Showing papers by "Applied Science Private University published in 1995"

Promoting Active Learning with Cases and Instructional Modules

Abstract: In this paper, we propose the use of cases and instructional modules to teach invention, engineering design, and elements of technology management. One way to learn is to study and reflect upon the experience of others. Such experience may be captured in a case. Cases promote active learning by requiring students to assume the roles of participants in the decision making process. Cases are also a vehicle for raising business issues and human resources concerns not usually considered in traditional engineering courses. Real world design and engineering involves risk and uncertainty, tradeoffs and priorities, ethical issues, human elements, and impact assessment. Cases expose students to open ended, ill defined problems whose solution often depends on making assessments, judgments, and decisions about the technical competencies of the organization.

Fatigue behaviour of polymer composite sandwich beams

Abstract: The static and flexural fatigue characteristics of foam cored polymer composite sandwich beams are investigated. The skins of the beams are made from hybrid glass-aramid fibres set in epoxy resin and the core materials are linear and cross-linked polymer foams. The applied load in a ten-point configuration approximates a uniformly distributed load throughout the span of the beam which is simply supported at the ends. The testing frequencies are 0.33-0.91 Hz. Failure modes relate to both core shear and skin failure.

Teaching Invention and Design: Multi‐Disciplinary Learning Modules

Abstract: This paper outlines an approach to teaching invention and design that combines engineering, social sciences and humanities. We created an experimental course with a collaborative learning environment in which students from a wide range of majors worked in teams on modules, each of which lasted for several weeks and included strong written and oral components. Standard university curricula tend to compartmentalize engineering, humanities and social sciences. But real world engineering decisions defy such compartmentalization, as students discover when they take this course. Four active learning modules from the course are described in this paper: a hands-on project based on the invention of the telephone, a computer simulator to teach driving, an energy-efficient house and a medical decision support system based on a client's needs. A thorough evaluation of the course and modules is included, as are suggestions for future improvements.

An asymptotic analysis of the dispersion relation of a pre-stressed incompressible elastic plate

Abstract: This paper concerns an asymptotic analysis of the dispersion relation for wave propagation in a pre-stressed incompressible elastic plate. Asymptotic expansions for the wave speed as a function of wavenumber and pre-stress are obtained. These expansions have important potenatial applications to many dynamic problems such as impact problems. It is shown that in the large wavenumber limit the wave speed of the fundamental modes of both symmetric and anti-symmetric motions tends to the associated Rayleigh surface wave speed, on the other hand, the wave speeds of all the harmonics tend to a single limit which is the corresponding body wave speed. It is also shown that, whereas the fundamental modes are very sensitive to changes in the underlying pre-stress, the harmonics are little affected by such changes, espcially in the small and large wavenumber limits.

Studies on addition of inclusions to molten aluminum using a novel technique

Abstract: Considerable initiatives have often been taken to introduce specific solid particles directly into molten metals in a desirable quantity, but little success has been achieved, particularly in the case of reactive particles. Therefore, alternative routes such as production of solid particles through chemical reactions within the melt are often used. While these methods are capable of producing solid particles within the melt, the chemistry of the melt changes and control of particle size and chemistry is difficult. In the present study, a direct addition technique has been used to introduce many types of inclusions into liquid aluminum and Al-Si alloys, irrespective of their wettability and chemical reactivity, while preserving the surface characteristics and melt chemistry. A uniform particle distribution can be obtained even at low volume fraction of addition and with particle sizes of the order of 2 to 5 µm. This technique allows valuable information regarding the behavior of many inclusions, such as TiB2, TiC, SrO, and Sr(OH)2, in liquid aluminum to be studied. Several such examples are presented.

Sodium currents in toad cardiac pacemaker cells.

Abstract: Cells in the pacemaker region of toad (Bufo marinus) sinus venosus had spontaneous rhythmic action potentials. The rate of firing of action potentials, the rate of diastolic depolarization and the maximum rate of rise of action potentials were reduced by TTX (10 nm to 1 μm). Currents were recorded with the whole cell, tight seal technique from cells enzymatically dissociated from this region. Cells studied were identified as pacemaker cells by their characteristic morphology, spontaneous rhythmic action potential activity that could be blocked by cobalt but not by TTX and lack of inward rectification. When calcium, potassium and nonselective cation currents (If) activated by hyperpolarization were blocked, depolarization was seen to generate transient and persistent inward currents. Both were sodium currents: they were abolished by tetrodotoxin (10 to 100 nm), their reversal potential was close to the sodium equilibrium potential and their amplitude and reversal potential were influenced as expected for sodium currents when extracellular sodium ions were replaced with choline ions. The transient sodium current was activated at potentials more positive than −40 mV while the persistent sodium current was obvious at more negative potentials. It was concluded that, in toad pacemaker cells, TTX-sensitive sodium currents contributing both to the upstroke of action potentials and to diastolic depolarization may play an important role in setting heart rate.

Dynamics of Granular Matter

Abstract: Granular matter is a typical example of a new topic in statistical (phenomenology) mechanics. Reconsidering granular matter from the physical point of view, several new aspects have been clarified, although granular matter has been studied by engineers for a long (period of) time. This review examines three topics: (1) pattern dynamics of sand ripples and dunes, (2) mathematical structure of a fluidized bed, and (3) convection and turbulence in a vibrating bed. Investigating these topics, it is found that the dynamics of granular matter exhibits many typical nonlinear phenomena, for example, formations of pattern, localized states, and turbulence.

Saint-venantend effects for plane deformations of elastic composites

Abstract: SUMMARY In the linear theory of elasticity, Saint-Venant's principle is used to justify the neglect of edge effects when determining stresses in a body. For isotropic materials, the validity of this is well established. However, for anisotropic and composite materials, experimental results have shown that edge effects may persist much farther into the material than for isotropic materials and as a result cannot be neglected. This paper provides a further analysis of the effects of material anisotropy on the exponential decay rate for stresses in a semi-infinite elastic strip. A linearly elastic semi-infinite strip in a state of plane stress/strain subject to a self-equilibrated end load is considered first for a specially orthotropic material and then for the general anisotropic material. The problem is governed by a fourth-order elliptic partial differential equation with constant coefficients. In the former case just a single dimension-less material parameter appears, while in the latter, only three dim...

Evaluating Market-Oriented Water Policies in Jordan: A Comparative Study

Abstract: It is argued that the establishment of tradable water rights will play an important role in increasing productivity and sustainability of water use in developing countries. Due to economic growth, scarcity is expected to be conducive to water market development. This article presents the potential for and feasibility of markets in water rights in Jordan through a comparative study of Chile, Mexico, and California. Many lessons were learned from the experiences of those countries concerning water markets. The transformation of these lessons to the Jordanian context is faced with some fundamental challenges in terms of water legislation, institutional structure, and data. Water legislation must deal with externalities, dispute, and third-party effect. Adopting a new water act and review of water laws is essential for better water resources management and assured public input and feedback. Market oriented policy should be introduced only on a pilot basis in terms of pricing. Policy makers believe th...

Dependence of inter-edge-channel scattering on temperature and magnetic field: Insight into the edge-confining potential

Abstract: The inter-edge-channel equilibration length ${\mathit{L}}_{\mathrm{eq}}$ of a high-mobility two-dimensional electron gas in a GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterostructure is studied in the range of magnetic fields 2.8--4.5 T at temperatures of 0.5\ensuremath{\le}T\ensuremath{\le}11 K. The inverse of ${\mathit{L}}_{\mathrm{eq}}$ increases with increasing T at a magnetic field (3.4 T) corresponding to the center of the \ensuremath{ u}=4 Hall plateau, and rapidly decreases with increasing magnetic field B to depart from the center of the plateau. An analysis of these data in terms of impurity and phonon scatterings is attempted by assuming a parabolic-type confining potential. The observed T and B dependences are consistently analyzed if the inter-edge-state spacing \ensuremath{\Delta}X is assumed to be (i) much larger than the magnetic length ${\mathit{l}}_{\mathit{B}}$ (\ensuremath{\Delta}X=530 \AA{}, ${\mathit{l}}_{\mathit{B}}$\ensuremath{\sim}130 \AA{}) and (ii) kept nearly unchanged in the range of magnetic fields studied. That the size of \ensuremath{\Delta}X is nearly independent of B is an unexpected behavior, which disagrees also with recent self-consistent calculations of the edge-confining potential. The validity of the assumed parabolic-type confining potential is discussed.

Midinfrared modulation through the use of field-induced scattering in ferroelectric liquid crystals.

Abstract: The feasibility of the use of modulation devices based on field-induced transient scattering in ferroelectric liquid crystals (LC) to replace mechanical choppers used in uncooled infrared-imaging systems was investigated. Devices fabricated with ITO-coated ZnSe substrates and a ferroelectric LC path length of 25 μm were able to modulate optical radiation by transient forward scattering at rates approaching 20 kHz. Through the use of a commercial arbitrary waveform generator and associated PC-based software, drive waveforms were developed that produced a variable, square-wave optical-modulation pattern by the extension of the duration of the scattering state to periods ranging from hundreds of microseconds to milliseconds. The ability of these extended-scattering-mode (ESM) devices to modulate radiation in both the visible and midinfrared regions was verified in a simple experiment through the use of a Fourier-transform infrared spectrometer, in which an unoptimized ESM device displayed a 40% modulation depth for IR radiation in the 8–12-μm region.

A self‐adaptive fe system based on recursive spatial decomposition and multigrid analysis

Abstract: This paper introduces an automatic self-adaptive finite element system for 3-D stress analysis of homogeneous elastic solids described in a Solid Modelling System (SMS). This system reduces the role of the analyst into two basic tasks: defining the problem (i.e. geometry, material properties and boundary conditions) and specifying the desired accuracy in the analysis. The approach followed in this work is based on Recursive Spatial Decomposition (RSD) of solids defined in a SMS. The system includes procedures for meshing, analysis, error estimation, and adaptive remeshing and reanalysis. The various procedures share the same hierarchical data structure built on the RSD.

Effective Transfer of Computer Graphics to Video Format

Abstract: A course in computational fluid dynamics provides nearly unlimited opportunities for intensive use of computer graphics. Possibilities include in-class demonstrations of fundamental numerical principles and of various applications by the instructor, as well as use by students in homework assignments. In addition, graphical material on videotape is readily available from government and other laboratories. In this paper we report on the delivery of such a computer graphics-enhanced course live over television to students at multiple remote sites. Steps taken to enhance the presentation of computer graphics on television and to ease use by individual students at many widely scattered sites are reviewed in detail.

Chapter 15 Structural models of tetrahedrally bonded amorphous materials

Abstract: Publisher Summary This chapter focuses on the structural models of tetrahedrally bonded amorphous materials Amorphous silicon is a particularly interesting and important amorphous material It is the most promising material for a wide range of applications of solar energy conversion A fundamental understanding of the properties of these amorphous materials, whether electrical, optical, or mechanical, requires a detailed knowledge of their microscopic structure With the advent of realistic models of their structure, much effort has gone into calculations to elucidate these properties Starting with the structure for the perfect crystal, bond switches are made according to the usual Monte Carlo prescription The initial strain energy for the structure is zero When a single pair of bond switches is introduced into the otherwise perfect crystal, the strain energy given by the Keating potential is 45 eV Because the perfect crystal is the minimum energy, no trial bond switches will be accepted on a permanent basis except at a finite temperature The appropriate temperature can be determined by systematic trial After each bond-pair switch, the structure is relaxed to the geometrical configuration of minimum energy The number of shells over which to relax depends upon the expected range of energy differences between configurations During the initial randomization and the beginning stages of annealing, these differences are usually sufficiently large that energy differences can be calculated by using local relaxation over a single shell

Waves in Pre-Stressed Laminated Plates

Abstract: The problem of wave propagation and vibration of elastic plates and laminates has been an area of active research in recent years, although seemingly little attention has been focused on the effects of pre-stresses. The few contributions in this area have also restricted studies to single plates, see Ogden and Roxburgh [1], Roxburgh and Ogden [2] and Rogerson and Fu [3]. In this paper the dispersion relation associated with extensional waves propagating in a symmetric four-ply laminated plate subject to traction-free boundary conditions is derived. Each layer of the laminate is composed of a pre-stressed, incompressible elastic solid. The dispersion relation is both solved numerically and investigated analytically in the long and short wave limits.

Synthesis of MnAPO-20 and CoAPO-20 Using Tetrahedral Metal Species.

Abstract: High substitution levels of manganese and cobalt in MnAPO-20 and CoAPO-20 are achieved using tetrahedral metal species.