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  • Springer  (56)
  • American Institute of Physics (AIP)  (5)
  • Oxford University Press  (4)
  • 1985-1989  (63)
  • 1960-1964  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Self-consistent T-matrix solution for the effective elastic properties of perfectly disordered multiphase solids (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 1809-1813 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent solution for the effective elastic properties of polycrystalline and perfectly disordered multiphase composites has been discussed by using the T-matrix method under certain suitable approximations. Compared to the existing formulas these new relations for the disordered composites are very useful in practical situations for a quick and more accurate estimate of the effective elastic properties, in particular for a case where the composite has components with widely different values of the elastic constants. For comparison we have discussed the results based on Kröner's theory which also purports to solve the same problem. It is found that the two solutions do not agree. To resolve the difference we take help of Hill's exact solution of the composite problem when the components have equal rigidities. It is found that while Kröner's theory is inconsistent with the exact result the present self-consistent solution analytically reproduces it. Another interesting finding of the present investigation is that the approximations made in obtaining the self-consistent solution are exact in the limit of composites with equal-shear moduli. Finally it is indicated that although the results for composites have been derived for isotropic and cubic components it can be easily adapted for a composite with noncubic components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336032
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  • 2
    Electronic Resource
    Electronic Resource
    Method for producing neutral and negative hydrogen particles applicable to hot plasma diagnosis (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2158-2162 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method is described whereby a beam of positive hydrogen ions incident at grazing angles on an array of cesium-covered tungsten foils is used to produce H0 and H− particles by negative surface ionization. The results of these experiments indicate that the method can provide diagnostic beams of particles to hot plasmas and can also energy-analyze charge exchange neutrals emerging from hot plasmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139979
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  • 3
    Electronic Resource
    Electronic Resource
    A Green's function approach to third-order elastic constants of disordered solids (1986)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 27 (1986), S. 2807-2812 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Starting from a Lippmann–Schwinger-type equation, which is very similar to that of quantum mechanical multiple scattering theory, Zeller and Dederichs [Phys. Status Solidi B 55, 831 (1973)] have developed the effective medium theory. This theory has found wide application in understanding the mechanical behavior of disordered solids. However, unlike the problem in quantum mechanics, this equation of the random elasticity is only approximate since this is a linear response theory. So, it is proposed in this work for the first time to go beyond this approximation to treat nonlinear properties of such solids of which the third-order elastic constant is a generic. Again, so far as the nonlinear elastic behavior of these solids is concerned, no work has been done except the simple Voigt- and Reuss-type averaging. Both are extreme approximations and are, moreover, known to lead to violation of the equilibrium condition. The salient feature of the present calculation is to get an exact formal solution of the problem in terms of an appropriate Green's function in a closed form. The result obtained is quite general and may be adopted to treat nonlinearity in any tensor property of disordered materials. Finally several approximations, including a self-consistent solution, have been discussed for obtaining the effective nonlinear static mechanical susceptibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527256
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  • 4
    Electronic Resource
    Electronic Resource
    Elastic properties of a computer-simulated polycrystalline aggregate of a single component (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1844-1848 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple procedure involving sound velocities in component crystallites has been developed to calculate the effective elastic properties of a hypothetical aggregate which is macroscopically homogeneous but has fluctuations on a microscopic scale, with the underlying assumption that the sound wave can distinguish between the different crystallites oriented at random. For comparison we have also employed the effective medium theory based on a static deformation scheme to calculate the effective elastic properties of the same hypothetical aggregate. Both the procedures use the identical set of input data. Although the assumptions on which the above dynamic and static methods are based are entirely different the results obtained from them for seventeen different aggregates are remarkably close to each other and also to experiments done on polycrystalline specimens using ultrasonic velocities. Finally, a critical discussion of the results and their consequences is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334413
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  • 5
    Electronic Resource
    Electronic Resource
    Two-dimensional turbulent boundary layers over rigid and moving swept wavy surfaces (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 964-970 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The two-dimensional, incompressible, turbulent boundary layer over a flexible wall is analyzed. The wall consists of sinusoidal waves that are swept with respect to the flow direction. The mean flow is a boundary layer with wave-induced stresses. These stresses are evaluated from the solution of the linear problem. It is found that the small mean skin friction reduction, observed for the case of zero sweep, persists. The pressure drag reduces for swept wavy wall from its value for no sweep. There is a small drag reduction for the moving wall cases even for the lowest phase speed considered. Within the assumptions of the turbulence model used, a possible drag reduction mechanism is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865691
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanical properties of oriented fibres of semicrystalline polymers based upon orientation function from optical properties (1986)
    Springer
    Colloid & polymer science 264 (1986), S. 128-130 
    Details
    ISSN: 1435-1536
    Keywords: Orientation of polymer chains ; mechanical properties ; birefringence ; deformation scheme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The computation of the orientational averages is a great problem in the case of semicrystalline polymers. In a previous communication [1] it has been shown that sinθ=f(λ) sinθ′ describes the orientational changes satisfactorily for a certain class of polymers. In this paper some alternative deformation schemes are also discussed. It has been concluded that birefringence provides a useful guideline in the choice of a deformation scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01414838
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  • 7
    Electronic Resource
    Electronic Resource
    A single server queue with gated processor-sharing discipline (1989)
    Springer
    Queueing systems 4 (1989), S. 249-261 
    Details
    ISSN: 1572-9443
    Keywords: Processor-sharing ; discrimination function ; gating mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we consider a single server queue in which arrivals occur according to a Poisson process and each customer's service time is exponentially distributed. The server works according to the gated process-sharing discipline. In this discipline, the server provides service to a batch of at mostm customers at a time. Once a batch of customers begins service, no other waiting customer can receive service until all members of the batch have completed their service. For this queue, we derive performance characteristics, such as waiting time distribution, queue length distribution etc. For this queue, it is possible to obtain the mean conditional response time for a customer whose service time is known. This conditional response time is a nonlinear function (as opposed to the linear case for the ordinary processor-sharing queue). A special case of the queue (wherem=∞) has an interesting and unusual solution. For this special case, the size of the batch for service is a Markov chain whose steady state distribution can be explicitly written down. Apart from the contribution to the theory of Markov chains and queues, the model may be applicable to scheduling of computer and communication systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02100269
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  • 8
    Electronic Resource
    Electronic Resource
    Assembly-like queues with finite capacity: Bounds, asymptotics and approximations (1986)
    Springer
    Queueing systems 1 (1986), S. 67-83 
    Details
    ISSN: 1572-9443
    Keywords: Assembly queue ; manufacturing ; approximations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we study a queueing model of assembly-like manufacturing operations. This study was motivated by an examination of a circuit pack testing procedure in an AT & T factory. However, the model may be representative of many manufacturing assembly operations. We assume that customers fromn classes arrive according to independent Poisson processes with the same arrival rate into a single-server queueing station where the service times are exponentially distributed. The service discipline requires that service be rendered simultaneously to a group of customers consisting of exactly one member from each class. The server is idle if there are not enough customers to form a group. There is a separate waiting area for customers belonging to the same class and the size of the waiting area is the same for all classes. Customers who arrive to find the waiting area for their class full, are lost. Performance measures of interest include blocking probability, throughput, mean queue length and mean sojourn time. Since the state space for this queueing system could be large, exact answers for even reasonable values of the parameters may not be easy to obtain. We have therefore focused on two approaches. First, we find upper and lower bounds for the mean sojourn time. From these bounds we obtain the asymptotic solutions as the arrival rate (waiting room, service rate) approaches zero (infinity). Second, for moderate values of these parameters we suggest an approximate solution method. We compare the results of our approximation against simulation results and report good correspondence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01149328
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  • 9
    Electronic Resource
    Electronic Resource
    Studies on monocyclopentadienyl titanium(IV) dithiocarbamato complexes (1985)
    Springer
    Monatshefte für Chemie 116 (1985), S. 431-436 
    Details
    ISSN: 1434-4475
    Keywords: Cyclopentadienyl ; Titanium(IV) complexes ; Conductometric ; IR ; 1H-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurden Titan(IV)-dithiocarbamat-Komplexe vom TypCpTi(S2CNHR)Cl2 undCpTi(S2CNHR)2Cl mitR=C8H5N2S, C9H5N2SCl2 und C9H7N2S mittels der Reaktion von Monocyclopentadienyltitan(IV)trichlorid mit dem Kaliumsalz der entsprechenden Dithiocarbaminsäure in wasserfreiem Dichlormethan dargestellt. Leitfähigkeitsmessungen und IR-Untersuchungen zeigen, daß diese Komplexe Nichtelektrolyte sind, bei denen alle Dithiocarbamat-Liganden zweizähnig sind. Demnach können 5-, bzw. 6-koordinierte Strukturen für die Komplexe des TypsCpTi(S2CNHR)Cl2, bzw.CpTi(S2CNHR)2Cl angenommen werden. Die1H-NMR Spektren zeigen eine rasche Rotation des Cyclopentadienylrings um die Metall-Ring Achse an.
    Notes: Abstract Titanium(IV) dithiocarbamato complexes of the typesCpTi(S2CNHR)Cl2 andCpTi(S2CNHR)2Cl, whereR=C8H5N2S, C9H5N2SCl2 and C9H7N2S, have been prepared by the reaction of monocyclopentadienyl titanium(IV) trichloride with the potassium salt of the appropriate dithiocarbamic acid in anhydrous dichloromethane. Conductance and infrared studies indicate that these complexes are non-electrolytes in which all dithiocarbamate ligands are bidentate. Therefore, 5 and 6 coordinate structures can be assigned toCpTi(S2CNHR)Cl2 andCpTi(S2CNHR)2Cl complexes, respectively.1H-NMR spectra indicate that there is rapid rotation of the cyclopentadienyl ring about the metal ring axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798364
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  • 10
    Electronic Resource
    Electronic Resource
    Distributed optimistic concurrency control with reduced rollback (1987)
    Springer
    Distributed computing 2 (1987), S. 45-59 
    Details
    ISSN: 1432-0452
    Keywords: Database systems ; Concurrency ; Optimistic protocols ; Distributed algorithms ; Rollbacks ; Transactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Concurrency control algorithms have traditionally been based on locking and timestamp ordering mechanisms. Recently optimistic schemes have been proposed. In this paper a distributed, multi-version, optimistic concurrency control scheme is described which is particularly advantageous in a query-dominant environment. The drawbacks of the original optimistic concurrency control scheme, namely that inconsistent views may be seen by transactions (potentially causing unpredictable behavior) and that read-only transactions must be validated and may be rolled back, have been eliminated in the proposed algorithm. Read-only transactions execute in a completely asynchronous fashion and are therefore processed with very little overhead. Furthermore, the probability that read-write transactions are rolled back has been reduced by generalizing the validation algorithm. The effects of global transactions on local transaction processing are minimized. The algorithm is also free from dedlock and cascading rollback problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01786254
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