bluuebunny/crossref_metadata_2025 huggingface dataset:
European car makers and their suppliers: changes at the interface
Authors: McIvor R.T. , Humphreys P.K. , McAleer W.E.
Published: July 2002

The objective of this paper is to examine changes in the European car industry and in particular the impact these changes are having on the car makers and their relationships with their suppliers. With excess production capacity and the poor outlook for car sales, the European car industry requires structural changes to balance supply and demand. In an effort to address these problems, the car makers are re‐appraising their relations with their suppliers. They are now pursuing more intensive and interactive relationships with their suppliers, collaborating in areas such as new product development, supplier development, and information sharing on a range of issues. However, there is evidence to illustrate that there is a lack of trust between the car makers and their suppliers. It is argued that if the European car makers are to compete globally then there will have to be more trust and co‐operation between the car makers and the components industry.
Horizontal thermal convection in a shallow cavity: oscillatory regimes and transition to chaos
Authors: Bucchignani Edoardo , Mansutti Daniela
Published: July 2002

We develop a numerical analysis of the buoyancy driven natural convection of a fluid in a three dimensional shallow cavity (4 ⋅ 1 ⋅ 1) with a horizontal gradient of temperature along the larger dimension. The fluid is a liquid metal (Prandtl number equal to 0. 015) while the Grashof number (Gr) varies in the range 100,000‐300,000. The Navier‐Stokes equations in vorticity‐velocity formulation have been integrated by means of a linearized fully implicit scheme. The evaluation of fractal dimension of the attractors in the phase space has allowed the detection of the chaotic regime. The Ruelle‐Takens bifurcation sequence has been observed as mechanism for the transition to chaos: the quasi periodic regime with three incommensurate frequencies is the instability mechanism responsible for the transition to chaos. Physical experiments confirm the existence of this scenario.
A fundamental study of combined free and forced convective heat transfer from a vertical plate followed by a backward step
Authors: Kishinami Koki , Saito Hakaru , Suzuki Jun , Hamza H. Ali Ahmed , Umeki Hisashi , Kitano Noriyuki
Published: July 2002

Combined forced and free laminar convective heat transfer on a vertical plate with a backward‐facing step has been studied numerically and experimentally, considering the effects of the interaction between the buoyancy and inertia forces which play a significant role in this phenomenon with the step‐geometry factor of d/L. The convective heat transfer behavior in connection with the reattachment and recirculation flows appearing in the step region has been investigated based on the numerical calculations and Mach‐Zehnder interferometer measurement under the wide range of the thermal condition. The behaviors of local Nusselt number NuL, velocity and temperature boundary layers and streamline fields in the recirculating region have been discussed for the various parameters of Grashof number GrL, Reynolds number ReL and the geometry factor d/L. The characteristic behavior of this convection heat transfer, including the vortex flow mode in the recirculating region and the unstable fluctuating mode near the reattaching point appearing at the specific condition, has been clarified numerically and experimentally by introducing the generalized coupling parameter GrL/ReL2 and geometry factor d/L.
Transnational forest fire fighting: the Malaysian experience
Authors: Said Aini Mat , Fakhur’l‐Razi Ahmadun , Daud Mohamed , Hamdan Wahid Mohammad
Published: July 2002

The forest fire experiences of Malaysia, Singapore, the Philippines and Thailand in 1997 are reviewed. The problems of transnational co‐operation in such cases are examined and the resulting joint lessons are presented.
Accrediting teaching in higher education – voices crying in the wilderness!
Authors: Luby Antony
Published: July 2002

States that one of the outcomes of globalization and the increasing competition between higher education institutions (HEIs) has been a move towards the accreditation of teaching in higher education. HEIs in other countries may be interested to learn from the UK experience where there has been much acrimony “behind the scenes”, as various associations and organizations have battled for power. Unfortunately, the main losers in this battle have been the “chalkface academics” whose collective voice has been “crying in the wilderness”. This article attempts to redress the situation by reiterating the main findings of a national research project on accreditation; and it concludes by evaluating progress to date from the perspective of 18 months after the completion of the study.
Electronic courses: old wine in new bottles?
Authors: Saunders Gary , Weible Rick
Published: July 2002

Offerings of electronic courses and degrees are growing at a surprising rate. Some have surmised that E courses represent the future for higher education and that the traditional university may soon be a relic of the past: do E courses represent a significant improvement over traditional pedagogy for educating students? In this context, 305 questionnaires were sent by e‐mail to accounting chairpersons in the USA. A total of 94 usable responses was received. Nearly 65 per cent of the respondents indicated that E courses are simply correspondence courses presented with new technology. Those who view E courses as correspondence courses are more negative on offering E courses in university programs or offering degrees through the completion of only E courses. They are also more restrictive with E courses, favoring the proctoring of exams and requiring students to come to campus as part of the E course. Additionally, they tended to agree that “the student‐to‐student and the student‐to‐instructor interaction that are missing in E courses makes them less valuable to the student.” Instead of viewing E courses and E degrees as the “university of the future”, they see them as adjuncts to university programs just as correspondence courses have been for decades.
An audit of psychiatric case notes in relation to antipsychotic medication and information giving
Authors: Bowler N. , Moss Susanna , Winston Mark , Coleman M.
Published: July 2002

This paper reports upon a Welsh Office funded “clinical effectiveness” project. The project aimed to produce evidence‐based practice guidelines for depot neuroleptic medication. An audit was conducted to establish current practice regarding the provision of illness and treatment specific information to out‐patients and their informal carers. Sixty‐five patients’ case‐notes, under the care of a single community mental health team were examined for evidence of the type, nature and frequency of information given to patients receiving typical depot neuroleptic medications. Service guidelines were produced and are presented.
Product‐conformation‐driven ligation of peptides by V8 protease
Authors: Srinivasulu Sonati , Acharya A. Seetharama
Published: July 2002

Organic co‐solvent‐induced secondary conformation of α17–40 of human hemoglobin facilitates the splicing of E30‐R31 in a mixture of its complementary segments by V8 protease. The amino acid sequence of α17–40 has been conceptualized by the general structure FRI‐EALER‐FRII and the pentapeptide sequence EALER playing a major role in inducing the α‐helical conformation. The primary structure of α17–40 has been engineered in multiple ways to perturb one, two, or all three regions and the influence of the organic co‐solvent‐induced conformation and the concomitant resistance of E30‐R31 peptide bond to V8 protease digestion has been investigated. The central pentapeptide (EALER), referred to here as splicedon,3

Splicedon is a pentapeptide sequence (EALER) sandwiched between the two peptides with intrinsic α‐helical potential and provides the resistance to the spliced peptide bond E‐R by V8 protease once it is integrated as a contiguous segment and the peptide folds into an α‐helical conformation.

appears to dictate a primary role in facilitating the splicing reaction. When the same flanking regions are used, (1) splicedons that carry amino acid residues of low α‐helical potential, for example G at position 2 or 3 of the splicedon, generate a conformational trap of very low thermodynamic stability, giving an equilibrium yield of only 3%–5%; (2) splicedons with amino acid residues of good α‐helical potential generate a conformational trap of medium thermodynamic stability and give an equilibrium yield of 20%–25%; (3) the splicedons with amino residues of good α‐helical potential and also an amino acid that can generate an i, i + 4 side‐chain carboxylate‐guanidino (amino) interaction, a conformational trap of maximum thermodynamic stability is generated, giving an equilibrium yield of 45%–50%; and (4) the thermodynamic stability of the conformational trap of the spliced peptide is also influenced by the amino acid composition of the flanking regions. The V8 protease resistance of the spliced peptide bond is not a direct correlate of the amount of α‐helical conformation induced into the product. The results of this study reflect the unique role of the splicedon in translating the organic co‐solvent‐induced product conformation as a site‐specific stabilization of the spliced peptide bond. It is speculated that the splicedon with higher α‐helical potential as compared to either one of the flanking regions achieves this by integrating its potential with that of the flanking region(s). Exchange of flanking regions with the products of other V8 protease–catalyzed splicing reactions will help to establish the general primary structural requirements of this class of splicing reactions and facilitate their application in modular construction of proteins.
Protein–protein docking with multiple residue conformations and residue substitutions
Authors: Lorber David M. , Udo Maria K. , Shoichet Brian K.
Published: July 2002

The protein docking problem has two major aspects: sampling conformations and orientations, and scoring them for fit. To investigate the extent to which the protein docking problem may be attributed to the sampling of ligand side‐chain conformations, multiple conformations of multiple residues were calculated for the uncomplexed (unbound) structures of protein ligands. These ligand conformations were docked into both the complexed (bound) and unbound conformations of the cognate receptors, and their energies were evaluated using an atomistic potential function. The following questions were considered: (1) does the ensemble of precalculated ligand conformations contain a structure similar to the bound form of the ligand? (2) Can the large number of conformations that are calculated be efficiently docked into the receptors? (3) Can near‐native complexes be distinguished from non‐native complexes? Results from seven test systems suggest that the precalculated ensembles do include side‐chain conformations similar to those adopted in the experimental complexes. By assuming additivity among the side chains, the ensemble can be docked in less than 12 h on a desktop computer. These multiconformer dockings produce near‐native complexes and also non‐native complexes. When docked against the bound conformations of the receptors, the near‐native complexes of the unbound ligand were always distinguishable from the non‐native complexes. When docked against the unbound conformations of the receptors, the near‐native dockings could usually, but not always, be distinguished from the non‐native complexes. In every case, docking the unbound ligands with flexible side chains led to better energies and a better distinction between near‐native and non‐native fits. An extension of this algorithm allowed for docking multiple residue substitutions (mutants) in addition to multiple conformations. The rankings of the docked mutant proteins correlated with experimental binding affinities. These results suggest that sampling multiple residue conformations and residue substitutions of the unbound ligand contributes to, but does not fully provide, a solution to the protein docking problem. Conformational sampling allows a classical atomistic scoring function to be used; such a function may contribute to better selectivity between near‐native and non‐native complexes. Allowing for receptor flexibility may further extend these results.
Investment and Arbitrage Opportunities with Short Sales Constraints
Authors: Carassus Laurence , Jouini Elyès
Published: July 2002

In this paper we consider a family of investment projects defined by their deterministic cash flows. We assume stationarity—that is, projects available today are the same as those available in the past. In this framework, we prove that the absence of arbitrage opportunities is equivalent to the existence of a discount rate such that the net present value of all projects is nonpositive if the projects cannot be sold short and is equal to zero otherwise. Our result allows for an infinite number of projects and for continuous as well as discrete cash flows, generalizing similar results established by Cantor and Lippman (1983, 1995) and Adler and Gale (1997) in a discrete time framework and for a finite number of projects.
Calcium release and intramembranous charge movement in frog skeletal muscle fibres with reduced (< 250 μM) calcium content
Authors: Pape Paul C. , Carrier Nicole
Published: July 2002

It is generally accepted that activation of voltage sensors in the T‐tubular membranes is a critical step of excitation‐contraction coupling in skeletal muscle. The purpose of this study was to evaluate further whether the Qγ component (delayed [hump] component) of the intramembranous charge movement current (Icm) results from movement of these voltage sensors. Ca2+ release and Icm were measured in voltage‐clamped frog cut fibres mounted in a double Vaseline‐gap chamber. In order to reduce effects of Ca2+ feedback mechanisms, the calcium content of the sarcoplasmic reticulum (SR) during rest was reduced to < 250 μm (referred to volume of myoplasm) and maintained approximately constant. The early (Qβ) and Qγ components of charge movement were estimated by fitting the sum of two Boltzmann functions to the total steady‐state intramembranous charge vs. voltage data. The average voltage steepness factor (k) and half‐maximal voltage (V‐) for Qγ were 4.3 and −57.4 mV (n= 6), respectively. The SR membrane permeability for Ca2+ release was assessed when a constant amount of calcium remained in the SR (usually about 60 μm). A single Boltzmann function fitted to these data gave values on average for k and V‐ of 4.7 and −45.3 mV, respectively. The similarity of the values of k for Qγ and Ca2+ release supports the idea that Qγ reflects movement of voltage sensors for Ca2+ release. The greater value of V‐ for Ca2+ release compared to Qγ is consistent with multi‐state models of the voltage sensor involving movement of Qγ charge during non‐activating transitions.
Yield Criteria for the Elastic-Plastic Design of Tubesheets With Triangular Penetration Pattern
Authors: Reinhardt Wolf D.
Published: July 2002

To perform an elastic-plastic finite element analysis of a tubesheet, the anisotropic stiffness and yield properties of the perforated region are represented by an equivalent solid plate. Traditional anisotropic yield criteria (like Hill’s criterion) do not give accurate predictions under general biaxial loading because they neglect the plastic compressibility of the perforated material. A compressible-anisotropic second-order yield criterion is derived which can model both the actual out-of-plane and in-plane behavior. Using an equivalent stress vector, the in-plane symmetry properties of the second-order compressible model are examined for a triangular penetration pattern. Generally, the tubesheet symmetry is not precisely reflected by this model. Additional planes of symmetry can be introduced with a higher-order yield function. A fourth-order yield function with the required symmetry properties is presented which is in excellent agreement with the response of a finite element, elastic-plastic model of a tubesheet ligament under in-plane biaxial loading.
Design of Robust High-Speed Motion Controller for a Plant With Actuator Saturation
Authors: Choi Hyun-Taek , Kim Bong Keun , Suh Il Hong , Chung Wan Kyun
Published: July 2002

A robust high-speed motion controller is proposed. The proposed controller consists of the proximate time optimal servomechanisms (PTOS) for high-speed motion, disturbance observer (DOB) for robustness, friction compensator, and saturation handling element. In the proposed controller, DOB basically provides the chance to apply PTOS to nondouble integrator systems by drastically reducing disturbances as well as unwanted signals due to difference between real system and the double integrator model. But, in DOB-based systems, if control input is saturated due to control input of PTOS and/or DOB, overall system stability cannot be guaranteed, which is first found and analyzed in this paper. To solve this problem, robust stability and internal stability conditions of DOB-based system are derived. It is also shown that DOB could violate the internal stability, when the control input is saturated. Eventually, a simple saturation handling element is inserted to maintain internal stability of overall system. Also, we explain that our two saturation handling methods, i.e., Additional Saturation Element (ASE) and Self Adjusting Saturation (SAS) are the equivalent solutions of saturation problem to maintain internal stability. The stability and performances of the proposed controller are verified through numerical simulations and experiments using a precision linear motor system. [S0022-0434(00)01103-5]
Experimental Investigations on a Permanent Magnet Brushless DC Motor Fed by a PV Array for a Water Pumping System
Authors: Putta Swamy C. L. , Singh Bhim , Singh B. P. , Murthy S. S.
Published: July 2002

This paper describes the experimental study carried out on a Permanent Magnet Brushless DC (PMBLDC) motor coupled to a pump load powered by a Photo Voltaic (PV) Array for a Water Pumping System. A simple low cost controller has been designed and developed without any current and position sensors. This drastically reduces the over all cost of the drive system. This controller is used to test the dynamic behavior of the PMBLDC motor drive system. The mathematical model of the system is developed with a view to carry out a comparison between experimental and simulated response of the drive system. The necessary computer algorithm is developed to analyze the performance under different conditions of varying solar irradiance for a pump load. The developed state space equations are simulated to obtain the performance characteristics which are also verified by conducting suitable experiments on the developed system. [S0199-6231(00)01002-9]
Analysis of Material Nonlinear Problems Using Pseudo-Elastic Finite Element Method
Authors: Desikan V. , Sethuraman Raju
Published: July 2002

A method based on linear elastic finite element analysis is presented for stress field determination of elasto-plastic problems. Hencky’s total deformation theory is used to define effective material parameters, which are treated as spatial field variables and considered to be functions of final state of equilibrium stress and material properties. These effective material parameters are obtained in an iterative manner using strain-controlled projection method, arc-length method, and Neuber rule applied on experimental uniaxial tension test curve. Three problems of von Mises material are considered to illustrate the application of the proposed method: a thick-walled cylinder subjected to internal pressure characterized by general work-hardening behavior, a V-notch specimen subjected to remote tensile load having elastic-perfectly plastic behavior, and a rotating disk with material having elastic linear work-hardening behavior. Obtained results for all the cases are compared with standard nonlinear finite element results and are found to be in good agreement. [S0094-9930(00)00104-9]
Plastic Bifurcation in the Triaxial Confining Pressure Test
Authors: Durban D. , Papanastasiou P.
Published: July 2002

Bifurcations of a circular cylinder are studied, within the context of the triaxial confining pressure test, for pressure sensitive solids. Material response is modeled by large strain versions of flow and deformation theories of plasticity in conjunction with the Drucker-Prager solid. An axially symmetric deformation pattern is assumed prior to bifurcation and only diffuse modes within the elliptic regime are considered. The governing equations are solved analytically in terms of Bessel functions and a search procedure is employed to trace bifurcation loads. Deformation theory predicts critical stresses which are consistently below flow theory results, and provides practical upper bounds on experimentally observed values of peak stresses. [S0021-8936(00)01403-3]
A Navier–Stokes Analysis of the Stall Flutter Characteristics of the Buffum Cascade
Authors: Weber Stefan , Platzer Max F.
Published: July 2002

Numerical stall flutter prediction methods are much needed, as modern jet engines require blade designs close to the stability boundaries of the performance map. A Quasi-3D Navier–Stokes code is used to analyze the flow over the oscillating cascade designed and manufactured by Pratt & Whitney, and studied at the NASA Glenn Research Center by Buffum et al. The numerical method solves for the governing equations with a fully implicit time-marching technique in a single passage by making use of a direct-store, periodic boundary condition. For turbulence modeling, the Baldwin–Lomax model is used. To account for transition, the criterion to predict the onset location suggested by Baldwin and Lomax is incorporated. Buffum et al. investigated two incidence cases for three different Mach numbers. The low-incidence case at a Mach number of 0.5 exhibited the formation of small separation bubbles at reduced oscillation frequencies of 0.8 and 1.2. For this case the present approach yielded good agreement with the steady and oscillatory measurements. At high incidence at the same Mach number of 0.5 the measured steady-state pressure distribution and the separation bubble on the upper surface was also found in good agreement with the experiment. But computations for oscillations at high incidence failed to predict the negative damping contribution caused by the leading edge separation. [S0889-504X(00)01304-0]
Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress
Authors: Underwood John H. , Glennon Michael J.
Published: July 2002

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.
Hypersonic Flow Heat Transfer Prediction Using Single Equation Turbulence Models
Authors: Goldberg U.
Published: July 2002

Three single equation turbulence models were applied to a test case of a Mach 9 flow over a 38 deg ramp. None of the models have been optimized to high-speed flows. Results indicate that the Rt closure outperforms both the Spalart-Allmaras and Menter’s models in predicting this flow. Since the Rt model’s formulation is also topography-parameter-free, it seems to be the best choice for use in hypersonic heat transfer prediction within the single equation closure family.
An Innovative Device for Passive Control of Surge in Industrial Compression Systems
Authors: Arnulfi Gianmario L. , Giannattasio Pietro , Micheli Diego , Pinamonti Piero
Published: July 2002

The present paper reports a numerical–experimental study on the dynamic behavior of a compression system based on a multistage centrifugal blower and fitted with an innovative device for the dynamic suppression of surge instability. The control device is of passive type and is based on the aeroelastic coupling of the basic compression system with a hydraulic oscillator. The controlled system is modeled at first by using a nonlinear lumped parameter approach. The simulated system dynamics within a wide range of operating conditions allows a parametric analysis to be performed and the optimal values of the control parameters to be singled out. Such optimal values are then used to design the hydraulic oscillator, which results in a technically feasible and very simple configuration. Finally, experimental tests are carried out on the compression plant with and without the passive control device, which demonstrate the effectiveness of the proposed control system in suppressing surge instabilities, at least within the limits predicted by the numerical simulation.
A Numerical Model to Predict the Thermal and Psychrometric Response of Electronic Packages
Authors: Vargas J. V. C. , Stanescu G. , Florea R. , Campos M. C.
Published: July 2002

This paper introduces a general computational model for electronic packages, e.g., cabinets that contain electronic equipment. A simplified physical model, which combines principles of classical thermodynamics and heat transfer, is developed and the resulting three-dimensional differential equations are discretized in space using a three-dimensional cell centered finite volume scheme. Therefore, the combination of the proposed simplified physical model with the adopted finite volume scheme for the numerical discretization of the differential equations is called a volume element model (VEM). A typical cabinet was built in the laboratory, and two different experimental conditions were tested, measuring the temperatures at forty-six internal points. The proposed model was utilized to simulate numerically the behavior of the cabinet operating under the same experimental conditions. Mesh refinements were conducted to ensure the convergence of the numerical results. The converged mesh was relatively coarse (504 cells), therefore the solutions were obtained with low computational time. The model temperature results were directly compared to the steady-state experimental measurements of the forty-six internal points, with good quantitative and qualitative agreement. Since accuracy and low computational time are combined, the model is shown to be efficient and could be used as a tool for simulation, design, and optimization of electronic packages.
Steady-State Pleural Fluid Flow and Pressure and the Effects of Lung Buoyancy
Authors: Haber Richard , Grotberg James B. , Glucksberg Matthew R. , Miserocchi Giuseppe , Venturoli Daniele , Del Fabbro Massimo , Waters Christopher M.
Published: July 2002

Both theoretical and experimental studies of pleural fluid dynamics and lung buoyancy during steady-state, apneic conditions are presented. The theory shows that steady-state, top-to-bottom pleural-liquid flow creates a pressure distribution that opposes lung buoyancy. These two forces may balance, permitting dynamic lung floating, but when they do not, pleural–pleural contact is required. The animal experiments examine pleural-liquid pressure distributions in response to simulated reduced gravity, achieved by lung inflation with perfluorocarbon liquid as compared to air. The resulting decrease in lung buoyancy modifies the force balance in the pleural fluid, which is reflected in its vertical pressure gradient. The data and model show that the decrease in buoyancy with perfluorocarbon inflation causes the vertical pressure gradient to approach hydrostatic. In the microgravity analogue, the pleural pressures would be toward a more uniform distribution, consistent with ventilation studies during space flight. The pleural liquid turnover predicted by the model is computed and found to be comparable to experimental values from the literature. The model provides the flow field, which can be used to develop a full transport theory for molecular and cellular constituents that are found in pleural fluid.
Fatigue Performance of High-Pressure Waterjet-Peened Aluminum Alloy
Authors: Ramulu M. , Kunaporn S. , Jenkins M. , Hashish M. , Hopkins J.
Published: July 2002

An experimental study of high-pressure waterjet peening on 7075-T6 aluminum alloy was conducted to investigate the effects of waterjet on high-cycle fatigue life and fatigue crack growth. Unnotched hourglass-shaped circular cross section test specimens were fatigue tested in completely reversed rotating bending R=Smin/Smax=−1 to determine fatigue life behavior (S-N curves). Single-edge-notched flat tensile test specimens were tested in the tension-tension fatigue crack growth tests R=Smin/Smax=0.1 to determine fatigue crack propagation behavior (da/dN versus ΔK). Surface characteristics and fracture surfaces were evaluated by scanning electron microscopy (SEM). Results show that waterjet peening can increase high-cycle fatigue life, delay fatigue crack initiation, and decrease the rate of fatigue crack propagation.
Axial Vibration of a Padded Annulus on a Semi-Infinite Viscoelastic Medium
Authors: Guzina B. B. , Fata F. Nintcheu
Published: July 2002

The vibratory punch problem for a viscoelastic half-space indented by a padded annular disk is investigated. By virtue of transform methods, the problem is formulated as a set of triple integral equations which are reducible to a Fredholm integral equation of the second kind. In the formulation, the response of a thin buffer which regularizes the load transfer to the semi-infinite solid is approximated via a plane stress-type solution. A set of numerical results is included to demonstrate the effect of padding characteristics on the dynamic system response. Apart from providing an interpretation tool for the nondestructive testing methods involving buffered annular loading systems, the present solution can be used as an effective approximation to the corresponding rigid-punch problem which has so far eluded a rigorous mathematical treatment.
Three Dimensional Absolute Nodal Coordinate Formulation for Beam Elements: Theory
Authors: Shabana Ahmed A. , Yakoub Refaat Y.
Published: July 2002

The description of a beam element by only the displacement of its centerline leads to some difficulties in the representation of the torsion and shear effects. For instance such a representation does not capture the rotation of the beam as a rigid body about its own axis. This problem was circumvented in the literature by using a local coordinate system in the incremental finite element method or by using the multibody floating frame of reference formulation. The use of such a local element coordinate system leads to a highly nonlinear expression for the inertia forces as the result of the large element rotation. In this investigation, an absolute nodal coordinate formulation is presented for the large rotation and deformation analysis of three dimensional beam elements. This formulation leads to a constant mass matrix, and as a result, the vectors of the centrifugal and Coriolis forces are identically equal to zero. The formulation presented in this paper takes into account the effect of rotary inertia, torsion and shear, and ensures continuity of the slopes as well as the rotation of the beam cross section at the nodal points. Using the proposed formulation curved beams can be systematically modeled.
The Exact One-Dimensional Theory for End-Loaded Fully Anisotropic Beams of Narrow Rectangular Cross Section
Authors: Ladeve`ze P. , Simmonds J. G.
Published: July 2002

The exact theory of linearly elastic beams developed by Ladeve`ze and Ladeve`ze and Simmonds is illustrated using the equations of plane stress for a fully anisotropic elastic body of rectangular shape. Explicit formulas are given for the cross-sectional material operators that appear in the special Saint-Venant solutions of Ladeve`ze and Simmonds and in the overall beamlike stress-strain relations between forces and a moment (the generalized stress) and derivatives of certain one-dimensional displacements and a rotation (the generalized displacement). A new definition is proposed for built-in boundary conditions in which the generalized displacement vanishes rather than pointwise displacements or geometric averages.
Computational Evaluation of the Periodic Performance of a NACA 0012 Fitted With a Gurney Flap
Authors: Date James C. , Turnock Stephen R.
Published: July 2002

A detailed computational investigation into the periodic two-dimensional performance of a NACA 0012 section fitted with 2 and 4 percent h/c Gurney flaps operating at a Reynolds number of 0.85×106 is presented. The aim of the work was to determine the suitability of the incompressible Reynolds-averaged Navier-Stokes (RANS) formulation in modeling the vortex shedding experienced by lifting sections with blunt, sharp edged features. In particular, whether under-converged steady state calculations could be used for section design performance evaluation in place of the computationally intensive time accurate flow simulations. Steady, periodic, and time-averaged two-dimensional lift and drag coefficients, as well as vortex shedding frequency, were predicted and compared with the available experimental data. Reasonable agreement was found, once sufficiently fine grids had been generated, and the correct time step determined for the time accurate simulations.
Finding Approximate Shape Regularities for Reverse Engineering
Authors: Langbein F. C. , Mills B. I. , Marshall A. D. , Martin R. R.
Published: July 2002

Current reverse engineering systems can generate boundary representation (B-rep) models from 3D range data. Such models suffer from inaccuracies caused by noise in the input data and algorithms. The quality of reverse engineered geometric models can be improved by finding candidate shape regularities in such a model, and constraining the model to meet a suitable subset of them, in a post-processing step called beautification. This paper discusses algorithms to detect such approximate regularities in terms of similarities between feature objects describing properties of faces, edges and vertices, and small groups of these elements in a B-rep model with only planar, spherical, cylindrical, conical and toroidal faces. For each group of similar feature objects they also seek special feature objects which may represent the group, e.g. an integer value which approximates the radius of similar cylinders. Experiments show that the regularities found by the algorithms include the desired regularities as well as spurious regularities, which can be limited by an appropriate choice of tolerances.
Heat Transfer in a Two-Pass Rectangular Rotating Channel With 45-deg
Angled Rib Turbulators
Authors: Azad Gm S. , Uddin Mohammad J. , Han Je-Chin , Moon Hee-Koo , Glezer Boris
Published: July 2002

Experimental heat transfer results are presented in a two-pass rectangular channel (aspect ratio=2:1) with smooth and ribbed surfaces for two channel orientations (90 and 135 deg to the direction of rotational plane). The rib turbulators are placed on the leading and trailing sides at an angle 45 deg to the main stream flow. Both 45-deg parallel and cross rib orientations are studied. The results are presented for stationary and rotating cases at three different Reynolds numbers of 5000, 10,000, and 25,000, the corresponding rotation numbers are 0.21, 0.11, and 0.04. The rib height to hydraulic diameter ratio (e/D) is 0.094; the rib pitch-to-height ratio (P/e) is 10 and the inlet wall-to-coolant density ratio (Δρ/ρ) is maintained at 0.115 for all surfaces in the channel. Results show that the rotating ribbed wall heat transfer coefficients increase by a factor of 2 to 3 over the rotating smooth wall results. The heat transfer from the first pass trailing and second pass leading surfaces are enhanced by rotation. However, the first pass leading and the second pass trailing sides show a decrease in heat transfer with rotation. The result show that 45-deg parallel ribs produce a better heat transfer augmentation than 45-deg cross ribs, and a 90-deg channel orientation produces higher heat transfer effect over a 135-deg orientation.
A Comparison of Rotordynamic-Coefficient Predictions for Annular Honeycomb Gas Seals Using Three Different Friction-Factor Models
Authors: D’Souza Rohan J. , Childs Dara W.
Published: July 2002

A two-control-volume bulk-flow model is used to predict rotordynamic coefficients for an annular, honeycomb-stator/smooth-rotor gas seal. The bulk-flow model uses Hirs’ turbulent-lubrication model, which requires a friction factor model to define the shear stresses at the rotor and stator wall. Rotordynamic coefficients predictions are compared for the following three variations of the Blasius pipe-friction model: (i) a basic model where the Reynolds number is a linear function of the local clearance, fs=ns Rems (ii) a model where the coefficient is a function of the local clearance, and (iii) a model where both the coefficient and exponent are functions of the local clearance. The latter models are based on data that shows the friction factor increasing with increasing clearances. Rotordynamic-coefficient predictions shows that the friction-factor-model choice is important in predicting the effective-damping coefficients at a lower frequency range (60∼70 Hz) where industrial centrifugal compressors and steam turbines tend to become unstable. At a higher frequency range, irrespective of the friction-factor model, the rotordynamic-coefficient predictions tend to coincide. Blasius-based Models which directly account for the observed increase in stator friction factors with increasing clearance predict significantly lower values for the destabilizing cross-coupled stiffness coefficients.
Influence of Friction Damping on Workpiece-Fixture System Dynamics and Machining Stability
Authors: Fang B. , DeVor R. E. , Kapoor S. G.
Published: July 2002

In this paper, a dynamic model that considers the vibrations of both the workpiece and fixture elements in order to accurately predict the friction damping over a wide range of clamping forces has been developed. The model is established based on the theory of variational inequality and solved via a nonlinear FEM. It is shown that the model is capable of predicting the system dynamics over a wide range of clamping forces. It is also demonstrated that the increasing then decreasing trend of the damping ratio caused by “interface locking” is due to the relative velocity change at the contact interface. With multiple contact interfaces, the “locking” occurs sequentially. Finally, the model is used to study the influence of friction damping on machining process stability.
XML Representation of STEP Schemas and Data
Authors: Lubell Joshua , Frechette Simon
Published: July 2002

The first Technical Note in this series [1] introduced the international standard ISO 10303, informally known as STEP (Standard for the Exchange of Product Model Data). Subsequent Technical Notes discussed various issues faced by users of STEP and how the ISO TC184/SC4 committee is addressing these issues. This article discusses the representation of STEP data using the Extensible Markup Language (XML). We begin by presenting XML’s advantages as an exchange medium for STEP. We then discuss some of the issues involved in designing an XML exchange mechanism for STEP and conclude with an update of SC4’s STEP/XML activities.
Melan’s Problems With Weak Interface
Authors: Lenci S.
Published: July 2002

The problem of a fiber attached to an infinite sheet (Melan’s problem) has been reconsidered under the hypothesis that the adherence between the two bodies is not perfect. We have assumed that the link is guaranteed by the so-called “weak interface,” i.e., we have supposed that the jump of the displacement is linearly proportional to the interface stress. The solutions of (i) the case with a concentrated force acting on the fiber and (ii) the case of the redistribution of stresses as a consequence of the rupture of the fiber have been obtained in closed form. We have discussed how the interface stiffness k influences the solutions and, in particular, the interfacial stress. Emphasis is placed on determining how the zone of influence of the applied load is modified by k. Approximate (though accurate) simple expressions for the length of the zone of influence are given and discussed. [S0021-8936(00)01001-1]
Impinging Jet Boiling of a Fluorinert Liquid on a Foil Heater Array
Authors: Nakayama Wataru , Behnia Masud , Mishima Hiroaki
Published: July 2002

An experimental study of forced convection in impinging flow, using fluorocarbon FX3250 and a simulated electronic chip, was performed. A test section consisting of a 35 mm long, 1 mm wide slot nozzle in a 2 mm thick plate offset 2 mm from the heat source was used. The simulated chip array consisted of five foil strip (4 mm wide) heaters, positioned with the center strip directly beneath the slot nozzle. The velocity of the coolant was varied from 0.53 to 5 m/s, and the subcooling in the range from 2 to 21 K. The experiments were conducted focusing on two cases. First, only the center strip was heated. Second, all the heaters were energized, and the strip-by-strip variations of heat transfer were measured. The critical heat flux (CHF) on the center strip, determined by sensing the onset of oscillations and subsequent rapid rise of foil temperatures, was found considerably lower than those predicted by the existing correlations. It is pointed out that the thermal mass of the test heater could be an important factor for the CHF. The heat transfer behavior of other strips showed channel-flow or jet-impingement mode depending on the strip location and the coolant flow rate. [S1043-7398(00)00202-4]
Rayleigh Light Scattering Measurements of Transient Gas Temperature
in a Rapid Chemical Vapor Deposition Reactor
Authors: Horton J. F. , Peterson J. E.
Published: July 2002

A laser-induced Rayleigh light scattering (RLS) system was used to measure transient gas temperatures in a simulated rapid chemical vapor deposition (RCVD) reactor. The test section geometry was an axisymmetric jet of carrier gas directed down, impinging on a heated wafer surface. RLS was used to measure instantaneous gas temperature at several locations above the wafer as it was heated from room temperature to 475 K. Gas flow rate and wafer temperature correspond to jet Reynolds number Rei=60, wafer maximum Grashof number GrH=4.4×106, and maximum mixed convection parameter GrH/Rei2=1200; all conditions typical of impinging jet reactors common in the numerical literature. Uncertainty of RLS transient temperature from a propagated error analysis was ±2–4 K. Peak gas temperature fluctuations were large (in the order of 25 to 75 °C). Both flow visualization and RLS measurements showed that the flow field was momentum dominated prior to heating initiation, but became unstable by GrH/Rei2=5. It then consisted of buoyancy-induced plumes and recirculations. Up to the peak wafer temperature, the flow field continued to be highly three-dimensional, unsteady, and dominated by buoyancy. RLS measurements are shown to provide information on carrier gas instantaneous temperature and flow field stability, both critical issues in RCVD processing. [S0022-1481(00)02401-4]
Local Approximation of the Efficient Frontier in Robust Design
Authors: Zhang Jinhuan , Wiecek Margaret M. , Chen Wei
Published: July 2002

The problem of robust design is treated as a bi-objective optimization problem in which the performance mean and variation are optimized and minimized, respectively. A method for deriving a utility function as a local approximation of the efficient frontier is presented and investigated at different locations of candidate solutions, with different ranges of interest, and for efficient frontiers with both convex and nonconvex behaviors. As an integral part of the interactive robust design procedure earlier proposed by the authors, the method assists designers in adjusting the preference structure and exploring alternative efficient robust design solutions. It eliminates the need of solving the bi-objective problem repeatedly using new preference structures, which is often computationally expensive. Though demonstrated for robust design problems, the principle is also applicable to any bi-objective optimization problem. [S1050-0472(00)00702-9]
Determination of Optimal Machining Conditions: A Coupled Uncertainty Model
Authors: Rao S. S. , Chen Li
Published: July 2002

The problem of selecting optimal machining conditions, where the formulation involves the use of empirical relations, is considered. Since both randomness and fuzziness are associated with empirical relations, a coupled uncertainty model is proposed for manipulating these uncertainties. Equations are derived to establish the interrelation between the two types of uncertainties present in the objective functions and constraints of the optimization process. This permits a systematic handling of fuzziness in terms of randomness that is usually associated with experiments. The computational aspects of the approach are illustrated by two numerical examples dealing with the optimization of machining processes. [S1087-1357(00)70501-6]
Sodium Salts of Chlorine Oxyacid Anions, Cl(+7), Perchlorate, XPS Comparison Spectra
Authors: Beard Bruce C.
Published: July 2002

High quality sodium perchlorate has been analyzed as one in a series of chlorine-oxy anion sodium salts, Chloride to Perchlorate. The spectra include survey and high resolution scans over the major photopeaks, the sodium Auger transitions and the valence band of the compound. Several references have been listed as additional sources of information of the nature of these materials and previous XPS analyses [see R. Manne, J. Chem. Phys. 46, 4645 (1967); R. G. Copperthwaite, J. Chem. Soc. Dalton Trans. 1977, 1117; R. Prins and T. Navakov, Chem. Phys. Lett. 9, 593 (1971); R. Prins, J. Chem. Phys. 61, 2580 (1974); and F. Solymosi, Structure and Stability of Salts of Halogen Oxyacids in the Solid Phase (Wiley–Interscience, New York, 1977)].
Interrelationships between process parameters, structure, and properties of CVD tungsten and tungsten–rhenium alloys
Authors: Holman William R. , Huegel Frank J.
Published: July 2002

The development of CVD techniques for fabricating free-standing tungsten and tungsten–rhenium alloy structures is reviewed. Relationships between plating parameters, kinetics, morphology, microstructure, and properties of thick polycrystalline deposits are discussed. It is emphasized that porosity may be grown into the grain boundaries when the depostition rate is controlled by gas phase diffusion, and that fully dense deposits are generally obtained when the rate is limited by a surface process. The origin and control of many of the microstructural features peculiar to CVD are also discussed.