bluuebunny/crossref_metadata_2025 huggingface dataset:
Micro-Structures and Macro-Stresses in Sheared Granular Matter
Authors: Antony S. J. , Ghadiri M.
Published: May 2008

In this paper, the influence of large particles on the contact force net-work (structure) and their impact on the macroscopic shear resistance of a slowly sheared dense granular medium three dimensional) having a binary size distribution is presented. The evolution of deviator fabric tensor of the ‘strong’ and ‘weak’ contacts in the granular assembly is presented here. The ability of the granular material to establish a strongly anisotropic force net-work of strong contacts is ‘diluted’ by the presence of large particles during shearing. Previous studies [for example, Antony, S. J., 2001, Physical Review E, 63, 011302 and references there in] have shown that the shear strength of granular materials subjected to slow shearing depends on the ability of the material to built up a strongly anisotropic net work of contacts carrying strong (greater than average) contact normal force.
Design and Analysis of an Anthropometric Leg of the Humanoid Robot: Tyche
Authors: Yih T. C. , Shurpali Madhu V. , Apsangi Sandeep , Pemmaraju Sankar
Published: May 2008

This paper is concerned with the development of an anthropometric robotic leg for the humanoid robot, Tyche (Goddess of fortune). The design is based on physiology and anthropometry of human leg. The geometries of the links are finalized based on topological studies and avoidance of singularity condition. Fault tolerant design is incorporated in the design. A pantograph mechanism is used as the control device, which helps in magnifying the input. The kinematic and dynamic analyses are performed on the Tyche-leg. Five different cases are considered based on a cubic input motion profile. The kinematic and dynamic parameters are plotted with respect to time.
Discrete Characterization of Cohesion in Gas-Solid Flows
Authors: Jain Kunal , McCarthy J. J.
Published: May 2008

Cohesive forces between grains can arise from a variety of sources – such as liquid bridge (capillary) forces, van der Waals forces, or electrostatic forces – and may play a significant role in the processing of fine and/or moist powders. While recent advances have been made in our understanding of liquid-induced cohesion at the macroscopic level, in general, it is still not possible to directly connect this macroscopic understanding of cohesion with a microscopic picture of the particle properties and interaction forces. In fact, conventional theories make no attempt to distinguish between these modes of cohesion, despite clear qualitative differences (lubrication forces in wet systems or electrostatic repulsion are two good examples). In this work, we discuss several discrete characterization tools for wet (cohesive) granular material with simple, physically relevant interpretations. We examine the utility of these tools, both computationally and experimentally, by exploring a range of cohesive strengths (from cohesionless to cohesive) in several prototypical applications of solid and gas-solid flows.
Experimental Aspects of Shearing Granular Materials
Authors: Ding Yulong
Published: May 2008

Flow of granular materials has been a subject of numerous investigations in the past few decades. A number of experimental techniques have been used in these studies. Examples include PEPT (Positron Emission Particle Tracking), NMR (Nuclear Magnetic Resonance), HSP (High-Speed Photography), and various tomographic methods. These techniques have been used to study a number of model systems such as rotating drums, chute flows, vibro-beds, hopper flows, fluidised beds, and shear cells, in order to gain an insight into the behaviour of granular flows. In this paper, a brief review of these experimental techniques and model systems will be made first. Attention will then be paid to the work on rotating drums and fluidised beds using the non-invasive PEPT technique. Finally, future directions of the experimental aspects of shearing granular materials will be discussed.
Melting Behavior of In-Flight Particles and Its Effects on Splat Morphology in Plasma Spraying
Authors: Zhang H. , Xiong H. B. , Zheng L. L. , Vaidya A. , Li L. , Sampath S.
Published: May 2008

Effects of particle size, velocity, and temperature on the splat morphology have been well studied in the open literature. Effects of melt fraction on deposition efficiency and splat morphology are, however, not well understood. In this paper, we will focus on the melting behavior of in-flight particles and their impact on splat morphologies. A group parameter, “melting index”, has been derived to correlate the melting status of in-flight particles with particle size, velocity, and temperature which can be measured experimentally. Numerical simulations have been used to determine the unknown parameters in the melting index. The effects of initial particle diameter on the melting behavior have also been investigated.
Melting/Oxidation Behavior of In-Flight Particles in Plasma Spray Processes
Authors: Xiong H. , Zheng L. L. , Sampath S. , Fincke Jim
Published: May 2008

A comprehensive model describing the melting and oxidation of in-flight particles during plasma spray has been presented which includes the models for heat, momentum and mass transfer of carrier gas, and particle heating, acceleration and evaporation. The effect of evaporation-induced mass transfer on heat flux to the particle surface has been taken into consideration along with the effect of oxidation-induced evaporation due to the production of volatile oxides on the particle surface, and effects of variable plasma properties and non-continuum effects under plasma conditions. Computational results on molybdenum and zirconium particles in an argon-hydrogen DC plasma spray system have been obtained and discussed. The temperature and melting formation of particles with different sizes along their trajectories are depicted as well as other particle parameters such as velocity, evaporation rate and oxide content, which manifests that the behavior of particles are diverse due to particle size distribution in the spray coating operation. The effects of gun power on the heating, acceleration, melting, evaporation and oxidation of particles have also been discussed.
Design of Direct Methanol Micro Fuel Cell Fluidic Systems
Authors: Yao S. C. , Fedder G. K. , Amon C. H. , Hsieh C. C. , Tang X. , Alyousef Y.
Published: May 2008

Direct methanol micro fuel cells offer higher power density than advanced batteries. In this system, micro scale fluid handling becomes necessary. Designs of advanced microfluidic systems including micro valves, pumps and CO2 Gas bubble-Liquid separators, and flow channels are provided. MEMS-based special fabrication processes are utilized. Since all the fluidic components are fabricated with a common procedure, they are all fabricated together on the same silicon wafer at the same time. This assures the full fluidic system integration, which shall reduce the cost and enhance the reliability of the direct methanol micro fuel cell system.
Prediction of Heat Transfer Behavior of Carbide Inserts With Embedded Heat Pipes for Dry Machining
Authors: Chiou Richard Y. , Chen Jim S. J. , Lu Lin , Cole Ian
Published: May 2008

The temperature of a tool plays an important role in thermal distortion and the machined part’s dimensional accuracy, as well as in tool life in machining. The most significant factors in tool wear are temperature and the degree of chemical affinity between the tool and the workpiece. This research focuses on developing a clear understanding of the temperature distribution with cutting tool inserts embedded with heat pipes to eliminate the use of cutting fluids and reduce tool wealr in machining. A novel approach using the finite element analysis was developed to simulate the thermal behavior of a carbide cutting tool in three-dimensional dry machining. The carbide tools possess high material strengths at room temperature, but they cannot retain useful hardness at temperatures above 900°C (1700°F). Therefore, the reduction of tool wear typically requires maintaining the temperature of cutting tool inserts below some critical values. The particular temperature distribution depends on density, specific heat, thermal conductivity, shape and contact of the tool and heat pipe. Finite Element Analysis (FEA) shows that the temperature drops greatly at the tool-chip interface and that the heat flow to the tool is effectively removed when a heat pipe is embedded.
Development of a Telerobotic System to Assist Persons With Disabilities
Authors: Pernalete N. , Yu W. , Fritz B. , Dubey R.
Published: May 2008

This paper describes the development of intelligent mapping from a haptic user interface to a remote manipulator to assist individuals with disabilities performing manipulation tasks. This mapping, referred to an assistance function, is determined on the basis of environmental model or sensory data to guide the motion of a telerobotic manipulator while performing a given task. Human input is enhanced rather than superseded by the computer. Three manual dexterity assessment tests commonly used in occupational therapy field were chosen to implement several forms of assistance functions designed to augment the human performance. The test bed used for these tasks consisted of a six-degree-of-freedom force-reflecting haptic interface device, PHANToM with the GHOST SDK Software. One of the tests was chosen to be implemented in a real telerobotic system consisting of the haptic device as a Master and the Robotics Research Corporation manipulator (RRC K-2107) with a vision system and laser range data as a Slave. The results demonstrated that the forms of assistance provided reduced the execution times and increased the performance of the chosen tasks. In addition, these results suggest that the introduction of the haptic rendering capabilities, including the force feedback, offers special benefit to motion-impaired users by augmenting their performance on job-related tasks.
Cartesian Based Finite Volume Formulation for LES of Mixed Convection in a Vertical Turbulent Pipe Flow
Authors: Xu Xiaofeng , Lee Joon Sang , Pletcher R. H.
Published: May 2008

A numerical study was performed to investigate the effects of heating and buoyancy on the turbulent structures and transport in turbulent pipe flow. Isoflux wall boundary conditions with low and high heating were imposed. The compressible filtered Navier-Stokes equations were solved using a second order accurate finite volume method. Low Mach number preconditioning was used to enable the compressible code to work efficiently at low Mach numbers. A dynamic subgrid-scale stress model accounted for the subgrid-scale turbulence. The results showed that strong heating caused distortions of the flow structures resulting in reduction of turbulent intensities, shear stresses, and turbulent heat flux, particularly near the wall. The effect of heating was to raise the mean streamwise velocity in the central region and reduce the velocity near the wall resulting in velocity distributions that resembled laminar profiles for the high heating case.
Bidirectional Reflectance Measurement of Microstructural Silicon Surfaces
Authors: Zhu Qunzhi , Shen Yu-Jiun , Zhang Zhuomin M.
Published: May 2008

Knowledge of the bidirectional reflectance of silicon wafers is needed for the modeling prediction of the emitted and reflected radiation detected by radiometric thermometers, so that these instruments can be properly employed in industrial applications, such as rapid thermal processing chambers [1]. In a previous study [2], the bidirectional reflectance was observed to be sensitive to the surface roughness and coating configuration. For a typical silicon wafer, the surface could be polished, thin-film coated, randomly rough, or patterned. The characteristic parameters of the surface topography fall into the microscale or even nanoscale range. The present paper focuses on the bidirectional reflectance measurement of silicon wafers with thin-film coatings on their randomly rough sides. The reflectance distribution out of the incidence plane is also measured for the sake of a thorough characterization of surface scattering.
Advances in Computations of Air-Side Heat Transfer in Compact Heat Exchangers
Authors: Tafti D. K. , Cui J.
Published: May 2008

The paper describes the computed flow structure and heat transfer in flat tube corrugated multilouvered fin heat exchanger at the fin-tube junction. Three Reynolds numbers, 300, 600 and 1100 are calculated. The junction region is characterized by large flow velocities on the top surface of the fin and a “vortex jet” which develops under the bottom surface. Both of these are highly unsteady at Re = 1100. Their strength and unsteadiness decrease as the Reynolds number decreases. The large induced flow velocities in this region have a big impact on tube heat transfer, increasing it by a factor of 1.75 to 2. In spite of this augmentation, tube heat transfer coefficients are between 2.5 to 3 times smaller that those found on the louver, hence decreasing the overall heat transfer coefficient by 20–25%. Comparison of the modeled geometry with correlations derived from full core experiments show good agreement.
Convection Effects in Three-Dimensional Dendritic Growth
Authors: Lu Yili , Beckermann C. , Karma A.
Published: May 2008

A phase-field model is developed to simulate free dendritic growth coupled with fluid flow for a pure material in three dimensions. The preliminary results presented here illustrate the strong influence of convection on the three-dimensional (3D) dendrite growth morphology. The detailed knowledge of the flow and temperature fields in the melt around the dendrite from the simulations allows for a detailed understanding of the convection effects on dendritic growth.
Is There a Difference Between Dendrites of a Binary or a Ternary Alloy? Some Answers by Phase-Field Simulations
Authors: Diepers Hermann-J. , Eiken Janin , Steinbach Ingo
Published: May 2008

Dendritic growth is best understood for pure substances growing into a uniformly supercooled environment. Under certain assumptions the standard growth theory can be applied to the directional growth of dendrites in a binary alloy. To apply the theory to technical multicomponent alloys so called ‘binary equivalent’ or ‘pseudo-binary’ models have been proposed. The basic question of ‘Is there a difference between dendrites of a binary or ternary alloy?’ has only partially been answered. A phase-field model applied to a ternary Fe-C alloy with a third fictive component will be used in this paper to compare ternary and binary equivalent phase-field simulations focussing on different component diffusivities. Results for directional dendritic solidification indicate negligible and relevant differences with respect to micro-segregation and micro-structure.
A Unified Viscoplastic Fatigue Damage Model for 63Sn-37Pb Solder Alloy Under Cyclic Stress Control
Authors: Yang X. J. , Chow C. L. , Lau K. J.
Published: May 2008

A damage coupling viscoplastic model is developed to predict fatigue life of solder alloy 63Sn-37Pb under stress control. The viscoplastic flow rule chosen employs a hyperbolic sine function. A damage evolution equation is formulated based on three distinct material deformation behaviors: (i) stress rate independent damage evolution; (ii) stress rate dependent cyclic damage evolution; and (iii) stress rate dependent ductile damage evolution. The cyclic stress testing with different stress waveforms was first conducted to investigate their progressive viscoplastic deformations of the solder alloy. The investigation reveals that the material constants used in the model can be adequately determined from the results of standard creep tests. The constitutive model is validated by comparing the predicted and measured ratchetting results of the solder alloy under different forms of stress cycling. The proposed model is found to be capable of satisfactorily describing the viscoplastic deformation and ratchetting failure behaviors of the solder alloy under the conditions of the cyclic stress loading.
Front Tracking Method on a Fixed Grid versus Enthalpy Approach in Modelling of Binary Alloy Solidification
Authors: Browne David J. , Banaszek Jerzy , Hunt John D.
Published: May 2008

A novel front tracking technique on a fixed Cartesian grid, based on the kinetics of dendritic growth, is discussed. It is used to predict the influence of both alloy composition and convective heat transfer coefficient on the size of the undercooled liquid zone in front of columnar dendrite tips during solidification of Al-Cu alloys driven by conduction in a square mould. The model is compared with the enthalpy approach showing its superiority in the detection of the undercooled zone and, thus, in potentially modelling of columnar/equiaxed grain structures. The effect of natural thermal convection on the shape of the mushy zone is demonstrated by use of the enthalpy-porous medium model, and an approach to incorporating convection into the non-equilibrium front-tracking model is outlined.
Dynamic Performance of Shoe Centerless Grinding
Authors: Zhang Hong , Lieh Junghsen , Yen David
Published: May 2008

In this paper, the dynamic performance of shoe centerless grinding is presented. The model is a single-mass system in time and frequency domains. Based on the model, the stability and the critical parameters of the grinding process were studied. Numerical simulations were conducted in order to evaluate key parameters for the grinding process. The model was verified by experiments from real grinding trials.
Multiple Flow Patterns and Heat Transfer in Confined Jet Impingement
Authors: Li X. , Gaddis J. L. , Wang T.
Published: May 2008

The flow field of a 2-D laminar confined impinging slot jet is investigated. Numerical results indicate that there exist two different solutions in some range of geometric and flow parameters. The two steady flow patterns are obtained under identical boundary conditions but only with different initial flow fields. Three different exit boundary conditions are investigated to eliminate artificial effects. The different flow patterns are observed to significantly affect the heat transfer. A flow visualization experiment is carried out to verify the computational results and both flow patterns are observed. The bifurcation mechanism is interpreted and discussed.
On the Numerical Analysis of Different Controlling Parameters During the Solidification of Aluminum-Carbon Fiber Composite With Thermal Management
Authors: Amano R. S. , Lee E. K. , Rohatgi P. K. , Seong H. G. , Tiwari V. K.
Published: May 2008

Metal matrix composites (MMCs) consist of two or more distinct phases, namely a continuous metallic phase known as the matrix and a reinforcing phase. MMCs offer advantages over traditional monolithic materials of enhanced material properties such as strength, thermal/electrical conductivity, toughness, modulus of elasticity, wear resistance, etc. It is desirable to shorten the solidification time when producing MMCs because the higher the cooling rate, the finer the microstructures of the MMCs will be. The present research investigates MMCs processed in a novel way, in which the ends of the reinforcement phase are extended outside the liquid matrix envelope and cooled by a heat sink. By doing so, heat extraction in the axial direction greatly reduces the solidification time compared with conventional way of making MMCs. Due to the complicated geometry of the calculation domain, analytical result is very difficult to obtain. Therefore, attempts have been made to solve the energy equation by finite difference numerical method for a 2-D axis-symmetric model involving phase change. The calculation domain is based on the proposed experimental configuration by Rohatgi et al. [1]. In this paper, the effects of selected parameters which can influence the process of solidification are examined. These parameters include the volume fraction, the thermal conductivity of the reinforcing phase, and the heat sink temperature.
Calculation of Turbulent Boundary Layers Using Equilibrium Thermal Wakes
Authors: Sucec James
Published: May 2008

The combined thermal law of the wall and wake is used as the approximating sequence for the boundary layer temperature profile to solve an integral thermal energy equation for the local Stanton number distribution. The velocity profile in the turbulent boundary layer was taken to be the combined law of the wall and wake of Coles. This allows the solution of an integral form of the x-momentum equation, to give the skin friction coefficient distribution. This, along with the velocity profile is used to solve the thermal energy equation using inner coordinates. The strength of the thermal wake was found by analysis of earlier research results, in the literature, for equilibrium, constant property, turbulent boundary layers. Solutions for the Stanton number distribution with position are found for some adverse pressure gradient boundary layers as well as for zero pressure gradient ones. The zero pressure gradient results cover both fully heated plates and those with unheated starting lengths, including both isothermal surfaces and constant flux surfaces. Comparison of predictions of the present work is made with experimental data in the literature.
Nusselt Number Behavior on Deep Dimpled Surfaces Within a Channel
Authors: Burgess N. K. , Oliveira M. M. , Ligrani P. M.
Published: May 2008

Experimental results, measured on a dimpled test surface placed on one wall of a channel, are given for a ratio of air inlet stagnation temperature to surface temperature of approximately 0.94, and Reynolds numbers from 12,000 to 70,000. These data include friction factors, local Nusselt numbers, spatially-resolved local Nusselt numbers, and globally-averaged Nusselt numbers. The ratio of dimple depth to dimple print diameter δ/D is 0.3, and the ratio of channel height to dimple print diameter is 1.00. These results are compared to measurements from other investigations with different ratios of dimple depth to dimple print diameter δ/D to provide information on the influences of dimple depth. At all Reynolds numbers considered, local and spatially-resolved Nusselt number augmentations increase as dimple depth increases (and all other experimental and geometric parameters are held approximately constant). These are attributed to: (i) increases in the strengths and intensity of vortices and associated secondary flows ejected from the dimples, as well as (ii) increases in the magnitudes of three-dimensional turbulence production and turbulence transport. The effects of these phenomena are especially apparent in local Nusselt number ratio distributions measured just inside of the dimples, and just downstream of the downstream edges of the dimples.
Probability Analysis of Motor Vehicle Accidents
Authors: Kimbrough Scott
Published: May 2008

Probability analysis is the key to extracting the maximum information from the evidence surrounding a motor vehicle accident. Moreover, it gives essential perspective to the answers drawn from the evidence, by conveying the uncertainty about the answers. In this paper, probability methods are used to analyze a typical intersection type collision between two vehicles. It is a situation in which one of the vehicles pulls out from a stop sign into the path of the other vehicle, which had the right of way. The vehicle that pulls out into the path of the oncoming vehicle precipitates the accident, but the driver of the oncoming vehicle may have contributed to the accident by traveling at excessive speed and or by being inattentive.
A Wind-Tunnel Study of Thermally Stratified Boundary Layers
Authors: Cataldi Marcio , Loureiro Juliana B. R. , Silva Freire Atila P.
Published: May 2008

The objective of this work is to develop, in a wind tunnel environment, boundary layers with different states of development that simulate the structure present in the atmospheric boundary layer. The work analyses the dymamic and thermal characteristics of different types of thick, artificially-generated, turbulent boundary layers. The thermal boundary layer is obtained by two methods: wall surface heating, made through electrical resistance, can furnish an increase in wall temperature of up to 100 °C above the ambient temparatures and can be applied over a 5000 mm long surface with a controlled variation of 2 °C. The main flow heating is obtained by forcing the flow pass through an array of copper wires whose elements can be heated individually. The main flow can be heated up to 100 °C. The whole system can then be used to produce unstable, neutral and stable boundary layers. The parameters of the thermal boundary layers are qualified according to the following parameters: growth, structure, equilibrium, turbulent transport of heat and energy spectrum. The paper describes in detail the experimental arrangements, including the geometry of the wind tunnel and the instrumentation.
Hybrid Analysis of Laminar Thermally Developing Flow With Axial Diffusion Effects
Authors: Castro Ana Cristina R. , Neto Francesco Scofano , Guedes Rodrigo Otavio C.
Published: May 2008

This contribution addresses the internal forced convection problem in a circular duct including axial fluid conduction effects. The problem is modeled by taking under consideration the “two-region” model which avoids the prescription of the inlet temperature profile. The mathematical formulation is handled by the Generalized Integral Transform Technique. The results are focused on the axial distribution of bulk and wall temperatures and Nusselt numbers over a range of suitable Peclet and external Biot numbers.
Modeling of Anisotropic Damage for Ductile Materials in Metal Forming Processes
Authors: Hammi Youssef , Horstemeyer Mark F. , Bammann Doug J.
Published: May 2008

The primary goal of this study is to model the anisotropic effect of ductile damage in metal forming processes. To represent the ductile metals, an anisotropic ductile plasticity/damage formulation is considered within the framework of continuum mechanics. The formulation is motivated from fracture mechanisms and physical observations in Al-Si-Mg aluminum alloys with second phases. The ductile damage mechanisms are represented by the classical ductile process of nucleation of voids at inclusions, followed by their growth and coalescence. Functions of each mechanism evolution are related to different microstructural parameters. The damage, represented by a second rank tensor, is coupled to the Bammann-Chiesa-Johnson (BCJ) rate-dependent plasticity using the effective stress concept. The constitutive equations are integrated using a fully implicit scheme and implemented into a explicit finite element code. This implementation is used to predict damage during the forward axisymmetric extrusion of an aluminum bar. This example illustrates the applicability of the model to predict the initiation and the evolution of anisotropic damage in metal forming processes.
Manufacturability of Large SMT Connectors
Authors: Serafin Stacey N. , Dishongh Terrance
Published: May 2008

With the advent of higher signaling frequencies on today’s motherboard, evolution suggests that the electronic industry is near a phase transition of going from through hole mount to surface mount connectors. Current computer infrastructure supports assembly of motherboards using through hole mount connectors from a historical standpoint. This legacy has led placement equipment manufacturers to develop fabrication machines that do not consider long, thin devices such as a PCI or DIMM connector. The reassessment of the world’s method of motherboard manufacturing presents a challenge. Hence the question arises, what is the realistic lifetime of a through hole mount connector and what are the assembly and reliability issues associated with a proposed replacement such as a surface mount connector. This paper addresses the basic reliability concerns of a long, thin, surface mount PCI connector both with, and without retention features.
Effect of Voids on Thermal Fatigue Reliability of Lead-Free Solder Joints
Authors: Yu Qiang , Kim Do-Seop , Shibutani Tadahiro , Inoue Toshiaki , Sadakata Nobuyuki
Published: May 2008

There have been serious debates about whether Pb should be removed from solder joints, in view of environmental problems. These debates have now developed to the extent that a remarkable movement to establish regulations for the removal of Pb has emerged, especially in European countries and Japan. Therefore, many studies are aggressively being undertaken to develop technologies for replacing Sn-Pb solder with a lead-free alternative. From the results obtained so far, it has been proven that the fatigue strength in lead-free solder joints is almost equivalent to the fatigue strength of Sn-Pb eutectic solder joints. However, the other problem is that voids are easily formed in lead-free solder joints during the reflow process, and the effects of void formation on the fatigue strength of solder joints has attracted attention. In this study, the relationship between formation of voids and fatigue fracture mode and fatigue strength of solder joints was examined using FEM (finite element method) analysis and mechanical shear fatigue test. From the results of FEM analysis, it has been found that the equivalent plastic strain and shear strain of solder joints with voids are not always larger than those of solder joints without voids and the magnitude of the strains relate to the position and size of voids in solder joints. However, the difference of the strains is not so great as to affect the fatigue strength of solder joints. It has also been proven from the mechanical shear fatigue test that the fatigue fracture mode of solder joints with voids is similar to that of solder joints without voids and fatigue strength in both cases is also almost equivalent.
A Transient Technique for Calibrating Thermochromic Liquid Crystals: The Effects of Surface Preparation, Lighting and Overheat
Authors: Bakrania Smitesh , Anderson Ann M.
Published: May 2008

This paper describes a transient technique for thermochromic liquid crystal hue-temperature calibration and presents results on the effects of surface preparation, lighting and overheat on that calibration. An image acquisition system and calibration test plate were designed for transient measurement and are described. The transient calibration results compare well to steady state calibration results for cooling and heating rates of 0.03 °C/s. Hysteresis occurred when the surface was heated above the play range of the crystals but was not permanent. We found that a poorly prepared liquid crystal surface yielded a “steep” calibration curve, was subject to light ‘warm up’ effects and the hysteresis effect was severe upon overheating.
An Interfacial Debonding Model for Particle-Reinforced Composites
Authors: Liu H. T. , Sun L. Z. , Ju J. W.
Published: May 2008

To simulate the evolution process of interfacial debonding between particle and matrix, and to further estimate its effect on the overall elastic behavior of particle-reinforced composites, a two-level microstructural-effective damaged model is developed. The microstructural damage mechanism is governed by the interfacial debonding of reinforcement and matrix. The progressive damage process is represented by the debonding angles that are dependent on the external loads. For those debonded particles, the elastic equivalency is constructed in terms of the stiffness tensor. Namely, the isotropic yet debonded particles are replaced by the orthotropic perfect particles. The volume fraction evolution of debonded particles is characterized by the Weibull’s statistical approach. Mori-Tanaka’s method is utilized to determine the effective stiffness tensor of the resultant multi-phase composites. The proposed constitutive framework is developed under the general three-dimensional loading condition. Examples are conducted to demonstrate the capability of the proposed model.
A Path-Planning Strategy for Overhead Cranes With High Hoisting Speed
Authors: Lee Ho-Hoon
Published: May 2008

This paper proposes a path planning strategy for high-performance anti-swing control of overhead cranes, where the anti-swing control problem is solved as a kinematic problem. First, two anti-swing control laws, one for hoisting up and the other for hoisting down, are proposed based on the Lyapunov stability theorem. Then a new path-planning strategy is proposed based on the concept of minimum-time control and the proposed anti-swing control laws. The proposed path planning is free from the usual constraints of small load swing, slow hoisting speed, and small hoisting distance. The effectiveness of the proposed path planning is shown by computer simulation with high hoisting speed and hoisting ratio.
Managing Energy Engineering Education: The Introductory Course
Authors: Fanchi John R.
Published: May 2008

Future energy engineers will need to understand a range of diverse energy initiatives. The purpose of this paper is to present a plan for developing an Energy Engineering course for undergraduates. The course will introduce students to the concepts needed to understand the 21st century energy mix, and should help tomorrow’s leaders understand their role as stewards of the earth’s natural resources.
Evolution of a Modern Energy Company
Authors: Brown Roberta S.
Published: May 2008

The mergers and acquisitions currently taking place in the energy industry are often thought to be new to our times but are actually part of an on-going process common in the energy industry since its inception. The paper traces the evolution of Conectiv, a current mid-Atlantic supplier of energy and energy delivery company, from its foundations over 100 years ago as Wilmington Coal Gas Company and Electric Light Company of Atlantic City through dozens of mergers, acquisitions and divestitures, with products as diverse as electricity, gas, ice, trolleys, trains, steam, cooling, appliances, telephone service, and even the Internet. The impact of technological advances, both within the power industry and in society, as well as major historical events such as the Great Depression or World War II, will be highlighted.
A Thermodynamic Study of the Thermal Performance of Free Piston Stirling Prime Movers
Authors: Rogdakis E. D. , Bormpilas N. A. , Koniakos I. K.
Published: May 2008

Linear dynamics theory adequately describes the behavior of Free Piston Stirling Engines (FPSEs). The aim of this paper is to predict the conditions for stable operation of FPSEs and the modeling of FPSEs. The linearization technique of the dynamic balance equations proposed recently by F. de Monte and G. Benvenuto has been applied using RE-1000 of Sunpower Inc. for a typical well known FPSE. The equations of motion are solved analytically in terms of the stiffness and damping coefficients of the machine. Using the criterion of the stable engine cyclic steady operation a rigorous mathematical form is obtained for the main parameters of the engine. The proposed model gives results close to the data coming from the literature and can be used to predict the thermal performance, the piston stroke and the delivered power. Furthermore, using for reasons of simplicity Schmidt Analysis (Isothermal model) the indicated output power is obtained. In addition, a reference is given to some of the most important thermal losses in the engine decreasing the theoretical performance up to experimental level.
Experimental Performance of Natural Convection of a Semitransparent Wall With Film Coating of a Cubic Enclosure Using Infrared Imaging
Authors: Flores J. J. , Alvarez G.
Published: May 2008

This paper presents an experimental heat transfer study of the exterior side of a semitransparent wall (window) with film coating of a enclosure. The absorptance of the semitransparent wall with film coating was simulated using a film resistance on the glazing. A technique of infrared imagining thermography and a traversing system developed in Lawrence Berkeley National Laboratories (LBNL) were extended to measured from 1-D to 2-D local surface temperatures and boundary layer air temperatures of the exterior a glazing. From those measurements, the exterior heat flow and the exterior local convective heat transfer coefficients were calculated by applying a technique proposed by Truler [1]. The 2-D surface temperature distributions, the local convective heat transfer coefficient distributions and the average Nusselt number of the exterior side of the semitransparent wall with a simulated absorptance of 0.5 are presented.
Teaching of Thermodynamics: Innovation in Design for ABET
Authors: O¨zer Arnas A.
Published: May 2008

In this paper the methodologies by which thermodynamic theory can be developed to permit design of experiments are discussed. This approach is both innovative in itself and pedagogically sound in that the student learns to design while learning the important theoretical topics. This technique uses mathematical as well as engineering concepts that are relatively simple and yet very educational. The equipment to be used and the details of the design then become the designer’s choice and are limited only by the person’s own imagination, creativity, and innovative thinking and the physical laboratory resources available at a given institution. This methodology shows what is to be measured and what kind of results are to be expected. Since design is incorporated into this thermodynamics course, then it can be assessed for its design content as well as engineering science coverage in the ABET 2000 evaluations.
Thermodynamic Optimization of Flow Architecture: Dendritic Structures and Optimal Sizes of Components
Authors: Bejan A. , Lorente S.
Published: May 2008

This paper reports two new advances on constructal design, or the generation of flow architecture in the pursuit of global thermodynamic performance subject to constraints. This is thermodynamic optimization with an emphasis on its product: flow geometry, as a mechanism for the achievement of performance under constraints. The first part of the paper relies on this principle in the design of dendritic (tree-shaped) networks that distribute a stream optimally from one source to a disc-shaped area for which the source is the center. One global objective is (i) the minimization of source-area flow resistance, which, when the overall flow rate is fixed, is the same as the minimization of the destruction of exergy. The alternative (ii) is to design the flow architecture such that the flow path followed by each stream is the shortest. Optimal dendritic flow architectures are reported based on both methods. It is shown that the performance of designs (ii) is nearly the same as that of the optimal designs (i). Examples of dendritic patterns of high-conductivity blades used for cooling a disc-shaped body show that the overall thermal resistance of the construct decreases as the size and complexity of the flow architecture increase. The same principle of maximizing global performance can be used to select the optimal sizes of flow components in all complex energy flow systems (e.g., vehicles, animals). The size of a heat transfer surface and the diameter of a tube with fluid are given as examples.
Future Trends in Sensed-Information Technology and Sensor Systems Research
Authors: Flatau Alison , Varshney Usha , Chang Peter
Published: May 2008

Advances in MEMs, wireless, information technology and other enabling technologies are leading to new sensor system functionality and access to more accurate data and information than heretofore realizable. These advances are crucial for realizing the full potential of the on-going transition from data-poor to data-rich and information-poor to information-rich science and engineering practices. With decreases in size and cost of sensors resulting from advances in microsystem technologies, ubiquitous sensing is becoming both physically realizable and economically feasible. New developments in sensed-information technologies offer the promise of novel insights and advances in areas that have previously lacked the technology base for acquiring high resolution and highly specific assessments of state (biologic, chemical, physical, optical, etc.). Increased research and education are needed in new technologies addressing research issues relating to new hardware and software for efficient acquisition of data and information, and in new decision and control theory as tools for managing and using available data and information. New sensor system functionality will be realized through countless different design concepts. This paper examines some of the needs, opportunities, and trends for research and education in the area of sensed-information and sensor systems research.
Thermoeconomic Analysis of a Cogeneration System of Compression Ignition Engine and Absorption Refrigeration Machine
Authors: Cruz Ricardo Wilson , Nebra Silvia Azucena
Published: May 2008

This paper is a first attempt to evaluate a refrigeration with cogeneration system focusing on a 915 kW genset/90 ton aqua-ammonia absorption system capable of supplying refrigeration, e.g. for cold storage warehouses for food conservation in the Northern Brazilian autonomous grid. The first and second law joined formulation, i.e. exergy, is used in order to determine irreversibilities and to address the exergetic and monetary costs of the system.
Thermoeconomic Diagnosis: Zooming Strategy Applied to Highly Complex Energy Systems: Part 1 — Detection and Localization of Anomalies
Authors: Verda Vittorio , Serra Luis , Valero Antonio
Published: May 2008

This paper presents a summary of our most recent advances in Thermoeconomic Diagnosis, developed during the last three years [1–3], and how they can be integrated in a zooming strategy oriented towards the operational diagnosis of complex systems. In fact, this paper can be considered a continuation of the work presented at the International Conference ECOS’99 [4–6] in which the concepts of malfunction (intrinsic and induced) and dysfunction [7] were analyzed in detail. These concepts greatly facilitate and simplify the analysis, the understanding and the quantification of how the presence of an anomaly, or malfunction, affects the behavior of the other plant devices and of the whole system. However, what remains unresolved is the so-called inverse problem of diagnosing [3], i.e. given two states of the plant (actual and reference operating conditions), find the causes of deviation of the actual conditions with respect to the reference conditions. The present paper tackles this problem and describes significant advances in addressing how to locate the actual causes of malfunctions, based on the application of procedures for filtering induced effects that hide the real causes of degradation. In this paper a progressive zooming thermoeconomic diagnosis procedure, which allows one to concentrate the analysis in an ever more specific zone is described and applied to a combined cycle. In an accompanying paper (part 2 [8]) the accuracy of the diagnosis results is discussed, depending on choice of the thermoeconomic model.
Feasibility Analysis and Computer Simulation of an Automated Bus Route
Authors: Solomon J. H. , Gonzalez-Mohino P. , Amirouche F. , Zavattero D.
Published: May 2008

Traffic congestion in major cities is a major problem which is growing steadily every year. It is clear that something must be done to curb this trend. Several different concepts are being investigated which can be used to minimize congestion and improve the traffic flow. Automation of the bus system represents one of those methods, and is the focus of this paper. Currently, public opinion of the quality of bus services is generally not perceived as adequate. Buses generally travel about 60% of the speed of other vehicles, and more often than not adherence to schedule is difficult to achieve. The consequence is that people choose to take personal transportation instead, causing increased congestion. Automation seeks to address this issue by offering decreased travel times, increased schedule adherence, and greater overall convenience compared to the current bus systems. The concept of automation is based on expanding upon the ideas of Bus Rapid Transit (BRT) and making the system as efficient as possible.
Cost Structure of CGAM Cogeneration System
Authors: Kwak Ho-Young , Byun Gi-Taek , Kwon Yong-Ho , Yang Hyup
Published: May 2008

The cost structure of the CGAM system, a predefined cogeneration system suggested to unify the different methodologies of thermoeconomic analysis, was investigated by using a thermoeconomic method called MOPSA (Modified Productive Structure Analysis). An emphasis has been specially put on how the cost structure of the system is affected by the chosen level of aggregation that specifies the subsystems. It has been found that the unit cost of products is dependent on the chosen level of aggregation of the system only when one consider the negentropy flow as one of the parameters to determine the unit cost of products.
Self-Contained Intelligent Sensor-Actuator for Temperature Control
Authors: Al-Jumaily A. M. , Kadhum H.
Published: May 2008

Some electrically conductive polymer composites show positive temperature coefficient behavior during one temperature range followed by negative temperature coefficient behavior during the next range. The change normally occurs at a well-defined switching temperature. This paper proposes to use this phenomenon to develop an intelligent sensor-actuator device suited for temperature control applications. Two conductive composites were prepared and their switching temperatures were determined experimentally. Then a heated tube was made, with one of these composites as the heating element, and tested for the sensing-actuation control action. The results are very promising for future development of a wide range of such devices.
Experimental Study of Bubble Dynamics and Concentration Variation in the Presence of Boron in the Liquid
Authors: Jia W. , Dhir V. K.
Published: May 2008

Accumulation of neutron absorber (boron or boron compounds) within the porous crud layer on the fuel rods in the cores of pressured water reactors (PWR) results in the so-called axial offset anomaly (AOA). There is practically little information on the gradients of neutron absorber concentration near a nucleation site on the cladding surface during the growth of a bubble. The objective of the present work is to study bubble dynamics and associated concentration field of aqueous boron. As a first step in solving the complete problem, dynamics of single bubble was studied under pool boiling conditions. Distilled water and an aqueous solution containing 3,000ppm by weight of boric acid were used as test liquids. Single bubble was generated at a micro-fabricated cavity on a polished silicon wafer. It was found that the growth and departure processes of single bubbles are similar for both the test liquids. A miniature sensor for measurement of concentration was developed and calibrated. Concentration variation near the liquid-vapor interface was detected successfully. The measured concentration variations at different radial locations from the center of cavity have the same trend as given by the numerical simulations but the magnitude is much smaller.