Showing papers by "Stevens Institute of Technology published in 1980"

Linear stability of Poiseuille flow in a circular pipe

Abstract: Correction of an error in the matrix elements used by Salwen & Grosch (1972) has brought the results of the matrix-eigenvalue calculation of the linear stability of Hagen–Poiseuille flow into complete agreement with the numerical integration results of Lessen, Sadler & Liu (1968) for azimuthal index n = 1. The n = 0 results were unaffected by the error and the effect of the error for n > 1 is smaller than for n = 1. The new calculations confirm the conclusion that the flow is stable to infinitesimal disturbances.Further calculations have led to the discovery of a degeneracy at Reynolds number R = 61·452 ± 0·003 and wavenumber α = 0·9874 ± 0·0001, where the second and third eigenmodes have equal complex wave speeds. The variation of wave speed for these two modes has been studied in the vicinity of the degeneracy and shows similarities to the behaviour near the degeneracies found by Cotton and Salwen (see Cotton 1977) for rotating Hagen-Poiseuille flow. Finally, new results are given for n = 10 and 30; the n = 1 results are extended to R = 106; and new results are presented for the variation of the wave speed with αR at high Reynolds number. The high-R results confirm both Burridge & Drazin's (1969) slow-mode approximation and more recent fast-mode results of Burridge.

Components for optical communications systems: A review

Abstract: Current trends in research and development of components for optical communication are reviewed. Emphasis is placed on active components for fiber-optic systems which have undergone recent major advances. Basic properties of optical fibers and recent technological improvements in splices, connectors, and source/detector-fiber couplers are presented first. This background information serves as a basis for describing recent developments in optical sources (e.g., device reliability, LED's and laser diodes) and photodetectors. Developments in both the 0.8-0.9-µm and 1.0-1.7-µm wavelength regions are covered. Also surveyed are results of research in areas of potential interest for optical communications: novel fiber-optic components, integrated optics (sources and modulators/switches), novel device fabrication methods, and integration of optical components.

Abinitio effective core potentials including relativistic effects. V. SCF calculations with ω–ω coupling including results for Au2+, TlH, PbS, and PbSe

Abstract: Ab initio self‐consistent field calculations are reported for a series of diatomic molecules using relativistic effective core potentials (REP) and basis sets appropriate for ω–ω coupling. The molecular orbitals are expressed as linear combinations of two‐component analogs of Dirac spinors. The unique feature of the present approach is the retention of the spin–orbit operator in the generation of the REP’s and the propagation of its effects into the molecular wave functions in a totally consistent fashion. The nature of bonding in the molecules Au2+, TlH, PbSe, and PbS is discussed with consideration of the orbital energies, spectroscopic constants, and population analyses. Comparisons with recently obtained photoelectron spectra of PbSe and PbS are made. It is noted that 6p1/2 and 6p3/2 orbitals exhibits bonding characteristics that are different from the nonrelativistic pσ and pπ molecular orbitals.

Solutions of the Iteration Equation and Extensions of the Scalar Iteration Operation

Abstract: We study the solutions to a (vector) equation somewhat analogous to the traditional equations of linear algebra. Whereas, in introductory linear algebra the domain of discourse is the field of real numbers (or an arbitrary field) our domain of discourse is the algebraic theory of (multi-rooted, leaf-labeled) trees (or, more generally, any iterative theory).

Internal structure of electron-beam filaments

Abstract: Electron beams of tW/${\mathrm{cm}}^{2}$ (\ensuremath{\sim}0.4 MeV) which are split into filaments are produced by an inductive generator which transfers field energy to beam particles in 1-10-ns pulses. Target-damage analysis reveals the composite internal structure of each filament as a sequence of concentric circles with a discontinuous pattern. The nonuniform distribution of collectively accelerated positive ions within a filament contributes to resolve the filament structure which propagates at a speed $\ensuremath{\sim}\frac{3c}{4}$ and can cross unaffected a ${10}^{3}$-G magnetic field.

Vector Iteration in Pointed Iterative Theories

Abstract: This paper is a sequel to a previous paper S. L. Bloom, C. C. Elgot and J. B. Wright, Solutions of the iteration equation and extensions of the scalar iteration operations, SIAM J. Comput., 9 (1980), pp. 25–45. In that paper it was proved that for each morphism ⊥: 1 → 0 in an iterative theory J there is exactly one extension of the scalar iteration operation in J to all scalar morphisms such that \( I_1^{ + } = \bot \) and all scalar iterative identities remain valid. In this paper the scalar iteration operation in the pointed iterative theory (J, ⊥) is extended to vector morphisms while preserving all the old identities.

The effects of basis set quality and configuration mixing in ab initio calculations of the ionization potentials of the nitrogen molecule

Abstract: Systematic configuration interaction calculations of the adiabatic ionization potentials of N2(1Σg+) to the X 2Σg+, A 2Πu and B 2Σu+ states of N2+ give best results of 15.62, 16.41, and 18.93 eV compared with observed values of 15.576, 16.694, and 18.746 eV. The computed values are near the complete basis limit for a wave function containing single and double excitations from the Hartree–Fock configuration with the Langhoff–Davidson correction for unlinked cluster quadruple excitations. The critical dependence of ionization potentials on basis is demonstrated. Vertical ionization potentials at near the N2 ground state equilibrium internuclear separation are compared for a variety of basis sets using different computational methods. In particular, an important comparison is made with the EOM calculation of Herman, Yeager, Freed, and McKoy using a ’’double‐zeta+polarization’’ basis identical to one used in this study. We conclude that agreement to within ∼0.2 eV can be expected for ionization potentials bet...

Simulation of reactive injection molding

Abstract: This paper deals with the computer simulation of those aspects of Reactive Injection Molding (RIM) dealing with the non-isothermal and transient flow of a chemically reacting mixture into a mold cavity, and the in situ polymerization (“curing”) which follows mold filling. Linear polyurethane systems were considered. The purpose of this simulation work is to investigate the effects of the operating, chemical, and rheological variables on the length and the stability of the RIM process, as well as the quality of the resulting product. Since the flowing fluid mixture is reactive, there is a need to know the thermal history of each of the flowing fluid particles. For this reason the “fountain” flow at the fluid-air interface is considered in a heuristic fashion.

Structure vs stability in polymer degradation

Abstract: All materials are subject to aging, a process of long-term degradation, but not at the same rate or affected in the same manner. The wide variation in susceptibility (or resistance) of polymers to various degradative agents, e.g., oxidative, thermal, mechanical, chemical, biological, depend on their chemical composition and structure. Accordingly, the chemical, physical, and energy considerations inherent in the pure polymer are discussed in relation to degradative stability.

Steady pressure flow relations in compressed arteries: possible origin of Korotkoff sounds.

Abstract: Anin vivo preparation is described in which the compressed artery under an occlusive blood pressure cuff is shown to possess a dynamic negative-resistance characteristic. In this situation the pressure drop along a segment of artery decreases despite an increase in flow. Such characteristics have been previously observed only inin vitro preparations. Under the appropriate conditions this characteristic permits self-excited and sustained oscillation (relaxations oscillations) of the intraluminal pressure and flow to occur. A plausible model in which the origin of Korotkoff sounds is linked to such self-excited oscillations is described.

Cross-sections and scaling variable distributions of neutral and charged current neutrino nucleon interactions from a low-energy narrow band beam

Abstract: This Letter compares neutral-current and charged-current scaling-variable distributions in neutrino-nucleon interactions induced by a narrow-band beam at Brookhaven National Laboratory; the $x$ distribution of neutral-current events has been reported previously. The first measurement of flux-normalized neutrino cross sections from a narrow-band beam in the energy range ${E}_{\ensuremath{ u}}=3\ensuremath{-}9$ GeV is also presented.

Asymmetric Permeators—A Conceptual Study

Abstract: The asymmetric permeator concept of Ohno et. al. utilizing two different membranes for rare gas separation has been explored in general. Various geometrical arrangements and possible applications to gas separations other than rare gas-nitrogen mixtures have been discussed. The utility of an asymmetric permeator for multicomponent gas separations has been investigated. The separation factor of a ternary system in a perfectly mixed asymmetric permeator has been obtained. The amount of separation obtained with a ternary feed in a perfect crossflow stage having no axial mixing has been analytically determined for some limiting cases with an asymmetric permeator. The asymmetric permeator concept has been extended also to a high separation factor liquid solution separation process like reverse osmosis desalination. Preliminary calculations have been carried out to show that an asymmetric desalinator with reverse osmosis (RO) and piezodialysis (PD) membranes has a lower increase in brine concentration a...

Polymer devolatilization: Theory of equipment

Abstract: The role of surface renewal and feedback phenomena in devolatilization equipment is clearly illustrated via staged models. A continuous model for the vented, single-screw devolatilizer is developed, including barrel evaporation and bulk surface renewal as well as backmixing, which represents de-volatilization data more accurately than previous models. Numerous sample computations are included. The models are used to demonstrate the sensitivity of devolatilization equipment to certain design parameters.

Reactive polymer processing

Abstract: This paper addresses some of the general engineering problems in reactive polymer processing: thermal effects on reactor stability and polymer properties due to rapid exothermic polymerization, the formulation of reaction viscosity relationships required in simulations, and the generation of flow and mixing via technology available from both ends of the viscosity spectrum, which is spanned in its entirety when going from monomer to molded polymer. Methods of analysis are discussed and general design concepts are suggested, which can be applied to the construction of innovative future processing equipment.

New derivations of the quadrupole formulas and balance equations for gravitationally bound systems

Abstract: A new derivation of the quadrupole formulas and balance equations of general relativity for gravitationally bound systems is given which overcomes objections raised to previous derivations.

Modeling Chemosensory Responses of Swimming Eukaryotes

Abstract: The application of biased random walk and diffusion types of models to chemosen-sory responses of populations of swimming eukaryotes is described. Three general types of models and their physiological bases are discussed. The distinction between steady-state and transient solutions, and the importance of various time scales in the experiments to be modeled are emphasized. Experiments with Paramecium, Tetrahymena and Crypthecodinium are discussed in this context.

Re-evaluation of the planing hull form

Abstract: This paper defines the planing hull form, presents a brief historical evolution of the craft, summarizes the recently develpoed technology and its impact upon design and application, and, finally, discusses the potential of the craft. The authors demonstrate the inappropriateness of stereotyping planing craft as small underpowered boats which must struggle to "get over the hump" and then subject the structure and personnel to severe pounding, wetness, and discomfort when operating in a seaway. It is shown that, by appropriate application of recently developed technology, planing forms have evolved which are devoid of "hump" problems, demonstrate excellent behavior in a seaway, have substantially useful load fractions, and have a potential growth up to displacements of nearly 1000 tons.

Realizability of p‐point graphs with prescribed minimum degree, maximum degree, and line connectivity

Abstract: It is well known that certain graph-theoretic extremal questions play a central role in the study of communication network vulnerability. Herein we consider a generalization of some of the classical results in this area. We define a (p, Δ, δ, λ) graph as a graph having p points, maximum degree Δ, minimum degree Δ, and line connectivity λ. An arbitrary quadruple of integers (a, b, c, d) is called (p, Δ, δ, λ) realizable if there is a (p, Δ, δ, λ) graph with p = a, Δ = b, Δ = c, and λ = d. Necessary and sufficient conditions for a quadruple to be (p, Δ, δ, λ) realizable are derived.