model of China is presented: the age structure is represented by one-year cohorts; urban and rural populations are distinguished; birth and death rates, family size, life expectancy, and other demographic variables are determined endogenously. The model can be used to analyze population problems and to project population size, the age structure, the adult labor force, the elderly population, and so on. The model can be used in two modes: to project the consequences of various exogenous fertility levels and to determine endogenously birth rates and fertility by economic inputs such as food supply, GDP, and services. Socioeconomic factors important in the demo graphic transition are incorporated into the model, such as the effect of perceived life expectancy on fertility, the effects of tradi tional values, and the ability of government to influence family fertility choices. Policies and programs designed to control population growth, such as delayed marriage age, improved con traception, and restrictions on family size can be evaluated. Required inputs are industrial, service, and food output per worker, and also the level of pollution. The model should be thought of as a component of a comprehensive planning model which generates these inputs endogenously. Based on the system dynamics approach to modeling complex systems, the model is implemented in the DYNAMO simulation language.
Mechanics of Elastic Performance of Textile Materials
Authors: Platt Milton M. , Klein William G. , Hamburger Walter J. 
Published: March 2007

Theoretical analyses are given of the effects of fiber properties and yarn structure on singles yarn bending rigidity, assuming the fibers to be elastically isotropic and to exhibit linear stress—strain behavior. The two extreme cases of complete freedom and no freedom of relative fiber motion are analyzed. The effects on yarn rigidity of fiber dimensions, fiber stiffness, torsional to bending rigidity ratio, yarn density, size, twist, fiber clustering, and prior relaxation treatments are analytically investigated. 1. Where freedom of fiber motion prevails, yarn rigidity is equal to the sum of fiber bending rigidities geometrically modified by yarn twist in a manner such that twist increases produce decreases in yarn rigidity. 2. For most practical yarns, residual torsional stresses produce only a minor influence (increase) in yarn rigidity. 3. Relaxation of twisting stresses prior to yarn bending alters very slightly the effects of yarn twist on rigidity. Conaequently only changes in fiber modulus produced by relaxation are of significance. 4. Fiber clustering, i.e., the aggregate action of groups of fibers, produces marked increases in yarn rigidity, roughly proportional to the number of fibers per cluster. 5. The extreme case of fiber clustering, i.e., no freedom of relative fiber motion, results in rigidity of the order of the number of fibers in the yarn divided by the yarn packing factor times the rigidity obtained when freedom of motion prevails. The rigidity of blended yarns is discussed, and the interaction of gross yarn structure, properties of the fibers being blended, and their spatial distributions qualitatively analyzed. 1. For a uniform blend distribution, total rigidity is determined from the summative rigidities of the fibers, modified by yarn twist to the same proportionate extent as is a self-fiber yarn. 2. Location of fibers in a nonuniform blend determines not only the yarn rigidity but also its variation with twist. Generally, when stiffer fibers predominate in the core of the yarn, less rapid decreases in rigidity with twist increases take place than in a uniform blend ; the converse is true when the stiffer fibers are present in the yarn sheath. 3. Changes in fiber location resulting from twist or blend changes can significantly affect yarn rigidity.
Some Theoretical Considerations of Cellulose Cross-Linking
Authors: Garden John L. , Steele Richard 
Published: March 2007

Much available chemical evidence supports the hypothesis that covalent cross-linking is the best way to improve the resilience of cellulosic fabrics. This paper reviews the theories relating physical properties to cross-linking in rubbery polymers and shows that they apply in some qualitative aspects to cellulose. Particularly, the observed changes in swelling, solubility, modulus, tensile strength, and resilience are consistent with these theories. On the basis of published data, the concentration of intermolecular cross links is esti mated ; it is found that at least every twenty-fifth accessible anhydroglucose unit has to be intermolecularly cross-linked when maximum crease recovery values are attained. In rubbery polymers, substantial changes in mechanical properties are obtained at much lower levels of cross-linking. This difference between cellulose and rubbers in response to cross-linking is probably due to the polar nature of cellulose.
Studies in the Light Absorption of Dyes.1
Authors: Giles C.H. , Rahman S.M.K. , Smith D. 
Published: March 2007

A linear relation between the logarithm of the color concentration of a diffusely reflect ing colored surface and its reflectance density is derived as a simple extension of Beer's law and confirmed experimentally using a variety of dyed fabrics. The experimental results indicate that Beer's law is not usually obeyed by the dye present in dyed materials, probably on account of the presence of adsorbed dye aggre gates. It is in fact only obeyed by true solutions or by suspensions of particles of con stant size distribution. The application of Beer's law to transmission and reflection systems is discussed, and it is shown that a more general relation is obtained by substituting for c, the color con centration factor in the Beer's law formula, the empirical factor ( c/1 +acx ). where a and x are constants (probably functions of the refractive index difference between the dye and surrounding medium), and x is a simple fraction. In a test with dyed viscose rayon fabrics it is shown that about 20% of the reflected light is specutarty reflected from the surfaces of lightly dyed fibers.
Studies in Wool Yellowing
Authors: Kirkpatrick A. , Maclaren J.A. 
Published: March 2007

Disulfide groups in wool have been converted to thioether groups by reduction and subsequent alkylation. In this way wool fabric that contained only 7-19%, of the original cystine content and that were almost identical in appearance with untreated fabrics were prepared. The rates of yellowing of these fabrics and of controls that were alkylated without prior reduction were studied under conditions of heat, hot alkali, and uv irradiation. The rate of yellowing of the modified wools was at least as great as that of untreated wool, and this suggests that the decomposition of disulfide groups is not of major importance in the yellowing process.
Electron Microscopic Observations on Cellulose Graft Copolymers: Radiation Induced Rayon-Styrene Graft Copolymers1
Authors: Kaeppner Werner M. , Huang Robert Y-M. 
Published: March 2007

Three types of commercial rayon (Fortisan, high-tenacity tire yarn, and modifier- type, high wet modulus yarn) were grafted with styrene, using the direct radiation method with gamma-rays from Co-60. The grafted filaments were examined in the electron microscope to investigate their morphology and fine structure, the location and distribution of polystyrene in the fiber, and whether the polystyrene was truly grafted. In all three grafted fibers, the polystyrene was distributed throughout the cross sec tion of the filament and also appeared on the surface. As a result, the filaments expanded isometrically during grafting, but retained their original shape. The polystyrene grafted to the surface of the filament followed the original surface striations of the rayon and appeared as protruding ridges and valleys, rather than as uniform surface layers. The polystyrene inside the filament could not be removed hy exhaustive extraction of the intact yarn with benzene, but some of it could be removed by extracting the ultra-thin cross sections (ca. 500 Å thick) used for electron microscopic observations. The main portion of these ultri-thin sections was insoluble in solvents for both polystyrene and cellulose and is considered to be a true cellulose-styrene graft. The changes induced in the fine structure of the cross sections by alternate extraction with solvents for polystyrene and cellulose were followed, using the electron microscope. From a macroscopic viewpoint, it was concluded that the styrene grafted rayons are homogeneous. At a molecular level, however, they consist of a gross heterogeneous mixture of polystyrene homopolymer, cellulose, and true cellulose-styrene graft co polymer.