bluuebunny/crossref_metadata_2025 huggingface dataset:
Barriers to women managers’ advancement in education in Uganda
Authors: Brown Marie
Published: July 2002

Attempts to explain women’s lack of achievement in educational management, both in countries in the developed world and in Africa, particularly Uganda. Suggests that women are hindered by both internal and external barriers which keep them from advancing; internally in the main owing to the effects of socialization and sex stereotyping, and externally because organizations so structure the behaviour of their workforce that women limit their performance because they are locked into low‐power, low‐visibility, dead‐end jobs. Points out that these barriers are particularly applicable to women educational managers in Uganda, whose advancement is further impeded by the cultural imperatives of male dominance and suppression. Highlights a number of strategies which can help Ugandan women to overcome these barriers, such as a sensitization programme to alert women to the opportunities available, and affirmative action by the government to put equality of opportunity as a high priority on the Ugandan national agenda.
Franchising in Austria
Authors: Glatz Erika , Chan Peng
Published: July 2002

This paper describes the status quo of the Austrian franchise situation. Judging from current trends, the future of franchising seems to have a bright outlook in Austria. The growth in franchising is a result not only of the increasing number of homegrown systems, but also of the influx of foreign franchise systems. Recently, there has been an increase in information and consulting activities as a result of the growing demand. Owing to the fact that little research on franchising in Austria has been done so far, there is a wide area for further investigation on this subject.
Simulation modeling of a garment production system using a spreadsheet to minimize production cost
Authors: Rotab Khan M.R.
Published: July 2002

A methodology of structuring a garment production simulation model using a spreadsheet is described to minimize the average daily production cost through the investigation of various man‐machine combinations. The capability and usability of an easily available modern spreadsheet Excel 7.0 to simulate a simple garment production system is accessed with an attempt to demonstrate the simulation model building in a user friendly environment rather than learning and using costly simulation programming languages or simulation software packages. Simulation has evaluated the resource utilization and measured the system performance and developed strategies for taking operational decisions in a logical and better way to minimize the garment production cost. It may also assist and benefit the garment production managers to plan, design and operate their systems in an efficient manner in a competitive environment.
Translating institutional objectives into action
Authors: Gordon George
Published: July 2002

In higher education, translating institutional objectives into meaningful action is a challenging task, particularly given the currency attached to analogies such as the view that managing academics is akin to herding cats, or that teaching in HE is one of the last cottage industries. Yet alignment is becoming increasingly important, as the reports of national inquiries and commissions (e.g. Dearing, West, Boyer) and the pronouncements and plans of governments indicate. The paper examines one illustration of steps that an institution has taken to translate objectives into action.
A user‐based design process for Web sites
Authors: Abelse Eileen G. , Domas White Marilyn , Hahn Karla
Published: July 2002

This paper reports on Phase II of a two‐part project to identify and implement user‐based design criteria in World Wide Web sites. The test site is a Web page for the academic business community. As an alternative to existing, largely ad hoc design processes, the authors developed a user‐based design process, gathering user input at three different times in the process. Delineating this four‐stage process (information‐gathering; development; test and evaluation; and implementation) is a major focus of the paper. In addition to explaining the process in detail, the paper reports on the second stage of this process, which involves operationalizing definitions of the criteria and translating the criteria into Web page features and, to some extent, on the evaluation activities undertaken during Stage 3. Already reported are the results of Stage 1, which gathered user criteria for evaluating Web sites through a focus group session.
Drucker on effective public management
Authors: Gazell James A.
Published: July 2002

Management historians have devoted attention to writer Peter F. Drucker’s thoughts about directing businesses successfully but may have overlooked (or been unaware of) his appreciation of the inherent difficulties in managing public sector organizations effectively. He nevertheless wrote extensively about two highly important components of this sector: nonprofit organizations and the federal government. He was among the earliest observers to recognize the growing significance of nonprofits and the variety of obstacles to their more effective management. He also perceived categories of management problems unique to the ability of the federal government to be run well ‐ a set of external and internal limits. His observations reveal an underlying respect for the role of government and his desire to strengthen it by focussing its missions and priorities on what it must do and what it does best and identifying what it does poorly and should thus delegate to nonprofits and business.
Mechanistic aspects of cyanogenesis from active‐site mutant Ser80Ala of hydroxynitrile lyase from Manihot esculenta in complex with acetone cyanohydrin
Authors: Lauble Hanspeter , Miehlich Burkhard , Förster Siegfried , Wajant Harald , Effenberger Franz
Published: July 2002

The structure and function of hydroxynitrile lyase from Manihot esculenta (MeHNL) have been analyzed by X‐ray crystallography and site‐directed mutagenesis. The crystal structure of the MeHNL–S80A mutant enzyme has been refined to an R‐factor of 18.0% against diffraction data to 2.1‐Å resolution. The three‐dimensional structure of the MeHNL–S80A–acetone cyanohydrin complex was determined at 2.2‐Å resolution and refined to an R‐factor of 18.7%. Thr11 and Cys81 involved in substrate binding have been substituted by Ala in site‐directed mutagenesis. The kinetic measurements of these mutant enzymes are presented. Combined with structural data, the results support a mechanism for cyanogenesis in which His236 as a general base abstracts a proton from Ser80, thereby allowing proton transfer from the hydroxyl group of acetone cyanohydrin to Ser80. The His236 imidazolium cation then facilitates the leaving of the nitrile group by proton donating.
The effect of substrate binding on the conformation and structural stability of Herpes simplex virus type 1 thymidine kinase
Authors: Wurth Christine , Kessler Ulrich , Vogt Joachim , Schulz Georg E. , Folkers Gerd , Scapozza Leonardo
Published: July 2002

The structure of Herpes simplex virus type 1 thymidine kinase (TKHSV1) is known at high resolution in complex with a series of ligands and exhibits important structural similarities to the nucleoside monophosphate (NMP) kinase family, which are known to show large conformational changes upon binding of substrates. The effect of substrate binding on the conformation and structural stability of TKHSV1, measured by thermal denaturation experiments, far‐UV circular dichroism (CD) and fluorescence is described, and the results indicate that the conformation of the ligand‐free TKHSV1 is less ordered and less stable compared to the ligated enzyme. Furthermore, two crystal structures of TKHSV1 in complex with two new ligands, HPT and HMTT, refined to 2.2 Å are presented. Although TKHSV1:HPT does not exhibit any significant deviations from the model of TKHSV1:dT, the TKHSV1:HMTT complex displays a unique conformationally altered active site resulting in a lowered thermal stability of this complex. Moreover, we show that binding affinity and binding mode of the ligand correlate with thermal stability of the complex. We use this correlation to propose a method to estimate binding constants for new TKHSV1substrates using thermal denaturation measurements monitored by CD spectroscopy. The kinetic and structural results of both test substrates HPT and HMTT show that the CD thermal denaturation system is very sensitive to conformational changes caused by unusual binding of a substrate analog.
Structure and functional characterization of the periplasmic N‐terminal polypeptide domain of the sugar‐specific ion channel protein (ScrY porin)
Authors: Michels Jenny , Geyer Armin , Mocanu Viorel , Welte Wolfram , Burlingame Alma L. , Przybylski Michael
Published: July 2002

The structure of the sucrose‐specific porin (ScrY) from Salmonella typhimurium has been elucidated by X‐ray crystallography to consist of 18 antiparallel β‐strands, associated as a trimer complex similar to ion‐transport channels. However, the 71‐amino‐acid‐residue N‐terminal periplasmic domain was not determined from the crystal structure due to the absence of sufficient electron density. The N‐terminal polypeptide contains a coiled‐coil structural motif and has been assumed to play a role in the sugar binding of ScrY porin. In this study the proteolytic stability and a specific proteolytic truncation site at the N‐terminal domain were identified by the complete primary structure characterization of ScrY porin, using MALDI mass spectrometry and post‐source‐decay fragmentation. The secondary structure and supramolecular association of the coiled‐coil N‐terminal domain were determined by chemical synthesis of the complete N‐terminal polypeptide and several partial sequences and their spectroscopic, biophysical, and mass spectrometric characterization. Circular dichroism spectra revealed predominant α‐helical conformation for the putative coiled‐coil domain comprising residues 4–46. Specific association to both dimer and trimer complexes was identified by electrospray ionization mass spectra and was ascertained by dynamic light scattering and electrophoresis data. The role of the N‐terminal domain in sugar binding was examined by comparative TR‐NOE‐NMR spectroscopy of the complete ScrY porin and a recombinant mutant, ScrY(Δ1–62), lacking the N‐terminal polypeptide. The TR‐NOE‐NMR data showed a strong influence of ScrY porin on the sugar‐binding affinity and suggested a possible function of the periplasmic N terminus for supramolecular stabilization and low‐affinity sugar binding.
Physicochemical consequences of the perdeuteriation of glutathione S‐transferase from S. japonicum
Authors: Brockwell David , Yu Lu , Cooper Serena , Mccleland Steven , Cooper Alan , Attwood David , Gaskell Simon J. , Barber Jill
Published: July 2002

Glutathione S‐transferase (GST) from Schistosoma japonicum has been prepared in both normal protiated (pGST) and fully deuteriated (dGST) form by recombinant DNA technology. Electrospray mass spectrometry showed that the level of deuteriation in dGST was 96% and was homogeneous across the sample. This result is attributed to the use of a deuterium‐tolerant host Escherichia coli strain in the preparation of the protein. 10 heteroatom‐bound deuteriums (in addition to the carbon‐bound deuteriums) were resistant to exchange when dGST was incubated in protiated buffer. The physicochemical and biological properties of the two proteins were compared. dGST was relatively less stable to heat denaturation and to proteolytic cleavage than was pGST. The midpoint transition temperature for pGST was 54.9°C, whereas that for dGST was 51.0°C. Static light‐scattering measurements revealed that the association behavior of dGST is also different from that of pGST. The perdeuteriated enzyme shows a tendency to associate into dimers of the fundamental dimer. This is in contrast with results that have been obtained for other perdeuteriated proteins in which perdeuteriation has been shown to promote dissociation of aggregates. dGST showed a similar Km to pGST; similar results had been obtained previously with bacterial alkaline phosphatase. However, whereas the alkaline phosphatase showed a reduced rate of catalysis on deuteriation, dGST exhibited a slightly higher rate of catalysis than pGST. It is clear that the bulk substitution of deuterium for protium has significant effects on the properties of proteins. Until many more examples have been studied, it will be difficult to predict these effects for any given protein. Nevertheless, deuteriation represents an intriguing method of preparing functional analogs of recombinant proteins.
Tyrosine kinases enhance the function of glycine receptors in rat hippocampal neurons and human α1β glycine receptors
Authors: Caraiscos Valerie B. , Mihic S. John , MacDonald John F. , Orser Beverley A.
Published: July 2002

Glycine receptors (GlyRs) are transmitter‐gated channels that mediate fast inhibitory neurotransmission in the spinal cord and brain. The GlyR β subunit contains a putative tyrosine phosphorylation site whose functional role has not been determined. To examine if protein tyrosine kinases (PTKs) regulate the function of GlyRs, we analysed whole‐cell currents activated by applications of glycine to CA1 hippocampal neurons and spinal neurons. The role of a putative site for tyrosine phosphorylation at position 413 of the β subunit was examined using site‐directed mutagenesis and expression of recombinant (α1βY413F) receptors in human embryonic kidney (HEK 293) cells. Lavendustin A, an inhibitor of PTKs, depressed glycine‐evoked currents (IGly) in CA1 neurons and spinal neurons by 31 % and 40 %, respectively. In contrast, the intracellular application of the exogenous tyrosine kinase, cSrc, enhanced IGly in CA1 neurons by 56 %. cSrc also accelerated GlyR desensitization and increased the potency of glycine 2‐fold (control EC50= 143 μm; cSrc EC50= 74 μm). Exogenous cSrc, applied intracellularly, upregulated heteromeric α1β receptors but not homomeric α1 receptors. Substitution mutation of the tyrosine to phenylalanine at position β‐413 prevented this enhancement. Furthermore, a selective inhibitor of the Src family kinases, PP2, down‐regulated wild‐type α1β but not α1βY413F receptors. Together, these findings indicate that GlyR function is upregulated by PTKs and this modulation is dependent on the tyrosine‐413 residue of the β subunit.
The Flexural Response of a Submarine Pipeline to an Underwater
Explosion Bubble
Authors: Zong Z. , Lam K. Y.
Published: July 2002

The flexural response of a submarine pipeline to an underwater explosion bubble is studied in this paper. A simple model for estimating bubble evolution with time and predicting bubble-induced pressure is introduced. A detailed analysis is given to estimate the fluid force acting on the pipeline. Finally, the fluid-structure interaction equation is given and an approximate solution is found using modal superposition method. The response features are discussed. The relation between pipeline length and maximum stresses is investigated. [S0892-7219(00)00303-4]
Formation of Surface Microcrack for Separation of Nonmetallic Wafers Into Chips
Authors: Elperin T. , Kornilov A. , Rudin G.
Published: July 2002

In recent years a technology for a high quality separation of nonmetallic materials into chips using a surface (“blind”) microcrack attracted considerable attention in the electronic industry. In this method a wafer is positioned on the translated X-Y table and is heated by a laser beam up to a temperature of the order of 300–400°C. The wafer is then cooled by an air-water spray, and a surface microcrack is formed due to relaxation of the thermal stresses. The initial microcrack with a depth of the order of several hundred microns then propagates in a subsurface region of a wafer and follows the path of the laser beam. Theoretical modeling based on the solution of the equations of thermal elasticity was performed to determine the distributions of temperature and thermal stresses that cause formation of an “edge” microcrack (at the edge of a wafer) followed by its transformation into a surface microcrack. The results of thermal stresses analysis are in an agreement with experimental observations. [S1043-7398(00)00804-5]
One-Dimensional Performance Prediction of Subsonic Vaned Diffusers
Authors: Ribi Beat , Dalbert Peter
Published: July 2002

A simple one-dimensional theory to predict the performance of a diffuser using as few empirical factors as possible is presented. The prediction method uses two empirical functions to assess both the pressure recovery and the losses. The functions have been calibrated from experimental data from the company’s standard diffusers. The method is, however, adaptable for any type of subsonic vaned diffusers, provided that the empirical functions can be calibrated from measurements. The pressure rise in the diffuser is calculated from the continuity equation, taking into account the blockage, while the losses are determined by means of displacement and momentum thickness. These values are calculated at design point from an integral boundary layer calculation. To take into account the influence of flow separation at off-design, the calculated displacement and momentum thickness are increased according to empirical functions. When designing a new impeller, the method provides a simple way to evaluate the diffuser, resulting in the best combination in terms of efficiency and range. It further provides a simple means of estimating the change to be expected in a known stage performance characteristic due to a modification of the diffuser geometry.[S0889-504X(00)01703-7]
Decentralized Feedback Control of Broadband Duct Noise with Nodal Placement of Colocated Actuator-Sensor Pairs
Authors: Jayachandran V. , Petrova Maria V. , Li Florence J. , King Patrick , Meyer Nancy E. , Sun J. Q.
Published: July 2002

This paper presents experimental results from a demonstration of feedback control experiments on an open-ended acoustic duct, using nodally placed colocated actuator-sensor pairs. The disturbance signal used in the experiments is bandlimited and random. The first three modes undergo as much as 20 dB attenuation. The simplicity of the nodal control together with the spatially global sound reduction makes this a suitable technique for suppressing low frequency broadband duct noise.
On the Materials Requirements for a Solar Solid-Expansion Machine
Authors: Brinkworth B. J.
Published: July 2002

An outline is given of the mechanical and thermal histories of the working substance for a generic stand-alone solar thermal solid-expansion engine. A Figure-of-merit for the selection of materials is devised and evaluated, showing that high-strength engineering alloys figure best for this duty, with the carbon and low-alloy steels a practical choice. [S0199-6231(00)00403-2]
Editorial
Authors: Katz Joseph
Published: July 2002

[S0098-2202(00)02704-8]
Experimental Study of a Hydrogen-Fueled Engine
Authors: Sierens R. , Verhelst S.
Published: July 2002

The Laboratory of Transport Technology (Ghent University) converted a GM/Crusader V-8 engine for hydrogen use. The engine is intended for the propulsion of a midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air–fuel mixture in the intake manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing, injection timing and duration, injection pressure) are given. Special focus is given to topics related to the use of hydrogen as a fuel: ignition characteristics (importance of electrode distance), quality of the lubricating oil (crankcase gases with high contents of hydrogen), oxygen sensors (very lean operating conditions), and noise reduction (configuration and length of intake pipes). The advantages and disadvantages of a power regulation only by the air-to-fuel ratio (as for diesel engines) against a throttle regulation (normal gasoline or gas regulation) are examined. Finally, the goals of the development of the engine are reached: power output of 90 kW, torque of 300 Nm, extremely low emission levels, and backfire-safe operation.
Minimization of the Peak-to-Peak Gain in Periodic Systems Under Full State Feedback1
Authors: Aubrecht Johannes , Voulgaris Petros G.
Published: July 2002

The paper considers the minimization of the l∞-induced norm of the closed loop in linear periodically time varying (LPTV) systems when state information is available for feedback. A state-space approach is taken and concepts of viability theory and controlled invariance are utilized. It is shown that a memoryless periodically varying nonlinear controller can be constructed to achieve near-optimal performance. The construction involves the solution of several finite linear programs and generalizes to the periodic case earlier work on linear time-invariant systems (LTI).
Simulations of Channel Flows With Effects of Spanwise Rotation or Wall Injection Using a Reynolds Stress Model
Authors: Chaouat Bruno
Published: July 2002

Simulations of channel flows with effects of spanwise rotation and wall injection are performed using a Reynolds stress model. In this work, the turbulent model is extended for compressible flows and modified for rotation and permeable walls with fluid injection. Comparisons with direct numerical simulations or experimental data are discussed in detail for each simulation. For rotating channel flows, the second-order turbulence model yields an asymmetric mean velocity profile as well as turbulent stresses quite close to DNS data. Effects of spanwise rotation near the cyclonic and anticyclonic walls are well observed. For the channel flow with fluid injection through a porous wall, different flow developments from laminar to turbulent regime are reproduced. The Reynolds stress model predicts the mean velocity profiles, the transition process and the turbulent stresses in good agreement with the experimental data. Effects of turbulence in the injected fluid are also investigated.
Applications of the Impedance Method on Multiple Piezoelectric Actuators Driven Structures
Authors: Cheng C. C. , Wang P. W.
Published: July 2002

An impedance-based system modeling technique has been developed to determine the output forces of multiple piezoelectric (PZT) patch actuators on an active structure to produce a known vibration response. In the analysis of the dynamic response of a structure driven by multiple PZT patches, the proposed model includes not only the dynamic interactions between the PZT patch and the host structure but also the impedance couplings among PZT patches. Therefore this approach can apply to a structure with multiple PZT actuators. Furthermore, the bending stiffness and the thickness of a PZT patch that are proved to be important as increases of excitation frequency are included in the proposed impedance model. Examples are given to demonstrate how to synthesize a known vibration response and how to suppress vibration response at an arbitrary location on structures using this technique.
9 ppm NOx/CO Combustion System for “F” Class Industrial Gas Turbines
Authors: Vandervort C. L.
Published: July 2002

The Dry Low NOx (DLN) -2.6 combustion system has achieved emission rates of lower than 9 ppm NOx (dry, corrected to 15 percent O2) and CO from 50 to 100 percent load for the GE MS7001FA industrial gas turbine on natural gas. The system uses lean premixed combustion with fuel staging for low load stability. The first unit achieved commercial operation in March of 1996 with a firing temperature of 2350°F. As of September 9, 1999, it has accumulated over 11,800 hours of operation in peaking and base load service. Sixteen more units have since entered commercial service. Emissions data are shown for operation on natural gas. The DLN-2.6 system can operate on liquid fuel with water injection for NOx abatement. Power augmentation with steam injection is allowable while operating on natural gas. The premixed gas nozzles utilize swirl for flame stabilization. Aerodynamically shaped natural gas injectors are applied for flashback or flame-holding resistance.
Performance of a Vacuum Formed Chopped Ceramic Fiber Filter in a Reducing Environment
Authors: Ahluwalia R. K. , Novick V. J. , Zhang L. , Sutaria M. P. , Singh J. P.
Published: July 2002

A laboratory-scale apparatus has been used for unattended, long duration, continuous flow through testing of a vacuum formed chopped ceramic fiber filter under reducing conditions at atmospheric pressure. Four candle specimens were exposed from 150 to 3550 h to 600°C gas containing 4 percent CO, 11 percent H2, 12 percent CO2, 14 percent H2O, 59 percent N2, 1 ppmv NaCl, 50 ppmv H2S, and 1000–2000 ppmw ash from a transport reactor operated in gasification mode. A database was established on pressure drop of the as-received and exposed filter as a function of face velocity and temperature. Tests were conducted to investigate the effects of back-pulse parameters on filter regenerability. Results are reported on the critical reservoir pressure and pulse duration for maintaining a stable saw-tooth profile of pressure drop across the filter element. Data are obtained to characterize the effect of chemical and thermal aging on the apparent bulk density of the filter, pore size distribution, fast fracture strength, and microstructure. It is suggested that the compliant filter undergoes a slow process of rigidization upon exposure to the test environment.
On Saint-Venant’s Problem for an Inhomogeneous, Anisotropic Cylinder—Part II: Cross-Sectional Properties
Authors: Kosmatka J. B. , Lin H. C. , Dong S. B.
Published: July 2002

Cross-sectional properties of a prismatic inhomogeneous, anisotropic cylinder are determined from Saint-Venant solutions for extension-bending-torsion and flexure, whose method of construction was presented in a previous paper. The coupling of extensional, bending, and twisting deformations due to anisotropy and inhomogeneity leads to some very interesting features. Herein, it is shown that for an inhomogeneous, anisotropic cylinder whose cross-sectional plane is not a material symmetry plane, distinct modulus-weighted and compliance-weighted centroids and distinct principal bending axes are possible. A line of extension-bending centers is given on which an axial force causes extension and bending only but no twist. Two shear centers are given, one using the Griffith-Taylor definition that ignores cross-sectional warpages and the other by stipulating a zero mean rotation over the cross section. The center of twist is discussed, and this property depends on root end fixity conditions that are prescribed in terms of their mean values based on integrals over the cross section rather than by a pointwise specification. While these shear center and center of twist definitions have some rational bases, it is recognized that other definitions are possible, for example those based on modulus or compliance-weighted integrals. Two examples, an angle and a channel, both composed of a two-layer ±30 deg angle-ply composite material, illustrate the procedures for determining these cross-sectional properties.
Running Force in Medium to High-Curvature Wellbores: An Experimental Study and Numerical Simulation of Laboratory and Field Cases
Authors: Seibi Abdennour C.
Published: July 2002

This paper presents a novel approach to measure and estimate running force for various laboratory and field conditions. The experimental and simulation procedures of different rod/pipe sizes running through various laboratory/field conditions are described in detail. Tests were conducted on rods to measure the running force for various laboratory cases obtained from dimensional analysis. The generated experimental results were used to calibrate a typical laboratory finite element model from which calibrated parameters are used to estimate the running force for prescribed field cases. Both the experimental and simulated field results revealed that the running force depends on the radius of curvature, hole clearance, horizontal section, and contact scenario significantly. Stress analysis of pipes running through curved and horizontal sections showed that pipes undergo elastic and plastic deformation, and the nature of deformation depends on the pipe size and radius of curvature.
Anisotropic Elastic Materials With a Parabolic or Hyperbolic Boundary: A Classical Problem Revisited
Authors: Ting T. C. T. , Hu Y. , Kirchner H. O. K.
Published: July 2002

When an anisotropic elastic material is under a two-dimensional deformation that has a hole of given geometry Γ subjected to a prescribed boundary condition, the problem can be solved by mapping Γ to a circle of unit radius. It is important that (i) each point on Γ is mapped to the same point for the three Stroh eigenvalues p1,p2,p3 and (ii) the mapping is one-to-one for the region outside Γ. In an earlier paper it was shown that conditions (i) and (ii) are satisfied when Γ is an ellipse. The paper did not address to the case when Γ is an open boundary, such as a parabola or hyperbola that was studied by Lekhnitskii. We examine the mappings employed by Lekhnitskii for a parabola and hyperbola, and show that while the mapping for a parabola satisfies conditions (i) and (ii), the mapping for a hyperbola does not satisfy condition (i). Nevertheless, a valid solution can be obtained for the problem with a hyperbolic boundary, although the prescription of the boundary condition is restricted. We generalize Lekhnitskii’s solutions for general anisotropic elastic materials and for more general boundary conditions. Using known identities and new identities presented here, real form expressions are given for the displacement and hoop stress vector at the parabolic and hyperbolic boundary.
Velocity Measurements of Vortex Breakdown in an Enclosed Cylinder
Authors: Fujimura Kazuyuki , Yoshizawa Hiroaki , Iwatsu Reima , Koyama Hide S. , Hyun Jae Min
Published: July 2002

Experimental measurements were carried out of three-component velocity fields inside a cylindrical container. Flow was driven by the rotation of the top endwall disk. The purpose of the precision laser-Doppler velocimetry measurements was to describe the velocity characteristics pertinent to the vortex breakdown phenomenon. A turntable experimental apparatus was fabricated. Extensive laser-Doppler measurements, as well as flow visualizations, were made for the aspect ratio 1.50 and 2.50, and the Reynolds number ranges 0.99×103-2.20×103. The measured meridional velocities were found to be consistent with the prior visualization studies. The characteristic changes in swirling motions in the vicinity of vortex breakdown bubble are depicted. Detailed flow patterns near the rotating disk are constructed by using the experimental data.
Neural Network-Based Adaptive Monitoring System for Power Transformer
Authors: Ottele Andy , Shoureshi Rahmat
Published: July 2002

Power transformers are major elements of the electric power transmission and distribution infrastructure. Transformer failure has severe economical impacts from the utility industry and customers. This paper presents analysis, design, development, and experimental evaluation of a robust failure diagnostic technique. Hopfield neural networks are used to identify variations in physical parameters of the system in a systematic way, and adapt the transformer model based on the state of the system. In addition, the Hopfield network is used to design an observer which provides accurate estimates of the internal states of the transformer that can not be accessed or measured during operation. Analytical and experimental results of this adaptive observer for power transformer diagnostics are presented.
An Analytically Solvable Model for Biomechanical Response of the Cornea to Refractive Surgery
Authors: Djotyan Gagik P. , Kurtz Ron M. , Ferna´ndez Delia Cabrera , Juhasz Tibor
Published: July 2002

An analytically solvable model that considers the elasticity of the cornea is developed for use in the current and novel corneal refractive surgery procedures. The model assumes that the cornea is a thin spheroid shell with an elastic response to intraocular pressure. The value of the Young’s modulus of the post-operative cornea and its dependence on the geometric parameters of the ablation zone are estimated employing “best-fit” approach to nomograms currently used in corneal refractive surgery. These elasticity parameters are applied for quantitative modeling of different types of refractive surgery for myopia.
Modeling and Simulation of Traction Drive Dynamics and Control
Authors: Zou Z. , Zhang Y. , Zhang X. , Tobler W.
Published: July 2002

This paper presents an analytical model for the simulation of traction drive dynamics and control in ratio change processes. The model systematically incorporates the formulations on the kinematics, dynamics and control characteristics of traction drives. In the model, the motion parameters of traction drive components are coupled to CVT inputs and outputs, torque losses, as well as ratio variations. The characteristics of a dual-feedback ratio control system are formulated in Laplace transform and integrated into the overall CVT system. The model is implemented in Matlab/Simulink block diagrams and is capable of predicting traction drive performances under various ratio change conditions. The effectiveness of the model is illustrated in a numerical example by the comparison between the simulation and experimental data on key CVT performance parameters.
Nonlinear Stability of Circular Cylindrical Shells in Annular and Unbounded Axial Flow
Authors: Amabili M. , Pellicano F. , Pai¨doussis M. A.
Published: July 2002

The stability of circular cylindrical shells with supported ends in compressible, inviscid axial flow is investigated. Nonlinearities due to finite-amplitude shell motion are considered by using Donnell’s nonlinear shallow-shell theory; the effect of viscous structural damping is taken into account. Two different in-plane constraints are applied at the shell edges: zero axial force and zero axial displacement; the other boundary conditions are those for simply supported shells. Linear potential flow theory is applied to describe the fluid-structure interaction. Both annular and unbounded external flow are considered by using two different sets of boundary conditions for the flow beyond the shell length: (i) a flexible wall of infinite extent in the longitudinal direction, and (ii) rigid extensions of the shell (baffles). The system is discretized by the Galerkin method and is investigated by using a model involving seven degrees-of-freedom, allowing for traveling-wave response of the shell and shell axisymmetric contraction. Results for both annular and unbounded external flow show that the system loses stability by divergence through strongly subcritical bifurcations. Jumps to bifurcated states can occur well before the onset of instability predicted by linear theory, showing that a linear study of shell stability is not sufficient for engineering applications.
Formation of Air Core in Nozzles With Tangential Entry
Authors: Dash S. K. , Halder M. R. , Peric M. , Som S. K.
Published: July 2002

The process of formation of air core and its development with time, inside one cylindrical and one conical nozzle having two tangential entries, has been analyzed experimentally and numerically. Experiments have been carried out using Plexiglas nozzles and water in ambient air; the air core has then been photographed for different nozzles and flow parameters. Numerical simulations have been performed using a finite volume method that employs unstructured grids with cell-wise local refinement and an interface-capturing scheme to predict the shape of the air core. The shape of the air core inside the cylindrical nozzle is found to be helicoidal at steady state for higher inlet velocity, whereas the shape of the free surface remains nearly cylindrical for low inlet velocity. In the conical nozzle, the air core is nearly axisymmetric in experiments. So only two-dimensional simulations are performed; the air core widens at the end of conical section as it approaches nozzle exit. For both nozzles numerical simulation predicts qualitatively and to a large extent also quantitatively the correct shape of the air core and the angle of the spray at the nozzle exit, as verified by comparisons with experimentally observed shapes.
A Cable Extension Transducer Based Two-Dimensional Position Sensor for Industrial Applications
Authors: Hong Daehie , Mueller Keith J. , Velinsky Steven A.
Published: July 2002

A technique for two-dimensional position measurement is presented through the use of cable-extension transducers. The method includes the use of two such transducers and the planar position is determined through triangulation. This paper also presents a design methodology for the sensor system which is developed based on uncertainty analysis results. The performance of the sensor system is verified through experiments with coordinate measurement machines. This new type of position sensor can be easily used in a wide variety of automation applications in industry for two-dimensional position measurements with high accuracy over a relatively large range, and it is both cost effective and robust against hostile environments.
Transient Coupled Radiation and Conduction in a Three-Layer Composite
With Semitransparent Specular Interfaces and Surfaces
Authors: Tan He-Ping , Luo Jian-Feng , Xia Xin-Lin
Published: July 2002

Transient coupled radiative and conductive heat transfer in a three-layer absorbing and isotropically scattering composite with semitransparent specular interfaces and surfaces is investigated. The transient energy equation is solved by the full implicit control-volume method in combination with spectral band model. The radiative heat source term is calculated by the radiative transfer coefficients (RTCs), which are deduced by the ray tracing method in combination with Hottel and Sarofim’s zonal method (Hottel H. C., and Sarofim A. F., 1967, Radiative Transfer, McGraw-Hill Book Company, New York). The effects of extinction coefficient, refractive index, and scattering albedo etc., on coupled heat transfer are studied under radiative and convective boundary conditions. The effect of isolating space on coupled heat transfer and the appearance of temperature peaks within the composite are investigated. It is found that temperature peaks also appear in the inner parts of an inhomogeneous semitransparent medium layer even though there is no convection cooling on the surfaces. This occurs when the absorbing coefficient of inner parts is higher than that of the parts close to the surfaces, and the two surfaces are semitransparent and subjected to an external radiation.
A Test Rig for Frictionally Damped Bladed Segments
Authors: Berruti T. , Filippi S. , Goglio L. , Gola M. M. , Salvano S.
Published: July 2002

The paper describes the development of an instrumented test rig suitable to carry out vibration testing of the bladed segments of a turbine (belonging to a stator low pressure stage) in which the friction occurring at the contact of neighboring segments is used in service to damp the vibrations. The system is able to assign the desired preload to the segment and to measure the forces exerted in the contact and the relative displacements due to slipping. The main results that can be obtained concern the type of motion that takes place (stick/slip) and the effect of the interlocking on it, the friction coefficients, the contact tangential stiffness, and, more generally, the frequency response.
Flexible Bearing Supports, Using Experimental Data
Authors: Vázquez J. A. , Barrett L. E. , Flack R. D.
Published: July 2002

A laboratory rotor, representing a scaled-down model of a three-stage compressor supported by fluid film bearings on anisotropic flexible supports was analyzed. The support characteristics were measured at the bearing locations by exciting the bearing housings with electromechanical shakers and measuring the acceleration. Direct, cross-coupled, and cross-talk accelerance between supports were measured. Unbalance response and stability analyses of the rotor were performed using polynomial transfer functions extracted from the measured accelarance data. The predicted critical speeds and instability threshold agree with measured data. Predictions using other support models are included to show the effectiveness of this method.
Multimode Approach to Nonlinear Supersonic Flutter of Imperfect Circular Cylindrical Shells
Authors: Amabili M. , Pellicano F.
Published: July 2002

The aeroelastic stability of simply supported, circular cylindrical shells in supersonic flow is investigated by using both linear aerodynamics (first-order piston theory) and nonlinear aerodynamics (third-order piston theory). Geometric nonlinearities, due to finite amplitude shell deformations, are considered by using the Donnell’s nonlinear shallow-shell theory, and the effect of viscous structural damping is taken into account. The system is discretized by Galerkin method and is investigated by using a model involving up to 22 degrees-of-freedom, allowing for travelling-wave flutter around the shell and axisymmetric contraction of the shell. Asymmetric and axisymmetric geometric imperfections of circular cylindrical shells are taken into account. Numerical calculations are carried out for a very thin circular shell at fixed Mach number 3 tested at the NASA Ames Research Center. Results show that the system loses stability by travelling-wave flutter around the shell through supercritical bifurcation. Nonsimple harmonic motion is observed for sufficiently high post-critical dynamic pressure. A very good agreement between theoretical and existing experimental data has been found for the onset of flutter, flutter amplitude, and frequency. Results show that onset of flutter is very sensible to small initial imperfections of the shells. The influence of pressure differential across the shell skin has also been deeply investigated. The present study gives, for the first time, results in agreement with experimental data obtained at the NASA Ames Research Center more than three decades ago.
Relationship Between Rockwell C Hardness and Inelastic Material
Constants
Authors: Hirano Akihiko , Sakane Masao , Hamada Naomi
Published: July 2002

This paper describes the relationship between Rockwell C hardness and elastic-plastic material constants by using finite element analyses. Finite element Rockwell C hardness analyses were carried out to study the effects of friction coefficient and elastic-plastic material constants on the hardness. The friction coefficient and Young’s modulus had no influence on the hardness but the inelastic materials constants, yield stress, and strain hardening coefficient and exponent, had a significant influence on the hardness. A new equation for predicting the hardness was proposed as a function of yield stress and strain hardening coefficient and exponent. The equation evaluated the hardness within a ±5% difference for all the finite element and experimental results. The critical thickness of specimen and critical distance from specimen edge in the hardness testing was also discussed in connection with JIS and ISO standards.
Application of a Unified Viscoplastic Model With Mixed Hardening to
Ionic Solids and Metallic Alloys
Authors: Yahya O. M. L. , Aubertin M.
Published: July 2002

The mechanical behavior of different types of polycrystalline materials shows many common features in the ductile inelastic flow regime. It is typically controlled by dislocations motion, which involves the competitive action of hardening and recovery processes that induces a strong dependency upon mechanical history. The object of this paper is to show how a constitutive model, named SUVIC, can be used to describe and predict in a unified manner the inelastic response of various types of materials. For that purpose, the authors use laboratory test results obtained on alkali halides (NaCl) and on metallic alloys (Inconel 738LC and A508 steel) at different homologous temperatures.
Multi-State Transient Rotor Vibration Control Using Sampled Harmonics
Authors: Keogh P. S. , Cole M. O. T , Burrows C. R.
Published: July 2002

A technique is introduced to achieve transient vibration attenuation in a multi-input, multi-output flexible rotor/magnetic bearing system. The strategy employs feedback control of measured harmonic components of rotor vibration. Whereas previous harmonic controllers have been based only on steady state vibration characteristics, the new controller also incorporates the transient dynamics. The controller may still be designed from measured data and is determined from target transient vibrational responses arising from step changes in particular disturbances. Account is taken of delays arising from evaluation of harmonic components. Furthermore, stability boundaries for the controller are shown to have significant tolerance to measurement error. The controller is validated experimentally in a flexible rotor/magnetic bearing system and mass loss tests are used to demonstrate rapid decrease in vibration levels with near elimination of transient overshoot.
An Analysis of Turbulent Shear Stresses in Leakage Flow Through a Bileaflet Mechanical Prostheses
Authors: Travis Brandon R. , Leo Hwa L. , Shah Parina A. , Frakes David H. , Yoganathan Ajit P.
Published: July 2002

In this work, estimates of turbulence were made from pulsatile flow laser Doppler velocimetry measurements using traditional phase averaging and averaging after the removal of cyclic variation. These estimates were compared with estimates obtained from steady leakage flow LDV measurements and an analytical method. The results of these studies indicate that leakage jets which are free and planar in shape may be more unstable than other leakage jets, and that cyclic variation does not cause a gross overestimation of the Reynolds stresses at large distances from the leakage jet orifice.
Vibration Behavior and Simplified Design of Thick Rectangular Plates
With Variable Thickness
Authors: Sasajima M. , Kakudate T. , Narita Y.
Published: July 2002

A free vibration analysis and an optimal design approach have been presented for thick isotropic rectangular plates with varying thickness under general edge conditions. First, the analysis is developed for vibrating rectangular plates by using the Mindlin plate theory and an eigenvalue problem is formulated by extending a method of Ritz to arbitrary sets of standard boundary conditions. The classical plate theory is also used to derive the frequency equation for comparison purpose. Secondly, a simplified optimal design approach is proposed to maximize the fundamental frequency of the plates. In applying this approach, the thickness variation is assumed to be linear in one direction and a taper ratio is chosen to be a design variable that represents the whole plate design. This approach significantly reduces the process for obtaining optimal or nearly optimal design under constraint of the constant plate volume. Numerical results are presented for various sets of boundary conditions, thickness ratio and two different plate theories, and their effects on the optimal taper ratio and its corresponding maximized fundamental frequency are discussed.