bluuebunny/crossref_metadata_2025 huggingface dataset:
Smart sensor networks for robotic sensor skins
Authors: Tamasy Gabor J.
Published: July 2002

Data acquisition and data fusion of large numbers of sensors present unique challenges for control systems designers and applications engineers alike. In recent years the sensors industry has been moving towards the use of smart sensors, fieldbus networks, and localized smart processes. Merritt Systems Inc. of Rockledge, Florida, has been in the forefront of these developments since 1987 when it started pursuing the development of large sensor networks for robotic obstacle avoidance. As a result of this work a number of unique smart sensors and network technologies have been developed which have a wide range of applications beyond robotics. These include: one of industry’s first smart sensors, smart sensor networks, PC‐based data acquisition and control systems, and novel robotic modelling and motion planning algorithms. Whenever large networks of sensors with mixed sensing media are used, this technology has far‐reaching applications to industry and the research community.
Micromachined gyroscopic sensors
Authors: Yates Rob
Published: July 2002

Many new micromachined angular rate sensors (gyroscopes) are now commercially available. Their rapid development has been mainly due to the automotive industry. A wide range of different devices exists and their performance is significantly improving every year while costs are falling. Much effort is now under way for large volume production. This article provides a general overview of gyroscopic sensors and also describes a novel micromachined rotating device.
Valuation of real estate in global markets
Authors: Mackmin David
Published: July 2002

This paper considers the development of national and international standards for valuers. Examines in outline the variations in market practice arising from variations in law, culture and custom while noting the general acceptance internationally of the underlying meaning of “market value”.
Monte Carlo evaluation of the transport coefficients in a n+ – n – n+ silicon diode
Authors: Muscato Orazio
Published: July 2002

Hydrodynamic‐like models are commonly used for describing carrier transport in semiconductor devices. One major problem of this formulation is how to model the production terms. In this paper the relaxation‐time approximation and the moments expansion of the production terms are checked with Monte Carlo simulations for a one dimensional n+ – n – n+ silicon diode in the spherical parabolic band approximation.
Correlates of pay satisfaction in higher education
Authors: Oshagbemi Titus
Published: July 2002

Despite numerous studies of pay comparisons and pay satisfaction among public and private sector workers, little is known about correlates of employee satisfaction with pay. Investigates the correlates of pay satisfaction among UK academics. Using a questionnaire methodology, the study found that over 50 per cent of the respondents expressly stated that they were dissatisfied with their pay. The results of a three‐way analysis of variance (ANOVA) showed that female academics are more satisfied with their pay when compared with their male colleagues. When rank was examined in relation to pay, senior lecturers were most satisfied, followed by professors, lecturers and readers in that order. The differences in satisfaction levels with rank and gender are statistically significant. However, there are no statistical differences with respect to age variations relating to satisfaction with pay. Explores the implications of these results.
Format for human body modelling from 3‐D body scanning
Authors: Jones Peter R.M. , Li Peng , Brooke‐Wavell Katherine , West Gordon M.
Published: July 2002

Presents a standard data format for describing and interpolating 3‐D human body shapes from data collected by a 3‐D body scanner. The body data were treated as a series of horizontal cross‐sections. Each cross‐section was described by 16 data points. The 3‐D surface can be calculated by interpolating between these sections. This procedure allowed editing and manipulation of raw scanned data, as well as substantial data reduction. Horizontal cross‐sections of the body were chosen to correspond to particular anatomical surface landmarks, rather than distances from a reference point. Hence, each data element described a particular anatomical location, irrespective of body shape and size. This feature allowed comparison and averaging of 3‐D shapes, greatly enhancing the application of 3‐D scanned data. The standard data format allows 3‐D scanned data to be transferred into CAD/CAM systems for automated garment design and manikin manufacture.
Relating school policies and staff attitudes to the homework behaviours of teachers
Authors: Wiesenthal Richard , Cooper Bruce S. , Greenblatt Ruth , Marcus Sheldon
Published: July 2002

Research on homework has typically focused on students’ beliefs, commitment to, and benefits of doing homework, but what about the influence of school policies and teachers’ beliefs and attitudes on the topic? Do schools with stricter rules and a clearer focus have teachers giving more homework? Are teachers who believe in the virtues of homework as a learning device and a convenient means for communicating with the home more likely to give, collect, mark, and return homework to students than teachers who see no benefits? This study developed a valid, reliable instrument, the homework attitude and behaviour inventory for teachers (HABIT), and administered it to 120 teachers in two schools with a clear, focused homework policy, and two without. Findings were that schools with a well‐defined homework policy had teachers who: gave, collected, marked, and returned homework significantly more often; and believed in the usefulness of these assignments. Multiple regressions showed a significant relationship between beliefs about homework, the homework behaviours, and the types of assignments made (repeat classwork, introduce new materials, explore new ideas, pursue imaginative topics at home). Regressing homework attitudes and school policies against teacher homework behaviours produced an adjusted R‐square of 49.5 (p < 0.001).
What is higher education for? Strategic dilemmas for the
twenty‐first century university
Authors: King Roger
Published: July 2002

Higher education is still very much is demand throughout the world,
but is increasingly financially squeezed because of budget constraints.
The UK has responded by encouraging “diversity of mission”
and setting performance targets. In practice, however, this has often
resulted in sameness rather than diversity. This also raises the
question of quality and standards. As a result of these developments the
traditional idea of a “university” in the UK is itself being
challenged. Discusses the major elements of change in higher education.
Concludes that the twenty‐first century university will be unlikely to
succeed unless it can manage change effectively.
Mechanosensitive cation channels in human leukaemia cells: calcium permeation and blocking effect
Authors: Staruschenko Alexandr V. , Vedernikova Elena A.
Published: July 2002

Cell‐attached and inside‐out patch‐clamp methods were employed to identify and characterize mechanosensitive (MS) ionic channels in the plasma membrane of human myeloid leukaemia K562 cells. A reversible activation of gadolinium‐blockable mechanogated currents in response to negative pressure application was found in 58 % of stable patches (n= 317). I‐V relationships measured with a sodium‐containing pipette solution showed slight inward rectification. Data analysis revealed the presence of two different populations of channels that were distinguishable by their conductance properties (17.2 ± 0.3 pS and 24.5 ± 0.5 pS), but were indistinguishable with regard to their selective and pharmacological properties. Ion‐substitution experiments indicated that MS channels in leukaemia cells were permeable to cations but not to anions and do not discriminate between Na+ and K+. The channels were fully impermeable to large organic cations such as Tris+ and N‐methyl‐d‐glucamine ions (NMDG+). Ca2+ permeation and blockade of MS channels were examined using pipettes containing different concentrations of Ca2+. In the presence of 2 mm CaCl2, when other cations were impermeant, both outward and inward single‐channel currents were observed; the I‐V relationship showed a unitary conductance of 7.7 ± 1.0 pS. The relative permeability value, PCa/PK, was equal to 0.75, as estimated at physiological Ca2+ concentrations. Partial or full inhibition of inward Ca2+ currents through MS channels was observed at higher concentrations of external Ca2+ (10 or 20 mm). No MS channels were activated when using a pipette containing 90 mm CaCl2. Monovalent mechanogated currents were not significantly affected by extracellular Ca2+ at concentrations within the physiological range (0‐2 mm), and at some higher Ca2+ concentrations.
Bile acids induce calcium signals in mouse pancreatic acinar cells: implications for bile‐induced pancreatic pathology
Authors: Voronina Svetlana , Longbottom Rebecca , Sutton Robert , Petersen Ole H. , Tepikin Alexei
Published: July 2002

The effect of the natural bile acid, taurolithocholic acid 3‐sulfate (TLC‐S), on calcium signalling in pancreatic acinar cells has been investigated. TLC‐S induced global calcium oscillations and extended calcium transients as well as calcium signals localised to the secretory granule (apical) region of acinar cells. These calcium signals could still be triggered by TLC‐S in a calcium‐free external solution. TLC‐S‐induced calcium signals were not inhibited by atropine, but were abolished by caffeine or by depletion of calcium stores, due to prolonged application of ACh. Global calcium signals, produced by TLC‐S application, displayed vectorial apical‐to‐basal polarity. The signals originated in the apical part and were then propagated to the basal region. Other natural bile acids, taurocholate (TC) and taurodeoxycholate (TDC), were also able to produce local and global calcium oscillations (but at higher concentrations than TLC‐S). Bile, which can enter pancreas by reflux, has been implicated in the pathology of acute pancreatitis. The calcium releasing properties of bile acids suggest that calcium toxicity could be an important contributing factor in the bile acid‐induced cellular damage.
Analysis of a Tubesheet Undergoing Rapid Transient Thermal Loading
Authors: Reinhardt W. , Kizhatil R. , McClellan G. H.
Published: July 2002

Some Class I CANDU heat exchanger tubesheets experience very high in-plane thermal gradients under Level A/B transients. If the thermal stresses exceed the ratcheting limit of the ASME Boiler and Pressure Vessel Code, shakedown has to be demonstrated by an elastic-plastic analysis. The choice of the plasticity model and its parameters must ensure that shakedown is predicted only if it occurs in reality. Differences to uniaxial modeling are discussed, and a conservative way of predicting shakedown is presented. The perforated region of the tubesheet is replaced by an equivalent solid plate with anisotropic yield properties (Hill’s yield criterion). A lower-bound shakedown limit for this material is derived. An example analysis is presented that has been performed using a commercial finite element code. [S0094-9930(00)00303-6]
Discussion: “On the Development and Application of the Fast-Response Aerodynamic Probe System in Turbomachines–Part 3: Comparison of Averaging Methods Applied to Centrifugal Compressor Measurements” [ASME J. Turbomach., 122, No. 3, pp. 527–535 (2000)]1
Authors: Cumpsty N. A.
Published: July 2002

[S0889-504X(00)01303-9]
Steady-Periodic Three-Dimensional Foundation Heat Transfer From Refrigerated Structures
Authors: Chuangchid Pirawas , Krarti Moncef
Published: July 2002

Analytical solutions for steady-periodic ground-coupled heat conduction problems for cylindrical and three-dimensional rectangular slab-on-grade floors beneath refrigerated structures with uniform and partial insulation are presented in this paper. The solutions provide the soil temperature field, and the total slab heat gain. A parametric analysis is conducted to determine the effect of thermal insulation U-value and insulation width on the mean, amplitude, and phase lag of total slab heat gain. In particular, it was found that the mean and the amplitude of the total slab heat gain are effectively independent of its shape but are strongly affected by the slab size and thermal characteristics. [S0199-6231(00)00502-5]
Inability of Free-Interface Modes in Representing Stress Resultants Near the Free Interface
Authors: Kim Yoon Young , Kang Jeong Hoon
Published: July 2002

As the fundamental cause of the slow convergence of a direct free-interface component mode synthesis method, we point out the inability of free-interface normal modes in representing the stress resultants near the free interface of a substructure. Although the effects of the residual flexibility of a substructure on the solution convergence are well known, the present theoretical analysis would help understand more clearly the convergence problems of the direct free-interface substructure coupling method. [S0739-3717(00)01704-9]
Assessing Circularity in Three Dimensions1
Authors: Chou Shuo-Yan , Lin Shih-Wei , Chen Chien-Hong
Published: July 2002

This research resolves an inconsistency problem that arises from assessing circularity of workpiece measured by coordinate measuring machines (CMMs). Although the notion of circularity is employed to constrain two-dimensional circular features, in practice the measured points are obtained in a three-dimensional space and are in general not in the same plane, let alone being in a “perpendicular” cross-section. All of the algorithms currently used for assessing circularity deal with data in a single plane that is perpendicular to the axis of a cylindrical feature from which the circular feature is extracted. This discrepancy causes the assessed circularity significantly departing from the actual circularity and resulting in rejection of in-tolerance parts. This research designs a compensation procedure for deriving two-dimensional data from three-dimensional biased measured points. The circularity is assessed based on the compensated two-dimensional data points. The assessment results with the compensation are compared with those without compensation. A program containing a variety of implementations of form fitting algorithms is developed and used to illustrate the improvement on the accuracy of assessment.
Discussion: “An Energy Method for Analyzing Magnetoelastic Buckling and Bending of Ferromagnetic Plates in Static Magnetic Fields” (Yang, W., Pan, H., Zheng, D., and Cai, Z., 1999, ASME J. Appl. Mech., 66, pp. 913–917)
Authors: Zhou You-He
Published: July 2002

[S0021-8936(00)03903-9]
Thermally Induced Vibration of an Internally Heated Beam
Authors: Blandino Joseph R. , Thornton Earl A.
Published: July 2002

Virtually all previous research on thermally induced vibrations has investigated vibrations caused by surface heating. This paper describes the first detailed study of a thermally induced vibration caused by internal heating. A mathematical model was developed to predict the thermal-structural behavior of an internally heated beam. The results from the model were verified using experimental data for an internally heated beam undergoing thermally induced vibrations. The model was shown to predict the steady-state temperatures accurately. The model predicted the steady-state displacements adequately, although it predicted the displacement histories with some error. The analysis showed that the natural frequency of the beam was more important than the heating rate in determining if vibrations will occur. Once initiated, the amplitude of the vibration increased until the amplitude was such that the heat removed by convection balanced the internal heating. The steady-state amplitude was not affected by the initial displacement of the beam. The convection heat transfer caused the vibrations and controlled the steady-state amplitude. This study showed that thermally induced vibrations of internally heated beams belong to the class of vibrations called self-sustaining oscillations.
On the Unification of Yield Criteria
Authors: Fan S. C. , Yu M.-H. , Yang S.-Y.
Published: July 2002

A piecewise linear unified yield criterion called the twin-shear-unified was proposed. It is based on a kind of orthogonal dodecahedron stress element. The effects of intermediate principal stress are taken into account such that most available yield loci on the π-plane are embraced in a unified manner. Besides, it is capable to represent not only convex limit surfaces but also nonconvex limit surfaces.
On the General Solution for Piezothermoelasticity for Transverse Isotropy With Application
Authors: Chen W. Q.
Published: July 2002

This paper derives a general solution of the three-dimensional equations of transversely isotropic piezothermoelastic materials (crystal class, 6 mm). Two displacement functions are first introduced to simplify the basic equations and a general solution is then derived using the operator theory. For the static case, the proposed general solution is very simple in form and can be used easily in certain boundary value problems. An illustrative example is given in the paper by considering the symmetric crack problem of an arbitrary temperature applied over the faces of a flat crack in an infinite space. The governing integro-differential equations of the problem are derived. It is found that exact expressions for the piezothermoelastic field for a penny-shaped crack subject to a uniform temperature can be obtained in terms of elementary functions. [S0021-8936(00)01704-9]
Measurements of Air Entrainment by Bow Waves
Authors: Waniewski T. A. , Brennen C. E. , Raichlen F.
Published: July 2002

This paper describes measurements of the air entrained in experiments simulating the breaking bow wave of a ship for Froude numbers between two and three. The experiments and the characteristics of the wave itself are detailed in T. Waniewski, 1999, “Air Entrainment by Bow Waves; Ph.D. theses, Calif. Inst. of Tech.” The primary mechanism for air entrainment is the impact of the plunging wave jet, and it was observed that the air bubbles were entrained in spatially periodic bubble clouds. The void fraction and bubble size distributions were measured in the entrainment zone. There were indications that the surface disturbances described in Waniewski divide the plunging liquid jet sheet into a series of plunging jets, each of which produces a bubble cloud.
Shilnikov Chaos and Dynamics of a Self-Sustained Electromechanical Transducer
Authors: Chedjou J. C. , Woafo P. , Domngang S.
Published: July 2002

The dynamics of a self-sustained electromechanical transducer is studied. The stability of the critical points is analyzed using the analytic Routh-Hurwitz criterion. Analytic oscillatory solutions are obtained in both the resonant and non-resonant cases. Chaotic behavior is observed using the Shilnikov theorem and from a direct numerical simulation of the equations of motion.
Optimum Dimensional Analysis With Applications to Elastohydrodynamic Lubrication
Authors: Hsiao Hsing-Sen S.
Published: July 2002

A robust, straightforward technical procedure referred to as “optimum dimensional analysis” that is a hybrid of conventional dimensional analysis and optimum similarity analysis is proposed here to find a smallest set of system dimensionless power products of dimensions for nondimensionalizing a set of system equations. With these dimensionless parameters, the system behavior can be fully described by a most concise set of dimensionless governing equations and boundary/initial conditions. Functional relationships between the system dependent dimensionless parameters and a smallest set of system independent dimensionless parameters are thereby established. All alternative sets of optimum dimensionless parameters can be identified without any computational complications. A simple illustration is given first to analyze a time-dependent initial value problem. Applications to EHL of rectangular and elliptical contacts then follow. Because the inference process of the optimum dimensional analysis always arrives at clearest and simplest formulas for system dependency equations, especially for initial value problems, this process may be simply referred to as “optimum analysis.”
Effect of Size and Position of Supporting Buoys on the Dynamics of Spread Mooring Systems
Authors: Garza-Rios Luis O. , Bernitsas Michael M.
Published: July 2002

Vessels moored in deep water may require buoys to support part of the weight of the mooring lines. The effects that size and location of supporting buoys have on the dynamics of spread mooring systems (SMS) at different water depths are assessed by studying the slow motion nonlinear dynamics of the system. Stability analysis and bifurcation theory are used to determine the changes in SMS dynamics in deep water based as functions of buoy parameters. Catastrophe sets in a two-dimensional parametric design space are developed from bifurcation boundaries, which separate regions of qualitatively different dynamics. Stability analysis defines the morphogeneses occurring as bifurcation boundaries are crossed. The mathematical model of the moored vessel consists of the horizontal plane—surge, sway, and yaw—fifth-order, large-drift, low-speed maneuvering equations. Mooring lines made of chains are modeled quasi-statically as catenaries supported by buoys including nonlinear drag and touchdown. Steady excitation from current, wind, and mean wave drift are modeled. Numerical applications are limited to steady current and show that buoys affect both the static and dynamic loss of stability of the system, and may even cause chaotic response.
A New Cepstral Analysis Procedure of Recovering Excitations for Transient Components of Vibration Signals and Applications to Rotating Machinery Condition Monitoring
Authors: Zheng G. T. , Wang W. J.
Published: July 2002

A new cepstral analysis procedure with the complex cepstrum for recovering excitations causing multiple transient signal components from vibration signals, especially from rotor vibration signals, has been developed. Along with the problem of singularity, a major problem of the cepstrum is that it cannot provide a correct distribution of the excitations. To solve these problems, a signal preprocessing method, whose function is to provide a definition for the distribution of the excitations along the quefrency axis and remove singular points from the transform, has been added to the cepstrum analysis. With this procedure, a correct distribution of the excitations can be obtained. An example of application to the condition monitoring of rotor machinery is also presented.
Buckling of Free Infinite Strips Under Residual Stresses and Global Tension
Authors: Rammerstorfer F. G. , Fischer F. D. , Friedl N.
Published: July 2002

Long free strips of small thickness frequently show a wavy surface being the consequence of buckling due to residual stresses. The paper deals with the derivation of the corresponding relations under conditions which are frequently met in the case of edge wave buckling of rolled strips or in deployable structures. It is shown that an increasing global tension force does not only lead to increased critical residual stress intensity but also produces shorter buckling waves concentrated towards the edges of the strip. By introducing dimensionless quantities, diagrams and formulas are provided which allow the determination of critical loading combinations. Asymptotic considerations are also presented.
A Study of Integrally Augmented State Feedback Control for an Active Magnetic Bearing Supported Rotor System
Authors: Flowers G. T. , Sza´sz G. , Trent V. S. , Greene M. E.
Published: July 2002

State feedback controller designs allow for pole placement in an effective manner, but reduction of static offset is difficult. On the other hand, classical control methodology allows for the increase of system type and the elimination of static offset. An integrally augmented state feedback controller provides the benefits of standard feedback designs while allowing for the elimination of static offsets (through the increase of system type). Static offset is a particular problem with magnetic bearing supported rotor systems, in that gravitational effects, current biasing, and operational loading tend to exacerbate this problem. In order to assess the effectiveness of this technique, an integrally augmented state feedback controller is developed, implemented, and tested for a magnetic bearing supported rotor system. Results for several selected configurations are presented and compared. Some conclusions and recommendations concerning the effectiveness of integrally augmented state feedback controller designs are presented.
Computation of Particle and Scalar Transport for Complex Geometry Turbulent Flows
Authors: Tucker P. G.
Published: July 2002

The prediction of particle and scalar transport in a complex geometry with turbulent flow driven by fans is considered. The effects of using different turbulence models, anisotropy, flow unsteadiness, fan swirl, and electrostatic forces on particle trajectories are shown. The turbulence models explored include k−l, zonal k−ε/k−l, and nonlinear eddy viscosity models. Particle transport is predicted using a stochastic technique. A simple algorithm to compute electrostatic image forces acting on particles, in complex geometries, is presented. Validation cases for the particle transport and fluid flow model are shown. Comparison is made with new smoke flow visualization data and particle deposition data. Turbulence anisotropy, fan swirl, and flow unsteadiness are shown to significantly affect particle paths as does the choice of isotropic turbulence model. For lighter particles, electrostatic forces are found to have less effect. Results suggest, centrifugal forces, arising from regions of strong streamline curvature, play a key particle deposition role. They also indicate that weaknesses in conventional eddy viscosity based turbulence models make the accurate prediction of complex geometry particle deposition a difficult task. Axial fans are found in many fluid systems. The sensitivity of results to their modeling suggests caution should be used when making predictions involving fans and that more numerical characterization studies for them could be carried out (especially when considering particle deposition). Overall, the work suggests that, for many complex-engineering systems, at best (without excessive model calibration time), only qualitative particle deposition information can be gained from numerical predictions.
Stability of Reconstructed Paralyzed Shoulders Using a Reflected Long Head Biceps Technique
Authors: Tang C. Y. , Mak A. F. T. , Hung L. K. , Wong H. S. , Pacaldo T.
Published: July 2002

A new tendon transfer technique is proposed for the reconstruction of the paralyzed shoulders secondary to Brachial Plexus Injury (BPI). In this tendon transfer, the long head of the biceps tendons is utilized as a bridging tendon graft. It is reflected at the exit of the bicipital groove, passed through the deltoid and directed to the trapezius. The technique is referred to here as the Reflected Long Head Bicepts (RLHB) technique. This study evaluated the effect of this tendon transfer on the anterior, posterior, and inferior stability of the reconstructed should using cadaveric specimens. It was shown that loading of the RLHB contributed significantly to anterior stability of the reconstructed shoulder for 90 deg elevation in the scapula plane. The mean displacement was reduced by 56 percent with RLHB loaded (p<0.01), by 56 percent with the rotator cuff loaded (p<0.005), and by 67 percent with both the RLHB and the rotator cuff loaded (p<0.004). For the post-operation conditions, variation of the directions of RLHB had no significant effect on joint displacement in response to anterior loading. The RLHB tendon also contributed to the posterior and inferior stability for the low and middle elevations in the plane of scapula. Two variations of the RLHB tendon transfer procedures, namely the “Sub-Deltoid” and the “Through-Deltoid” techniques, were introduced and studied. These two techniques did not seem to have significantly different effects on the displacement of the humeral head in response to both posterior and inferior loading. The results of this study seemed to support the clinical feasibility of this tendon transfer approach as far as the biomedical stability of the reconstruction is concerned.
Wave Oscillation in a Circular Harbor With Porous Wall
Authors: Yip T. L. , Sahoo T. , Chwang A. T.
Published: July 2002

The wave resonance in a circular harbor surrounded by a porous seawall is analyzed. Matching the velocity and pressure along the porous seawall and the harbor entrance, the full solution is obtained. The resonance condition is found to depend on the wave frequency, the complex porous-effect parameter and the internal dimension of the porous seawall. The oscillation characteristics are analyzed in different cases. The condition for natural oscillation is derived by studying the wave resonance in a closed circular harbor surrounded by a porous seawall.
Influence of Cutting Parameters on Residual Stresses Induced by Milling in Pressure Die-Cast Aluminum Alloy Components
Authors: Berruti T. , Ubertalli G.
Published: July 2002

Residual stress states, induced by milling in a die cast aluminum alloy component, have been determined by means of X-ray diffraction. Samples have been cut from an automotive engine sump, fabricated by pressure die-casting. The X-ray experimental apparatus has been calibrated by detecting stresses on a sample bent under imposed external deformations. Different samples (cut from the sump) have been tested after milling operations with each one characterized by different cutting speed, feed speed and depth of cut in order to evaluate their influence on the final residual stress state. Results have been analyzed taking into account surface morphologies after milling, as revealed by scanning electron microscopy.
Global Surface Solar Energy Anomalies Including El Nin˜o and La Nin˜a Years*
Authors: Whitlock C. H. , Brown D. E. , Chandler W. S. , DiPasquale R. C. , Ritchey Nancy A. , Gupta Shashi K. , Wilber Anne C. , Kratz David P. , Stackhouse Paul W.
Published: July 2002

Weather anomalies that increase clouds influence the reliability of both renewable energy and building environmental-control systems. Non-grid solar power systems may run out of capacity for such items as communications electronics, flood-warning stream gages, refrigerators, and small village power systems. This paper provides 1×1-degree resolution global maps that identify those regions which experienced large abnormal solar energy during a 10-year period. A source is identified where specific values for maximum year-to-year variability can be obtained in regions where ground-site measurements do not exist. The information may aid in the selection of safety factors for solar power systems.
Experimental Evaluation of the Dynamic Behavior of an Air-Breathing Fuel Cell Stack
Authors: Morner Svein O. , Klein Sanford A.
Published: July 2002

The performance of an air breathing proton exchange membrane (PEM) fuel cell stack has been experimentally measured to investigate the steady-state and transient effects of temperature, humidity and air flowrate. The results show that hydrogen leaks to the cathode through the membrane causing internal heating of the fuel cell. The leakage rate is found to be linearly dependent on the pressure difference between the hydrogen side and air side which is at atmospheric pressure. Temperature was found to not have a significant effect on the PEM performance, except through its indirect effect on humidity. The humidity of the membrane is found to be the most significant variable in determining the fuel cell performance. The airflow also influences the performance of the fuel cell directly by supplying oxygen and indirectly by influencing the humidity of the membrane. Experiments show that an optimum air flowrate exists that is much larger than required for stoichiometric oxidation of the fuel.
A New Approach of Coordinated Motion Control Subjected to Actuator Saturation
Authors: Niu Weiguang , Tomizuka Masayoshi
Published: July 2002

In this paper, a new approach of motion coordination of two axes systems in the presence of actuator saturation is proposed. The proposed approach includes two parts: feedback controller and on-line trajectory planning. The feedback controller is designed using an anti-windup design to reduce the degradation in performance of each axis when saturation occurs. An on-line trajectory planning algorithm is also proposed to maintain the contouring accuracy during saturation periods. The desired outputs for X- and Y-axis are given as sequences of points. When the actuator of any axis is predicted to saturate, an appropriate number of points are inserted in the original sequence to slow down the motion. The effectiveness of the proposed approach is studied by simulation of a two-axis Cartesian positioning system.
Traction Behavior of Some Lubricants Used for Rolling Bearings in Spacecraft Applications: Experiments and Thermal Model Based on Primary Laboratory Data
Authors: Ne´lias Daniel , Legrand Eric , Vergne Philippe , Mondier Jean-Bernard
Published: July 2002

Three synthetic oils used in spacecraft mechanisms (Pennzane SHF X2000, Nye 186 A, and Fomblin Z25) have been studied. Rheological tests were performed in order to characterize the behavior of each fluid versus pressure, temperature and shear rate. That includes the determination of the WLF viscosity model parameters. Tribological tests were carried out to measure the traction coefficient for operating conditions representative of spacecraft applications. Experimental results were compared with theoretical ones obtained using a non-newtonian thermal model. The modeling of traction in EHL contact is based on the Johnson and Tevaarwerk’s model modified to account for the shear heating of the fluid. The variations of the lubricant thermal conductivity with respect to temperature and pressure are also considered. In this model, input data comes directly from rheological experiments or are derived from other measurements through physical relationships. These rheological and tribological characterizations are essential to better describe the behavior of a lubricated rolling bearing.
New Frontiers in the Design of Steel Catenary Risers for Floating Production Systems
Authors: Mekha Basim B.
Published: July 2002

The steel catenary riser (SCR) concept has recently been used in almost every new deepwater field development around the world. Shell pioneered the implementation of the SCR concept in 1994 on its Auger tension leg platform (TLP) in 872 m (2860 ft) water depth. Since then, SCRs have been vital to deepwater field developments. Their use has given a new dimension to oil exploration and transportation in water depths where other riser concepts could not tolerate the environmental loads or would have become very costly. SCR designs are very sensitive to floating support platform or vessel motion characteristics to which they are typically attached. In addition to pipe stresses, the main design issue for the SCR concept is fatigue related. There are two main sources for fatigue: random wave fatigue and vortex-induced vibration (VIV) fatigue. The former is due to wave action and the associated platform motion characteristics. The VIV fatigue is mainly due to current conditions. Fracture mechanics assessment is also an essential issue that must be addressed in the design of SCRs. This paper presents a brief history in the use and development of SCRs since the first project implementation on Auger TLP in 1994. The paper also summarizes major steps that must be considered in the design of SCRs and how to explain their behavior in different water depths and environmental conditions. Existing design boundaries for SCRs are discussed with emphasis on the capabilities of new technologies that enable engineers to go beyond these boundaries. Projects with unique SCR features and their implementation are compiled and presented.
An Exact Approach For Free Vibration Analysis of Multi-Step Nonuniform Shear Plates
Authors: Li Q. S.
Published: July 2002

In this paper multi-story frame buildings are treated as shear plates with variably distributed mass and stiffness for free vibration analysis. An analytical model of a shear plate is proposed and an exact approach for determining natural frequencies and mode shapes of such shear plates is presented. The function for describing the distribution of mass of a shear plate along the plate height is an arbitrary one and the distribution of shear stiffness is expressed as a functional relation with the distribution of mass and vice versa. The exact solutions of one-step shear plates are obtained first for seven cases. Then the derived exact solutions of one-step shear plates are used to establish the frequency equations of multi-step shear plates by using the transfer matrix method. The numerical example shows that the natural frequencies and mode shapes of a shear plate calculated by the proposed methods are in good agreement with the measured data and those determined by the Ritz method and the finite element method, verifying the accuracy and applicability of the proposed methods.
Dynamics of a Flexible Beam Contacting a Linear Spring at Low Frequency Excitation: Experiment and Analysis
Authors: Fegelman Karen J. L. , Grosh Karl
Published: July 2002

A detailed study of one-, two-, and three-impact per period motion of a vibro-impacting, pinned beam is presented involving experimental results, as well as one- and multi-degree-of-freedom theoretical models. The details of the impact event are examined and correlated to the qualitative appearance of the frequency response. In addition, it is noted that the multi-degree-of-freedom model is necessary in order to predict response at high frequencies. This study is unique in that the model system includes a pinned boundary condition, the forcing frequency is considerably lower than the fundamental in-contact natural frequency, and the frequency analysis extends into a range important for acoustic predictions.
Reduction of Vibration Caused by Magnetic Force in a Switched Reluctance Motor by Topology Optimization
Authors: Yoo J.
Published: July 2002

The topology optimization of a switched reluctance motor (SRM) excited by magnetic forces is an important issue to minimize the noise and vibration level. In this paper, the magnetic force is computed using the Maxwell stress method and the optimization problem is formulated to minimize the frequency response based on the homogenization design method (HDM). The developed method is applied to the stator of an SRM to minimize the deformation caused by the magnetic harmonic excitation. Numerical simulation shows that this method successfully decreases the vibration level of an SRM.
3D Mesh Generation for Static Stress Determination in Spiral Noncircular Gears Used for Torque Balancing
Authors: Barkah D. , Shafiq B. , Dooner D.
Published: July 2002

Standard procedures available for evaluating gear fillet stresses are targeted to circular gears where little information is available about noncircular gears. In this paper, a mesh generation algorithm is presented for the discretization of gear tooth profiles of noncircular gear elements for static stress evaluation using FEM (Finite Element Method). The procedure assumes that the noncircular gear tooth profile is known. Delimiting a tooth domain from the gear structure and subdividing it into sectors, the gear tooth mesh is generated by mapping pregenerated patterns into the sectors. The discretized tooth domain is used in conjunction with the FEM to obtain stresses within the tooth fillet region. For comparison, this procedure was applied to determine the stress distribution in circular gears and rectangular beams. The results were in complete agreement with existing analytical solutions. An illustrating example is presented where a noncircular gear pair is introduced to eliminate the speed and torque fluctuation that exists in an electrical generator when an I.C. engine is used as the power source for the generator. The maximum fillet Von Mises stress is calculated for each angular position of the noncircular gear pair.
A Nonlocal Phenomenological Anisotropic Finite Deformation Plasticity Model Accounting for Dislocation Defects
Authors: Regueiro Richard A. , Bammann Douglas J. , Marin Esteban B. , Garikipati Krishna
Published: July 2002

A phenomenological, polycrystalline version of a nonlocal crystal plasticity model is formulated. The presence of geometrically necessary dislocations (GNDs) at, or near, grain boundaries is modeled as elastic lattice curvature through a curl of the elastic part of the deformation gradient. This spatial gradient of an internal state variable introduces a length scale, turning the local form of the model, an ordinary differential equation (ODE), into a nonlocal form, a partial differential equation (PDE) requiring boundary conditions. Small lattice elastic stretching results from the presence of dislocations and from macroscopic external loading. Finite deformation results from large plastic slip and large rotations. The thermodynamics and constitutive assumptions are written in the intermediate configuration in order to place the plasticity equations in the proper configuration for finite deformation analysis.
Vaporization Cooling for Gas Turbines, the Return-Flow Cascade
Authors: Kerrebrock J. L. , Stickler D. B.
Published: July 2002

A new paradigm for gas turbine design is treated, in which major elements of the hot section flow path are cooled by vaporization of a suitable two-phase coolant. This enables the blades to be maintained at nearly uniform temperature without detailed knowledge of the heat flux to the blades, and makes operation feasible at higher combustion temperatures using a wider range of materials than is possible in conventional gas turbines with air cooling. The new enabling technology for such cooling is the return-flow cascade, which extends to the rotating blades the heat flux capability and self-regulation usually associated with heat-pipe technology. In this paper the potential characteristics of gas turbines that use vaporization cooling are outlined briefly, but the principal emphasis is on the concept of the return-flow cascade. The concept is described and its characteristics are outlined. Experimental results are presented that confirm its conceptual validity and demonstrate its capability for blade cooling at heat fluxes representative of those required for high pressure ratio high temperature gas turbines. [S0742-4795(00)00601-3]
Surface Tension Effects on Post-Nucleation Growth of Water Microdroplets in Supersaturated Gas Mixtures
Authors: Carey V. P.
Published: July 2002

Immediately after nucleation in a superheated gas mixture, the very small size of liquid droplets affects the condensation growth of the droplets in two ways: (1) The droplet size may be comparable to the mean free path of the gas molecules, resulting in noncontinuum transport effects, and (2) surface tension effects may strongly alter the conditions at the interface of the droplet. In the study reported here, a direct simulation Monte Carlo scheme was used to model the molecular transport during quasi-equilibrium condensation growth of water microdroplets in a supersaturated mixture of water vapor and a noncondensable gas. In the simulation, the boundary condition at the droplet surface is treated in a manner that allows us to model surface tension effects on transport. Results of calculations are presented for water vapor and argon mixtures for which some experimental data on droplet growth rates exists. The simulation results indicate that surface tension effects play a significant role in the determination of droplet growth rates during early stages of droplet growth. In particular, the results indicate that the droplet growth rate, droplet temperature, and the temperature slip at the interface pass through maxima as the droplet grows. These trends are a consequence of the shift in equilibrium vapor pressure due to surface tension effects at small droplet radii. [S0022-1481(00)02702-X]
Standard Nomenclature List
Authors: Hewitt G. F.
Published: July 2002

[S0022-1481(00)03002-4]
Sheet Thickness Optimization for Superplastic Forming of Engineering Structures
Authors: Huang A. , Cardew-Hall M. J. , Lowe A.
Published: July 2002

This paper explores two optimization strategies; the gradient search and proportional control methods, for determining the initial sheet thickness of superplastic forming to ensure final desired part thickness. A hemispherical dome model was involved in the testing of both optimization methods. Also, a three-dimensional rectangular box model was optimized by the proportional control method. The gradient search technique is shown to be acceptable in terms of the optimized thickness obtained, but displays poor convergence rates. The proportional control approach presented is easy to be implemented, and yields not only more accurate sheet thickness, but much higher convergence speeds that makes such optimization possible on complex geometric models. [S1087-1357(00)01001-7]
High Speed Grinding of Silicon Nitride With Electroplated Diamond Wheels, Part 2: Wheel Topography and Grinding Mechanisms
Authors: Hwang T. W. , Evans C. J. , Malkin S.
Published: July 2002

This is the second in a series of two papers concerned with high speed grinding of silicon nitride with electroplated diamond wheels. In the first article (ASME J. Manuf. Sci. Eng., 122, pp. 32–41), it was shown that grinding of silicon nitride is accompanied by dulling of the abrasive grains and a significant increase in the grinding forces and power. High wheel speed caused more wheel wear, which was attributed to a longer accumulated sliding length between the abrasive grains and the workpiece. This second paper is concerned with the progressive change in wheel topography during grinding and how it affects the grinding process. A statistical model is developed to characterize the wheel topography during grinding in terms of active cutting grains and wear flat area. According to this model, continued grinding is accompanied by an increase in both the number of active grains and the wear flat area on the wheel surface as the wheel wears down. The measured increase in grinding forces and power was found to be proportional to the wear flat area, which implies a constant average contact pressure and friction coefficient between the wear flats and the workpiece. Increasing the wheel speed from 85 to 149 m/s significantly reduced the contact pressure, which may be attributed to a reduction of the interference angle, but had almost no effect on the attritious wear rate of the diamond abrasive. Therefore, more rapid wear of the diamond wheel at higher wheel speeds due to a longer sliding length may be offset by reduced contact pressures and lower grinding forces. [S1087-1357(00)00401-9]