bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxidant-induced cell death in retinal pigment epithelium cells mediated through the release of apoptosis-inducing factor
Authors: Zhang Congxiao , Baffi Judit , Cousins Scott W. , Csaky Karl G.
Published: April 2003

In the present study, the pathways involved in oxidant-induced cell death of a primary cell of the retina, ARPE-19, were investigated and compared with a leukemic cell, U937 cells. Both ARPE-19 and U937 cells exhibited similar viability when exposed to menadione. At lethal doses, both cell lines demonstrated extensive membrane blebbing. However, although U937 cells exhibited caspase-3, -9 PARP cleavage and 200 bp laddering, no such cleavage or laddering was noted in ARPE-19 cells. Furthermore, addition of exogenous cytochrome c and ATP to a cell-free system again resulted in cleavage of caspase-3 and -9 in extracts of U937 but not ARPE cells. Further studies in ARPE-19 cells undergoing menadione-induced cell death demonstrated mitochondrial membrane depolarization, release of cytochrome c, nuclear translocation of apoptosis-inducing factor and subsequent 50 kilo-base pair laddering, and nuclear shrinkage. All of these findings were abrogated by the pretreatment of ARPE-19 cells with hepatocyte growth factor/scatter factor. These findings demonstrate the complex nature of cell death in primary cells of the retina and highlight the role of caspase-independent signals, growth factors and intracellular survival factors in programmed cell death pathways.
Anti-membrane-bound transferrin-like protein antibodies induce cell-shape change and chondrocyte differentiation in the presence or absence of concanavalin A
Authors: Oda Ryo , Suardita Ketut , Fujimoto Katsumi , Pan Haiou , Yan Weiqun , Shimazu Atsushi , Shintani Hideaki , Kato Yukio
Published: April 2003

Membrane-bound transferrin-like protein (MTf), a glycosylphosphatidylinositol-anchored protein, is expressed at high levels in many tumors and in several fetal and adult tissues including cartilage and the intestine, as well as in the amyloid plaques of Alzheimer's disease, although its role remains unknown. MTf is one of the major concanavalin A-binding proteins of the cell surface. In this study, we examined the effects of anti-MTf antibodies and concanavalin A on cell shape and gene expression,using cultures of chondrocytes and MTf-overexpressing ATDC5 and C3H10T1/2 cells. In cultures expressing MTf at high levels, concanavalin A induced cell-shape changes from fibroblastic to spherical cells, whereas no cell-shape changes were observed with wild-type ATDC5 or C3H10T1/2 cells expressing MTf at very low levels. The cell-shape changes were associated with enhanced proteoglycan synthesis and expression of cartilage-characteristic genes,including aggrecan and type II collagen. Some anti-MTf antibodies mimicked this action of concanavalin A, whereas other antibodies blocked the lectin action. The findings suggest that the crosslinking of MTf changes the cell shape and induces chondrogenic differentiation. MTf represents the first identification of a plant lectin receptor involved in cell-shape changes and the differentiation of animal cells.
Cajal body proteins SMN and Coilin show differential dynamic behaviour in vivo
Authors: Sleeman Judith E. , Trinkle-Mulcahy Laura , Prescott Alan R. , Ogg Stephen C. , Lamond Angus I.
Published: April 2003

Analysis of stable cell lines expressing fluorescently tagged survival of motor neurons protein (SMN) and coilin shows striking differences in their dynamic behaviour, both in the nucleus and during mitosis. Cajal bodies labelled with either FP-SMN or FP-coilin show similar behaviour and frequency of movements. However, fluorescence recovery after photobleaching (FRAP)studies show that SMN returns ∼50-fold more slowly to Cajal bodies than does coilin. Time-lapse studies on cells progressing from prophase through to G1 show further differences between SMN and coilin, both in their localisation in telophase and in the timing of their re-entry into daughter nuclei. The data reveal similarities between Cajal bodies and nucleoli in their behaviour during mitosis. This in vivo study indicates that SMN and coilin interact differentially with Cajal bodies and reveals parallels in the pathway for reassembly of nucleoli and Cajal bodies following mitosis.
A hydrophilic lamin-binding domain from theDrosophilaYA protein can target proteins to the nuclear envelope
Authors: Mani Shobana S. , Rajagopal Rithwick , Garfinkel Amanda B. , Fan Xiaochun , Wolfner Mariana F.
Published: April 2003

The nuclear lamina provides an architectural framework for the nuclear envelope and an attachment site for interphase chromatin. In Drosophila eggs and early embryos its major constituent, lamin Dm0, interacts with a lamina protein called YA. When the lamin-interaction region of YA is deleted, YA still enters nuclei but fails to localize to nuclear envelopes, suggesting that lamin interaction targets YA to the nuclear envelope. Here, we show that C-terminal lamin-interacting region of YA is sufficient to target the heterologous soluble protein GFP-NLS to the nuclear periphery in Drosophila tissue culture cells. Yeast two-hybrid analysis and transient transfection assays further defined this domain: residues 556-696 of YA are sufficient for both lamin Dm0interaction and the targeting of GFP-NLS to the nuclear periphery. This region of YA is hydrophilic and lacks any transmembrane domain or known membrane-targeting motifs. We propose that the localization of YA to the nuclear lamina involves interaction with polymerized lamin Dm0mediated by the lamin-targeting domain of YA. This hydrophilic YA domain might provide a useful molecular tool for targeting heterologous non-membrane-associated proteins to the nuclear envelope.
Protein phosphatase 4 interacts with the Survival of Motor Neurons complex and enhances the temporal localisation of snRNPs
Authors: Carnegie Graeme K. , Sleeman Judith E. , Morrice Nick , Hastie C. James , Peggie Mark W. , Philp Amanda , Lamond Angus I. , Cohen Patricia T. W.
Published: April 2003

Protein phosphatase 4 (PPP4) is a ubiquitous essential protein serine/threonine phosphatase found in higher eukaryotes. Coordinate variation of the levels of the catalytic subunit (PPP4c) and the regulatory subunit (R2)suggests that PPP4c and R2 form a heterodimeric core to which other regulatory subunits bind. Two proteins that specifically co-purify with Flag-epitope-tagged R2 expressed in HEK-293 cells were identified as Gemin3 and Gemin4. These two proteins have been identified previously as components of the Survival of Motor Neurons (SMN) protein complex, which is functionally defective in the hereditary disorder spinal muscular atrophy. Immuno-sedimentation of the epitope-tagged SMN protein complex from HeLa cells expressing CFP-SMN showed that the SMN protein interacts, as previously reported, with Gemin2 (SIP1), Gemin3 and Gemin4 and in addition associates with PPP4c. The SMN complex has been implicated in the assembly and maturation of small nuclear ribonucleoproteins (snRNPs). Expression of GFP-R2–PPP4c in HeLa cells enhances the temporal localisation of newly formed snRNPs, which is consistent with an association of R2-PPP4c with the SMN protein complex.
Role for NudC, a dynein-associated nuclear movement protein, in mitosis and cytokinesis
Authors: Aumais Jonathan P. , Williams Shelli N. , Luo Weiping , Nishino Michiya , Caldwell Kim A. , Caldwell Guy A. , Lin Sue-Hwa , Yu-Lee Li-yuan
Published: April 2003

NudC, a nuclear movement protein that associates with dynein, was originally cloned as a mitogen-inducible early growth response gene. NudC forms a biochemical complex with components of the dynein/dynactin complex and is suggested to play a role in translocation of nuclei in proliferating neuronal progenitors as well as in migrating neurons in culture. Here, we show that NudC plays multiple roles in mitosis and cytokinesis in cultured mammalian cells. Altering NudC levels by either small interfering RNA-mediated gene silencing or adenovirus-mediated overexpression resulted in multinucleated cells and cells with persistent intercellular connections and disorganized midzone and midbody matrix. These phenotypes suggest a failure in cytokinesis in NudC altered cells. Further, a key mitotic enzyme, polo-like kinase, is mislocalized from the centrosomes and the midbody in NudC altered cells. Gene silencing of nud-1, the Caenorhabditis elegansortholog of NudC, led to a loss of midzone microtubules and the rapid regression of the cleavage furrow, which resulted in one-celled embryos containing two nuclei. The loss of midzone microtubule organization owing to silencing of the NudC/nud-1 gene in two systems, coupled with the loss of Plk1 from mitotic structures in mammalian cells, provide clues to the cytokinesis defect and the multinucleation phenotype. Our findings suggest that NudC functions in mitosis and cytokinesis, in part by regulating microtubule organization at the midzone and midbody.
Study on the life distribution of microdrills
Authors: Yang Z , Chen Y , Yang Y
Published: April 2003

In this paper, the life distribution of microdrills has been studied experimentally. The fit and test methods of the life distribution function of microdrills are described. Under the experimental conditions of the present work, it is concluded that the life of microdrills follows the log-normal distribution and the distribution parameters are different for various workpiece materials. The life distribution function and reliability function of microdrills from the present work provide a base for correct changing of drills in automatic machining processes.
A product data management integrated product configuration and assembly process planning environment
Authors: Gao J X , Bowland N W
Published: April 2003

This paper reports part of the results of a 3 year project carried out at Cranfield University in collaboration with companies in the automotive and aerospace industry, aiming to develop new methodologies for computer aided assembly process planning (CAAPP). CAAPP is not a mature technology, despite the managerial and technical advantages offered by its implementation. This paper describes the limiting factors in industrial acceptance of CAAPP and discusses methodologies by which these factors can be eliminated. This is done primarily by the integration of CAAPP functionality with a product data management (PDM) tool, providing a data control framework and a high-level data structure to form the basis of planning. The paper also details a system based on the described approach. The underlying object-oriented model developed to facilitate automated assembly process planning is described in detail. Data control methodologies are presented to aid retrieval, storage and creation. Methods for the definition of liaisons, mating features, are discussed. The methodologies used for constraint identification, process sequence generation and sequence representation within the system are described. Multiple sequences are represented by means of a tree structure, similar to the AND/OR graph representation. The sequence is navigable and can be used for downstream sequence evaluation and simulation or to generate scheduling data.
Obtaining an optimal compression spring design directly from a user specification
Authors: Paredes M , Sartor M , Masclet C
Published: April 2003

Common mechanical components can be designed manually but this involves problem simplifications. A computer can help to develop a suitable approach for optimizing design. Industrial software for spring design is comprehensive tools for validation only. To improve design assistance to the designer, this paper presents software which not only is comprehensive but also can serve as a dimensional synthesis tool for compression spring design. It exploits an optimization process for use even in the early design steps as specifications are set with interval values. It includes a large set of constraints which can express not only the designer specifications but also the standards and the technical capability limits of spring manufacturers. This process has been successfully tested by a spring manufacturer, who has used it to solve real industrial problems for 2 years. One case study is presented.
A genetic algorithm-based parameter-tuning algorithm for multi-dimensional motion control of a computer numerical control machine tool
Authors: Kuo L-Y , Yen J-Y
Published: April 2003

This paper addresses an automatic parameter-tuning algorithm for the multi-axis motion control of a computer numerical control (CNC) machine centre. The traditional approach to tune the control parameters in the multi-axis machines is to tune each axis independently. Some high-end-precision machines offer cross-axis motion parameters for impedance compensation but this is usually not satisfactory for practical purpose. Because each axis on the machine centre contributes to more than one working plane, obtaining the optimal performance for motions involving more than one plane often results in axis coupling. This paper introduces a systematic method to tune the servo parameters for multi-axis motion control. The tuning algorithm is based upon an intelligent genetic algorithm (GA) and the parameters are tuned for each work plane. The method optimized the multi-axis motion performance. A modified GA is also proposed to solve the convergence problem induced by a large number of parameters in multi-axis motion tuning.
Automated segmentation of point data in a feature-based reverse engineering system
Authors: Park S , Jun Y
Published: April 2003

This paper proposes a novel methodology for robust segmentation of scanned point data that has been implemented in the feature-based reverse engineering system (FBRES). In the proposed method, firstly triangle meshes are generated from the input point data. The normal and the area of generated meshes are checked to find boundary meshes using the angle deviation criterion and the area criterion based upon a region-growing technique. Boundary meshes of each segmented region are connected into loops. Then, the meshes closed by each boundary loop are segmented into a single distinctive region. Finally, all segmented regions are mapped into a single feature using an artificial neural network (ANN) based feature recognizer. The FBRES is currently dedicated for reconstructing prismatic features such as a block, pocket, step, slot, hole and boss, which are very common and crucial in mechanical engineering products. The effectiveness of the proposed segmentation method is validated with experimental results.
Collaborative development using EMProDS: The electromechanical product design system
Authors: Farr R , Gayretli A , Speller H , Gindy N
Published: April 2003

Among manufactured products, electromechanical devices are something of a special case, requiring input at the earliest design stage of experts from two (or more) distinctly separate branches of engineering. This tends to promote a modular approach under which products are partitioned by function, with each module being either purely electrical or purely mechanical. However, customers' demands for smaller lighter, less expensive items with greater functionality force manufacturers to produce integrated systems. Furthermore, modules which function optimally in isolation may not produce an optimal assembly.

This paper describes an alternative approach to the conceptual design of electromechanical products, in which a software tool promotes the communication of ideas and opinions. EMProDS provides an easy-to-use distributed design environment, meant to preserve as far as possible the intent of the design team—an aspect of design which can easily be lost once detailed computer aided design drawings are made. This makes any redesign activity which is required simpler and eliminates a common source of conflict between specialists with different technical backgrounds.
Three-dimensional extension of Bresenham's algorithm and its application in straight-line interpolation
Authors: Liu X-W , Cheng K
Published: April 2003

Conventional straight-line generating algorithms, such as the digital differential analyser (DDA), Bresenham's algorithm and the mid-point algorithm, are suitable only for planer straight lines on the coordinate planes, of which Bresenham's algorithm is the most efficient. In this paper, the authors have extended Bresenham's algorithm to spatial straight lines. Given a spatial straight-line segment with two end-points, the authors have applied Bresenham's algorithm to the projections of the line segment on two of the three coordinate planes, which is determined by the largest of the coordinate lengths of the line segment, thereby obtaining a three-dimensional extension of the algorithm. In a case study, the authors calculated the distance between each sample position and the given line segment. The result reveals that the actual error at each sample position is smaller than the maximum theoretical error, and the performance of the three-dimensional extension of Bresenham's algorithm is as good as that of Bresenham's original planer algorithm. One of its potential applications is the three-dimensional step straight-line interpolation used in computer numerical control (CNC) systems of machine tools and rapid prototyping machines. Application of the algorithm is contrasted with that of the traditional DDA step straight-line interpolation algorithm. The result confirms that the three-dimensional extension of Bresenham's algorithm is much better than the DDA straight-line interpolation algorithm.
Statistical modelling of laser percussion drilling for hole taper and circularity control
Authors: Ghoreishi M , Low D K Y , Li L
Published: April 2003

The aim of the present work is to investigate the effects of different variables and their interactions in laser percussion drilling and to understand the possibility of controlling simultaneously the two important characteristics of a laser drilled hole: taper and circularity. Six variables, namely the peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position, were selected as independent controllable factors. The response surface method was used to statistically analyse the process. For each variable, five levels were considered and the experiments were performed based on a central composite design. A fibre-optic delivered neodymium-doped yttrium aluminium garnet laser was used to laser percussion drill mild steel sheets with a thickness of 2.5mm. The entrance diameter, the taper and the ratio of maximum to minimum Feret diameter for the hole entrance (circularity) were considered as responses/outputs in order to evaluate the process performance in terms of hole taper and circularity. Statistical modelling was carried out to develop mathematical models to relate the responses (outputs) to the six independent variables through multiple regression. A complete analysis of variance (ANOVA) was performed to test the significance of the obtained coefficients at 1, 5 and 7 per cent levels of significance. The developed models were verified by experiments. The work has shown that the pulse width and peak power have significant effects on the hole diameter, hole taper and hole circularity. However, the pulse frequency has no effect on these three hole characteristics. The number of pulses has no significant effect on hole diameter and circularity but has a significant effect on hole taper.
Low-frequency modulation-assisted drilling using linear drives
Authors: Chhabra P N , Ackroyd B , Compton W D , Chandrasekar S
Published: April 2003

A new machine tool based on linear drive technology has been developed for low-frequency modulation-assisted drilling. The linear drive utilizes a novel design for generating continuous drill feed motion with a superimposed low-frequency modulation of up to 400 Hz without the use of secondary actuators. The frequency characteristics of the drive are such that a wide variety of drilling conditions can be systematically explored. Results pertaining to torque, thrust and controlled chip breakage when drilling ductile aluminium alloys are presented to demonstrate the attractive features of modulation-assisted drilling using linear drives. It has been shown that the application of a superimposed modulation of the appropriate frequency and amplitude produces consistent chip breakage, thereby facilitating the drilling process. Furthermore, under these conditions, the mean torque and mean thrust are decreased in comparison with conventional drilling. The frequency and amplitude conditions for which such beneficial effects are observed can be predicted using a simple model for chip formation and forces in modulation-assisted drilling.
Multi-dimensional transient heat conduction in heat exchanger tubesheets
Authors: Al-Mulhim K , Said S A M , Yilbas B , Habib M A , AlBagawi J
Published: April 2003

Experimental and numerical investigations were carried out to study the effect of weld parameters on the temperature-time history at the back of a tubesheet (adjacent to the gasket) of a shell-and-tube heat exchanger. Experiments were conducted to validate one of the cases simulated (second case in Table 1). The simulated case is called the base case. The predictions obtained for the base case agree well with experimental results. Moreover, parametric studies based on numerical results are carried out for different weld parameters. These parameters include weld duration, weld temperature, tube-sheet size, tubesheet material and sequence of welding. The results indicate that the weld duration has a significant effect on the magnitude of the maximum temperature at the back surface of the tubesheet adjacent to the gasket. Doubling the weld duration increases the maximum temperature by more than 40 per cent. An increase of more than 20 per cent in the peak value of temperature at the back of the tubesheet near the gasket is predicted for five consecutive welds with a time gap of 10 s, whereas a 7.4 per cent increase is predicted for alternate welds.
The effect of coatings on the cutting process, friction, forces and predictive cutting models in machining operations
Authors: Armarego E J A , Verezub S , Samaranayake P
Published: April 2003

The effects of the popular TiN and TiCN coatings on the cutting process, friction and predictive mechanics of cutting models for forces and power in machining operations are investigated. Extensive orthogonal cutting and turning tests on steel work materials have shown that the cutting process and predictive force models are not qualitatively affected by these coatings. Quantitatively, both coatings are equally effective in reducing the friction, forces and power in orthogonal cutting when applied to high-speed steel (HSS) tools and equally ineffective when applied to carbide tools. Both TiN and TiCN coatings applied to HSS tools resulted in modest reductions in the power force component and power of 12–30 per cent ‘on average’ with larger reductions in the thrust force component of about 50 per cent ‘on average’. Considerably more research seems necessary to understand better and to predict quantitatively the effects of the many coating-substrate combinations on the technological performance of machining operations, essential for optimizing the economic performance of these operations.
Burn threshold of high-carbon steel in high-efficiency deep grinding
Authors: Jin T , Stephenson D J , Corbett J
Published: April 2003

The burn-threshold of high-carbon steel (51CrV4) in the high-efficiency deep-grinding (HEDG) process is investigated. It is found that the burn threshold in HEDG is determined by the wheel-workpiece contact length, material removal rate and wheel speed. A theoretical expression for the burn threshold has been derived, which is based on the thermal modelling for deep grinding and takes account of the grinding parameters, wheel conditions, thermal properties of the workpiece and abrasive grain, and the heat convected away by the coolant and chips. The predicted upper and lower boundaries for occurrence of workpiece burn show good agreements with the experimental observations. It is shown that burn threshold in HEDG is related to the film boiling of process coolant and the critical heat flux increases as the specific material removal rate increases. The experiments were carried out on an Edgetek five-axis computer numerical control (CNC) grinding machine, which is capable of HEDG in a relatively wide range of process parameters.
Pass schedule design system in the dry wire-drawing process of high carbon steel
Authors: Jo H H , Lee S K , Kim M A , Kim B M
Published: April 2003

Recently, high-speed drawing has become very common because of the increase in customer demands and production rate in real industrial fields. In the high-carbon steel wire-drawing process, the wire temperature rises greatly according to the increase in the final drawing speed. The rapid temperature rise makes the wire more embrittled and finally leads to wire breakage. Therefore, in this paper, an approximate wire temperature estimation method is proposed to control the maximum temperature rise in the wire-drawing process. Using these results, it is possible to develop the isothermal pass schedule programme, to design the wire-drawing process. Also, the conventional pass schedule can be redesigned by considering the pass schedule constraints. As a result, the wire temperature was considerably reduced and the productivity of the final product could be improved by about 11 per cent.
Current research in the engineering design requirement
Authors: Darlington M J , Culley S J
Published: April 2003

The design requirement is a description of the desired solution to a problem. In engineering design, as in all other, a clear expression of a well-formulated design goal is vital for successful and efficient completion of the design task. The nature of the design requirement and the processes by which it is achieved have been the subject of a wide variety of research. The purpose of the paper is twofold. Firstly, it sets out to collate and discuss representative research in this area in order to give an overview of the current scope of the work. Secondly, it seeks to draw a comparison with the task of developing the design requirement for software and information systems and to initiate a discussion that considers to what extent the substantial body of research in software requirements engineering might help to give an understanding of the design requirement for the engineering design domain. A tentative characterization of the differences between the tasks in the two domains is presented, and representative papers from requirements engineering are used to suggest areas of overlap as a starting point for further investigation.
Functional and behavioural modelling for dependability in automated production systems
Authors: Dangoumau N , Toguyeni A K A , Craye E
Published: April 2003

Within the exploitation of the automated production systems (APS) framework, supervision and monitoring take the dependability into account. In order to reach these objectives, a method is being developed at the Laboratoire d'Automatique et d'Informatique Industrielle de Lille in a supervision and monitoring framework. The main functions are detection, diagnosis, modes management and faults recovery. This paper focuses on two kinds of modelling: functional modelling and behavioural modelling. On the one hand, these models are used to implement the diagnosis and the modes management functions. On the other hand, the complementarity of these models enables them to be used within the alarm processing system framework. Indeed, the design of intelligent alarm processing systems (IAPS) is a critical problem. One common problem is the number of alarms that operators have to manage. This paper focuses on the problem of the management of avalanches of alarms after the occurrence of failures in a complex process. To deal with this problem, different types of alarm are defined from the functional and behavioural modelling of the process to be surveyed. Filtering rules, based on the concepts of validation and inhibition, are also proposed.
Local fuel concentration, ignition and combustion in a stratified charge spark combustion in a stratified charge spark ignited direct injection engine: Spectroscopic, imaging and pressure-based measurements
Authors: Fansler T. D. , Drake M. C. , Stojkovic B , Rosalik M. E.
Published: April 2003

A recently developed spark emission spec-troscopy technique has been used to measure the effects of fuel injection timing, spark timing and intake swirl level on the individual-cycle fuel concentration at the spark gap in a wall-guided spark ignited direct injection (SIDI) engine. The fuel-concentration measurements were made simultaneously with measurements of individual-cycle spark discharge energy and cylinder pressure. Endoscopic imaging of the fuel spray and high-speed imaging of combustion (both broadband and spectrally resolved) augment these quantitative data. For optimum engine operation, the fuel-air equivalence ratio at the spark gap just after spark breakdown is rich on average (〈φ〉 ≈1.4–1.5) and varies widely from cycle to cycle (∼25 per cent). The evolution with crank angle of the mean equivalence ratio and its cycle-to-cycle fluctuations are correlated with the cylinder pressure, heat release and imaging data to provide insights into fuel transport and mixture preparation that are important to understanding and optimizing ignition and combustion in SIDI engines. For example, causes of misfires and partial burns have been determined.
A Calculation method for indicated mean effective pressure based on harmonic analysis of pressure waveform
Authors: Tsuchiya K , Nagashima K
Published: April 2003

A new method for calculating indicated mean effective pressure (i.m.e.p.) was derived from harmonic analysis of pressure waveform in working space, instead of conventional numerical integration of the pressure-volume (P-V) diagram. The method is applicable to a number of displacement-type machines including engines. This paper first introduces a generalized i.m.e.p. equation, then derives the specific i.m.e.p. equations for various mechanisms such as the piston-crank, swash plate, etc. The proposed i.m.e.p. equations introduced show that i.m.e.p. is determined by very low frequency components, of less than several hundred Hz, included in the pressure waveform. The reason is that the amplitude of volumetric variation becomes rapidly smaller as the order of its harmonics increases. This means that the i.m.e.p. equations proposed are more accurate where the number n of sam-pling pressure data per cycle is decreased and allow highspeed calculation as compared with the conventional method. The error of the i.m.e.p. equation for internal combustion engines with a piston-crank driving mechanism is less than ±0.1 per cent. For a Stirling engine with a Ross yoke drving mechanism the erros is less than 0.4 per cent, even if n is decreased until four per cycle because the pressure waveform is close or similar to the sinusoidal wave. The digital i.m.e.p. meter developed as an application of the i.m.e.p. equation is also described, and its validation is discussed.
Laser Doppler velocimetry measurements of flow within the cylinder of a motored tow-stroke cycle engine-comparison with some computational fluid dynamics predictions
Authors: Creaven J. P. , Fleck R , Kenny R. G. , Cunningham G
Published: April 2003

This study was carried out to assess the ability of a computational fluid dynamics (CFD) code to predict the scavenging flow in the cylinder of a two-stroke cycle engine. Predictions were obtained from a CFD simulation of the flow within the cylinder. Due to the apparent sym-metry of the engine port layout, only half of the cylinder volume was modelled. Boundary conditions for the CFD model were obtained from experimentally measured pressure-time histories in the crankcase and exhaust. The two-stroke cycle engine was modified to allow laser Doppler velocimetry (LDV) measurements to be made of the in-cylinder flow. The engine was operated under motoring conditions at 500 r/min with a delivery ratio of 0.7. Although the engine scavenge port layout was geometrically symmetrical, an asymmetrical flow field was identified in the cylinder. As a result of this, a direct comparison of the in-cylinder LDV measured and CFD computed results was not possible. However, LDV and CFD results for the in-cylinder flow are presented to help highlight the dissimilarity between the measured and predicted flow fields. Two-dimensional LDV measurements were made in the cylinder at the transfer ports for a portion of the cycle. A comparison of these LDV measurements with CFD predictions of the in-cylinder velocities at the same locations showed that the CFD model could replicate reasonably well the general trend of the flow. The measured cylinder averaged turbulent kinetic energy was compared with that of the CFD model. The qualitative trend of the overall turbulence generating capacity of the engine was well replicated by the CFD model.
Effect of heat and mass transfer coefficients on the performance of automotive catalytic converters
Authors: Shamim T
Published: April 2003

This paper numerically investigates the role of heat and mass transfer coefficients on the performance of automotive catalytic converters, which are employed to reduce engine exhaust emissions. The pollutant conversion performance of a converter is influenced by a number of physical and chemical processes that take place in gaseous and solid phases as the exhaust gases flow through the catalyst. A quantitative predictive understanding of these complex catalyst processes involving flow dynamics, heterogeneous surface reactions and heat and mass transport mechanisms is important in improving the converter design. The role of convective transport phenomena becomes important at high temperature when the mass transfer becomes rate-limiting to an increasing extent. The objective of the present study is to elucidate the influence of convective heat and mass transfer coefficients (mechanisms). The mathematical model considers the conservation of mass, momentum and energy in both gaseous and solid phases. In addition to the heterogeneous surface reactions, the model also takes into account the adsorption/desorption of oxygen in the catalyst during non-stoichiometric composition of air/fuel mixtures. The governing equations are solved by an implicit scheme using a successive line under a relaxation method. The converter performance under the transient conditions as simulated by the US Federal Test Procedure (US-FTP) is analysed.
Analysis of cycle-by-cycle variation in a direct injection gasoline engine using a laser-induced fluorescence technique
Authors: Fujikawa T , Nomura Y , Hattori Y , Kobayashi T , Kanda M
Published: April 2003

To analyse the cycle-by-cycle variation of combustion in a direct injection gasoline engine equipped with a fan-shape spray nozzle and operated with exhaust gas recirculation (EGR), the fuel mixture distribution was measured at a time of spark and during the combustion period by the laser-induced fluorescence (LIF) technique. It was found that in the case of advanced or retarded injection timing, the initial combustion period tends to extend and the indicated mean effective pressure (i.m.e.p.) becomes low when lean mixtures appear at the spark position and at the spark timing. This suggests that the cycle-by-cycle variation of combustion under these conditions is dominated by the fuel concentration at the spark position and spark timing. In contrast to this, for the best injection timing, which allows the lowest cycle-by-cycle variation, the i.m.e.p. fluctuation is affected not by the initial combustion period but by the main combustion period. The observation of LIF images revealed that the i.m.e.p. fluctuation at this condition is strongly correlated to the unburned mixture quantity at the side area of the piston cavity during the latter half of the combustion period. It was shown by a computational fluid dynamics (CFD) calculation that the combination of a uniform spray pattern and a compact cavity shape is effective to reduce the over-lean mixture region in the edge of the piston cavity, which is responsible for the cycle-by-cycle variation of combustion at the condition of best-tuned injection timing.
Rapid Synthesis of SnSe Nanowires via an Ethylenediamine-assisted Polyol Route
Authors: Shen Guozhen , Chen Di , Jiang Xuan , Tang Kaibin , Liu Yankuan , Qian Yitai
Published: April 2003

A rapid ethylenediamine-assisted polyol (ENAP) process has been proposed to synthesize SnSe nanowires with high aspect ratio for the first time. The product was characterized by X-ray powder diffraction and transmission electron microscope. It was found that ethylenediamine has a great influence on the morphology and purity of the final products.
An Acid–Base Controlled Molecular Switch. syn–anti Conformational Switching in a μ-oxo Bis(Iron Porphyrin)
Authors: Hembury Guy A , Borovkov Victor V , Lintuluoto Juha M , Inoue Yoshihisa
Published: April 2003

It was found that FeD adopted a stable syn conformation as a result of the inclusion of atomic oxygen in a μ-oxo fashion, but on exposure to acidic conditions converted into the extended anti form. When this was subsequently made basic the syn conformation was re-adopted, simply due to re-inclusion of atomic oxygen forming the μ-oxo species. It was found that the combination of these affects allowed FeD to undergo repeated conformational switching cycles that were reproducible and robust.
Preparation and Properties of Sterically Protected Diphosphene and Fluorenylidenephosphine Bearing the 2,6-Di-tert-butyl-4-methoxyphenyl Group
Authors: Toyota Kozo , Kawasaki Subaru , Nakamura Akitake , Yoshifuji Masaaki
Published: April 2003

A new bulky bromobenzene, 2-bromo-1,3-di-tert-butyl-5-methoxybenzene, was prepared and utilized to preparations of the corresponding diphosphene and fluorenylidenephosphine including low-coordinate phosphorus atom(s). An electronic perturbation of the p-methoxy group in the system was indicated by UV–vis spectra and 31P NMR chemical shifts.
Review of The Ordinary Business of Life by Backhouse
Authors: Brittan Samuel
Published: April 2003

Roger Backhouse's book The Ordinary Business of Life is a comprehensive history of economic thought, from the ancient Greeks to the present day. It will be useful both to specialist economists and to people with a smattering of economic ideas who want to fill in the historical gaps. Backhouse's book provides much of the material for anyone brave enough to tackle the big issues.
Detection of Defects at Different Locations in Ball Bearings by Vibration and Shock Pulse Monitoring
Authors: Tandon N. , Kumar K.S.
Published: April 2003

In the present study, the vibrations and shock pulse values of good and defective bearings have been measured. Bearings with one defect and two defects (with different degrees of separation) on the outer race have been used. The position of the defects with respect to the maximum load zone axis was also varied. The study shows that it is easier to detect defects on the outer race of bearings when the defects are in the maximum load zone. The vibration levels and shock pulse values decrease with increase in angle between two defects. The levels decrease as the defects are moved away from the maximum load position. Shock pulse method showed better defect detectability as compared to overall vibration levels. However, at low speed, the shock pulse method has not proved to be as effective as at higher speeds.
Minmax Regret Median Location on a Network Under Uncertainty
Authors: Averbakh Igor , Berman Oded
Published: April 2003

We consider the 1-median problem on a network with uncertain weights of nodes. Specifically, for each node, only an interval estimate of its weight is known. It is required to find the “minimax regret” location, i.e., to minimize the worst-case loss in the objective function that may occur because a decision is made without knowing which state of nature will take place. We present the first polynomial algorithm for this problem on a general network. For the p roblem on a tree network, we discuss an algorithm with an order of complexity improved over the algorithms known in the literature.
Time-Indexed Formulations for Machine Scheduling Problems: Column Generation
Authors: van den Akker J.M. , Hurkens C.A.J. , Savelsbergh M.W.P.
Published: April 2003

Time-indexed formulations for machine scheduling problems have received a great deal of attention; not only do the linear programming relaxations provide strong lower bounds, but they are good guides for approximation algorithms as well. Unfortunately, time-indexed formulations have one major disadvantage—their size. Even for relatively small instances the number of constraints and the number of variables can be large. In this paper, we discuss how Dantzig-Wolfe decomposition techniques can be applied to alleviate, at least partly, the difficulties associated with the size of time-indexed formulations. In addition, we show that the application of these techniques still allows the use of cut generation techniques.
A Stochastic Branch-and-Bound Approach to Activity Crashing in Project Management
Authors: Gutjahr W. J. , Strauss C. , Wagner E.
Published: April 2003

Many applications such as project scheduling, workflow modeling, or business process re-engineering incorporate the common idea that a product, task, or service consisting of interdependent time-related activities should be produced or performed within given time limits. In real-life applications, certain measures like the use of additional manpower, the assignment of highly-skilled personnel to specific jobs, or the substitution of equipment are often considered as means of increasing the probability of meeting a due date and thus avoiding penalty costs. This paper investigates the problem of selecting, from a set of possible measures of this kind, the combination of measures that is the most cost-efficient. Assuming stochastic activity durations, the computation of the optimal combination of measures may be very expensive in terms of runtime. In this article, we introduce a powerful stochastic optimization approach to determine a set of efficient measures that crash selected activities in a stochastic activity network. Our approach modifies the conventional Stochastic Branch-and-Bound, using a heuristic—instead of exact methods—to solve the deterministic subproblem. This modification spares computational time and by doing so provides an appropriate method for solving various related applications of combinatorial stochastic optimization. A comparative computational study shows that our approach not only outperforms standard techniques but also definitely improves conventional Stochastic Branch-and-Bound.
Algorithms for Path-Based Placement of Inspection Stations on Networks
Authors: Rosenkrantz Daniel J. , Tayi Giri K. , Ravi S. S.
Published: April 2003

Placement of inspection stations is a common task in transportation and communication networks. In this paper, two categories of problems involving placement of inspection stations are studied. The first category deals with the selection of inspection stations along a given path from an origin to a destination. The second considers simultaneous selection of both a path and inspection stations along that path. We formulate these problems under a variety of minimization objectives such as the maximum gap between two consecutive inspection stations, the expected penalty cost of failure along the path, and the total inspection cost. Our results include efficient algorithms for many formulations and complexity results as well as fully polynomial approximation schemes for other formulations. When considering cost objectives, we identify a core problem and show that the complexity of many formulations is directly related to the complexity of the core problem.
Selecting Scheduling Heuristics Using Neural Networks
Authors: Gupta Jatinder N. D. , Sexton Randall S. , Tunc Enar A.
Published: April 2003

This paper discusses the application of neural networks to select the best heuristic algorithm to solve a given scheduling problem. The two-stage hybrid flowshop with multiple identical parallel machines at the second stage is used as an example to discuss the process of selecting a scheduling heuristic through a neural-network approach. This paper uses the genetic-algorithm-based approach for training the neural network and shows that the suggested neural-network approach is quite effective and efficient for selecting the best heuristic algorithm for solving a given scheduling problem.
Modifications of Uncertain Data: A Bayesian Framework for Belief Revision
Authors: Dey Debabrata , Sarkar Sumit
Published: April 2003

The inherent uncertainty pervasive over the real world often forces business decisions to be made using uncertain data. The conventional relational model does not have the ability to handle uncertain data. In recent years, several approaches have been proposed in the literature for representing uncertain data by extending the relational model, primarily using probability theory. The aspect of database modification, however, has not been addressed in prior research. It is clear that any modification of existing probabilistic data, based on new information, amounts to the revision of one's belief about real-world objects. In this paper, we examine the aspect of belief revision and develop a generalized algorithm that can be used for the modification of existing data in a probabilistic relational database. The belief revision scheme is shown to be closed, consistent, and complete.
A Formal Approach to Workflow Analysis
Authors: Basu Amit , Blanning Robert W.
Published: April 2003

Agile manufacturing, fast-response micromarketing, and the rise of the virtual organization have led managers to focus on cross-functional business processes that link various divisions and organizations. These processes may be realized as one or more workflows, each of which is an instantiation of a process under certain conditions. Because an ability to adapt processes to workflow conditions is essential for organizational responsiveness, identifying and analyzing significant workflows is an important activity for managers, organization designers, and information systems specialists. A variety of software systems have been developed to aid in the structuring and implementation of workflow systems, but they are mostly visualization tools with few analytical capabilities. For example, they do not allow their users to easily determine which information elements are needed to compute other information elements, whether certain tasks depend on other tasks, and how resource availability affects information and tasks. Analyses of this type can be performed by inspection, but this gives rise to the possibility of error, especially in large systems. In this paper, we show how a mathematical construct called a metagraph can be used to represent workflows, so that such questions can be addressed through formal operations, leading to more effective design of organizational processes.