bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Rheological Parameters in Blood-Endothelial Nano-Scale Interactions
Authors: Alshorman Abdullah A.
Published: January 2011

The performance of endothelium layer under the effect of blood shear force depends fundamentally on the rheological parameters of the blood flow, characteristic structure and physiological response of this lining layer to the shear effect. This includes the nano-scale geometry of blood cells and endothelium surface, shear rate and blood viscosity, in addition to endothelial mechanical properties. Principally, the elucidation of these nanoscale interactions will contribute the explanation and better understanding of cardiovascular diseases that are the main causes of death and health suffering for millions of people all over the world. As an attempt to build up a tangible contribution for this revelation, a simulation analysis has been performed to study the effects of blood shear stress and blood dynamic viscosity on the rate of attachment and detachment of blood over the endothelium layer in the form of adhesion and rolling. In particular, the nature of each effect has been determined and the numerical ranges for each parameter have been estimated for the physiological range of shear rates. The results reveal that shear rate G enhances the blood cell rolling starting from 20 s−1 up to 90 s−1 then it tends to have constant contribution regardless its value ever greater than 90 s−1. Likewise, higher and moderate blood viscosity μ (i.e., 0.5–2.5 cP) supports rolling up to 4 cP, then it starts to keep its influence constant similar to that of shear rate. However, lower μ enhances the enhances the steady rolling at low rolling velocity, which open a room for primary and/or permanent adhesion. The rolling starts at μ = 0.0.5 cP, then jumped to higher values when μ was increased. The effect of μ on rolling is similar to that of shear rate because of their jointed role in the hemodynamic force, such that the increase of both of them drives the cell for faster rolling up to maximum limit, then discontinue affecting. Fundamentally, the most effective biophysiological range of μ on cell rolling is 0.1–3.0 cP, which is suggested by this study and mainly used in the previous investigations. However, the most frequent used rang of μ was 1–2 cP.
Collaborative Determination of Task Implementation Priorities in Engineering Design
Authors: Tsokos Theodoros G. , Dentsoras Argyris J.
Published: January 2011

The present paper introduces a framework for the collaborative determination of design task implementation priorities according to design effort-based calculations. Hierarchical structures are used for representing associative dependencies among primary and dependent tasks. Design effort for task implementation is defined as function of various task-oriented issues such as designers’ experience, designers’ ability to fulfill task-related requirements, etc. Simple metrics are used to form a unified effort index for each individual task. Weighted collaborative determination of implementation effort for individual tasks is also studied. Weights are assigned to individual designers and a simple aggregation technique is used that provides overall values of effort indices for tasks when multiple designers are involved in the design process. A weighted dependency matrix so formed is further transformed through a number of operations based on the connectivity among the tasks and the intensity of effort index values. From the aforementioned matrix, a unique sorted list of primary tasks is produced that ensures that production of design information of maximum importance takes place with least effort during the early design stages and under completely realistic design conditions. A short design example contributes towards a better understanding of the proposed framework.
Combustion of Raw Algae Oil and Its Methyl Ester in a Diesel Engine
Authors: Haik Yousef , Selim Mohamed Y. E. , Abdulrehman Taher
Published: January 2011

An experimental study has been carried to use raw Algae oil and its methyl esters in an indirect injection diesel engine. Effects of engine speed, engine load output, injection timing of the algae biofuel and engine compression ratio on the engine output torque, combustion noise (maximum pressure rise rate), maximum pressure and maximum heat release rate have been studied. Raw oil extracted from microalgae and its methyl ester have been evaluated in a Ricardo E6 engine. It has been shown that the algae oil methyl ester’s properties are similar to diesel fuel and its use has been successful in running the diesel engine smoothly. However, its use reduced the engine output torque slightly and increased the combustion noise. Nonetheless, the engine output can be increased and the combustion noise can be reduced by controlling the engine design parameters e.g. injection timing and compression ratio.
Computational Study of a Target Fluidic Flowmeter
Authors: Nowakowski Andrzej F. , Nicolleau Franck C. G. A. , Salim S. M. Muztaba
Published: January 2011

The computational studies on the flow structure, design and performance of a target fluidic flowmeter have been carried out. The computational challenge was to find a universal approach to study a wide range of flow regimes. To this end the Detached Eddy Simulation (DES) approach for unsteady flows was applied. The numerical technique enabled to accurately reproduced three dimensional flow structures in a target fluidic flowmeter. The signal analysis of the obtained results was conducted for a range of Reynolds numbers from laminar case up to 4000. The results show that a number of factors such as meter geometry and aspect ratio can influence the performance of the flow meter significantly. A minimum Reynolds number constraint for the measurements to be accurate was evaluated for various design parameters. The significance of using knife edges which influence boundary layer separation was also established. The experimental data, which were obtained for a prototype of flowmeter setup were used to validate numerical tools in the important area of low Reynolds number flows.
Bending Analysis of Thin Skew Plates Using Extended Kantorovich Method
Authors: Kargarnovin M. H. , Joodaky A.
Published: January 2011

An accurate approximate closed-form solution is presented for bending of thin skew plates with clamped edges subjected to uniform loading using the extended Kantorovich method (EKM). Successive application of EKM together with the idea of weighted residual technique (Galerkin method) converts the governing forth-order partial differential equation (PDE) to two separate ordinary differential equations (ODE) in terms of oblique coordinates system. The obtained ODE systems are then solved iteratively with very fast convergence. In every iteration step, exact closed-form solutions are obtained for two ODE systems. It is shown that some parameters such as angle of skew plate have an important effect on results. It is shown that the method provides sufficiently accurate results not only for deflections but also for stress components. Comparison of the deflection and stresses at various points of the plates show very good agreement with results of other analytical and numerical analyses. Also, it has been shown that for skew angle less than 30° this method provides more accurate results and when the skew angle becomes greater than 30°, results gradually begin to deviate from those reported using other methods or by finite element softwares.
An Experimental Study on the Effect of Partition Angle on Free Convection Heat Transfer in a Partition Cavity by Laser Interferometry Method
Authors: Yousefi Tooraj , Mahmoodi Nezhad Sajjad , Bigharaz Masood , Ebrahimi Saeed
Published: January 2011

Steady state two-dimensional free convection heat transfer in a partitioned cavity with adiabatic horizontal and isothermally vertical walls and an adiabatic partition has been investigated experimentally. The experiments have been carried out using a Mach-Zehnder interferometer. The effects of the angel of the adiabatic partition and Rayleigh number on the heat transfer from the heated wall are investigated. Experiments are performed for the values of Rayleigh number based on the cavity side length in the range between 1.5×105 to 4.5×105 and various angle of the partition with respect to horizon from 0° to 90°. The results indicate that at each angle of the adiabatic partition, by increasing the Rayleigh number, the average Nusselt number and heat transfer increase and at each Rayleigh number, the maximum and the minimum heat transfer occur at θ=45° and θ=90°, respectively. A correlation based on the experimental data for the average Nusselt number of the heated wall as a function of Rayleigh number and the angel of the adiabatic partition is presented in the aforementioned ranges.
Natural Convective Characteristics of an Oblique Heat Source Module in the Closed and Ventilated Cabinets
Authors: Tsay Yeong-Ley , Cheng Jen-Chieh , Zhuang Yong-Lin
Published: January 2011

A numerical analysis is performed to study the characteristics of heat transfer from a block heat source module at different angles in two-dimensional cabinets. Great efforts are carried out to conduct the effects of thermal interaction between the air steams inside and outside the cabinet on the conjugate conduction–natural convection phenomena. Moreover, the enhancement of cooling performance of the heat source module through the construction of air vents on cabinet wall is rigorously examined. The computation domain covers the cabinet and the surrounding area, and the temperature and velocity fields of the cabinet and surrounding area are solved simultaneously. Results show that the thermal interaction between the airs inside and outside the cabinet, the module angle and vent position can significantly affect the transfer characteristics. Comparing the results for cases with and without the consideration of thermal interaction between the air streams, the difference in hot spot temperature of module can be up to 26% for Pr = 0.7, Kbf = Kpf = Kwf = 100, 105 ≦ Ra ≦ 107 and φ = 0°, 90°, 270°. The maximum reduction in hot spot temperature is about 41% when two air vents are constructed on cabinet wall. The variation of module angle results in the maximum difference of the hot spot temperature is 15% for closed cabinet, and 10% for ventilated cabinet.
Introduction to a Type of Resin-Reinforced Rapid Prototyping Transtibial Socket
Authors: Hsu L. H. , Lu C. T. , Huang G. F. , Chen J. T. , Chuang W. C. , Shih H. S.
Published: January 2011

This article introduced a type of rapid prototyping (RP) transtibial socket that is fabricated by a fused deposition modeling (FDM) machine and wrapped with a layer of unsaturated polyester resin (UPR) to enhance its flexural strength. As current rapid prototyping machines use a layer-based process to manufacture products, this will result in RP products liable to break along forming layers once bending moment is applied. To prevent RP prosthetic socket from breakage, this study proposed wrapping a layer of unsaturated polyester resin around a preliminary thin RP socket to reinforce its flexural strength. Factors affecting the strength of the resin-reinforced RP socket include thickness and forming orientation of the preliminary RP socket, thickness of the UPR layer, and type of material used to make the preliminary RP socket. Employing Taguchi experimental design method and ASTM three-point bending test standard, the parameters that influence the flexural strength of the resin-reinforced RP prosthetic socket can be determined. Based on the appropriate parameters, including thickness of the RP layer and UPR layer, the RP material and RP fabricating orientation, the preliminary thin RP prosthetic sockets can be fabricated by an FDM machine. And the thin layer preliminary RP sockets were then wrapped with cotton socks and laminated UPR layer to form resin-reinforced RP sockets. To confirm the effectiveness of the resin-reinforced sockets developed in this study, the pressures at residual limb/socket interface were measured by using a pressure distribution measurement system and movement was captured by a motion analysis system while a patient wears the resin-reinforced RP socket. Two resin-reinforced RP sockets have been fabricated and tested by a volunteer amputee. Analysis of the experimental results would assist a prosthetist to assess the distribution of interface pressures at the pressure-tolerant (PT) and pressure-relief (PR) areas of the residual limb. And, the gait pattern will be used to evaluate the applicability while the resin-reinforced RP socket is worn. Trial uses for durability test of the proposed RP socket are being arranged.
Performance Analysis of Absorption Chillers Using Data Reconciliation
Authors: Martinez David E. , Bruno Joan Carles , Bagajewicz Miguel J. , Coronas Alberto
Published: January 2011

Performance data obtained from measurements of process variables usually do not obey material and energy conservation laws. This is why a data reconciliation process, that is, the adjustment of measured data to obey the conservation laws and other constraints is necessary in order to characterize the real performance of equipment, processes, or the whole plant. The information on the partial load and off-design operation performance of absorption chillers is scarce. Real operation of these units do not always coincides with the expected performance according to the data provided by the manufacturer due to site specific conditions. On the other hand the data reconciliation procedure has been extensively applied mainly only for open cycles with a moderate number of recycle streams. The objective of this work is the development and application of the data reconciliation technique to analyse the performance of absorption chillers using rigorous thermodynamic properties for the calculation of the P-V-T equilibrium properties and enthalpies. We present in this paper the preliminary test results for one of the absorption chiller components, the evaporator.
LES Simulation of an Ultra-Micro Combustion Chamber Based on a 177 Reactions Mechanism
Authors: Minotti Angelo , Sciubba Enrico
Published: January 2011

Goal of this paper is to investigate the performance of microcombustors, a field currently under rapid development in particular for propulsion, e.g., UAVs and micro-electrical power generators. This study focuses on a cylindrical microcombustor fed by methane and air, with diameter and height 0.025m and 0.06m respectively. A 3D LES simulation with the WALE subgrid scale models, the EDC combustion-chemistry model and the reduced GRIMech1.2 mechanism has been performed. The calculated maximum temperature inside the chamber, the gas exhaust temperature and the combustion efficiency are compared and discussed. Reported results are at 0.05s, that is after 5 residence times. This ultra-microcombustor displays an excellent combustion efficiency which makes it a suitable for application in ultra-small energy producing devices. This work is part of a broader work that includes an experimental analysis, and it was conceived as a contribution towards a better understanding of the most convenient simulations guidelines for future microcombustor applications, and to a more accurate estimate of the performance parameters to apply to first-order design procedures.
Weak Radiator Design Using Dimples
Authors: Cheng Wen Nan , Cheng Chih Chun , Koopmann Gary H.
Published: January 2011

A design method for achieving minimum sound radiation from a beam is presented. The strategy is to form a series of cylindrical dimples on the beam surface in order to make one or more vibration modes of this dimpled beam have the same shape as the weak modes. Consequently, the dimpled beam behaves as a weak radiator when one or more vibration modes are excited. Instead of minimizing the radiated sound power at a specific frequency or in a bandwidth, the objective is to maximize the modal assurance coefficient (MAC) which quantifies resemblance between the vibration mode of a dimpled beam and a weak mode. To perform this strategy, two key issues are addressed in this paper. The first is to determine the so-called weak mode of a beam. And the second is how to determine the required dimple size and the dimple location on this beam so that the dimpled beam may have vibration modes resembled to the weak modes. A methodology to do so based on the finite element method and the mode assurance criteria is proposed. Results show that the radiation efficiency of the dimpled beam after optimization using MAC as the objective is generally lower than the uniform beam. However, the effectiveness of this strategy depends on how close in shape between the vibration mode of the dimpled beam and the designated weak mode.
Multi-Purpose Flexible Bodies Integration Into the Multi-Body System of a Metro-Vehicle
Authors: Saporito Guido , Baroni Alessandro , Romani Mario
Published: January 2011

The work points to study the effects of bodies flexibility concerning the Running Dynamics and Structural requirements and how such aspects could be integrated into a single design process of a mass transit vehicle in terms of Comfort, Safety, Track fatigue and Bogie-frame design. The multi-body system of the vehicle has been developed. The finite element model of the flexible bodies as car-body, wheel-set, bolster-beam and bogie-frame have been implemented. The critical but necessary step, in the integration process of the flexible body into a multi-body system, is the reduction of the finite element model of the body. For that reason an analytical verification in focused to validate the reduced FE-model with respect to the full FE-model has been thought, developed and implemented to provide a useful design tool; such an analytical verification aids the engineer to control and to optimize the reduction technique applied to the full-FE-model of the body. The validation procedure, which has been implemented, consists in developing an alter for the DMAP, Direct Matrix Abstraction Program of the FE-solver, and processing the output into a programming environment.
Temperature Measurement of Premixed Methane OEC Radially Symmetric Flame Jet Using Mach-Zehnder Interferometry
Authors: Ahmadi Mehran , Avval Majid Saffar , Yousefi Tooraj , Nasr Babak , Goharkhah Mohammad
Published: January 2011

The temperature field of a premixed methane/air symmetric laminar flame jet, under oxygen enriched conditions, is visualized by studying the interferogram of the flame, using Mach-Zehnder Interferometry. The flame is chosen to be both lean. For the lean flame, equivalence ratio was held constant at 0.5, and oxygen enrichment is adjusted to 0.5 and 0.6. And for rich combustion, equivalence ratio is chosen to be 1.2 while oxygen enrichment was 0.7 and 0.8. The Reynolds number is tried to keep unchanged at 500. In the present study a non-contact method is successfully developed to measure the temperature field of a premixed methane/air OEC radially symmetric laminar flame jet. The effect of oxygen enrichment on temperature field is also investigated and depicted.
Turbulent Flow Simulations Through Tarbela Dam Tunnels Considering the Effect of Sediment Particles
Authors: Abid Muhammad , Noon Adnan Aslam
Published: January 2011

The sediments inflow in the Tarbela reservoir is resulting in reduction in water storage capacity and damage to the tunnels carrying water to the power generating units and ultimately to the plant equipment. The turbulent flow in tunnel-2 of the Tarbela Dam Project (TDP) is analyzed for the sediment particles tracking in ANSYS CFX. The particles flow in the tunnel is considered random and striking the tunnel walls at different impact angles. Langrangian particles tracking approach is used for the particles deposition, which is a oneway coupling phenomena as the carrier phase is unaffected by the sediment particles because of particle mass loadings less than 0.2 and unaltered flow field. Reynolds Stress Model (RSM) is used for turbulent modeling as it takes care of anisotropic effects near the tunnel walls and is used in flows with strong curvature, swirling flows, flows with strong acceleration/retardation.
Fatigue Life Improvement of Antiroll Bar Bracket Used in Heavy Truck Suspension
Authors: Cinar Ali , Senocak Kader
Published: January 2011

Finite element analysis has been used widely in automotive industry to evaluate design alternatives. Especially when there is no prototype part for rig testing; CAE (Computer Aided Engineering) is the only tool to evaluate design whether it meets customer usage profile for the vehicles entire life. Antiroll bar bracket is used in heavy truck suspension which is mounted on the top of front axle & beneath the leaf spring squeezed with U bolts. Bracket has two attachment points for external loadings; antiroll bar & shock absorber. Modeling techniques used in finite element for stress analysis include assembly loads in addition to the external loads. Material & contact nonlinearities have been used for stress estimation. Alternative design is used to decrease stress level; and therefore increase fatigue life of the bracket. Rig testing has been used to determine fatigue life of bracket. Results for finite element & rig testing have been presented.
Simulation on Performances of Vertical Axis Wind Turbine
Authors: Chen Chien-Chang , Kuo Cheng-Hsiung
Published: January 2011

This study employs the commercialized computational fluid dynamics software (Ansys/Fluent), with the user’s defined technique, to simulate the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. This study addresses the effects of the collective variations of the pitch angle (within ± 10°) on the performance of the VAWT system. The results of the transient (acceleration) stage will be employed to evaluate the self-starting ability. While the vertical axis wind turbine (VAWT) reaches a steady rotating stage, the detailed flow structures, the vorticity fields, the pressure distributions around, and the forces on the airfoils at various azimuthal positions will be addressed. For the blades with a negative pitch angle (θ = −10°), has the peak value of the moment coefficient within one revolution is the largest which will provide the largest starting torque to drive the VAWT system more easily. However, in this case, the moment coefficients are negative within some part of the period. This cancels part of the positive moment within one revolution, thus the efficiency is reduced at this pitch angle. For the case with positive pitch angle (θ = 10°), the area under the moment coefficient curve is the smallest and the time elapse of large moment coefficient is relatively short. Thus the efficiency and the starting torque are the lowest among thee pitch angles.
Numerical Simulation of One-Dimensional Hyperbolic Heat Conduction Equation in Longitudinal Fins With Different Profiles
Authors: Bamdad Masouleh Keivan , Ahmadikia Hossein , Azimi Aziz
Published: January 2011

In this paper, the steady/unsteady heat conduction in the longitudinal fins with variable cross sectional area under the periodic thermal conditions is examined. Three different one-dimensional fins are considered and solved numerically by implicit finite difference method. In the hyperbolic equation the heat wave propagates with the finite speed hence the sharp discontinuities appear at the temperature distributions. In the explicit solution oscillations appear at discontinuity point which is greatly improved at the implicit method. In the present study temperature distributions are obtained for non-Fourier fins with different profiles. The effects of frequency of temperature oscillation, relaxation time and fin cross sectional area are studied on the temperature and location of the discontinuity of temperature. In order to validate the obtained results of the present study, these results have been compared to those of numerical solutions of the non-Fourier fin with constant cross sectional area. This comparison confirms the correctness of the current results.
On the Axisymmetric Torsional Wave Dispersion and Its Controlling in the Finitely Pre-Stretched Bi-Material Compound Circular Cylinder
Authors: Kepceler Tamer , Egilmez M. Mert
Published: January 2011

This paper investigates the dispersion of the torsional wave propagation in the finitely pre-strained bi-material compounded cylinder. This investigation is made within the framework of the piecewise homogenous body model with the use of the three dimensional linear theory of the elastic waves in initially stressed bodies. The mechanical relations of the materials of the components of the cylinder are described by the harmonic potential. The numerical results on the influence of the initial strains on the wave propagation velocity are presented and discussed. It is established in particularly that the initial stretching of the cylinders causes to increase the torsional wave propagation velocity.
Multi-Axial Fatigue Life Prediction of a Composite Structural Component
Authors: Vergani Laura , Colombo Chiara
Published: January 2011

Aim of this work is to test and understand the mechanical behavior of a composite material used to build a structural component, in particular a corner beam of a bus cabin. This component is obtained by means of the pultrusion technique and presents random and longitudinal E-glass fibers as reinforce, while the matrix is a vinyl-ester resin. A series of experimental tests was performed on specimens cut out from this beam. Different fibers orientation with respect to the direction of load application were considered: longitudinal (0°), normal (90°) and inclined (45°), thus both in uni-axial and multi-axial loading conditions. A static and fatigue characterization was carried out to identify the mechanical behaviors and the failure modes in these directions. Obtained fatigue data are then interpolated by fitting parameters required for models of fatigue life prediction.
A Combinatory Design Methodology Dedicated to the Ball and Roller Screw Drives for Optimum Design
Authors: Dupont Pierre
Published: January 2011

Machine-tools, packaging units, lifting systems and also other heavy duty devices (f.e. used in steel casting technologies) employ advantageously screw drives (balls, re-circulating rollers, and planetary roller drives) as mechanical command elements (f.e. directly coupled to servo drives), especially for their high efficiencies (∼87 .. 98%) and “output force to input torque ratio”. After a short review of the most important checks (for Static and Endurance Strength, Life, Shocks resistance and also some Miscellaneous Effects due f.e. to Critical Speeds and Stress Concentrators) it will be described briefly a combinatory design methodology or “heuristics” which takes into account as the technical viability and reliability as well as the economical feasibility of the whole system line (included end bearings and transmission) leading to an “overall safety ratio matrix” and/or to “viability and reliability graphs” helping in such a way the designer to reach an “optimum design” by an overall helicopter view of his/her design(s). In terms of optimization techniques, this user friendly combinatory design methodology could be placed in the field of the “heuristic” ones. An industrial case study will illustrate that presentation. This presentation is also a continuation of the one given for the MS&T’09 occurring in PITTSBURGH, USA during the “Charles R. MORIN Memorial Symposium on Failure Analysis & Prevention” for the ASM International.
Lattice Boltzmann Simulation of Non-Newtonian Flow Past Cylinders
Authors: Nejat Amir , Vahidkhah Koohyar , Abdollahi Vahid
Published: January 2011

A second-order lattice Boltzmann algorithm is used for power-law non-Newtonian flow simulation. The shear dependent behavior of the fluid is implemented through calculating the shear locally from the lattice distribution functions. The flow past a series of tandem arrangement of two cylinders is computed in a confined domain. The effect of Reynolds number and the power-law index on drag coefficients of the cylinders are examined in detail. The present study clearly reveals the capability of the lattice Boltzmann method in successful simulation of the complicated non-Newtonian flow fields.
Laser Microdrilling and Anodic Oxidation of Titanium for the Manufacturing of a Wettability Controlled Microvalve With UV/Dark Actuation
Authors: Demir Ali Go¨khan , Previtali Barbara , Bestetti Massimiliano
Published: January 2011

Capillary pressures due to the wetting behaviour of a liquid on a material can be exploited to control the pressure drop of the liquid into microchannels. The pressure can be estimated by the Young-Laplace equation and for a given liquid, high values can be achieved by having small microchannel diameters and high wetting contact angles. An original actuation method for a microvalve can be derived from this, if reversible wettability behaviour can be achieved, i.e. the switching between hydrophobic to hydrophilic states implies that the microvalve can be turned on and off. In the present work a wettability controlled microvalve with UV/dark actuation is proposed. The valve microchannels are obtained by laser microdrilling on commercially pure titanium foil. Then the drilled titanium foil is anodic oxidized to grow on the microchannel surfaces a nanostructured TiO2 layer, which exhibits reversible wettability behaviour upon the alternate application of UV and darkness. Finally, the concept is demonstrated in a prototype microvalve controlled between OFF and ON states by UV light application.
Pressure Drop Characteristics of Nanofluid Flow in a Horizontal Coiled Tube Under Constant Heat Flux
Authors: Akhavan-Behabadi M. A. , Hashemi S. M.
Published: January 2011

In the present study, an investigation of pressure drop characteristics of CuO-Base oil nanofluid laminar flow inside a horizontal helically coiled tube with constant heat flux boundary condition has been experimentally carried out. The nanofluid is prepared by dispersion of CuO nanoparticles in base oil and stabilized by means of an ultrasonic device. Particle weight fraction is ranging from 0 to 2%. The uniform and constant heat flux produced by an electrical heating coil wrapped around the coiled tube. The required data were acquired for laminar fully developed regime. The effect of different parameters such as fluid temperature, nanofluid particles concentration and mass velocity on the pressure drop characteristics in helically coiled tube for laminar fully developed regime is investigated. The results show that by using the helically coiled tube instead of the straight one, the pressure drop is increased. Also, the pressure drop increasing is happened by using nanofluid instead of base fluid. However, this increase is small compared to the increase resulted by using helically coiled tube. Observations also show that by increasing of mass velocity and concentration of nanoparticles in nanofluid, the pressure drop increasing is more pronounced.
Effect of Sintering Temperature on the Tribological Behavior of Plasma Assisted Debinded and Sintered MIM Self Lubricating Steels
Authors: de Mello Jose´ Daniel B. , Binder Cristiano , Klein Aloisio Nelmo , Binder Roberto
Published: January 2011

Solid lubrication and solid lubricants are one of the most promising choices for controlling friction and wear in energy efficient modern systems. The production of self lubrication composites containing second phase particles incorporated into the volume of the material appears to be a promising solution. A new processing route to obtaining a homogeneous dispersion of discrete solid lubricant particles in the volume of sintered steels produced by metal injection molding (MIM) was recently presented. This new route was achieved by in situ formation of graphite nodules due to the dissociation of precursor (SiC particles) mixed with the metallic matrix powders during the feedstock preparation. Nodules of graphite (size ≤ 20μm) presenting a nanostructured stacking of graphite foils a few nanometers thick were obtained. The thermal debinding, as well as the sintering, was performed in a single thermal cycle using a Plasma Assisted Debinding and Sintering (PADS) process. In this work, we present and discuss the effect of sintering temperature on the tribolayer durability and average friction coefficient in the lubricious regime (μ<0.2) of plasma assisted debinded and sintered self lubricating steel produced by metal injection mould technique. Three different temperatures (1100, 1150 and 1200 °C) and six different SiC contents (0–5%) were analyzed. Friction coefficient was little affected by the sintering temperature. However, the durability of the tribo layer formed on the sliding interface was greatly increased (5X) for the lower sintering temperature (1100°C).
Design and Experimental Validation of a Hardware-in-the-Loop Simulator for Mechanisms With Link Flexibility
Authors: Boscariol Paolo , Gasparetto Alessandro , Zanotto Vanni
Published: January 2011

The aim of this paper is to demonstrate the capabilities and potential of a Hardware-In-the-Loop (HIL) simulator for the tuning of closed-loop control strategies used in flexible-links mechanisms. HIL is an increasingly popular methodology used in reducing the design and validation time of complex systems. This approach makes use of a software-programmed hardware prototype of the device under test, which is able to interact with other hardware devices and real-world signals. In this paper a validation of the proposed simulator, named FLiMHILS (Flexible Link Mechanisms HIL Simulator), will be obtained by comparing the dynamic behavior of a real single-link mechanism with the corresponding response of the simulator subject to the same stimuli and controller parameters. The experimental results show how the tuning parameters obtained with the HIL simulator can be successfully used to control the real mechanism. The real-time capable model which constitutes the core of the HIL simulator is a highly accurate FEM-based nonlinear model capable of describing with consistency the dynamics of different planar mechanisms with flexible links.
Optimal Path Planning for Painting Robots
Authors: Gasparetto A. , Vidoni R. , Saccavini E. , Pillan D.
Published: January 2011

In this work, a robotic painting task is addressed in order to automate and improve the efficiency of the process. Usually, path planning in robotic painting is done through self learning programming. Recently, different automated and semi-automated systems have been developed in order to avoid this procedure by using a CAD-drawing to create a CAD-guided trajectory for the paint gun, or by acquiring and recognizing the overall shape of the object to be painted within a library of prestored shapes with associated pre-defined paths. However, a general solution is still lacking, which enables one to overcome the need for a CAD-drawing and to deal with any kind of shapes. In this paper, graph theory and operative research techniques are applied to provide a general and optimal solution of the path planning problem for painting robots. The object to be painted is partitioned into primitives that can be represented by a graph. The Chinese Postman algorithm is then run on the graph in order to obtain a minimum length path covering all the arcs (Eulerian path). However, this path is not always optimal with respect to the constraints imposed by the painting process, hence dedicated algorithms have been developed in order to generate the optimal path in such cases. Based on the optimal path, the robot trajectories are planned by imposing a constant velocity motion of the spray gun, in order to ensure a uniform distribution of the paint over the object surface. The proposed system for optimal path planning has been implemented in a Matlab environment and extensively tested with excellent results in terms of time, costs and usability.
Development of a Computer Program for the Numerical Investigation of Heat Transfer in a Gasketed Plate Heat Exchanger
Authors: Gulben Gizem , Aradag Selin , Sezer-Uzol Nilay , Atamturk Ufuk
Published: January 2011

In this study, a computer program is developed to calculate characteristics of a Chevron type gasketed plate heat exchanger (CTGPHEX) such as: the number of plates, the effective surface area and total pressure drops. The main reason to prefer the use of CTGPHEXs to other various types of heat exchangers is that the heat transfer efficiency is much higher in comparison. Working conditions such as the flow rates and inlet and outlet temperature of both flow sides and plate design parameters are used as an input in the program. The Logarithmic Mean Temperature Method and the different correlations for convective heat transfer coefficient and Fanning factor that are found in the literature are applied to calculate the minimum necessary effective heat transfer area, the number of plate and pressure drops due to friction for both fluid sides of fulfill the desired heat transfer rate. This Turkish / English language optioned user friendly computer program is targeted to be used in domestic companies to design and select CTGPHEXs for any desired working conditions.
Application of Tuned Mass Dampers and Lever Type Vibration Isolator to the Quarter-Car Model in Order to Increase Ride Comfort
Authors: Aydan Go¨ksu , Cig˘erog˘lu Ender , Bas¸lamıs¸lı S. C¸ag˘lar
Published: January 2011

In this paper, performance of passive vibration isolators, namely rotational / linear tuned mass dampers (TMD) and lever type vibration isolators (LVI), are investigated under different configurations for optimal ride comfort. TMDs reduce vibration levels by absorbing the energy of the system, especially around natural frequencies with the help of viscous dampers. Two types of TMDs, rotational and linear, are investigated in this study. Although linear TMDs can be more easily implemented on suspension systems, rotational TMDs show better performance in reducing vibration levels. The reason is that, the inertia effect of rotational TMDs is higher than linear TMDs. In order to obtain better results with TMDs, a study on different possible configurations is conducted. A plate, with very small mass, is added between sprung and unsprung masses without changing the original suspension spring stiffness and damping coefficients and acts as a support for in-series TMD applications. Finally, LVIs are implemented to reduce sprung mass acceleration and more satisfactory results are obtained especially around body bounce frequency.
Mechanical Design and Prototyping Considerations for an Intramedullary Nail for Extending Bone Sections
Authors: Okyar A. Fethi , Safak Koray K. , Egrican Nilufer
Published: January 2011

An orthopedic distractor device is currently being developed for extending bones or bridging a gap in a bone. The device is designed to fit into the medullary canal of a human femur or tibia. By virtue of telescopic motion between two mating parts, the device can extend axially inside a dissected bone, elongate it to desired length. The distractor is actuated by means of a miniature electrical drive system, which is energized and controlled from outside of the body without any direct physical connection or cabling. In this study mechanical design and prototype manufacturing considerations of the intramedullary distractor device are discussed. An important limitation in design of this device is the availability of a suitable drive system that will fit into the intramedullary space of the bone, which has a diameter of less then 12 mm. The nail must withstand axial forces with a magnitude of 2000 N, which is exerted by extending the muscles, especially during the late stages of the distraction operation. Since the designed device is intended to be used inside the human body, proper insulation from the surrounding body fluids must be provided, thus sealing is also an important design consideration. A preliminary design is presented that will achieve the desired requirements.
Controllability and Maintenance of Human Trunk Response Surface for Isometric Extension Strength
Authors: Azghani M. R. , Farahmand F. , Meghdari A. , Hakkak F. , Parnianpour M.
Published: January 2011

From an ergonomic point of view, quantitative assessment of the feasibility of the task performance is an intricate process, which combines the multidimensional task demand profile with the individual’s multidimensional performance capacity profile. Trunk muscle strength is affected by the trunk posture but it is not clear how the variability of trunk muscle is affected by the trunk posture or exertion level. A validated triaxial dynamometer, Sharif-LIST, was used for to model the surface response of trunk muscle extension strength variability as a function of trunk posture in the sagittal, coronal and transverse planes in standing position. Fifteen healthy males with no history of low back pain in the previous year participated in this study. A full factorial method was used to design the experiments to fit a second-order model of response surface method (RSM) with block effect (BE). For the first time in the literature, the results of this study indicate that the quadratic RSM model is suitable to represent the trunk extension strength variability in terms of its coefficient of variation (CV) and standard deviation (SD) of maximum trunk torque as a function of trunk posture in coronal and sagittal planes (R2 = 0.6, p<0.5). These results showed that in the positions with higher trunk strength values, the higher standard deviation and lower coefficient of variation were observed which is consistent with previous findings.
Dynamic Analysis of a Hula-Hoop System
Authors: Lu C. H. , Sung C. K.
Published: January 2011

This paper presents a theoretical and experimental study into the dynamics of a hula-hoop system, in which a free-rotating mass mimicking the ring is hinged on a main mass that simulates the human body and performs translational reciprocating motion under external excitations. The physical model of the hula-hoop system was first constructed and the equations governing the motions of the main mass and the free-rotating mass were, then, derived. The approximate steady-state solutions were obtained by employing homotopy perturbation method and the stabilities of which were analyzed by using Floquet theory. Good agreement between the results obtained from stability analysis and numerical simulation implied that the approximate solutions were adequate for the dynamic analysis of the proposed model. Finally, an experimental rig consisting of a semicircular thin plate hinged on the top of a linear-motor stage was devised to mimic the hula-hoop motion based on the analytical analysis.
Medical Rapid Prototyping and Manufacturing: Status and Outlook
Authors: Alabey Peristera , Pappas Menelaos , Kechagias John , Maropoulos Stergios
Published: January 2011

Rapid Prototyping (RP) has been considered, over the last decades, as a highly promising technology for reducing product development time and cost, as well as for addressing the need for customization and faster response to the market needs. Nowadays this technology is also used widely in medical applications (Medical Rapid Prototyping – MRP), supporting diagnosis and treatment in Neurosurgery, Orthopedic and Dental-Cranio-Maxillo-Facial surgery as well as in Tissue Engineering. The scan data that are usually obtained by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) are used to build a 3D CAD model of the patient’s pathological region. The 3D model is used to construct the real size prototype using one of the existing RP processes. This assists surgeons in gaining a detailed insight of the problem, making the diagnosis and treatment easier and more reliable. This study presents the current benefits and barriers of Rapid Prototyping and Manufacturing methods and applications in the field of medicine. Most of the recent state-of-art developments and case studies of MRP are presented. Their limitations are discussed along with the challenges to be addressed in the future.
Steam Turbine’s Damage Assessment
Authors: Al-Tuwaijri Jasem
Published: January 2011

A turbo generator unit at Al-Khobar power and desalination plant (7 years old) was unable to start due to high vibration. Vibration trend increasing was noticed in the beginning of 2006 and inflated in 2007 due to unbalance which came to acceptable limits after rotor low speed balancing. Fortunately, this inspection prevented a complete damage of turbine due to detached of casing’s top pressure sensor’s sleeve which was digging into nozzle box body and created a big hole and was few millimeters from the rotor. Site repair was done for the nozzle box as per OEM procedure and sensor was omitted since it is not related to control system. In addition, both journal bearings were getting discoloration and pitting in left side due to selected operation mode of steam admission (partial arc mode) which shifting axis of rotation to left side by 30 μm and increases vibration reading compare to full arc mode. Also, another unit found with similar problems which seems to be a design issue. So an assessment study was done to evaluate the design.
Trajectory Planning of Spine Motion During Flexion Using a Stability-Based Optimization
Authors: Khorsand Vakilzadeh Majid , Salarieh Hassan , Asghari Mohsen , Parnianpour Mohamad
Published: January 2011

A central problem in motor control is to understand how the many biomechanical degrees of freedom are coordinated to achieve a goal. A common assumption is that Central Nervous System (CNS) would minimize a performance index to achieve this goal which is called objective function. In this paper, two popular objective functions are utilized to design the optimal trajectory of trunk movements. A 3D computational method incorporated with 18 anatomically oriented muscles is used to simulate human trunk system. Inverse dynamics allows us to compute torque which is generated around Lumbosacral joint. This torque is divided among muscles by static stability-based optimization. Trunk movement from the upright standing to 30 degrees of flexion is simulated based on this method. Incorporation of the stability condition with the static optimization resulted in an increase of antagonistic activities which would increase the joint stiffness around the Lumbosacral joint in response to gravity perturbation. Results would shed light on the interaction mechanisms in muscle activation patterns, seen in various performance indices.
The Efficiency of Geothermal Heat Pumps With Vertical Ground Heat Exchangers: A Simulation Under Iraqi Conditions
Authors: Antwan Nazar F. , Maree Iyd E.
Published: January 2011

Geothermal heat pumps with ground source heat exchangers have been widely used for heating and cooling homes as well as for domestic water heating. A study on a small house in Erbil-Iraq was conducted to assess energy savings when using GHPs with closed loop ground source heat exchangers as compared with air-to-air heat pumps. Local climate conditions and soil properties of Erbil located in the north of Iraq were used. The simulation was performed using TRNSYS-16 software. The results of this study show that we can reduce the energy used for heating and cooling by 39% during annual when using GHP. The simulation also showed that the average COP for heating is 2.9 and for cooling is 2.6 when using air to air heat pumps and the average COP for heating is 5.6 and 3.6 for cooling when using GHP. This reduction in energy reduces the CO2 emission as it reduces energy consumption.