bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Simple Triangular Plate Elements Based on the Absolute Nodal Coordinate Formulation
Authors: Dmitrochenko Oleg , Mikkola Aki
Published: September 2008

In this paper, two triangular plate elements based on the absolute nodal coordinate formulation (ANCF) are introduced. Triangular elements employ the Kirchhoff plate theory and can, accordingly, be used in thin plate problems. As usual in ANCF, the introduced elements can exactly describe arbitrary rigid body motion when their mass matrices are constant. Previous plate developments in the absolute nodal coordinate formulation have focused on rectangular elements that are difficult to use when arbitrary meshes need to be described. The elements introduced in this study have overcome this problem and represent an important addition to the absolute nodal coordinate formulation. The two elements introduced are based on Specht’s and Morley’s shape functions, previously used in conventional finite element formulations. The numerical solutions of these elements are compared with previously proposed rectangular finite element and analytical results.
Control Design and Robustness Analysis of Linear Time-Periodic Systems
Authors: Kalender S. , Flashner H.
Published: September 2008

This paper proposes a new design approach for control of periodically time-varying systems. The approach is based on the point-mapping technique to obtain an equivalent linear time-invariant sampled-data system for the linear periodically time-varying system with a piecewise parametrization of the control vector. This allows the known control design techniques for sampled-data systems to be applied. The proposed approach is then extended for analysis of robustness of the control design with respect to plant parametric uncertainties. This is achieved by computation of approximate discrete-time dynamics of the perturbed system by truncated point-mappings. By computing an upper norm bound on the error due to the truncated approximations, the robustness analysis of the system with respect to the parametric uncertainties is then formulated as a discrete-time structured singular value problem. Two numerical examples are considered to illustrate the approach and the extension of the approach for robust stability analysis.
Multiobjective Optimization of a Microchannel Heat Sink Using Evolutionary Algorithm
Authors: Husain Afzal , Kim Kwang-Yong
Published: September 2008

A multiobjective performance optimization of microchannel heat sink is carried out numerically applying surrogate analysis and evolutionary algorithm. Design variables related to microchannel width, depth, and fin width are selected, and two objective functions, thermal resistance and pumping power, are employed. With the help of finite volume solver, Navier–Stokes analyses are performed at the design sites obtained from full factorial design of sampling methods. Using the numerically evaluated objective function values, polynomial response surface is constructed for each objective functions, and multiobjective optimization is performed to obtain global Pareto optimal solutions. Analysis of optimum solutions is simplified by carrying out trade-off with design variables and objective functions. Objective functions exhibit changing sensitivity to design variables along the Pareto optimal front.
Effects of Growth Temperature on Carbon Nanotube Array Thermal Interfaces
Authors: Cola Baratunde A. , Amama Placidus B. , Xu Xianfan , Fisher Timothy S.
Published: September 2008

Due to their excellent compliance and high thermal conductivity, dry carbon nanotube (CNT) array interfaces are promising candidates to address the thermal management needs of power dense microelectronic components and devices. However, typical CNT growth temperatures (∼800°C) limit the substrates available for direct CNT synthesis. A microwave plasma chemical vapor deposition and a shielded growth technique were used to synthesize CNT arrays at various temperatures on silicon wafers. Measured growth surface temperatures ranged from 500°Cto800°C. The room-temperature thermal resistances of interfaces created by placing the CNT covered wafers in contact with silver foil (silicon-CNT-silver) were measured using a photoacoustic technique to range from approximately 7mm2°C∕Wto19mm2°C∕W at moderate pressures. Thermal resistances increased as CNT array growth temperature decreased primarily due to a reduction in the average diameter of CNTs in the arrays.
Effect of Channel Geometry Variations on the Performance of a Constrained Microscale-Film Ammonia-Water Bubble Absorber
Authors: Jenks Jeromy , Narayanan Vinod
Published: September 2008

An experimental study of the absorption of ammonia vapor in a constrained thin film of ammonia-water solution is presented. A large aspect ratio microchannel with one of its walls formed of a porous material is used to constrain the thickness of the liquid film. Experiments are performed at a pressure of 2.5 bar absolute and 4 bar absolute and at a fixed weak solution inlet temperature. Weak solution flow rates are varied from 10 g/min to 30 g/min (corresponding to the weak solution Reynolds number, Re, from 15 to 45), inlet mass concentrations are varied from 0% to 15%, and gas flow rates are varied between 1 g/min and 3 g/min (corresponding to the vapor Re from 160 to 520). Six geometries, including three smooth-bottom-walled channels of differing depths and three channels with structured bottom walls, are considered. Results indicate that, for identical rates of vapor absorption, the overall heat transfer coefficient of the 400 μm absorber is in most cases significantly larger than that of other absorbers. For the 150 μm and 400 μm absorbers, a trade-off between the high overall heat and mass transfer coefficients is achieved for the highest vapor to solution flow rate ratio.
Three-Dimensional Numerical Simulation on the Laminar Flow and Heat Transfer in Four Basic Fins of Plate-Fin Heat Exchangers
Authors: Zhu Yinhai , Li Yanzhong
Published: September 2008

In this paper, four basic fins of the plate-fin heat exchangers, rectangular plain fin, strip offset fin, perforated fin, and wavy fin, are modeled and simulated by taking account of fin thickness, thermal entry effect, and end effect. Three-dimensional numerical simulations on the flow and heat transfer in the four fins are investigated and carried out at laminar flow regime. Validity of the modeling technique is verified by comparing computational results with both corresponding experimental data and three empirical correlations from literatures. Global average Colburn factor (j factor) and friction factor (f factor) and their local 1D streamwise-average distributions along the fins are presented by introducing data reduction method. The heat transfer behaviors in both the developing and developed regions are analyzed by examining variations of the local Nusselt number along the flow direction. It is found that the thermal entry length of the four fins might be expressed in the format of Le=c1 Rec2 Pr Dh, which has the same form as the one in a circular tube.
An Experimental Investigation of Sorption Process in Fluidized Bed With Cooling Pipe
Authors: Horibe Akihiko , Husain Syahrul , Inaba Hideo , Haruki Naoto , Tu Ping
Published: September 2008

An experimental investigation of a fluidized bed with multiple cooling pipes was conducted to study adsorption characteristics of a new organic sorbent desiccant material (HU300P) for a new air conditioning system. The mass ratio of the present sorbent desiccant powder type is from 1.3 to 2.3 times greater than that of silica gel. The sorption rate of the water vapor in the sorbent bed was measured under various conditions. It was found that the sorption rate is highly dependent on the effect of cooling pipes. The sorption ratio increases and the completion time for the sorption process decreases by using multiple cooling pipes.
Simulation of Thermal Fluid Flow Transport in a Channel Containing Slot-Perforated Flat Plates
Authors: Torii Shuichi , Yang Wen-Jei
Published: September 2008

A numerical study is performed to investigate unsteady, two-dimensional, incompressible laminar flow over both sides of a slot-perforated flat surface in a pulsating channel flow. Consideration is given to the effects of the pulsating Strouhal number fSr, the Reynolds number Re, and the blockage factor, i.e., the ratio of plate thickness, δ, to channel width, W, on the heat-transfer performance and the velocity and thermal fields. It is found from the study that (i) time-averaged Nusselt number at the rear plate is amplified with Re, (ii) in contrast, the corresponding performance is attenuated with an increase in the blockage factor, whose effect becomes larger in the lower region of the Reynolds number, i.e., Re=100, and (iii) enhancement of the Nusselt number causes an increase in fSr, whose effect becomes minor near in the region of Re=100.
Blocker Forging Die Design Using Backward Deformation Method
Authors: Biglari Farid R. , Zamani Neyestani Mahmoud , Nickbin Kamran M.
Published: September 2008

In forging processes, several operations are often required to achieve gradual metal flow from a simple shape of initial billet to a more complex shape of the desired final forging. Amongst various kinds of preforming operations, the blocker is the stage that is normally used before the finishing operation. The geometry of the blocker cavity is often similar to that of the finisher. An appropriate design of the blocker preform can lead to a defect-free metal flow in the final forging operation and complete die-filling with minimum metal loss and die wear. However, the optimum design of the blocker die is an extremely difficult task and is known to be an art by itself, requiring skills that are achieved only by years of extensive experience. This paper presents a blocker die design using the backward deformation method. This method employs the finite element analysis during each reverse deformation step. It involves an alternative boundary node release criterion in the finite element simulation of backward tracing of forging processes to reduce the die wear in the finishing operation. The procedure starts with the forward simulation of a candidate preform into the final forging shape. A record of the boundary condition changes is produced by identifying the time that a particular segment of the die makes contact with the workpiece surface in forward simulation. Also the wear profile on the die surface during forging is calculated by implementing friction work model into a finite-element user written subroutine. Recorded time sequence is then optimized with the aim of releasing those nodes that are located on the segments of the die which have higher wear profile, in the first stages of the backward simulation. The modified boundary conditions are finally used as the boundary condition that controls the criterion for the inverse deformation simulation. Two examples of the blocker preform design for two forging components are performed and presented in this paper.
Wind Turbine Installation for High Elevations
Authors: Battisti Lorenzo , Giovannelli Ambra
Published: September 2008

The strong drive to exploit wind energy has recently led to new types of location for wind turbine installations being considered, including mountain regions and, to be more specific, areas at elevations coming between 800 and 2,500 m asl. Authoritative sources, such as the European Wind Energy Association (EWEA), have estimated that 20–25% of the approximately 60,000 MW expected to be installed in Europe between now and 2010 will be situated in cold-climate areas, and a part of them will be on hills and mountains. The installation of wind farms in the mountains consequently demands an in-depth analysis, in the design of such plant, into both the methods for assessing the resource and the more or less direct transfer of procedures and technologies developed for conventional sites. For the time being, the IEC standards (originally developed to provide a reference picture relating to conventional sites) fail to provide recommendations on this type of site, where the structure of the flow field is substantially more complex in terms of its effect on the stresses involved. The present work outlines the main features of mountain wind farm sites and discusses the effects of some of said features on the structural assessment of the turbines destined for such installations in the light of the IEC standard requirements. The work illustrate that the installation of wind turbines in mountain sites must consider different site-related features from those used to develop the requirements of the IEC standards. The examples given here indicate that, based on the standards, these features influence both energy generation and the turbine’s working life. Only an adequate understanding of these features can lead to a cost-effective sizing of the turbines. This type of approach can lead to a site-specific design concept, and only certain components are structurally adequate for the stress characteristics of a given site. These procedures will then have to be transferred to the standards, overcoming the conflict between the minimum standard requirements specifying the fundamental elements to consider in the project and the set of parameters describing the external conditions that demand a turbine of equivalent sturdiness in comparable applications.
Modeling of Gas Turbine Cooled Blades
Authors: Pashayev A. , Askerov D. , Sadiqov R. , Samedov A. , Ardil C.
Published: September 2008

In contrast to existing methods which do not take into account multiconnectivity in a broad sense of this term, we develop mathematical models and highly effective combination (BIEM and FDM) numerical methods of calculation of stationary and quasi-stationary temperature field of a profile part of a blade with convective cooling (from the point of view of realization on PC). The theoretical substantiation of these methods is proved by appropriate theorems. For it, converging quadrature processes have been developed and the estimations of errors in the terms of A.Ziqmound continuity modules have been received [6]. For visualization of profiles are used: the method of the least squares with automatic conjecture, device spline, smooth replenishment and neural nets. Boundary conditions of heat exchange are determined from the solution of the corresponding integral equations and empirical relationships. The reliability of designed methods is proved by calculation and experimental investigations heat and hydraulic characteristics of the gas turbine first stage nozzle blade.
Power and Emission Evaluation of Natural Gas Engines Converted From Gasoline
Authors: Shariat Bashir Samsam
Published: September 2008

In the present article, the performance analysis of a bi-fuel spark ignition engine is investigated. An originally gasoline-fuelled car is used for experimental tests. It is converted to a bifuel vehicle which may run both on natural gas and gasoline. The wheel and motor power of the car are measured before and after conversion together with exhaust emissions. It is observed that the engine power reduces not only in gas but also in gasoline state after the conversion in comparison with the base engine power. The effect of gas/air mixer design is fully explained. The results of closed-loop and open-loop gas supplying systems are compared. The influence of ignition timing on the power loss is discussed. The optimum timing advance for natural gas is obtained through laboratory experiments. The power and emissions of the converted vehicle are compared with the base power and emission values for a series of engine speeds. The reasons for the power loss are discussed and some useful methods are recommended to decrease the amount of power loss.
A New Recognition Method for Damping Coefficients of Rod Pumping System of Directional Well
Authors: Liu Baixi , Liu Hongzhao , Yuan Daning , Rao Jianhua
Published: September 2008

In this paper, a pattern recognition method is put forward to identify damping coefficients of rod pumping system of directional well by using characteristics space mapping. The 24-direction chain code is presented to encode the curve of dynamometer card. The parametric equation of the dynamometer card curve is transformed into Fourier series whose coefficients can be computed according to the curve’s chain codes. By means of those Fourier coefficients, shape characteristics of the curve are extracted. Euclidean distance is introduced as the measurement of similar degree between the shape characteristics of measured dynamometer card and that of simulated dynamometer card. Changing the value of viscous damping coefficient and Coulomb damping coefficient in the simulation program, different simulated dynamometer cards are obtained. Substituting their shape characteristics to the Euclidean distance, respectively, a series of distances are acquired. When the distance is little than the given error, the corresponding values of the damping coefficients in the simulation program are regarded as real damping coefficients of the rod pumping system of directional well. In the end, an example is provided to show the correctness and effectiveness of the presented method.
Optimization of Fatigue Life of Hollow Rollers Under Pure Normal Loading
Authors: Abu-Jadayil Wisam M. , Flugrad Donald R.
Published: September 2008

Fatigue life investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages between 20% and 80% have been tested to find the optimum percentage hollowness that gives the longest fatigue life. Two main models were built for this purpose. Model 1 with two identical sized rollers and Model 2 with two non identical sized rollers. In each model, two cases have been studied, when both rollers are hollow and the case when one roller is hollow while the other one is solid. The Ioannides-Harris (IH) theory was used to calculate the relative fatigue life of the hollow rollers with respect to solid rollers under same loading. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel. The finite element package ABAQUS has been used to study the stress and deformations in the loaded rollers. In general, the optimum hollowness percentage with the longest fatigue life ranges between 60% and 70% based on the kind of the material, whether the rollers are same size or different size and whether both rollers are hollow or only one of them is hollow. Using IH theory for fatigue life calculation resulted in having infinite fatigue life for those rollers made of Induction-hardened steel that relatively has high fatigue limit value. Rollers in the optimum range are flexible enough to get the best redistribution the stress in the contact zone. For models of a hollow cylindrical roller in contact with a solid roller, the optimum hollowness is around 70%. When both cylindrical rollers are hollow, the optimum hollowness decreases to be between 60% and 65%. At the optimum hollowness, small differences in the fatigue life have been found between models of one hollow roller and models of two hollow rollers. Even though, having both rollers hollow means less weight, saving more material and more stability for the system.
A New Model for Dynamic Analysis of Side Mounted Diffuser Valve Micropumps
Authors: Ahmadian M. T. , Mehrabian Amin
Published: September 2008

Valveless micropumps are widely used due to simple structure, durability and low maintenance. Understanding the fluid-membrane interaction and performance criteria is still a challenging problem for the scientists. In this work, a new model for side mounted valve micropumps is developed to obtain dynamic response of micropump with respect to piezoelectric actuation. The parameters of this model are obtained in terms of actuation frequency and geometrical dimensions of the micropump. Balancing elastic, inertial and damping forces result in the governing equation of the micropump system model. Analytical studies for the bottom mounted valve micropump indicate pump flux is independent of the chamber geometrical aspect ratio while, for the side mounted valve micropumps, geometric aspect ratio is an important factor in the net flux. Findings indicate there exists a peak excitation frequency at which the flux is maximum. As the excitation frequency increases beyond the peak frequency, the pump flux decreases sharply. This is due to enhancement of the fluid inertial forces. By increasing the aspect ratio of the chamber the maximum net flux raises considerably. While, increasing membrane to valve area ratio has adverse effect on the pump efficiency. Findings show that good agreement exists between the net flux response to actuation frequency obtained from modeling and experiment.
A Short Note on Stability of Linear Time Delay Systems
Authors: Medenica M. S. , Debeljkovic D. Lj.
Published: September 2008

Our research on stability criteria for linear systems with time delay in a frequency domain has brought in a new stability criterion that belongs to the group of graph-analytical stability criteria. Via the theory of functions with a complex variable, this criterion is based upon Cauchy’s theorem of argument and condition that for frequency ω varying from −∞ to +∞ the argument of function f*(jω,ejωτ) has positive change. In solution, as a graphic interpretation in the f* - plane, a spiral curve is obtained, which possesses some characteristics crucial for the stability of a system with time delay. Through given examples, simplicity and facility of criteria application to different cases of systems are shown.
Method of Dynamic Analysis for Rod-in-Hole Buckling
Authors: Tikhonov Vadim S. , Safronov Alexander I. , Gelfgat Mikhail Ya.
Published: September 2008

The problem of a postbuckling dynamic behavior of weighted rod, which is inserted into an arbitrary profile hole with some clearance, under the axial compression load is considered. In practice, this analysis is important for calculation of the friction drag of the drillstring in inclined and horizontal wellbores. The mathematical model and numerical method of the rod-in-hole contact interaction are developed. The contact model is based on a nonlinear dependence of the normal-directed contact force on the depth of interpenetration of rod in hole. The tangential interaction of bodies with the contact surfaces is described using a model of “elastic-plastic” friction. The developed system of substantially nonlinear differential equations with partial derivatives of 3-D rod dynamics is approximated by the finite differences and integrated by the Runge-Kutta method. A simplified model for axial motion of rod is suggested to make the process of numerical integration faster. The results of numerical simulation of stress-deformed state of rod in horizontal, inclined and curved holes are presented. The results of numerical simulation are compared with the results of experiment. The effect of the friction factor on the rod buckling has been studied. The effect of local outside bulges of the drillstring on a postbuckling behavior of the drillstring is considered.
Optimization of Hypoid Gears Performance Characteristics With Typical Manufacturing and Assembly Errors
Authors: Kolivand Mohsen , Soltani Nasser , Hannaneh Abdolhamid , Shoroki Zabihollah Kargar
Published: September 2008

A procedure for calculating and optimizing hypoid gear surface performance characteristics in the presence of the most typical errors associated with machining errors of the differential housing and assembly of gears is presented. Such errors that result in mounting or position errors of hypoid gears positioning are considered in optimization procedures and basic settings of Gleason machine. The goal of this paper is to consider machining and assembling errors of differential housing unique to a given typical manufacturing line so that conditions of optimized match between gears and the differential housing of that particular manufacturing line can be achieved. During this optimization, the condition of a predetermined contact situation up to the second-order, with optimization of third-order contact situation is considered. In order to check this calculation with other methods, the results were compared to the Gleason TCA program [1]. Moreover, practical experiments of contact pattern positioning errors on hypoid tooth surfaces with a Gleason 17A Hypoid Gear Tester are done and presented.
Equimomental System and Its Applications
Authors: Chaudhary Himanshu , Saha Subir Kumar
Published: September 2008

This paper presents a study of an equimomental system and its application. The equimomental system of point-masses for a rigid body moving in plane and space system is studied. Sets of three and seven equimomental point-masses are proposed for a planar and spatial motion, respectively. The set of equimomental point-masses is then applied for the optimization of dynamic performance characteristics of a mechanism, e.g, shaking forces and moments, driving torques, bearing reactions, etc. The Newton-Euler equations of motion of a link undergoing planar motion are formulated systematically in the parameters related to the point-masses, which leads to an optimization scheme for the mass distribution of the links to improve the dynamic performances. The effectiveness of the proposed methodology is shown by applying it to a multiloop mechanism of carpet scrapping machine. A significant improvement in all the dynamic performance characteristics is obtained compared to those of the original mechanism.
Influence of van der Waals Force on the Pull-In Parameters of Cantilever Type Nanoscale Electrostatic Actuators
Authors: Ramezani Asghar , Alasty Aria , Akbari Javad
Published: September 2008

In this paper, the influence of the van der Waals force on two main parameters describing an instability point of cantilever type nanomechanical switches, which are the pull-in voltage and deflection are investigated by using a distributed parameter beam model. The nonlinear differential equation of the model is transformed into the integral form by using the Green’s function of the cantilever beam. The integral equation is solved analytically by assuming an appropriate shape function for the beam deflection. The detachment length and the minimum initial gap of the cantilever type switches are given, which are the basic design parameters for NEMS switches. The pull-in parameters of micromechanical electrostatic actuators are also investigated as a special case of our study by neglecting the van der Waals force.
Vibration Control of Suspension System Using Proposed Neural Networks
Authors: Yıldırım S¸ahin , Eski I˙kbal
Published: September 2008

This paper investigates a new robust model based neural controller for active suspension system’s vibrations via feedback control approach. The proposed model reference adaptive control system consists of a neural controller, a robust feedback controller, a third-order linear reference model and dynamics of active suspension system. The simulation examples with various standard input signals are included to demonstrate the effectiveness of the proposed control method and show significant improvement over the existing PID controller method. The robustness of the proposed neural controller is also analyzed with white noise disturbances on the suspension system. It is shown that the control system is robustly stable for all road disturbances. Finally, this kind of control approach could be employed in real time vehicle applications.
Improving the Accuracy of Tests for Centrifugal Compressor Stage Performance Prediction
Authors: Fiaschi Daniele , Manfrida Giampaolo , Tapinassi Libero
Published: September 2008

A design of experiment approach was used to solve problems on the new centrifugal compressor stage development test beds at the Nuovo Pignone – GE Oil&Gas premises in Florence, Italy. The company is able to provide centrifugal compressor equipment tailored to the user’s requests, with special reference to the oil & gas market. In order to provide this service, an archive of designs is available which can be adapted to different requirements: CFD is widely used to improve the turbomachinery performance, and on each new stage design extensive fluid dynamics test campaigns are routinely run, in order to confirm the expected performance. Recently inadequacy of the accuracy of the measurements became evident: the cause was traced back to thermal effects which introduced a large uncertainty in the test results, with special reference to machines having large operating Mach number, and low pressure ratio. The present work included: a) The development of a heat transfer model capable of predicting the observed trend of the experimental data. b) The improvement of the accuracy of total temperature measurements, needed to confirm the results of the model. The positive results allow the company to guarantee with increased confidence the expected performance levels.
A Validated CFD Methodology to Obtain the Total Pressure Loss Coefficients in Internal Compressible Flow at Junctions
Authors: Pe´rez-Garci´a J. , Sanmiguel-Rojas E. , Herna´ndez-Grau J. , Viedma A.
Published: September 2008

A global methodology has been developed and validated to obtain the total pressure loss coefficient in internal compressible flow at T-type junctions. This methodology is based on the calculation of the thermo-fluid properties extrapolated to the branch axes intersection, once the straight pipe friction losses numerically calculated have been subtracted from the total energy losses. For this purpose, a steady adiabatic compressible one-dimensional flow with friction mathematical model has been applied to the results obtained by numerical simulation using the commercial finite volume code FLUENT. A 90 degree T-type junction has been studied and the predicted loss coefficient has been related to the extrapolated Mach number in the common branch and to the mass flow rate ratio between branches at different flow configurations, in both combining and dividing flows. The numerical results have been compared with experimental results and published data in open literature. In general, a good agreement is obtained. The correlations obtained will be applied as boundary condition in one-dimensional global simulation models of fluid systems in which these components are present.
The State of Art on Scheduling of FMS: A Comprehensive Survey
Authors: Kumar M. Vijay , Murthy A. N. N. , Chandrashekara K. C.
Published: September 2008

Flexible manufacturing systems (FMS) have already proved their great success in a large number of manufacturing industries. Realizing the importance of FMS in increasing productivity, quality, the high investment and the potential of FMS as a strategic competitive tool makes it attractive to engage in research in this area. Scheduling of flexible manufacturing systems (FMSs) has been one of the most attractive areas for both researches and practitioners. A considerable body of literature has accumulated in this area since the late 1970s when the first batches of papers were published. A number of approaches here been adopted to schedule FMS. The FMS scheduling problem has been tackled by various traditional optimization techniques and non-traditional approaches. The traditional method can give an optimal solution to small-scale problem; they are often inefficient when applied to larger-scale problem. The non-traditional approaches such as genetic algorithm generate optimal schedule to large-scale problems. Articles emphasizing many methodological perspectives are critically reviewed. The review is done from multiple viewpoints covering different approaches like simulation, artificial intelligence and genetic algorithm. Comments on the publications and suggestions for research and development are given. A comprehensive bibliography is also presented in the paper.
Using Case-Based Reasoning and Soft Computing Techniques for the Initialization of Engineering Design Optimization
Authors: Saridakis K. M. , Dentsoras A. J.
Published: September 2008

From a certain point of view, parametric engineering design may be considered as an optimization problem. The design problem may be represented through a set of design parameters. The optimal solution is located by using a set of competing design parameters and its evaluation is based upon specific criteria. A significant number of techniques and methodologies have been proposed in order to perform this difficult task. The selection of the appropriate one(s) depends strongly upon the nature and the specific characteristics of the design problem under consideration. The majority of these techniques and methodologies rely on the definition of some initial conditions. Wrong, misleading or incomplete initial conditions may result to solutions characterized by local optimality or may need excessive computational time in order to converge to either an optimal or a sub-optimal solution. In the context of the current work, two different approaches are used for initializing the optimization process: genetic algorithms and pattern search. Genetic algorithms need an initial population of individual solutions before the genetic operations could be deployed, while the pattern search techniques use a starting (initial) point for the optimization process. These two initial conditions (initial population and initial point) may be defined either randomly or deliberately. The present paper introduces a case-based design (CBD) module as pre-processor to the design optimization. This CBD module is based on an artificial competitive neural network, which is submitted to unsupervised learning by examples based on past design solutions. The new design is represented through fuzzy preferences and weighting factors, which are compiled by the neural network for retrieving similar past solutions. The retrieved solutions are used in order to determine the initial conditions of the optimization method (the initial population for the genetic algorithm (GA) or the starting point for the pattern search). The optimal solution is then searched using the criterion of the maximum aggregated overall preference. A system, namely Case-DeSC, has been developed in the purpose of evaluating the proposed framework in the application area of parametric design of oscillating conveyors. The results show that the proposed optimization methods converge faster to more efficient solutions if case-based reasoning (CBR) is utilized for defining the initial optimization conditions.
Application of Technological Algorithms and Mathematical Modelling in Cycle Chemistry Monitoring Systems
Authors: Smetanin Denis S. , Voronov Victor N.
Published: September 2008

Most Russian fossil fuelled power plants equipped with cycle chemistry monitoring systems (CCMS), as a tool to maintain water chemistry within operating limits, use these systems in informative mode only without performing any particular control function. Modern modeling methods allow for the optimizing of water chemistry control. According to the Russian guidelines, CCMS of a single unit depending on its type (drum or once-through boiler) should be based on on-line monitoring performed by 25–35 chemical analyzers; 50–100 “grab” sample analyses (daily) and about 20 on-line monitored operating parameters. Significant volume of the incoming information needs to be organized and presented to operating personnel in order to improve and optimize water chemistry at power plants, which is the main idea of CCMS, this can be achieved by implementing technological algorithms and modeling in the systems. Most of the operating CCMS are supplied with alarms to indicate water chemistry failure, alerting the operating personnel but not informing them about the danger and gravity of the event. The use of water chemistry evaluating algorithms based on system of indices provides data analysis for the operating personnel informing them on the danger of the event. Implementation of CCMS at power plants should change the role of laboratory monitoring from routine to diagnostic. The application of theoretical and experimental dependencies of different water quality parameters can be used for water chemistry optimization. In order to predict impurity distribution and deposit build-up on heat transfer surfaces and turbine blades, mathematical models of thermal cycles based on balance equations can be used in CCMS. Such models can be formed for ion-impurities, silica acid and corrosion products. Another type of model predicts impurity behavior in the event of deteriorating feed water chemistry. By means of such models operating personnel receive information about the time available to prevent steam chemistry failure. The model results should be compared with the available impurities solubility data. The majority of power plants have their particular water chemistry problems and technological disadvantages, which together with preventive and emergency measures are described in water chemistry guidelines applied at power plants. The application of logical algorithms based on these guidelines can be used in CCMS as an informative support to operating personnel in case of water chemistry failure. All the algorithms and mathematical models should only be used after their refinement to the individual power plant.
Low-Temperature and High-Temperature Thermochemical Hardening Technologies for Hard Alloys
Authors: Shmatov Alexander A.
Published: September 2008

The new surface hardening methods for hard alloys are developed: (1) high-temperature process for producing multicomponent carbide coatings by thermochemical heat treatment of hard alloys at 1050 °C and (2) low-temperature process for producing thin-film coatings by chemical treatment of hard alloys in specially prepared aqueous suspensions of nanosized hard refractory compounds and subsequent tempering (minimal temperature is 130°C). The structure and properties of the obtained coatings are examined. The coatings permit improving substantially the service life of cutting tools.
On the Thermal Behavior of an Aluminum Reduction Cell During Electrical Preheating
Authors: Hernandez Pedro J. , Salazar Juan E. , Tosta Rafael
Published: September 2008

This paper presents a thermal evaluation of a retrofitted aluminum reduction cell at the CVG ALCASA smelter. The aim of the study was to find the thermal response of the different components in the cell when loaded by joule heating from a petroleum coke resistor bed placed in between anode and cathode, working on a full current of 70 kA. A thermo-electrical approach was assumed for problem solution. For temperature and voltage drop calculations, a commercially available finite elements method (FEM) code was used. Loading conditions comprised time varying values of electrical resistivity of the coke bed as well as heat transfer coefficients, all functions of experimentally measured quantities such as voltage drop, air velocity, and external temperature. The results of the 3D one tenth cell FEM simulations show for low peak temperature values as well as a very non uniform distribution in the cell at the end of the preheating stage, urging for several process design changes already carried away.
Transient Heat Transfer Analysis of Freeze Plate Structures Cooled by Nanofluids
Authors: Jou Rong-Yuan
Published: September 2008

Heat transfer enhancement by nanofluids is an emerging and innovative technology for traditional heat transfer problems. However, researches of nanofluids for refrigeration applications are rare either theoretically or experimentally. In this paper, the physical model of a freezing chucker is considered as a two-dimensional domain which is consist of the top and bottom copper plates, and a channel for flowing of copper nanofluids. Inlet flow passes through the left hand side and exhausts to the outlet at right hand side. Three kinds of transverse rib structures, e/Dh = 0.1, 0.2, 0.3, are attached on the internal top wall of the channel for heat transfer enhancement of the coolant flows. To investigate this problem, the transient heat transfer of this channel flow is analyzed and transport problems are solved numerically for the ethylene-glycol (EG) based nanofluids mixture of copper nano-particles with volume fractions of 0%, 0.5%, 1%, 5%, respectively. The smooth channel problem is analyzed and compared to the ribbed channel problem. Analyses of the highest decay rate, the lowest temperature, and temperature distributions of the top-plate surface of a freezing chucker are shown.
An Innovative Channel Design of the Freezing Chucker
Authors: Jou Rong-Yuan
Published: September 2008

A freezing chucker is a clamp-less mechanism of fixture for easy broken egg-shell, clay, and other ferrous/nonferrous materials. Typical structure of this mechanism includes a top plate for freezing workpieces, a body with specially designed channels for the coolant flows, and a bottom plate to fasten on the table of other machine. Just by a small amount of liquids on the top surface and by rapidly cool down to 253K, parts can be frozen stationary on the top plate surface and can conduct precision machining on it. There are four steps to design a new freeze chucker by the engineering design process: planning and clarifying the task; conceptual design; embodiment design; detailed design. Some useful tools from the Quality Function Deployment (QFD) technique and the Theory of Inventive Problem Solving (TRIZ) method are used in this design process. Eight concept designs are generated by the conceptual design work and the final design of channel with transverse ribs is selected by decision matrix technique during embodiment design and detailed design stage. This final design is evaluated by numerical modeling of the COMSOL MULTIPHYSICS 3.2 finite-element based package. Performances such as the temperature distribution of top-plate surface temperature and the lowest temperature of a freezing chucker are shown. Numerical results show the success of the innovative channel design by this inventive design process using TRIZ methodology.
Calibration of the Tight Seal of the Discharge Mechanism Doors on a Rail Wagon Using Adjustable Members
Authors: Mendoza Jesus A. , Otero Luis L.
Published: September 2008

Among other types of wagons, CVG Ferrominera Orinoco (FMO) uses 350 hopper type wagons for ore transportation. Each of these wagons has a mechanical linkage system, made up of nine mobile elements plus a frame to open and close two rotary doors located at the bottom of the wagons. This paper presents development of a mathematical model to find out how the calibrating lengths of the operating mechanism’s four adjustable members allow variations of the angular position of the doors from its fully closed position. The mathematical model is obtained from the total differentials of the kinematics constraints equations and is used to find the relative influence coefficients of each adjustable member on the kinematic accuracy of the doors motion. The results show that the maximum error depends mainly upon the correct positioning of the primary element. It is also proved that two of the adjustable members in the original design do not play an important role in the tight closing.
Automatic Fault Detection Using a Model-Based Approach in the Frequency Domain
Authors: Shi Zhanqun , Higson Andrew , Zheng Lin , Gu Fengshou , Ball Andrew
Published: September 2008

In this paper, the model-based approach is introduced into rotation machinery fault detection to achieve an automatic feature extraction. The paper starts with a brief review of the model-based approach, including model development, residual generation and fault detection and diagnosis. The applicability of this approach to rotation machinery is then considered. In order to overcome difficulties arising from phase shift and random measurements, the statistical performance of the vibration of rotation machinery is analysed in both time and frequency domains. A consistence model is developed using stochastic process theory. After model validation, the model-based approach is implemented in AC motor fault detection. The residual is generated by comparing the new measurement and the model prediction, by both subtraction and division. Fault detection results prove that the model-based approach is applicable to fault feature extraction for rotation machinery in the frequency domain.
Design Optimization of Diffuser Type Valveless Micropumps
Authors: Saidi M. H. , Mehrabian Amin
Published: September 2008

Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, using finite element method, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand how the pump rectification efficiency, defining as the ratio of micropump net flux to sum of the absolute values of fluxes of inlet and outlet valves, and optimum diffuser angle depend on these parameters. At last, a set of characteristic curves are constructed which show these dependencies. The optimum working condition of micropump can be clearly found out through the use of these general characteristic curves.
Specific Performance Calculations of Two Types of Space Solar Power Systems
Authors: Furukawa Masao
Published: September 2008

Space solar power systems (SSPSs) lately planned in Japan are introduced with a result of conceptual design studies. Solar energy collected in orbit is converted into electrical energy and is transmitted to the Earth by way of microwaves or lasers. Systems of our concern are thereby Microwave-based SSPS (MSSPS) and Laser-based SSPS (LSSPS). The MSSPS basically consists of solar concentrators and a disk-like power module with I- or Y-shaped radiator. The power module is one-sidedly coated with solar cells and is internally loaded with magnetrons. The LSSPS is composed of a sun-oriented parabolic mirror and a planar radiator put on the focal line, where an array of laser devices are set up. For any of the two, system feasibilities critically depend on possibilities of size/mass reduction and heat rejection. Radiative heat transfer/exchange analyses are made considering the system thermal balance. Analysis results are written in fractional form upon the specified transmission power P. The required area A and the resulted mass M are thus simply calculated from the specific area a and the specific mass m, respectively defined as A/P and M/P. All such performance indices concerning the concentrator/mirror, the generator, the radiator, and the system are expressed in algebraic form suited to numerical computations. Empirically obtained polynomial expressions are presented to determine the cell/magnetron/laser efficiencies from the specified temperature because the system size may be highly temperature-dependent. Performance calculations have been parametrically done with various combinations of the reference temperature and the concentration ratio. Obtained numerical results are graphically shown in the figures to indicate specific system/subsystem area/mass values. Such specific values are submitted to quantitative discussion in two demonstrative design cases. Design objects are then a low-earth orbiting MSSPS of 100 kW class and a geostationary-orbiting LSSPS of 1 MW class. System feasibilities of the two are mainly examined from thermal and configurational points of view.