bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Approach for Simultaneous Vehicle Handling and Path Tracking Improvement Through SBW System
Authors: Janbakhsh Amir Ali , Kazemi Reza
Published: January 2011

A nonlinear adaptive sliding mode control for simultaneous vehicle handling and path tracking improvement through the Steer-By-Wire system is presented in this paper. The proposed adaptive sliding mode controller, which is insensitive to system uncertainties, offers an adaptive sliding gain to eliminate the precise determination of the bound of uncertainties. The sliding gain value is calculated using a simple adaptation algorithm which does not require extensive computational load. A driver control model is also presented according to the preview or look-ahead strategy to generate the appropriate steering angles using the vehicle states feedback and the future information about the path to be followed. Moreover, because of the inertia and viscous damping in the steering mechanism and the effects of coulomb friction and self-aligning moment of the front tires, the steering system controller based on the proposed adaptive sliding mode scheme, is designed to control the front steering angle. A complete stability analysis based on the Lyapunov theory is presented in order to guarantee the closed loop stability. Eventually, the simulation results confirm that the proposed adaptive robust controller not only improves the vehicle handling and path tracking performance but also reduces the chattering problem in presence of uncertainties in the tire cornering stiffness and the external disturbance.
Investigation of Bubble Nucleation on Platinum Solid Surface Using Molecular Dynamics (MD) Simulation
Authors: Mirnouri Langroudi S. M. , Ghasemi M. , Shahabi A. , Rezaei Nejad H.
Published: January 2011

The main purpose of this paper is to numerically investigate the contact angle of a bubble on a solid surface and the effect of bubble curvature on the surface tension. A computer code based on Molecular Dynamics method is developed. The code carries out a series of simulations to generate bubbles between two planar solid surfaces for different wettabilities. In our simulation, the surface wettability affects the bubble contact angle and curvature. The pair potential for the liquid–liquid and liquid-solid interaction is considered using Lennard-Jones model. Density profiles are locally calculated. Furthermore, surface tension is computed using Young-Laplace equation. It is observed that the gas pressure is independent of the bubble radius. However, the liquid pressure becomes more negative as the radius decreases. In addition, the amount of surface tension decreases by decrease of the radius.
A Numerical Study on Flow Characteristics of 2D Vertical Liquid Jet Striking a Horizontal Surface
Authors: Kimiaghalam M. , Passandideh-Fard M.
Published: January 2011

We studied numerically impingement of vertical liquid jets of moderate Reynolds number for both Newtonian and non-Newtonian liquids to clarify the structure formation of circular hydraulic jump and the phenomenon of jet buckling. First, we have studied the hydraulic jump characteristics and governing parameters for a laminar water jet. Moreover, different types of hydraulic jump have been investigated by varying the height of a circular wall around the bed in flow downstream. The results show that a circular hydraulic jump has two kinds of steady states which can be reached by changing wall height. Next, we studied the impingement of a non-Newtonian liquid jet on a solid surface. In this case, we observe that instead of having a significant hydraulic jump, jet buckling phenomenon happens. The results were used in order to achieve a better understanding of the jet buckling phenomenon and the conditions in which this phenomenon happens.
Genetic Algorithm for Multi-Objective Exergetic and Economic Optimization of Parabolic Trough Collectors Integration Into Combined Cycle System (ISCCS)
Authors: Baghernejad Ali , Yaghoubi Mahmood
Published: January 2011

Thermoeconomic analyses of any thermal system design are always based on the economic objectives. However, knowledge of economic optimization may not be sufficient for decision making process, since solutions with higher thermodynamic efficiency, in spite of small increases in total costs, may result in much more interesting designs due to changes in the energy market prices or in the energy policies. In this paper a multi-objective optimization scheme is developed and applied for an Integrated Solar Combined Cycle System (ISCCS) that produces 400 MW of electricity to find solutions that simultaneously satisfy exergetic as well as economic objectives. This corresponds to search for a set of Pareto optimal solutions with respect to the two competing objectives. The optimization process is carried out by a particular class of search algorithms known as multi-objective evolutionary algorithms (MOEAs). For such MOEAs, an example of decision-making is presented and a final optimal solution has been introduced. The final optimal solution that is selected in this analysis belongs to the region of Pareto Frontier with significant sensitivity to the costing parameters. However, the region with lower sensitivity to the costing parameter is not reasonable for the final optimum solution due to a weak equilibrium of Pareto Frontier in which a small changes in exergetic efficiency of plant due to variation of operating parameters may lead to the danger of increasing the cost rate of product, drastically. The analysis shows that optimization process leads to 3.2% increasing in the exergetic efficiency and 3.82% decreasing of the rate of product cost. Also optimization leads to the 2.73% reduction on the fuel exergy, 5.71% reductions in the total exergy destruction and also 3.46% and 7.32% reductions in the fuel cost rate and cost rate relating to the exergy destruction, respectively.
Measurement and Simulation of Indoor Air Quality and CO2 Concentration in a Hotel Room
Authors: Asadi Ehsan , Gameiro da Silva Manuel , Costa Jose´ J.
Published: January 2011

Indoor air quality (IAQ) is nowadays universally recognized as an important issue that affects the comfort and health of people, as well as their productivity. This paper describes the relationship of indoor CO2 concentration to building air quality and ventilation, with a focus on how CO2 can be used to evaluate and predict air quality and ventilation performance, namely the infiltration airflow rate. Besides it shows the ability of ESP-r building simulation software for predicting the CO2 concentration and the air exchange rate in a building. For this purposes a room of a hotel located in the urban area of Coimbra was chosen. The developed simulation model was then validated against empirical results. It was shown that a fair degree of agreement between ESP-r results and the experimental observation exist for the zones. High accuracy of the simulation model showed that building simulation software, namely ESP-r can provide a better understanding of indoor environmental conditions and be a powerful tool in finding the best modification measures for improving the indoor air quality in a building.
Experimental and Numerical Analysis of the Piston Cooling Jet’s Performance
Authors: Izadi Mohamad , Hosseini Seyed Vahid , Alaviyoun Seyed Shahab , Mirsalim Seyed Mostafa Agha
Published: January 2011

Recently, with development in the output power and material cost efficiency, the value of thermal and mechanical stress on many engine parts such as piston is increased. On the other hands, the strength of aluminum alloys used for piston manufacturing decreases with temperature. So, for lightweight pistons, the strength reduction should be minimized to maintain the mechanical integrity of the part. This drives piston designers to use strong and lightweight materials that can sustain a harsh thermal environment through improved oil cooling. In addition to modify the power output, piston cooling reduces the carbonization and pre-ignition caused by hot spots on sharp edges of the piston crown. In this study, in order to evaluate the piston cooling functionality and validate the numerical simulation, a test rig is designed and manufactured and it is equipped with glassy piston and cylinder to show the oil contact surface. Using this test rig, flow rate is measured in different oil pressures and temperatures. In addition, heat transfer coefficient for various engine speeds is determined. Also a numerical model has been developed using CFD approach for analysis of piston cooling oil jet and validated with existing experimental results at axisymmetric condition. Finally, oil contact area and heat transfer coefficient are predicted at the bottom of piston for real piston cooling jet conditions.
An Analytical Study to Free Vibration Control of Composite Beams With Piezoelectric Layers Based on First Order Shear Deformation Theory
Authors: Abbaszadeh Bidokhti Ali
Published: January 2011

In this paper a new approach is applied to investigate the effects of piezoelectric materials on the damping properties of laminated composite beams. The active control is obtained by using an actuator and a sensor piezoelectric layer acting in a closed loop. The formulation is based on the first order shear deformation theory (FSDT). There are purely mechanical models in the literature, but only at a finite element level. Generally the electric quantities are condensed from an electromechanical finite element model. Here, an analytical study is performed to get equivalent beam equations that are of elastic type. The model is applicable. Analytical solutions are developed for simply supported composite beams with piezoelectric layers. A constant velocity feedback control algorithm is used to actively control the dynamic response of the structure through a closed loop control. Numerical results of vibration suppression effect for various locations and thickness of the piezoelectric layers, lay-up sequence, and control parameters are presented.
Assumed-Modes Formulation of Piezoelectric Energy Harvesters: Euler-Bernoulli, Rayleigh and Timoshenko Models With Axial Deformations
Authors: Erturk Alper , Inman Daniel J.
Published: January 2011

Harvesting of vibration energy has been investigated by numerous researchers over the last decade. The research motivation in this field is due to the reduced power requirement of small electronic components such as wireless sensor networks used in monitoring applications. The ultimate goal is to power such devices by using the waste vibration energy available in their environment so that the maintenance requirement for battery replacement is minimized. Among the basic transduction mechanisms that can be used for vibration-to-electricity conversion, piezoelectric transduction has received the most attention due to the large power densities and ease of application of piezoelectric materials. Typically, a piezoelectric energy harvester is a cantilevered beam with one or two piezoceramic layers and the source of excitation is the base motion in the transverse direction. This paper presents general formulations for electromechanical modeling of base-excited piezoelectric energy harvesters with symmetric and asymmetric laminates. The electromechanical derivations are given using the assumed-modes method under the Euler-Bernoulli, Rayleigh and Timoshenko beam assumptions in three sections. The formulations account for an independent axial displacement variable in all cases. Comparisons are provided against the analytical solution given by the authors for symmetric laminates and convergence of the assumed-modes solution to the analytical solution with the increasing number of modes is shown. Experimental validations are also presented by comparing the electromechanical frequency response functions derived here against the experimentally obtained ones. The electromechanical assumed-modes formulations given here can be used for modeling of piezoelectric energy harvesters with asymmetric laminates as well as those with moderate thickness and varying geometry in the axial direction.
Stirling Engine: An Emerging Prime Mover for Micro-CHP Systems
Authors: Scarpete Dan , Badea Nicolae
Published: January 2011

In this paper, an analysis of different micro-CHP systems is made from the point of view of benefits and limitations of several prime movers used in micro-CHP systems: reciprocating engines, Stirling engines, micro steam and gas turbines and fuel cell systems. A comparison using the metrics and weighting factors is suggesting that the reciprocating engines and the Stirling engines are more appropriate for the micro-CHP. In another analysis, micro-CHP factors related to efficiency and thermal/electric power for different prime movers are compared. Micro-CHP systems with Stirling engine has the best score. The electric efficiency is better for micro-CHP systems with reciprocating engines, and Stirling engines are in the second place. The thermal efficiency is better for micro-CHP systems with Stirling engines followed by reciprocating engines. Stirling engines use an external heat source, which simplifies design, minimizes noise and vibration, and allow multi-fuel use. These features make the Stirling engine a promising alternative to the internal combustion engine.
The Effect of Blank Thickness on the Shear Band Localization During Fine Blanking of 1045 Steel Plate
Authors: Parsa M. H. , Taieban S.
Published: January 2011

Fine blanking is a near net shape process that is used for manufacturing of final product. In the fine blanking process, V-ring indentation is applied to create hydrostatic pressure and prevent premature fracture in an undesired direction. Furthermore, a small clearance between the punch and die is employed along with a counterforce punch that causes concentrated strain in the sheared band region. This process generally applies for sheet metal up to 6 mm. Application of this process for blanking of sheets thicker than 6 mm require some precautions for sound production. In the present research work, finite element analyses have been performed to investigate the effects of thickness variations on the shear band localization and shear surface quality in the fine blanking process. Simulations have been performed for two thicknesses of 6 and 8 mm. As blank materials, steel sheets of AISI 1045 have been used for numerical investigations.
Indoor Environmental Mapping by Means of Autonomous Guided Agents
Authors: Galetto Maurizio , Mastrogiacomo Luca , Pralio Barbara , Spagnolo Cristina
Published: January 2011

The indoor environmental monitoring of industrial production sites is becoming increasingly important in an attempt to comply with current regulations inhering working conditions and production standards. Although monitoring tasks often consist of repetitive, time-consuming, and sometimes dangerous actions, they are mostly carried out by a human operator, who is responsible for carrying the sensor set around the working area and for enabling the communication with a remote processing system. The aim of the paper is to present the architecture of an integrated autonomous system for three-dimensional mapping of environmental conditions in indoor spaces. The proposed system integrates one (or more) autonomous guided vehicles, carrying the sensor set around the working area, a distributed wireless sensor network, providing a real-time tracking of the mobile agent, and a remote processing unit to store and elaborate the measured data. A prototype implementation of the system is herein described, in order to demonstrate the overall system feasibility.
Optimization of Concentration and Temperature of KOH Etchant on Micromachining Process
Authors: Shayan Mohsen , Arezoo Behrooz , Amani Ali
Published: January 2011

Due to vast application of silicon wet etching in Micromachining and MEMS structure, investigation about parameters that have more influence on wet etch rate is indispensable. Wet etch rate is dependent to several factor such as temperature, etchant concentration and crystal orientation. Because of temperature and concentration are more controllable therefore the etch rates R{hkl} depend mainly on concentration and temperature of the etchant. Understanding the relation between this parameters and wet etch rate can assist us in order to control and optimization of micromachining process. This paper present a relation between etchant concentration and temperature and wet etch rate on (100) plane, and then identify the etchant concentration in a certain range of temperature as the wet etch rate be in optimal amount. With optimization the etch rate of wafer (100), necessary time for etching process reduces and this reduction of time can lead to reduction of undercutting at convex and concave corners.
Analysis of Single Phase Convective Heat Transfer in Microchannels With Variable Thermal Conductivity and Viscosity
Authors: Go¨zu¨kara Arif Cem , Yazıcıoglu Almıla G. , Kakac¸ Sadık
Published: January 2011

The need for maximizing the performance of micro-mechanical systems and electronic components has resulted in a trend of minimization. Minimized sizes and dimensions have come along with a complex heat transfer and fluid problem within these devices and components. For a variety of fields in which these devices are used, such as; biomedicine, micro fabrication, and optics, fluid flow and heat transfer at the microscale needs to be understood and modeled with an acceptable reliability. In general, models are prepared by making some extensions to the conventional theories by including the scaling effects that become important for microscale. Studies performed in the last decade have shown that, some of the effects that are thought to become significant for a microscale gas flow are; axial conduction, viscous dissipation, and rarefaction. In addition to these effects, the temperature variable thermal conductivity and viscosity may become important in microscale gas flow due to the high temperature gradients that may exist in the fluid. Therefore, effects of variable thermal conductivity and viscosity in microscale gas flow and convection heat transfer are investigated in this study. For this purpose, simultaneously developing, single phase, laminar and incompressible air flow in a micro gap between parallel plates is numerically analyzed. In the analyses, scaling effects such as rarefaction, viscous dissipation, and axial conduction are taken into account in addition to the temperature variable thermal conductivity and viscosity.
A Modification on Performance of MEMS Gyroscopes by Parametro-Harmonic Excitation
Authors: Pakniyat Ali , Salarieh Hassan , Vossoughi Gholamreza , Alasty Aria
Published: January 2011

In this paper, parametric excitation for MEMS gyroscope proposed by Oropeza-Ramos, et al. [1–4] is examined and problems associated with this kind of excitation are shown. It is proved that origin has exponential stability for some sets of parameter values (including those considered in [1–4]). This stability is shown to be global for linearized system and local for the general nonlinear system. Hence, it is concluded that if there would be a periodic orbit, the system has difficulties reaching it. As a solution, a harmonic term to the parametric excitation is added and the new actuation is referred to as parametro-harmonic excitation. It is shown that there are some parameter values for which a stable periodic orbit exists. Finally, stability of periodic orbit of the linear parametro-harmonically excited MEMS gyroscope is analyzed based on Floquet Theory. Figures show that in the non-resonant driving frequencies, only stiffness and damping play important roles in the stability of periodic response and other terms like excitation voltage and imposed external rotation are of less influence on this stability. However, in the parametric resonant regions, not only stiffness and damping affect stability, but also excitation voltage is of great importance.
Integrated AFS and DYC Sliding Mode Controller Design for Hybrid Electric Vehicle
Authors: Mashadi Behrooz , Majidi Majid
Published: January 2011

An integrated controller of active front steering and direct yaw moment is developed in this paper. In upper layer, the corrective steering angle and yaw moment are obtained using sliding mode control. A combined sliding surface is defined in order that the yaw rate and side slip angle of vehicle track the desired values. The corrective yaw moments are applied by electrical motors embedded in rear wheels. The desired value for yaw rate and sideslip angle are obtained from a 4-DOF nonlinear vehicle model. In the lower layer, the active steering, wheel slip and electrical motor torque controllers are designed. Wheel slip and motors torque controllers generate the longitudinal forces in the rear wheels to produce the desired yaw moment. A nonlinear nine degrees of freedom vehicle model is used for simulation purposes. The simulation results illustrate considerable improvements in vehicle handling.
Quantitative Feedback Theory Controller Design for Vehicle Stability Enhancement
Authors: Mashadi Behrooz , Goharimanesh Masoud , Gharib Mohammad Reza , Majidi Majid
Published: January 2011

The main objective of this paper is to use a robust controller based on quantitative feedback theory on vehicle to control it at different work conditions. There are different parameters affecting vehicle stability from which Changes in speed, road condition, vehicle mass, center of gravity position and tire stiffness are the most important parameters in this aspect. In this paper, the various steps of controller design are undertaken and an optimal robust controller is designed. An eight degrees-of-freedom, nonlinear vehicle model is used for the evaluation of controller performance. Several maneuvers are considered for the vehicle motions under different working regimes in order to reveal the effectiveness of the design controller. The simulation results show very good vehicle behavior under controlled actions in situations where the uncontrolled vehicle has undesired behavior. It is also shown that with the presence of different uncertainties, the controller is able to produce accurate desired responses.
Tribological Characterization of Particulate Composites
Authors: Bria Vasile , Birsan Iulian-Gabriel , Circiumaru Adrian , Ungureanu Victor , Roman Igor
Published: January 2011

Among composites, the polymer matrix ones are the cheapest and the easiest to form but they show major disadvantages such as poor electrical and thermal conductivity, low fire resistance etc. In the case of any composite, some of the properties may be designed, some of them may be obtained by using an appropriate forming technique and, at least, some of them may be improved by special treatments. In the case of polymer matrix composites the first two ways are recommended if we are taking into account the polymers’ properties while the last one will turn the PMC into an expensive material due to the costs of metal or oxide thin film deposition on polymeric surface. Is it possible to solve all the problems by material design and by developing a convenient forming technique? Powders are used as fillers in order to obtain bi-components composites. The most important aim is about the uniform distribution of particles in matrix. If the fillers’ particles are arranged into the polymer volume is possible to change the electro-magnetic behavior of the obtained composite making this one to act as a meta-material. The powders can be dielectric as talc, clay or ferrite can be magnetic active as ferrite, or electric active as CNT or carbon nano-fibers. All these powders have effects on the electromagnetic, thermal and mechanical properties of the composite. This study is about the influence of fillers on the tribological behavior of particulate composites. Epoxy resin was used as matrix and various powders were used to fill the polymer: ferrite, zinc, clay. The materials were thermally treated in order to reach the best polymer properties. Pin on disk fixture on a CETR-UTM had been used to determine the friction coefficient for each filler concentration. The Wear resistance of each material had been evaluated using the same apparatus but with some modifications.
First Test Results of a Haptic Tele-Operation System to Enhance Stability of Telescopic Handlers
Authors: Cenci Stefano , Rosati Giulio , Zanotto Damiano , Oscari Fabio , Rossi Aldo
Published: January 2011

According to a recent report of ILO (International Labour Organization), more than two million people die or loose the working capability every year because of accidents or work-related diseases. A large portion of these accidents are related to the execution of motion and transportation tasks involving heavy duty machines. The insufficient degree of interaction between the human operator and the machine may be regarded as one of the major causes of this phenomenon. The main goal of the tele-operation system presented in this paper is to both preserving slave (machine) stability, by reducing the inputs of slave actuators when certain unsafe working conditions occur, and improving the level of interaction at master (operator) side. Different control schemes are proposed in the paper, including several combinations of master and slave control strategies. The effectiveness of the algorithms is analyzed by presenting some experimental results, based on the use of a two degrees-of-freedom force feedback input device (with one active actuator and one passive stiff joint) coupled with a simulator of a telescopic handler.
A Cable-Suspended Robot With a Novel Cable Based End Effector
Authors: Saber Omid , Abyaneh Soroush , Zohoor Hassan
Published: January 2011

Object handling is one of the most important applications of cable-suspended robots, which can be obtained by use of a gripper as its end-effector. In this paper, a novel cable-driven multi-finger gripper assembled on a cable-suspended robot has been presented. Using lock/unlock mechanisms, the under-actuated finger mechanism has been designed to have a human like motion. A cable-suspended robot structure with 3 position degrees of freedom is also proposed by employing active/passive cables in such a way that makes it capable of resisting external moments, while it may be simplified to a spatial point-mass cable robot during positioning operation. Furthermore, the robot workspace has been investigated and by considering both lower and upper cable tension limits, a formulation for obtaining the force-feasible workspace is presented and the influence of the minimum tension limit on the workspace is discussed. Finally the moment-resisting capability of the proposed robot has been investigated and by considering several cases, its moment-resisting region is compared to an analogous robot.
An Inverse Numerical/Analytical Approach to Predict the Material Properties of Carbon Nanotube/Polymer Interphase
Authors: Parsa A. , Mosavi Mashhadi M.
Published: January 2011

There is substantial interest in using carbon nanotubes (CNTs) to create multifunctional polymer composite materials with outstanding mechanical, electrical, and thermal properties. A difficulty in modeling the behavior of these systems is the non-bulk interphase region in these systems that forms due to nanoscale interactions between the embedded NTs and adjacent polymer chains. However, the mechanical properties of this interphase region are unknown and very difficult to measure directly from experimental testing due to the size scale of this interphase region. Thus a three-phase (nanotube, interphase and matrix) Mori-Tanaka micromechanical model has been developed such that the properties of this interphase region can be inferred from macroscale elastic data. Both as-received and functionalized NTs have been considered in order to investigate the influence of functionalization on predicted mechanical properties of the interphase. A hybrid finite element-micromechanical method is also used to consider the effect of NT waviness in modeling. Results show that the Young’s modulus of interphase region is significantly higher than that of bulk polymer and it must be considered as an independent reinforcement mechanism in CNT/polymer nanocomposites.
Micro-Scale Numerical Model of Bovine Cortical Bone: Analysis of Plasticity Localization
Authors: Abdel-Wahab Adel A. , Maligno Angelo R. , Silberschmidt Vadim V.
Published: January 2011

Evolution of damage and fracture in a bone is affected by its microstructure. A non-uniform distribution of osteons in a cortical bone tissue results in a localization of deformation processes. Such localization can affect bone performance under external load and initiate fracture. In this paper, a two-dimensional numerical (finite-element) model for osteonal bovine cortical bone was developed with account for its microstructure. The topology of a transverse-radial cross section of a bovine cortical bone was captured with optical microscopy. The elastic-plastic data for the microstructural features of the cross section was obtained with a use of the nanoindentation technique. Both the topology and nanoindentation data were used as input to the model formulated with the Abaqus finite-element software. The area, directly reflecting micro-scale information, was embedded into the region with homogenised properties of the cortical bone. Different scenarios of the loading were tried: (i) tension in transverse direction, (ii) tension in radial direction and (iii) tension in both directions. The calculated stress and strain fields for various cases of loading demonstrate different patterns due to implementation of microstructural features in the finite-element model. There are obvious signs of localization of the plastic regions at the micro-structure level that can be considered as fracture precursors. The suggested approach emphasizes the importance of microstructural features in development of bone failure.
Modeling and Analysis of Hot Extrusion Metal Forming Process Using Artificial Neural Network and ANOVA
Authors: Zohourkari Iman , Assarzadeh Saeed , Zohoor Mehdi
Published: January 2011

In this paper, a feed-forward back-propagation artificial neural network (BP-ANN) and analysis of variance (ANOVA) are applied to a hot metal extrusion process, establishing a black box model as well as analyzing the effects of relevant process parameters on required forging load, under different operating conditions. Some finite element simulation data on extruding ck-45 steel, adopted from a published research paper, were used to train the neural model employing Levenberg-Marquardt learning algorithm. Die angle (15°–75°), friction coefficient between billet-die material pair (0.4–0.8), punch velocity (168–203 mm/s), and billet temperature (1000°C–1260°C) were selected as the inputs, while the extrusion load (tone) was considered as the network’s output. Based on the results during modeling attempts, a 4-10-10-1 size neural network has been decided on as the appropriate architecture of the process model. Testing predictive accuracy of the developed model was also done using a new data set (8 data samples), which has not been used in the training phase. The comparative errors with respect to the desired FEM simulations are all in acceptable ranges (less than 12%) thereby the network’s generalization capabilities were confirmed. Having established the appropriate neural model, analysis of variance (ANOVA) technique was then applied to the original training data base to find and recognize the level of importance of each parameters and their possible dual interactions on the extrusion loading force within 95% of confidence interval (α = 0.05). Based on the obtained inferences, the best optimal combination of parametric settings which leads to the minimum required extruding load was then revealed and recommended. The optimally minimized extrusion force was then predicted by the trained network model. Neural network tool box (NNET) of the Matlab software and design of experiments module of Minitab software were employed as platforms to develop neural simulations and ANOVA technique, respectively. The overall results indicate the feasibility and effectiveness of the proposed approach in a real manufacturing environment and eliminate the need to carry out expensive as well as time consuming trial and error experimentations to reach to the optimum operating conditions.
Classical and Generalized Coupled Thermoelasticity of a Layer
Authors: Hosseini Zad S. K. , Eslami M. R.
Published: January 2011

A one-dimensional thermoelastic region is modeled based on the classical and generalized coupled thermoelasticity theories, and a finite element scheme is employed to obtain the field variables directly in the space and time domains. The problem is solved for two different types of boundary conditions (BCs), and the behavior of temperature, displacement and stress waves according to these BCs and based on the classical and generalized coupled thermoelasticity theories are shown and compared with each other. Several characteristics of thermoelastic waves are examined according to this analysis, and comparison between the behavior of classical and generalized coupled thermoelasticity theories in extended period of time is made to examine the damping effects of each theory.
The Improvement of Cooling Performance of a Flash Pumped Laser Using Nd:YAG
Authors: Erdog˘mus¸ A. Berkan , S¸ahin Murat , C¸olakog˘lu Ali Murteza , Erentu¨rk Birol
Published: January 2011

In this study, the cooling performance of a flash pumped laser using Nd:YAG was investigated. The examined system is used to cool down the laser head of a range finder device where heat is produced. Three dimensional CFD model for the examined system was generated and the results were verified by using experimental study. The transient approach and k-epsilon turbulence model were used during the computational analysis. It was realized that the result were in good consistency. At the end of the verification, it is found that the use of extended surfaces on the heat sink does not enhance the heat transfer from the surface in 3 minutes during transient phase because of low thermal diffusivity of titanium material and the undesired high temperature values were seen. Then the cooling system was modified. As a result more reliable cooling system is developed. The enlargement of the liquid flow channels increases the heat transfer and reduces the heat sink temperatures with addition of negligible pressure drop.
Artificial Neural Networks Based Wear Prediction for Pneumatic Drives Seals
Authors: Ciortan Sorin , Podaru Geanina , Birsan Iulian Gabriel , Spanu Constantin
Published: January 2011

Sealing systems used for non-metallic rod pneumatic drives have hard duty conditions, including the absence of any kind of lubricant and non-linear thermal regime. Due to this, the wear evolution of the lip -rod pair can be difficult to be estimated. The paper propose an ANN based method for wear prediction during service life of the lip seals, taking into account some seals’ working behavior influencing factors.
Pneumatic Drives’ Seals Efficiency Monitoring by Thermography Based Methods
Authors: Podaru Geanina , Birsan Iulian Gabriel , Ciortan Sorin , Deleanu Lorena
Published: January 2011

Pneumatic drives systems have specific working conditions like smell-less and invisible power fluid, almost dry friction regime in sealing etc.. All these, nest to the impossibility to collect and measure the leakage, make difficult to establish the moment when the first leakage occur and the evolution of drive’s seal efficiency after that. Assuming that in case of non-metallic rod drives the temperature has particular distribution, the paper propose a thermography based method to monitor and evaluate the pneumatic seals’ leakage, on the fly, without suspend the system duty.
Static Analysis of Moderately Thick Functionally Graded Plates With Various Boundary Conditions
Authors: Shahmansouri Nastaran , Aghdam Mohammad Mohammadi , Bigdeli Kasra
Published: January 2011

The present study investigates static analyses of moderately thick FG plates. Using the First Order Shear Deformation Theory (FSDT), functionally graded plates subjected to transversely distributed loading with various boundary conditions are studied. Effective mechanical properties which vary from one surface of the plate to the other assumed to be defined by a power law form of distribution. Different ceramic-metal sets of materials are studied. Solution of the governing equations, including five equilibrium and eight constitutive equations, is obtained by the Extended Kantorovich Method (EKM). The system of thirteen Partial Differential Equations (PDEs) in terms of displacements, rotations, force and moment resultants are considered as multiplications of separable function of independent variables x and y. Then by successful utilization of the EKM these equations are converted to a double set of ODE systems in terms of x and y. The obtained ODE systems are then solved iteratively until final convergence is achieved. Closed form solution is presented for these ODE sets. It is shown that the method is very stable and provides fast convergence and highly accurate predictions for both thin and moderately thick plates. Comparison of the normal stresses at various points of rectangular plates and deflection of mid-point of the plate are presented and compared with available data in the literature. The effects of the volume fraction exponent n on the behavior of the normalized deflection, moment resultants and stresses of FG plates are also studied. To validate data for analysis fully clamped FG plates, another analysis was carried out using finite element code ANSYS. Close agreement is observed between predictions of the EKM and ANSYS.
The Use of Schwartz Geometries for Scaffold Design in Tissue Engineering Applications
Authors: Almeida Henrique A. , Ba´rtolo Paulo J.
Published: January 2011

Additive biomanufacturing processes are increasingly recognised as ideal techniques to produce scaffolds for tissue engineering applications. Scaffolds provide a temporary mechanical and vascular support for tissue regeneration while shaping the in-growth tissues. These scaffolds must be biocompatible, biodegradable, with appropriate porosity, pore structure and pore distribution and optimal vascularisation, with both surface and structural compatibility. Surface compatibility means a chemical, biological and physical suitability to the host tissue. Structural compatibility corresponds to an optimal adaptation to the mechanical behaviour of the host tissue. Recent advances in the tissue engineering field are increasingly relying on modelling and simulation. The design of optimised scaffolds based on the fundamental knowledge of its microstructure is a relevant topic of research. This paper proposes the use of novel geometric structures based on the Triple Periodic Minimal Surfaces formulation, namely the Schwartz primitives, one of the a sub-classes of Triple Periodic Minimal Surfaces. Schwartz primitives enables the design of vary high surface-to-volume ratio structures with high porosity and mechanical/vascular properties. With the use of a computational tool combining structural, computational fluid dynamics and topological optimisation schemes, it is possible to predict and optimise both mechanical and vascular behaviour of scaffolds for soft and hard tissue applications, with different topological architectures and levels of porosity. This tool is particularly important to quantify the structural heterogeneity and scaffold mechanical properties with a designed microstructure subjected to either a single or a multiple load distribution. This computational tool enables the simulation of biological flows in vascular passages of scaffolds. The blood flow considered in this study is a complex fluid comprising a suspension of red blood cells, white blood cells and platelets within a newtonian plasma.
Testing to Investigate the Use of Lap Belt Positioners During Pregnancy
Authors: Weekes Alix M. , Acar B. Serpil
Published: January 2011

Some pregnant women do not use the seat belt, and many have the lap belt incorrectly positioned across the abdomen instead of across the hips. Seat belt positioners are available as aftermarket products that claim to hold the lap belt in the correct position and prevent it from riding upward onto the abdomen. The Hybrid III 5th percentile female dummy with MAMA2B pregnancy conversion kit is used to investigate comparatively whether the positioners increase or decrease the protection of the original seat belt. The tests clearly support the correct positioning of the lap belt over the hips rather than on the abdomen. The tests suggest the use of the aftermarket seat belt positioners offers no obvious disadvantage (higher abdominal pressure) compared to use of the lap belt in the correct position across the hips. It can be concluded that if the use of positioners encourages pregnant women firstly to use the seat belt, and secondly possibly to help position it correctly across the hips, then this might offer benefit.
Statistical Error Analysis for Dimensional Control in Automotive Body Assembly Process
Authors: Khodaygan S. , Movahhedy M. R. , Mirabolghasemi A. , Zendehbad M. , Moradi H.
Published: January 2011

In mechanical assemblies, the performance, quality, cost and assemblability of the product are significantly affected by the geometric errors of the parts. This paper develops the statistical error analysis approach for dimensional control in automotive body multi-station assembly process. In this method, the homogeneous transformation matrices are used to describe the location and orientation of part and assembly features and the small homogeneous transformation matrices are used to model the errors. In this approach, the effective errors in automotive body assembly process are classified in three categories: manufacturing errors (dimensional and geometric tolerances), locating errors (fixture errors) and process errors (joining errors). In a mechanical assembly, small variations due the errors propagate according to a complex mechanism that in this approach it formulated in error analysis procedure. The propagation chain of geometric errors is described based on CAD models. The estimation of the error accumulation and the percent contributions of individual errors are based on the statistical model (root-sum-square method). The application of the proposed method is illustrated through presenting an example problem.
Spectral Element Model for the Transverse Vibrations of Thin Plates
Authors: Lee Usik , Jang Injoon
Published: January 2011

The frequency-dependent spectral element matrix (or exact dynamic stiffness matrix) has been known to provide very accurate solutions in structural dynamics by using only a minimum number of degrees of freedom which may resolve the computation and cost problems. Thus, this paper presents a spectral element model for thin plates by using the concept of plane-waves superposition.
Gas Turbine Power Boosting: Evaporative Cooling
Authors: Brusca S. , Lanzafame R.
Published: January 2011

It is well known that gas turbines performance depend on ambient conditions. In particular, power production decreases when ambient temperature increases. It is possible to restore standard performance while running at critical temperatures using a power boosting technique such as evaporative cooling. The present paper deals with analysis of gas turbines power boosting by means of an evaporative cooling technique. In order to study the impact of the technique on gas turbine performance, a mathematical model of a General Electric MS6001FA gas turbine has been implemented using GateCycle software. The mathematical model was calibrated and tested using real gas turbine data for different running conditions. Test results show that the model is able to simulate engine behavior in all considered conditions with low errors. Parametric analysis in function of ambient conditions at maximum load was carried out. It was imposed a specific value of artificial air humidity using real ambient temperature and pressure. Thus, performance analysis of gas turbine running was carried out.
Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle
Authors: Bohn D. , Krewinkel R. , Wolff A.
Published: January 2011

The flow field and heat transfer in the internal cooling system of gas turbines can be modelled using rotating-disc systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the Maximum Entropy Production (MEP) Principle as a possible means of simplifying numerical computations for these complex flows. This theory is based on the heat flux out of the cavity. In this numerical study, the Nusselt numbers on the disc walls inside an open rotating cavity with a Rayleigh number of approximately 4.97×108 are evaluated with regard to the computed Nusselt numbers on the disc walls. These can be considered to be representative of the flow inside the cavity. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximised, or, conversely, the system is unstable when the heat transfer is minimised. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.
Heat Accumulator in Large District Heating Systems: Simulation and Optimisation
Authors: Badyda Krzysztof , Bujalski Wojciech , Milewski Jarosław , Warchoł Michał
Published: January 2011

Heat accumulators in large district heating systems are used to buffer heat production. Their main purpose is to make heat production as independent as possible from district heating system demand. To do this effectively a heat accumulator of appropriate capacity must be selected. In large district heating systems, heat accumulators can be used for equalising production over periods lasting a few hours. Accumulators can be used for optimising electricity and heat production to achieve possible highest income. It may be important in situations where on-line prices change. An optimising algorithm for heat accumulator use is shown and commented. Typical working situations are simulated and results presented.
Fuel Emulsification Plants on Board of Gas Turbines
Authors: Cerri Giovanni , Chennaoui Laila , Giovannelli Ambra , Miglioli Mauro , Salvini Coriolano
Published: January 2011

An innovative Emulsification Engine Feeding System (EEFS) has been developed in the Roma Tre University Fluid Machinery Lab. It is based on an emulsification loop, where fuel and water are fed in real time with the emulsion injection. Thus no chemicals to stabilize water in diesel fuel or ethanol in diesel fuel emulsions, are used. The system assures a sufficient stability level of the emulsion to be injected inside the combustor. Tests carried out on the EEFS, developed for a 250–300 kW gas turbine have shown the good quality of the emulsion in terms of the water droplet diameters and volumetric mixing ratio at the various engine loadings. A water separation section that operates for the duration of the engine shutdown is an unique feature of the EEFS to avoid corrosion during stops.
A Parametric Study on the Effect of Sister Hole Location on Active Film Cooling Flow Control
Authors: Ely Marc J. , Jubran B. A.
Published: January 2011

This paper presents an investigation on the effect of sister holes on film cooling. The proposed technique surrounds a primary injection hole by two or four smaller sister holes to actively maintain flow adhesion along the surface of the blade. A numerical evaluation using the realizable k-ε turbulence model led to the determination that the use of sister holes significantly improves adiabatic effectiveness by countering the primary vortical flow structure. Research was performed to determine the optimal hole configuration, arriving at the conclusion that placing sister holes slightly downstream of the primary injection hole improves the near-hole effectiveness, while placing sister holes slightly upstream of the primary hole improves downstream effectiveness. On the whole, the sister hole approach to film cooling was found to offer viable improvements over standard cooling regimes.