bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Models and Methods to Nurture General Management Skills in Engineering Students Living in Large Residential Communities
Authors: Panthalookaran Varghese , R. Biru
Published: January 2011

To be successful in one’s profession, an engineer operating in the contemporary globalized world needs to be adequately equipped with suitable management skills. They include talent to plan, implement and manage engineering projects in diverse and pluralistic teams, ability to communicate at different levels, perseverance in the face of failures and crisis, creativeness to improvise innovative solutions, maintenance of physical and mental health, ability to invent and implement eco-friendly engineering solutions, and smartness to work within stipulated time-frames, etc. Large residential student communities prepare suitable context for engineering students to nurture their general management skills, if carefully planned. In the current paper, we present some innovative models and appropriate methods to convert large residential student communities into an arena where students can train themselves in general management skills. It also presents some results of two years of implementation of such methods in a men’s hostel, which accommodates youngsters between 17–19 years of age in their first year of undergraduate engineering study.
On the Use of Flow Between Parallel Disks to Investigate Drag-Reducing Efficiency of Polymeric Additives
Authors: Jafargholinejad Shapoor , Sadeghy Kayvan
Published: January 2011

In this study we will examine the applicability of flow induced by a rotating disk in evaluating the performance of polymeric and surfactant additives in reducing skin friction drag. It is shown that these additives can dramatically reduce friction drag provided that the flow is occurring under turbulent conditions while they have no effect on Taylor instabilities. Based on the experimental data, a drag reduction in the range of 10% can be achieved with the effect becoming more pronounced with an increase in the Reynolds numbers.
Application of a Robust Minimum-Order Observer to Control the Performance of an Uncertain Multivariable Boiler Unit
Authors: Moradi Hamed , Bakhtiari-Nejad Firooz
Published: January 2011

To obtain economic operation of power plant steam generators, output of mechanical energy must be balanced with the electrical load while maintaining the internal variables within desired ranges. During a boiler unit operation, dynamic variables such as drum pressure, steam temperature and water level of drum must be controlled to achieve an appropriate performance. In this paper, a linear time invariant (LTI) model of a boiler unit is considered where feed-water and fuel mass rates are the control inputs. Due to the inaccessibility of some state variables of boiler system, a robust minimum-order observer is designed to gain an estimate state of the true state. Real dynamic model of boiler unit may associate with parametric uncertainties. In this case, optimum region of poles of observer-based controller are found such that the robust performance of the boiler system against model uncertainties is guaranteed.
An Investigation on Micro Slip Flows in Micro Channels
Authors: Salehi Gh. Reza , JalaliBidgoli Masoud , ZeinaliDanaloo Saeed , HasanZadeh Kazem
Published: January 2011

In this paper, distributions of velocity and flow rate of micro channels are studied. Moreover, the parameters which influence them were also discussed, as well as their effects and relevant curves. In the Analytical study, the governing equation in specific micro flows is obtained. This equation is specifically investigated for slip flow in two micro parallel plates (micro channel).At the next step numerical representation shows the influence of the related parameters in micro channel flow such as Knudsen number, thermal -accommodation coefficient, mass flow rate ratio and pressure ratio (outlet to inlet), Tangential Momentum Accommodation Coefficient with relative curves, and flow rate distribution in slippery state to no slip state has been compared as the another part of this solution. Finally, the results of investigating parameters and dimensionless numbers in micro channels are reviewed.
Experimental Study on the Heat Transfer Under Impinging Jet Array Using Liquid Crystal Thermograph
Authors: Chiu Han-Chieh , Jang Jer-Huan , Yan Wei-Mon
Published: January 2011

In this work, the effects of jet geometry and the arrangement of film holes on the target plate on the impinging heat transfer are experimentally investigated in detail. A liquid crystal thermograph technology is employed in this study. The aspect ratios (AR) of elliptical jet with five different values, 4, 2, 1, 0.5, and 0.25, jet Reynolds number ranging from 2000 to 4000, and jet-to-target spacing ranging from 1.5 to 4.5 are considered to investigate impingement heat transfer performance. In addition, three arrangements of film hole on the target plates, named side-, middle- and staggered-types, are tested, respectively. The experimental results show that the Nu increases with the increase of jet Reynolds number. Better heat transfer is noted for the cases with smaller jet-to-plate spacing. For the effect of the arrangement of pores on the target surface, the heat transfer on middle-type plate is more significant than the other two for smaller jet-to-plate spacing. As for the effect of aspect ratio, results indicate that the optimal heat transfer performance is found with circular jet of AR = 1.
Conjugate Heat Transfer in an Enclosure With Internal Contaminant and Heat Source Using Lattice Boltzmann Method
Authors: Hosseini Salah , Abdollahi Vahid , Nejat Amir
Published: January 2011

Conjugate convective-conductive heat transfer in an enclosure is simulated. Internal heat and contaminant sources are included in the fluid flow domain, causing mass transfer within the cavity. The two-dimensional governing equations for natural heat and mass convection in the fluid phase and heat conduction in the solid phase are solved employing lattice Boltzmann method. The effects of Rayleigh number and buoyancy ratio variations on the fluid flow, heat and mass transfer characteristics are studied.
Influence of Ambient Air Velocity Orientation in Thermal Behaviour of Open Refrigerated Display Cabinets
Authors: Gaspar Pedro Dinis , Gonc¸alves L. C. Carrilho , Ge Xiao
Published: January 2011

Open refrigerated display cabinets (ORDCs) suffer alterations of their thermal behaviour and of its performance due to variations of ambient air conditions (air temperature, relative humidity and velocity magnitude and orientation). Some factors interfere and affect the re-circulated air curtain behaviour and thus the equipment’s overall thermal performance. Examples of these factors are the location of air conditioning system discharge grilles, air mass flows originated by pressure differences due to openings to surroundings, and ambient air flow instabilities due to consumers’ passage nearby the frontal opening of the display cabinet, among others. This work performs a three-dimensional (3D) Computational Fluid Dynamics (CFD) modelling of air flow and heat transfer in an ORDC. The influence of ambient air velocity orientation in performance of the re-circulated air curtain is evaluated. A CFD parametric study is developed considering the ambient air orientation parallel, oblique and perpendicular to the frontal opening plane of the equipment. The 3D effects of ambient air velocity orientation are determined through the analysis of air temperature and velocity inside the equipment as well as along and across the air curtain. The longitudinal air flow oscillations and length extremity effects are analyzed, having a considerable influence in the overall thermal performance of the equipment. Experimental tests following EN-ISO Standard 23953 were conducted for climatic class n.er 3 (Tamb = 25 °C, φamb = 60%) in order to characterize the phenomena near inlets, outlets and physical borders. Moreover, experimental data is used to prescribe boundary conditions as well as to validate numerical predictions of temperature and velocity distributions.
Robustness of Wheelchairs Under Direct Frontal Impact Loading Conditions
Authors: Yilmazcoban Ibrahim K. , Iyibilgin Osman , Mimaroglu Abdullah
Published: January 2011

In this study, the robustness of five different commercial type wheelchairs under direct frontal impact loadings were modeled, examined and compared. Wheelchairs were modeled, simulated and analyzed under direct frontal impact process using ANSYS/LS-DYNA software. The stresses, strains and displacements of deformed shapes were obtained and compared. The results showed that, “Wheelchair Chassis 4” is the most economic and robust design. Finally the chosen wheelchair design was modified and developed and its robustness was examined.
Numerical Study on Microscopic Etch Rates for the Atomistic Simulation of Anisotropic Wet Etching
Authors: Shayan Mohsen , Arezoo Behrooz , Merati Amir Reza
Published: January 2011

For simulation of anisotropic wet chemical etching, we consider the equations of microscopic etch rates and with a trial and error method we solve these equations. We use these results and a mathematical method to derive new equation for calculating of microscopic etches rates of surface atoms under a various range of concentrations and temperatures. A comparison is made between microscopic etch rates of basic surface atoms. The results of the corresponding simulations are in good agreement with the experiments.
The Application of Bees Algorithm in Finite Element Model Updating
Authors: Fatahi Laleh , Moradi Shapour , Razi Pejman
Published: January 2011

This research work is aimed to investigate the application of bees algorithm (BA) to the finite element (FE) model updating. BA is an evolutionary optimization algorithm that imitates the natural foraging behavior of the honeybees to find the global optimum of an objective function. Here, the weighted squared sum of the error between the measured modal parameters and the FE model predictions is considered as the objective function. To demonstrate the effectiveness of the proposed method, BA is applied on a piping system to update several physical parameters of its FE model. The results obtained from the numerical model are compared with the experimental ones obtained through the modal testing. The results show that BA successfully updates the FE model. Moreover, the performance of this approach is compared with two popular optimization methods; the genetic algorithm (GA) and the particle swarm optimization (PSO). The comparison shows the advantage of BA over GA and its similarity to PSO in terms of accuracy in the presented case study. However, BA reaches to the optimum solution faster than PSO and GA. Therefore, it can be concluded that BA is a robust and accurate optimization method that could be a good candidate for the FE model updating.
Heat Transfer Measurements of Compact High Power LED Illumination Cooled by Different Fluids
Authors: Jou Rong-Yuan
Published: January 2011

The generated heats of high-power LED illumination will increase the LEDs’ working temperatures which may degrading the illumination efficiency and lifetimes of LED devices. In this study, the liquid cooling of directly immersed LEDs in different ambient of air or liquids is investigated by the experimental measurement methodology. For LEDs which are operated in series, the generated heats are dissipated into and stored in ambient fluids, then, the casing of lamp (usually acted as a heat sink structure) further conduct these heats and dissipate it into atmospheric air finally. In the experiments, different powers are sequentially input into the LEDs and different fluids, including air, silicone oil, and FC-40, respectively, are filled to cool the LEDs which are directly immersed in these fluids. Temperatures are measured by thermocouples and the IR thermal imager, respectively. Fluid-to-air thermal resistances and fluid temperatures are estimated by a proposed resistance equation. The calculated temperatures are within 10% of error as compared to experimental results. This resistance model is a very good way to quickly examine the fluid-to-air resistances if we want to design the liquid-cooled package of LED illumination.
Study of the Freezing Chuck for Non-Traditional Clamping Applications
Authors: Jou Rong-Yuan
Published: January 2011

A freezing chuck with thermoelectric coolers and coolant channels is investigated. Measurement for freezing/thawing processes and analysis of heat transfer enhancements are conducted. Three channel configurations are designed and investigated by numerical simulations and experimental measurements, respectively, to compare the temperature distributions and heat transfer enhancements. Regarding to experiments, inlet temperatures and flow rates of coolants are altered, and transient and steady surface temperatures on the top-plate are measured for these three channel designs. In numerical analysis, convective fluid flows and heat transfers are solved to find temperature, velocity, and pressure fields inside the channel and surface temperatures of top-plate of the freezing chuck by a software package. Comparisons between experimental measurements and numerical simulations are made. Effects of flow rates, inlet coolant temperatures, and channel designs, upon the steady and transient state of temperature distributions and heat transfer enhancements are discussed and conclusions are addressed.
Stamina of a Gasketed Flange Joint Under Combined Internal Pressure and Axial Loading
Authors: Abid Muhammad , Khan Niaz Bahadur
Published: January 2011

Performance of a bolted flange joint is characterized mainly due to its ‘strength’ and ‘sealing capability’. A number of numerical and experimental studies have been conducted to study these characteristics mostly under internal pressure loading. A very limited work is found in literature under combined internal pressure and axial loading. Due to the ignorance of this external (i.e. axial) loading, the optimized performance of the bolted flange joint cannot be achieved. The present design codes do not address the effects of axial loading on the structural integrity and sealing ability. To investigate, joint strength and sealing capability under combined loading, extensive numerical study of a gasketed flange joint is carried out. Actual joint load capacity is determined under both the design and proof test pressure with maximum additional external axial loading that can be applied for safe joint performance. Numerical results are compared with the available experimental results and overall joint performance and behavior is discussed in detail.
Exergy Analysis of a Compressed Natural Gas Turbocharged Spark Ignited Engine
Authors: Mirsalim S. M. , Hajialimohammadi A. , Ehteram M. , Fakhari V.
Published: January 2011

Turbo charging the CNG fueled engine is a new concept for development of the natural gas vehicles. Investigating the performance of this type of engine based on the thermodynamic laws is a useful way that can help to improve the methods of exploiting the useful work from energy and exergy losses. In this study, energy and exergy analysis are applied to the experimental data of a turbo charged CNG fueled engine. The engine was EF7 TC, which is four stroke bi-fuel CNG-gasoline engine. The data are collected using an engine test unit which enables accurate measurements of fuel flow rate, combustion air flow rate, engine speed and all the relevant temperatures. Energy and exergy efficiencies are calculated for different engine speeds and compared. Results indicate that exergy efficiency is maximum at a speed of 2500 rpm and the speed in which the maximum exergy and energy occur are not the same. It is concluded that using the unused output energy of the engine can increase useful work and therefore improve engine efficiency.
Optimizing Surface Roughness in Face Milling Using a New Meta-Heuristic Method of Harmony Search
Authors: Razfar M. R. , Farshbaf Zinati R. , Haghshenas M.
Published: January 2011

The focus of this study is on a new approach for determination of the optimal cutting parameters leading to minimum surface roughness in face milling of X20Cr13 stainless steel by coupling Neural Network (NN) and Harmony Search (HS) algorithm. In this regard, advantages of statistical experimental design technique, experimental measurements, artificial neural network and Harmony Search algorithm were exploited in an integrated manner. For this purpose, numerous experiments on X20Cr13 stainless steel were conducted to obtain surface roughness values. A predictive model for surface roughness was created using a feed forward artificial neural network exploiting experimental data. The optimization problem was solved by Harmony Search algorithm. Additional experiments were performed to validate optimum surface roughness value predicted by HS algorithm. From the obtained results, it is clearly seen that the Harmony Search algorithm is an efficient and accurate method in approaching the global minimum of surface roughness in face milling.
Measurable 5S System
Authors: Cayir Emrullah
Published: January 2011

The 5S system consists of 5 series of activities designed to improve workplace organization and standardization. These five activities begin with the letter S: Sort, Set in order, Shine, Standardize and Sustain. The key targets of 5S are to improve workplace morale, safety and efficiency and to reduce cost. In this study, industrial application of measurable 5S in a steel service center is explained. 5S performance index has been defined as a numerical basis for the measurement of 5S success. Numerical results provide objective evaluation. So, by analyzing the result of 5S performance index, improvement areas on 5S can be easily determined. This study indicates that by well-organized 5S program, 5S performance index steadily increases from the start time of 5S activities to 10 weeks after the start time. After 10 weeks, 5S performance index is maintained around desired value 100%.
Thermal Mixing Length Determination by RANS Models in T-Junction
Authors: Aounallah M. , Belkadi M. , Adjlout L. , Imine O.
Published: January 2011

In the present study, a numerical simulation is carried out in order to optimize the length of the mixing part of a T-junction to obtain a homogenous temperature distribution at the outlet. Different RANS turbulence models are tested: the Realizable k-ε the k-ω standard and the k-ω SST. The behavior of turbulent mixing flow in the mixing part of the pipe has helped in understanding the causes of discrepancy between the models used. The test case analysed in this paper is an unsteady state three-dimensional turbulent flow. The numerical results obtained show that there is a difference in the prediction of the thermal field when different models are used. The results obtained for both k-ω standard and SST models are closer compared with those given by the Realizable k-ε model. The numerical results show that a distance of x/L = 0.625 from the branch is enough to supply devices with a constant temperature.
LuGre Friction Model Based Adaptive Control With Functional Approximation Compensation for a Piezoelectric-Actuating Table
Authors: Huang Shiuh-Jer , Her Kuan-Lian , Hsiang Su-Hai
Published: January 2011

Since the piezoelectric actuators have the disadvantages of small travel and hysteretic behavior, a long range friction actuating mechanism was designed. The piezoelectric material is used to generate high frequency oscillation for actuating a finger tip which contacted with a slide to induce the back and forth motion. The LuGre friction model is chosen to simulate the dynamics of this friction actuating mechanism. However, this piezoelectric actuating system has obvious nonlinear and time-varying dead-zone offset control voltage due to the static friction and preload. It is difficulty to establish an accurate dynamic model for model-based precision control design. Hence, the functional approximation (FA) scheme is employed to compensate the system modeling error. The Laypunov-like design strategy is adopted to derive the adaptive laws and the system stability criterion. Different trajectories tracking control are planned to investigate the motion control performance and the steady state error of this adaptive controller. The dynamic experimental results of the proposed controller are compared with that of a model-based PID controller.
Simulation of the Dynamic Behaviour of a Thin-Walled Meshing Gear Using Duhamel’s Integral
Authors: Carmignani Costantino , Forte Paola , Melani Gabriele , Buffa Ugo
Published: January 2011

Aircraft transmissions have the peculiar characteristics of light structures and high operating speeds, therefore relatively low flexural natural frequencies and high excitation frequencies due to rotation and meshing. Resonance vibrations can create serious problems of malfunctions and even catastrophic failures. A reliable numerical model is surely a convenient means to perform preliminary simulations to identify the most critical resonance conditions and evaluate the effect of structural modifications on the dynamic behaviour of the component in the design development phase. Most numerical investigations found in the literature are carried out on simplified models of the rotating bodies likened to discs to reduce the computational effort. In this work a novel approach based on the application of Duhamel’s integral for the determination of the dynamic behaviour of a rotating gear subject to meshing forces has been developed to obtain more reliable results with a realistic model at an affordable computational cost. The gear response to dynamic excitation is obtained by the determination of its response to impulse using a single 3D finite element transient analysis taking afterwards into account the effect of the gear rotation. Subsequently, the Duhamel’s integral is applied using the tooth load time history in order to simulate as realistically as possible the gear load conditions. This paper presents the case of a real bi-helicoidal gear. A test bench was simulated measuring the displacement observed by some non-rotating virtual displacement sensors, located near the gear rim and disc. The signal was processed identifying the most critical rotating speeds on the basis of its RMS value. The numerical Campbell speed/frequency diagrams are in good agreement with experimental results.
Effect of Intentional Dry Friction Damping on the Performance of an Elastomeric Engine Mount
Authors: Boral Caner , Cig˘erog˘lu Ender , Korkmaz I˙brahim
Published: January 2011

Automotive engine mounts are used to protect engine from road irregularities and to isolate transmission of vibrations created by the engine which have a drastic effect on the noise generated inside the passenger cabin. Most common types of engine mounts are elastomeric and hydraulic mounts, the former having better vibration isolation characteristics whereas the latter displays better shock isolation. Elastomeric mounts are widely used for their low initial cost, while hydraulic mounts with inertia track and decoupler are chosen for their good vibration isolation and shock excitation characteristics. However, hydraulic mounts with inertia track and decoupler are not appropriate for small segment and commercial vehicles due to their high initial cost. In this paper, the effect of the addition of a dry friction damper on the performance of elastomeric automobile engine mounts is investigated. Results showed that addition of dry friction damping to the elastomeric engine mount significantly improves the transmissibility throughout a wide frequency range where the best results are obtained at the resonance frequency.
Investigating the Effect of Stone-Wales Defect on Young Modulus of Armchair Single Wall Carbon Nanotube Using Molecular Dynamics Simulation
Authors: Rezaei Nejad H. , Ghasemi M. , Shahabi A. , Mirnouri Langroudi S. M.
Published: January 2011

Effect of Stone-Wales percentage defect on effective elastic modulus of single-walled carbon nanotubes (SWCNT) is investigated. The Stone-Wales defect is a crystallographic defect that happens in nanotubes and is believed to affect the nanotubes mechanical properties. In order to calculate the mechanical properties of SWCNTs under axial tension, molecular dynamics (MD) simulations using the Morse potential is performed. An in house FORTRAN code is developed and utilized. The Young’s modulus of the perfect SWCNTs and those with different defect percentage is obtained using the classical elasticity theory. It is observed that for low percentage of defect (less than 8%) as the diameter increases the Young’s modulus of SWCNTs slightly increases. However, for high percentage of defect (more than 8%) as diameter increases the Young modulus clearly decreases.
Numerical Modeling and Simulation of a Condenser Microphone
Authors: Mehrabani M. T. , Ranjbar A. , Torkaman F.
Published: January 2011

Non-uniform deflection of a pressure condenser microphone diaphragm causes a nonlinear relationship between the deflection of the diaphragm and the induced voltage. This paper describes how the numerical dynamic analysis carried out with the second order finite difference method in space and forward difference in time domain to determine more accurately this nonlinearity and moreover, to determine the influence of the nonlinear electric field force on the mechanical system of the microphone with respect to time. For this purpose unsteady one dimensional equation of diaphragm vibration has been considered in the cylindrical coordinate. The damping and stiffness coefficients have been calculated using the squeeze film theory. Unlike the past analytical solutions, in this article the dependence of damping coefficient on the number of holes and rings, holes radius and relative angle is studied in detail. The dependence of the microphone capacitance on the diaphragm deflection can be well calculated by solving the Laplace equation using a numerical mapping. The numerical frequency response obtained for a condenser microphone has been compared with analytical solution exists in the literature. The numerical results obtained indicate a very good accuracy of the code. Such a dynamic analysis unlike the past numerical static simulation gives a deeper view into the reasons of the nonlinearity of this important measuring transducer.
Sliding-Mode Control Algorithm Development for Anti-Lock Braking System
Authors: Okyay Ahmet , Cig˘erog˘lu Ender , Bas¸lamıs¸lı S. C¸ag˘lar
Published: January 2011

In this paper, a sliding mode control methodology is implemented for the ABS control problem. Tire-road adhesion coefficient is taken as an uncertain parameter within known limits. This allows designing a robust sliding mode controller which does not require utilization of road coefficient of adhesion information, which is difficult to measure. As an improvement over previous studies, the sliding plane is formed to include both integral and derivative terms of the slip ratio error rather than only one of them. A design routine was identified in which the integral term, the derivative term and the relay action replaced by saturation compensate for each other’s drawbacks. Simulations were carried out using a quarter car model, where hydraulic components were assumed to introduce an additional first order dynamics due to hydraulic delay. Results show that, reference tracking performance and stability benefits of the integral term, which allowed for a more flexible relay term, could be used without causing oscillations. Conversely, possible instability at low speeds caused by the derivative term could be prevented by the relaxation of the relay term by means of saturation. As a result, stable controller operation with reduced chattering at both low and high velocities is realized. Finally, the enriched set of parameters involved in the sliding plane is observed to enable the designer to shape different stages of response while maintaining stability and, partly, performance characteristics.
Experimental and Numerical Study of Cavitation in Centrifugal Pumps
Authors: Niazi Erfan , Mahjoob M. J. , Bangian Ardeshir
Published: January 2011

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.
Fabrication of Metallic Wire Grating by Femtosecond Laser Ablation: A Molecular Dynamics Simulation Study
Authors: Cheng Ming-Chieh , Sung Cheng-Kuo
Published: January 2011

Femtosecond lasers enable materials processing with their notably characteristics, such as precision, high peak density, flexible, and minor thermal affected zone. Applications ranging from high precision micromachining to biological manipulation with no thermal damages are possibly executed via this technology. In this study, the three-dimensional molecular dynamics simulation associated with the parallel computation were utilized to explore the ablation mechanism, the trend between the femtosecond laser fluence density and laser ablation depth as well as affected zone. In addition, we also compared the ablation methods which were single ablation and superposited ablation machining processes. Moreover, the heat-affected zone effect was discussed. Ultimately, a femtosecond laser ablation manufacturing process simulation was implemented by the combination of laser fluence densities to demonstrate the feasibility of fabricating the metallic gratings.
Robustly Stabilizing Controller Synthesis for Haptic Devices With Maximized Transparency
Authors: Tajaddodianfar Farid , Ahmadian Mohammadtaghi , Vossoughi Gholamreza , Jazi Mehdi Molavian
Published: January 2011

Performance of a haptic device is evaluated based on the concept of transparency which indicates the match between the impedance transmitted to the user and the target virtual impedance. Stability of a haptic device prevalently has been evaluated based on the passivity criterion. Due to conservativeness of passivity, it appears as an obstacle to improve transparency. In this paper, passivity is suggested to be replaced by the complementary stability criterion which accounts for the robust stability of the interaction in the presence of uncertain user hand dynamics. In this respect, an algorithm is proposed which guarantees transparency of the haptic device in a stable manner. Assuming that the dynamics of the device is known, a certain structure of compensators is assigned. This special structure guarantees transparency of the device by compensating for the dynamics of the device and its control loop. The design objective is to obtain a stabilizing controller which achieves robust stability for the interaction of the device in the presence of parametric uncertainties of user hand dynamics and other sources of uncertainties. An iterative method is implemented to derive controller dynamics. The algorithm is applied to a series elastic actuator based haptic device model. Simulation results confirm enhanced transparency and robust stability.
An Experimental Investigation of Forced Convection Heat Transfer From an Isothermal V-Shaped Plate
Authors: Yousefi Tooraj , Ebrahimi Saeed , Bigharaz Masood , Mahmoodi Nezhad Sajjad
Published: January 2011

An experimental study has been carried out to investigate heat transfer characteristics on internal surfaces of a V-shaped plate exposed to a slot jet impingement of air. A square-edged nozzle is mounted parallel with V-shaped plate axis and jet flow impinges on the bottom of the V-shaped plate. The study is focused on Rayleigh number 159000, angle of V-shaped plate ranging from 22.5 to 45 degree, low Reynolds numbers ranging from 29.05 to 60.41, and slot-to-(V-shaped plate) spacing from 17 to 21 of the slot width. A Mach-Zehnder interferometer is used for measurement of local Nusselt number on the V-shaped plate. It is observed that the local Nusselt number and average Nusselt number decrease with increasing the jet spacing and increase with increasing the Reynolds number. Also the local Nusselt number and average nusselt number increase with rising the angle of V-shaped plate.
Impinging Jet Cooling Optimization for Obtaining Uniform Heat Flux
Authors: Kowsary Farshad , Gholamian Hamed , Rajaeeian Hoonejani Mehran
Published: January 2011

In this study obtaining a uniform heat flux over a target surface was investigated by means of using characteristics of jet impingement heat transfer. Conjugate Gradients Method (CGM) was utilized to minimize the objective function defined on the basis of the squared differences between the target heat flux and the calculated ones. Design variables were taken to be jets’ Reynolds numbers, separation distance between the exit plane of the jets and the target plate, as well as inter-jet spacing. Air single phase jets were used in this study. The problem was solved for the cases of 4 and 6 jets. Temperature difference between the jet exit and the target plate is 100°C, and a steady state condition was assumed. The Finite Volume Method and an unstructured mesh were used for direct solution of the jet impingement heat transfer problem for a laminar jets impingement to a flat plate with constant temperature.
Acoustic Emission Signal Analysis by Wavelet Method to Investigate Damage Mechanisms During Drilling of Composite Materials
Authors: Heidary Hossein , Refahi Oskouei Amir , Hajikhani Milad , Moosaloo Behrooz , Ahmadi Najafabadi Mehdi
Published: January 2011

Structural parts made of composites have frequently to be drilled in the industry. However, little is now about the interacting conditions between the drill tool and material, which may be multi-type and multi-size. Delamination free in drilling different fiber reinforced composites is the main objective of present paper. Therefore the influence of drilling and materials variables thrust force and delamination of GFRP composite was investigated experimentally. Drilling variables are cutting speed and feed; material variable is fiber orientation. Acoustic Emission sensing was employed for online detection of composite damage induced by drilling. This paper addresses an application of wavelet-based signal processing technique on a composite during drilling. The wavelet methodology is introduced and procedure of wavelet-based acoustic emission (AE) analysis methods is demonstrated. Result shows Acoustic Emission analysis by wavelet method can monitor damage mechanism in drilling of composites.
Second Law Analysis of Fully Developed Convection in a Helical Coiled Tube Under Constant Wall Temperature Using a CFD-ANN Approach
Authors: Emami Mostafa , Rahimian Mohammad H. , Alem Varzane Esfehani Saeed
Published: January 2011

The present paper analyses the second law of thermodynamics in a fully developed forced convection in the horizontal helical coiled tube under constant wall temperature. The influence of non-dimensional parameters such as Reynolds number (Re), coil-to-tube ratio (δ) and coil pitch (λ) are inspected on the entropy generation. According to the literature, the coil pitch has a minor effect on the entropy generation compared with Re and δ. Using a CFD tool is a common classical method to find the optimal Reynolds Number and coil-to-tube ratio (δ) based on the entropy generation minimization principal. This approach requires lots of time and resources while the innovative implementation of an Artificial Neural Network (ANN) reduces the simulation time considerably. The data pool generated by the CFD tool is used to train the ANN. As less data is needed to train the ANN in comparison to classical CFD based method, the performance of ANN-CFD optimization approach enhances. As entropy generation minimization principal is applied during the optimization, Nusselt number and friction factor are required to evaluate the entropy generation; these parameters are obtained through a numerical simulation and then are used to train the ANN. The ANN can predict these parameters as a function of different Re numbers and coil-to-tube ratios during optimization. Several different architectures of ANNs were evaluated and parametric studies were performed to optimize network design for the best prediction of the variables. The results obtained from the ANN are compared with the available experimental data to show the network reasonable accuracy.
An Experimental Study on Flow Induced Vibration of a Circular Cylinder in Shear Flow
Authors: Yu Ming Huei , Wu Yi-hsin
Published: January 2011

The vibrations of a circular cylinder in both uniform and shear flows are investigated experimentally. For the experimental investigation, a low speed water tunnel was designed and built to provide either uniform or shear flow in the test section, depending on the upstream flow management. In the test section, a circular tube of various materials can be flexibly mounted for vibration testing. Two accelerators were carefully installed inside the tube so that one accelerator is sensitive to the cylinder vibration in the streamwise direction only, and the other in the cross-stream direction. The vibration amplitudes of the cylinder in the streamwise and cross-stream directions were simultaneously measured by the two accelerators, and recorded by a two-channel data acquisition system. The orbits of the cylinder motion can be drawn from the data. Experiments were conduced at various mass ratios (the ratio of the cylinder mass per unit length to its buoyancy force) and shear parameters (the non-dimensional velocity gradient of the approaching fluid flow to the cylinder). By analyzing the orbits and amplitude diagrams, it is found that both the shear parameter and mass ratio have profound effects on the cylinder vibration. The orbits of the cylinder in uniform flow are symmetric while they are asymmetric in shear flow. Vibration amplitude as a function of reduced velocity illustrates that the cylinder in uniform or shear flow does not vibrate at low reduced velocities but vibrate significantly beginning at the reduced velocity around 5, initiated by vortex-induced instability. At high reduced velocity, the circular cylinder in shear flow still vibrates at significant amplitude, an evidence of fluid elastic vibration. It is also shown by the amplitude diagrams that low mass ratio promotes the cylinder’s vibration while large mass ratio reduces the vibration.
Influence of Ion Implantation on Tribo and Mechanical Behaviour of Duplex Hard Coatings
Authors: Skoric Branko , Kakas Damir , Miletic Aleksandar
Published: January 2011

In this paper, we present the results of a study of TiN films which are deposited by a Physical Vapor Deposition and Ion Beam Assisted Deposition. In the present investigation the subsequent ion implantation was provided with N2+ ions. The ion implantation was applied to enhance the mechanical properties of surface. In the nanoindentation technique, hardness and Young’s modulus can be determined by the Oliver and Pharr method. Indentation was performed with CSM Nanohardness Tester. The results are analyzed in terms of load-displacement curves, hardness, Young’s modulus, unloading stiffness and elastic recovery The analysis of the indents was performed by Atomic Force Microscope. The stress determination follows the conventional sin2 Ψ method, using a X-ray diffractometer. A variety of analytic techniques were used for characterization, such as scratch test, calo test, SEM, AFM, XRD and EDAX. Therefore, by properly selecting the processing parameters, well-adherent TiN films with high hardness can be obtained on engineering steel substrates, and show a potential for engineering applications. The experimental results indicated that the mechanical hardness is elevated by penetration of nitrogen, whereas the Young’s modulus is significantly elevated.
Natural Convection-Radiation Heat Transfer in Rectangular Cavity With the Presence of Participating Media
Authors: Moghadassian Behnam , Kowsary Farshad , Gholamian Hamed
Published: January 2011

The problem of natural convection radiation with the presence of participating fluid in a tilted square cavity has been investigated numerically. Two vertical walls are at uniform different temperatures while the others are adiabatic. The working fluid is taken as grey, absorbing, emitting and non-scattering. The finite volume method is used to solve the dimensionless governing equations and SIMPLE algorithm is applied for pressure velocity coupling. The radiative heat flux gradient is estimated by finding radiative intensities from the radiative transfer equation (RTE). A very recent method, called the QL method, is utilized to solve RTE. In this study the effects of the inclination angle, Rayleigh number and optical thickness on the heat transfer and flow characteristics are studied. A great accuracy in the results was observed in the prediction of flow contours and average radiative and convective Nusselt numbers at walls.
Effect of Ambient Pressure on Bubble Growth in Micro-Channel and Its Pumping Effect
Authors: Mobadersani F. , Eskandarzade M. , Azizi S. , Abbasnezhad S.
Published: January 2011

Over the last two decades, explosive boiling has been widely used in industry, many researches have been dedicated to study its aspects. Some applications of explosive boiling are in thermal bubble jet printers, micro-injectors and micro-medicine devices. In such applications ambient pressure is not usually the atmospheric pressure. To have a good design, there is a great need to simulate the bubble growth under non-atmospheric pressure. In this research a three dimensional numerical analysis of growth and collapse of a bubble in a micro-channel under four different ambient pressures is presented. Flow3D package which solves the Navier-Stokes equations with surface tension effects, is used to reach this aim. Leinhard’s equation is used to compute the temperature of explosive boiling in various pressures. It is considered that the internal pressure of the bubble has an exponential form. Bubble dynamics relations have been used to obtain time constant of the bubble. The bubble volume and the flow rates from both ends of the microchannel are obtained. It has been shown that increasing in the ambient pressure causes decreasing in the bubble volume. Numerical results for the growth and collapse of the bubble in the micro-channel are compared with those of experiments under similar conditions. Results of the growth and collapse of the bubble in the micro-channel of a printer, BJ-80, have been used to validation. Comparisons show that the bubble evolution is well predicted by the numerical results.
Tolerance Analysis: A New Model Based on Variational Solid Modelling
Authors: Marziale Massimiliano , Polini Wilma
Published: January 2011

In mechanical fields products are usually made by assembling many parts. The dimensional and geometrical variations of each part has to be limited by tolerances able to ensure their manufacture, assembling, interchange-ability and a certain level of product quality. The tolerance analysis is the fundamental tool to foresee the effects of the tolerances assigned to the single components on the whole assembly and to optimize its quality-cost ratio. This work presents a new tolerance analysis model able to overcome the limits of the actual ones. It is based on the variational solid modeling and on the simplified hypothesis that each feature maintains its nominal shape. Its application is general. It allows to perform analysis by both worst case and statistical approaches. It may consider all the tolerance kinds, the Envelope and the Independence principles, the interaction among the tolerance zones and the joints with clearance among the components.
Integrated Numerical and Experimental Study on the Thermal Management for LED Daytime Running Lamp
Authors: Lin Sheam-Chyun , Shen Ming-Chou , Cheng Kuang-Ting , Hong Jin-Tsing , Shih Hsien-Chang
Published: January 2011

The daytime running light (DRL) is a special lamp; they can be automatically switched on when the engine is started, and hence substantially increase the visibility of motor vehicles. Comparing to traditional light sources in DRL, LED offers many advantages such as its high lighting efficacy, low power consumption, quick response time, and long lifetime, However, the application of high brightness LED on DRL still faces severe thermal challenge in removing the unavoidable dissipation heat, which directly influences the radiation efficiency, emitted light quality, and lifetime of LED. Therefore, this investigation focuses on the thermal management for LED Daytime Running Lamp through an integrated effort of CFD simulation, CNC mockup fabrication, and experimental verification. At first, a comprehensive CFD simulation is executed to check the heat-removing performance of several thermal modules for identifying the efficient thermal design. Thereafter, this LED module integrated with a Zinc-Al alloy casing is fabricated via the die-casting and carried out the thermal performance measurements for experimentally validating the numerical outcomes. As a result, after taking the contact resistance and radiation into account, the comparison between numerical and experimental results indicates an acceptable deviation percentage within 5%. Also, experimental result shows that the LED junction temperature is located within the range of 50∼51°C for the case of a 2.34-Watt power input and a 35°C environmental temperature. Moreover, for a 10-Watt power input, the numerical calculation predicts that LED junction temperature is 88.6°C, which is still well below the safety limit (120°C). In conclusion, the accomplishment of this research offers a rigorous and systematic design scheme for the thermal management of the LED DRL. This design scheme has successfully produced an efficient thermal module to control the LED chip temperature below safety limit.
On the Design of a Micro Switch to Use as an Airbag Activator
Authors: Azizi Saber , Rezazadeh Ghader , Mobadersani Farrokh
Published: January 2011

The object of the present study is to design a micro switch witch activates the airbag of a car when the amplitude of the acceleration of the accident exceeds the critical one. The response time of the micro switch is supposed to be 5 ms. Micro switch consist of a proof mass connected to a clamped-clamped micro beam. The nonlinear partial integro-differential equation of the motion is solved using FEM. According to the results it is recommended to use micro switches instead of accelerometers as airbag activators in car’s safety systems.
A Low Cost Velocity Measurement System Design for Rotary Machinery
Authors: Cakir Cagatay , Koruk Hasan , Ulas Burak
Published: January 2011

Today, as the importance of system automation increases, measurement systems become more and more important. Consequently, in many applications, from washing machines, motorized vehicles, robots to nuclear turbine reactors, velocity measurement is inevitable. In industry, velocity is widespreadly needed to be measured. Besides that researchers through the globe need such measurement devices in their studies. On the other hand, to be able to make a correct measurement, it may be needed to pay much on measuring equipments while the economical issue is sometimes the reason for the research does not continue on or even not begin. So, it has always been a practical problem for both industry and researchers not to be able to measure the rotating velocity of machinery with both sufficient precision and low cost. In this paper, a very low cost but still precise velocity measurement system design is introduced, explained and discussed. First, building up of the sensor circuit and basic components of the system are introduced. Then, data acquisition and signal processing of the system are explained. Finally, advantages of the system are discussed and some conclusions are given.