bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion inhibiting properties of some polyaza macrocyclic compounds on mild steel in acid environments
Authors: Ajmal Mohammad , Rawat Jaya , Quraishi M.A.
Published: July 2002

Macrocyclic compounds constitute a potential class of corrosion inhibitors. In an attempt to develop effective corrosion inhibitors we have synthesized four macrocyclic compounds by condensing o‐ethylene diamine and o‐phenylene diamine with ethylacetoacetate and succinic acid; Their inhibiting action was evaluated on corrosion of mild steel in HCI and H2SO4 by weight loss and potentiodynamic polarization methods. A macrocyclic compound derived by condensing o‐phenylene diamine with ethylacetoacetate exhibited best performance by giving IE of 98 per cent at 500 ppm concentration. The potentiodynamic polarization studies revealed that the tested compounds are either mixed type or predominantly cathodic inhibitors. IE of all the investigated compounds increased significantly on addition of a small concentration KI in both acids due to synergism.
Citius. Altius. Fortius. Peritius: the Skill Olympics and skill competitions
Authors: Wilson John P.
Published: July 2002

The growth of vocational skills competitions demonstrates an increased interest and popularity in companies, schools, colleges, and at regional, national and international levels. There are a number of significant benefits and also challenges associated with the competitions for individuals, their organisations, and for the nation as a whole, and this article draws parallels with the Olympic Games. This article combines research from a variety of sources to give a comprehensive overview of the history and purpose of the competitions and also to describe the various organisations supporting them. This is the first article to map the terrain of skills competitions and, having done so, it calls for further research to be conducted into their impact.
Statistics for food science – VI: correlation and regression (part B)
Authors: Bower John A.
Published: July 2002

Describes the application of correlation and regression in food science and nutrition studies.
The complexity and unpredictability of young people’s learning careers
Authors: Bloomer Martin , Hodkinson Phil
Published: July 2002

Draws from a four‐year longitudinal study of young people’s experiences of learning in further education. The project, funded by the Further Education Development Agency, focused upon relationships between the personal careers of young people and the structured opportunities for education and training available to them. A single case study is used in order to illustrate the kinds of insight which the study afforded. The research revealed a stark contrast between the complexity and unpredictability of the young people’s learning careers, and the more structured approaches in current policy and practice.
Teaching methods for learning outcomes
Authors: Bourner Tom
Published: July 2002

Focuses on learning outcomes in debates on teaching methods in higher education (HE). Presents six core learning outcomes and ten common teaching methods for each of the learning outcomes. Concludes that the search for any universally best teaching method is bound to be fruitless and should give way to the search for better ways of achieving particular learning outcomes. Recommends the widening of the repertoire of teaching methods available to academic staff as a means of diminishing the severity of the trade‐off between teaching effectiveness and teaching efficiency as the unit of teaching resource continues to fall.
Selecting Managers for a Hazardous Environment
Authors: Slaven Georgina , Flin Rhona
Published: July 2002

Following civilian disasters such as Piper Alpha, Hillsborough and
King′s Cross, personnel professionals are rethinking the types of
individuals needed to fill senior posts, considering the demands of
responding to a serious emergency. Presents the results from a project
designed to examine the current selection, training and assessment
procedures for managers of offshore oil and gas installations in the
North Sea, with particular emphasis on their ability to take command in
the event of a serious offshore incident. Personnel and operations
managers in 38 oil and gas exploration and production companies in the
UK were interviewed. Characteristics sought in an offshore installation
manager were leadership and command ability, communication skills, sound
judgement, decisiveness and a stable disposition. Selection decisions
were based predominantly on the candidate′s previous performance,
appraisal reports and managerial recommendations rather than more formal
methods such as interview panels, assessment centres or psychometric
tests. An industry‐wide concern regarding managerial competence has led
to increased use of emergency management simulations for training and
assessment. The lack of formal assessments during the selection
procedure is surprising, but the recent introduction of high fidelity,
emergency management simulations present an additional source of
valuable information on future candidates if assessment data are
collected rigorously.
All year round: the growth of annual hours in Britain
Authors: Gall Gregor
Published: July 2002

Makes a critical examination of annual hours (AH), a relatively new development in industrial relations in Britain. First, considers the extent, sectoral distribution and development of AH before moving to examine the reasons why a growing number of employers are introducing this way of organizing working time. Goes on to review the implications for employees. Concludes that AH is only one of many “new management techniques”, that the extent of AH is still limited, and that the scheme has many detrimental implications for employees.
Workers’ experiences of redundancy: evidence from Scottish defence‐dependent companies
Authors: Donnelly Mike , Scholarios Dora
Published: July 2002

Examines the phenomenon of worker displacement resulting from redundancies within defence‐related industries. Focuses on responses to an extensive survey of people made redundant over a three‐year period in four defence‐dependent companies in Scotland. Examines individuals’ experiences immediately following the announcement of redundancy and in the course of attempting to find re‐employment, this evidence questions the adequacy of redundancy support measures offered both by the companies themselves and by external services. Outlines key finding that individuals’ experiences of the advice and support they received, as well as their success in finding re‐employment, differ depending on gender, age and skill level. Discusses how the nature of re‐employment found by these workers is typically temporary, part‐time and lower skilled, highlighting substantial skill underutilisation. Draws conclusions about how the support and advisory services might be improved for these types of workers and especially for particular groups facing difficulties adapting to redundancy.
Inequality in the careers of NHS nurses
Authors: Lane Nikala
Published: July 2002

Despite the numerical predominance of women in nursing there is a marked concentration of women, especially those working part‐time, in the lower echelons of the profession. The paper presents survey data and interview material from a study of qualified nurses in NHS Wales. By controlling for differences in education and experience in nursing work, it was found that comparable groups of female nurses received unequal employment opportunities. Women with dependent children were primarily located in the lower nurse grades irrespective of their qualifications and experience. Much of this was associated with inflexible working practices, and the low status of part‐time work. Occupational downgrading for female returners was also a significant barrier to career advancement. However, these problems were not recognised by management. Management failed to evaluate the mechanics of their human resource policies in terms which matter to many nurses, in particular with regard to the management of diversity.
Working patterns and working hours: their impact on UK managers
Authors: Worrall Les , Cooper Cary L.
Published: July 2002

Reports on the UMIST‐Institute of Management five‐year study into the changing experiences of UK managers and the impact of organizational change. Examines the patterns of actual working hours generally and by managerial level before going on to explore the reasons managers give to explain their work patterns (over contract hours, evening and weekend working). Contains an assessment of how managers trade‐off work and non‐work activity and the impact of long working hours on managers’ health, morale, productivity, social life and relationships with their partners and children. The analysis reveals a strong relationship between actual hours worked and an increasingly negative impact on all the factors tested.
A walk‐through programmed robot for welding in shipyards
Authors: Ang Marcelo H. , Lin Wei , Lim Ser‐Yong
Published: July 2002

Automating the welding process for the shipbuilding industry is very challenging and important, as this industry relies heavily on quality welds. Conventional robotic welding systems are seldom used because the welding tasks in shipyards are characterised by non‐standardised workpieces which are large but small in batch sizes. Furthermore, geometries and locations of the workpieces are uncertain. To tackle the problem, a Ship Welding Robot System (SWERS) has been developed for the welding process. The main features of the SWERS include a special teaching procedure that allows the human user to teach the robot welding paths at a much easier and faster pace. In addition, operation of the system is made easier through a custom designed man‐machine interface. Through this interface, only a few buttons need to be pressed to command the robot into different modes. Optimised welding parameters can be selected from a large database through a Graphical User Interface system.
Optical correlator for industrial applications, quality control and target tracking
Authors: Bergeron Alain
Published: July 2002

This paper describes a state‐of‐the‐art, commercially available optical correlator that has been used to perform industrial applications. The optical correlator can be used in many different applications including quality control, defect detection, target tracking and pattern recognition. The correlator has been designed to be rugged and is compatible with VGA and NTSC standards. The plug‐and‐play configuration makes it easy for engineers to test new industrial applications.
A cross‐disciplinary model for improved information systems analysis
Authors: Loughman Thomas P. , Fleck Robert A. , Snipes Robin
Published: July 2002

As organizations seek to prosper in ever more complex and changing environments, they will require ever more sophisticated analysis and design tools. Current systems analysis tools function well to identify hardware and software requirements – the mostly technical elements of systems – but are less well suited to address the human component, an understanding of which is crucial to successful organizational analysis and design. The best technically designed system can easily fail when human factors are not explicitly included. The authors show how a combination of systems analysis and communication auditing methods can jointly optimize both the social and technical elements of organizations as they undergo design or business process re‐engineering. As a result of this joint optimization, the authors maintain that systems analysis tools are enriched and thereby enable system designers to explicitly include human and organizational communication factors into an information or business system. A theoretical model and implementation examples are provided.
Algorithmic aspects of deformation dependent loads in non‐linear static finite element analysis
Authors: Mok D.P. , Wall W.A. , Bischoff M. , Ramm E.
Published: July 2002

The present study focusses on algorithmic aspects related to deformation dependent loads in non‐linear static finite element analysis. If the deformation dependency is considered only on the right hand side, a considerable increase in the number of iterations follows. It may also cause failure of convergence in the proximity of critical points. If in turn the deformation dependent loading is included within the consistent linearization, an additional left hand side term emerges, the so‐called load stiffness matrix. In this paper several numerical test cases are used to show and quantify the influence of the two different approaches on the iteration process. Consideration of the complete load stiffness matrix may result in a cumbersome coding effort, different for each load case, and in certain cases its derivation is even not practicable at all. Therefore also several formulations for approximated load stiffness matrices are presented. It is shown that these simplifications not only reduce the additional effort for linearization and implementation, but also keep the iterative costs relatively small and still allow the calculation of the entire equilibrium path.
Effective leadership within hospice and Specialist Palliative Care Units
Authors: Barker Liz
Published: July 2002

In this study the Repertory Grid interview technique was used to investigate constructs of leadership held by a group of male and female senior managers from within hospice and Specialist Palliative Care Units (SPCUs) in the UK. The themes that emerged were compared with those from existing research models of leadership. Results: men and women in these roles describe different constructs of effective leadership. The women’s constructs that emerged were predominantly transformational, whilst the men’s were predominantly transactional. Themes were also identified in this study, which differed from previous studies, i.e. those of political and environment awareness and the valuing of others’ views regardless of their status. These themes do not feature highly in other research, and may be in response to the environment within which hospice and specialist palliative care functions.
A theoretical study of charge iteration
Authors: Aiello G. , Alfonzetti S. , Coco S. , Salerno N.
Published: July 2002

Charge iteration is an iterative procedure for the finite element computation of unbounded electrical fields, created by voltaged conductors. It makes use of a fictitious boundary, enclosing all the conductors, on which the electrical potential is first guessed and then iteratively improved according to the charge lying on the conductor surfaces. Highlights the theoretical foundations of the procedure outside any numerical context. From this useful insight, obtains a model which can aid the user in utilization of the numerical version of the procedure.
Encoded archival description (EAD) conversion: a methodological proposal
Authors: Peis Eduardo , de Moya Félix , Carlos Fernández‐Molina J.
Published: July 2002

The eventual adaptation of archives to new technological possibilities could begin with the creation of digital versions of archival finding aids, which would allow the international diffusion of descriptive information. The Standard Generalized Markup Language (SGML), document type definition (DTD) for archival description known as encoded archival description (EAD) is an appropriate tool for this purpose. Presents a methodological strategy that begins with an analysis of EAD and the informational object to be marked up, allowing the semiautomatic creation of a digital version.
Headlamp and the need for an enlightened view of mentoring for new
school leaders
Authors: Kirkham Glynn
Published: July 2002

Explores the principles of mentoring in schools with reference to
the Headteachers Leadership and Management Programme (Headlamp), a new
UK national scheme which seeks to improve the quality of school
management. Discusses issues such as entitlement, expectations of
others, competences, other players in the team (mentors, LEAs, governing
bodies), and resourcing mentoring. Concludes that for the Headlamp
programme to be truly effective it should include a mentoring component
as a structured element of all efforts to support beginning heads.
Leadership stories: what novices learn by crafting the stories of experienced school administrators
Authors: Danzig Arnold B.
Published: July 2002

Describes research undertaken to study the kinds of understandings and reflections in which administrators‐in‐training engage by writing the story of an experienced administrator. Explains how 17 graduate students in educational administration carried out multiple interviews with practising school administrators concerning their personal biography, professional biography and a discrete incident of professional practice. Reports the findings that novices did get to hear about some of the grey areas in which educational administrators typically operate. The stories provided basic assumptions and details about how experienced administrators performed in specific situations and circumstances and illustrated some of the explicit rules used by administrators to manage problems as well as the more tacit knowledge and assumptions embedded in practice. States that this led students to reflect on their own approaches to practice.
Recent library developments in Vietnam
Authors: Anh Tran Lan
Published: July 2002

This paper investigates the current state of libraries in Vietnam through a descriptive study of selected sectors: public, academic and special library services. Attention is also devoted to the government’s development initiatives with regard to libraries.
Market‐based predictors of interactivity at Southeast Asian online newspapers
Authors: Massey Brian L.
Published: July 2002

Market‐based and press‐freedom variables were tested as predictors of “interactive” online journalism at the Web companions of 17 English‐language Asian newspapers. A multidimensional conception of interactivity was used in the analysis. The findings suggest that market‐based variables predict only certain facets of an online newspaper’s interactivity. Press‐freedom variables were not fruitful predictors.
File not found: the problems of changing URLs for the World Wide Web
Authors: Mary P. Benbow S.
Published: July 2002

Explores the issue of changing URLs and provides a brief analysis of the degree to which change is occurring. Examines the range of potential solutions and provides discussion concerning the reasons for outdated and inaccurate URLs.
Surface macro‐texture design for rapid prototyping
Authors: Jee Haeseong , Sachs Emanuel
Published: July 2002

Rapid prototyping technologies can create a physical part directly from a digital model by accumulating layers of a given material. Providing tremendous flexibility in the part geometry that they can fabricate, these technologies present an opportunity for the creation of new product attributes that cannot be made with existing technologies. For this to be possible, however, various design environments including different fabrication processes need to be considered at the time of design. This paper proposes an extended design automation paradigm for design and fabrication of a new product attribute, surface macro‐texture.
Advances in modeling the effects of selected parameters on the SLS process
Authors: Williams John D. , Deckard Carl R.
Published: July 2002

Selective laser sintering (SLS) is a leading process for developing rapid prototype objects by selectively fusing layers of powder according to numerically defined cross‐sectional geometry. The process has the potential to become an indispensable industrial tool. However, continuous process improvement is necessary. Improved understanding of the parameter effects on the process response is expected to lead to process advances. In this work the analytical problem describing the energy delivery, heat transfer and sintering process along with other pertinent phenomena is studied. Physical experiments and implementation of a numerical simulation are conducted using Bisphenol‐A polycarbonate. The effects of selected parameters on the SLS process response are examined. The primary parameters of interest are the laser power, laser beam velocity, hatch spacing, laser beam spot size and scan line length. This work shows that the secondary process parameters, delay period and number of effective exposures have a significant influence on the process response.
Proteins with β‐(thienopyrrolyl)alanines as alternative chromophores and pharmaceutically active amino acids
Authors: Budisa Nediljko , Alefelder Stefan , Bae Jae Hyun , Golbik Ralph , Minks Caroline , Huber Robert , Moroder Luis
Published: July 2002

L‐β‐(Thieno[3,2‐b]pyrrolyl)alanine and L‐β‐(thieno[2,3‐b]pyrrolyl)alanine are mutually isosteric and pharmaceutically active amino acids that mimic tryptophan with the benzene ring in the indole moiety replaced by thiophene. Sulfur as a heteroatom causes physicochemical changes in these tryptophan surrogates that bring about completely new properties not found in the indole moiety. These synthetic amino acids were incorporated into recombinant proteins in response to the Trp UGG codons by fermentation in a Trp‐auxotrophic Escherichia coli host strain using the selective pressure incorporation method. Related protein mutants expectedly retain the secondary structure of the native proteins but show significantly changed optical and thermodynamic properties. In this way, new spectral windows, fluorescence, polarity, thermodynamics, or pharmacological properties are inserted into proteins. Such an engineering approach by translational integration of synthetic amino acids with a priori defined properties, as shown in this study, proved to be a novel and useful tool for protein rational design.
Coupling of vasopressin‐induced intracellular Ca2+ mobilization and apical exocytosis in perfused rat kidney collecting duct
Authors: Yip Kay‐Pong
Published: July 2002

Arginine vasopressin (AVP) regulates the osmotic water permeability of the kidney collecting duct by inducing exocytotic insertion of aquaporin‐2 into apical membrane. The coupling between AVP‐induced intracellular Ca2+ mobilization and apical exocytosis was investigated in isolated perfused rat inner medullary collecting duct (IMCD) segments using confocal fluorescence microscopy. Changes of [Ca2+]i in IMCD cells were measured with fluo‐4. A novel confocal imaging technique using a styryl dye, FM1‐43, was developed to monitor real‐time exocytosis induced by arginine vasopressin. AVP (0.1 nm) triggered a rapid increase of [Ca2+]i in IMCD cells, followed by sustained oscillations. Ratiometric measurement of [Ca2+]i confirmed that the observed [Ca2+]i oscillation was a primary event and was not secondary to changes in cell volume. The frequencies of [Ca2+]i oscillations in each IMCD cell were independent and time variant. 1‐Deamino‐8‐d‐arginine vasopressin (a V2 receptor agonist, 0.1 nm) simulated the effects of AVP by triggering [Ca2+]i oscillations. In the absence of extracellular Ca2+, ryanodine (0.1 mm) inhibited AVP‐induced Ca2+ mobilization. AVP (0.1 nm) triggered accumulative apical exocytosis in IMCD cells within 20 s after application. Pre‐incubating the IMCD with an intracellular Ca2+ chelator, BAPTA, prevented AVP‐induced intracellular Ca2+ mobilization, apical exocytosis, and increase of osmotic water permeability. These results indicate that AVP, via the V2 receptor, triggers a calcium signalling cascade observed as [Ca2+]i oscillations in the IMCD and that intracellular Ca2+ mobilization is required for exocytotic insertion of aquaporin‐2.
Anticipatory control of hand and eye movements in humans during oculo‐manual tracking
Authors: Barnes G. R. , Marsden J. F.
Published: July 2002

Anticipatory activity of hand and eye has been examined during oculo‐manual tracking of a constant velocity visual target with a hand cursor. Both target and cursor were presented briefly (< 480 ms), but repeatedly, at regular inter‐stimulus intervals (ISI). In Expt 1, the build‐up of hand and eye responses was examined for target velocities varying from 10–40 deg s−1 with an ISI of 2.4 s. The velocity 100 ms after target onset (i.e. prior to visual feedback) for both hand and eye (V100) progressively increased over the first four presentations but then attained a steady state (SS). SS V100 values for eye and hand increased in proportion to target velocity and were thus predictive of forthcoming movement. Hand velocity exceeded eye velocity but both exhibited similar anticipatory trajectories. In Expt 2, target velocity was constant (40 deg s−1) but ISI varied from 0.48–3.74 s. Subjects made anticipatory eye movements for all ISIs but hand movements were often reactive at the longest ISI. If the target failed to appear as expected, subjects initiated predictive hand and eye responses with timing appropriate for the prevailing ISI. In Expt 3, predictive responses were compared with responses to randomised presentation. Peak hand velocity was greater in the randomised mode than in the predictive condition, whereas the converse was true for peak eye velocity. This difference is discussed in terms of the mechanisms of positional error correction in hand and eye. Results provide evidence of similar anticipatory mechanisms in hand and eye, using storage of velocity and timing to achieve rapid prediction of target motion.
Mechanisms of intracortical I‐wave facilitation elicited with paired‐pulse magnetic stimulation in humans
Authors: Hanajima Ritsuko , Ugawa Yoshikazu , Terao Yasuo , Enomoto Hiroyuki , Shiio Yasushi , Mochizuki Hitoshi , Furubayashi Toshiaki , Uesugi Haruo , Iwata Nobue Kobayashi , Kanazawa Ichiro
Published: July 2002

In order to elucidate the mechanisms underlying intracortical I‐wave facilitation elicited by paired‐pulse magnetic stimulation, we compared intracortical facilitation of I1‐waves with that of I3‐waves using single motor unit and surface electromyographic (EMG) recordings from the first dorsal interosseous muscle (FDI). We used a suprathreshold first stimulus (S1) and a subthreshold second stimulus (S2). In most experiments, both stimuli induced currents in the same direction. In others, S1 induced posteriorly directed currents and S2 induced anteriorly directed currents. When both stimuli induced anteriorly directed currents (I1‐wave effects), an interstimulus interval (ISI) of 1.5 ms resulted in extra facilitation of the responses to S1 alone. The latency of this effect was equivalent to that of the I2‐wave from S1. When S1 evoked posteriorly directed currents (I3‐wave recruitment), facilitation occurred at a latency corresponding to the I3‐wave from S1. This facilitation occurred at an ISI of 1.5 ms when both S1 and S2 flowed posteriorly, and at an ISI of approximately 3.5 ms when S1 was posteriorly and S2 was anteriorly directed. Based on these findings, we propose the following mechanisms for intracortical I‐wave facilitation. When S1 and S2 induce currents in the same direction, facilitation is produced by summation between excitatory postsynaptic potentials (EPSPs) elicited by S1 and subliminal depolarization of interneurones elicited by S2 directly. When S1 and S2 induce currents in the opposite direction, facilitation is produced by the same mechanism as above or by temporal and spatial summation of EPSPs elicited by two successive stimuli at interneurones or corticospinal neurones of the motor cortex.
Vasodilatation in response to repeated anodal current application in the human skin relies on aspirin‐sensitive mechanisms
Authors: Durand S. , Fromy B. , Bouyé Ph. , Saumet J. L. , Abraham P.
Published: July 2002

The vasodilatation resulting from prolonged square‐wave monopolar current application as used in iontophoresis is assumed to rely on an axon reflex. Involvement of prostaglandins in the anodal current‐induced vasodilatation remains unclear. We tested the hypothesis that prostaglandins participate in a sensitisation mechanism to current application rather than as direct vasodilators. In healthy volunteers, laser Doppler flowmetry (LDF) was recorded in the forearm during and following isolated or repeated 0.1 mA transcutaneous anodal current applications, using deionised water as a vehicle. Segmented current applications of 6 or 12 mC resulted in an LDF increase twice that observed following current applications of comparable total charge delivered all at once (P < 0.05). Following a 1 min anodal application, a slow and prolonged LDF drift occurred (slope: 0.3 ± 0.5 arbitrary units min−1). When the same current application was repeated after intervals of 5 and 20 min, an abrupt vasodilatation occurred, with maximal LDF amplitude of 53.5 ± 34.0 and 48.2 ± 19.1 arbitrary units, respectively. Pretreatment with 1 g oral aspirin abolished the abrupt vasodilatation to repeated current application but not the initial slow drift. We suggest that vasodilatation occurs through two parallel pathways: (1) a slow progressive drift of LDF of limited amplitude insensitive to aspirin pretreatment, and (2) an abrupt vasodilatation probably resulting from afferent fibre activation, appearing if a preliminary sensitisation by current application is performed. Sensitisation lasts for at least 20 min, and is blocked by aspirin, suggesting participation of prostanoids.
Conformation‐dependent regulation of inward rectifier chloride channel gating by extracellular protons
Authors: Arreola Jorge , Begenisich Ted , Melvin James E.
Published: July 2002

We have investigated the gating properties of the inward rectifier chloride channel (Clir) from mouse parotid acinar cells by external protons (H+o) using the whole‐cell patch‐clamp technique. Increasing the pHo from 7.4 to 8.0 decreased the magnitude of Clir current by shifting the open probability to more negative membrane potentials with little modification of the activation kinetics. The action of elevated pH was independent of the conformational state of the channel. The effects of low pH on Clir channels were dependent upon the conformational state of the channel. That is, application of pH 5.5 to closed channels essentially prevented channel opening. In contrast, application of pH 5.5 to open channels actually increased the current. These results are consistent with the existence of two independent protonatable sites: (1) a site with a pK near 7.3, the titration of which shifts the voltage dependence of channel gating; and (2) a site with pK = 6.0. External H+ binds to this latter site (with a stoichiometry of two) only when the channels are closed and prevent channel opening. Finally, block of channels by Zn2+ and Cd2+ was inhibited by low pH media. We propose that mouse parotid Clir current has a bimodal dependence on the extracellular proton concentration with maximum activity near pH 6.5: high pH decreases channel current by shifting the open probability to more negative membrane potentials and low pH also decreases the current but through a proton‐dependent stabilization of the channel closed state.
Role of Unloading in Machining of Brittle Materials
Authors: Chandra A. , Wang K. , Huang Y. , Subhash G. , Miller M. H. , Qu W.
Published: July 2002

A simple stress based defect evolution model is developed to assess the influence of various process parameters on material removal rate (MRR) and induced damage during grinding of brittle materials. Model predictions for normal and lateral damage zones under normal indentations are first compared to fracture models as well as experimental observations on pyrex glass. Process design options for reducing induced damage in the finished part, and increasing MRR are considered next. In particular, the potential of a new design avenue involving intermittent unloading is investigated. Simulation results show that intermittent unloading can potentially facilitate increase in Force/Grit without increasing the associated surface and sub-surface fragmentation in the finished part. Preliminary experimental observations on single grit scratching of pyrex glass also show a similar trend. [S1087-1357(00)01902-X]
Experimental Investigation of Adaptive Control Applied to HSFD Supported Rotors
Authors: El-Shafei A. , El-Hakim M.
Published: July 2002

This paper describes the experimental application of adaptive control to Hybrid Squeeze Film Damper (HSFD) supported rotors. The HSFD has been shown to be an adaptive damper capable of providing infinite damper configurations between short and long damper configurations. Previously, theoretical investigations of the adaptive control of HSFD concentrated on the development of the model reference adaptive control (MRAC) method, as well as development of a nonlinear reference model. Simulations of the performance of the adaptive controller during run-up and coast-down indicated the superior performance of the adaptive controller. In this paper, the adaptive controller is tested on a multi-mode rotor. A test rig is designed and developed using computer control. A simple reference model is investigated consisting of a second order system. Three forms for adaptation gain are studied. The results of the experimental investigation illustrated the performance capabilities of the adaptive controller applied to the HSFD, and moreover indicated the possibility of simple design for the adaptive controller. [S0742-4795(00)01603-3]
Minimization of Energy in the Multipass Rolling Process
Authors: Samad M. Abdul , Rao Ravi S.
Published: July 2002

This research focuses on the optimization of the flat rolling process. In order to optimize the process effectively, the existing process model has been especially enhanced—in the neutral zone where the friction changes sign over a region rather than at a point. Pressure and frictional stress distributions as well as total load and torque are thereby estimated as functions of the various rolling parameters. Roll flattening has also been taken into account. The main problem of determining the optimum design parameters of multipass rolling has been considered. The problem has been formulated and solved as a constrained nonlinear programming problem by considering the radius of the rolls, the front and back tensions as design variables. Optimum number of passes have been found, so that the total energy consumed by the tandem mill is minimized. Constraints are placed on the induced stresses, the neutral angle, the angle of bite and the deflections of the rolls, for both cold and hot rolling processes.
Elastodynamic Fracture Analysis of Multiple Cracks by Laplace Finite Element Alternating Method
Authors: Chen W.-H. , Chang C.-L. , Tsai C.-H.
Published: July 2002

The Laplace finite element alternating method, which combines the Laplace transform technique and the finite element alternating method, is developed to deal with the elastodynamic analysis of a finite plate with multiple cracks. By the Laplace transform technique, the complicated elastodynamic fracture problem is first transformed into an equivalent static fracture problem in the Laplace transform domain and then solved by the finite element alternating method developed. To do this, an analytical solution by Tsai and Ma for an infinite plate with a semi-infinite crack subjected to exponentially distributed loadings on crack surfaces in the Laplace transform domain is adopted. Finally, the real-time response can be computed by a numerical Laplace inversion algorithm. The technique established is applicable to the calculation of dynamic stress intensity factors of a finite plate with arbitrarily distributed edge cracks or symmetrically distributed central cracks. Only a simple finite element mesh with very limited number of regular elements is necessary. Since the solutions are independent of the size of time increment taken, the dynamic stress intensity factors at any specific instant can even be computed by a single time-step instead of step-by-step computations. The interaction among the cracks and finite geometrical boundaries on the dynamic stress intensity factors is also discussed in detail. [S0021-8936(00)02103-6]
Effect of Outflow Orientation on Heat Transfer and Pressure Drop in a Triangular Duct With an Array of Tangential Jets
Authors: Hwang J.-J. , Chang B.-Y.
Published: July 2002

Experiments are conducted to study the heat transfer and pressure drop characteristics in a triangular duct cooled by an array of tangential jets, simulating the leading-edge cooling circuit of a turbine blade. Coolant ejected from a high-pressure plenum through an array of orifices is aimed at the leading-edge apex and exits from the radial outlets. Three different outflow orientations, namely coincident with the entry flow, opposed to the entry flow, and both, are tested for various Reynolds numbers 12600⩽Re⩽42000. A transient liquid crystal technique is used to measure the detailed heat transfer coefficients on two walls forming the leading-edge apex. Flow rate across each jet hole and the crossflow development, which are closely related to the local heat transfer characteristics, are also measured. Results show that increasing Re increases the heat transfer on both walls. The outflow orientation affects significantly the local heat transfer characteristics through influencing the jet flow together with the crossflow in the triangular duct. The triangular duct with two openings is recommended since it has the highest wall-averaged heat transfer and the moderate loss coefficient among the three outflow orientations investigated. Correlations for wall-averaged Nusselt number and loss coefficient in the triangular duct have been developed by considering the Reynolds number for three different outflow orientations. [S0022-1481(00)01204-4]
Head Injury in Facial Impact—A Finite Element Analysis of Helmet Chin Bar Performance
Authors: Chang Chih-Han , Chang Li-Tung , Chang Guan-Liang , Huang Shyh-Chour , Wang Chiou-Hua
Published: July 2002

The chin bar of a motorcycle helmet protects the rider from facial and head injuries. To evaluate the protective performance of chin bars against head injuries from facial impacts, an explicit finite element method was used to simulate the Snell Memorial Foundation test and a proposed drop test. The maximum acceleration and Head Injury Criterion (HIC) were employed to assess the impact-absorbing capability of the chin bar. The results showed that the proposed approach should be more practical than the Snell test, and provided more information for improving the chin bar design to protect against head injuries. The shell stiffness was important in determining the protective ability of the chin bar, but a chin bar with only an outer shell and comfort foam offered inadequate protection. An energy-absorbing liner was essential to increase the protective performance of the chin bar and the liner density should be denser than that used in the cranial portion of the helmet. For the chin bar with energy-absorbing liner, a shell design that is less stiff would provide better protection. [S0148-0731(00)01206-1]
An Experimental Evaluation of Advanced Leading Edge Impingement Cooling Concepts
Authors: Taslim M. E. , Setayeshgar L. , Spring S. D.
Published: July 2002

The main objective of this experimental investigation was to measure the convective heat transfer coefficient of impingement for different target wall roughness geometries of an airfoil leading edge, for jet to wall spacings and exit flow schemes. Available data in the open literature apply mostly to impingement on flat or curved smooth surfaces. This investigation covered two relatively new features in blade leading-edge cooling concepts: curved and roughened target surfaces. Experimental results are presented for four test sections representing the leading-edge cooling cavity with cross-over jets impinging on: (1) a smooth wall, (2) a wall with high surface roughness, (3) a wall roughened with conical bumps, and (4) a wall roughened with tapered radial ribs. The tests were run for two supply and three exit flow arrangements and a range of jet Reynolds numbers. The major conclusions of this study were: (a) There is a heat transfer enhancement benefit in roughening the target surface; (b) while the surface roughness increases the impingement heat transfer coefficient, the driving factor in heat transfer enhancement is the increase in surface area; (c) among the four tested surface geometries, the conical bumps produced the highest heat transfer enhancement.
Contact Stresses in Multilayered Strands Under Tension and Torsion1
Authors: Kumar K. , Botsis J.
Published: July 2002

First, an attempt is made to experimentally test the validity of the linear deformation derivative results earlier developed for the multilayered wire-rope strands under tension and torsion. The theoretical results are next utilized to obtain analytical expressions for the maximum contact stresses induced in the multilayered strands with metallic wire core. These closed-form solutions provide some useful design insights into the influence of several important cable parameters and material properties on the resulting contact stresses. The strong influence of the material modulus of elasticity on the critical stresses is highlighted. Significantly, the analysis brings out how the contact stresses can rise to an order of magnitude higher levels than that of the nominal stresses.
Flow Structure and Particle Transport in a Triple Bifurcation Airway Model1
Authors: Zhang Z. , Kleinstreuer C. , Kim C. S.
Published: July 2002

Considering steady laminar incompressible flow in a triple bifurcation, which represents generations three to six of the human respiratory system, air flow fields and micron-particle transport have been simulated for several combinations of relatively high and low inlet Reynolds and Stokes numbers. While the upstream bifurcations are hardly affected by the third bifurcation, complex air and particle flow fields occur in the daughter tubes leading to the third dividers. Variations in Reynolds number, 500⩽Re⩽2000, and Stokes number, 0.04⩽St⩽0.12, cause locally changing vortical air flows as well as irregular particle motions. Preferential concentration of particles can be induced by the secondary vortical flow in the tubes when the inlet Reynolds number is high enough. The air and particle velocity profiles in the third daughter tubes are still quite different from those in the upstream tubes, which indicates that additional downstream effects are possible. This work may contribute to respiratory dose estimation in health risk assessment studies, as well as the analyses of drug aerosol delivery.
Clouds Over Soot Evaporation: Errors in Modeling Laser-Induced Incandescence of Soot
Authors: Smallwood G. J. , Snelling D. R. , Liu F. , Gu¨lder O¨. L.
Published: July 2002

The ambiguity and incorrect treatment of the evaporation term among some LII models in the literature are discussed. This study does not suggest that the correct formulation presented for the evaporation model is adequate, or that it reflects the soot evaporation process under intense evaporation. The emphasis is that the current evaporation model must be used correctly in the evaluation of the LII model against experimental data. Numerical results are presented to demonstrate the significance of the molecular weight associated with the heat of evaporation and the thermal velocity of carbon vapor on the results obtained with the evaporation model. Other errors frequently repeated in the literature are also identified.
On Prediction of Thermal-Hydraulic Characteristics of Square-Sectioned Ribbed Cooling Ducts
Authors: Saidi Arash , Sunde´n Bengt
Published: July 2002

This paper presents the results of an investigation on prediction of local and mean thermal-hydraulic characteristics in rib-roughened ducts of square cross section. the Navier–Stokes and energy equations together with two low-Re k–ε turbulence models are solved numerically. The Reynolds turbulent stress tensor is calculated by two methods, namely, an eddy viscosity model (EVM) and an explicit algebraic stress model (EASM). The pressure–velocity coupling is handled by the SIMPLEC algorithm and calculations were carried out on a collocated grid. The convection–diffusion terms were calculated using the hybrid scheme (the changes in the results obtained by the other schemes, e.g., QUICK and Van Leer, were not significant). The considered ribbed duct configuration is identical to that in an experimental study and comparisons between the predictions and experimental results are provided. A discussion of the capabilities of the two methods (EVM and EASM) is presented.
Identifying, Correcting, and Avoiding Errors in Computer-Aided Design Models Which Affect Interoperability
Authors: Gu Hong , Chase Thomas R. , Cheney Douglas C. , Bailey Thomas “Tim” , Johnson Douglas
Published: July 2002

Interoperability characterizes the ability of computer-aided design (CAD) models to accurately represent objects in concurrent engineering environments. The diagnostic set of available software for interoperability testing is described. This set is utilized to develop a visual catalog of possible interoperability errors. The value of utilizing interoperability testing software is appraised by way of a real-world case study. Numerous significant errors are identified in a suite of 140 parts. “Geometry errors” are shown to be more common than “topology errors.” The case study suggests that sensitizing the designer to the nature of typical errors leads to improvement in initial model quality. Example errors are described to illustrate their nature and how to eliminate them. Informal guidelines to improve quality upon initial design are deduced. The development of errors due to inconsistent system accuracy settings during data exchange is explored.
Multicomponent and High-Pressure Effects on Droplet Vaporization
Authors: Aggarwal S. K. , Mongia H. C.
Published: July 2002

This paper deals with the multicomponent nature of gas turbine fuels under high-pressure conditions. The study is motivated by the consideration that the droplet submodels that are currently employed in spray codes for predicting gas turbine combustor flows do not adequately incorporate the multicomponent fuel and high-pressure effects. The quasi-steady multicomponent droplet model has been employed to investigate conditions under which the vaporization behavior of a multicomponent fuel droplet can be represented by a surrogate pure fuel droplet. The physical system considered is that of a multicomponent fuel droplet undergoing quasi-steady vaporization in an environment characterized by its temperature, pressure, and composition. Using different vaporization models, such as infinite-diffusion and diffusion-limit models, the predicted vaporization history and other relevant properties of a bicomponent droplet are compared with those of a surrogate single-component fuel droplet over a range of parameters relevant to gas turbine combustors. Results indicate that for moderate and high-power operation, a suitably selected single-component (50 percent boiling point) fuel can be used to represent the vaporization behavior of a bicomponent fuel, provided one employs the diffusion-limit or effective-diffusivity model. Simulation of the bicomponent fuel by a surrogate fuel becomes increasingly better at higher pressures. In fact, the droplet vaporization behavior at higher pressures is observed to be more sensitive to droplet heating models rather than to liquid fuel composition. This can be attributed to increase in the droplet heatup time and reduction in the volatility differential between the constituent fuels at higher pressures. For ignition, lean blowout and idle operations, characterized by low pressure and temperature ambient, the multicomponent fuel evaporation cannot be simulated by a single-component fuel. The validity of a quasi-steady high-pressure droplet vaporization model has also been examined. The model includes the nonideal gas behavior, liquid-phase solubility of gases, and variable thermo-transport properties including their dependence on pressure. Predictions of the high-pressure droplet model show good agreement with the available experimental data over a wide range of pressures, implying that quasi-steady vaporization model can be used at pressures up to the fuel critical pressure.