bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization design of a compressor cascade airfoil using a Navier-Stokes solver and genetic algorithms
Authors: Li J , Satofuka N
Published: August 2003

This paper presents the multiobjective aerodynamic design of a compressor cascade using a Navier-Stokes solver and genetic algorithms (GAs). The design goal of a compressor cascade optimization is to maximize the pressure rise and minimize the total pressure loss at the given flow condition on the basis of the controlled diffusion airfoil (CDA). A two-branch Boltzmann selection and Pareto optimal solution criteria method are applied to GAs for the multiobjective optimization design. The optimization performance of the present multiobjective GAs is demonstrated by the typical test function. Bezier curves are adopted to represent the geometry of the cascade shape. The aerodynamic performance of design candidates is evaluated using a two-dimensional Navier-Stokes solver. The obtained results of the compressor cascade design provide many Pareto optimal solutions. A certain Pareto optimal solution with higher pressure rise and lower total pressure loss is demonstrated to have improved aerodynamic performance than the existed CDA.
Shape optimization of two turbine stages using the deformed polyhedron method and a three-dimensional RANS solver
Authors: Yershov S , Rusanov A , Shapochka A , Lampart P , Świrydczuk J , Gardzilewicz A
Published: August 2003

A combination of the Nelder-Mead deformed polyhedron method with a three-dimensional RANS solver is used in the paper for the constrained optimization of the shape of two selected turbine stages. The objective function is the total stage loss, with the exit kinetic energy also considered a loss. There are constraints imposed on the mass flowrate, exit angle, average reaction and reaction at tip and root. The exit angle and reactions are not allowed to assume values beyond prescribed ranges, whereas a penalty function is imposed on the mass flowrate if it falls outside the required interval. Among the optimized parameters are stator and rotor stagger and twist angles and stator sweep and lean, both straight and compound. The computations of the flowfield are compressible, viscous and three-dimensional. Turbulence effects are taken into account using the modified Baldwin-Lomax model. The process of optimization gives new designs with improved calculated efficiency. Part of the improvementis due to optimization of the stagger angles and blade numbers, as in classical one-dimensional optimization, and part of it is due to the fact that the blades assume new three-dimensional stacking lines.
Thermodynamic performance study of an integrated gasification fuel cell combined cycle—an energy analysis
Authors: Ghosh S , De S
Published: August 2003

In this paper an integrated gasification combined cycle (IGCC) with a high-temperature, pressurized solid oxide fuel cell (SOFC) in the topping cycle and a single-pressure, non-reheat steam bottoming cycle has been conceptualized and analysed. An energy analysis is done for this combined cycle. The study reveals that an overall efficiency above 54 per cent is achievable for this combined cycle, which also offers satisfactory environmental friendliness. A higher pressure ratio across the gas turbine is found to improve the overall efficiency of the combined cycle. The SOFC operating temperature is found to influence the performance of the combined cycle in different ways, depending on the pressure ratios.
Gas path fault diagnosis framework for a three-shaft gas turbine
Authors: Ogaji S. O T. , Singh R
Published: August 2003

A diagnostic framework has been developed for the detection of faults in the gas path of a three-shaft aeroderivative gas turbine thermodynamically similar to the Rolls Royce RB211-24GT. The framework involves a large-scale integration of artificial neural networks (ANNs) designed and trained to detect, isolate and assess faults in the gas path components of the engine. The approach has the capacity to assess both multiple-component and multiple-sensor faults. The results obtained demonstrate the promise of ANNs applied to engine diagnostic activities.
An intelligent system for interpreting the nuclear refuelling process within an advanced gas-cooled reactor
Authors: Steele J. A. , Martin L. A. , McArthur S. D J. , Moyes A , McDonald J. R. , Howie D , Elrick R , Yule I. Y.
Published: August 2003

Evaluation of the data produced during the refuelling process in a nuclear power plant is required to ensure proper ‘set-down’ of the fuel assembly, thereby allowing the continued and safe operation of the station. The process of evaluating the data can be time consuming owing to the large amounts of data requiring considerable domain experience and interpretation. This paper presents an intelligent system (IS) to automate the process of data analysis, thereby shortening the evaluation time and providing an explanation of the reasoning behind its conclusions. The intelligent system utilizes a knowledge-based system (KBS), neural network based classification, K-means clustering techniques and rule induction methods to evaluate the data and inform the operator of any errors encountered.
Aerodynamic design optimization of a compressor rotor with Navier—Stokes analysis
Authors: Ahn C-S , Kim K-Y
Published: August 2003

Design optimization of a transonic compressor rotor (NASA rotor 37) using the response surface method (RSM) and three-dimensional Navier-Stokes analysis has been carried out in this work. The Baldwin—Lomax turbulence model was used in the flow analysis. Three design variables were selected to optimize the stacking line of the blade. Data points for response evaluations were selected by D-optimal i design, and a linear programming method was used to optimize the response surface. As a main result of the optimization, adiabatic efficiency was successfully improved. It was found that the optimization process provides reliable design of a turbomachinery blade with reasonable computing time.
Kinetic combustion neural modelling integrated into computational fluid dynamics
Authors: Cerri G , Michelassi V , Monacchia S , Pica S
Published: August 2003

The attempt to replace traditional chemical kinetics model calculations with new ones based on neural networks (NNs) has been successfully carried out. The paper deals with the methodology that has been followed to replace traditional model calculations with neural models (NMs) for methane/air combustion. The reacting flowfield has been described with account taken of the detailed chemical reaction mechanism. Convective and turbulent diffusive transport of species has been taken into consideration by means of a well-known finite volume computational fluid dynamics (CFD) code. Two versions of such a mechanism have been developed. The first one is based on traditional differential equations representing the species production rates. Such equations are integrated over the time intervals related to the cell volumes and local volumetric flows. The second version is based on neural models which can extract and store knowledge from the data presented to them. The neural model capability of connecting output to input quantities by means of the stored knowledge leads to very fast calculations. A reduced combustion mechanism involving 20 species and 68 reactions has been developed both for the traditional calculation and for the neural model calculations. It can be concluded that calculations using chemical kinetics neural models show a 42 times shorter CPU time than that of the traditional procedures, with a comparable solution accuracy of the combustion flowfields.
Thermographic phosphor thermometry for film cooling studies in gas turbine combustors
Authors: Feist J. P. , Heyes A. L. , Seefelt S
Published: August 2003

The paper describes the application of thermographic phosphors for surface temperature measurements in gas turbine combustors and on surrounding components. Thermographic phosphors enable many of the problems associated with the application of conventional thermometry techniques in a combustion environment to be overcome. They consist of a ceramic host matrix with a lanthanide ion dopant. When illuminated with UV light, they exhibit luminescence which is temperature dependent by virtue of variations in the relative intensities of distinct emission lines or in the time constant of the exponential decay that occurs once excitation has ceased. The authors have calibrated the response of a range of phosphors and demonstrated that a useful dynamic response exists up to at least 1400±C. Furthermore, to demonstrate the utility of the technique, surface temperatures have been measured over a small region within a model gas turbine combustor. In this region the temperature distribution was measured with an estimated uncertainty of ±10 K, with the absolute temperature values confirmed by thermocouple measurements within the experimental uncertainties of this technique.
Modelling of a bluff body stabilized CH4/H2 flame based on a laminar flamelet model with emphasis on NO prediction
Authors: Hossain M , Malalasekera W
Published: August 2003

A laminar flamelet model prediction of a bluff body stabilized CH4/H2 flame is reported. The predicted results of temperature and major and minor species as well as NO are compared against the Raman/Rayleigh/LIF data available from the University of Sydney. The effect of differential diffusion is also studied. The calculation shows that temperature and concentration of major and minor species are better predicted by the unity Lewis number flamelet. It is also shown that the current steady state flamelet approach has difficulties in predicting experimental NO levels.
Venturi valves for steam turbines and improved design considerations
Authors: Zhang D , Engeda A
Published: August 2003

As a turbine governing valve, the venturi valve has been widely used in large turbines to regulate inlet flow for about 40 years. It is favoured in terms of low total pressure loss because of the converging-diverging configurations of the valve passage. However, as turbines become larger and larger, a number of valve failure incidents have been reported, and there is a great demand for improved designs. Yet, because of the complicated nature of the fluid—structure interaction mechanisms, the basic mechanism causing valve vibration and failure is still far from being fully understood. Most of the available literature relies heavily on experiments before the 1980s. There are several improved designs by the trial and error method, but governing rules, or even a clear direction for improvement, are almost non-existent. There has still seen no published investigation using computational fluid dynamics (CFD) tools. As CFD is increasingly recognized as a powerful tool for understanding complicated fluid phenomena, a two-dimensional numerical investigation was performed in the present work. The study revealed that valve plug vibration is due to hydraulic forces acting on the plug at its balanced position and fluid-induced excitation as the plug vibrates in the lateral and vertical directions. All this relates to unexpected asymmetric flow patterns. By changing the plug shape, the flow patterns can be made much more symmetric, which reduces the intensity of steady forces and fluid plug interaction.
A gas turbine diagnostic approach with transient measurements
Authors: Li Y. G.
Published: August 2003

Most gas turbine performance analysis based diagnostic methods use the information from steady state measurements. Unfortunately, steady state measurement may not be obtained easily in some situations, and some types of gas turbine fault contribute little to performance deviation at steady state operating conditions but significantly during transient processes. Therefore, gas turbine diagnostics with transient measurement is superior to that with steady state measurement. In this paper, an accumulated deviation is defined for gas turbine performance parameters in order to measure the level of performance deviation during transient processes. The features of the accumulated deviation are analysed and compared with traditionally defined performance deviation at a steady state condition. A non-linear model based diagnostic method, combined with a genetic algorithm (GA), is developed and applied to a model gas turbine engine to diagnose engine faults by using the accumulated deviation obtained from transient measurement. Typical transient measurable parameters of gas turbine engines are used for fault diagnostics, and a typical slam acceleration process from idle to maximum power is chosen in the analysis. The developed diagnostic approach is applied to the model engine implanted with three typical single-component faults and is shown to be very successful.
Numerical and experimental investigation of unsteady flow interaction in a low-pressure multistage turbine
Authors: Höhn W
Published: August 2003

The paper presents results of unsteady viscous flow calculations and corresponding cold flow experiments on a three-stage low-pressure turbine. The investigation emphasizes the study of unsteady flow interaction. A time-accurate, Reynolds-averaged Navier-Stokes solver is applied for the computations. Turbulence is modelled using the Spalart-Allmaras one-equation turbulence model. The influence of modern transition models on the unsteady flow predictions is investigated. Integration of the governing equations in time is performed with a four-stage Runge-Kutta scheme, which is accelerated by a two-grid method in the viscous boundary layer around the blades. At the inlet and outlet, non-reflecting boundary conditions are used. The quasi-three-dimensional calculations are conducted on a stream surface around mid-span, allowing a varying stream tube thickness. A three-stage, low-pressure turbine rig of a modern commercial jet engine is used for a study of the unsteady flow interaction. The numerical method is able to capture important unsteady effects found in the experiments, i.e. unsteady transition as well as the bladerow interaction. In particular, the flowfield with respect to time-averaged and unsteady quantities such as surface pressure, vorticity and turbulence intensity is compared with the experiments conducted in the cold airflow test rig.
Exergy tools
Authors: Wall G
Published: August 2003

This paper presents a number of exergy-based concepts and methods, e.g. efficiency concepts, exergy flow diagrams, exergy utility diagrams (EUDs), life cycle exergy analysis (LCEA) and exergy economy optimization (EEO). These tools are useful in order to describe, analyse and optimize energy conversion systems.
Wear performance of polytetrafluoroethylene-metal coatings in rolling/sliding line contact
Authors: Akdogan G , Stolarski T. A. , Tobe S
Published: August 2003

The study, presented in this paper, aims to shed some light on the effect of deposited polytetrafluorothylene (PTFE) on the tribological performance of Al bronze and Mo coatings in rolling/sliding contact conditions by using a two-disc machine.

The experimental results revealed that both PTFE-Al bronze and PTFE-Mo coatings had outstanding wear and surface fatigue resistance. Although PTFE-Al bronze coatings had relatively better wear behaviour than PTFE-Mo coatings under both pure rolling and rolling/sliding conditions, both coatings had no significant surface damage after 1.2 × 106 load cycles. Optical microscopy and scanning electron microscopy studies suggest that metallic asperities in the coating matrix acted as the load carrier. PTFE was lost by an adhesive wear due to transfer film formation on the counter steel surface, which in turn provided good lubrication of the contact zone.
Measurements of the coefficients of friction of different lubricants during impact under high pressure and shear
Authors: Workel M. F. , Dowson D , Ehret P , Taylor C. M.
Published: August 2003

For a comprehensive set of lubricants the friction coefficients were determined under very high pressures and shear rates by means of a ball impact experiment. Measurements of the limiting shear stresses were obtained for a large range of pressures, from about 2 to 4 GPa, as typically encountered in elastohydrodynamic contacts. It was shown that under these conditions the limiting shear stresses increased less than proportionally with the pressure; i.e. the coefficients of friction were decreasing functions of the pressures. The results were compared with previously reported values from the literature and in general good agreement was obtained.
Static characteristics of aerostatic porous journal bearings with a surface-restricted layer
Authors: Yoshimoto S , Tozuka H , Dambara S
Published: August 2003

Graphite porous materials have been successfully used in an aerostatic bearing. This is because graphite porous materials have a lower permeability than porous metal, which makes it possible to achieve a higher stiffness in aerostatic bearings. However, aerostatic porous bearings have a disadvantage in that they are prone to cause pneumatic hammer instability. Therefore, a restricted layer which has a permeability lower than the bulk of the porous material is usually formed on the bearing surface to avoid this instability. In this paper, the static characteristics of aerostatic porous journal bearings with a surface-restricted layer are investigated theoretically and experimentally. In addition, the effects of a surface-restricted layer on the static characteristics are discussed for two types of loads, symmetrical and coupled.
An analysis of the influence of oil supply conditions on the thermohydrodynamic performance of a single-groove journal bearing
Authors: Costa L , Miranda A. S. , Fillon M , Claro J. C. P.
Published: August 2003

In this work a thermohydrodynamic analysis has been developed in order to investigate the influence of oil supply conditions on the performance of a journal bearing. The supply conditions considered were oil supply temperature, supply pressure, groove length and groove location. To carry out this study, the hydrodynamic pressure distribution inside the bearing has been determined using a mass-conserving cavitation model with realistic supply conditions. The energy equation and the heat conduction equation have been used for the determination of oil film and bush temperature distributions. The agreement observed between theoretical predictions and experimental published data is acceptable. Quantitative information shows that the oil supply conditions affect bearing performance parameters in different ways. Oil flowrate was markedly affected by all supply parameters studied. Power loss, maximum bush temperature and minimum film thickness were mainly dependent on oil supply temperature. The effect of supply pressure on minimum film thickness was dependent on groove location. An axial groove located at 90° to the load line gave rise to more favourable bearing performance characteristics.
A comparative study of the methods for calculation of surface elastic deformation
Authors: Wang W-Z , Wang H , Liu Y-C , Hu Y-Z , Zhu D
Published: August 2003

A fundamental issue of lubrication analysis is the calculation of surface deformation, which includes two major steps: determination of influence coefficients and multiplication and summation. There are various interpolation schemes, such as the bilinear interpolation, the piecewise constant function or Green's function, available for determining the influence coefficients, while the summation operation may be performed by using one of the following methods: direct summation (DS), multilevel multi-integration (MLMI) or the discrete convolution and fast Fourier transform (DC-FFT) method. To limit the periodical errors, the proper way to implement the DC-FFT method is described in detail. The computation efficiency and numerical accuracy are compared by applying the different methods to typical contact problems. The results show that the three methods can achieve comparable numerical accuracy, but the DC-FFT method shows much higher computation efficiency than the others, especially when a great number of grid points are involved. It is concluded that the DC-FFT method has great potential in applications to the numerical analysis of, for example, surface deformations and temperature rises.
Thermal effect on the film thickness in high-speed lubricated cold rolling of a strip—an inlet zone analysis
Authors: Ghosh M. K. , Pandey R. K. , Singh P
Published: August 2003

A thermal analysis of hydrodynamic lubrication of high-speed cold rolling of strips in the inlet zone has been made to estimate the film thickness in the contact region. The piezoviscous effect, which would be significant in the case of heavy-duty rolling when a large reduction in the thickness of the strip takes place during the rolling process, has been incorporated using Roelands' viscosity model. The generalized Reynolds equation in the inlet zone has been solved using the finite difference method to determine the pressure distribution. Temperature variations across the film have been expressed using Legendre's polynomial at Lobatto points while solving the energy equation. Temperature variations along the film were determined using the finite difference method by solving the energy equation. The results for the film thickness-temperature profile in the inlet zone have been estimated for high-speed rolling of the strip (up to 50m/s) with and without sliding for heavy reduction in thickness of the strip. Significant reduction in the film thickness due to the thermal effect has been found.
Viscous pumps: Comparative assessment of effectiveness
Authors: Arafa H. A. , Osman T. A.
Published: August 2003

A classification of the different viscous pump embodiments and a survey of the application areas are made. A dimensionless number is newly introduced here, and it is suggested that this be used in evaluating the comparative effectiveness of viscous pumps of different configurations. The effectiveness is evaluated for viscous pumping devices developed over the last four decades and for which sufficient data and experimental test results are available. It is shown that these pumps could be broadly categorized into effective and much less effective types. An enumeration of possible design pitfalls is given for the latter types. The findings of the present paper are deemed useful to design engineers in their endeavour to assess the effectiveness of existing viscous pumps and in developing new ones.
Study of the main variability aspects of surface texture of steel in face milling
Authors: Petropoulos G , Pandazaras C , Stamos I
Published: August 2003

The investigation of basic variability aspects in face-milled surfaces regarding roughness and waviness (surface texture) for various cutting conditions is attempted in this note. The inhomogeneity of the machined steel specimens surfaces is modelled according to the Fisher-Pearson statistical system. Models are developed by regression analysis for waviness and roughness interdependence exhibiting very high correlation coefficients.
Half-frequency whirl of pistons in axial piston pumps and motors under mixed lubrication
Authors: Tanaka K , Nakahara T , Kyogoku K
Published: August 2003

Dynamic lubrication characteristics between a piston and a cylinder in an axial piston pump and motor have been calculated under mixed-lubrication conditions. The calculated results have shown that half-frequency whirling of the piston occurs under some operating conditions and specifications such as low supply pressure, narrow clearance and long sealing length between the piston and the cylinder, in a manner similar to the oil whirl phenomenon in journal bearings. The whirl phenomenon has been confirmed by measurements of piston motion.
Analysis of ignition processes in a fuel spray using an ignition model including turbulent mixing and reduced chemical kinetics
Authors: Ishiyama T , Shioji M , Lhara T
Published: August 2003

In order to clarify the mechanism of fuel spray ignition, an ignition model was developed employing a stochastic turbulent mixing model and a quasi-global chemical kinetics model. Using this model, histories of heterogeneity in temperature and equivalence ratio of fuel/air mixtures were analysed. At low initial ambient temperatures, exothermic reactions begin in lean mixtures with equivalence ratios in a very narrow range. On the other hand, at higher air temperatures, mixtures with a variety of equivalence ratios ignite. This phenomenon can be explained by the dependency of mixture reactivity on the equivalence ratio and temperature. Based on these results, a discussion is given on the similarities and differences in the temperature dependency of ignition delays between sprays and homogeneous mixtures.
Residual-effected homogeneous charge compression ignition at a low compression ratio using exhaust reinduction
Authors: Caton P. A. , Simon A. J. , Gerdes J. C. , Edwards C. F.
Published: August 2003

Studies have been conducted to assess the performance of homogeneous charge compression ignition (HCCI) combustion initiated by exhaust reinduction from the previous engine cycle. Reinduction is achieved using a fully flexible electrohydraulic variable-valve actuation system. In this way, HCCI is implemented at low compression ratio without throttling the intake or exhaust, and without preheating the intake charge. By using late exhaust valve closing and late intake valve opening strategies, steady HCCI combustion was achieved over a range of engine conditions. By varying the timing of both valve events, control can be exerted over both work output (load) and combustion phasing. In comparison with throttled spark ignition (SI) operation on the same engine, HCCI achieved 25–55 per cent of the peak SI indicated work, and did so at uniformly higher thermal efficiency. This was accompanied by a two order of magnitude reduction in NO emissions. In fact, single-digit (ppm) NO emissions were realized under many load conditions. In contrast, hydrocarbon emissions proved to be significantly higher in HCCI combustion under almost all conditions. Varying the equivalence ratio showed a wider equivalence ratio tolerance at low loads for HCCI.
Diesel engine control optimization for transient operation with lean/rich switches
Authors: Kyrtatos N. P. , Tzanos E. I. , Papadopoulos C. I.
Published: August 2003

Transient operation of a direct injection heavy duty (DI HD) diesel engine equipped with an NOx storage catalyst (NSC) was simulated using a ‘virtual powerplant’ simulation code with a zero-dimensional multizone combustion model. For the regeneration of the NSC the engine is required to work with lean/rich operation switches, which necessitates advanced engine management schemes for the fuelling, throttle and turbocharger wastegate. An optimization procedure, using the simulation model, resulted in a proposed schedule for the control of the various engine components involved in such engine operation.
Mass integration of fast-response NO measurements from a two-stroke large-bore natural gas engine
Authors: Puzinauskas P. V. , Olsen D. B. , Willson B. D.
Published: August 2003

A thermodynamic two-stroke-cycle engine simulation with a quasi-steady scavenging model was developed and used to mass-integrate cycle-resolved NO measurements made with a fast-response NO analyser. The engine tested was a Cooper-Bessemer GMV-4TF large-bore natural gas engine and the fast NO measurements were made in cylinders 2 and 4 using a Cambustion fNOx400 two-channel fast-response analyser. The engine simulation was deemed to provide a good representation of the cycle-resolved scavenging mass flow. The mass-integrated NO results were compared to Fourier transform infrared (FTIR) steady measurements taken downstream of the cylinders 2 and 4 exhaust-manifold junction. The correlation between the two techniques was linear to within 2 per cent. A strong correlation was exhibited between mass-integrated cycle-to-cycle NO and measured peak and crank angle location of peak combustion pressure. The correlation with peak pressure was slightly better than the location of peak pressure.
Modelling the early stage of spark ignition engine combustion using the KIVA-3V code incorporating an ignition model
Authors: Andreassi L , Cordiner S , Rocco V
Published: August 2003

The evolution of early stages of homogeneous mixture combustion in spark ignition (SI) engines represents a critical period that greatly affects the whole combustion process. A proper description of this critical phase represents a major issue, which could strongly influence the overall model predictive capability (i.e. model ability to reproduce the real engine behaviour for a large range of operating conditions without any major tuning). Such requirements become even more important for the simulation of last-generation gasoline direct injection or lean stratified engines, where ignition could determine the functionality of the engine itself.

In this paper, after a detailed analysis of the ignition physical process and its modelling issues, the predictive capability of the KIVA-3V code has been improved by substituting the original ignition procedure with a more detailed kernel evolution model based on the one presented by Herweg and Maly in 1992.

The ignition model introduced in a KIVA-3V version already modified by the authors (re-zoning algorithm, combustion and turbulence models, cylinder wall heat transfer, etc.) has then been tested in order to assess its level of accuracy in describing this complex phenomenon, by varying the most critical engine operating conditions and keeping combustion tuning parameters unchanged. After comparing ignition model results with the corresponding ones presented by Herweg and Maly, a specific application of the overall model (KIVA-3V + ignition model + turbulent combustion model) has been made to perform an analysis of a compressed natural gas (CNG) fuelled engine for heavy-duty applications. To this aim, the in-cylinder combustion history and the related processes as the temperature distribution and NOx formation have been calculated and verified with reference to the experimental data measured in a wide range of operating conditions of an IVECO turbocharged engine.
The application of a multicomponent droplet vaporization model to gasoline direct injection engines
Authors: Ra Y , Reitz R. D.
Published: August 2003

A model for unsteady droplet vaporization is presented that considers the droplet temperature range from flash-boiling conditions to normal evaporation. The theory of continuous thermodynamics was used to model the properties and compositions of multicomponent fuels such as gasoline. In order to model the change of evaporation rate from normal to boiling conditions more realistically, an unsteady internal heat flux model and a new model for the determination of the droplet surface temperature are proposed. An explicit form of the equation to determine the heat flux from the surrounding gas mixture to the droplet/gas interface was obtained from an approximate solution of the quasi-steady energy equation for the surrounding gas mixture, with the interdiffusion of fuel vapour and the surrounding gas taken into account. The model was applied to calculate normal and boiling evaporation processes of droplets for various ambient temperatures and droplet temperatures. Single-droplet evaporation calculated using the present model was compared with the results calculated by using the standard evaporation routine of the KIVA-3V code. Also, simulations of the vaporization of a single-component fuel (iso-octane) were compared with multi-component fuel cases. The vaporization of a hollow cone spray of fuel injected into a cylindrical chamber was simulated for both normal and flash-boiling conditions using the KIVA-3V code implemented with the present model. In addition, the model was applied to a realistic gasoline direct injection engine.
A risk-based method for minimizing welding distortion in steel ship production
Authors: Sukovoy O , Kuo C
Published: August 2003

The paper presents a novel approach, entitled responsibility-sharing management (RSM) which can be used to assist in effective management of welding distortion in ship production that takes into account scientific methods, procedures and management issues. The paper begins by outlining the nature of welding distortion, its impact on steel ship production and traditional methods of dealing with it before suggesting the alternative way forwards. The principles of the RSM approach are then explained and the key features of its six elements are examined. An illustrative example is used to demonstrate the effective use of this approach in a shipyard.

The main conclusions are the following. Firstly, since welding distortion has a significant impact on ship production, there is, therefore, a need for a fresh systematic approach for dealing with this problem which could address not only technical aspects but also management, operation and human factors. Secondly, it is essential to encourage the development of a positive culture in the management of ship production and this is particularly relevant in efforts to minimize welding distortion.
Reliable finite element analysis of ship structural components
Authors: Palani G S , Rajasankar J , Iyer N R , Appa Rao T V S R
Published: August 2003

Reliable and accurate determination of the static and dynamic response quantities is of considerable importance for economical and safe design of ship hull structures and offshore platforms. The objective of this paper is to present efficient methodologies that can be employed to obtain reliable finite element solutions for static and dynamic analysis of ship structural components. An a posteriori error estimator and h-adaptive refinement strategy is proposed for static and dynamic analysis of stiffened plate/shell panels. The equal subdivision or bisection method is made use of and local refinements are carried out only in the elements requiring refinements. An adaptive time-stepping scheme is proposed for transient dynamic analysis of stiffened plate/shell panels based on the time error estimates. Numerical studies on the static and dynamic analysis of ship hull structural components have been conducted to demonstrate the performance of the error estimator and the adaptive refinement strategy. It is observed that the proposed adaptive strategy in association with the error estimator is helpful in arriving at optimal mesh and time steps for the specified accuracy. It is recommended that the proposed methodologies can be used in obtaining reliable finite element solutions for design of ship structural components subjected to static and dynamic loads.
Drug Therapy for Prevention of Recurrent Myocardial Infarction
Authors: van der Elst Menno E , Buurma Henk , Bouvy Marcel L , de Boer Anthonius
Published: August 2003

OBJECTIVE

To provide an evidence-based overview of drug treatment for long-term secondary prevention of myocardial infarction (MI).

DATA SOURCES

We conducted searches of MEDLINE (1966–August 2002), the Cochrane Controlled Trial Register, and the reference list of each identified study.

STUDY SELECTION/DATA EXTRACTION

Trials and meta-analyses were included using the following criteria: (1) randomized trials, (2) description of identification procedure, inclusion criteria, outcome measures, and statistical methods, (3) confirmed MIs, (4) treatment continued for at least 1 month, and (5) all-cause mortality as primary outcome; other events as secondary outcomes. All authors interpreted the results from trials that met the inclusion criteria.

DATA SYNTHESIS

In randomized clinical trials, low-dose aspirin, high-intensity oral anticoagulants, β-blockers, angiotensin-converting enzyme (ACE) inhibitors, and statins decreased the risk of mortality and reinfarction after MI. Randomized clinical trials using calcium-channel blockers, antiarrhythmics, and hormone replacement therapy did not show benefits in patients with prior MI. Effects of the combined use of aspirin or oral anticoagulants with β-blockers or ACE inhibitors plus statins must be derived from subgroup analysis of trials, but seem to be beneficial.

CONCLUSIONS

The use of at least aspirin or an oral anticoagulant, a β-blocker or an ACE inhibitor, plus a statin should be incorporated in the treatment routine. Clopidogrel treatment might be an alternative to aspirin. Standard addition of a β-blocker to ACE inhibitor–treated patients without reduced left-ventricular ejection fraction seems to be untimely.
Enfuvirtide: A Novel Agent for the Treatment of HIV-1 Infection
Authors: Duffalo Melody L , James Christopher W
Published: August 2003

Objective

To review the pharmacology, virology, pharmacokinetics, efficacy, safety, and clinical use of enfuvirtide.

Data Sources

English-language MEDLINE and AIDSline searches were performed (1966–January 2003) using enfuvirtide, T-20, gp41, and fusion inhibitors as key words. Abstracts from infectious diseases and HIV scientific meetings were identified.

Data Extraction

All publications and meeting abstracts were reviewed and relevant items included. In vitro and preclinical studies were included, as well as Phase II and III clinical trials.

Data Synthesis

Enfuvirtide is a fusion inhibitor used for the treatment of HIV-1 infection. Given its unique mechanism of action, most HIV-1 isolates are susceptible to enfuvirtide. Enfuvirtide is administered by subcutaneous injection twice daily. In clinical trials with antiretroviral-experienced patients, enfuvirtide was effective at suppressing HIV-RNA and increasing CD4+ T-cell counts. Enfuvirtide should be used in combination with other active antiretroviral agents to optimize its efficacy and limit resistance. Injection site reactions associated with administration of the drug are experienced in the majority of patients. Availability of enfuvirtide may be limited by a complex manufacturing procedure.

Conclusions

Enfuvirtide is an effective treatment option for HIV-1–infected individuals when used in combination with other antiretroviral agents. It may be used as part of a regimen for treatment-experienced patients.
Student attitudes towards socially acceptable and unacceptable group working practices
Authors: Underwood Jean D. M.
Published: August 2003

While there is much support for co‐operative learning among learning theorists, not all learners exhibit the same enthusiasm for groupwork. A number of factors such as sex, group size and ability mix, subject domain, task type and organization have been shown to influence the effectiveness of co‐operative and collaborative learning. This study established learners' attitudes to various shared working scenarios. In this mixed design, 140 post‐graduate teacher trainees were asked to imagine their responses to seven groupwork scenarios presented as a series of short vignettes. The vignettes varied on the degree of co‐operation required; the sex of the prospective co‐worker(s) including single and mixed‐sex groups; type of assessment, including no assessment at all; and on academically acceptable and unacceptable ‘shared’ working practices. Anticipated attitudinal and behavioural responses of the students were assessed by questionnaire. On the whole, students were cautiously willing to be involved in groupwork. There were caveats, however. Factors such as the characteristics of the group members, the level and type of assessment procedures in operation, and individual differences, including sex and self‐reported social deviance, also governed their responses. There was very limited agreement to be involved in socially undesirable collaborative group activities at a personal level or to condone such activities by others. Those students who showed a tendency towards mild anti‐social behaviour were more willing to take direct punitive action against non‐contributors than their peers. Female students were more willing to invoke the help of the tutor than their male counterparts, but only if the anti‐social behaviour impacted on them personally.
Exposure duration: Effects on eyewitness accuracy and confidence
Authors: Memon Amina , Hope Lorraine , Bull Ray
Published: August 2003

The current study examined the relationship between the length of exposure to a face in an eyewitness setting and identification accuracy and confidence. A sample of 164 young (ages 17–25) and older (ages 59–81) adults viewed a simulated crime in which they saw the culprit's face for a short (12 s) or long (45 s) duration. They were then tested with a target absent (a line‐up not containing the culprit) or target present line‐up. Identification accuracy rates for both young and older participants were significantly higher under the long exposure condition. In the short exposure condition, witnesses who had made a correct identification of the target were more confident than incorrect witnesses. In the long exposure condition the confidence ratings of accurate and inaccurate witnesses did not differ. Discussion focuses on the extent to which extended exposure may inflate confidence judgments and variables that may moderate the relationship between exposure duration and face recognition accuracy.
Sequence learning by action and observation: Evidence for separate mechanisms
Authors: Kelly S. W. , Burton A. M. , Riedel B. , Lynch E.
Published: August 2003

In the Serial Reaction Time (SRT) task, participants respond to a set of stimuli the order of which is apparently random, but which consists of repeating sub‐sequences. Participants can become sensitive to this regularity, as measured by an indirect test of reaction time, but can remain apparently unaware of the sequence, as measured by direct tests of prediction or recognition. Some researchers have claimed that this learning may take place by observation alone. We suggest that observational learning may be due to explicit acquired knowledge of the sequence, and is not mediated by the same processes which give rise to learning by action. In Expt 1, we show that it is very difficult to acquire explicit sequence knowledge under dual task conditions, even when participants are told that a regular sequence exists. In Expt 2, we use the same conditions to compare actors, who respond to the sequence during learning, and observers, who merely watch the stimuli. Furthermore, we manipulate the salience of the sequence, in order to encourage learning. There is no evidence of observational learning in these conditions, despite the usual effects of learning being demonstrated by actors. In Expt 3, we show that observational learning does occur, but only when observers have no secondary task and even then only reliably for a sequence which has been made salient by chunking subcomponents. We conclude that sequence learning by observation is mediated by explicit processes, and is eliminated under conditions which support learning by action, but make it difficult to acquire explicit knowledge.
The influence of a salience distinction between bilateral cues on the latency of target‐detection saccades
Authors: Kean Matthew , Lambert Anthony
Published: August 2003

The spatial cueing paradigm, with saccades to targets as the method of response, was used to investigate the influence of two simultaneously presented cues on the orienting of visual attention. Participants were presented with bilateral cues, one of which was perceptually salient (high luminance) relative to the other. They participated in one of three conditions: in the ‘bright side likely’ condition targets usually (p = .8) appeared near the more salient cue; in the ‘dim side likely’ condition targets usually (p = .8) appeared near the less salient cue; and in the ‘neutral’ condition the arrangement of the cues was uninformative with respect to target location. Brief SOAs (0, 50, 100 and 150 ms) were employed. Rapid reflexive orienting to the more salient stimulus was observed in the neutral condition: saccadic latencies were faster when the target appeared near the bright cue, and this was found even across the two shortest SOAs. However, this reflexive orienting was suppressed in both the bright side likely and dim side likely conditions: the advantage observed at the bright cue's location across the two shortest SOAs in the neutral condition was significantly attenuated in the two contingent conditions. Results point to rapid expectancy‐based interference in the reflexive process of attention capture.
Selective interest and psychological practice: A new interpretation of the Burt affair
Authors: Joynson R. B.
Published: August 2003

Anomalies in Burt's twin data have precipitated a prolonged and inconclusive controversy between those who accuse him of fabrication and those who defend his integrity. Here it is suggested that the argument arose in part because differing personal, and especially political, interests predisposed psychologists to diverse interpretations of the evidence. ‘Selective interest’ (James, 1890) leads to a concentration of attention on partial data. The participants in the controversy readily detected this fault in their opponents, but rarely in themselves. It is then suggested that this same factor accounts for the deficiencies in Burt's kinship data. His research was especially vulnerable to ‘selective interest’, and the numerical anomalies in his reports are consistent with this interpretation. It is questioned whether scientific techniques can ever wholly replace personal judgment, with its potential for selective bias.
Building Quantum Dots into Solids with Well‐Defined Shapes
Authors: Mao C. , Qi J. , Belcher A.M.
Published: August 2003

Quantum dots (QDs) chemically synthesized in solution at a higher temperature (85 °C) were built in situ into a variety of three‐dimensional (3D) close‐packed QD ensembles (QD solids) with well‐defined shapes: needles, disks, rods, spheres, bundles, stars, ribbons, and transition structures (TSs). Design strategies using a novel cold‐treatment (–25 to 0 °C) process immediately following the synthesis of the QDs provided control over these shapes, independently from the II–VI materials used. Transformation occurred between different shapes by the rearrangement of the QDs within the QD ensembles. The QD solids were characterized by advanced electron microscopy and photoluminescence spectroscopy. The cold treatment strategy is versatile and has been applied to several II–VI QDs (CdS, ZnS, and CdSe) and may be extended to other QD systems and other chemical approaches.
Improved Efficiency of Single‐Layer Polymer Light‐Emitting Devices with Poly(vinylcarbazole) Doubly Doped with Phosphorescent and Fluorescent Dyes as the Emitting Layer
Authors: Kan S. , Liu X. , Shen F. , Zhang J. , Ma Y. , Zhang G. , Wang Y. , Shen J.
Published: August 2003

We demonstrate novel organic light‐emitting diode (LED) materials that contain a green phosphorescent dye (dmbpy)Re(CO)3Cl (dmbpy = 4,4′‐dimethyl‐2,2′‐bipyridine), and a red fluorescent dye 4‐dicyanomethylene‐6‐(p‐dimethylaminostyryl)‐2‐methyl‐4H‐pyran (DCM) as dopants and polyvinylcarbazole (PVK) as the host. The photoluminescence (PL) and electroluminescence (EL) properties of these complex materials were studied. The energy transfer efficiency from PVK host to DCM is increased by the (dmbpy)Re(CO)3Cl co‐dopant, which has an emission energy between that of PVK and DCM. The (dmbpy)Re(CO)3Cl, which emits a long‐lived phosphorescence, is used as an energy coupler, providing the possibility to harvest both singlet and triplet energy in the devices. The pure red emission from DCM was observed from PL and EL spectra of (dmbpy)Re(CO)3‐Cl(> 2.0 wt.‐%):DCM(> 0.5 wt. %) doped PVK films, demonstrating an efficient energy transfer from PVK and (dmbpy)Re(CO)3‐Cl to DCM. By optimizing the concentration of DCM and (dmbpy)Re(CO)3Cl in PVK, a maximum EL quantum efficiency of 0.42 cd A–1 at a current density of 9.5 mA cm–2 was obtained. The EL quantum efficiency of the doubly doped device is significantly enhanced in comparison with both a DCM‐only doped PVK device and a DCM‐doped PVK device with the green fluorescent dye Alq3 as co‐dopant. The improvement in the operating characteristics of the phosphorescent and fluorescent dye doubly doped device is attributed to efficient energy transfer in the system, in which both triplet and singlet excitons are used for resultant emission in the polymer device.