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  • Articles  (25)
  • Chemical Engineering  (14)
  • Engineering General  (8)
  • Male
  • 1985-1989  (25)
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  • Articles  (25)
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  • 1
    Electronic Resource
    Electronic Resource
    A semi-empirical algorithm for flow balancing in multi-cavity transfer molding (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 749-761 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Multi-cavity transfer molding is an important process step in several electronic and photonic technologies. In some applications, uniform filling of the cavities of the mold, or mold balancing, is required. A semi-empirical flow model to predict mold filling patterns was developed. The algorithm is a one-dimensional network flow simulation that uses experimental pressure drop data to determine the volumetric flow rate through the gates and runners. A comprehensive experimental program was undertaken to determine these hydraulic resistances for different flow rates and mold geometries. A theoretical treatment is also described to compute hydraulic resistance from gate geometry. Uniform gate resistances provide unbalanced filling and higher velocities in the cavities. Balanced filling can significantly reduce the molding compound velocity and the flow induced stresses, but imperfect balancing compromises the benefits. Experimental filling patterns were obtained for two sets of gates. The agreement between the model and the experiments was satisfactory, and the discrepancies were attributed to correctable phenomena.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760291108
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  • 2
    Electronic Resource
    Electronic Resource
    “A semi-empirical algorithm for flow balancing in multi-cavity transfer molding” (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1796-1796 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760292409
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  • 3
    Electronic Resource
    Electronic Resource
    A new approach to capillary viscometry of thermoset transfer molding compounds (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1399-1404 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new capillary rheometer incorporated in an instrumented transfer molding press has been developed. This rheometer is effective for determining the viscosity characteristics of thermoset molding compounds under both isothermal and typical molding conditions. In examples of the rheometer's utility, the power law indices of two commercial epoxy molding compounds have been determined to be approximately 0.7. Additionally it has been shown that preconditioning typical epoxy compounds at 47 percent relative humidity causes a viscosity decrease of about 40 percent owing to plasticization of the epoxy resin.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760262008
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  • 4
    Electronic Resource
    Electronic Resource
    Volume change and the nonlinearly thermo-viscoelastic constitution of polymers (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 86-100 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The time-dependent behavior of linearly viscoelastic materials is known to be very sensitive to changes in temperature and in solvent (water) concentration. Following an investigation by the authors of this sensitivity in terms of the associated small volume changes, a nonlinearly viscoelastic model of constitutive behavior was formulated earlier in terms of the free volume concept and evaluated in terms of experiments on poly(vinyl acetate). Following a brief presentation of the earlier results these concepts are expanded and refined in the present paper to deal with transient deformation histories under pressure. In this connection, model computations explore the effect of simultaneous pressurization and straining. In addition the effect of “ageing” the polymer under pressures of various magnitudes and for different lengths of time are investigated. It becomes clear that the yield phenomenon depends sensitively on pressure and on the ageing time. In addition, the volume change under transient thermal histories in the glass transition range is explored, largely in terms of Kovacs' experimental data and attendant computations. These considerations are presented from a unified point of view of nonlinear thermoviscoelastic constitutive behavior, principally with phenomenological material description in mind. These computations provide guidance to the design of experiments for the proper determination of the relevant material functions and seem to indicate a need for the reevaluation of certain experimental procedures in the time histories of thermal material characterization.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760270113
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  • 5
    Electronic Resource
    Electronic Resource
    Conservative calculations of non-isentropic transonic flows (1985)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 5 (1985), S. 1047-1057 
    Details
    ISSN: 0271-2091
    Keywords: Transonic Flow ; Modified Potential ; Finite Elements ; Non-isentropic Flow ; Conservative Method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The classical potential formulation of inviscid transonic flows is modified to account for non-isentropic effects. The density is determined in terms of the speed as well as the pressure, which in turn is calculated from a second-order mixed-type equation derived via differentiating the momentum equations.The present model differs in general from the exact inviscid Euler equations since the flow is assumed irrotational. On the other hand, since the shocks are not isentropic, they are weaker and are placed further upstream compared to the classical potential solution. Furthermore, the streamline leaving the aerofoil does not necessarily bisect the trailing edge.Results for the present conservative calculations are presented for non-lifting and lifting aerofoils at subsonic and transonic speeds and compared to potential and Euler solutions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650051204
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  • 6
    Electronic Resource
    Electronic Resource
    Finite element stream function-vorticity solutions of the incompressible Navier-Stokes equations (1987)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 7 (1987), S. 17-27 
    Details
    ISSN: 0271-2091
    Keywords: Finite Element ; Navier-Stokes Stream ; Function Vorticity ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The incompressible, two-dimensional Navier-Stokes equations are solved by the finite element method (FEM) using a novel stream function/vorticity formulation. The no-slip solid walls boundary condition is applied by taking advantage of the simple implementation of natural boundary conditions in the FEM, eliminating the need for an iterative evaluation of wall vorticity formulae. In addition, with the proper choice of elements, a stable scheme is constructed allowing convergence to be achieved for all Reynolds numbers, from creeping to inviscid flow, without the traditional need for upwinding and its associated false diffusion. Solutions are presented for a variety of geometries.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650070103
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  • 7
    Electronic Resource
    Electronic Resource
    On the computation of weakly separated laminar flows in a smoothly expanding channel (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 3 (1987), S. 327-333 
    Details
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In Reference 1, a summary of results of numerical solutions to steady-state laminar flows in an expanding planar channel from 15 research groups was presented. Both vorticity and pressure values computed along a wall of the channel were compared. This paper presents some possible explanations for the wide discrepancies in these computed results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1630030415
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  • 8
    Electronic Resource
    Electronic Resource
    Direct solution procedure for solution of harmonic problems using complete, non-singular, Trefftz functions (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 5 (1989), S. 159-169 
    Details
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Boundary approximation solutions using a singular Green function basis have been widely applied to the solution of a variety of linear problems. To avoid the difficulties associated with integration over singularities it is convenient to use sets of non-singular, complete Trefftz functions, and this procedure has been applied recently with success using an indirect formulation. In the paper we observe that direct formulation is here again possible and that for some problems it performs in a superior way.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1630050304
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  • 9
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    Physical mapping of a translocation breakpoint in neurofibromatosis (1989)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1989-06-02
    Description: The gene for von Recklinghausen neurofibromatosis (NF1), one of the most common autosomal-dominant disorders of humans, was recently mapped to chromosome 17 by linkage analysis. The identification of two NF1 patients with balanced translocations that involved chromosome 17q11.2 suggests that the disease can arise by gross rearrangement of the NF1 locus, and that the NF1 gene might be identified by cloning the region around these translocation breakpoints. To further define the region of these translocations, a series of chromosome 17 Not I-linking clones has been mapped to proximal 17q and studied by pulsed-field gel electrophoresis. One clone, 17L1 (D17S133), clearly identifies the breakpoint in an NF1 patient with a t(1;17) translocation. A 2.3-megabase pulsed-field map of this region was constructed and indicates that the NF1 breakpoint is only 10 to 240 kilobases away from 17L1. This finding prepares the way for the cloning of NF1.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fountain, J W -- Wallace, M R -- Bruce, M A -- Seizinger, B R -- Menon, A G -- Gusella, J F -- Michels, V V -- Schmidt, M A -- Dewald, G W -- Collins, F S -- NS22224/NS/NINDS NIH HHS/ -- NS23410/NS/NINDS NIH HHS/ -- NS23427/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1989 Jun 2;244(4908):1085-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, University of Michigan, Ann Arbor 48109.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2543076" target="_blank"〉PubMed〈/a〉
    Keywords: *Chromosome Mapping ; *Chromosomes, Human, Pair 17 ; Cloning, Molecular ; DNA Restriction Enzymes ; Electrophoresis ; Female ; Genetic Linkage ; Humans ; Hybrid Cells ; Male ; Neurofibromatosis 1/*genetics ; *Translocation, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 10
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    Long-term neuropathological and neurochemical effects of nucleus basalis lesions in the rat (1987)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1987-11-13
    Description: The long-term effects of excitotoxic lesions in the nucleus basalis magnocellularis of the rat were found to mimic several neuropathological and chemical changes associated with Alzheimer's disease. Neuritic plaque-like structures, neurofibrillary changes, and neuronal atrophy or loss were observed in the frontoparietal cortex, hippocampus, amygdala, and entorhinal cortex 14 months after the lesions were made. Cholinergic markers in neocortex were reduced, while catecholamine and indoleamine metabolism was largely unaffected at this time. Bilateral lesions of the nucleus basalis magnocellularis increased somatostatin and neuropeptide Y in the cortex of the rat by at least 138 and 284 percent, respectively, suggesting a functional interaction between cholinergic and peptidergic neurons that may differ from that in Alzheimer's disease.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arendash, G W -- Millard, W J -- Dunn, A J -- Meyer, E M -- HD 17933/HD/NICHD NIH HHS/ -- New York, N.Y. -- Science. 1987 Nov 13;238(4829):952-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, University of South Florida, Tampa 33620.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2890210" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylcholinesterase/metabolism ; Animals ; Biogenic Amines/metabolism ; Brain/metabolism/*pathology ; Cerebral Cortex/metabolism/*pathology ; Choline/metabolism ; Choline O-Acetyltransferase/metabolism ; Male ; Neuropeptide Y/analysis ; Olivary Nucleus/*physiology ; Organ Specificity ; Rats ; Rats, Inbred Strains ; Somatostatin/analysis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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