bluuebunny/crossref_metadata_2025 huggingface dataset:
Design sensitivity analysis method for multidisciplinary shape optimisation problems with linear and non‐linear responses
Authors: Chiandussi G. , Fontana R. , Urbinati F.
Published: July 2002

A method to solve shape and size optimisation problems with linear and non‐linear responses has been studied taking advantage of statistical methodologies. A nested optimisation procedure has been fixed. The global optimisation problem is decomposed in several subproblems where each non‐linear response is locally approximated with a first degree polynomial function identified by the definition and execution of an experimental plan. The approximating functions so obtained are used to evaluate the design sensitivity coefficients required by the optimisation procedure. The numerical results obtained during the optimisation process to verify exactly the value of the non‐linear responses are used to verify and to improve the approximating function accuracy. The non‐linear design sensitivity analysis method so defined has been used to solve a multidisciplinary shape optimisation problem involving a real 3D automotive structure.
Communication apprehension and perceptions of salesperson performance: a multinational perspective
Authors: Pitt Leyland F. , Berthon Pierre R. , Robson Matthew J.
Published: July 2002

While the effect of communication apprehension on a multitude of psychological and performance variables has been studied in many other disciplines, it has not been extensively examined by sales researchers. This article considers communication in the sales transaction from the perspective of communication apprehension, and investigates the role of communication apprehension as an indicator of a salesperson’s performance. Using ordinal logistic regression, an attempt is made to predict a salesperson’s performance based on the four contexts of communication apprehension, in a multicultural sample. The results show a small but significant effect of communication apprehension on the performance of salespersons, and some contexts of communication apprehension are found to be better predictors than others. The findings also indicate that the Personal Report of Communication Apprehension‐24 scale is valid and reliable when used to establish international principles.
Implementing Investors in People: a case study from the NHS
Authors: Smith Paul J.
Published: July 2002

The National Health Service (NHS) is the largest employer in the UK and has a diverse workforce with many different professional groups. This can make introducing a planned programme of change a complex and difficult task. Examines the process in the shape of Investors in People (IIP) within a public sector context. The findings come from a case study of a successful IIP project in a combined acute and community trust hospital. Drawing largely on direct experience of managing an IIP project, interview, survey and documentary evidence, the paper concludes by exploring the question of whether the IIP standard can be used as a tool for managing change and if it is sophisticated enough to reach a diverse workforce.
Training issues for the European automotive industry
Authors: Dankbaar Ben
Published: July 2002

Provides an overview of the results of an investigation carried out for the European Commission. Aims to identify themes and issues in the field of continuing training in the European automotive industry. A large number of interviews were carried out in all the major car manufacturing countries of Europe, and a series of case studies were done on training projects funded by the European Commission within the framework of the FORCE programme on continuing training. Shows that training has become a key element in a far‐reaching process of restructuring which is currently under way in the industry. Identifies major fields of interest including training for new work structures; training for co‐makership; and new methods and approaches for learning while working. Larger numbers of people are trained than ever before, especially in production. Claims an increasing use of information technology (expert systems) for training is being signalled.
EXORcist Boolean algebra and interactions between binary strings
Authors: Musès C.
Published: July 2002

Carrying on the arithmetization of Euler diagrams by George Boole, with refinements by Augustus De Morgan and others, the full‐scale incorporation of binary strings into the scheme is discussed, with emphasis on the usefulness of the operator EXOR and its consequent EXORcism of what had remained unclear. Examples and applications are given. By this powerful extension of Boolean algebra Euler/Venn diagrams of class relations can be digitally computed. Its uses to system theory and cybernetics are manifold.
Use of unconventional oils in surface coatings: blends of alkyd resins with epoxy esters
Authors: Bajpai Madhu , Seth Sunita
Published: July 2002

The alkyd resin of short oil length with low acid value was modified with novolac‐based epoxy esters, prepared by using tobacco seed oil fatty acids. The prepared blends were cured using an aliphatic amine as curing agent. The films of cured resins were applied over various panels and their film characteristics were studied. It was found that the scratch hardness and corrosion resistance increased with the increase of epoxy esters in the blend. The chemical resistance was also studied and found to be better with increasing epoxy esters in the blends.
Effects of non‐isometric pigment particles in organic coatings for corrosion protection
Authors: Kalendova Andréa
Published: July 2002

Studies the effects of non‐isometric pigments on the anticorrosion properties of coating films. The optimum concentrations for using iron mica, muscovite, and graphite have been determined. The results obtained on using the natural iron mica are compared to those obtained with a synthetic product. As binders for the coatings epoxy resin, polyurethane and alkyd resins were used. The results allow the conclusion that on the pigmentation with iron mica the protection function of top coatings against the corrosive media can be considerably increased.
Managing projects in fast track – A case of public sector organization in India
Authors: Dey Prasanta Kumar
Published: July 2002

Completing projects faster than the normal duration is always a challenge to the management of any project, as it often demands many paradigm shifts. Opportunities of globalization, competition from private sectors and multinationals force the management of public sector organizations in the Indian petroleum sector to take various aggressive strategies to maintain their profitability. Constructing infrastructure for handling petroleum products is one of them. Moreover, these projects are required to be completed in faster duration compared to normal schedules to remain competitive, to get faster return on investment, and to give longer project life. However, using conventional tools and techniques of project management, it is impossible to handle the problem of reducing the project duration from a normal period. This study proposes the use of concurrent engineering in managing projects for radically reducing project duration. The phases of the project are accomplished concurrently/simultaneously instead of in a series. The complexities that arise in managing projects are tackled through restructuring project organization, improving management commitment, strengthening project‐planning activities, ensuring project quality, managing project risk objectively and integrating project activities through management information systems. These would not only ensure completion of projects in fast track, but also improve project effectiveness in terms of quality, cost effectiveness, team building, etc. and in turn overall productivity of the project organization would improve.
Mechanisms of ultrasonic joining of textile materials
Authors: Shi Weihua , Little Trevor
Published: July 2002

Investigates the potential for building smart seams by incorporating optic fibers ultrasonically. The heating and bonding mechanisms of ultrasonic welding process in fabrics were studied. Battle dress uniform (BDU) (50/50 nylon/cotton), 100 percent cotton, 100 percent polyester and Nomex fabrics were used and were bonded ultrasonically with and without polyurethane adhesives. The effects of three important welding parameters, namely weld pressure, weld time and amplitude of vibration, on the joint strength and the temperature profile at the interface were examined. The temperature profiles for different fabrics were measured during ultrasonic welding process. The attenuation degree of signal transition properties of optic fibers incorporated was tested to determine if ultrasonic process provided a possible way of embedding optic fibers into seams and achieving sufficient joint strength while the signal transmission properties of optic fibers incorporated were not changed significantly.
Building a communitarian policy of educative accountability using a critical pragmatist epistemology
Authors: Macpherson Reynold J.S.
Published: July 2002

This paper reports a policy research project intended to clarify the accountability processes and criteria that should be used to collect data, report and improve the quality of learning, teaching and leadership in Tasmania. Its outcomes informed the design of a new three‐year school review process that seeks to integrate local governance, school planning, action research evaluation, external reviews, and systemic performance monitoring. Behind the recommended policy is a touchstone set of processes and criteria that comprise a theory of mutual and educative accountability. This theory represents an attempt to reconcile centralism with pluralism, exhibits liberal, democratic and limited forms of community government, anticipates educative forms of leadership, and values communitarian over collegial and individualistic forms of professionalism.
Space‐time spectral element methods for unsteady convection‐diffusion problems
Authors: Bar‐Yoseph Pinhas Z. , Moses Eduard
Published: July 2002

Deals with the formulation and application of temporal and spatial spectral element approximations for the solution of convection‐diffusion problems. Proposes a new high‐order splitting space‐time spectral element method which exploits space‐time discontinuous Galerkin for the first hyperbolic substep and space continuous‐time discontinuous Galerkin for the second parabolic substep. Analyses this method and presents its characteristics in terms of accuracy and stability. Also investigates a subcycling technique, in which several hyperbolic substeps are taken for each parabolic substep; a technique which enables fast, cost‐effective time integration with little loss of accuracy. Demonstrates, by a numerical comparison with other coupled and splitting space‐time spectral element methods, that the proposed method exhibits significant improvements in accuracy, stability and computational efficiency, which suggests that this method is a potential alternative to existing schemes. Describes several areas for future research.
Internal academic quality audit in UK higher education: part II ‐ implications for a national quality assurance framework
Authors: Jackson Norman
Published: July 2002

Suggests that the expansion of academic quality audit methodologies within higher education institutions is a significant development in UK quality assurance. It reflects increasing demands for accountability and also a desire for more dynamic and efficient methods for review and evaluation. The adoption of common regulatory frameworks and centrally defined procedures and protocols; the more explicit specification of intentions and expectations; and the increased use of self‐assessment in quality review processes, have all assisted in creating an environment in which audit methodologies are more acceptable, appropriate and useful. Argues that the development of an audit capacity is essential to the notion of institutional self‐regulation. Such a capacity could form the basis for a type of national quality assurance framework different from that currently operated or proposed, in which there is a much closer articulation of internal and external audit processes.
National information infrastructure policy: a theoretical and
normative approach
Authors: Schaefer Richard J.
Published: July 2002

Relies on critical theories of technology and democratic disclosure
to construct normative communication principles for the development of
the national information infrastructure. Suggests that efforts to
privatize the information highway, which are currently underway,
undermine the network′s long‐range potential to encourage
citizen‐to‐citizen discussion of public issues.
Analysis of shell cracking in investment casting with laser stereolithography patterns
Authors: Yao W.L. , Leu Ming C.
Published: July 2002

This paper presents a numerical and experimental investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser stereolithography patterns. Considered are the cracking temperature of the ceramic shell, the buckling temperature of the web link, and the glass transition temperature of the epoxy resin. Our hypothesis is that shell cracking will occur if the ceramic rupture temperature is lower than the temperature of glass transition and the temperature of web buckling. This hypothesis is validated by a good agreement we obtained between experimental observations and numerical simulations. It is found that the shell cracking and web link buckling are strongly related to the cross‐sectional dimensions and span length of the web structure and the shell thickness, and that shell cracking can be prevented by buckling of the epoxy webbed pattern in early stages of the burnout process.
Magnetization transfer from laser‐polarized xenon to protons located in the hydrophobic cavity of the wheat nonspecific lipid transfer protein
Authors: Landon Céline , Berthault Patrick , Vovelle Françoise , Desvaux Hervé
Published: July 2002

Nonspecific lipid transfer protein from wheat is studied by liquid‐state NMR in the presence of xenon. The gas–protein interaction is indicated by the dependence of the protein proton chemical shifts on the xenon pressure and formally confirmed by the first observation of magnetization transfer from laser‐polarized xenon to the protein protons. Twenty‐six heteronuclear nOes have allowed the characterization of four interaction sites inside the wheat ns‐LTP cavity. Their locations are in agreement with the variations of the chemical shifts under xenon pressure and with solvation simulations. The richness of the information obtained by the noble gas with a nuclear polarization multiplied by ∼12,000 makes this approach based on dipolar cross‐relaxation with laser‐polarized xenon promising for probing protein hydrophobic pockets at ambient pressure.
Hypertonicity‐induced transmitter release at Drosophila neuromuscular junctions is partly mediated by integrins and cAMP/protein kinase A
Authors: Suzuki Kazuhiro , Grinnell Alan D. , Kidokoro Yoshiaki
Published: July 2002

The frequency of quantal transmitter release increases upon application of hypertonic solutions. This effect bypasses the Ca2+ triggering step, but requires the presence of key molecules involved in vesicle fusion, and hence could be a useful tool for dissecting the molecular process of vesicle fusion. We have examined the hypertonicity response at neuromuscular junctions of Drosophila embryos in Ca2+‐free saline. Relative to wild‐type, the response induced by puff application of hypertonic solution was enhanced in a mutant, dunce, in which the cAMP level is elevated, or in wild‐type embryos treated with forskolin, an activator of adenylyl cyclase, while protein kinase A (PKA) inhibitors decreased it. The response was also smaller in a mutant, DC0, which lacks the major subunit of PKA. Thus the cAMP/PKA cascade is involved in the hypertonicity response. Peptides containing the sequence Arg‐Gly‐Asp (RGD), which inhibit binding of integrins to natural ligands, reduced the response, whereas a peptide containing the non‐binding sequence Arg‐Gly‐Glu (RGE) did not. A reduced response persisted in a mutant, myospheroid, which expresses no integrins, and the response in DC0 was unaffected by RGD peptides. These data indicate that there are at lease two components in the hypertonicity response: one that is integrin mediated and involves the cAMP/PKA cascade, and another that is not integrin mediated and does not involve the cAMP/PKA cascade.
Oxygen uptake on‐kinetics in dog gastrocnemius in situ following activation of pyruvate dehydrogenase by dichloroacetate
Authors: Grassi Bruno , Hogan Michael C. , Greenhaff Paul L. , Hamann Jason J. , Kelley Kevin M. , Aschenbach William G. , Constantin‐Teodosiu Dumitru , Gladden L. Bruce
Published: July 2002

The aim of the present study was to determine whether the activation of the pyruvate dehydrogenase complex (PDC) by dichloroacetate (DCA) is associated with faster O2 uptake (V̇O2) on‐kinetics. V̇O2 on‐kinetics was determined in isolated canine gastrocnemius muscles in situ (n= 6) during the transition from rest to 4 min of electrically stimulated isometric tetanic contractions, corresponding to ∼60–70 % of peak V̇O2. Two conditions were compared: (1) control (saline infusion, C); and (2) DCA infusion (300 mg (kg body mass)−1, 45 min before contraction). Muscle blood flow (Q̇) was measured continuously in the popliteal vein; arterial and popliteal vein O2 contents were measured at rest and at 5–7 s intervals during the transition. Muscle V̇O2 was calculated as Q̇ multiplied by the arteriovenous O2 content difference. Muscle biopsies were taken before and at the end of contraction for determination of muscle metabolite concentrations. DCA activated PDC at rest, as shown by the 9‐fold higher acetylcarnitine concentration in DCA (vs. C; P < 0.0001). Phosphocreatine degradation and muscle lactate accumulation were not significantly different between C and DCA. DCA was associated with significantly less muscle fatigue. Resting and steady‐state V̇O2 values during contraction were not significantly different between C and DCA. The time to reach 63 % of the V̇O2 difference between the resting baseline and the steady‐state V̇O2 values during contraction was 22.3 ± 0.5 s in C and 24.5 ± 1.4 s in DCA (n.s.). In this experimental model, activation of PDC by DCA resulted in a stockpiling of acetyl groups at rest and less muscle fatigue, but it did not affect ‘anaerobic’ energy provision and V̇O2 on‐kinetics.
Characterization of the maitotoxin‐activated cationic current from human skin fibroblasts
Authors: Martínez‐François Juan Ramón , Morales‐Tlalpan Verónica , Vaca Luis
Published: July 2002

The maitotoxin (MTX)‐induced cationic current (Imtx) from human skin fibroblasts was characterized using the patch‐clamp technique in whole‐cell configuration. Under resting conditions (absence of MTX), the main current observed is produced by an outwardly rectifying K+ channel which is inhibited by 1 mm TEA. The current reversal potential was −86 mV (n= 12). MTX (500 pm) activated a current with a linear current–voltage relationship and a reversal potential of −10 mV (n= 10). Replacing the extracellular Na+ and K+ with N‐methyl‐d‐glucamine (NMDG) caused a shift of the reversal potential to a value below −100 mV, indicating that Na+ and K+, but not NMDG, carry Imtx. Further ion selectivity experiments showed that Ca2+ carries Imtx also. The resulting permeability sequence obtained with the Goldman–Hodgkin–Katz equation yielded Na+ (1) ≈ K+ (1) > Ca2+ (0.87). The Imtx activation time course reflected the changes in intracellular Ca2+ and Na+ measured with the fluorescent indicators fura‐2 and SBFI, respectively, suggesting that the activation of Imtx brings about an increment in intracellular Ca2+ and Na+. Reducing the extracellular Ca2+ concentration below 1.8 mm prevented the activation of Imtx and the increment in intracellular Na+ induced by MTX. Mn2+ and Mg2+ could not replace Ca2+, but Ba2+ could replace Ca2+. MTX activation of current in 10 mm Ba2+ was approximately 50 % of that induced in the presence of 1.8 mm Ca2+. When 5 mm of the Ca2+ chelator BAPTA was included in the patch pipette, MTX either failed to activate the current or induced a small current (less than 15 % of the control), indicating that intracellular Ca2+ is also required for the activation of Imtx. Intracellular Ba2+ can replace Ca2+ as an activator of Imtx. However, in the presence of 10 mm Ba2+ the activation by MTX of the current was 50 % less than the activation with nm concentrations of free intracellular Ca2+.
Ca2+ regulation in guinea‐pig colonic smooth muscle: the role of the Na+‐Ca2+ exchanger and the sarcoplasmic reticulum
Authors: Bradley Karen N. , Flynn Elaine R. M. , Muir Thomas C. , McCarron John G.
Published: July 2002

To study the contribution of the Na+‐Ca2+ exchanger to Ca2+ regulation and its interaction with the sarcoplasmic reticulum (SR), changes in cytoplasmic Ca2+ concentration ([Ca2+]c) were measured in single, voltage clamped, smooth muscle cells. Increases in [Ca2+]c were evoked by either depolarisation (−70 mV to 0 mV) or by release from the SR by caffeine (10 mm) or flash photolysis of caged InsP3 (InsP3). Depletion of the SR of Ca2+ (verified by the absence of a response to caffeine and InsP3) by either ryanodine (50 μm), to open the ryanodine receptors (RyRs), or thapsigargin (500 nm) or cyclopiazonic acid (CPA, 10 μm), to inhibit the SR Ca2+ pumps, reduced neither the magnitude of the Ca2+ transient nor the relationship between the influx of and the rise in [Ca2+]c evoked by depolarisation. This suggested that Ca2+‐induced Ca2+ release (CICR) from the SR did not contribute significantly to the depolarisation‐evoked rise in [Ca2+]c. However, although Ca2+ was not released from it, the SR accumulated the ion following depolarisation since ryanodine and thapsigargin each slowed the rate of decline of the depolarisation‐evoked Ca2+ transient. Indeed, the SR Ca2+ content increased following depolarisation as assessed by the increased magnitude of the [Ca2+]c levels evoked each by InsP3 and caffeine, relative to controls. The increased SR Ca2+ content following depolarisation returned to control values in approximately 12 min via Na+‐Ca2+ exchanger activity. Thus inhibition of the Na+‐Ca2+ exchanger by removal of external Na+ (by either lithium or choline substitution) prevented the increased SR Ca2+ content from returning to control levels. On the other hand, the Na+‐Ca2+ exchanger did not appear to regulate bulk average Ca2+ directly since the rates of decline in [Ca2+]c, following either depolarisation or the release of Ca2+ from the SR (by either InsP3 or caffeine), were neither voltage nor Na+ dependent. Thus, no evidence for short term (seconds) control of [Ca2+]c by the Na+‐Ca2+ exchanger was found. Together, the results suggest that despite the lack of CICR, the SR removes Ca2+ from the cytosol after its elevation by depolarisation. This Ca2+ is then removed from the SR to outside the cell by the Na+‐Ca2+ exchanger. However, the exchanger does not contribute significantly to the decline in bulk average [Ca2+]c following transient elevations in the ion produced either by depolarisation or by release from the store.
Differential facilitation of N‐ and P/Q‐type calcium channels during trains of action potential‐like waveforms
Authors: Currie Kevin P. M. , Fox Aaron P.
Published: July 2002

Inhibition of presynaptic voltage‐gated calcium channels by direct G‐protein βγ subunit binding is a widespread mechanism that regulates neurotransmitter release. Voltage‐dependent relief of this inhibition (facilitation), most likely to be due to dissociation of the G‐protein from the channel, may occur during bursts of action potentials. In this paper we compare the facilitation of N‐ and P/Q‐type Ca2+ channels during short trains of action potential‐like waveforms (APWs) using both native channels in adrenal chromaffin cells and heterologously expressed channels in tsA201 cells. While both N‐ and P/Q‐type Ca2+ channels exhibit facilitation that is dependent on the frequency of the APW train, there are important quantitative differences. Approximately 20 % of the voltage‐dependent inhibition of N‐type ICa was reversed during a train while greater than 40 % of the inhibition of P/Q‐type ICa was relieved. Changing the duration or amplitude of the APW dramatically affected the facilitation of N‐type channels but had little effect on the facilitation of P/Q‐type channels. Since the ratio of N‐type to P/Q‐type Ca2+ channels varies widely between synapses, differential facilitation may contribute to the fine tuning of synaptic transmission, thereby increasing the computational repertoire of neurons.
Prolonged increase in ciliary beat frequency after short‐term purinergic stimulation in human airway epithelial cells
Authors: Lieb Thomas , Frei Corinne Wijkstrom , Frohock Jeffrey I. , Bookman Richard J. , Salathe Matthias
Published: July 2002

Stimulation of ovine airway epithelial cells with 10 μm ATP for 1 min at 25 °C transiently increased both cytoplasmic calcium (fura‐2 epifluorescence microscopy) and ciliary beat frequency (CBF; differential interference contrast microscopy) with a similar time course. Identical purinergic stimulation of human airway epithelial cells at 25 or 35 °C, however, lead to an increase in CBF that outlasted the calcium transient at least 20 min. While a nitric oxide synthase inhibitor had no effect, pre‐treatment of human cells with inhibitors of cAMP‐dependent kinase (PKA), 10 μm myristoylated PKA‐inhibitory peptide and 1 μm KT‐5720, as well as an inhibitor of adenylyl cyclase, 1 mm SQ22536, blocked the prolonged, but not calcium‐coupled CBF increase. Addition of PKA inhibitors after purinergic stimulation only partially reduced CBF from its elevated plateau. Prolonged CBF increases did not depend on adenosine production as 10 μm UTP had an effect similar to ATP and 8‐sulphophenyl‐theophylline did not block them. After increasing human CBF in a PKA‐dependent manner to a stable plateau with forskolin (10 μm), ATP caused only a transient, calcium‐coupled CBF increase. Calcium transients were necessary for both short‐term and prolonged CBF changes as ATP failed to produce CBF increases after emptying calcium stores with 1 μm thapsigargin. These data suggest that in human, but not ovine airway epithelial cells, ATP‐induced calcium transients activate a signalling cascade including adenylyl cyclase and PKA. The resulting prolonged CBF stimulation does not rely only on PKA activity, suggesting that the decay of CBF is influenced by ciliary phosphatase activity.
Dual effect of blocking agents on Ca2+‐activated Cl− currents in rabbit pulmonary artery smooth muscle cells
Authors: Piper A. S. , Greenwood I. A. , Large W. A.
Published: July 2002

The effects of the Cl− channel antagonists, niflumic acid (NFA), dichloro‐diphenylamine 2‐carboxylic acid (DCDPC) and diisothiocyanato‐stilbene‐2,2′‐disulphonic acid (DIDS) on Ca2+‐activated Cl− current (ICl(Ca)) evoked by adding fixed intracellular calcium concentrations ([Ca2+]i) to the pipette solution were studied in rabbit pulmonary artery myocytes. With 250 and 500 nm[Ca2+]i bath application of NFA (100 μm) increased inward current at negative potentials, but inhibited outward current at positive potentials. On wash out of NFA, ICl(Ca) was greatly enhanced at all potentials. When external Na+ ions were replaced by N‐methyl‐d‐glucamine (NMDG+) NFA still enhanced ICl(Ca) at negative potentials but the increase of ICl(Ca) on wash out was blocked. When the mean reversal potential (Er) of ICl(Ca) was shifted to negative potentials by replacing external Cl− with SCN−, NFA increased inward current but blocked outward current suggesting that the effect of NFA is dependent on current flow. Inclusion of NFA in the pipette solution had no effect on ICl(Ca). Voltage jump experiments indicated that ICl(Ca) displayed characteristic outward current relaxations at +70 mV and inward current relaxations at −80 mV that were abolished by NFA. DCDPC (100 μm) produced similar effects to NFA but 1 mm DIDS produced inhibition of ICl(Ca) at both positive and negative potentials and there was no increase in current on wash out of DIDS. These results suggest that NFA and DCDPC, but not DIDS, simultaneously enhance and block ICl(Ca) by binding to an external site, probably close to the mouth of the chloride channel.
Parametric-Based Determination of Cylindrical Variations in Geometric Tolerancing
Authors: Ba´rcenas C. Carolina , Griffin Paul M.
Published: July 2002

The ANSI Y14.5M Geometric Dimensioning and Tolerancing Standards have been used for many years by practitioners for size and form verification of manufactured parts. However, different parts may satisfy these tolerances and yet perform quite differently because of surface variations not specified in the standards. We present a statistically-based technique for the determination of the type of surface variation for cylindrical parts. This technique is based on a parametric-based part representation used for fitting. The method is illustrated with examples. [S1087-1357(00)00403-2]
Micromechanical Approach of Lamellar Nano-Composites: Influence of the Microstructure on the Yield Strength
Authors: Krummeich R. , Sabar H. , Berveiller M.
Published: July 2002

Actually, micromechanical approaches give only few references related to glide mechanisms in a lamella and especially load transfer mechanism between lamellae in pearlites. At large strains the concept of interphase barrier has to be introduced and considered as the determinant mechanism of hardening compared with the classical bulk work hardening. A micromechanical approach is used to describe a hardening mechanism related to the growth of dislocation loops inside the ferritic lamellae of pearlite and their locking at the interphase boundary. Using Eshelby-Kro¨ner’s formalism for the resolution of the field equations, the calculation of the Helmholtz free energy related to the (internal) morphological variables allows finding driving forces and the strength of interactions between loops and interfacial walls. Results exhibit a linear dependence between the critical stress and the inverse of the true interlamellar spacing, through a lattice orientation factor relative to the lamellar interphase, as observed experimentally (J. Gil Sevillano, 1991, J. Phys. III, 1, pp. 967–988; G. Langford, 1977, Metallurgical Trans A, 8A, pp. 861–875.
Upsetting of Cylinders: A Comparison of Two Different Damage Indicators
Authors: Ga¨nser H.-P. , Atkins A. G. , Kolednik O. , Fischer F. D. , Richard O.
Published: July 2002

Two damage indicators for ductile failure, as proposed by Hancock–Mackenzie–Gunawardena and Atkins, are compared with experimental results from literature for the upsetting process of cylindrical specimens. It is shown, for this specific example, that quite similar results can be obtained from highly different damage indicators as long as they allow for the accumulation of damage proportional both to the equivalent strain and to the stress triaxiality; the specific mathematical structure of the indicator seems to be of minor importance. These findings give some guidelines for the practical choice of a damage indicator for the simulation of industrial forming processes, and suggest the use of the void growth based Hancock–Mackenzie–Gunawardena indicator even for a certain class of bulk forming processes. In addition, a slight geometry dependence of the failure lines obtained by the Hancock–Mackenzie–Gunawardena indicator is obtained that has so far neither been reported by experimentalists, nor can it be reproduced in a comparable manner by the Atkins indicator. A surprising correlation is found between these results and those obtained from an entirely different micromechanical analysis proposed recently by one of the authors.
The Modeling of Unusual Rate Sensitivities Inside and Outside the Dynamic Strain Aging Regime
Authors: Ho Kwangsoo , Krempl Erhard
Published: July 2002

The viscoplasticity theory based on overstress (VBO) is altered by introducing an augmentation function into the dynamic recovery term of the growth law of the equilibrium stress, which is a tensor valued state variable of the model. It is a measure of the defect structure of metals and alloys. The flow law is unaltered but affected by the equilibrium stress whose growth is modified by the augmentation function. The augmentation function does not affect the initial, quasi-elastic region but exhibits a strong influence on the long-time, asymptotic solution that applies approximately when the flow stress is reached in a laboratory experiment. On the basis of the long-time asymptotic solution positive (stress increases with strain rate), zero (no influence of strain rate) and negative rate sensitivity (stress decreases with an increase in strain rate) can be easily modeled. In the simplest case the augmentation function is a constant and the rate sensitivity remains equal throughout the deformation. The modeling of a change from one kind of rate sensitivity, say negative, to another, say positive can be accomplished by making the augmentation function dependent on the accumulated, effective inelastic strain. The theory is applied to model the varying rate sensitivity of a modified 9Cr-1Mo steel, which changes from negative, to zero and to positive with temperature. The unusual rate sensitivities are modeled well together with relaxation and strain rate change tests.
Some Pitfalls of Simplified Modeling for Viscoelastic Sandwich Beams
Authors: Austin Eric M. , Inman Daniel J.
Published: July 2002

It is commonplace in academia to base models of constrained-layer damping treatments on the assumption that the facesheets displace identically during transverse vibrations. This assumption is valid for a large range of problems, particularly for problems common in the era when damping was achieved by applying foil-backed treatments to thin panels. The authors show using a very simple example that oversimplified modeling can skew distributions of modal strain energy, a common indicator of damping. [S0739-3717(00)00204-X]
Optimization of Matrix Heat Exchanger Geometry
Authors: Pavan Kumar K. , Venkatarathnam G.
Published: July 2002

Matrix heat exchangers are used in a number of applications such as helium liquefiers, sorption refrigerators, and in Kleemenko cryocoolers. In this paper the methods for the optimum sizing of balanced flow and unbalanced flow matrix heat exchangers of rectangular and circular shapes are presented. Using the methods developed, the relative size of matrix heat exchangers of rectangular and circular shapes are compared. [S0022-1481(00)01503-6]
Mist/Steam Cooling in a 180-Degree Tube Bend
Authors: Guo Tao , Wang Ting , Gaddis J. Leo
Published: July 2002

An experimental study on mist/steam cooling in a highly heated, horizontal 180-deg tube bend has been performed. The mist/steam mixture is obtained by blending fine water droplets (3∼15 microns) with the saturated steam at 1.5 bar. The test section consists of a thin wall (∼0.9 mm), welded, circular, stainless steel 180-deg tube (20-mm inside diameter) with a straight section downstream of the curved section, and is heated directly by a DC power supply. The experiment was conducted with steam Reynolds numbers ranging from 10,000 to 35,000, wall superheat up to 300°C, and droplet to steam mass ratio at about 1∼2 percent. The results show that the heat transfer performance of steam can be significantly improved by adding mist into the main flow. The highest enhancement occurs at a location about 45-deg downstream of the inlet of the test section. Generally, only a small number of droplets can survive the 180-deg turn and be present in the downstream straight section, as observed by a phase Doppler particle analyzer (PDPA) system. The overall cooling enhancement of the mist/steam flow ranges from 40 percent to 300 percent. It increases as the main steam flow increases, but decreases as the wall heat flux increases. [S0022-1481(00)02003-X]
Inverse Design Model for Radiative Heat Transfer
Authors: Howell J. R. , Ezekoye O. A. , Morales J. C.
Published: July 2002

Inverse solution techniques are applied to the design of heat transfer systems where radiation is important. Various solutions using inverse methods are demonstrated, and it is argued that inverse design techniques provide an alternative to conventional iterative design methods that is more accurate and faster, and can provide a greatly improved first estimate of a thermal design. This estimate can then be used as a trial design in more complete thermal analysis programs for predicting system behavior, eliminating many faulty first design trials. [S0022-1481(00)02703-1]
Study of Using Oxygen-Enriched Combustion Air for Locomotive Diesel Engines
Authors: Assanis D. N. , Poola R. B. , Sekar R. , Cataldi G. R.
Published: July 2002

A thermodynamic simulation is used to study the effects of oxygen-enriched intake air on the performance and nitrogen oxide (NO) emissions of a locomotive diesel engine. The parasitic power of the air separation membrane required to supply the oxygen-enriched air is also estimated. For a given constraint on peak cylinder pressure, the gross and net power output of an engine operating under different levels of oxygen enrichment are compared with those obtained when a high-boost turbocharged engine is used. A 4 percent increase in peak cylinder pressure can result in an increase in net engine power of approximately 10 percent when intake air with an oxygen content of 28 percent by volume is used and fuel injection timing is retarded by 4 degrees. When the engine is turbocharged to a higher inlet boost, the same increase in peak cylinder pressure can improve power by only 4 percent. If part of the significantly higher exhaust enthalpies available as a result of oxygen enrichment is recovered, the power requirements of the air separator membrane can be met, resulting in substantial net power improvements. Oxygen enrichment with its attendant higher combustion temperatures, reduces emissions of particulates and visible smoke but increases NO emissions (by up to three times at 26 percent oxygen content). Therefore, exhaust gas after-treatment and heat recovery would be required if the full potential of oxygen enrichment for improving the performance of locomotive diesel engines is to be realized.
Transient Heat Transfer Measurements Using a Single Wide-Band Liquid Crystal Test
Authors: Licu Dragos N. , Findlay Matthew J. , Gartshore Ian S. , Salcudean Martha
Published: July 2002

A technique using a thermochromic liquid crystal coating to measure film cooling effectiveness (η) and heat transfer coefficient hf has been developed so that both of these important parameters can be obtained, as a function of time, from a single transient test. The technique combines a real-time, true color (24 bit) imaging system with the use of a wide-band liquid crystal coating and multiple event sampling for the simultaneous determination of η and hf from the single test. To illustrate and validate this technique, the flow from compound-angle square jets in a crossflow is examined. The tests, in which the jet air was suddenly heated to about 40°C, lasted 30 seconds. The measured η is compared with measurements made in the same flow under steady-state conditions in a totally different way, using a mass/heat analogy and a flame ionization detector. Good agreement is obtained. Three different blowing ratios M of 0.5, 1.0, and 1.5 are investigated with a constant jet Reynolds number of about 5000. Detailed quantitative comparisons of the η measured in both ways are made for all blowing ratios, and plots of η and hf are presented. [S0889-504X(00)01403-3]
Numerical Formulation for the Dynamic Analysis of Spiral-Grooved Gas Face Seals
Authors: Miller Brad A. , Green Itzhak
Published: July 2002

A numerical formulation is presented for the dynamic analysis of spiral-grooved gas lubricated mechanical face seals with a flexibly mounted stator. Axial and angular modes of motion are considered. Both finite volume and finite element methods are employed for the spatial discretization of the unsteady, compressible form of the Reynolds equation. Self-adapting unwinding schemes are employed in both methods, making them suitable for situations when the compressibility number is high. Both the lubrication analysis and the kinetic analysis are arranged into a single state space form, which makes coupling the two analyses straightforward. The resulting set of equations is solved using a linear multistep ordinary differential equation solver. Examples of the transient response to static stator misalignment and rotor runout are given. Although a properly designed spiral grooved face seal provides good dynamic performance, it is shown that unacceptably large face separation can occur when large angle spiral grooves are employed together with a sealing dam.
Aerodynamic Response of Turbomachinery Blade Rows to Convecting Density Wakes
Authors: Wijesinghe H. S. , Tan C. S. , Covert E. E.
Published: July 2002

A two-dimensional computational study was conducted to characterize the density wake induced force and moment fluctuations on a compressor blade row. The flow simulations indicate unsteady blade excitation generated by: (1) density wake fluid directed to the blade suction surface, (2) axial deflection of the blade passage shock wave position and (3) formation of a separation bubble on the blade suction surface. The blade force and moment fluctuation amplitudes are found to scale with the nondimensional density wake width w/c and a nondimensional density parameter ρ*.
Geometric Parameters Influencing Flow in an Axisymmetric IC Engine Inlet Port Assembly: Part I—Valve Flow Characteristics
Authors: Maier Andreas , Sheldrake Terry H. , Wilcock Dennis
Published: July 2002

Discharge characteristics in an IC engine inlet port and the dependency on geometrical parameters are examined for two valves having seat angles of 40 and 45 deg. The characteristics were established under steady-state conditions over a range of valve lifts up to L/D=0.25 and pressure differentials up to 100 mm H2O. The detailed boundary layer characteristics, indicating flow separation and reattachment on the valve seats, were established with the aid of heat transfer data using the transient liquid crystal technique. Details of the experimental methods for obtaining discharge coefficients and heat transfer coefficients are presented. The discharge and heat transfer data established the expected sequential progression, with lift through the four flow regimes for the valve with a 45 deg seat angle. For the valve with a 40 deg seat angle the four flow regimes were not present. The results demonstrate the extreme sensitivity of the valve flow and boundary layer state to small changes in valve geometry. [S0098-2202(00)00504-6]
Designing the Shaft Diameter for Acceptable Levels of Stress Within an Axial-Piston Swash-Plate Type Hydrostatic Pump
Authors: Manring Noah D.
Published: July 2002

In this research, the diameter of the shaft within an axial-piston swash-plate type hydrostatic pump is considered from a stress point of view. To analyze the loading of the shaft, the components within the pump are studied using a force and torque diagram and it is shown that the loads are applied differently for three main sections of the shaft. From the force and torque diagram, the actual shaft loads are determined based upon the geometry of the pump and the working pressure of the hydraulic system. Using well-accepted machine design practices, governing equations for the shaft diameter are produced for the various regions of loading along the shaft. These equations consider both bending and torsional stresses on the outer surface of the shaft. Results for the required shaft diameter are then computed for a typical pump design and compared to the geometry of an actual shaft. It is noted that stress concentrations can significantly alter these results and that the required shaft diameter can be reduced by applying the proper heat treatments and increasing the shaft strength. Finally, the designer is cautioned regarding the deflection difficulties that can arise when the shaft diameter is reduced too much. [S1050-0472(00)01704-9]
Effects of Stress Shielding on the Transverse Mechanical Properties of Rabbit Patellar Tendons
Authors: Yamamoto Ei , Hayashi Kozaburo , Yamamoto Noritaka
Published: July 2002

With the aim of studying mechanisms of the remodeling of tendons and ligaments, the effects of stress shielding on the rabbit patellar tendon were studied by performing tensile and stress relaxation tests in the transverse direction. The tangent modulus, tensile strength, and strain at failure of non-treated, control patellar tendons in the transverse direction were 1272 kPa, 370 kPa, and 40.5 percent, respectively, whereas those of the tendons stress-shielded for 1 week were 299 kPa, 108 kPa, and 40.4 percent, respectively. Stress shielding markedly decreased tangent modulus and tensile strength in the transverse direction, and the decreases were larger than those in the longitudinal direction, which were determined in our previous study. For example, tensile strength in the transverse and longitudinal direction decreased to 29 and 50 percent of each control value, respectively, after 1 week stress shielding. In addition, the stress relaxation in the transverse direction of stress-shielded patellar tendons was much larger than that of non-treated, control ones. In contrast to longitudinal tensile tests for the behavior of collagen, transverse tests reflect the contributions of ground substances such as proteoglycans and mechanical interactions between collagen fibers. Ground substances provide lubrication and spacing between fibers, and also confer viscoelastic properties. Therefore, the results obtained from the present study suggest that ground substance matrix, and interfiber and fiber–matrix interactions have important roles in the remodeling response of tendons to stress. [S0148-0731(00)00806-2]
On the Robust Stabilization of Nonlinear Uncertain Systems With Incomplete State Availability
Authors: Bartolini G. , Pisano A. , Usai E. , Levant A.
Published: July 2002

The control problem of a class of nonlinear uncertain processes with incomplete state availability is dealt with by means of second-order sliding mode control technique. With the aim of using a continuous control, a combined scheme is proposed in which a 2-sliding mode differentiator and a 2-sliding mode controller are coupled. The stability of the whole observer-controller system is proved for a class of nonlinear plants, and some simulation results are finally provided. [S0022-0434(00)02704-0]
Manufacturability Analysis of Flatness Tolerances in Solid Freeform Fabrication
Authors: Arni Ramakrishna , Gupta S. K.
Published: July 2002

Increasingly, Solid Freeform Fabrication (SFF) processes are being considered for creating functional parts. In such applications, SFF can either be used for creating tooling (i.e., patterns for casting, low volume molds, etc.) or directly creating the functional part itself. In order to create defect free functional parts, it is extremely important to fabricate the parts within allowable dimensional and geometric tolerances. This paper describes a systematic approach to analyzing manufacturability of parts produced using SFF processes with flatness tolerance requirements on the planar faces of the part. Our research is expected to help SFF designers and process providers in the following ways. By evaluating design tolerances against a given process capability, it will help designers in eliminating manufacturing problems and selecting the right SFF process for the given design. It will help process providers in selecting a build direction that can meet all design tolerance requirements.