bluuebunny/crossref_metadata_2025 huggingface dataset:
An empirical investigation of agency relationships and capital structure of property management firms in the UK
Authors: Theis John , Casey Michael
Published: July 2002

This study examines the relationship between various agency factors and debt of property management firms in the UK. Findings indicate that debt is significantly inversely related to percentage of shares closely held, dividend yield and price‐to‐book ratio. Size, measured by sales volume, appears to be insignificant in determining debt level.
Crashing of stochastic processes by sampling and optimisation
Authors: Gutjahr Walter J. , Strauss Christine , Toth Martin
Published: July 2002

The application of advanced methods of process management is essential, especially in those fields in which activity durations can be determined only vaguely, while at the same time a highly competitive market enforces strict completion schedules through the implementation of penalties. The technique presented is most suitable for determining a time‐cost trade‐off based on practice‐relevant assumptions. Completion time overruns usually cause penalties whose size depends on the degree of the overruns. To avoid such penalties – or at least to keep any losses low – distinct processes may be crashed by one or several measures that decrease the activity duration. The risk of an overrun has to be weighed against the expected costs and benefits of certain crashing measures and their combinations. The technique presented is a new PERT‐based, hybridised approach using simulated annealing and importance sampling to support typical process re‐engineering, which focuses on the efficient allocation of extra resources in order to achieve a more reliable performance without changing the precedence‐successor‐structure.
Conformational and thermodynamic properties of peptide binding to the human S100P protein
Authors: Gribenko Alexey V. , Guzmán‐Casado Mercedes , Lopez Maria M. , Makhatadze George I.
Published: July 2002

S100P is a member of the S100 subfamily of calcium‐binding proteins that are believed to be associated with various diseases, and in particular deregulation of S100P expression has been documented for prostate and breast cancer. Previously, we characterized the effects of metal binding on the conformational properties of S100P and proposed that S100P could function as a Ca2+ conformational switch. In this study we used fluorescence and CD spectroscopies and isothermal titration calorimetry to characterize the target‐recognition properties of S100P using a model peptide, melittin. Based on these experimental data we show that S100P and melittin can interact in a Ca2+‐dependent and ‐independent manner. Ca2+‐independent binding occurs with low affinity (Kd ≈ 0.2 mM), has a stoichiometry of four melittin molecules per S100P dimer and is presumably driven by favorable electrostatic interactions between the acidic protein and the basic peptide. In contrast, Ca2+‐dependent binding of melittin to S100P occurs with high affinity (Kd ≈ 5 μM) has a stoichiometry of two molecules of melittin per S100P dimer, appears to have positive cooperativity, and is driven by hydrophobic interactions. Furthermore, Ca2+‐dependent S100P‐melittin complex formation is accompanied by significant conformational changes: Melittin, otherwise unstructured in solution, adopts a helical conformation upon interaction with Ca2+‐S100P. These results support a model for the Ca2+‐dependent conformational switch in S100P for functional target recognition.
A general method for the quantitative analysis of functional chimeras: Applications from site‐directed mutagenesis and macromolecular association
Authors: Luong Tinh N. , Kirsch Jack F.
Published: July 2002

Two new parameters, I and C, are introduced for the quantitative evaluation of functional chimeras: I (impact) and C (context dependence) are the free energy difference and sum, respectively, of the effects on a given property measured in forward and retro chimeras. The forward chimera is made by substitution of a part “a” from ensemble A into the analogous position of homologous ensemble B (SB → A). The C value is a measure of the interaction of the interrogated position with its surroundings, whereas I is an expression of the quantitative importance of the probed position. Both I and C vary with the evaluated property, for example, kinetics, binding, thermostability, and so forth. The retro chimera is the reverse substitution of the analogous part “b” from B into A, SA → B. The I and C values derived from original data for forward and retro mutations in aspartate and tyrosine aminotransferase, from literature data for quasi domain exchange in oncomodulin and for the interaction of Tat with bovine and human TAR are evaluated. The most salient derived conclusions are, first, that Thr 109 (AATase) or Ser 109 (TATase) is an important discriminator for dicarboxylic acid selectivity by these two enzymes (I < −2.9 kcal/mol). The T109S mutation in AATase produces a nearly equal and opposite effect to S109T in TATase (C < 0.4 kcal/mol). Second, an I value of 5.5 kcal/mol describes the effects of mirror mutations D94S (site 1) and S55D (site 2) in the Ca2+ binding sites of oncomodulin on Ca2+ affinity. The second mirror set, G98D (site 1) and D59G (site 2), yields a smaller impact (I = −3.4 kcal/mol) on Ca2+ binding; however, the effect is significantly more nearly context independent (C = −0.6 versus C = −2.7 kcal/mol). Third, the stem and loop regions of HIV and BIV TAR are predominantly responsible for the species specific interaction with BIV Tat65–81 (I = −1.5 to −1.6 kcal/mol), whereas I = 0.1 kcal/mol for bulge TAR chimeras. The C values are from −0.3 to −1.2 kcal/mol. The analysis described should have important applications to protein design.
pH‐induced conformational transitions of a molten–globule–like state of the inhibitory prodomain of furin: Implications for zymogen activation
Authors: Bhattacharjya Surajit , Xu Ping , Xiang Hui , Chrétien Michel , Seidah Nabil G. , Ni Feng
Published: July 2002

The endoprotease furin, which belongs to the family of mammalian proprotein convertase (PC), is synthesized as a zymogen with an N‐terminal, 81‐residue inhibitory prodomain. It has been shown that the proenzyme form of furin undergoes a multistep ‘autocatalytic’ removal of the prodomain at the C‐terminal side of the two consensus sites, R78‐T‐K‐R81∼ and R44‐G‐V‐T‐K‐R49∼. The furin‐mediated cleavage at R44‐G‐V‐T‐K‐R49∼, in particular, is significantly accelerated in an ‘acidic’ environment. Here, we show that under neutral pH conditions, the inhibitory prodomain of furin is partially folded and undergoes conformational exchanges as indicated by extensive broadening of the NMR spectra. Presence of many ring‐current shifted methyl resonances suggests that the partially folded state of the prodomain may still possess a ‘semirigid’ protein core with specific packing interactions among amino acid side chains. Measurements of the hydrodynamic radii and compaction factors indicate that this partially folded state is significantly more compact than a random chain. The conformational stability of the prodomain appears to be pH sensitive, in that the prodomain undergoes an unfolding transition towards acidic conditions. Our NMR analyses establish that the acid‐induced unfolding is mainly experienced by the residues from the C‐terminal half of the prodomain (residues R44–R81) that contains the two furin cleavage sites. A 38‐residue peptide fragment derived from the entire pH‐sensitive C‐terminal region (residues R44–R81) does not exhibit any exchange‐induced line broadening and adopts flexible conformations. We propose that at neutral pH, the cleavage site R44‐G‐V‐T‐K‐R49∼ is buried within the protein core that is formed in part by residues from the N‐terminal region, and that the cleavage site becomes exposed under acidic conditions, leading to a facile cleavage by the furin enzyme.
Numerical and Experimental Study of Strain Rate Effects in Laser Forming
Authors: Li Wenchuan , Yao Y. Lawrence
Published: July 2002

Experimental investigation and numerical simulation of the influence of the strain rate in laser forming are presented. To isolate and effectively study the strain rate effects, which are temperature dependent, a “constant peak temperature” method is developed with the aid of numerical modeling and solution. Under the condition of the constant peak temperature, the effects of strain rate on forming efficiency, residual stress and hardness of the formed parts are studied both experimentally and numerically. In the numerical model, the temperature dependence and strain-rate dependence of the flow stress and other material properties are considered. The simulation results are consistent with the experimental observations. [S1087-1357(00)01004-2]
Forward and Inverse Acceleration Analyses of In-Parallel Manipulators
Authors: Martı´nez Jose´ Marı´a Rico , Duffy Joseph
Published: July 2002

Simple expressions for the forward and inverse acceleration analyses of a six degree of freedom in-parallel manipulator are derived. The expressions are obtained by firstly computing the “accelerator” for a single Hooke-Prismatic-Spheric, HPS for short, connector chain in terms of the joint velocities and accelerations. The accelerator is a function of the line coordinates of the joint axes and of a sequence of Lie products of the same line coordinates. A simple expression for the acceleration of the prismatic actuator is obtained by forming the Klein form, or reciprocal product, with the accelerator and the coordinates of the line of the connector chain. Since the Klein form is invariant, the resulting expression can be applied directly to the six HPS connector chains of an in-parallel manipulator. As a required intermediate step, this contribution also derives the corresponding solutions for the forward and inverse velocity analyses. The authors believe that this simple method has applications in the dynamics and control of these in-parallel manipulators where the computing time must be minimized to improve the behavior of parallel manipulators. [S1050-0472(00)01303-9]
The Deformation Habits of Compressed Open-Cell Solid Foams
Authors: Wang Y. , Gioia G. , Cuitin˜o A. M.
Published: July 2002

Compressed open-cell solid foams frequently exhibit spatially inhomogeneous distributions of local stretch. The theoretical aspects of this deformation habit have not been clearly elucidated. Here we briefly discuss the energetics of the problem to show that the stretch inhomogeneity stems from the nonconvexity of the underlying potential. We also perform displacement field measurements using the Digital Image Correlation technique, and discuss the results in light of the theory. [S0094-4289(00)01904-6]
Phase-Locked Mode Stability for Coupled van der Pol Oscillators
Authors: Storti Duane W. , Reinhall Per G.
Published: July 2002

The critical variational equation governing the stability of phase-locked modes for a pair of diffusively coupled van der Pol oscillators is presented in the form of a linear oscillator with a periodic damping coefficient that involves the van der Pol limit cycle. The variational equation is transformed into a Hill’s equation, and stability boundaries are obtained by analytical and numerical methods. We identify a countable set of resonances and obtain expressions for the associated stability boundaries as power series expansions of the associated Hill determinants. We establish an additional “zero mean damping” condition and express it as a Pade´ approximant describing a surface that combines with the Hill determinant surfaces to complete the stability boundary. The expansions obtained are evaluated to visualize the first three resonant surfaces which are compared with numerically determined slices through the stability boundaries computed over the range 0.4<ε<5. [S0739-3717(00)00502-X]
Influence of Workpiece Surface Topography on the Mechanisms of Liquid Lubrication in Strip Drawing
Authors: Shimizu Ichiro , Andreasen Jan L. , Bech Jakob I. , Bay Niels
Published: July 2002

The workpiece surface topography is an important factor controlling the mechanisms of lubrication in metal forming processes. In the present work, the microscopic lubrication mechanisms induced by lubricant trapped in pockets of the surface in strip drawing are studied. The experiments are performed with macroscopic model pockets in the surface studying the influence of the shape of the pockets on the lubrication mechanisms. A large radius of curvature on the rear edge and a small angle to the edge of the lubricant pocket induce a large area of backward escape of lubrication caused by microplasto hydrodynamic lubrication (MPHDL). On the other hand, when the radius on the edge is small MPHDL is impeded and microplasto hydrostatic lubrication appears instead implying forward escape of the lubricant. The occurrence of these mechanisms are quantitatively explained by a mathematical model combining a slab method of analysis of the strip drawing process and an analysis of lubricant escape by Reynolds equation.
On the Relation Between the L-Integral and the Bueckner Work-Conjugate Integral
Authors: Shi, J. P. , Liu, and X. H. , Li J. M.
Published: July 2002

A simple but inherent relation between the L-integral and the Bueckner work conjugate integral is deduced for crack problem in isotropic, anisotropic, and dissimilar materials, respectively. It is proved the L-integral, from the mathematical point of view as well as in principle, is arising from the Betti’s reciprocal theorem. [S0021-8936(00)00103-3]
Buckling Optimization of Composite Axisymmetric Cylindrical Shells Under Uncertain Loading Combinations
Authors: de Faria A. R. , Hansen J. S.
Published: July 2002

Optimal elastic buckling loads of composite axisymmetric circular cylinders under uncertain loading conditions are investigated. The mechanical loads applied to the cylinder are a combination of axial compression, lateral pressure, and torsion. Additionally, these loads are allowed to vary within a certain class of admissible loads during the optimization search, as opposed to the restriction of fixed loads in the traditional optimization. The consideration of a degree of uncertainty in the mechanical loads leads to optimal designs which are inherently insensitive to perturbations and/or randomness in the applied loads.
Dynamic Singular Moments in a Perfectly Conducting Mindlin Plate With a Through Crack Under a Magnetic Field
Authors: Shindo Y. , Ohnishi I. , Toyama S.
Published: July 2002

Following Mindlin’s theory of plate bending of magnetoelasticity, we consider the scattering of time-harmonic flexural waves by a through crack in a perfectly conducting plate under a uniform magnetic field normal to the crack surface. An incident wave giving rise to moments symmetric about the crack plane is applied. It is assumed that the plate has the electric and magnetic permeabilities of the free space. By the use of Fourier transforms we reduce the problem to solving a pair of dual integral equations. The solution of the dual integral equations is then expressed in terms of a Fredholm integral equation of the second kind. The dynamic moment intensity factor versus frequency is computed and the influence of the magnetic field on the normalized values is displayed graphically. It is found that the existence of the magnetic field produces lower singular moments near the crack tip. [S0021-8936(00)02603-9]
Bending Moment Capacity of Pipes
Authors: Hauch So̸ren R. , Bai Yong
Published: July 2002

In this paper, the bending moment capacity for metallic pipes has been investigated to provide criteria for optimizing the cost effectiveness in pipeline seabed intervention design. An analytical solution for the ultimate load-carrying capacity of pipes subjected to combined pressure, longitudinal force, and bending has been derived and thoroughly compared against results obtained by the finite element method. The derived equations can be used for high-strength materials with isotropic as well as anisotropic stress/strain characteristics, and may be applied for pipelines, risers, and piping if safety factors are calibrated in accordance with appropriate target safety levels. [S0892-7219(00)00504-5]
Nonlinear Transient Localization and Beat Phenomena Due to Backlash in a Coupled Flexible System
Authors: Ma Xianghong , Vakakis Alexander F.
Published: July 2002

Transient nonlinear localization and beat phenomena are studied in a system of two rods coupled with a nonlinear backlash spring. The method of Karhunen-Loeve (K-L) decomposition is used to reduce the order of the dynamics, and to study nonlinear effects by considering energy transfers between leading K-L modes. The computed K-L modes are used to discretize the governing partial differential equations, thus creating accurate and computationally efficient low-dimensional nonlinear models of the system. Reconstruction of transient nonlinear responses using these low dimensional models reveals the accuracy of the order reduction. Poincare´ maps are utilized to study the nonlinear localization and beat phenomena caused by the clearance connecting the coupled rods.
On the Propagation of Lu¨ders Bands in Steel Strips
Authors: Kyriakides S. , Miller J. E.
Published: July 2002

The initiation and propagation of Lu¨ders-type localized deformation in thin, fine grained steel strips in tension is studied through combined experimental and analytical efforts. Purely elastic deformation is terminated (upper yield stress) by localized deformation which tends to initiate along preferred directions. The strain level associated with this material instability is limited to two to five percent. When this strain level is achieved locally, the instability propagates via inclined fronts which separate coexisting regions of essentially elastic and plastically deformed materials. Under displacement controlled stretching, one or two fronts propagate in a steady-state manner (lower yield stress). The propagation of one and two fronts are simulated numerically using finite element models in which the material is modeled as a finitely deforming elastoplastic solid with an up-down-up nominal stress-strain response. The simulations capture the major events observed in the experiments such as the initiation process, the propagation of inclined fronts, kinking of the strip and the build up of moments, and the periodic straightening and moment reduction through transient events. This confirms that structural effects play a major role in the evolution of observed events. [S0021-8936(00)01604-4]
Performance of a Large Parabolic Trough Solar Water Heating System at Phoenix Federal Correctional Institution
Authors: May Ken , Barker Greg , Hancock Ed , Walker Andy , Dominick Jeff , Westby Bob
Published: July 2002

At Phoenix Federal Correctional Institution in Arizona, the Federal Bureau of Prisons (FBP) completed a 1,584 m2 (17,040 square feet) parabolic trough solar water heating system financed, installed and operated under an Energy Savings Performance Contract (ESPC) with Industrial Solar Technology Corp (IST). The ESPC was developed under a Cooperative Research and Development Agreement with the National Renewable Energy Laboratory (NREL). The system incorporates a 87 m3 (23,000 gallon) storage tank. The system delivered 1,161,803 kWh (3,964 million Btu) of solar heat from March 1, 1999 to February 29, 2000. This energy would have cost $77,805.74 if purchased from the utility (based on the monthly average $/kWh cost). Sale of this energy to the prison provided $70,025.18 in revenue to IST (a rate negotiated at 90 percent of the monthly average $/kWh utility cost). Thus, the prison saved $7,780.56 (the remaining 10 percent). A photograph of the collector system is presented in Figure 1. Results show that the system delivers heat reliably, with only minor operational problems which are listed and discussed. The system delivered a minimum of 80,315 kWh (274 Btu) in January 2000 to a maximum of 130,979 kWh (447 Million Btu) in October 1999. The prison pays IST for energy delivered by the solar system at a rate equal to 90 percent of the monthly average utility rate (10 percent guaranteed savings), over 20 years. Details of the establishment of the payment structure and the cost savings to the prison are discussed. Annual Emissions Savings are estimated by EPA multipliers [1] for Arizona as 627,374 kg/yr of CO2, 2,324 kg/yr of SO2 and 2,297 kg/yr of NOx. Other benefits to the prison are also discussed, such as reduced operations and maintenance on the electric water heaters and a greater capacity to deliver hot water. [S0199-6231(00)00704-8]
Bend Angle Effect on B2 and C2 Stress Indices for Piping Elbows
Authors: Kumar Rajnish , Saleem Mohammad A.
Published: July 2002

B 2 and C2 stress indices are used for calculation of stress terms corresponding to moment loading in evaluation of nuclear piping components. The formulas given in the ASME Boiler & Pressure Vessel Code for calculating these indices for elbows and curved pipes are independent of the bend angle. The objective of this investigation was to study the effect of the bend angle on the values of B2 and C2. For this purpose, elbows with sizes ranging from 2.5 to 20 in. have been studied. The values of B2 and C2 have been calculated by detailed analysis using finite element models. Each elbow size has been analyzed for various bend angles (e.g., 15, 30,…90 deg and above). The results of this study show that the values of B2 and C2 based on the ASME Code formulas are conservative and more so if the bend angle is less than 90 deg. The values of B2 and C2 decrease as the bend angle is decreased. The reduction in the values is very significant for smaller bend angles. Simple relations have been established to express the dependence of B2 and C2 on the bend angle. Based on these results, a modified form of ASME Code formulas is proposed to account for the bend angle effect.
Mixing Models for Large-Eddy Simulation of Nonpremixed Turbulent Combustion
Authors: deBruynKops S. M. , Riley J. J.
Published: July 2002

The application of mixture fraction based models to large-eddy simulations (LES) of nonpremixed turbulent combustion requires information about mixing at length scales not resolved on the LES grid. For instance, the large-eddy laminar flamelet model (LELFM) takes the subgrid-scale variance and the filtered dissipation rate of the mixture fraction as inputs. Since chemical reaction rates in nonpremixed turbulence are largely governed by the mixing rate, accurate mixing models are required if mixture fraction methods are to be successfully used to predict species concentrations in large-eddy simulations. In this paper, several models for the SGS scalar variance and the filtered scalar dissipation rate are systematically evaluated a priori using benchmark data from a DNS in homogeneous, isotropic, isothermal turbulence. The mixing models are also evaluated a posteriori by applying them to actual LES data of the same flow. Predictions from the models that depend on an assumed form for the scalar energy spectrum are very good for the flow considered, and are better than those from models that rely on other assumptions.
Effect of Partition Wall on Natural Convection Heat Transfer in a Vertical Air Layer
Authors: Yamaguchi Yoshiyuki , Asako Yutaka
Published: July 2002

Three-dimensional natural convection heat transfer characteristics in a vertical air layer partitioned into cubical enclosures by partition walls of finite thermal conductivity and finite thickness were obtained numerically. The air layer is differentially heated from each surface. In this work, the analyses were performed using finite thickness and finite conductivity of the partition wall for Ra=104 and 105, and for wide range of the thickness and the conductivity of the partition wall. The results were presented in the form of overall convection and total heat transfer coefficient. From the comparison of the results with the traditional ideal boundary conditions such as “conduction,” “adiabatic,” and “no-thickness,” the correlation of the heat transfer with the actual partition wall and the ideal boundary conditions were developed. After examinations of the results, it was shown that the proportion of the heat transfer quantity in the partition wall to the total heat transfer quantity from the hot wall is a function of a product of the thermal conductivity and the thickness of the partition wall.
Assessment of Overall Cooling Performance in Thermal Design of Electronics Based on Thermodynamics
Authors: Ogiso Ken
Published: July 2002

A method of assessing the overall cooling performance in the thermal design of electronics is presented. The method is based on the optimization concept proposed by A. Bejan, whose original idea was related to the trade-off between heat transfer enhancement and pressure loss increase based on an assessment of entropy generation rate. The present report summarizes the research conducted to date and presents a study on the optimization of cooling systems.
First Experiments on an Evaporative Gas Turbine Pilot Power Plant: Water Circuit Chemistry and Humidification Evaluation
Authors: A˚gren N. D. , Westermark M. O. , Bartlett M. A. , Lindquist T.
Published: July 2002

The evaporative gas turbine (EvGT), also known as the humid air turbine (HAT) cycle, is a novel advanced gas turbine cycle that has attracted considerable interest for the last decade. This high-efficiency cycle shows the potential to be competitive with Diesel engines or combined cycles in small and intermediate scale plants for power production and/or cogeneration. A 0.6 MW natural gas-fired EvGT pilot plant has been constructed by a Swedish national research group in cooperation between universities and industry. The plant is located at the Lund Institute of Technology, Lund, Sweden. The pilot plant uses a humidification tower with metallic packing in which heated water from the flue gas economizer is brought into direct counter current contact with the pressurized air from the compressor. This gives an efficient heat recovery and thereby a thermodynamically sound cycle. As the hot sections in high-temperature gas turbines are sensitive to particles and alkali compounds, water quality issues need to be carefully considered. As such, apart from evaluating the thermodynamic and part-load performance characteristics of the plant, and verifying the operation of the high-pressure humidifier, much attention is focused on the water chemistry issues associated with the recovery and reuse of condensate water from the flue gas. A water treatment system has been designed and integrated into the pilot plant. This paper presents the first water quality results from the plant. The experimental results show that the condensate contains low levels of alkali and calcium, around 2 mg/l Σ(K,Na,Ca), probably originating from the unfiltered compressor intake. About 14 mg/l NO2−+NO3− comes from condensate absorption of flue gas NOx. Some Cu is noted, 16 mg/l, which originates from copper corrosion of the condenser tubes. After CO2 stripping, condensate filtration and a mixed bed ion exchanger, the condensate is of suitable quality for reuse as humidification water. The need for large quantities of demineralized water has by many authors been identified as a drawback for the evaporative cycle. However, by cooling the humid flue gas, the recovery of condensed water cuts the need of water feed. A self-supporting water circuit can be achieved, with no need for any net addition of water to the system. In the pilot plant, this was achieved by cooling the flue gas to around 35°C.
Large-Scale Hull Loading of Sea Ice, Lake Ice, and Ice in Tuktoyaktuk Harbour
Authors: Gagnon R. E. , Jones S. J. , Frederking R. , Spencer P. A. , Masterson D. M.
Published: July 2002

As part of an INSROP project, large-scale hull loading of first-year sea ice, two series of experiments were carried out to simulate ice loading on a ship’s hull. The first, Phase I, was a preliminary series on freshwater lake ice near Calgary, Alberta, and the second, Phase II, took place in Tuktoyaktuk Harbour in the Canadian Arctic also on essentially freshwater ice. Loading was generated by hydraulic actuators impressing a rigid indentor against an ice edge, and by using flatjacks. A finite element analysis of the test geometry was carried out to assess the deformation and stress distributions in the ice edge for cases with both undamaged and varying degrees of damage. The calculated and measured stiffness of the ice edge agreed for a realistic selection of elastic modulus of the parent ice and damaged ice. The field results did not show conclusively any influence of damage on the failure strength of the ice. A review of these results, and those from Resolute Bay sea ice obtained earlier, showed that the nature of the ice loading, depending on whether it was uniform pressure or uniform deformation, significantly affected the results. The failure stress for uniform pressure tests did not have any dependence on area or aspect ratio. The measured field results gave average ice pressures less than those recommended by the Arctic Pollution Prevention Regulations.
Gas Turbine Field Performance Determination: Sources of Uncertainties
Authors: Pinelli M. , Spina P. R.
Published: July 2002

This paper presents an analysis of the uncertainties in the determination of gas turbine health, which arise by using a method of gas path analysis. This method uses field measurements to estimate, through a mathematical model of the gas turbine thermodynamic cycle, the characteristic geometric and performance parameters, which are indices of gas turbine health. The investigated sources of uncertainties are the influence of measurement accuracy and the a priori selection of the characteristic parameters that have to be considered constant during the calculation. This fact implies that variations occurring on these parameters in the actual gas turbine cause an estimation error on the characteristic parameters used as problem variables. The analysis leads to the selection of the appropriate measurements to be used in the gas turbine health determination and to the identification of both the most critical measurements and parameters.
CFD Predictions and Field Measurements of NOx
Emissions From LM1600 Gas Turbine During Part Load Operation
Authors: Price G. R. , Botros K. K. , Goldin G. M.
Published: July 2002

CFD simulations of the combustion process and formation of emissions in an industrial GE LM1600 gas turbine have been performed over a range of unit loads. Two combustion models were considered here to characterize the combustion process, the chemical equilibrium model and the nonequilibrium laminar flamelet model. The flamelet model predictions of nitric oxide concentration demonstrated much closer agreement with field measurements of continuous emission monitoring systems, due to accurate modeling of the oxygen radial concentration. The predictions made with this model are within 15 percent at maximum load and considerably better at lower loads. Field measurements also showed that nitric oxide constitutes about 95 percent of the total NOx measured. Unburnt hydrocarbons and carbon monoxide emissions are significantly overpredicted, however, arguably as a result of neglecting their oxidation in the high temperature, fuel-lean environment of the turbine and exhaust stack downstream of the combustor.
Damage Zone Around Tip of an Interface Crack Between Rubber-Modified
Epoxy Resin and Aluminum
Authors: Lee Deok-Bo , Ikeda Toru , Miyazaki Noriyuki , Choi Nak-Sam
Published: July 2002

The fracture behavior of an interface crack tip has significant influence on the structural integrity of an adhesive joint. We investigate a damage zone and the deformation of rubber particles around a tip of an interface crack between rubber-modified epoxy resin and aluminum. They are compared with those around a crack tip in homogeneous rubber-modified epoxy resin. Cavitations in rubber particles are observed around a damaged crack tip in homogeneous resin but not around a damaged interface crack tip. Rubber particles around an interface crack tip are deformed ellipsoidally due to the residual stress even before being damaged, and interfaces between rubber particles and epoxy resin around an interface crack tip are debonded after being damaged.
Robust Feedback Control of a Baffled Plate via Open-Loop Optimization
Authors: De Man P. , Franc¸ois A. , Preumont A.
Published: July 2002

A SISO control system is built by using a volume displacement sensor and a set of actuators driven in parallel with a single amplifier. The actuators location is optimized to achieve an open-loop transfer function which exhibits alternating poles and zeros, as for systems with collocated actuators and sensors; the search procedure uses a genetic algorithm. The ability of a simple lead compensator to control this SISO system is numerically demonstrated.
Analysis of the Heat Transfer Mechanism in High-Temperature
Circulating Fluidized Beds by a Numerical Model
Authors: He Qiao , Winter Franz , Lu Ji-Dong
Published: July 2002

A general numerical model is presented here to describe the complex fluid dynamics and the heat transfer process in high-temperature circulating fluidized beds (CFBs). The core-wall concept is used to describe the gas-solid flow in the dilute phase section of CFBs. The variation of the thickness of the wall layer along the height direction is considered in the fluid dynamic model in order to approach the practical conditions. Three components of heat transfer, i.e., the particle-convective heat transfer, the gas-convective heat transfer, and the radiative heat transfer, and their contributions to the total heat transfer coefficient are investigated. The influences of some operating parameters on the total heat transfer and its components are predicted. Detailed information about the mechanism of heat transfer is discussed. The radiative heat transfer accounts for about 30∼60% of the total heat transfer in high temperature CFBs. It gradually increases along the height direction of the furnace. When the contribution of particle convection increases, the contribution of gas convection decreases, and vice versa. Particle size shows a significant effect on the radiative heat transfer and the convective heat transfer. High bed and wall temperatures will primarily increase the radiative heat transfer.
A Recuperated Gas Turbine Incorporating External Heat Sources in the
Combined Gas-Steam Cycle
Authors: Chodkiewicz R. , Krysinski J. , Porochnicki J.
Published: July 2002

The recuperation by means of external waste heat sources, as opposed to the recuperation of the turbine exhaust gases (to preheat the compressed air), allows one to utilize the hot exhaust gases of the gas turbine in the bottoming steam cycle to produce steam in order to generate additional power. Such a combined gas/steam energy system, closely integrated with the industrial process, can produce electric power (and useful heat) with high efficiency and very low atmospheric air pollution. In the present paper two examples of applications of this new technology have been analyzed from the economic and ecological viewpoint.
Thermal Field and Flow Visualization Within the Stagnation Region of
a Film-Cooled Turbine Vane
Authors: Cutbirth J. Michael , Bogard David G.
Published: July 2002

To develop quality computational codes for the film cooling of a turbine vane, a detailed understanding is needed of the physical mechanisms of the mainstream-coolant interactions. In this study flow visualization, thermal profiles, and laser Doppler velocimetry measurements were used to define the thermal and velocity fields of the film cooled showerhead region of a turbine vane. The showerhead consisted of six rows of spanwise oriented coolant holes, and blowing ratios ranged from 0.5 to 2.0. Performances with low and high mainstream turbulence levels were tested. Coolant jets from the showerhead were completely separated from the surface even at relatively low blowing ratios. However, the interaction of the coolant jets from laterally adjacent holes created a barrier to the mainstream flow, resulting in relatively high adiabatic effectiveness.
Numerical Study of Rotating Stall in a Pump Vaned Diffuser
Authors: Sano Takeshi , Yoshida Yoshiki , Tsujimoto Yoshinobu , Nakamura Yuki , Matsushima Tatsuhito
Published: July 2002

This paper treats the flow instabilities in a vaned diffuser by using CFD. A commercial code with the standard κ-ε turbulence model was used for the present work. It was found that the flow instabilities in the vaned diffuser: i.e., rotating stall, alternate blade stall, and asymmetric stall, could be simulated by the present calculations. These instabilities were observed in a range with negative slope of the pressure performance curve of the diffuser. The rotating stall onset flow rate is larger for the case with larger clearance between the impeller and diffuser vanes.
Beam Characterization and Improvement with a Flux Mapping System for Dish Concentrators
Authors: Ulmer Steffen , Reinalter Wolfgang , Heller Peter , Lu¨pfert Eckhard , Martı´nez Diego
Published: July 2002

A flux mapping system able to measure the flux distribution of dish/Stirling systems in planes perpendicular to the optical axis was built and operated at the Plataforma Solar de Almerı´a (PSA). It uses the indirect measuring method with a water-cooled Lambertian target placed in the beam path and a CCD-camera mounted on the concentrator taking images of the brightness distribution of the focal spot. The calibration is made by calculating the total power coming from the dish and relating it to the integrated gray value over the whole measurement area. The system was successfully operated in a DISTAL II stretched membrane dish and in the new EURODISH in order to characterize their beams and improve the flux distribution on their receivers.
Measurement of Distribution of Maximum Index-Fingertip Force in all Directions at Fingertip in Flexion/Extension Plane
Authors: Yokogawa Ryuichi , Hara Kei
Published: July 2002

The purpose of the present study is to investigate whether distribution patterns of the maximum fingertip force in all directions from 0 deg to 360 deg around the index fingertip are the same among subjects. Distributions of the maximum index fingertip force were measured at four finger postures for five subjects (healthy males, ages 21 to 25). It became apparent that distribution patterns of the fingertip force were very similar among subjects, through the application of an analysis of variance (level of significance: 5%) to the measurement results. In the production of the maximum fingertip force, Valero-Cuevas et al. [1998, 2000] reported that patterns of control signals for driving muscle forces were common among subjects. The results of the present study indicate that patterns of maximum fingertip force are also similar among subjects. Therefore, the possibility is high that the static transfer characteristic for index fingers from input (i.e., control signals to muscles) to output (i.e., the maximum fingertip force) is also common among subjects.
Experimental Investigation of Convective Melting of Granular Packed
Bed Under Microgravity
Authors: Jiang J. , Hao Y. , Tao Y.-X.
Published: July 2002

To improve the understanding of convective melting of packed solid particles in a fluid, an experimental investigation is conducted to study the melting characteristics of a packed bed by unmasking the buoyancy forces due to the density difference between the melt and solid particles. A close-loop apparatus, named the particle-melting-in-flow (PMF) module, is designed to allow a steady-state liquid flow at a specified temperature. The module is installed onboard NASA’s KC-135 reduced gravity aircraft using ice particles of desired sizes and water as the test media. Experimentally determined melting rates are presented as a function of upstream flow velocity, temperature and initial average particle size of the packed bed. It is found that the melting rate is influenced mainly by the ratio of the Reynolds number (Re, based on the initial particle diameter) to the square of the Froude number (Fr), and the Stefan number (Ste). In general, the dimensionless melting rate decreases as Re/Fr2 increases and increases as Ste increases. With the absence of gravity, i.e., as the Froude number approaches infinity, a maximum melting rate can be achieved. The increase in the melting rate proportional to the Stefan number also becomes more pronounced under the zero gravity condition. The trend of average and local Nusselt number of the melting packed bed under microgravity, as a function of Reynolds number and Prandtl number, is discussed and compared with the case of nonmelting packed bed.
Torsion/Simple Shear of Single Crystal Copper
Authors: Horstemeyer M. F. , Lim J. , Lu W. Y. , Mosher D. A. , Baskes M. I. , Prantil V. C. , Plimpton S. J.
Published: July 2002

We analyze simple shear and torsion of single crystal copper by employing experiments, molecular dynamics simulations, and finite element simulations in order to focus on the kinematic responses and the apparent yield strengths at different length scales of the specimens. In order to compare torsion with simple shear, the specimens were designed to be of similar size. To accomplish this, the ratio of the cylinder circumference to the axial gage length in torsion equaled the ratio of the length to height of the simple shear specimens (0.43). With the [110] crystallographic direction parallel to the rotational axis of the specimen, we observed a deformation wave of material that oscillated around the specimen in torsion and through the length of the specimen in simple shear. In torsion, the ratio of the wave amplitude divided by cylinder circumference ranged from 0.02–0.07 for the three different methods of analysis: experiments, molecular dynamics simulations, and finite element simulations. In simple shear, the ratio of the deformation wave amplitude divided by the specimen length and the corresponding values predicted by the molecular dynamics and finite element simulations (simple shear experiments were not performed) ranged from 0.23–0.26. Although each different analysis method gave similar results for each type boundary condition, the simple shear case gave approximately five times more amplitude than torsion. We attributed this observation to the plastic spin behaving differently as the simple shear case constrained the dislocation activity to planar double slip, but the torsion specimen experienced quadruple slip. The finite element simulations showed a clear relation with the plastic spin and the oscillation of the material wave. As for the yield stress in simple shear, a size scale dependence was found regarding two different size atomistic simulations for copper (332 atoms and 23628 atoms). We extrapolated the atomistic yield stresses to the order of a centimeter, and these comparisons were close to experimental data in the literature and the present study.
Foreword
Authors: Mohan Raj , Raj Rishi
Published: July 2002

[S0094-4289(00)02103-4]
Analysis on the Performance of a Thermoelectric Generator
Authors: Chen Jincan , Wu Chih
Published: July 2002

An externally and internally irreversible heat engine model of thermoelectric generators is used to analyze the so-called device-design parameter introduced by O¨zkaynak et al. The simple expression of the parameter is given and its physical meaning is expounded. Moreover, the optimal range of the parameter is determined and the problems relative to the maximum power output and maximum efficiency are discussed. Some meaningful results are obtained. [S0195-0738(00)00401-5]
Average Boiling and Condensation Heat Transfer Coefficients of the
Zeotropic Refrigerant Mixture R22/R142b in a Coaxial Tube-in-Tube Heat Exchanger
Authors: Meyer J. P. , Bukasa J. M. , Kebonte S. A.
Published: July 2002

Average boiling and condensation heat transfer coefficients were determined experimentally for a coaxial tube-in-tube heat exchanger used in hot water heat pumps. During manufacturing, the heat exchanger geometry used for the experiments changed from round tubes to elliptical tubes as no spacers were used to keep the inner tube from touching the outer tube. The refrigerant used was two different mixtures of R22 with R142b in mass ratios of 80 percent/20 percent and 60 percent/40 percent. The results were compared to theoretical results for straight tubes. It was concluded that the theoretical modes do not predict the heat transfer coefficients very well in coaxial tube-in-tube heat exchangers where the annulus touches the inside of the outer tube. [S0022-1481(00)01001-X]
Issues and Challenges in the Requalification of Offshore Platforms in
Mexico
Authors: Valdés Victor M. , Ortega Ramirez Roberto
Published: July 2002

[S0892-7219(00)00201-6]
Hydrodynamic Coefficient Estimation for TLP and Spar Structures
Authors: Lake Matthew , He Haiping , Troesch Armin W. , Perlin Marc , Thiagarajan Krish P.
Published: July 2002

Research papers at previous OMAE conferences by Thiagarajan and Troesch 45 described forced oscillation model tests using a 0.45-m-dia cylinder and a 0.6-m-disk appended to the cylinder base for drag augmentation. Scaling laws were proposed based on a component scaling concept for extrapolation of full-scale added mass and damping coefficients. The present work further verifies the scaling methodology by presenting and discussing results on smaller models—cylinder and disk of diameters 0.15 m and 0.19 m, respectively. The dimensions of the smaller models are typical of more complex offshore platform models tested in scale 1:50 to 1:75 design sea states. The hydrodynamic coefficients of the cylinder and of the disk are estimated individually, and component-scaling methodology is examined. Physics-based arguments for the differences in force coefficients of the configurations are discussed: flow around the cylinder, flow around the disk, and flow around the composite structure. The analysis results from force measurements and flow visualization conducted during forced oscillation experiments. Further, difficulties in maintaining accuracy with the smaller models are examined. [S0892-7219(00)00202-8]
Wear Measurements of Diamond-Like Carbon Coated Proximity Recording Sliders Using Raman Spectroscopy
Authors: Kohira Hidekazu , Talke F. E.
Published: July 2002

The wear behavior of diamond-like carbon (DLC) coated sliders for proximity recording is investigated as a function of sliding distance, spindle speed and slider “interference height” using Raman spectroscopy. Both constant speed drag tests simulating track following and “slew” tests simulating track seeking were performed. The results indicate that track seeking increases the wear rate of DLC coated sliders dramatically during the first stages of a seek test. The results also show that wear of the DLC layer depends strongly on sliding distance and interference height of the slider. [S0742-4787(00)03801-7]
Relationship Between Vibration Frequencies of Reddy and Kirchhoff Polygonal Plates With Simply Supported Edges
Authors: Wang C. M. , Kitipornchai S. , Reddy J. N.
Published: July 2002

This paper presents an exact relationship between the natural frequencies of Reddy third-order plate theory and those of classical Kirchhoff plate theory for simply supported, polygonal isotropic plates, including rectangular plates. The relationship for the natural frequencies enables one to obtain the solutions of the third-order plate theory from the known Kirchhoff plate theory for the same problem. As examples, some vibration frequencies for rectangular and regular polygonal plates are determined using this relationship. [S0739-3717(00)01601-9]
Polycarbonate Spin Cast Films by XPS
Authors: Burrell Michael C. , Chera John J.
Published: July 2002

A spin cast film of poly(bisphenol-A carbonate) was analyzed by XPS using monochromatic Al Kα excitation. The measured atomic composition closely matched the expected stoichiometry of the polymer. Peak positions of the individual chemically shifted C 1s and O 1s components are reported. The results are in general agreement with other reported spectra of polycarbonate polymers: experimental, C 83.4% and O 16.6%; theoretical, C 84.2% and O 15.8%.