bluuebunny/crossref_metadata_2025 huggingface dataset:
Methodological issues ‐ Reflections on quantification in corporate social reporting content analysis
Authors: Unerman Jeffrey
Published: July 2002

A key assumption underlying many corporate social reporting content analysis studies is that volume of disclosure signifies the relative importance of disclosures. Most of these studies have only quantified disclosures in annual reports, and there is disagreement within the literature regarding the best way to measure each individual disclosure. Based on observations made during the conduct of a 100‐year content analysis study, which examined a broad range of Shell’s corporate reports, this paper argues that an exclusive focus on annual reports is likely to result in an incomplete picture of reporting practices. It also contributes further insights to the debate on measurement techniques, arguing that while measurement in sentences may be carried out with greater accuracy than measurement in proportions of a page, the former is likely to give less relevant results than the latter.
Exploring causes of principal burnout
Authors: Whitaker Kathryn S.
Published: July 2002

Describes a qualitative study on causes of principal burnout. Aims to ascertain causes of emotional exhaustion, depersonalization, and personal accomplishment in the principalship. Nine principals depict how the principalship has changed and describe elements of their jobs that lead to burnout, as well as reasons for not wanting to continue in the principalship despite intrinsic rewards associated with the job. Discusses several implications including the need for more support systems, greater professional development opportunities, and the need to prepare principals better for the realities of the job.
Response to the QAA consultation paper on the quality assurance and standards framework for UK higher education
Authors: Greensted Christopher , Slack Jonathan
Published: July 2002

Following the fundamental review by the Committee of Inquiry into Higher Education, under the Chairmanship of Sir Ron, (now Lord) Dearing, in July, 1997 (and Scottish equivalent under Sir Ron Garrick); the Quality Assurance Agency for higher education (QAA), is currently consulting on the detailed elaboration of those Committees’ main recommendations. The QAA proposals are designed to provide public assurance on both the quality and standards in higher education and comprise an inter‐related set of components under the following headings: the development of a complete and overarching framework of qualifications for the UK; the development of a national template for individual programme specifications; the development of benchmarking information and threshold standards across 41 subject areas; the development of institutional codes of practice and institutional reviews; and the strengthening of the existing external examiner system to encompass a formal role of feedback on quality and standards to the QAA. The paper was submitted by the Association of Business schools to the QAA, in the format specified by the QAA. It can therefore best be understood in conjunction with the QAA’s consultation paper “An agenda for quality”, which provides greater detail of the main components, set out above.
Factors influencing the types of products and services purchased over the Internet
Authors: Phau Ian , Meng Poon Sui
Published: July 2002

Presents the findings of an empirical investigation of Internet shopping in Singapore. Specifically, Internet buying behaviour is compared between potential Internet buyers and non‐Internet buyers. It was found that the classification of different types of products and services will significantly influence the consumer choice between a retail store and Internet shopping mall. The types of products and services that are suitable for selling through the Internet are also identified. Generally, products and services that have a low outlay, are frequently purchased, have intangible value proposition, and relatively high on differentiation are more likely to be purchased via the Internet. Based on the analysis and results obtained from the study, some recommendations are presented to retailers who are interested in selling their products via the Internet.
Facing life without the Internet
Authors: Kingsley Paul , Anderson Terry
Published: July 2002

The size of that section of the electronic market place known as the Internet is substantially dependent on how many people acquire and retain Internet access. This core of Internet users is the bedrock on which electronic commerce will be built. More attention has been given to the reasons why people join the Internet community than to their motivation for leaving. We therefore sought to carry out exploratory research into the thinking of some of the likely Internet defectors in order to identify intelligent questions which could form the basis for subsequent experimental hypotheses. At the same time we took the opportunity to examine possible critical mass effects in the adoption of the Internet as a piece of innovative technology, and to shed some light on the question of knowledge gaps, more recently characterised as the problem of the information rich and the information poor.
Exploring consumer product construct systems with the repertory grid technique
Authors: Marsden David , Littler Dale
Published: July 2002

Examines some of the applications of repertory grid technique and theory to qualitative market research. In particular, it shows how together they can be used to explore five basic components of the network of subjective meanings that consumers attach to their consumption experiences, what are termed here consumers’ product construct systems (PCSs): consumption domains: how do consumers categorise different products and services?; decision rules: what search strategies and evaluative criteria are employed for each category?; values: what core beliefs underpin different decision rules?; construct complexity: how discriminating are consumer’s decision rules and values?; and construct commonalities: what are the similarities and differences in consumers’ PCSs and how are they mediated by their demographic backgrounds?
Adaptive slicing with sloping layer surfaces
Authors: Hope R.L. , Roth R.N. , Jacobs P.A.
Published: July 2002

Presents an adaptive slicing procedure for improving the geometric accuracy of layered manufacturing techniques which, unlike previous procedures, uses layers with sloping boundary surfaces that closely match the shape of the required surface. This greatly reduces the stair case effect which is characteristic of layered components with square edges. Considers two measures of error, and outlines a method of predicting these measures for sloping layer surfaces. To cater for different manufacturing requirements, presents a method to produce parts with either an inside or outside tolerance, or a combination of both. Finally, considers some problems associated with surface joins, vertices, and inflection points and proposes some solutions.
Characterization of the N‐terminal repeat domain of Escherichia coli ClpA—A class I Clp/HSP100 ATPase
Authors: Lo John H. , Baker Tania A. , Sauer Robert T.
Published: July 2002

The ClpA, ClpB, and ClpC subfamilies of the Clp/HSP100 ATPases contain a conserved N‐terminal region of ∼150 residues that consists of two approximate sequence repeats. This sequence from the Escherichia coli ClpA enzyme is shown to encode an independent structural domain (the R domain) that is monomeric and ∼40% α‐helical. A ClpA fragment lacking the R domain showed ATP‐dependent oligomerization, protein‐stimulated ATPase activity, and the ability to complex with the ClpP peptidase and mediate degradation of peptide and protein substrates, including casein and ssrA‐tagged proteins. Compared with the activities of the wild‐type ClpA, however, those of the ClpA fragment missing the R domain were reduced. These results indicate that the R domain is not required for the basic recognition, unfolding, and translocation functions that allow ClpA‐ClpP to degrade some protein substrates, but they suggest that it may play a role in modulating these activities.
Development of a cytokine analog with enhanced stability using computational ultrahigh throughput screening
Authors: Luo Peizhi , Hayes Robert J. , Chan Cheryl , Stark Diane M. , Hwang Marian Y. , Jacinto Jonathan M. , Juvvadi Padmaja , Chung Helen S. , Kundu Anirban , Ary Marie L. , Dahiyat Bassil I.
Published: July 2002

Granulocyte‐colony stimulating factor (G‐CSF) is used worldwide to prevent neutropenia caused by high‐dose chemotherapy. It has limited stability, strict formulation and storage requirements, and because of poor oral absorption must be administered by injection (typically daily). Thus, there is significant interest in developing analogs with improved pharmacological properties. We used our ultrahigh throughput computational screening method to improve the physicochemical characteristics of G‐CSF. Improving these properties can make a molecule more robust, enhance its shelf life, or make it more amenable to alternate delivery systems and formulations. It can also affect clinically important features such as pharmacokinetics. Residues in the buried core were selected for optimization to minimize changes to the surface, thereby maintaining the active site and limiting the designed protein's potential for antigenicity. Using a structure that was homology modeled from bovine G‐CSF, core designs of 25–34 residues were completed, corresponding to 1021–1028 sequences screened. The optimal sequence from each design was selected for biophysical characterization and experimental testing; each had 10–14 mutations. The designed proteins showed enhanced thermal stabilities of up to 13°C, displayed five‐to 10‐fold improvements in shelf life, and were biologically active in cell proliferation assays and in a neutropenic mouse model. Pharmacokinetic studies in monkeys showed that subcutaneous injection of the designed analogs results in greater systemic exposure, probably attributable to improved absorption from the subcutaneous compartment. These results show that our computational method can be used to develop improved pharmaceuticals and illustrate its utility as a powerful protein design tool.
Laminar processing of stimulus orientation in cat visual cortex
Authors: Martinez Luis M. , Alonso José‐Manuel , Reid R. Clay , Hirsch Judith A.
Published: July 2002

One of the most salient features to emerge in visual cortex is sensitivity to stimulus orientation. Here we asked if orientation selectivity, once established, is altered by successive stages of cortical processing. We measured patterns of orientation selectivity at all depths of the cat's visual cortex by making whole‐cell recordings with dye‐filled electrodes. Our results show that the synaptic representation of orientation indeed changes with position in the microcircuit, as information passes from layer 4 to layer 2+3 to layer 5. At the earliest cortical stage, for simple cells in layer 4, orientation tuning curves for excitation (depolarization) and inhibition (hyperpolarization) had similar peaks (within 0–7 deg, n= 11) and bandwidths. Further, the sharpness of orientation selectivity covaried with receptive field geometry (r= 0.74) ‐ the more elongated the strongest subregion, the shaper the tuning. Tuning curves for complex cells in layer 2+3 also had similar peaks (within 0–4 deg, n= 7) and bandwidths. By contrast, at a later station, layer 5, the preferred orientation for excitation and inhibition diverged such that the peaks of the tuning curves could be as far as 90 deg apart (average separation, 54 deg; n= 6). Our results support the growing consensus that orientation selectivity is generated at the earliest cortical level and structured similarly for excitation and inhibition. Moreover, our novel finding that the relative tuning of excitation and inhibition changes with laminar position helps resolve prior controversy about orientation selectivity at later phases of processing and gives a mechanistic view of how the cortical circuitry recodes orientation.
A System for Quantifying the Cooling Effectiveness of Bicycle Helmets
Authors: Reid Jennifer , Wang Eric L.
Published: July 2002

This article describes the design and development of a system that is capable of quantifying the thermal comfort of bicycle helmets. The motivation for the development of the system stems from the desire both to increase helmet use and to provide the designer with a quantitative method of evaluating the thermal comfort of a helmet. The system consists of a heated mannequin head form, a heated reference sphere, a small wind tunnel, and a data acquisition system. Both the head form and the reference sphere were instrumented with thermocouples. The system is capable of simulating riding speeds ranging from 4.5–15.5 m/s. A cooling effectiveness, C1, that is independent of both ambient conditions and wind velocity is defined as a measure of how well the helmet ventilates as compared to the reference sphere. The system was validated by testing six commercially available bicycle helmets manufactured between approximately 1992 and 1998. [S0148-0731(00)02304-9]
Flow and Heat Transfer Correlations for Porous Fin in a Plate-Fin Heat Exchanger
Authors: Kim S. Y. , Paek J. W. , Kang B. H.
Published: July 2002

The present experimental study investigates the impact of porous fins on the pressure drop and heat transfer characteristics in plate-fin heat exchangers. Systematic experiments have been carried out in a simplified model of a plate-porous fin heat exchanger at a controlled test environment. The porous fins are made of 6101 aluminum-alloy foam materials with different permeabilities and porosities. Comparison of performance between the porous fins and the conventional louvered fins has been made. The experimental results indicate that friction and heat transfer rate are significantly affected by permeability as well as porosity of the porous fin. The porous fins used in the present study show similar thermal performance to the conventional louvered fin. However, the louvered fin shows a little better performance in terms of pressure drop. For compactness of the heat exchanger, the porous fins with high pore density and low porosity are preferable. Useful correlations for the friction factor and the modified j-factor are also given for the design of a plate-porous fin heat exchanger. [S0022-1481(00)01103-8]
Formaldehyde Formation in Large Bore Natural Gas Engines Part 1: Formation Mechanisms
Authors: Mitchell Charles E. , Olsen Daniel B.
Published: July 2002

Recent testing of exhaust emissions from large bore natural gas engines has indicated that formaldehyde CH2O is present in amounts that are significant relative to hazardous air pollutant standards. In consequence, a detailed literature review has been carried out at Colorado State University to assess the current state of knowledge about formaldehyde formation mechanisms and evaluate its applicability to gas engines. In this paper the following topics from that review, which bear directly on formaldehyde formation in natural gas engines, are discussed: (1) post combustion equilibrium concentrations; (2) chemical kinetics; (3) flame propagation and structure; (4) partial oxidation possibilities; and (5) potential paths for engine out formaldehyde. Relevant data taken from the literature on equilibrium concentrations and in-flame temperatures and concentrations are presented in graphical form. A map of possible paths for engine out formaldehyde is used to summarize results of the review, and conclusions relative to formation and destruction mechanisms are presented. [S0742-4795(00)00904-2]
Component-Mode-Based Reduced Order Modeling Techniques for Mistuned Bladed Disks—Part II: Application
Authors: Bladh R. , Castanier M. P. , Pierre C.
Published: July 2002

In this paper, the component-mode-based methods formulated in the companion paper (Part I: Theoretical Models) are applied to the dynamic analysis of two example finite element models of bladed disks. Free and forced responses for both tuned and mistuned rotors are considered. Comprehensive comparisons are made among the techniques using full system finite element solutions as a benchmark. The accurate capture of eigenfrequency veering regions is of critical importance for obtaining high-fidelity predictions of the rotor’s sensitivity to mistuning. Therefore, particular attention is devoted to this subject. It is shown that the Craig–Bampton component mode synthesis (CMS) technique is robust and yields highly reliable results. However, this is achieved at considerable computational cost due to the retained component interface degrees of freedom. It is demonstrated that this problem is alleviated by a secondary modal analysis reduction technique (SMART). In addition, a non-CMS mistuning projection method is considered. Although this method is elegant and accurate, it is seen that it lacks the versatility and efficiency of the CMS-based SMART. Overall, this work shows that significant improvements on the accuracy and efficiency of current reduced order modeling methods are possible.
Capillary Blocking in Forced Convective Condensation in Horizontal Miniature Channels
Authors: Zhang Yuwen , Faghri A. , Shafii M. B.
Published: July 2002

Forced convective condensation in miniature channels is investigated numerically. Capillary blocking that occurs due to condensation in a horizontal miniature tube and between parallel plates is simulated by using the Volume of Fluid (VOF) method. The effects of vapor inlet velocity, saturation temperature, surface tension, and diameter on effective condensation length, film thickness, and heat transfer coefficient are investigated. The film thickness and the condensation length decrease as the hydraulic diameter or the distance between parallel plates decreases. When the total mass flow rate drops, the condensation length decreases significantly.
Dynamic Measurements of Three-Dimensional Scapular Kinematics: A Validation Study
Authors: Karduna Andrew R. , McClure Phil W. , Michener Lori A. , Sennett Brian
Published: July 2002

The validation of two noninvasive methods for measuring the dynamic three-dimensional kinematics of the human scapula with a magnetic tracking device is presented. One method consists of simply fixing a sensor directly to the acromion and the other consists of mounting a sensor to an adjustable plastic jig that fits over the scapular spine and acromion. The concurrent validity of both methods was assessed separately by comparison with data collected simultaneously from an invasive approach in which pins were drilled directly into the scapula. The differences between bone and skin based measurements represents an estimation of skin motion artifact. The average motion pattern of each surface method was similar to that measured by the invasive technique, especially below 120 degrees of elevation. These results indicate that with careful consideration, both methods may offer reasonably accurate representations of scapular motion that may be used to study shoulder pathologies and help develop computational models.
A Collapse Surface for a Perforated Plate With an Equilateral Triangular Array of Penetrations
Authors: Gordon J. L. , Jones D. P. , Banas D. , Hutula D. N.
Published: July 2002

A collapse surface is developed for use in limit-load analysis of plates containing a large number of small circular penetrations arranged in an equilateral triangular array of holes with a ligament efficiency of 0.31733. The collapse surface is obtained by calculating the limit load for a unit cell model of the penetration pattern using a three-dimensional elastic-perfectly plastic [EPP] finite element analysis [FEA] computer program. The EPP response from incipient yielding to plastic collapse for the unit cell is obtained for a sufficient number of load cases to define the complete collapse surface. The collapse surface is expressed analytically by using a fourth-order function that incorporates the periodicity dictated by the triangular hole pattern. The coefficients of the fourth-order function were obtained by statistically fitting the collapse surface generated by the EPP-FEA results. The resulting collapse surface was shown to be appropriate for development of an EPP-EQS theory for perforated plates. The analytic surface agrees to within 7 percent of the actual collapse surface obtained by EPP-FEA of the unit cell representing the penetration.
Film Cooling of a Cylindrical Leading Edge With Injection Through Rows of Compound-Angle Holes
Authors: Lin Y.-L. , Shih T. I.-P.
Published: July 2002

Computations, based on the k-ω shear-stress transport (SST) turbulence model in which all conservation equations were integrated to the wall, were performed to investigate the three-dimensional flow and heat transfer about a semi-cylindrical leading edge with a flat afterbody that is cooled by film-cooling jets, injected from a plenum through three staggered rows of compound-angle holes with one row along the stagnation line and two rows along ±25 deg. Results are presented for the surface adiabatic effectiveness, normalized temperature distribution, velocity vector field, and surface pressure. These results show the interactions between the mainstream hot gas and the cooling jets, and how those interactions affect surface adiabatic effectiveness. Results also show how “hot spots” can form about the stagnation zone because of the flow induced by the cooling jets. The computed results were compared with experimental data generated under a blind test. This comparison shows the results generated to be reasonable and physically meaningful. With the SST model, the normal spreading was under predicted from 20 to 50 percent. The lateral spreading was over predicted above the surface, but under predicted on the surface. The laterally averaged surface effectiveness was well predicted.
High-Resolution Measurements of Local Effectiveness From Discrete Hole Film Cooling
Authors: Baldauf S. , Schulz A. , Wittig S.
Published: July 2002

Local adiabatic film cooling effectiveness on a flat plate surface downstream a row of cylindrical holes was investigated. Geometric parameters such as blowing angle and hole pitch, as well as the flow parameters blowing rate and density ratio, were varied in a wide range emphasizing engine relevant conditions. IR thermography was used to perform local measurements of the surface temperature field. A spatial resolution of up to seven data points per hole diameter extending to 80 hole diameters downstream of the ejection location was achieved. Since all technical wall materials have a finite thermoconductivity, a procedure for correcting the measured surface temperature data based on a Finite Element analysis was developed. Heat loss over the back and remnant heat flux within the test plate in lateral and streamwise directions were taken into account. The local effectiveness patterns obtained are systematically analyzed to quantify the influence of the various parameters. As a result, a detailed description of the characteristics of local adiabatic film cooling effectiveness is given. Furthermore, the locally resolved experimental results can serve as a data base for the validation of CFD codes predicting discrete hole film cooling.
Computational Fluid Dynamics of a Vascular Access Case for Hemodialysis
Authors: Ene-Iordache Bogdan , Mosconi Lidia , Remuzzi Giuseppe , Remuzzi Andrea
Published: July 2002

Vascular accesses (VA) for hemodialysis are usually created by native arteriovenous fistulas (AVF) or synthetic grafts. Maintaining patency of VA continues to be a major problem for patients with end-stage renal disease, since in these vessels thrombosis and intimal hyperplasia often occur. These lesions are frequently associated with disturbed flow that develops near bifurcations or sharp curvatures. We explored the possibility of investigating blood flow dynamics in a patient-specific model of end-to-end native AVF using computational fluid dynamics (CFD). Using digital subtraction angiographies of an AVF, we generated a three-dimensional meshwork for numerical analysis of blood flow. As input condition, a time-dependent blood waveform in the radial artery was derived from centerline velocity obtained during echo-color-Doppler ultrasound examination. The finite element solution was calculated using a fluid-dynamic software package. In the straight, afferent side of the radial artery wall shear stress ranged between 20 and 36 dynes/cm2, while on the inner surface of the bending zone it increased up to 350 dynes/cm2. On the venous side, proximal to the anastomosis, wall shear stress was oscillating between negative and positive values (from −12 dynes/cm2 to 112 dynes/cm2), while distal from the anastomosis, the wall shear stress returned within the physiologic range, ranging from 8 to 22 dynes/cm2. Areas of the vessel wall with very high shear stress gradient were identified on the bending zone of the radial artery and on the venous side, after the arteriovenous shunt. Secondary blood flows were also observed in these regions. CFD gave a detailed description of blood flow field and showed that this approach can be used for patient-specific analysis of blood vessels, to understand better the role of local hemodynamic conditions in the development of vascular lesions.
Experimental Investigation of Mode Localization and Forced Response Amplitude Magnification for a Mistuned Bladed Disk
Authors: Judge J. , Pierre C. , Mehmed O.
Published: July 2002

The results of an experimental investigation on the effects of random blade mistuning on the forced dynamic response of bladed disks are reported. The primary aim of the experiment is to gain understanding of the phenomena of mode localization and forced response blade amplitude magnification in bladed disks. A stationary, nominally periodic, 12-bladed disk with simple geometry is subjected to a traveling-wave out-of-plane “engine order” excitation delivered via phase-shifted control signals sent to piezoelectric actuators mounted on the blades. The bladed disk is then mistuned by the addition of small, unequal weights to the blade tips, and it is again subjected to a traveling wave excitation. The experimental data is used to verify analytical predictions about the occurrence of localized mode shapes, increases in forced response amplitude, and changes in resonant frequency due to the presence of mistuning. Very good agreement between experimental measurements and finite element analysis is obtained. The out-of-plane response is compared and contrasted with the previously reported in-plane mode localization behavior of the same test specimen. This work also represents an important extension of previous experimental study by investigating a frequency regime in which modal density is lower but disk-blade interaction is significantly greater.
Prediction of Building Integrated Photovoltaic Cell Temperatures*
Authors: Davis Mark W. , Fanney A. Hunter , Dougherty Brian P.
Published: July 2002

A barrier to the widespread application of building integrated photovoltaics (BIPV) is the lack of validated predictive performance tools. Architects and building owners need these tools in order to determine if the potential energy savings realized from building integrated photovoltaics justifies the additional capital expenditure. The National Institute of Standards and Technology (NIST) seeks to provide high quality experimental data that can be used to develop and validate these predictive performance tools. The temperature of a photovoltaic module affects its electrical output characteristics and efficiency. Traditionally, the temperature of solar cells has been characterized using the nominal operating cell temperature (NOCT), which can be used in conjunction with a calculation procedure to predict the module’s temperature for various environmental conditions. The NOCT procedure provides a representative prediction of the cell temperature, specifically for the ubiquitous rack-mounted installation. The procedure estimates the cell temperature based on the ambient temperature and the solar irradiance. It makes the approximation that the overall heat loss coefficient is constant. In other words, the temperature difference between the panel and the environment is linearly related to the heat flux on the panels (solar irradiance). The heat transfer characteristics of a rack-mounted PV module and a BIPV module can be quite different. The manner in which the module is installed within the building envelope influences the cell’s operating temperature. Unlike rack-mounted modules, the two sides of the modules may be subjected to significantly different environmental conditions. This paper presents a new technique to compute the operating temperature of cells within building integrated photovoltaic modules using a one-dimensional transient heat transfer model. The resulting predictions are compared to measured BIPV cell temperatures for two single crystalline BIPV panels (one insulated panel and one uninsulated panel). Finally, the results are compared to predictions using the NOCT technique.
Pulsatile Blood Flow Effects on Temperature Distribution and Heat Transfer in Rigid Vessels
Authors: Craciunescu Oana I. , Clegg Scott T.
Published: July 2002

The effect of blood velocity pulsations on bioheat transfer is studied. A simple model of a straight rigid blood vessel with unsteady periodic flow is considered. A numerical solution that considers the fully coupled Navier–Stokes and energy equations is used for the simulations. The influence of the pulsation rate on the temperature distribution and energy transport is studied for four typical vessel sizes: aorta, large arteries, terminal arterial branches, and arterioles. The results show that: the pulsating axial velocity produces a pulsating temperature distribution; reversal of flow occurs in the aorta and in large vessels, which produces significant time variation in the temperature profile. Change of the pulsation rate yields a change of the energy transport between the vessel wall and fluid for the large vessels. For the thermally important terminal arteries (0.04–1 mm), velocity pulsations have a small influence on temperature distribution and on the energy transport out of the vessels (8 percent for the Womersley number corresponding to a normal heart rate). Given that there is a small difference between the time-averaged unsteady heat fiux due to a pulsating blood velocity and an assumed nonpulsating blood velocity, it is reasonable to assume a nonpulsating blood velocity for the purposes of estimating bioheat transfer.
Shock Wave–Film Cooling Interactions in Transonic Flows
Authors: Ligrani P. M. , Saumweber C. , Schulz A. , Wittig S.
Published: July 2002

Interactions between shock waves and film cooling are described as they affect magnitudes of local and spanwise-averaged adiabatic film cooling effectiveness distributions. A row of three cylindrical holes is employed. Spanwise spacing of holes is 4 diameters, and inclination angle is 30 deg. Free-stream Mach numbers of 0.8 and 1.10–1.12 are used, with coolant to free-stream density ratios of 1.5–1.6. Shadowgraph images show different shock structures as the blowing ratio is changed, and as the condition employed for injection of film into the cooling holes is altered. Investigated are film plenum conditions, as well as perpendicular film injection crossflow Mach numbers of 0.15, 0.3, and 0.6. Dramatic changes to local and spanwise-averaged adiabatic film effectiveness distributions are then observed as different shock wave structures develop in the immediate vicinity of the film-cooling holes. Variations are especially evident as the data obtained with a supersonic Mach number are compared to the data obtained with a free-stream Mach number of 0.8. Local and spanwise-averaged effectiveness magnitudes are generally higher when shock waves are present when a film plenum condition (with zero crossflow Mach number) is utilized. Effectiveness values measured with a supersonic approaching free-stream and shock waves then decrease as the injection crossflow Mach number increases. Such changes are due to altered flow separation regions in film holes, different injection velocity distributions at hole exits, and alterations of static pressures at film hole exits produced by different types of shock wave events.
Thermal Modeling of Unlooped and Looped Pulsating Heat Pipes
Authors: Shafii Mohammad B. , Faghri Amir , Zhang Yuwen
Published: July 2002

Analytical models for both unlooped and looped Pulsating Heat Pipes (PHPs) with multiple liquid slugs and vapor plugs are presented in this study. The governing equations are solved using an explicit finite difference scheme to predict the behavior of vapor plugs and liquid slugs. The results show that the effect of gravity on the performance of top heat mode unlooped PHP is insignificant. The effects of diameter, charge ratio, and heating wall temperature on the performance of looped and unlooped PHPs are also investigated. The results also show that heat transfer in both looped and unlooped PHPs is due mainly to the exchange of sensible heat.
Measurement of Interstitial Convective Heat Transfer and Frictional Drag for Flow Across Metal Foams
Authors: Hwang J.-J. , Hwang G.-J. , Yeh R.-H. , Chao C.-H.
Published: July 2002

Convective heat transfer and friction drag in a duct inserted with aluminum foams have been studied experimentally. The combined effects of foam porosity (ε=0.7, 0.8, and 0.95) and flow Reynolds number (1900⩽Re⩽7800) are examined. Frictional drags for flow across the aluminum foam are measured by pressure taps, while interstitial heat transfer coefficients in the aluminum foam are determined using a transient single-blow technique with a thermal non-equilibrium two-equation model. Solid material temperature distribution is further measured for double check of the heat transfer results. To understand the frictional drag mechanisms, smoke-wire flow visualization is conducted in the aluminum-foam ducts. Results show that both the friction factor and the volumetric heat transfer coefficient increase with decreasing the foam porosity at a fixed Reynolds number. In addition, the aluminum foam of ε=0.8 has the best thermal performance under the same pumping power constraint among the three aluminum foams investigated. Finally, empirical correlations for pore Nusselt number are developed in terms of pore Reynolds number under various foam porosities.
An FEM Simulation for Guided Elastic Wave Generation and Reflection in Hollow Cylinders With Corrosion Defects
Authors: Zhu Wenhao
Published: July 2002

The generation and reflection of guided elastic waves in hollow cylinders with corrosion defects have been investigated numerically for the purpose of nondestructive evaluation (NDE) of tubular structures. A new guided wave transducer model, time-delay periodic ring arrays (TDPRAs), has been used to generate the axisymmetric guided wave modes in hollow cylinders, and this is simulated by a finite element calculation. Unidirectional guided wave emission can be achieved by arranging a TDPRA’s parameters according to the principle of constructive and destructive interference. The guided wave reflections by axisymetric and nonaxisymmetric corrosion defects are analyzed using a 2-D and a 3-D FE simulation, respectively. The reflection features as well as mode conversion under the L0,1 and L0,2 mode incidences are discussed in association with the corrosion depth, the axial and circumferential extents in hollow cylinders.
Verification of Finite Volume Computations on Steady-State Fluid Flow and Heat Transfer
Authors: Cadafalch J. , Pe´rez-Segarra C. D. , Co`nsul R. , Oliva A.
Published: July 2002

This work presents a post-processing tool for the verification of steady-state fluid flow and heat transfer finite volume computations. It is based both on the generalized Richardson extrapolation and the Grid Convergence Index GCI. The observed order of accuracy and a error band where the grid independent solution is expected to be contained are estimated. The results corresponding to the following two and three-dimensional steady-state simulations are post-processed: a flow inside a cavity with moving top wall, an axisymmetric turbulent flow through a compressor valve, a premixed methane/air laminar flat flame on a perforated burner, and the heat transfer from an isothermal cylinder enclosed by a square duct. Discussion is carried out about the certainty of the estimators obtained with the post-processing procedure. They have been shown to be useful parameters in order to assess credibility and quality to the reported numerical solutions.
Tool Path-Based Deposition Planning in Fused Deposition Processes
Authors: Han Wenbiao , Jafari Mohsen A. , Danforth Stephen C. , Safari Ahmad
Published: July 2002

The fabrication of a functional part requires very high layer quality in the Fused Deposition (FD) processes. The constant deposition flow rate currently used in FD technology cannot meet this requirement, due to the varying geometries of the layers. To achieve a high quality functional part, an overfill and underfill analysis is conducted. A deposition planning approach is proposed, which is based on a grouping and mapping algorithm. Two piezoelectric test parts have been built to demonstrate the effectiveness and feasibility of the proposed approach.
Optimized Kinematic Properties for Stevenson-Type Presses With Variable Input Speed Approach
Authors: Yan Hong-Sen , Chen Wei-Ren
Published: July 2002

Traditionally, the input speed of a Stevenson-type press is constant. Here, we propose a novel approach by varying the input speed of the crank to make the ram’s motion suitable for both deep-drawing and precision-cutting. This approach uses a servomotor as the power input. By properly designing the input speed, the output motion can pass through a desired trajectory. The input motion characteristics are planned with Bezier curves. Optimization is used to improve the output characteristics. Guidelines for defining the optimization problems are discussed. Additional dimensional synthesis is also suggested for reducing the input speed variation. Design examples are given for illustration.
Influence of Fluid Flow Regime on Performances of Non-Contacting Liquid Face Seals
Authors: Brunetie`re Noe¨l , Tournerie Bernard , Fre^ne Jean
Published: July 2002

Some non contacting mechanical face seals are running near the laminar boundary flow limit. A modification of operating conditions leads to a non laminar fluid flow in the seal interface while inertia forces remain negligible. A numerical model has been developed to determine pressure and velocity fields in the sealing dam for laminar to turbulent regime. The turbulent viscosity determination is based on the Elrod and Ng model. Evolutions of seal characteristics (opening force, friction torque, leakage rate…) and fluid film dynamic coefficients versus running conditions are presented. Numerical results show that great variations appear in the transition to turbulence.
Micro- and Sub-Micromachining of Type IIa Single Crystal Diamond Using a Ti:Sapphire Femtosecond Laser
Authors: Ramanathan Diwakar , Molian Pal A.
Published: July 2002

A 200-fs pulsed Ti:Sapphire laser was used to micromachine Type IIa single crystal diamond. The effects of pulse energy and exposure time were investigated. Both blind and through holes were generated by trepanning and percussion modes. Trenches were produced by the direct-writing mode. Scanning electron and atomic force microscopy analysis revealed that the holes are in the range 0.65–100 μm and are free from taper. In addition, there was little recast layer around the holes. The damage threshold was approximately 4 J/cm2, which is smaller than those obtained from other lasers. A two-temperature model was used to establish the electron temperatures and to predict the ablation depth per pulse. It is evident from this work that femtosecond lasers are capable of producing micron and sub-micron structures with very high precision.
On the Development of Volumetric Strain Energy Functions
Authors: Doll S. , Schweizerhof K.
Published: July 2002

To describe elastic material behavior the starting point is the isochoric-volumetric decoupling of the strain energy function. The volumetric part is the central subject of this contribution. First, some volumetric functions given in the literature are discussed with respect to physical conditions, then three new volumetric functions are developed which fulfill all imposed conditions. One proposed function which contains two material parameters in addition to the compressibility parameter is treated in detail. Some parameter fits are carried out on the basis of well-known volumetric strain energy functions and experimental data. A generalization of the proposed function permits an unlimited number of additional material parameters.  Dedicated to Professor Franz Ziegler on the occasion of his 60th birthday. [S0021-8936(00)00901-6]
System Identification of Jet Engines
Authors: Sugiyama N.
Published: July 2002

System identification plays an important role in advanced control systems for jet engines, in which controls are performed adaptively using data from the actual engine and the identified engine. An identification technique for jet engine using the Constant Gain Extended Kalman Filter (CGEKF) is described. The filter is constructed for a two-spool turbofan engine. The CGEKF filter developed here can recognize parameter change in engine components and estimate unmeasurable variables over whole flight conditions. These capabilities are useful for an advanced Full Authority Digital Electric Control (FADEC). Effects of measurement noise and bias, effects of operating point and unpredicted performance change are discussed. Some experimental results using the actual engine are shown to evaluate the effectiveness of CGEKF filter. [S0742-4795(00)00401-4]
Internal Reforming Solid Oxide Fuel Cell-Gas Turbine Combined Cycles (IRSOFC-GT): Part A—Cell Model and Cycle Thermodynamic Analysis
Authors: Massardo A. F. , Lubelli F.
Published: July 2002

The aim of this work is to investigate the performance of internal reforming solid oxide fuel cell (IRSOFC) and gas turbine (GT) combined cycles. To study complex systems involving IRSOFC a mathematical model has been developed that simulates the fuel cell steady-state operation. The model, tested with data available in literature, has been used for a complete IRSOFC parametric analysis taking into account the influence of cell operative pressure, cell and stream temperatures, fuel-oxidant flow rates and composition, etc. The analysis of IRSOFC-GT combined cycles has been carried out by using the ThermoEconomic Modular Program TEMP (Agazzani and Massardo, 1997). The code has been modified to allow IRSOFC, external reformer and flue gas condenser performance to be taken into account. Using as test case the IRSOFC-GT combined plant proposed by Harvey and Richter (1994) the capability of the modified TEMP code has been demonstrated. The thermodynamic analysis of a number of IRSOFC-GT combined cycles is presented and discussed, taking into account the influence of several technological constraints. The results are presented for both atmospheric and pressurized IRSOFC. [S0742-4795(00)00501-9]
Curing of Composites Using Internal Resistive Heating
Authors: Ramakrishnan B. , Zhu L. , Pitchumani R.
Published: July 2002

Curing of fiber-resin mixtures is often the critical and productivity controlling step in the fabrication of thermosetting-matrix composites. The long processing times (and costs) have remained the fundamental impediment to widespread commercialization of composites. Shortening the cure cycle time, while ensuring a complete and uniform cure in the product, is imperative for realizing the goal of affordable materials processing, and forms the focus of this investigation. Toward addressing the affordability challenge, this paper explores the use of conductive carbon mats embedded inside the composite as a means of providing internal volumetric resistance heating during the cure process. The supplemental heating results in temperature and cure uniformity through the cross section, as well as speeds up the cure process. In the context of application to resin transfer molding, systematic experimental and theoretical studies on various resistive heating configurations are presented. Optimum processing strategies are derived based on the cure time and microstructural product quality considerations. [S1087-1357(00)01101-1]
Heat Transfer and Flow on the First-Stage Blade Tip of a Power Generation Gas Turbine: Part 1—Experimental Results
Authors: Bunker Ronald S. , Bailey Jeremy C. , Ameri Ali A.
Published: July 2002

A combined experimental and computational study has been performed to investigate the detailed distribution of convective heat transfer coefficients on the first-stage blade tip surface for a geometry typical of large power generation turbines (>100 MW). This paper is concerned with the design and execution of the experimental portion of the study, which represents the first reported investigation to obtain nearly full surface information on heat transfer coefficients within an environment that develops an appropriate pressure distribution about an airfoil blade tip and shroud model. A stationary blade cascade experiment has been run consisting of three airfoils, the center airfoil having a variable tip gap clearance. The airfoil models the aerodynamic tip section of a high-pressure turbine blade with inlet Mach number of 0.30, exit Mach number of 0.75, pressure ratio of 1.45, exit Reynolds number based on axial chord of 2.57×106, and total turning of about 110 deg. A hue detection based liquid crystal method is used to obtain the detailed heat transfer coefficient distribution on the blade tip surface for flat, smooth tip surfaces with both sharp and rounded edges. The cascade inlet turbulence intensity level took on values of either 5 or 9 percent. The cascade also models the casing recess in the shroud surface ahead of the blade. Experimental results are shown for the pressure distribution measurements on the airfoil near the tip gap, on the blade tip surface, and on the opposite shroud surface. Tip surface heat transfer coefficient distributions are shown for sharp edge and rounded edge tip geometries at each of the inlet turbulence intensity levels. [S0889-504X(00)01902-4]
Waterjet Machining and Peening of Metals
Authors: Ramulu M. , Kunaporn S. , Arola D. , Hashish M. , Hopkins J.
Published: July 2002

An experimental study was conducted to determine the influence of high-pressure waterjet (WJ) peening and abrasive waterjet (AWJ) machining on the surface integrity and texture of metals. A combination of microstructure analysis, microhardness measurements, and profilometry were used in determining the depth of plastic deformation and surface texture that result from the material removal process. The measurement and evaluation of residual stress was conducted with X-ray diffraction. The residual stress fields resulting from treatment were analyzed to further distinguish the influence of material properties on the surface integrity. It was found that waterjet peening induces plastic deformation at the surface layer of metals as good as shot peening. The degree of plastic deformation and the state of material surface were found to be strongly dependent on the peening conditions applied. [S0094-9930(00)00801-5]