bluuebunny/crossref_metadata_2025 huggingface dataset:
An Efficient Localized RBF Meshless Method Applied to FLuid Flow and Conjugate Heat Transfer
Authors: Divo Eduardo , Kassab Alain J.
Published: April 2008

A localized radial basis function (RBF) meshless method is developed for coupled viscous fluid flow and convective heat transfer problems. The method is based on new localized radial-basis function (RBF) expansions using Hardy Multiquadrics for the sought-after unknowns. An efficient set of formulae are derived to compute the RBF interpolation in terms of vector products thus providing a substantial computational savings over traditional meshless methods. Moreover, the approach developed in this paper is applicable to explicit or implicit time marching schemes as well as steady-state iterative methods. We apply the method to viscous fluid flow and conjugate heat transfer (CHT) modeling. The incompressible Navier-Stokes are time marched using a Helmholtz potential decomposition for the velocity field. When CHT is considered, the same RBF expansion is used to solve the heat conduction problem in the solid regions enforcing temperature and heat flux continuity of the solid/fluid interfaces. The computation is accelerated by distributing the load over several processors via a domain decomposition along with an interface interpolation tailored to pass information through each of the domain interfaces to ensure conservation of field variables and derivatives. Numerical results are presented for several cases including channel flow, flow in a channel with a square step obstruction, and a jet flow into a square cavity. Results are compared with commercial computational fluid dynamics code predictions. The proposed localized meshless method approach is shown to produce accurate results while requiring a much-reduced effort in problem preparation in comparison to other traditional numerical methods.
Thermophysical Properties of Biporous Sintered Copper
Authors: Lin Ying-Yu , Semenic Tadej , Catton Ivan
Published: April 2008

Thermophysical properties of bidispersed (biporous)-sintered copper are measured. An apparatus to measure effective thermal conductivity of dry samples is built. It is calibrated using bulk samples with known thermal conductivity. Permeability is measured based on flow resistance though the porous samples. Velocity at different pressure drops is measured and the permeability calculated using Darcy’s law. The experiment is performed using silicone oil as working liquid. The error of the method is less than three percent. Capillary pressure for all samples is measured based on amount of liquid that is held by the porous sample. The Young-Laplace relationship is used to relate capillary pressure to effective pore radius. Porosity of the samples is measured using density method. According to the measurement results, effective thermal conductivity of biporous samples is much lower than for comparable monoporous samples. Permeability and porosity of biporous samples are much higher than the monoporous samples. Capillary pressure of the biporous samples is very close to the one measured for the monoporous samples.
Effect of Inlet Air Cooling by Absorption Chiller on Gas Turbine and Combined Cycle Performance
Authors: Khaledi Hiwa , Zomorodian Roozbeh , Ghofrani Mohammad Bagher
Published: April 2008

Gas turbine performances are directly related to site conditions. The use of gas turbines in combined gas-steam power plants, also applied to cogeneration, increases such dependence. In recent years, inlet air cooling systems have been introduced to control air temperature at compressor inlet, resulting in an increase in plant power and efficiency. In this paper, the dependence of outside conditions for a simple gas turbine and a combined cycle plant is studied, using absorption chiller as inlet air cooling system. We used, as case study, a simple plant equipped with one frame E gas turbine and a combined cycle with a two pressure level heat recovery steam generator (HRSG). It was found that inlet air cooling with absorption chiller has great positive influence on power and less on efficiency of the gas turbine plant. Two steam sources (External and Internal) have been considered for chiller. External source has large positive influence on power but keep the efficiency of the combined cycle unchanged, while internal source causes a reduction in steam turbine mass flow. Consequently power production and efficiency of the combined cycle decrease. This reduction is lower in mid temperature (25 to 35°C) but higher in high temperature (35 to 45°C). Inlet cooling would result in lowering turbine exhaust temperature, thus decreasing the efficiency of HRSG.
Development of the Surgery Recorder System
Authors: Ikuta Koji , Kato Takashi
Published: April 2008

An important concept of the Surgery Recorder System (SRS) for minimally invasive surgery (MIS) is proposed. With wide spread of public interest in rapid recovery from surgical diseases, MIS has been increasing the number of clinical cases. Then the risk of clinical accidents will also be raised for a reason that shortage in supply of standard clinical treatments will lead to complications or mortal cases associated with misjudgments of surgeons. Actually, specific accidents in MIS have been increasing, but there is no efficient methodology of quantitative analysis for accidents, even the standard format for surgical record including operative procedure. Therefore, we developed SRS, which give clinical review process an objective way of identifying the causes of accidents. SRS is meant to be the “flight recorder” in the operating theater. SRS records surgery information including position/orientation (P/O) and force/torque (F/T) signals of surgical tools, an endoscopic vision and surrounding sounds in the operating theater (A/V information). A prototype of laparoscopic forceps for P/O and F/T sensing was newly developed with care for consistency with commercial forceps. Then, in-vivo pig experiments were also performed by an expert of laparoscopic surgery for testing SRS. False and rough operative approaches to diaphragma and liver by a skillful surgeon were analyzed quantitatively in a postoperative investigation.
Correlations of Characteristics of Waves on a Film Falling Down on a Vertical Wall
Authors: Koizumi Y. , Enari R. , Ohtake H.
Published: April 2008

Behavior of a liquid film flows down counter-currently on the inner surface of a circular pipe was examined. In experiments, silicon oils of 500, 1000 and 3000 cSt as well as water were used as the liquid phase. The gas phase was air. A test section vertically oriented was a circular pipe of 30 mm in inner diameter and 5.4 m in length. The substrate thickness of the silicone film, where the film Reynolds number was quite low, was close to the mean film thickness while the water film substrate was much thinner than the mean film thickness. Waves were on the substrate. It was confirmed that there were waves with some certain amplitude even on the silicone films near the flooding occurrence where the film Reynolds number was quite low. The mean film thicknesses of silicon films as well as the water film were well expressed by applying the universal velocity profile to the film flow. When the film Reynolds number was lower than 600, the wave velocity was well predicted as the velocity of small perturbation waves on the laminar film. As the film Reynolds number becomes large, the wave velocity becomes slower than the small perturbation wave velocity. The correlation for the wave length was developed based upon the present experimental results. Combining it with the Nosoko correlations and modifying constants and exponents, new correlations for the wave velocity and the maximum film thickness were proposed. The correlations could predict these within 15% accuracy.
Dynamic Analysis of Composite Plates
Authors: Sorohan Stefan , Parausanu Ioan , Motomancea Adrian , Caruntu Dumitru I.
Published: April 2008

The paper presents comparatively the measured and estimated natural frequencies and mode shapes of a rectangular orthotropic panel. The experimental tests were performed using a shaker. The plate was fixed in horizontal position directly on the shaker armature using a rigid rod. The experimental modes shapes were visualized using sand particles. The measured natural frequencies and also the modes shapes correspond to the whole system in motion. So, the analytic model of the plate must include the effect of the vibrator connected to the plates. The purpose of this experimental measurements and analytic modeling of such plates is to further developing a methodology to estimate the material properties of the composite panels. At this research stage, an orthotropic plate with unknown material properties was investigated. Using an adequate finite element model, the mechanical properties of the material were estimated. Using these properties it is possible to numerically estimate the dynamic behavior of the plate for additional sets of boundary conditions.
The Thermodynamics of Combined Electrical/Mechanical and Thermal Power Producing Systems
Authors: Adebiyi G. A.
Published: April 2008

A combined electrical/mechanical and thermal power generating system is undoubtedly the way to go for optimum overall efficiency in energy conversion. Traditionally, electric power is generated in centralized power stations and subsequently supplied to consumers via extensive grid distribution networks. Waste heat is a by-product that cannot inexpensively be conveyed to meet the demand for thermal power in the communities served. Consequently, the needed thermal power is produced either using the high grade electricity delivered from the grid supply, or by combustion of expensive fuels such as natural gas and oil. Cogeneration and CHP (Cooling, Heating, and Power) systems are designed to utilize waste heat from in-house electrical/mechanical power producing devices such as micro turbines and diesel engines used in industries that are located in the community or district. The generation of mechanical and thermal power from a single fuel input significantly enhances the overall conversion efficiency, which translates to lower CO2 emissions to the environment. Greater stability and reliability in power supply at the community level is achieved via the deployment of CHP systems that provide power on the required scale as well as meet local demand for cooling and/or heating. The magnitude of efficiency gain for CHP systems is often overstated simply because the quality difference between electrical/mechanical power and thermal power is not factored into the equation. This paper focuses on a complete thermodynamic analysis of CHP systems on the basis of the first and second laws of thermodynamics.
Influence of Nonideaities on the Performance of a Self-Balancing Rotor System
Authors: Horvath Roland , Flowers George T. , Fausz Jerry
Published: April 2008

An analytical, numerical and experimental investigation of the dynamic behavior of a four degree of freedom passive balancing system using pendulum balancers is presented. This work is an extension of previous studies which considered such automatic balancing systems and devices. It has previously been demonstrated analytically that a 4-DOF pendulum self-balancing system is capable, under idealized conditions, of exact radial balancing [10]. However, imperfections in the fabrication and assembly of such a system tend to compromise a number of the ideal modeling assumptions that were used to provide this result. The present research study examines the effects of a variety of such imperfections and their influence on the functional capability of the self-balancing system. Both analytical/simulation results and experimental validation are provided and discussed.
MR Compatible ERF Driven Hand Device for Rehabilitation After Stroke
Authors: Khanicheh Azadeh , Muto Andrew , Triantafyllou Christina , Weinberg Brian , Astrakas Loukas , Tzika Aria , Mavroidis Constantinos
Published: April 2008

This paper presents the design, fabrication and testing of a novel, one degree of freedom, magnetic resonance (MR) compatible, computer controlled, variable resistance hand device that will be used in fMRI studies of the brain and motor performance during rehabilitation after stroke. The device consists of four major subsystems: a) the Electro-Rheological Fluid (ERF) resistive element; b) the gearbox; c) the handles and d) the sensors: one optical encoder and one force sensor was implemented into the device design to measure the patient induced motion and force, respectively. A key feature of the device is the use of electro rheological fluids (ERF) to achieve resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. Using the electrically controlled rheological properties of ERFs, compact resistive elements with an ability to supply high resistive torques in a controllable and tunable fashion, have been developed. The hand device is designed to resist up to 50% of maximum level of gripping force of a human hand and be controlled in real time. Our study demonstrates that there is neither an effect from MR environment on the ERF properties and performance of the sensors, nor significant degradation on MR images by the introduction of ERF driven hand device in the MR environment. The results are encouraging in combining functional Magnetic Resonance Imaging methods, with MR compatible robotic devices for improved effectiveness of rehabilitation therapy.
Heat Transfer Characteristics in Mist Cooling With Machining Oil
Authors: Ohtake Hiroyasu , Tanaki Tomoyasu , Koizumi Yasuo
Published: April 2008

Heat transfer characteristics in mist cooling with commercial machining oil were investigated experimentally. Steady state experiments of heat transfer were conducted using a pure copper cylinder and mist flow of commercial machining oil and air. Liquid flow rate was 0.3, 0.9, 1.8, 4 and 8 l/hr, respectively; each air flow rate was 0, 40, 75 and 120 lN/min. Furthermore, liquid mass flux on the heating surface for each experimental condition was measured by using a measuring cylinder with same diameter as the heater. Average velocity of droplets and average diameter of those were measured by using a laser doppler anemometer and immersion method, respectively. The heat transfer mechanism in oil mist was only cooling of liquid film formed on a heated surface, whereas the heat transfer mechanism in water mist cooling was classified into three regions. The heat transfer coefficient in the oil mist was well expressed by the heat removal capacity on sensible heat of supplying oil-droplets to the heated surface. Four dimensionless correlations were derived from a dimension analysis, Buckingham Pi theorem, and experimental data for both water mist and the oil mist.
Weld Cooling-Rates and the Onset of Failure During “In-Service” Welding of Gas Pipelines
Authors: Wahab M. A. , Sabapathy P. N. , Painter M. J.
Published: April 2008

Welding onto a live-gas pipeline (In-service welding or hot-tapping) is employed in the repair, modification or extension of gas pipelines and has significant economic advantages for the gas-transmission industry since it avoids the costs of disrupting pipeline operation and secures continuity of supply; and used in pipeline maintenance such as the installation of sleeves around damaged sections and direct deposition of weld-metal onto an active pipe to replenish wall thickness lost through corrosion or local damage of the gas pipelines. Unfortunately, the flowing gas results in an accelerated cooling of the weld; and secondly, the localized heating and loss of material strength during the welding process, since the pipe-wall may burst under internal pressure if this reduction in strength becomes too critical. The useful role of numerical simulation of ‘in-service’ welding has been demonstrated by earlier work (i.e. work of EWI & BMI, and Goldak & Others—1992) that applied a general 3D-finite element method to calculate the thermal fields for circumferential fillet and direct-branch welds. Earlier, current authors developed a preliminary burn-through model of ‘in-service’ welding and in this work the authors have attempted to increase the accuracy of thermal prediction.
Thermal Model for the AC Armature Winding of a High Temperature Superconductor Airborne Motor
Authors: Morega A. M. , Ordonez J. C. , Vargas J. V. C.
Published: April 2008

This paper describes a preliminary study on a cooling concept for an airborne high performance synchronous motor that has a High Temperature Superconductor (HTS) field winding: whereas the rotor is actually an HTS DC field winding, the armature is an AC copper winding, mounted in an iron-less stator — a so-called “air winding”. The efforts aimed at prototyping a low weight/volume motor lead to a dedicated thermal design where an important role is played by the thermal management of the AC winding, which is the siege of intense power dissipation by Joule and variable magnetic field effects. The analysis reveals thermal constraints that are overlooked by the initial, first stage electromagnetic design and that need to be addressed. The thermal analysis reported here is based on equivalent, lumped thermal circuits: (a) a simplified circuit, aimed at delivering fast, design class results, that may be solved analytically; (b) more complex schemes aimed at assessing variable regimes, which are solved numerically by a circuit simulator. Both approaches are valuable, and complement each other in the quest for a meaningful preliminary design.
Integrated Reliability Solutions for New Component Development and Designs Optimization
Authors: Wu Xiaohua , Qian Zhengfang , Wang Yinyan
Published: April 2008

New engine control module products require most reliable, smallest pad size for new 0402 leadless components implementation. Cycle time and cost reduction is the major demand in the new product prototype development and design of experiments. An integrated quality and reliability modeling methodology has been applied for evaluating the new leadless component pad stack designs in PWB/Rigidizer engine module products for optimal process solderability and reliability performance. Simulations combine analyses of process defect root cause, high volume manufacturability, and thermal fatigue life to derive optimal design solutions of pad stack and manufacturing process requirement. This integrated quality and reliability simulations has enabled a significant cycle time reduction by performing virtual design of experiments for the new component pad stack designs.
An Investigation on Thermocouple-Based Temperature Measurements in Sooting Flames
Authors: Ergut A. , Levendis Y.
Published: April 2008

Temperature is an important parameter in flame chemical structure calculations. However, accurate temperature measurements are challenging to obtain. This manuscript reports on temperature measurements in sooting ethyl-benzene flames. Measurements were conducted with an array of four decreasing size thermocouples. However, to minimize disturbance of the flame by the insertion of the insulated multi-thermocouple array, the four thermocouples were also inserted bare one at a time, and results were contrasted. In both cases, radiative heat transfer was accounted for by using the well-known Nichols method [1]. This method was somewhat modified, as the extrapolation to zero thermocouple bead size was done using third-order polynomials. Furthermore, as soot accumulates on the thermocouple beads, upon their insertion in sooting flames, the obtained signals were scrutinized to determine the point in their time-history that is appropriate for this analysis. The zero time extrapolation technique, as suggested by McEnally et al. [2], was used to correct for soot accumulation at the tip of the thermocouples. Other methods were also explored, where theoretical expressions were used with corrections applied for the radiative heat losses from the thermocouples either prior or after the accumulation of soot on the thermocouple bead. Results showed that higher temperatures were recorded when single bare thermocouples were inserted into the flame as compared to inserting four thermocouples together. The difference was attributed to the disturbance of the flow-and temperature-fields in the flame, especially by the ceramic sheath that holds thermocouples together, and the thermal interaction of the thermocouples when they were inserted into the flame simultaneously. Results also showed that a combination of modified Nichols’ method with McEnallys’ corrections for sooting flames is a preferred technique as it nearly eliminates assumptions. Resulting temperature values are supported by theoretical calculations with judicious assumptions on important parameters.
Fluid Effects in Small Gaps: A Challenge for Sensor Application
Authors: Stammen C.
Published: April 2008

This paper is motivated by the difficulty of pressure distribution measurement in the small gap between valve spool and housing or sleeve. The research project “Design of Balancing Grooves for Hydraulic Valves using Analysis of Flow and Pressure Distribution” at IFAS aims at providing a design tool for balancing grooves. It is based on the idea that the application of modern simulation techniques together with experimental results enhances knowledge about necessity and design of balancing grooves. Main influence on the pressure distribution is the gap height profile. Although valve spool and sleeve can be examined separately, it cannot be concluded to the geometrical information about the gap between these parts as accurate as needed to verify the simulation model. The paper describes the development of miniature pressure sensors made of manganin wire. Measurements showing the current results are presented. As an outlook, the integration of gap height measurement into the pressure sensors is proposed.
Regulation of G2/M Transition in Mammalian Cells by Oxidative Stress
Authors: Li G. , Nair S. S. , Lees S. J. , Booth F. W.
Published: April 2008

The regulation of the G2/M transition for the mammalian cell cycle has been modeled using 19 states to investigate the G2 checkpoint dynamics in response to oxidative stress. A detailed network model of G2/M regulation is presented and then a “core” subsystem is extracted from the full network. An existing model of Mitosis control is extended by adding two important pathways regulating G2/M transition in response to DNA damage induced by oxidative stress. Model predictions indicate that the p53 dependent pathway is not required for initial G2 arrest as the Chk1/Cdc25C pathway can arrest the cell in G2 right after DNA damage. However, p53 and p21 expression is important for a more sustained G2 arrest by inhibiting the Thr161 phosphorylation by CAK. By eliminating the phosphorylation effect of Chk1 on p53, two completely independent pathways are obtained and it is shown that it does not affect the G2 arrest much. So the p53/p21 pathway makes an important, independent contribution to G2 arrest in response to oxidative stress, and any defect in this pathway may lead to genomic instability and predisposition to cancer. Such strict control mechanisms probably provide protection for survival in the face of various environmental changes. The controversial issue related to the mechanism of inactivation of Cdc2 by p21 is addressed and simulation predictions indicate that G2 arrest would not be affected much by considering the direct binding of p21 to Cdc2/Cyclin B given that the inhibition of CAK by p21 is already present if the binding efficiency is within a certain range. Lastly, we show that the G2 arrest time in response to oxidative stress is sensitive to the p53 synthesis rate.
Assessment of Efficiency for a Hybrid Explicit/Implicit Code Simulation of a Multiple Impact Crash Scenario
Authors: Lo Chi , Hinnerichs Terry , Hales Jason
Published: April 2008

Sandia National Laboratories has developed a new explicit nonlinear transient dynamic finite element code called Presto and an associated implicit code called Adagio. This paper describes a process used to assess the ability and efficiency for sharing the computational workload of a multiple impact crash simulation between the explicit (Presto) and the implicit (Adagio) codes to minimize computation time. A numeric example of this hybrid simulation process is given that applies to a dynamic beam impact scenario. Results from simulations using each code will be compared with the hybrid simulation and discussed.
Correlation of Test and FEA Studies on Effect of Bend Radius and Thickness on Ratcheting in Pipe Bends Subjected to Internal Pressure and In-Plane Bending Moment
Authors: Shanmuga Sundaran K. , Thanigaiyarasu G.
Published: April 2008

The paper deals with the results from the analytical study on ratcheting in pipe bends. There has been no well-defined material model and analysis procedure to predict this phenomenon accurately. A recent development in parameter selection of Chaboche’s Kinematic hardening model has resulted in close predictions in ratcheting analysis [15]. A problem has been selected from existing experimental results [16, 17] published in literature, and an analysis incorporating these parameters has been carried out and presented. The amount of stresses induced and strain accumulated in pipe bends with long and short radius and subjected to internal pressure and in-plane bending moment is studied. The results and their inferences are included. The analysis was carried out on 2-inch NPS SS304 pipe bends with different bend radius and two thickness (Schedule 40 and Schedule 80) using ABAQUS, non-linear FEA software to predict the strain accumulation and their influences on ratcheting failure is presented.
Providing Rapid Feedback to Students to Improve Student Learning and Engagement
Authors: Kadlowec Jennifer , Chen John C. , Whittinghill Dexter C.
Published: April 2008

In this project our goal is to improve student learning in engineering mechanics courses. The aim to improve learning was accomplished by providing rapid feedback to students of their understanding of key concepts and skills being taught. The feedback system acts as a catalyst to encourage students, working in pairs, to assist each other in correcting misconceptions or deepening each other’s understanding of the concept or skill at hand. Furthermore, the system allows the professor to assess the students’ level of comprehension or misconception in a just-in-time fashion, and thus guide the pace of covering the material. The feedback is enabled through wireless-networked handheld computers or color-coded flashcards. In the first two years of the study, the feedback system was implemented in two sections of a lower-level, core-engineering course, Statics, as well as in follow-on courses of Dynamics and Solid Mechanics.
The Evolution Required in Standard Cars for the Use of New EGR-VGT Control Strategies
Authors: Arnold J. F. , Langlois N. , Chafouk H.
Published: April 2008

This paper is a study into the possibility of using new control strategies in a standard car. The air system of a diesel engine equipped with a variable geometry turbine and an EGR system (EGR valve and throttle) is considered. New strategies, like GPC or H∞ permit an improvement of the control of both the fresh air flow and the intake manifold pressure. These strategies are not used today in standard car due to the mismatch of both the instrumentation of the ECU’s calculation power. The cost of proposed technology to meet the next emission norm are presented. Some low cost solutions are presented to permit an improvement of the engine control.
Origami Fabrication of SU-8 Supercapacitors
Authors: In Hyun Jin , Kumar Sundeep , Yang Shao-Horn , Barbastathis George
Published: April 2008

The Nanostructured Origami™ 3D Fabrication and Assembly Process was developed as a novel method of creating three-dimensional (3D) nanostructured devices using two-dimensional micro- and nanopatterning tools and techniques. The origami method of fabrication is a two-part process in which two-dimensional (2D) membranes are first patterned and then folded into the desired 3D configuration. This paper reports on the use of the Nanostructured Origami™ process to create a functional electrochemical energy storage device. An electrochemical capacitor, or a supercapacitor, is selected because its performance can be readily improved by the addition of 3D geometry and nanoarchitecture. In addition to improved performance, the origami fabrication method allows such devices to be integrated into preexisting MEMS and IC processes, thus enabling the fabrication of complete micro- and nanosystems with an integrated power supply. The supercapacitors were created by selectively depositing carbon-based electrode materials on the SU-8 membrane and then folding the structure so that oppositely-charged electrode regions face each other in a 3D arrangement. The fabrication process, electrochemical testing procedure, and analysis of the results are presented.
Visualization and Predictive Modeling of Two-Phase Flow Regime Transition With Application Towards Water Management in the Gas-Flow Channels of PEM Fuel Cells
Authors: Son Sang Young , Allen Jeffrey S.
Published: April 2008

Understanding the behavior of gas and water vapor flow through the microchannel gas flow passages of a proton-exchange membrane (PEM) fuel cells is critical to reliable fuel cell operation. Recent research efforts have illustrated the importance of capillarity on the behavior of two-phase flow (gas-liquid) in low Bond number systems; that is, systems where capillary forces are important relative to gravitational forces. Such systems include capillary tubes and microchannels as well as the gas flow channels of a PEM fuel cell. The key characteristic scaling factors for two-phase flow in capillaries have been determined. The choice of length scales and velocity scales in dimensionless groups used to characterize two-phase flow is critical to correctly delineating phase distribution. Traditional scaling for these types of flows have considered the interaction between gas and liquid phases to be primarily inertial in nature. The role of liquid film stability where the phase interaction is a combination of viscous and capillary effects is shown to be a more appropriate scaling for low-Bond number, low-Suratman number two-phase flows. Microscopic visualization at high frame rates has been used to identify the flow regime under various gas-liquid mass ratios, channel geometries and surface energies. The observations collected via high speed microscopy and corresponding pressure measurements are reported for square and circular cross-sectional microchannels with contact angles of 20 degrees (hydrophilic) and 70 degrees (hydrophobic). The effect of geometry and contact angle on the phase distribution and the pressure drop are dramatic.
Adaptive Mesh Generation for Finite Element Analysis of Functionally Graded Materials
Authors: Shin Ki-Hoon
Published: April 2008

Finite Element Analysis (FEA) is an important step for the design of structures or components formed by heterogeneous objects such as multi-material objects, Functionally Graded Materials (FGMs), etc. The main objective of the FEA-based design of heterogeneous objects is to simultaneously optimize both geometric shapes and material distributions over the design domain (e.g., Homogenization Design Method). However, the accuracy of the FEA-based design wholly depends on the quality of the finite element models generated. Therefore, there exists an increasing need for developing a new mesh generation algorithm adaptive to both geometric complexity and material distributions. In this paper, a two-dimensional adaptive mesh generation algorithm is proposed based on the discretization by which continuous material variation inside an object is converted into step-wise variation. The proposed algorithm first creates nodes on the iso-material contours of the discretized solid models. Triangular meshes are then generated inside each iso-material region formed by iso-material contours. Current implementation considers two-dimensional problems and thus needs to be extended to include three-dimensional problems in the near future.
Computer Aided Design of Belt Conveyors for the Process and Manufacturing Industries
Authors: Khalil Shahid , Masood Tariq , Janjua Ajaz Bashir
Published: April 2008

Designing and manufacturing work on Material Handling Equipments specially material conveying system is being carried out in many heavy engineering companies. To overcome the time delay, in conventional design approach, for the design of belt conveyors by utilizing the CAD facilities is not only the need of time but is also necessary for the market competition in this area. This paper explains the methodology of converting the conventional design process of belt conveyors to Computer Aided Design (CAD). This includes software engineering approach and the usage of different tools in order to get a computer based solution for the design of belt conveyors. Application of parametric design and design for manufacturing concepts could also be followed. The main idea is to automate the drafting process and the lengthy calculations involved in the design phase. General arrangement or assembly of a belt conveyor is shown in Fig. 1.
Experiment and Simulation of PET Stretch Blow Molding Process
Authors: Liu Ji-hu , Huang Han-Xiong , Yin Zhan-Song
Published: April 2008

This paper deals with various cases for PET (polyethylene terephthalate) in two-stage stretch blow molding process with a transparent mold and a digital camcorder. The simulations were carried out by POLYFLOW software with K-BKZ viscoelastic model. The predicted wall thickness distributions of the formed bottle were found to be in good agreement with those of experimental measurements. Under same reheating treatment, the two factors, both of the stretch rate and the time sequence of the rod movement and the gas blow, show more great influence on the thickness distributions of final bottle than blow pressure. Besides the three cases of the preform free blow, and the air pressure applied after/before the stretching rod touched the bottom of the mold cavity, the interaction of the two factors may cause another phenomenon, which is the stretching rod touches off the preform bottom after the rod pulls it for a moment. The phenomenon easily makes for an eccentricity of the bottle bottom.
Numerical Modeling of the Coupled Convective Heat Transfer in the Cylinder Block and the Water Jacket of Engine
Authors: Li Longjian , Cui Wenzhi , Jen Tien-Chien , Chen Qinghua
Published: April 2008

In this paper the physical and corresponding mathematical models of the 3D coupled heat conduction-convective heat transfer in a cylinder and its water jacket of the automobile engine were proposed. The standard k-ε turbulence model was employed to simulate the turbulent flow in the water jacket. The empirical correlations on the in-cylinder heat transfer in conjunction with the tested combustion data were used to calculate the thermal boundary conditions of the inner wall of the cylinder. The control-volume based finite element method was used to solve the 3D coupled heat conduction-convective heat transfer problem mentioned above. The computations were carried out under different engine speed from 1500rpm to 6000rpm, and the temperature distributions in the cylinder and its water jacket were revealed in detail. The relative errors between the tested temperatures at the fixed points and the corresponding ones were within the range form −12% to 4%.
Predictions of Flow Boiling in Fractal-Like Branching Microchannels
Authors: Daniels Brian J. , Pence Deborah V. , Liburdy James A.
Published: April 2008

Single-phase and two-phase flows in microscale fractal-like branching flow networks are studied using a one-dimensional model that includes variable property and developing flow effects. Pressure drop, pumping power, changes in the bulk fluid temperature and a performance parameter are reported for mass flow rates ranging from 25 to 500 g/min and wall heat fluxes from 5 to 40 W/cm2. Two-phase flow through fractal-like flow networks is also compared to flow through a series of parallel channels for identical wall heat fluxes and for flow rates between 25 and 100 g/min. Channel length, height, convective surface area, heat flux and flow rate were the same between the fractal-like and parallel channel array. It was found that single-phase flows through fractal-like flow networks exhibit lower pressure drop and pumping power than do two-phase flows at the same wall heat flux and mass flow rate. The inlet temperature for the single-phase cases is 20°C, whereas the two-phase flow enters as a saturated liquid. The pressure drop and pumping power were always lowest for the fractal-like flow networks compared with the parallel channel arrays for identical heat transfer and flow rates.
Triological Performance of Tumbled MOS2 on Biomimetic cBN-TiN Coating
Authors: Wu J.-H. , Jiang Wenping , Phillips B. S. , Sanders J. H. , Zabinski J. S. , Malshe A. P.
Published: April 2008

cBN-TiN hard composite coatings were prepared by a hybrid deposition technique, i.e., electrostatic spray coating (ESC) followed by chemical vapor infiltration (CVI). The coating surfaces have a biomimetic surface texture of lotus leaf. These surface structures can serve as the reservoirs of solid lubricant particles of MoS2, which have nano and submicron size scales in diameter. The tumbled MoS2 covered the whole cBN-TiN coating surface, leading to a smoother surface (or reduced average surface roughness Ra). Vacuum tribological tests were carried out for both the coatings before and after tumbling. Sliding results suggest that the burnished cBN-TiN coating has a significantly lower coefficient of friction. High temperature sliding tests showed that the effectiveness of the tumbled lubricant layer decreased with increasing testing temperature. Worn coating surfaces and pin scars were characterized by using optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Characterization results show that the tumbled MoS2 layer is responsible for friction reduction during room temperature sliding. This also implies that the biomimetic surface structure is effective for holding the MoS2 solid lubricant particles.
Development of Metallic Materials Using Hybrid Microwave Assisted Rapid Sintering
Authors: Wong W. L. E. , Gupta M.
Published: April 2008

Powder metallurgy is a highly established method for fabricating metals and metal matrix composites. An innovative hybrid sintering technique involving the use of microwaves and radiant heating is currently proposed. The use of microwaves to heat metallic materials is not common because it is a well known fact that bulk metals reflect microwaves and causes arching when placed inside a microwave oven. Microwave heating of materials is fundamentally different from conventional resistance heating and offer many benefits over conventional heating. In this study, aluminum, magnesium and a lead-free solder were selected as candidate materials and sintered using conventional sintering as well as a novel hybrid microwave assisted sintering. The sintered materials were hot extruded and characterized primarily in terms of physical and mechanical properties. An overall superior combination of hardness and tensile properties were realized in the case of microwave sintered samples when compared to the conventionally sintered samples.
Fatigue Performance of AAR Class A Railroad Wheel Steel at Ambient and Elevated Temperatures
Authors: McMaster Fraser J. , Robledo Guadalupe B. , Gordon Jeffrey E.
Published: April 2008

Classical stress-life (S-N) curves were developed for Association of American Railroads (AAR) Class A wheel steel with specimens removed from the rim area of an as-forged railcar wheel. The specimen geometry was a standard hourglass fatigue test specimen with a low stress concentration (Kt) of 1.05. Fatigue testing was performed at stress ratios of −1.0, 0.05, 0.5 and 0.7. Testing was performed at ambient, 500° F and 1000° F using high current resistance or convection methods. Endurance limit data was obtained for all R-ratios, although for the 1000° F condition there did not appear to be a clear endurance limit transition. These endurance limit data were used to estimate the Sines parameters, A and α.
Mass Transfer in Functionally Graded Solid Oxide Fuel Cell Electrodes
Authors: Greene Eric S. , Chiu Wilson K. S.
Published: April 2008

A 1-D computational model is presented in which performance of a solid oxide fuel cell with functionally graded electrodes can be predicted. The model calculates operational cell voltages with varying geometric and operational parameters. The model accounts for losses from mass transport through the porous electrodes, ohmic losses from current flow through the electrodes and electrolyte, and activation polarization. It also includes a model for the full or partial internal reforming of methane. The model was applied to investigate the effect of electrode porosity distribution on performance. Specifically the physical phenomena that occur when the electrode is designed with a change in microstructure along its thickness is studied. The general trends that occur are investigated to find the arrangement for which the minimal polarization occurs. Both diluted hydrogen fuel and partially reformed methane streams are investigated. It is concluded that performance benefits are seen when the electrodes are given an increase in porosity near the electrolyte interface.
ESC Effectiveness During Property Variations on Scaled Vehicles
Authors: Whitehead Randy , Clark Ben , Bevly David M.
Published: April 2008

Scaled passenger vehicles in conjunction with computer simulation have proven to be a valuable tool in determining rollover propensity. In this study, vehicle properties are varied to see their impact on roll stability and a stability threshold is derived empirically using simulation. The stability threshold is validated by scaled vehicle experiments. This is made possible with the lower cost and increased safety of using a scaled vehicle versus full size passenger vehicles. A simple electronic stability control (ESC) is then developed to keep the scaled vehicle within the stability threshold. The ESC is tested using varying vehicle properties with a constant vehicle model to see how these property changes affect the ESC’s effectiveness to prevent rollover. The ESC is then implemented with an Intelligent Vehicle Model (IVM) which updates the controller’s vehicle model as vehicle properties such as loading conditions change. This study shows that an IVM greatly increases the success of ESC in keeping the vehicle in the stability region.
Neural-Network Based On-Line Adaptation of Model Predictive Controller for Dynamic Systems With Uncertain Behavior
Authors: Sanjuan Marco E.
Published: April 2008

Model-based controllers have positioned themselves in industrial applications, working mainly on top of a layer of PID controllers. Their implementation takes an important amount of time because of the required PID tuning and the model characterization/identification. This paper presents a strategy to perform on-line adaptation for the dynamic matrix coefficients in a DMC controller. Based on the observed PH (Prediction Horizon) elements of the response and controller signal vectors, and based on a non-residing control horizon controller design, the direct control problem is reformulated using the full-effect dynamic matrix (PHxPH) as an unknown. Data is collected and used in two directions: training a RAWN Network (Random Allocation Weight Neural Network), to describe recently observed process behavior, and to solve a least-squares problem for a set of linear equations where the unknowns are the characteristic response coefficients. The paper presents the effect of both approaches, illustrating the adaptation algorithms operation in a highly nonlinear process where the controller is designed in a low-gain region. Then the process operating condition is shifted so that it moves to a high-gain region to observe controller response.
New Expressions for Fillet Weld Torsion Shear Stresses Calculation
Authors: Goytisolo Rafael , Hernandez Hernan , Moya Jorge , Jackson Inga M.
Published: April 2008

The fillet welds are conventionally calculated to shear stress in the weakest section: the throat area of the weld. This consideration is a simplification for any fillet weld. Nevertheless, this procedure is internationally accepted as a justified procedure, mainly, for the simplification that makes the calculation of the welded joints of an engineering construction an easy procedure. This premise has motivated that different authors try to obtain calculation expressions for different cases that are presented in the practice, looking to facilitate the work of the industry technicians and engineers in charge of carrying out the calculation of these unions, however, in this pawn they don’t always use the most appropriate methods settled down by the Mechanics of the Materials introducing inaccuracies in these expressions. The Fracture Mechanics has outlined a new necessity: the development of methods of predicting defects that could exist in the welding cords. In order to do that, it is required to determine the stresses that arise in the welding with a superior accuracy. In this paper, the Theory of the Torsion of Thin Walls Profiles is applied to the calculation of the torsion shear stresses of the fillet weld joints. New calculation expressions are obtained that belong together better than the classic expressions with relationship to the values obtained by the Finite Elements Method.
Development of a Scanning Hot Probe Technique for Thin-Film Thermoelectric Properties Characterization
Authors: Hapenciuc Claudiu L. , Borca-Tasciuc Theodorian
Published: April 2008

This work reports on the development of a scanning hot probe technique for the measurement of thermoelectric properties of thin-films. In this method a resistively heated thermal probe of an Atomic Force Microscope (AFM) is brought in contact with the sample surface giving rise to a temperature gradient and a Seebeck voltage in the specimen. The average temperature rise of the probe is determined from the change in its electrical resistance. The heat transfer rate between the probe and the sample is estimated using a heat transfer model that takes into account the major heat transfer mechanisms in the system. The thermal conductivity is determined from the measured thermal resistance of the film. The Seebeck coefficient value is calculated using the measured temperature drop and the Seebeck voltage in the plane of the sample. The method is calibrated on glass and silicon substrates. Preliminary experimental results are presented for a thermoelectric film composed of randomly aligned Bi2Te3 nanowires deposited on a glass substrate.
A Novel Concept to Improve the Performance of LED Panel Using Drilled Holes
Authors: Chiang S. B. , Wang C. C.
Published: April 2008

In this study, the concept of the thermal module of LEDs cooling by use of drilled hole to entrain air flow was examined. It is found that the drilled hole does not necessarily improve the overall performance. It depends on the size of the drilled hole, the number of drilled holes, and the locations. The heat transfer coefficients are generally increased with the number of drilled holes and the diameter of the drilled hole. In this paper, the plate fin heat sink has a higher heat transfer coefficients than pin fins, but the overall performance of the LED panel having pin fin outperforms that of plate fin. This is because the pin fin provides much larger surface area. For decrease the maximum temperature of the LED panel, placement of the drilled holes along the hot region will be more effective.