bluuebunny/crossref_metadata_2025 huggingface dataset:
Importing and reshaping digitized data for use in rapid prototyping: a system for sculpting polygonal mesh surfaces
Authors: Alciatore David G. , Wohlers Terry T.
Published: July 2002

Focuses on the development and testing of software for reading and formatting digitized data and exporting it to rapid prototyping (RP). Research and development over two years has involved the implementation of special computer‐aided sculpting software that runs on UNIX workstations and which imports 3D polygonal mesh data in STL, OBJ and DXF formats, then re‐shapes it, much like the pushing and pulling on the surface of a rubber membrane. Specifying a wall thickness gives the model volume, prior to exporting an STL file. Describes how data has been imported form laser digitizing systems, had its shape changed and then how RP parts have been created from the model data.
Piezoelectric ceramics and composites via rapid prototyping techniques
Authors: Bandyopadhyay A. , Panda R.K. , McNulty T.F. , Mohammadi F. , Danforth S.C. , Safari A.
Published: July 2002

Reviews the inherent advantages, i.e. design flexibility and processing, of manufacturing piezoelectric ceramics and composites with numerous architectures via rapid prototyping techniques. Reports on processing in which piezoelectric ceramics and composites with novel and conventional designs were fabricated using rapid prototyping techniques. Fused deposition of ceramics, fused deposition modeling, and Sanders prototyping techniques were used to fabricate lead‐zirconate‐titanate ceramics and ceramic/polymer composites via, first, direct fabrication and, second, indirect fabrication using either lost mold or soft tooling techniques.
High performance liquid cooled aluminium nitride heat sinks
Authors: Hahn R. , Glaw V. , Ginolas A. , Töpfer M. , Wittke K. , Reichl H.
Published: July 2002

High performance aluminium nitride water cooled heat sinks were fabricated and characterized. A variety of fabrication processes were employed to meet different cooling requirements. They include laser cut microchannel coolers for chip and multichip heat sinks as well as dry pressed pin fin heat sinks for power electronics. Thermal simulation was used to optimize the heat sink design.
High frequency wire bonding for PBGA package, a process optimisation approach
Authors: Kiat Choon Teo , Corpuz Victor G.
Published: July 2002

In a plastic BGA package, the glass transition temperature of 170‐215°C for bismaleimide triazine (BT) substrate puts an upper ceiling to the usable wire bond temperature. To compensate for the limitation in thermal energy, high frequency thermosonic bonding was proposed and successfully demonstrated for plastic BGA wire bonding. Design of experiment (DOE) and response surface methods (RSM) for process optimisation were used; bonded areas were also analysed using scanning electron microscope (SEM). Of the four major bonding parameters were investigated, ultrasonic power and bond force appeared to be the most important control factor for wire pulls and ball shear force optimisation. The results show that bonding at low temperature is viable with the use of high frequency transducer wire bonder.
Reduction of the amyloidogenicity of a protein by specific binding of ligands to the native conformation
Authors: Chiti Fabrizio , Taddei Niccolò , Stefani Massimo , Dobson Christopher M. , Ramponi Giampietro
Published: July 2002

It is known that human muscle acylphosphatase (AcP) is able, under appropriate conditions in vitro, to aggregate and form amyloid fibrils of the type associated with human diseases. A number of compounds were tested for their ability to bind specifically to the native conformation of AcP under conditions favoring denaturation and subsequent aggregation and fibril formation. Compounds displaying different binding affinities for AcP were selected and their ability to inhibit protein fibrillization in vitro was evaluated. We found that compounds displaying a relatively high affinity for AcP are able to significantly delay protein fibrillization, mimicking the effect of stabilizing mutations; in addition, the effectiveness of such outcome correlates positively to both ligand concentration and affinity to the native state of AcP. By contrast, the inhibitory effect of ligands on AcP aggregation disappears in a mutant protein in which such binding affinity is lost. These results indicate that the stabilization of the native conformation of amyloidogenic proteins by specific ligand binding can be a strategy of general interest to inhibit amyloid formation in vivo.
Effect of Personality Dimensions on the Diurnal Pattern of Motor Activity
Authors: Volkers Anita C. , Tulen Joke H. M. , Duivenvoorden Hugo J. , Gieteling Marieke J. , Wegewijs‐De Jong Marlies , Van Den Broek Walter W. , Passchier Jan , Pepplinkhuizen Lolke
Published: July 2002

ABSTRACTThe effects of personality dimensions, age, and gender on 24‐hour motor activity patterns were studied in 101 healthy subjects between 20–70 years. We measured motor activity by wrist‐actigraphy and personality dimensions by the Tridimensional Personality Questionnaire (TPQ) of Cloninger. Random Regression Models were used to estimate the effects of personality dimensions, age, and gender on the diurnal pattern of motor activity. Harm Avoidance as well as Reward Dependence influenced the overall level of motor activity, independent of age and gender. Subjects high on Harm Avoidance showed lower activity levels than subjects low on Harm Avoidance, whereas subjects high on Reward Dependence had higher overall levels of motor activity than subjects low on Reward Dependence. Older subjects were found to be less active than younger subjects, but the activity level did not differ between males and females.
Modulation of non‐monosynaptic excitation from ankle dorsiflexor afferents to quadriceps motoneurones during human walking
Authors: Marchand‐Pauvert V. , Nielsen J. B.
Published: July 2002

Modulation of non‐monosynaptic excitation from ankle dorsiflexors to quadriceps (Q) motoneurones during human treadmill walking was investigated in 25 healthy human subjects. Stimulation of the common peroneal nerve (CPN) evoked a biphasic facilitation in the rectified and averaged (n= 50) Q electromyographic (EMG) activity between 0 and 100 ms after heel strike. Prior to heel strike, the stimulation had no effect on the Q EMG. The latency of both peaks in the response was too long to be explained by a monosynaptic pathway to Q motoneurones. During voluntary tonic co‐contraction of Q and tibialis anterior (TA) while standing, only the first of the two peaks was evoked by the CPN stimulation despite a background EMG activity level in the Q and TA muscles corresponding to that observed 30–60 ms after heel strike during walking. Stimulation of cutaneous nerves did not evoke a similar biphasic facilitation in the Q motoneurones, which suggests that muscular afferents mediate the response. The second peak had a higher threshold than the earlier peak. During cooling of the CPN, the latency of the second peak was more prolonged than the latency of the earlier peak. This suggests that afferents of different diameters contributed to the two peaks. It is proposed that afferents from TA assist the contraction of Q during walking via spinal interneurones to stabilize the knee joint and maintain upright posture during walking.
The intent to exercise influences the cerebral O2/carbohydrate uptake ratio in humans
Authors: Dalsgaard Mads K. , Ide Kojiro , Cai Yan , Quistorff Bjørn , Secher Niels H.
Published: July 2002

During and after maximal exercise there is a 15–30 % decrease in the metabolic uptake ratio (O2/[glucose +1/2lactate]) and a net lactate uptake by the human brain. This study evaluated if this cerebral metabolic uptake ratio is influenced by the intent to exercise, and whether a change could be explained by substrates other than glucose and lactate. The arterial‐internal jugular venous differences (a‐v difference) for O2, glucose and lactate as well as for glutamate, glutamine, alanine, glycerol and free fatty acids were evaluated in 10 healthy human subjects in response to cycling. However, the a‐v difference for the amino acids and glycerol did not change significantly, and there was only a minimal increase in the a‐v difference for free fatty acids after maximal exercise. After maximal exercise the metabolic uptake ratio of the brain decreased from 6.1 ± 0.5 (mean ±s.e.m.) at rest to 3.7 ± 0.2 in the first minutes of the recovery (P< 0.01). Submaximal exercise did not change the uptake ratio significantly. Yet, in a second experiment, when submaximal exercise required a maximal effort due to partial neuromuscular blockade, the ratio decreased and remained low (4.9 ± 0.2) in the early recovery (n= 10;P< 0.05). The results indicate that glucose and lactate uptake by the brain are increased out of proportion to O2when the brain is activated by exhaustive exercise, and that such metabolic changes are influenced by the will to exercise. We speculate that the uptake ratio for the brain may serve as a metabolic indicator of ‘central fatigue’.
Sympathetic modulation of muscle spindle afferent sensitivity to stretch in rabbit jaw closing muscles
Authors: Roatta S. , Windhorst U. , Ljubisavljevic M. , Johansson H. , Passatore M.
Published: July 2002

Previous reports showed that sympathetic stimulation affects the activity of muscle spindle afferents (MSAs). The aim of the present work is to study the characteristics of sympathetic modulation of MSA response to stretch: (i) on the dynamic and static components of the stretch response, and (ii) on group Ia and II MSAs to evaluate potentially different effects. In anaesthetised rabbits, the peripheral stump of the cervical sympathetic nerve (CSN) was stimulated at 10 impulses s−1for 45–90 s. The responses of single MSAs to trapezoidal displacement of the mandible were recorded from the mesencephalic trigeminal nucleus. The following characteristic parameters were determined from averaged trapezoidal responses: initial frequency (IF), peak frequency at the end of the ramp (PF), and static index (SI). From these, other parameters were derived: dynamic index (DI = PF ‐ SI), dynamic difference (DD = PF ‐ IF) and static difference (SD = SI ‐ IF). The effects of CSN stimulation were also evaluated during changes in the state of intrafusal muscle fibre contraction induced by succinylcholine and curare. In a population of 124 MSAs, 106 units (85.4 %) were affected by sympathetic stimulation. In general, while changes in resting discharge varied among different units (Iavs.II) and experimental conditions (curarisedvs.non‐curarised), ranging from enhancement to strong depression of firing, the amplitude of the response to muscle stretches consistently decreased. This was confirmed and detailed in a quantitative analysis performed on 49 muscle spindle afferents. In both the non‐curarised (23 units) and curarised (26 units) condition, stimulation of the CSN reduced the response amplitude in terms of DD and SD, but hardly affected DI. The effects were equally present in both Ia and II units; they were shown to be independent from gamma drive and intrafusal muscle tone and not secondary to muscle hypoxia. Sympathetic action on the resting discharge (IF) was less consistent. In the non‐curarised condition, IF decreased in most Ia units, while in II units decreases and increases occurred equally often. In the curarised condition, IF in group II units mostly increased. The results have important functional implications on the control of motor function in a state of ‘high’ sympathetic activity, like excessive stress, as well as in certain pathological conditions such as sympathetically maintained pain.
Factors Affecting the Operational Thermal Resistance of Electronic Components
Authors: Davies Mark R. D. , Cole Reena , Lohan John
Published: July 2002

The thermal resistance of electronic components is known to often differ considerably between standard test conditions and those found in service. One way to correct for this is to use multi-parameter thermal resistances. Another, presented here, is to adjust the junction-to-ambient thermal resistance to account for operational conditions. For forced convection applications, two factors are proposed; the first accounts for any upstream aerodynamic disturbance and the second addresses purely thermal interaction. Thus if an upstream powered component interacts with a downstream component, the two factors are combined. It is shown that both factors may be quantified in terms of readily measured temperatures and then used as coefficients to adjust the standard thermal resistance data for operational conditions. To overcome the misconception that the currently published single-value thermal resistances are solely a property of the electronic package, thermal resistance is redefined to include both the resistance of the package and the part of the printed circuit board (PCB) covered by the component thermal footprint. This approach is applied to a symmetrical array of board mounted 160-lead devices and data showing how the factors vary with component position, nondimensional power distribution and Reynolds number is presented. Based on data a new method of generating operational component thermal resistances is proposed. [S1043-7398(00)00603-4]
A General Time Dependent Constitutive Model: Part I— Theoretical Developments1
Authors: Saleeb A. F. , Arnold S. M.
Published: July 2002

Using an internal-variable formalism as a starting point, we describe the viscoelastic complement of a previously-developed viscoplasticity formulation of the complete potential structure type. It is mainly motivated by experimental evidence for the presence of rate/time effects in the so-called quasilinear, reversible, material response range. Several possible generalizations are described, in the general format of hereditary-integral representations for nonequilibrium, stress-type, state variables, both for isotropic as well as anisotropic materials. In particular, thorough discussions are given on the important issues of thermodynamic admissibility requirements for such general descriptions, resulting in a set of explicit mathematical constraints on the associated kernel (relaxation and creep compliance) functions. In addition, a number of explicit, integrated forms are derived, under stress and strain control to facilitate the parametric and qualitative response characteristic studies reported here, as well as to help identify critical factors in the actual experimental characterizations from test data that will be reported in Part II.
Experimental Evaluation of the Lateral Contact Force in Horizontal Wells
Authors: Martinez Alexander , Miska Stefan , Kuru Ergun , Sorem James
Published: July 2002

In horizontal and extended reach drilling, a large frictional drag may occur. If the pipe buckles laterally or into a helical shape, additional lateral contact force, LCF, is developed between the pipe and the wellbore wall, increasing the drag force. This paper presents the results of an experimental study of the lateral contact force between the drill pipe and the wellbore wall, for helical pipe configuration. Comparison of the experimental results with the current analytical models is also presented. A horizontal well was simulated using a 2-in-dia hole, 86-ft long, and three different sizes of pipe. Two different techniques were used to measure the lateral contact force. Results from both techniques seem to be in good agreement. The comparison with the current analytical models shows that higher values are predicted. The results will find application in directional drilling, horizontal drilling, and coiled tubing operations. [S0195-0738(00)00603-8]
Unsteady Transport Mechanisms in an Axial Turbine
Authors: Casciaro Claudia , Treiber Martin , Sell Michael
Published: July 2002

A numerical analysis using a commercial unsteady Navier–Stokes solver has been performed on a pin/blade configuration, in order to assess the efficacy of a commercial code in calculating time-periodic interactions and to gain a better understanding of the unsteady flow physics in axial turbines. Two cases have been investigated, with the pin positioned at 25 and 50 percent of true chord ahead of the leading edge. Both configurations have been computed both two and three dimensionally. The two-dimensional case was used to examine the influence of numerical parameters, such as mesh, time, and space discretization. The three-dimensional case allowed insight into the complete flow field including the wake influence on the secondary flow and mixing processes of the blade row. The basic mechanisms of the wake–blade interaction proved, as expected, to be the same for both pin positions. Yet, as the closest pin wake interaction with the blade field was much stronger, its features have helped to identify the respective roles of wake fluid transport and blade potential field for both cases. The latter effect, noticeably strong with the thick leading edge blade form presented in this study, has often been neglected, and this study helps shed new light on this phenomenon. The code used had been validated in previous work for pin-free steady flow within the same blade row and the new time-dependent case has served to confirm the code range and limitations. [S0889-504X(00)02104-8]
Minimizing the Truncation Error in Assumed Modes Models of Structures
Authors: Moheimani S. O. Reza , Clark Robert L.
Published: July 2002

The assumed modes approach is a widely used technique in modeling of distributed systems. Such models often consist of a large number of modes. For controller design purposes these models are simplified by truncating the modes that lie out of the bandwidth of interest. Truncation can alter zeros of the system. This paper presents a method of minimizing the truncation error by adding a second order term to the truncated model. This extra term is determined such that the in-bandwidth error is minimized in an optimal H2 sense. The technique is extended to multivariable systems. [S0739-3717(00)02003-1]
Love’s Stress Function for Torsionless Axisymmetric Deformation of Elastically Isotropic Bodies With Body Forces
Authors: Simmonds J. G.
Published: July 2002

This note shows that the axisymmetric deformation of an elastically isotropic solid of revolution, subject to both axial and radial body forces, may be described in terms of Love’s stress function, provided certain simple terms are added to the displacement-stress function relations. [S0021-8936(00)01003-5]
Theory of Anisotropic Thin-Walled Beams
Authors: Volovoi V. V. , Hodges D. H.
Published: July 2002

Asymptotically correct, linear theory is presented for thin-walled prismatic beams made of generally anisotropic materials. Consistent use of small parameters that are intrinsic to the problem permits a natural description of all thin-walled beams within a common framework, regardless of whether cross-sectional geometry is open, closed, or strip-like. Four “classical” one-dimensional variables associated with extension, twist, and bending in two orthogonal directions are employed. Analytical formulas are obtained for the resulting 4×4 cross-sectional stiffness matrix (which, in general, is fully populated and includes all elastic couplings) as well as for the strain field. Prior to this work no analytical theories for beams with closed cross sections were able to consistently include shell bending strain measures. Corrections stemming from those measures are shown to be important for certain cases. Contrary to widespread belief, it is demonstrated that for such “classical” theories, a cross section is not rigid in its own plane. Vlasov’s correction is shown to be unimportant for closed sections, while for open cross sections asymptotically correct formulas for this effect are provided. The latter result is an extension to a general contour of a result for I-beams previously published by the authors. [S0021-8936(00)03003-8]
A Stagnation Flow Analysis of the Heat Transfer and Fluid Flow Phenomena in Laser Drilling
Authors: Batteh J. J. , Chen M. M. , Mazumder J.
Published: July 2002

This paper presents a quasi-steady stagnation flow analysis for the material removal processes in high-intensity laser materials processing, such as laser drilling. The governing stagnation flow equations for the heat transfer and fluid flow phenomena are derived for the region near the centerline of the laser beam. The analysis accounts for conduction in the solid, conduction, and convection in the melt layer, and the latent heats of melting and vaporization. The stagnation flow governing equations and boundary conditions are appropriately normalized and solved, and the important combinations of material properties and independent laser parameters are identified. This semiquantitative analysis yields quasi-steady estimates for the penetration velocity, the thickness of the melt layer, the velocity and temperature profiles in the melt layer, and the fraction of melt that is vaporized for varying absorbed laser power and beam radius. Inviscid results from the stagnation flow analysis are shown for five different materials: aluminum, copper, low carbon steel, stainless steel, and titanium. Relatively good agreement exists between the results from the analysis and experimental data from the literature. [S0022-1481(00)01804-1]
Flow and Heat Transfer in a Rotating Square Channel With 45 deg Angled Ribs by Reynolds Stress Turbulence Model
Authors: Jang Yong-Jun , Chen Hamn-Ching , Han Je-Chin
Published: July 2002

Numerical predictions of three-dimensional flow and heat transfer are presented for a rotating square channel with 45 deg angled ribs as tested by Johnson et al. (1994). The rib height-to-hydraulic diameter ratio e/Dh is 0.1 and the rib pitch-to-height ratio (P/e) is 10. The cross section of the ribs has rounded edges and corners. The computation results are compared with the experimental data of Johnson et al. (1994) at a Reynolds number (Re) of 25,000, inlet coolant-to-wall density ratio Δρ/ρ of 0.13, and three rotation numbers (Ro) of 0.0, 0.12, and 0.24. A multiblock numerical method has been employed with a near-wall second-moment turbulence closure model. In the present method, the convective transport equations for momentum, energy, and turbulence quantities are solved in curvilinear, body-fitted coordinates using the finite-analytic method. Pressure is computed using a hybrid SIMPLER/PISO approach, which satisfies the continuity of mass and momentum simultaneously at every time step. The second-moment solutions show that the secondary flows induced by the angled ribs, rotating buoyancy, and Coriolis forces produced strong nonisotropic turbulent stresses and heat fluxes that significantly affected flow fields and surface heat transfer coefficients. The present near-wall second-moment closure model provided an improved flow and heat transfer prediction.
Performance Distribution Analysis and Robust Design
Authors: Zhu Jianmin , Ting Kwun-Lon
Published: July 2002

The paper presents the theory of performance sensitivity distribution and a novel robust parameter design technique. In the theory, a Jacobian matrix describes the effect of the component tolerance to the system performance, and the performance distribution is characterized in the variation space by a set of eigenvalues and eigenvectors. Thus, the feasible performance space is depicted as an ellipsoid. The size, shape, and orientation of the ellipsoid describe the quantity as well as quality of the feasible space and, therefore, the performance sensitivity distribution against the tolerance variation. The robustness of a design is evaluated by comparing the fitness between the ellipsoid feasible space and the tolerance space, which is a block, through a set of quantitative and qualitative indexes. The robust design can then be determined. The design approach is demonstrated in a mechanism design problem. Because of the generality of the analysis theory, the method can be used in any design situation as long as the relationship between the performance and design variables can be expressed analytically.
Application of Screw Theory to Constraint Analysis of Mechanical Assemblies Joined by Features
Authors: Adams Jeffrey D. , Whitney Daniel E.
Published: July 2002

Screw Theory is used to provide mathematical models of assembly features, allowing the determination of positioning constraints imposed on one part in an assembly by another part based on the geometry of the features that join them. Several feature types have been modeled, and it is easy to model new ones. A user of this theory is able to combine members of this set to join two parts and then determine whether or not the defined feature set over-, under-, or fully-constrains the location and orientation of the part. The ability to calculate the state of constraint of parts in an assembly is useful in supporting quantitative design of properly constrained assemblies in CAD systems. Locational over-constraint of parts can lead to assembleability problems or require deformation of parts in order to complete the assembly.
Laminar Burning Velocity of Methane–Air–Diluent Mixtures
Authors: Elia M. , Ulinski M. , Metghalchi M.
Published: July 2002

An experimental facility for measuring burning velocity has been designed and built. It consists of a spherical constant volume vessel equipped with a dynamic pressure transducer, ionization probes, thermocouple, and data acquisition system. The constant volume combustion vessel allows for the determination of the burning velocity over a wide range of temperatures and pressures from a single run. A new model has been developed to calculate the laminar burning velocity using the pressure data of the combustion process. The model solves conservation of mass and energy equations to determine the mass fraction of the burned gas as the combustion process proceeds. This new method allows for temperature gradients in the burned gas and the effects of flame stretch on burning velocity. Exact calculations of the burned gas properties are determined by using a chemical equilibrium code with gas properties from the JANAF Tables. Numerical differentiation of the mass fraction burned determines the rate of the mass fraction burned, from which the laminar burning velocity is calculated. Using this method, the laminar burning velocities of methane–air–diluent mixtures have been measured. A correlation has been developed for the range of pressures from 0.75 to 70 atm, unburned gas temperatures from 298 to 550 K, fuel/air equivalence ratios from 0.8 to 1.2, and diluent addition from 0 to 15 percent by volume.
Comparison of First-Order Shear and Plane Strain Assumptions in Warpage Prediction of Simply Supported Printed Wiring Boards
Authors: Polsky Yarom , Ume I. Charles
Published: July 2002

The influence of transverse shear strain in the lamination theory modeling of Printed Wiring Board (PWB) deflection due to support conditions was examined. The in-plane mechanical properties of the core materials of a commercial PWB were measured as a function of temperature. Classical laminated plate theory and first-order shear deformation theory solutions for the out-of-plane deflection of a bare board configuration with two opposite edges simply supported and the remaining edges free were obtained. The weight of the board was approximated as a distributed transverse load. The effect of material property decrease with temperature and FR-4 layer thickness were examined to compare first-order shear and plane strain assumptions for the predicted warpage.
An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV
Authors: Wernet Mark P. , Bright Michelle M. , Skoch Gary J.
Published: July 2002

Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle, and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to control these events successfully. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to capture transient velocity and pressure measurements simultaneously in the nonstationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique that is ideally suited for studying transient flow phenomena in high-speed turbomachinery and has been used previously to map the stable operating point flow field in the diffuser of a high-speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.
Shallow Flaws Under Biaxial Loading Conditions—Part II: Application of a Weibull Stress Analysis of the Cruciform Bend Specimen Using a Hydrostatic Stress Criterion1
Authors: Williams Paul T. , Bass B. Richard , McAfee Wallace J.
Published: July 2002

Cruciform beam fracture mechanics specimens have been developed in the Heavy Section Steel Technology Program at Oak Ridge National Laboratory to introduce a prototypic, far-field, out-of-plane biaxial bending stress component in the test section that approximates the nonlinear biaxial stresses resulting from pressurized-thermal-shock or pressure-temperature loading of a nuclear reactor pressure vessel (RPV). Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant-depth) shallow surface flaws. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. Two and three-parameter Weibull models have been calibrated using a new scheme (developed at the University of Illinois) that maps toughness data from test specimens with distinctly different levels of crack-tip constraint to a small-scale-yielding Weibull stress space. These models, with a new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the Weibull stress integral definition, have been shown to correlate the experimentally observed biaxial effect in cruciform specimens, thereby providing a scaling mechanism between uniaxial and biaxial loading states.
Model-Based Fuzzy Controller Design With Common Observability Gramian Assignment
Authors: Chang Wen-Jer
Published: July 2002

Almost all robust properties of linear systems can be related directly to properties of the controllability or observability Gramian. A model-based fuzzy controller for a class of uncertain nonlinear systems will be developed in this paper to achieve a common observability Gramian. Design of a model-based fuzzy controller begins by assigning a certain common observability Gramian. The nonlinear systems considered in this paper are represented by Takagi-Sugeno fuzzy models. An application to the inverted pendulum system will be given to demonstrate the effects of the present design method.
Thermal Effects on Polymer Laminated Steel Formability in Ironing
Authors: Huang Chen-Hsi , Schmid Steven R. , Wang Jyhwen E.
Published: July 2002

In the current manufacturing processes for can making, a time consuming and therefore expensive process involves spraying a food-contact safe polymer coating onto the can interior before filling. This process can be eliminated by using a prelaminated metal workpiece as long as the polymer will survive the manufacturing operations involved in can making. The most demanding operation in can making is ironing because of the high pressures involved as well as the necessary generation of new surface. Previous research [5] has demonstrated the feasibility of using a polymer coated steel sheet stock for can making. However, ironing is commonly performed with elevated tooling temperatures which result from friction and plastic deformation in the workpiece. As such, it is possible that the polymer could significantly soften or melt during the ironing process when tooling/workpiece contact is most intimate. In this paper, the thermal effects of hot tooling on polymer coated steel formability are explored through both experiments and mathematical models.
Orientation Specific Thermal Properties of Polyimide Film
Authors: Samuels Robert J. , Mathis Nancy E.
Published: July 2002

The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.
Die Attachment for −120°C to +20°C Thermal Cycling of Microelectronics for Future Mars Rovers—An Overview1
Authors: Kirschman Randall K. , Sokolowski Witold M. , Kolawa Elizabeth A.
Published: July 2002

Active thermal control for electronics on Mars rovers imposes a serious penalty in weight, volume, power consumption, and reliability. Thus, we propose that thermal control be eliminated for future rovers. From a functional standpoint there is no reason that the electronics could not operate over the entire temperature range of the Martian environment, which can vary from a low of ≈−90°C to a high of ≈+20°C during the Martian night and day. The upper end of this range is well within that for conventional electronics. Although the lower end is considerably below that for which conventional—even high-reliability—electronics is designed or tested, it is well established that electronic devices can operate to such low temperatures. The primary concern is reliability of the overall electronic system, especially in regard to the numerous daily temperature cycles that it would experience over the duration of a mission on Mars. Accordingly, key reliability issues have been identified for elimination of thermal control on future Mars rovers. One of these is attachment of semiconductor die onto substrates and into packages. Die attachment is critical since it forms a mechanical, thermal, and electrical interface between the electronic device and the substrate or package. This paper summarizes our initial investigation of existing information related to this issue, in order to form an opinion whether die attachment techniques exist, or could be developed with reasonable effort, to withstand the Mars thermal environment for a mission duration of approximately one earth year. Our conclusion, from a review of literature and personal contacts, is that die attachment can be made sufficiently reliable to satisfy the requirements of future Mars rovers. Moreover, it appears that there are several possible techniques from which to choose and that the requirements could be met by judicious selection from existing methods using hard solders, soft solders, or organic adhesives. Thus, die attachment does not appear to be a roadblock to eliminating thermal control for rover electronics. We recommend that this be further investigated and verified for the specific hardware and thermal conditions appropriate to Mars rovers.
Requirements for Mesh Resolution in 3D Computational Hemodynamics
Authors: Prakash Sujata , Ethier C. Ross
Published: July 2002

Computational techniques are widely used for studying large artery hemodynamics. Current trends favor analyzing flow in more anatomically realistic arteries. A significant obstacle to such analyses is generation of computational meshes that accurately resolve both the complex geometry and the physiologically relevant flow features. Here we examine, for a single arterial geometry, how velocity and wall shear stress patterns depend on mesh characteristics. A well-validated Navier-Stokes solver was used to simulate flow in an anatomically realistic human right coronary artery (RCA) using unstructured high-order tetrahedral finite element meshes. Velocities, wall shear stresses (WSS), and wall shear stress gradients were computed on a conventional “high-resolution” mesh series (60,000 to 160,000 velocity nodes) generated with a commercial meshing package. Similar calculations were then performed in a series of meshes generated through an adaptive mesh refinement (AMR) methodology. Mesh-independent velocity fields were not very difficult to obtain for both the conventional and adaptive mesh series. However, wall shear stress fields, and, in particular, wall shear stress gradient fields, were much more difficult to accurately resolve. The conventional (nonadaptive) mesh series did not show a consistent trend towards mesh-independence of WSS results. For the adaptive series, it required approximately 190,000 velocity nodes to reach an r.m.s. error in normalized WSS of less than 10 percent. Achieving mesh-independence in computed WSS fields requires a surprisingly large number of nodes, and is best approached through a systematic solution-adaptive mesh refinement technique. Calculations of WSS, and particularly WSS gradients, show appreciable errors even on meshes that appear to produce mesh-independent velocity fields.
Effects of Surface Roughness on Multi-Station Mechanical Alignment Processes
Authors: Lee Neville K. S. , Chen J. Y. , Joneja Ajay
Published: July 2002

A theoretical simulation study was performed to study how surface roughness of the workpiece and datum can affect the locating precision of multiple station manufacturing processes using a mechanical alignment system. Our analysis shows that geometric consideration, a factor that has not been treated before, is extremely important for many multi-station applications. As expected, the level of alignment precision decreases when the level of surface roughness of the workpieces increases. Our analysis also shows that the effect of the sample roughness on the level of alignment precision depends heavily on the difference in the relative positions of the datum between different workstations.
Assessment of VR Technology and its Applications to Engineering Problems
Authors: Jayaram Sankar , Vance Judy , Gadh Rajit , Jayaram Uma , Srinivasan Hari
Published: July 2002

Virtual reality applications are making valuable contributions to the field of product realization. This paper presents an assessment of the hardware and software capabilities of VR technology needed to support a meaningful integration of VR applications in the product life cycle analysis. Several examples of VR applications for the various stages of the product life cycle engineering are presented as case studies. These case studies describe research results, fielded systems, technical issues, and implementation issues in the areas of virtual design, virtual manufacturing, virtual assembly, engineering analysis, visualization of analysis results, and collaborative virtual environments. Current issues and problems related to the creation, use, and implementation of virtual environments for engineering design, analysis, and manufacturing are also discussed.
Determination of Poisson’s Ratio by Spherical Indentation Using Neural Networks—Part I: Theory
Authors: Huber N. , Konstantinidis A. , Tsakmakis Ch.
Published: July 2002

When studying analytically the penetration of an indenter of revolution into an elastic half-space use is commonly made of the fraction Er=E/1−ν2. Because of this, only Er is determined from the indentation test, while the value of ν is usually assumed. However, as shown in the paper, if plastic deformation is involved during loading, the depth-load trajectory depends on the reduced modulus and, additionally, on the Poisson ratio explicitly. The aim of the paper is to show, with reference to a simple plasticity model exhibiting linear isotropic hardening, that the Poisson ratio can be determined uniquely from spherical indentation if the onset of plastic yield is known. To this end, a loading and at least two unloadings in the plastic regime have to be considered. Using finite element simulations, the relation between the material parameters and the quantities characterizing the depth-load response is calculated pointwise. An approximate inverse function represented by a neural network is derived on the basis of these data.
The Frequency Analysis of the Crankshaft’s Speed Variation: A Reliable Tool for Diesel Engine Diagnosis
Authors: Taraza D. , Henein N. A. , Bryzik W.
Published: July 2002

The speed variation of the crankshaft may be easily and accurately measured using a shaft encoder and counting the pulses of the internal clock of the data acquisition system. If the crankshaft would be a rigid body, the variation of its angular speed could be directly correlated to the total gas-pressure torque. Actually, the variation of the crankshaft’s speed has a complex nature being influenced by the torsional stiffness of the cranks, the mass moments of inertia of the reciprocating masses and the average speed and load of the engine. Analyzing only the lower harmonic orders of the speed variation spectrum can filter out the distortions produced by the dynamic response of the crankshaft. The information carried by these harmonic orders permits to establish correlations between measurements and the average gas pressure torque of the engine, and to detect malfunctions and identify faulty cylinders.
Thermal Stability of Thermal Interface Pastes, Evaluated by Thermal Contact Conductance Measurement
Authors: Luo, Xiangcheng , Xu, and Yunsheng , Chung D. D. L.
Published: July 2002

Thermal interface pastes based on silicone, lithium doped polyethylene glycol (PEG), and sodium silicate were evaluated in their performance before and after heating up to 120°C. The thermal contact conductance of any of the pastes between copper disks decreased after heating, such that the fractional decrease was less for the silicone-based paste than the PEG-based and sodium-silicate-based pastes. Nevertheless, the conductance was lower for the silicone-based paste than the other pastes both before and after heating up to 100 cycles.
The Effect of Proximal Artery Flow on the Hemodynamics at the Distal Anastomosis of a Vascular Bypass Graft: Computational Study
Authors: Kute Stephanie M. , Vorp David A.
Published: July 2002

The formation of distal anastomotic intimal hyperplasia (IH), one common mode of bypass graft failure, has been shown to occur in the areas of disturbed flow particular to this site. The nature of the flow in the segment of artery proximal to the distal anastomosis varies from case to case depending on the clinical situation presented. A partial stenosis of a bypassed arterial segment may allow residual prograde flow through the proximal artery entering the distal anastomosis of the graft. A complete stenosis may allow for zero flow in the proximal artery segment or retrograde flow due to the presence of small collateral vessels upstream. Although a number of investigations on the hemodynamics at the distal anastomosis of an end-to-side bypass graft have been conducted, there has not been a uniform treatment of the proximal artery flow condition. As a result, direct comparison of results from study to study may not be appropriate. The purpose of this work was to perform a three-dimensional computational investigation to study the effect of the proximal artery flow condition (i.e., prograde, zero, and retrograde flow) on the hemodynamics at the distal end-to-side anastomosis. We used the finite volume method to solve the full Navier–Stokes equations for steady flow through an idealized geometry of the distal anastomosis. We calculated the flow field and local wall shear stress (WSS) and WSS gradient (WSSG) everywhere in the domain. We also calculated the severity parameter (SP), a quantification of hemodynamic variation, at the anastomosis. Our model showed a marked difference in both the magnitude and spatial distribution of WSS and WSSG. For example, the maximum WSS magnitude on the floor of the artery proximal to the anastomosis for the prograde and zero flow cases is 1.8 and 3.9 dynes/cm2, respectively, while it is increased to 10.3 dynes/cm2 in the retrograde flow case. Similarly, the maximum value of WSSG magnitude on the floor of the artery proximal to the anastomosis for the prograde flow case is 4.9 dynes/cm3, while it is increased to 13.6 and 24.2 dynes/cm3, respectively, in the zero and retrograde flow cases. The value of SP is highest for the retrograde flow case (13.7 dynes/cm3) and 8.1 and 12.1 percent lower than this for the prograde (12.6 dynes/cm3) and zero (12.0 dynes/cm3) flow cases, respectively. Our model results suggest that the flow condition in the proximal artery is an important determinant of the hemodynamics at the distal anastomosis of end-to-side vascular bypass grafts. Because hemodynamic forces affect the response of vascular endo- thelial cells, the flow situation in the proximal artery may affect IH formation and, therefore, long-term graft patency. Since surgeons have some control over the flow condition in the proximal artery, results from this study could help determine which flow condition is clinically optimal.
A New Two-Phase Flow Map and Transition Boundary Accounting for Surface Tension Effects in Horizontal Miniature and Micro Tubes
Authors: Tabatabai Ahmadali , Faghri Amir
Published: July 2002

A new flow map is proposed to emphasize the importance of surface tension in two-phase flow in horizontal miniature and micro tubes. A transition boundary based on a force balance including shear, buoyancy and surface tension forces is also proposed. The flow map is compared against a number of existing experimental data sets totaling 1589 data points. Comparison of the proposed map and model with previous models shows substantial improvement and accuracy in determining surface tension dominated regimes. Furthermore, the proposed flow map shows how each regime transition boundary is affected by surface tension.
Analysis of Radiative Heat Transfer in Complex Two-Dimensional Enclosures With Obstacles Using the Modified Discrete Ordinates Method
Authors: Sakami M. , El Kasmi A. , Charette A.
Published: July 2002

In this work, an extension of a modified discrete ordinates method recently proposed by other researchers is presented. It is intended to counter the ray effect inherent in this method. The media analyzed are absorbing, emitting and isotropically or anisotropically scattering and the enclosure geometry is arbitrary. Cases with obstructions are emphasized. The radiative intensity is broken into two parts: the wall-related intensity and the medium-related intensity. The former is treated separately by rigorous integration over the entire solid boundary. A new differencing scheme based on quadrangular grids is also proposed and used for the treatment of the medium-related intensity. Results confirm that the proposed method is a good general remedy for anomalies caused by the ray effect due to the geometry.