Showing papers by "Stevens Institute of Technology published in 1995"

An examination of the effects of an upward feedback program over time

Abstract: Despite the growing popularity of upward feedback programs, there has been very little research on the effects of upward feedback on changes in managerial performance over time. We examined the effects of implementing an upward feedback program in which subordinates' ratings were collected for 238 first-through fifth-level managers in a large corporation at two points in time about 6 months apart. Research questions drawn from goal-setting, control, and social cognition theories guided our investigation of the effects of (a) receiving feedback, (b) completing self-ratings, (c) managers' initial level of performance, and (d) subordinate's familiarity with the manager on changes over time in the level of ratings and reported opportunity to observe managerial behaviors. Ratings were provided on a 33-item behavioral observation scale that focused on areas such as the manager's commitment to quality, communications, support of subordinates (encouraging participation, coaching), and fairness. Based on subordinates' ratings, managers whose initial level of performance was moderate or low improved over the 6-month period, and this improvement could not be attributed solely to regression to the mean. Also, both managers and their subordinates became more likely over time to indicate that the managers had an opportunity to demonstrate behaviors measured by the upward feedback instrument.

Study of grain growth in electrodeposited nanocrystalline nickel-1.2 wt.% phosphorus alloy

Abstract: The paper describes a transmission electron microscope study of the microstructural evolution of electrodeposited nanocrystalline Ni-1.2wt%P and pure nickel during heating experiments performed in situ. The grain structure of the Ni-1.2wt.%P alloy was found to be stable up to a temperature of 360 °C. The grain growth was concurrent with Ni3P precipitation, suggesting the important role of phosphorus in supersaturated solid solution in imparting the thermal stability to the microstructure. Normal grain growth was observed in Ni-1.2wt.%P at annealing temperatures up to 480 °C. Subsequent analysis revealed pinning of grain boundaries by Ni3P precipitates. The value of activation energy for grain growth in Ni-P alloy (2.25 eV), obtained from continuous scan rate DSC experiments, is consistent with the above observation. Electrodeposited nanocrystalline nickel, on the other hand, showed abnormal grain growth at temperatures as low as 260 °C. At 320 °C, the microstructure had largely transformed from the nanocrystalline to the microcrystalline state.

Mechanisms of mixing in single and co-rotating twin screw extruders

Abstract: Previous experimental studies have revealed that the mixing efficiencies of widely used continuous processors such as the single and twin screw extruders depend on the types of screw elements, which are utilized. It is generally recognized that the basic single screw extruder and the fully-fighted sections of the fully-intermeshing co-rotating twin screw extruders are not efficient mixers, in contrast to the specialized mixing elements such as the kneading discs used in co-rotating twin screw extruders. However, no simulation techniques were available to characterize quantitatively and rigorously the mixing efficiencies of continuous processors. In this study, we have solved the three-dimensional equations of conservation of mass and momentum, and utilized various tools of dynamics to analyze the mixing occurring in single and co-rotating twin screw extruders. It is shown that simulation methods can indeed capture the relative differences in the mixing mechanisms of continuous processors like the single and twin screw extruders. The ability to distinguish quantitatively between the distributive mixing capabilities of various continuous processors should facilitate numerical testing of new continuous mixer designs, optimization of operating conditions and geometries of existing mixers and the material-specific design of new mixers.

Tribology of diamond-like carbon sliding against itself, silicon nitride, and steel

Abstract: Diamond-like carbon (DLC) films were deposited on (100) silicon wafers and silicon nitride balls by RF plasma-assisted chemical vapor deposition at a pressure of 700 mTorr and a substrate temperature of 360 K. The friction coefficient and the wear rates were measured using a pin-on-disk tribometer in 40% humid and dry air. Friction coefficients are near 0.05 in all cases measured. In dry air, the wear of silicon nitride and steel against DLC is below measurement capability because of a protecting DLC transfer layer, and wear of DLC is 2.5 ± 10−8 mm3/Nm against silicon nitride and 6.5 ± 10−9 mm3/Nm against steel. In humid air, the DLC transfer layer does not adhere to the solids, and wear of both bodies is larger. Unmeasurable wear is obtained when DLC slides against itself in humid air; the wear rate is 5 ± 10−9 mm3/Nm in dry air. These results are interpreted in terms of the properties of a friction-induced transformation of the surface layer of DLC.

GEMNET: a generalized, shuffle-exchange-based, regular, scalable, modular, multihop, WDM lightwave network

Abstract: GEMNET is a generalization of shuffle-exchange networks and it can represent a family of network structures (including ShuffleNet and de Bruijn graph) for an arbitrary number of nodes. GEMNET employs a regular interconnection graph with highly desirable properties such as small nodal degree, simple routing, small diameter, and growth capability (viz. scalability). GEMNET can serve as a logical (virtual), packet-switched, multihop topology which can be employed for constructing the next generation of lightwave networks using wavelength-division multiplexing (WDM). Various properties of GEMNET are studied. >

Innovation, market structure and firm size: A simultaneous equations model

Abstract: This study uses a hwequation model and data for four-digit SIC manufacturing industries to examine the joint endogeneily of output measures of innovation activity and market structure (industry concentration). Its results confirm recent studies finding high concentration to have a negative effect on innovation output (especially smabfinn innovations), and Anding that large-firm innovations and small-finn innovations respond Werently to economic and technological conditions. The study also reveals that, contrary to some previous research, and consistent with modern ‘Schumpeterian’ propositions, innovation output (especially largefirm innovations) has a significant positive effect on industry concentration.

Multiparticle dynamics in an expanding universe.

Abstract: Approximate equations of motion for multiparticle systems in an expanding Einstein-deSitter universe are derived from the Einstein-Maxwell field equations using the Einstein-Infeld-Hoffmann surface integral method. At the Newtonian level of approximation one finds that, in comoving coordinates, both the Newtonian gravitational and Coulomb interactions in these equations are multiplied by the inverse third power of the scale factor $R(t)$ appearing in the Einstein-deSitter field and they acquire a cosmic "drag" term. Nevertheless, both the period and luminosity size of bound two-body systems whose period is small compared to the Hubble time are found to be independent of $t$.

Wavelets and perfect reconstruction subband coding with causal stable IIR filters

Abstract: We show for the first time that it is possible to have a large family of perfect reconstruction subband coding filter banks, which are causal and IIR both at the analysis and at the synthesis ends. Complete parametrization of such classes of filters leading to design methods are given. Parametrizations in frequency domain terms as well as in terms of state space descriptions of filters are provided for better numerical implementation of design methods. The development is valid for two-band as well as for multiband subband coding schemes. The iterated filter banks are shown to give rise to a new family of biorthogonal version of continuous wavelets, the scaled and dilated version of which represents arbitrary square integrable signals. Dilation factors larger than two are implicit in the development resulting from the fact that we consider multiband subband coding schemes. >

Simulation of intensity of segregation distributions using three-dimensional fem analysis: Application to corotating twin screw extrusion processing

Abstract: The corotating twin screw extrusion flow is simulated to generate the distributions of intensity of segregation and integral measures of mixing and forwarding. The simulation focused on the lenticular kneading disk elements that necessitated the application of a three-dimensional finite element method to solve the conservation equations. The intensity of segregation distributions were determined by introducing a tracer blob numerically and tracking the concentration of the tracer particles as a function of location and time. In spite of the chaotic nature of the dynamics of this flow, the analyses provided the broad features of twin extrusion flow and its ability to mix. The processing characteristics of kneading disks were found to depend on the stagger angle and complemented earlier numerical and experimental results on residence time distributions and color incorporated tracer analyses. © 1995 John Wiley & Sons, Inc.

Optical switch configuration and lightpath assignment in wavelength routing multihop lightwave networks

Abstract: A wide-area transparent optical network can be constructed by using wavelength routers and switches, each dealing with only a small number of wavelengths. In this work we consider the problem of configuring the wavelength routers based on the observed traffic. Various policies for wavelength routing, and the corresponding assignment of wavelengths along the routes have been studied before, which are based on minimizing congestion, average hop-distance, and call blocking probability or on maximizing carried traffic, and the number of clear channels. However these approaches often lead to scenarios where a significant number of available wavelengths at the input/output ports of the routers cannot be used due to potential wavelength conflict. The wavelength routing and assignment algorithms presented in this paper focus on maximizing the wavelength-utilization at the switching devices which also improve the overall network performance.

A Shrinking Lemma for Indexed Languages

Abstract: This article presents a combinatorial result on indexed languages which was inspired by an attempt to understand the structure of groups with indexed language word problem. We show that a sufficiently long word in an indexed language can be written as a product of a uniformly bounded number of terms in such a way that some proper subproduct belongs to the language.

Numerical Study of Forced Convection in a Partially Porous Channel With Discrete Heat Sources

Abstract: A numerical study was performed to analyze steady laminar forced convection in a channel partially filled with a fluid-saturated porous medium and containing discrete heat sources on the bottom wall. Hydrodynamic and heat transfer results are reported for the configuration in which the porous layers are located above the heat sources while the rest of the channel is nonporous. The flow in the porous medium was modeled using the Brinkman-Forchheimer extended Darcy model. Parametric studies were conducted to evaluate the effects of variable heat source spacing and heat source width on heat transfer enhancement and pressure drop in the channel. The results indicate that when the heat source spacing was increased within the range considered, there was a negligible change in heat transfer enhancement while the pressure drop decreased significantly. When the heat source width was decreased, there was a moderate increase in heat transfer enhancement and a significant decrease in pressure drop.

Thermoplastic composites from maleic anhydride modified post-consumer plastics

Abstract: In attempts to identify potential applications for refined commingled postconsumer plastics, a feedstock containing about 80% polyethylene (PE) and lesser amounts of poly(ethylene terephthalate) (PET), polystyrene (PS), polypropylene (PP), and poly(vinyl chloride) (PVC) was modified through functionalization with maleic anhydride in a co-rotating intermeshing twin-screw extruder. The modified and unmodified blends were compounded with various fillers and reinforcements such as glass fibers, mica flakes, talc, and calcium carbonate. Injection molded composites based on the modified matrix had, in general, superior mechanical and thermal properties. These findings are discussed in view of the improved adhesion resulting from reactions and/or enhanced polar interactions at phase boundaries. Several compounds prepared in this work had overall property data comparable to, or approaching those, of equivalent commercial HDPE molding compounds that are commonly used in “durable” applications.

Conditions for synchronization in Josephson-junction arrays.

Abstract: An effective perturbation theoretical method has been developed to study the dynamics of Josephson-junction series arrays. It is shown that the inclusion of junction capacitances, which is often ignored, has a significant impact on synchronization. Comparison of analytic with computational results over a wide range of parameters shows excellent agreement.

Induced-dichroism-excited atomic line filter at 532 nm.

Abstract: The operation of a narrow-linewidth optical filter based on the 4P1/2 → 8S1/2 excited-state transition in potassium vapor is reported. The 4P1/2 state is excited by a circularly polarized, 769.9-nm, 10-ns pulse from a dye laser. A linearly polarized, time-sequenced, and spatially overlapped probe pulse at 532.33 nm completes the transition to the 8S1/2 state. The peak filter transmission is ~40% with a bandwidth of less than 4 GHz. Corroborative experimental results suggest that the rotation of probe-pulse polarization by an induced circular birefringence is the dominant mechanism behind the filter operation.

Multiphase ozonolysis of organics in wastewater by a novel membrane reactor

Abstract: Conventional ozonation of recalcitrant organic compounds in wastewater suffers from low transfer rate of ozone into water. The low transfer rate can be enhanced by adding an inert fluorocarbon (FC) liquid immiscible with water but having a much higher solubility for ozone. A novel membrane reactor was studied for the destruction of organic pollutants by using PC liquid simultaneously as a reaction medium and a liquid membrane. The membrane reactor consisted of two sets of microporous and/or non-porous hollow-fiber membranes well-mixed in a cylindrical shell filled with the inert FC liquid. Wastewater was allowed to flow through the lumen of one set of microporous fibers; O3-containing gas flowed through the bore of the other set. Oxidative degradation products get partitioned back into the two mobile phases. Degradation of such pollutants as phenol, acrylonitrile, nitrobenzene, trichloroethylene, and toluene in such a reactor is presented. The kinetics of degradation of each pollutant in the two-phase (aqueous- FC) system were studied using batch and semibatch experiments. Simulation results based on a first-order model to predict the behavior of pollutant degradation in such a membrane reactor are compared with experimental data.

Method and apparatus for dual modulation laser spectroscopy

Abstract: A method and apparatus for conducting laser absorption spectroscopy uses a frequency tunable laser aligned to pass a laser beam through a sample volume and to an optical detector. A two-step modulation is used to generate frequency components that may be used to both lock the tunable laser to the absorbance signal, and generate an output signal proportional to the absorbance signal. The method includes frequency modulating the tunable laser at a first frequency while further modulating the tunable laser with a triangular waveform having a second frequency, and generating a feedback control signal based upon an antisymmetrical signal demodulated from the optical detector using a first predetermined harmonic of the second frequency. The tunable laser is locked to the absorbance signal with the feedback control signal. An output signal proportional to the absorbance signal is generated using a symmetrical signal demodulated using a second predetermined harmonic of the second or triangular waveform frequency. The first and second predetermined harmonics are preferably consecutive harmonics.

1 – introduction to materials science and engineering

Abstract: This introductory chapter has attempted to dramatize the role of materials within broader historical and societal contexts, as well as within engineering and manufacturing activities. Several concentric levels of connections conveniently serve to define the impact of materials. Most broadly, materialsenergy-environment concerns address the wider community, whereas materials-design-processing constraints are more narrowly limited to engineering and manufacturing issues. Processing-structure-properties-performance interactions are the most focused of all and refer to specific materials. At the core of the subject is the structure—properties scientific base. Enveloping the core are the engineering concerns of processing and performance. For millennia, processing and performance of engineering solids were what mattered, and because the former was an art, the latter was very variable in practice. Now structure-property relationships are recognized as the key to understanding the fundamental nature of materials, improving their properties, and creating new materials.

Optimal Bounds Correlating Electric, Magnetic and Thermal Properties of Two-Phase, Two-Dimensional Composites

Abstract: The effective conductivity function of a two-phase two-dimensional composite is known to be a tensor valued analytic function of the component conductivities, assumed here to be isotropic. Optimal bounds correlating the values this function can take are derived. These values may correspond to the measured effective magnetic permeabilities, thermal conductivities, or any other transport coefficient mathematically equivalent to the effective conductivity. The main tool in this derivation is a new fractional linear transformation which maps the appropriate class of conductivity functions passing through a given point to a similar class of functions which are not subject to the restriction of passing through a known point. Crude bounds on this class of functions give rise to sharp bounds on the original class of effective conductivity functions. These bounds are the best possible, being attained by sequentially layered laminate microgeometries.

A new model for optimal routing in all-optical networks with scalable number of wavelength converters

Abstract: A novel approach for modeling the optimal routing and wavelength assignment problem in wavelength division multiplexed all-optical networks is proposed. It is assumed that the optical switching nodes are equipped with a limited and scalable set of wavelength converters which can be used by any subset of incoming optical-connections. The proposed model, called the interconnected-layered-graph, provides an exact solution of the optimal routing and wavelength assignment problem in wavelength convertible networks with arbitrary number of wavelength converters at each node. A dynamic routing and wavelength assignment scheme, which is based on the proposed interconnected-layered-graph model, is also presented and it is evaluated for various network configurations.

Video dialtone technology: digital video over ADSL, HFC, FTTC, and ATM

Abstract: The age of digital video service drivers and markets regulatory aspects a primer on TV and cable technology video dialtone transport and signalling architecture digital video compression digital video servers ATM and ATM switches terrestrial/guided distribution systems - ADSL, HFC, FTTC other distribution systems the new TV set and the setup box the players - telephone carriers moving to video, cable TV moving to telephony.

Laboratory studies of air stripping of VOC‐contaminated soils

Abstract: Bench‐scale laboratory experiments were conducted to evaluate the effectiveness of air stripping for in situ remediation of benzene‐contaminated soils. Several parametric studies were performed to evaluate the effect of soil grain size, air injection flow rate, and air inlet temperature on the benzene recovery efficiency. An increase in soil grain size produced a significant increase in benzene recovery efficiency especially during the early stages of air injection. After 2 h of treatment, an increase in soil grain size from D50 = 0.31 mm to D50 = 1.20 mm resulted in an increase in benzene recovery efficiency from 49 to 65%. When the air‐flow rate was increased from 5 l/min to 10 l/min, the benzene recovery efficiency increased from 56 to 70% after 4 h of venting operation. Maximum recovery of benzene was reached after approximately 37 h of soil venting at a flow rate of 5 l/min and after approximately 24 h at a flow rate of 10 l/min. Preheating the air to 45°C at the inlet resulted in an increas...