bluuebunny/crossref_metadata_2025 huggingface dataset:
Condensate Retention Effects on the Performance of Plain-Fin-and-Tube Heat Exchangers: Retention Data and Modeling
Authors: Korte C. , Jacobi A. M.
Published: July 2002

A study of condensate retention is presented for plain-fin-and-tube heat exchangers typical to those used in air-cooling applications. An experiment in which the retained mass of air-side condensate was measured under dynamic conditions is described, and the results are analyzed using conventional thermal-hydraulic measurements of j and f. With the coupling between condensate retention and thermal performance established, a new model for predicting the mass of retained condensate is described and compared to the steady-state retention data. The model is successful in predicting retained condensate under relatively restricted conditions. The promise of this new approach, and possible refinements that will add engineering value are discussed.
Experimentation on the Residual Stresses Generated by Endmilling
Authors: Jacobus Kurt , Kapoor S. G. , DeVor R. E.
Published: July 2002

Residual stress measurements from endmilling of annealed AISI 4340 have been made at multiple points within the cut geometry to investigate the effects of location on the machining-induced residual stresses from endmilling. In the same experiments the effects of axial depth of cut and feed on the residual stresses induced in the machined surface have been investigated in a design of experiments framework. The experimentation demonstrates that location, feed and axial depth of cut have strong influences on the machining-induced residual stresses from end-milling when expressed in a workpiece coordinate frame. In addition, expression of the residual stresses in a coordinate frame fixed in the tool demonstrates a simplification in the residual stresses from endmilling in that the stresses at multiple locations within the cut geometry show strong similarities when expressed in this coordinate frame.
Micromachined Particle Filter With Low Power Dissipation
Authors: Yang Joon Mo , Ho Chih-Ming , Yang Xing , Tai Yu-Chong
Published: July 2002

Microfilters for collecting micron-size airborne biological agents are designed and fabricated using a micro-electro-mechanical-system (MEMS) fabrication technology. The thickness of the microfilter ranges from 1 μm–3 μm, and the hole diameter from 5 μm–12 μm. Iterations between experimental and numerical studies are carried out to attain efficient microfilter designs with low pressure drop. Two orders of magnitude reduction of viscous power consumption have been achieved. A design rule of the filter in a low Reynolds-number range was first derived from numerical simulations. Highly accurate measurements of the three-dimensional (3-D) geometry, side-wall profile, and diameter of the micron-size holes are critical in validating and modifying the design rule. The effect of the surface slip is found to be small in the tested Knudsen-number range.
Thermomechanical Analysis of Solder Joints Under Thermal and Vibrational Loading
Authors: Basaran Cemal , Chandaroy Rumpa
Published: July 2002

Due to the coefficient of thermal expansion (CTE) mismatch between the bonded layers, the solder joint experiences cycling shear strain, which leads to short cycle fatigue. When semiconductor devices are used in a vibrating environment, additional strains shorten the fatigue life of a solder joint. Reliability of these joints in new packages is determined by laboratory tests. In order to use the FEM to replace these expensive reliability tests a unified constitutive model for Pb40/Sn60 solder joints has been developed and implemented in a thermo-viscoplastic-dynamic finite element procedure. The model incorporates thermal-elastic-viscoplastic and damage capabilities in a unified manner. The constitutive model has been verified extensively against laboratory test data. The finite element procedure was used for coupled thermo-viscoplastic-dynamic analyses for fatigue life predictions. The results indicate that using Miner’s rule to calculate accumulative damage by means of two separate analyses, namely dynamic and thermo-mechanical, significantly underestimates the accumulative total damage. It is also shown that a simultaneous application of thermal and dynamic loads significantly shortens the fatigue life of the solder joint. In the microelectronic packaging industry it is common practice to ignore the contribution of vibrations to short cycle fatigue life predictions. The results of this study indicate that damage induced in the solder joints by vibrations have to be included in fatigue life predictions to accurately estimate their reliability.
Creep Analysis of Wafer Level Chip Scale Package (WLCSP) With 96.5Sn-3.5Ag and 100In Lead-Free Solder Joints and Microvia Build-Up Printed Circuit Board
Authors: Lau John H. , Pan Stephen H. , Chang Chris
Published: July 2002

In this study, time-temperature-dependent nonlinear analyses of lead-free solder bumped wafer level chip scale package (WLCSP) on printed circuit board (PCB) assemblies subjected to thermal cycling conditions are presented. Two different lead-free solder alloys are considered, namely, 96.5wt percent Sn-3.5wt percent Ag and 100wt percent In. The 62wt percent Sn-36wt percent Pb-2wt percent Ag solder alloy is also considered to establish a baseline. All of these solder alloys are assumed to obey the Garofalo-Arrhenius steady-state creep constitutive law. The shear stress and shear creep strain hysteresis loops, shear stress history, and shear creep strain history at the corner solder joint are presented for a better understanding of the thermal-mechanical behaviors of lead-free solder bumped WLCSP on PCB assemblies. Also, the effects of microvia build-up PCB on the WLCSP Solder joint reliability are investigated.
An Infinite Dimensional Distributed Base Controller for Regulation of Flexible Robot Arms
Authors: Jalili Nader
Published: July 2002

An exponentially stable variable structure controller is presented for regulation of the angular displacement of a one-link flexible robot arm, while simultaneously stabilizing vibration transient in the arm. By properly selecting the sliding hyperplane, the governing equations which form a nonhomogenous boundary value problem are converted to homogenous ones, and hence, analytically solvable. The controller is then designed based on the original infinite dimensional distributed system which, in turn, removes some disadvantages associated with the truncated-model-base controllers. Utilizing only the arm base angular position and tip deflection measurements, an on-line perturbation estimation routine is introduced to overcome the measurement imperfections and ever-present unmodeled dynamics. Depending on the composition of the controller, some favorable features appear such as elimination of control spillovers, controller convergence at finite time, suppression of residual oscillations and simplicity of the control implementation. Numerical simulations along with experimental results are provided to demonstrate and validate the effectiveness of the proposed controller.
Identification of Wiener Systems With Known Noninvertible Nonlinearities1
Authors: Lacy Seth L. , Erwin R. Scott , Bernstein Dennis S.
Published: July 2002

In this paper we develop a method for identifying SISO Wiener-type nonlinear systems, that is, systems consisting of a linear dynamic system followed by a static nonlinearity. Unlike previous techniques developed for Wiener system identification, our approach allows the identification of systems with nonlinearities that are known but not necessarily invertible, continuous, differentiable, or analytic.
Biorthogonal Wavelet Based Identification of Fast Linear Time-Varying Systems—Part I: System Representations12
Authors: Zhao Haipeng , Bentsman Joseph
Published: July 2002

An analytical framework is developed that permits the input-output representations of discrete-time linear time-varying (LTV) systems in terms of biorthogonal bases on compact time intervals. Using these representations, the companion paper, Part II develops computational procedures for rapid identification of fast nonsmooth LTV systems based on short data records. One of the representations proposed is also used in H. Zhao and J. Bentsman, “Block Diagram Reduction of the Interconnected Linear Time-Varying Systems in the Time Frequency Domain,” accepted for publication by Multidimensional Systems and Signal Processing to form system interconnections, or wavelet networks, and develop subsystem connectibility conditions and reduction rules. Under the assumption that the inputs and the outputs of the plants considered in the present work belong to lp spaces, where p=2 or p=∞, their impulse responses are shown to belong to Banach spaces. Further on, by demonstrating that the set of all bounded-input bounded-output (BIBO) stable discrete-time LTV systems is a Banach space, the system representation problem is shown to be reducible to the linear approximation problem in the Banach space setting, with the approximation errors converging to zero as the number of terms in the representation increases. Three types of LTV system representation, based on the input-side, the output-side, and the input-output transformations, are developed and the suitability of each representation for matching a particular type of the LTV system behavior is indicated.
Identification of a Driver Steering Model, and Model Uncertainty, From Driving Simulator Data
Authors: Chen Liang-Kuang , Ulsoy A. Galip
Published: July 2002

For active safety systems that function while the driver is still in the control loop, driver uncertainty can affect system performance significantly. In this paper, an approach to obtain both the driver model and its uncertainty from driving simulator data is presented. The structured uncertainty is used to represent the driver’s time-varying behavior, and the unstructured uncertainty for unmodeled dynamics. The uncertainty models can represent both the uncertainty within one driver and the uncertainty across multiple drivers. The structured uncertainty suggests that an estimation and adaptation scheme might be applicable for the design of controllers for active safety systems.
An Update on Heat Transfer in a Porous Insulation Medium in a Subsea Bundled Pipeline
Authors: Zheng Gary , Verret Allen , Burke Nancy , Prescott Neal , Cai Dennis , Perera Ravi
Published: July 2002

At the Multiphase ’99 Conference in Cannes, France, the authors presented a simple, yet general, formulation for effective conductivity of a porous insulation medium under pipeline application using fundamental continuity, momentum, and energy equations Zheng et al., 1999, “Heat Transfer in a Porous Insulation Medium in a Subsea Bundled Pipeline,” Paper No. 48 presented at Multiphase ’99, Cannes, France, ©BRH Group 1999. The effective conductivity was shown as a function of Darcy-modified Raleigh number only. The coefficients in the equation were then obtained from a set of tests for a simple pipe-in-pipe bundle with half-shell pieces of foam fitted around the inner pipe. Dramatic heat losses as experienced in some of field applications were recorded when the porous insulation foam is under high nitrogen pressure. All the heat losses were attributed to the increased heat convection within the porous insulation medium. Recognizing loose spaces between half-shells may contribute to the dramatic heat losses, the authors from R. J. Brown Deepwater conducted a new set of tests that used the same open-cell foam material, but with foamed-in-place application on the inner pipe wall. The new test data are used in this paper to derive an updated set of coefficients for the effective conductivity formulation. It is shown that such a foamed-in-place open-cell foam system maintains insulation effectiveness, even under high application pressures.
A historical survey of some mathematical aspects of Newtonian fluid flows
Authors: Zeytounian RKh
Published: July 2002

This article deals with a survey of the Newtonian fluid dynamics equations with some historical notes and a discussion related to the solvability of fluid flows problems. On the way, we discuss briefly various questions related with the behavior of fluid flows governed by these fluid dynamics equations. Some of these questions are, in fact, closely connected with the well-posedness of fluid dynamics problems. We touch on the problem of the fluid dynamics limit of the Boltzmann equation of the kinetic theory of gases. An overview of some rigorous recent results on the existence and uniqueness of solutions of the fluid flows problems concludes this paper. At the end, after some concluding remarks, there are 306 references.
Micro and Macro Deformation of Single Crystal NiTi
Authors: Gall Ken , Dunn Martin L. , Liu Yiping , Labossiere Paul , Sehitoglu Huseyin , Chumlyakov Yuriy I.
Published: July 2002

We present experimental results on the instrumented Vickers micro-indentation and compression of solutionized Ni-rich NiTi single crystals. The tests are conducted at room temperature where the solutionized Ti-50.9 at percent Ni material is 18 degrees above Af and the solutionized Ti-51.5 at percent Ni material is more than 100 degrees above Af. Aside from elastic deformation, it is discovered that dislocation motion and a reversible stress-induced martensitic transformation influence the micro-indentation response of Ti-50.9 at percent Ni, while the micro-indentation of Ti-51.5 at percent Ni only induces irreversible dislocation motion. The effect of the surface normal orientation on material hardness was negligible in the Ti-51.5 at percent Ni and followed trends anticipated by the activation of favorable slip systems in the Ti-50.9 at percent Ni. Compression tests on the identical Ti-50.9 at percent Ni samples revealed deformation by coupled stress-induced martensite and plastic flow, depending on the crystallographic orientation. The trends in hardness with surface normal orientation were not commensurate with the orientation dependence of the uniaxial compressive transformation or “yield” strength. The ramifications of the results in terms of comparing micro-indentation and macro-compression and the interactions between plasticity and the stress-induced martensitic transformation are discussed.
Present State of Numerical Ship Hydrodynamics and Validation Experiments
Authors: Gorski Joseph J.
Published: July 2002

This paper gives a perspective on the current state of computational and experimental ship hydrodynamics, which has experienced significant progress and rapid change recently. In particular, with the use of more powerful computers and parallel computations, Reynolds Averaged Navier-Stokes (RANS) calculations are more feasible for support of design studies. Some of the areas where RANS computations are being used for surface ships are demonstrated and an attempt is made to provide an indication of where the naval community is at in its ability to accurately predict some of these complex flow phenomenon. Concurrently, there have been efforts to obtain high quality experimental data for validating the computational tools. Such efforts have sought to obtain detailed flow field and wave height data in addition to conventional force data. This detailed information can be used to help quantify how accurately the flow physics can be predicted and begins to allow for a more formal verification and validation of the computations.
A Systematic Method for Kinematics Synthesis of High-Speed Mechanisms With Optimally Integrated Smart Materials
Authors: Rastegar J. , Yuan L.
Published: July 2002

A systematic method is presented for kinematics synthesis of high-speed mechanisms with optimally integrated smart materials based actuators for the purpose of modifying the output link motion. As an example, the method is applied to a four-bar linkage mechanism that is synthesized for function generation to eliminate the high harmonic component of the output link motion. For mechanisms with rigid links, the high harmonic motions are generated due to the nonlinearity of the kinematics of their closed-loop chains. By eliminating the high harmonic component of the output motion, the potential vibrational excitation that the mechanism can impart on the overall system and its own structure is greatly reduced. The resulting system should therefore be capable of operating at higher speeds and with greater precision. A numerical example is provided together with a discussion of the application of the method to other mechanism synthesis problems and some related topics of interest.
The Precise Measurement of Free-Form Surfaces1
Authors: Wolovich William , Albakri Hassan , Yalcin Hulya
Published: July 2002

We outline a new procedure for measuring free-form curves and surfaces using implicit polynomial equations. Such equations have long been known to offer certain advantages over the more traditional parametric methods. However, the lack of general procedures for obtaining implicit polynomial models of higher degree, which precisely represent arbitrary 3-D shapes, have prevented their general use in many practical applications, including rapid and precise metrology. Recent mathematical advances obtained at Brown University, experimentally verified using a state-of-the-art Chameleon coordinate measuring machine, have demonstrated potential advantages of implicit methods for modeling and measuring a variety of manufactured objects.
Recent Progress in Reducing the Uncertainty in and Improving Pyranometer Calibrations
Authors: Myers Daryl R. , Stoffel Thomas L. , Reda Ibrahim , Wilcox Stephen M. , Andreas Afshin M.
Published: July 2002

The Measurements and Instrumentation Team within the Distributed Energy Resources Center at the National Renewable Energy Laboratory, NREL, calibrates pyranometers for outdoor testing solar energy conversion systems. The team also supports climate change research programs. These activities led NREL to improve pyranometer calibrations. Low thermal-offset radiometers measuring the sky diffuse component of the reference solar irradiance removes bias errors on the order of 20 Watts per square meter (W/m2) in the calibration reference irradiance. Zenith angle dependent corrections to responsivities of pyranometers removes 15 to 30 W/m2 bias errors from field measurements. Detailed uncertainty analysis of our outdoor calibration process shows a 20% reduction in the uncertainty in the responsivity of pyranometers. These improvements affect photovoltaic module and array performance characterization, assessment of solar resources for design, sizing, and deployment of solar renewable energy systems, and ground-based validation of satellite-derived solar radiation fluxes.
Control of Flexible-Link Multiple Manipulators
Authors: Sun Qiao
Published: July 2002

In this paper, we consider the object trajectory tracking control for flexible-link cooperating manipulators. In particular, we develop a stable inversion control law which is commonly known as the inverse dynamics control or the computed torque method for rigid manipulators. Difficulties in applying this method to the control of flexible link manipulators are due to the fact that the inverse dynamics system is generally unstable because of the inherently unstable zero dynamics. As such, bounded actuator torques cannot be guaranteed. For multiple manipulators handling a common object, there are more actuators than the degrees of freedom of the system. Through decomposing the manipulator end-effector wrenches into resultant and internal force components, control laws are derived such that the internal forces are used to stabilize the system zero dynamics. Consequently, nonlinear inversion control can be applied for the object trajectory tracking control. Numerical simulations are performed to illustrate the performance of the control strategy developed in the paper.
Analysis of High Volume Fraction Irregular Particulate Damping
Composites
Authors: Lakes R. S. , Kose S. , Bahia H.
Published: July 2002

Concentrated suspensions of inclusions occur in asphalt and dental composite resins. Concentrated suspensions are also of use in achieving a combination of high stiffness and loss (the product E tan δ), desirable in damping layer and structural damping applications. For realizable particulate microstructures, analytical solutions for monodisperse inclusion morphologies such as spherical, random fibrous and platelet, are valid only in the case of a dilute concentration of inclusions. Finite element analyses were conducted of hierarchical particulate composites with high volume fractions of particles of irregular shape. For particle volume concentration 40 percent or less, the results are close to the Hashin-Shtrikman lower formula in a stiffness versus concentration plot and in a stiffness loss map. For larger concentration, stiffness is higher and E tan δ is lower. The irregular particle shape therefore enhances stiffness at a given concentration, and reduces damping layer performance.
Birefringence Reducing Precision Replication Process Assisted by Infrared Radiation
Authors: Sato Kimitoshi , Kurosaki Yasuo
Published: July 2002

This paper proposes a novel precision replication procedure having two stages: a molding process and a replication process assisted by an infrared radiation from an external source, and possessing the effect of birefringence reduction simultaneously. The experiments had been conducted for the replication process of CD. The proposed process has been proved to be feasible for the submicron replication by heating the surface of the resin, therefore, the reduction of birefringence remained in a work piece by some tens seconds irradiation.
Numerical simulation of finite dimensional multibody nonsmooth mechanical systems
Authors: Brogliato B , ten Dam AA , Paoli L , Ge´not F , Abadie M
Published: July 2002

This review article focuses on the problems related to numerical simulation of finite dimensional nonsmooth multibody mechanical systems. The rigid body dynamical case is examined here. This class of systems involves complementarity conditions and impact phenomena, which make its study and numerical analysis a difficult problem that cannot be solved by relying on known Ordinary Differential Equation (ODE) or Differential Algebraic Equation (DAE) integrators only. The main techniques, mathematical tools, and existing algorithms are reviewed. The article utilizes 233 references.
Vibrations of the All-Ceramic Ball Bearing
Authors: Ohta Hiroyuki , Satake Shinya
Published: July 2002

All-ceramic ball bearings with silicone nitride balls and silicone nitride rings were tested and the vibration characteristics were compared with those of hybrid ceramic ball bearings and conventional steel ball bearings. The vibration measurement results showed that the overall vibratory velocity levels of the all-ceramic ball bearings are influenced by rotational velocities, and do not change with axial loads. Under a given axial load and rotational velocity, the overall vibratory velocity level of the all-ceramic ball bearing is the lowest, and the hybrid ball bearing the highest. The frequencies of main peaks in the measured vibration spectra of the all-ceramic ball bearing are higher than the frequencies of the corresponding main peaks for the hybrid ceramic ball bearing and the steel ball bearing. To explain the main peaks, modal analysis was done and the relationship between peak and natural vibration was analyzed. The results of the analyses showed that the main peaks are caused by: (1) the mass-type natural vibration of the outer ring in the vertical direction, (2) the bending natural vibration of the outer ring in the radial direction, (3) the moment of inertia-type natural vibration of the outer ring in the angular direction, (4) the mass-type natural vibration of the outer ring in the axial direction, and (5) the bending natural vibration of the outer ring in the axial direction. We also discuss the generating mechanism of the vibration and present the calculation method of the vibration spectra. As a result, it is clear that the vibration spectra of the all-ceramic ball bearing are determined by the amplitude of the waviness of the raceways and ball surface, the mobility, and the non-linear spring constant associated with the contact between the raceways and balls.
Mechanical Analysis of Ultrasonic Bonding for Rapid Prototyping
Authors: Gao Yuan , Doumanidis Charalabos
Published: July 2002

Ultrasonic bonding of thin foils has been recently introduced to rapid prototyping of complex-shaped and/or internally structured layered parts. This article provides the mechanical analysis of an elementary ultrasonic spot welding process of a metal foil on a previously deposited substrate. A 2-D, quasi-static/dynamic, elasto-plastic numerical model of the stress/strain field is developed by finite element analysis. Its frictional boundary conditions at the foil/substrate interface are described via a simpler plain stress, static analytical formulation, and identified experimentally by strain measurements on the substrate surface, adjacently to the ultrasonic probe. The calibrated computational simulation is validated in the laboratory and applied in studying the elastic stress concentrations, plastic deformation initiation and propagation patterns, the slippage at the interface surface and the dynamic effects of ultrasonic loading on the bonding process. This mechanical model is suitable for analysis of multi-joint ultrasonic rapid prototyping and its applications in fabrication of multi-material, functional internal structures with embedded components.
Maximization of Workspace Volume of 3-DOF Spatial Parallel Manipulators
Authors: Miller Karol
Published: July 2002

In this work we investigate the influence of motor axes orientation on the workspace volume of 3-DOF manipulators, showing that the Delta configuration is not optimal. The configuration characterized by α=ArcTan1/2≈35.26°—the inclination of each motor axis to the horizontal plane (for the Delta robot α=0°), and β=60°—the rotation of each motor with respect to the vertical axis (for the Delta robot β=0°), known as the New University of Western Australia Robot (NUWAR) is shown to be advantageous over the Delta configuration in terms of workspace volume and shape. These results led to the construction of a prototype and an Australian Patent application.
The Role of “Allowable Flux Density” in the Design and Operation of Molten-Salt Solar Central Receivers
Authors: Vant-Hull Lorin L.
Published: July 2002

In the 1980s, the Utility Study [Hilesland, T., Jr., and Weber, E. R., 1988, “Utilities’ Study of Solar Central Receivers,” Fourth Int. Symp. on Research, Development, and Applications of Solar Thermal Technology, Santa Fe, NM] identified the external cylindrical molten-salt-in-tube receiver with a surround heliostat field as the most cost effective and practical design for commercial applications. Such designs typically require 50–1000 MW of design-point thermal power at outlet temperatures around 1050°F (565°C). Using computer codes such as RCELL [Lipps, F. W., and Vant-Hull, L. L., 1978, “A Cellwise Method for the Optimization of Large Central Receiver Systems,” Solar Energy, 20(6) pp. 505–516.] or DELSOL [Kistler, B. L., “A Users Manual for Delsol 3,” Sandia National Laboratories Livermore, SAND86-8018, 1987.] it is straightforward to design an optical system to meet these requirements, defining the smallest receiver (lower cost and thermal losses) and the most cost effective heliostat field. As the performance of heliostats in the anti-sun locations is better, such fields tend to be biased (in the northern hemisphere) to the north side of the receiver, and produce very high flux densities there; typically 2–5 MW/m2. However, the receiver is typicaly limited to a salt velocity and temperature dependent allowable flux density (AFD) of about 1 MW/m2. Design methods to reduce this peak flux to a nominally acceptable value in a cost effective manner are presented. Residual excess flux events under non-nominal conditions are handled by a real-time processor which selects specific heliostats for removal from track. This same processor is used to preheat the receiver, using a special algorithm to define the required flux density.
Boundary-Element Methods In Offshore Structure Analysis
Authors: Newman J. N. , Lee C.-H.
Published: July 2002

Boundary-element methods, also known as panel methods, have been widely used for computations of wave loads and other hydrodynamic characteristics associated with the interactions of offshore structures with waves. In the conventional approach, based on the low-order panel method, the submerged surface of the structure is represented by a large number of small quadrilateral plane elements, and the solution for the velocity potential or source strength is approximated by a constant value on each element. In this paper, we describe two recent developments of the panel method. One is a higher-order method where the submerged surface can be represented exactly, or approximated to a high degree of accuracy by B-splines, and the velocity potential is also approximated by B-splines. This technique, which was first used in the research code HIPAN, has now been extended and implemented in WAMIT. In many cases of practical importance, it is now possible to represent the geometry exactly to avoid the extra work required previously to develop panel input files for each structure. It is also possible to combine the same or different structures which are represented in this manner, to analyze multiple-body hydrodynamic interactions. Also described is the pre-corrected Fast Fourier Transform method (pFFT) which can reduce the computational time and required memory of the low-order method by an order of magnitude. In addition to descriptions of the two methods, several different applications are presented.
Thermal Integral Micro-Generation Systems for Solar and Conventional Use
Authors: Kribus Abraham
Published: July 2002

Thermal Integral Micro-Generation (TIMGen) systems on the scale of a few Watts are proposed for use with solar or fuel-derived heat. The optics, the thermal receiver, and several alternative generation technologies, including MEMS heat engines (Stirling and Brayton cycles), thermal photovoltaics, and thermoelectric, are discussed. Analysis of system performance shows the potential for efficiency comparable to photovoltaic cells and large-scale thermal plants. A major advantage of thermal systems over PV cells is the possibility of hybrid operation, both with sunlight and with another heat source when sunlight is not available. The alternative heat source can be another renewable or conventional fossil fuel. TIMGen plants compared to large-scale centralized thermal plants offer the advantages of modularity, scalability, redundancy and low cost via mass production. They can prove to be a very attractive option both for remote, self-contained electricity generation, and as an alternative to large-scale centralized plants.
Structural Synthesis of Multi-Fingered Hands
Authors: Lee Jyh-Jone , Tsai Lung-Wen
Published: July 2002

The kinematic structure of a mechanical hand typically resembles the skeleton of a human hand and it is usually designed to emulate a subset of the functions of a human hand. This paper analyzes the structural characteristics associated with the functional requirements of a mechanical hand. Using the mobility criterion and force closure concept, constraint equations for structural synthesis of multi-fingered mechanical hands are derived. A procedure for systematic enumeration of the kinematic structures of mechanical hands is established. An atlas of feasible kinematic structures of multi-fingered hands having a mobility number ranging from 3 to 6 and contact degrees of freedom ranging from 1 to 5 is developed. Further, two theorems concerning the structural characteristics of mechanical hands are presented.
A General Framework for Rigid Body Dynamics, Stability, and Control
Authors: Hemami Hooshang
Published: July 2002

Augmented state spaces for the representation of systems that include rigid bodies, actuators, controllers, and integrate mechanical, electrical, sensory, and computational subsystems, are proposed here. The formulation is based on the Newton-Euler point of view, and has many advantages in stability, control, simulation, and computational considerations. The formulation is developed here for a one- and two-link three-dimensional rigid body system. Three simulations are presented to study stability of the system and to demonstrate feasibility and application of the formulation. The formulation affords an embedding of the system in a larger state space. The rigid body system can be stabilized, in the sense of Lyapunov, in this larger space with very general and minimally restricted feedback structures. The formulation is modular to implementation and is computationally efficient. The method offers alternative states that are easier to control and measure than Euler angles. Thus, the formulation offers advantages from a sensory and instrumentation point of view. The formulation is versatile, and yields conveniently to applications in studies of human neuro-musculo-skeletal systems, robotic systems, marionettes and humanoids for animation and simulation of crash and other injury prone maneuvers and sports. It offers a methodical and systematic procedure for formulation of large systems of interconnected rigid bodies.
Mechanism of Nucleate Boiling Heat Transfer Enhancement From
Microporous Surfaces in Saturated FC-72
Authors: Kim J. H. , Rainey K. N. , You S. M. , Pak J. Y.
Published: July 2002

The present study is an experimental investigation of the nucleate pool boiling heat transfer enhancement mechanism of microporous surfaces immersed in saturated FC-72. Measurements of bubble size, frequency, and vapor flow rate from a plain and microporous coated 390 μm diameter platinum wire using the consecutive-photo method were taken to determine the effects of the coating on the convective and latent heat transfer mechanisms. Results of the study showed that the microporous coating augments nucleate boiling performance through increased latent heat transfer in the low heat flux region and through increased convection heat transfer in the high heat flux region. The critical heat flux for the microporous coated surface is significantly enhanced over the plain surface due to decreased latent heat transfer (decreased vapor generation rate) and/or increased hydrodynamic stability from increased vapor inertia; both of which are a direct result of increased nucleation site density.
Design and Control of a Force-Reflecting Haptic Interface for Teleoperational Grasping
Authors: Springer Scott L. , Ferrier Nicola J.
Published: July 2002

In this paper the design of a multi-finger force-reflecting haptic interface device for teleoperational grasping is introduced. The haptic interface or “master” controller device is worn on the human operator’s hand and measured human finger positions are used to control the finger positions of a remote grasping manipulator or “slave” device. The slave may be a physical robotic grasping manipulator, or a computer generated representation of a human hand such as used in virtual reality applications. The forces measured by the robotic slave, or calculated for the virtual slave, are presented to the operator’s fingertips through the master providing a means for deeper human sensation of presence and better control of grasping tasks in the slave environments. Design parameters and performance measures for haptic interfaces for teleoperation are discussed. One key performance issue involving the high-speed display of forces during initial contact, especially when interacting with rigid surfaces, is addressed by the present design, reducing slave controller computation requirements and overcoming actuator response time constraints. The design presented utilizes a planar four-bar linkage for each finger, to represent each finger bend motion as a single degree of freedom, and to provide a finger bend resistance force that is substantially perpendicular to the distal finger pad throughout the full 180 degrees of finger bend motion represented. The finger linkage design, in combination with a remote position measurement and force display assembly, provides a very lightweight and low inertia system with a large workspace. The concept of a replicated finger is introduced which, in combination with a decoupled actuator and feed forward control, provides improved performance in transparent free motion, and rapid, stable touch sensation of initial contact with rigid surfaces. A distributed computation architecture with a PC based haptic interface controller and associated control algorithms are also discussed.
Strategies for Product Structure Management at Manufacturing Firms
Authors: Svensson Daniel , Malmqvist Johan
Published: July 2002

Product structure management (PSM) is a process that affects many of the activity domains1. (AD) in a company. Different ADs have different requirements for the decomposition of a product structure and the function of the information systems (IS) used. Departments therefore often work in differing ISs. If several ISs contain some of the same information, it is important that it be updated in all systems when it is changed. Since PSM is a change intensive activity, it is difficult to perform it in an environment consisting of several heterogeneous ISs. There is a need for strategies of PSM that take into account all relevant aspects of an IS, such as the process it supports, the type of information handled, the systems used and the organization. Based on a case study at an automotive manufacturing firm, this paper discusses the diverse product structure requirements of various ADs. Proposed strategies for PSM can be used as a general guide and for categorization when analyzing ISs before introducing new systems or restructuring existing systems.
Numerical Modeling of Wind Turbine Wakes
Authors: So̸rensen Jens No̸rkær , Shen Wen Zhong
Published: July 2002

An aerodynamical model for studying three-dimensional flow fields about wind turbine rotors is presented. The developed algorithm combines a three-dimensional Navier-Stokes solver with a so-called actuator line technique in which the loading is distributed along lines representing the blade forces. The loading is determined iteratively using a blade-element approach and tabulated airfoil data. Computations are carried out for a 500 kW Nordtank wind turbine equipped with three LM19.1 blades. The computed power production is found to be in good agreement with measurements. The computations give detailed information about basic features of wind turbine wakes, including distributions of interference factors and vortex structures. The model serves in particular to analyze and verify the validity of the basic assumptions employed in the simple engineering models.
Evolutionary Optimization and Use of Neural Network for Optimum Stamping Process Design for Minimum Springback
Authors: Liew K. M. , Ray Tapabrata , Tan , and H. , Tan M. J.
Published: July 2002

Sheet metal forming is characterized by various process parameters such as the forming sequence, shapes of products and dies, friction parameters, forming speed etc. A designer is faced with the challenge of identifying optimal process parameters for minimum springback. Currently, a vast majority of such applications in practice are guided by trial and error and user experience. In this paper, we present two useful designer aids; an evolutionary algorithm and a neural network integrated evolutionary algorithm. We have taken a simple springback minimization problem to illustrate the methodology although the evolutionary algorithm is generic and capable of handling both single and multiobjective, unconstrained and constrained optimization problems. The springback minimization problem has been modeled as a discrete variable, unconstrained, single objective optimization problem and solved using both optimization methods. Both the algorithms are capable of generating multiple optimal solutions in a single run unlike most available optimization methods that provide a single solution. The neural network integrated evolutionary algorithm reduces the computational time significantly as the neural network approximates the springback instead of performing an actual springback computation. The results clearly indicate that both the algorithms are useful optimization tools that can be used to solve a variety of parametric optimization problems in the domain of sheet metal forming.
Combined Torsion, Circular and Axial Shearing of a Compressible Hyperelastic and Prestressed Tube
Authors: Zidi M.
Published: July 2002

In this paper, we study the combined torsion, circular and axial shearing of a compressible hyperelastic and prestressed tube. The analysis is carried out for a class of Ogden elastic material and the governing nonlinear equations are solved numerically using the Runge-Kutta method. The results reported present the effects of the torsion for different shearing loads on the local volume change and the circumferential stretch ratio. The effect of the second invariant-dependent behavior of polynomial materials is also investigated. [S0021-8936(00)01301-5]
Aerodynamic Characteristics of Pressure-Pad Air Bars
Authors: Chang Y. B. , Moretti P. M.
Published: July 2002

Air-flotation ovens are widely used for noncontact support and drying of coated paper and plastic films (generically called webs). The main components in typical air-flotation ovens are air bars which have slot nozzles or holes through which hot air jets are ejected. Problems in air-flotation drying techniques include sideward motion of the web, web flutter, and contact between the web and air bars. The key to analyzing these problems is to determine the aerodynamic forces on the web. This paper discusses the aerodynamic forces generated by pressure-pad-type air bars, each of which has two slot nozzles. Ground-effect theories, which were originally developed for the design of hovercraft, are re-examined. The theories are compared with the measured values of the aerodynamic forces for typical air bars. It is shown that ground effect theories can be applied to pressure-pad-type air bars if we properly define the equivalent values of the ground effect variables, which include thickness of the air jet, flotation height, ejection angle of the air jet, and the effective total pressure of the air jet. [S0021-8936(00)02801-4]
Disturbance Observer Based Tracking Control
Authors: Liu Chia-Shang , Peng Huei
Published: July 2002

A disturbance observer based tracking control algorithm is presented in this paper. The key idea of the proposed method is that the plant nonlinearities and parameter variations can be lumped into a disturbance term. The lumped disturbance signal is estimated based on a plant dynamic observer. A state observer then corrects the disturbance estimation in a two-step design. First, a Lyapunov-based feedback estimation law is used. The estimation is then improved by using a feedforward correction term. The control of a telescopic robot arm is used as an example system for the proposed algorithm. Simulation results comparing the proposed algorithm against a standard adaptive control scheme and a sliding mode control algorithm show that the proposed scheme achieves superior performance, especially when large external disturbances are present. [S0022-0434(00)00802-9]
Damage-Mitigating Control With Overload Injection: Experimental Validation of the Concept1
Authors: Zhang Hui , Ray Asok , Patankar Ravindra
Published: July 2002

The goal of damage-mitigating control is to enhance structural durability of mechanical systems (e.g., advanced aircraft, spacecraft, and power plants) while retaining high performance. So far the reported work in damage-mitigating control has focused on reduction of peak stresses to increase structural durability. This paper presents a novel concept that takes advantage of the physical phenomenon of fatigue crack retardation. Overload pulses are intermittently injected into the plant as a feedforward signal through the actuator(s) in addition to robust feedback control. A feedforward sequence of limited overload pulses and a robust feedback control law are designed based on state-space models of fatigue-crack damage and plant dynamics. A series of experiments have been conducted on a laboratory test apparatus to demonstrate feasibility of the overload injection concept for robust damage-mitigating control. [S0022-0434(00)01302-2]
Minimizing the Effect of Out of Bandwidth Modes in Truncated Structure Models
Authors: Moheimani S. O. Reza
Published: July 2002

The modal analysis approach to modeling of structures and acoustic systems results in infinite-dimensional models. For control design purposes, these models are simplified by removing higher frequency modes which lie out of the bandwidth of interest. Truncation can considerably perturb the in-bandwidth zeros of the truncated model. This paper suggests a method of minimizing the effect of the removed higher order modes on the low frequency dynamics of the truncated model by adding a zero frequency term to the low order model of the system. [S0022-0434(00)01501-X]
Uniaxial Ratchetting of 316FR Steel at Room Temperature— Part II: Constitutive Modeling and Simulation
Authors: Ohno N. , Abdel-Karim M.
Published: July 2002

Uniaxial ratchetting experiments of 316FR steel at room temperature reported in Part I are simulated using a new kinematic hardening model which has two kinds of dynamic recovery terms. The model, which features the capability of simulating slight opening of stress-strain hysteresis loops robustly, is formulated by furnishing the Armstrong and Frederick model with the critical state of dynamic recovery introduced by Ohno and Wang (1993). The model is then combined with a viscoplastic equation, and the resulting constitutive model is applied successfully to simulating the experiments. It is shown that for ratchetting under stress cycling with negative stress ratio, viscoplasticity and slight opening of hysteresis loops are effective mainly in early and subsequent cycles, respectively, whereas for ratchetting under zero-to-tension only viscoplasticity is effective. [S0094-4289(00)00501-6]
Densification Behavior of Ceramic Powder Under Cold Compaction
Authors: Kim K. T. , Choi S. W. , Park H.
Published: July 2002

Densification behavior of ceramic powder under cold compaction was investigated. Experimental data were obtained for zirconia powder under triaxial compression with various loading conditions. For densification of ceramic powder during cold compaction, a novel hyperbolic cap model was proposed from the iso-density curves based on experimental data of zirconia powder under triaxial compression. The proposed model was implemented into a finite element program (ABAQUS) to study densification behavior of zirconia powder under die compaction. The modified Drucker–Prager/cap model was also employed to compare with experimental data and the finite element results from the proposed model in the present work. By including the effect of friction between the powder and die wall, density distributions of a zirconia compact were measured and compared with finite element results under die compaction. [S0094-4289(00)00102-X]