bluuebunny/crossref_metadata_2025 huggingface dataset:
A Large-Deformation Theory for Thermally-Actuated Shape-Memory Polymers and its Application
Authors: Chester Shawn A. , Srivastava Vikas , Di Leo Claudio V. , Anand Lallit
Published: May 2012

The most common shape-memory polymers are those in which the shape-recovery is thermally-induced. A body made from such a material may be subjected to large deformations at an elevated temperature above its glass transition temperature &Vthgr;g. Cooling the deformed body to a temperature below &Vthgr;g under active kinematical constraints fixes the deformed shape of the body. The original shape of the body may be recovered if the material is heated back to a temperature above &Vthgr;g without the kinematical constraints. This phenomenon is known as the shape-memory effect. If the shape recovery is partially constrained, the material exerts a recovery force and the phenomenon is known as constrained-recovery.
Neural Network Control of a Flexible Link Manipulator in Contact With a Compliant Environment
Authors: Sabzehgar Reza , Moallem Mehrdad
Published: May 2012

A neural network controller for regulating the contact force of a flexible link manipulator in contact with a compliant environment is proposed in this paper. The dynamic model of a single-link flexible (SLF) manipulator is obtained using three rigid sub-links connected by two virtual springs. It is assumed that the length of each link is short enough to be considered as a rigid link. A neural network-based control strategy is then proposed to relax the a-priori knowledge of the model parameters of the flexible link manipulator. The weights of the neural network controller are adjusted to minimize the error between the actual contact force and desired force. To overcome the non-minimum phase characteristic of the system, a weighted term of input signal is added to controller’s cost function. Simulation results are presented to evaluate performance of the proposed controller.
Numerical Simulation of a Microchannel Heat Exchanger Using Steady-State and Time-Dependent Solvers
Authors: Dang Thanhtrung , Teng Jyh-tong
Published: May 2012

Microchannel heat exchangers are employed for thermal management of electronic devices, IC circuits, etc. Simulation of microchannel heat exchangers using solver with the capability of dealing with steady-state and time-dependent conditions is carried out. The solver — COMSOL — was developed by COMSOL Multiphysics, Inc. using the finite element method. The pressure drop and heat transfer are two of the most important parameters in these devices. In this study, the results obtained from the numerical analyses were in good agreement with those obtained from the papers. In addition, using the same heat exchanger configuration, results obtained from numerical simulations of pressure drop and overall thermal resistance using the COMSOL indicated that those parameters are lower for the cases with parallel-flow than those with the counter-flow.
Temperature Effect on Drop-Weight Impact of Hybrid Woven Composites
Authors: Budhoo Yougashwar , Liaw Benjamin , Delale Feridun , Iyer Ramki
Published: May 2012

This paper investigates the effect of temperature on hybrid and non-hybrid woven composite panels (100mm×100mm×6.35mm) drop-weight impacted at five different temperatures:−60°C,−20°C, room temperature (R.T), 75°C and 125°C. The studies were conducted by combining experimental and 3-D dynamic finite element (FE) approaches. The specimens tested were made of plain-weave hybrid S2 glass-IM7graphite fibers/toughened epoxy. The composite panels were damaged using an instrumented drop-weight impact tester equipped with an environmental chamber for temperature control. The time-histories of impact-induced dynamic strains and impact forces were recorded. The damaged specimens were inspected visually and using the ultrasonic C-scan method. A 3-D dynamic finite element software package, with Chang-Chang composite damage model, was then used to simulate the experimental results of the drop-weight tests. Good agreement between experimental and FE results has been achieved. It is observed that the variation of results obtained from our experiments for the hybrid composites was very small (about 8%) when compared to those of non-hybrid composites. Also, when looking at the hybrid or non-hybrid composite, the effect of temperature at −60°C, −20°C was not significant whereas at 75°C and 125°C the results were more distinct.
Combustion of Boron Nano-Particles in Ethanol Spray Flame
Authors: Karmakar Srinibas , Acharya Sumanta , Dooley Kerry M.
Published: May 2012

Biofuels such as ethanol have lower energy density than conventional petroleum-based fuels, and therefore enhancing its energy density via addition of high-energy density components is an attractive option. Boron is an attractive fuel additive because it has among the highest volumetric heating value among potentially suitable additives. The present study deals with an experimental investigation of boron combustion in an ethanol spray flame. A constant low particle loading density of boron nanoparticles (60nm SMD), around 1% (by weight) of the liquid fuel flow rate, has been used. Though it has high energetic potential, the combustion process of boron is retarded by the initial presence of the oxide coating the particle surface. In the present study, measurements have been made of the emission of intermediate sub-oxide like BO2 using spectroscopy and imaging with interference filters. The effect of boron on the hydrocarbon combustion has also been studied by examining the heat release and product mole fractions. In addition, particle characterization has been carried out to know the size, surface structure/composition of the injected boron nano powders using XRD, XPS and TEM. A preliminary investigation has also been performed on the burnt particle collected from the exhaust structure using XRD. The chemiluminescence and spectroscopic signatures indicate that boron combustion is facilitated and that hydrocarbon combustion is enhanced. The particle analysis shows differences in the imaged and spectroscopic characteristics of the unburnt and burnt nano-particles reflecting the particle-combustion processes.
Comparative Performance of Cylindrical Solar Water Heating System With and Without a Reflective Surface
Authors: Ogueke N. V. , Anyanwu E. E.
Published: May 2012

The comparative performance of a cylindrical solar water heating system with and without reflective surface is presented. The major components of the water heater are a transparent cylindrical PVC material acting as the glazing and a copper tube painted black for improved solar energy absorption. One of the systems has it’s under segment, about 45°, lined with an aluminium foil to act as a reflective surface. The two systems were tested under the meteorological condition of the Federal University of Technology, Owerri, Nigeria. Results obtained reveal a maximum exit water temperature from the solar water heater of 68 and 50°C for the reflective and non reflective surface conditions, respectively. The maximum efficiencies were determined as 70% and 40%, respectively for the reflective and non reflective surface conditions while the Hottel-Whillier-Bliss characterization showed that addition of the reflective surface improved the solar water heater’s ability to absorb energy by about 100% and reduced the rate at which it loses by up to 25%. Thus the system with a reflective surface has better capability of converting solar energy to heat for hot water generation.
Finite Element Analysis of Composite Piezoelectric Actuators Incorporating Nonlinear Material Behavior
Authors: Qidwai M. A. Siddiq , DeGiorgi Virginia G.
Published: May 2012

There is always the question of choosing the appropriate constitutive model when simulating and analyzing piezoelectric material performance. Linear material modeling typically requires less computational resources; however this approach may not accurately capture the performance. In this paper, the scope of linear predictive modeling was analyzed by comparison with nonlinear modeling. Monomorph and bimorph actuators were modeled with each approach, and their respective performances were compared. It was found that even under small magnitudes of electric field, differences arise between the two approaches. The magnitude of the deviations depended upon actuator composition, applied electric field and boundary conditions. The impact of these differences can be considerable, such as for precision-based applications and cyclic applications where initial design errors could compound.
Delay in Flow Separation for Circulation Controlled Cylinders
Authors: Patterson Byron W. , Angle Gerald M. , Pertl Emily D. , Smith James E.
Published: May 2012

Recent circulation control testing at West Virginia University, in a closed loop wind tunnel, has been conducted on models where the trailing edge radius was selected to be smaller than that used in literature, such as Loth and Boasson [1], 1.5 inches and Englar [2], 0.4375 inches. The reduced size was chosen in an attempt to minimize the drag experienced during periods of non-activation of the circulation control, and the smaller size was more compatible to the wind tunnel test section size. However, while the drag is lessened by a smaller trailing edge, the performance of circulation control also appears to be dependent upon a multitude of variables including, but not limited to, the trailing edge radius and jet velocity. Through a modeled experiment, the two attributes that influence the circulation control performance were concurrently manipulated by varying the radius of curvature and the velocity of the blown jet. The combination of these characteristics were experimentally explored to determine the location where the jet leaves the surface of the cylinder, also known as the separation point. The optimum separation point is defined as the farthest angular displacement from the plane of the blown jet exit slot, which corresponds to the greatest increase in the circulation around the cylinder, representing the trailing edge of a circulation control airfoil. From the known radius and jet velocity, an expression that relates the separation point and the mass flow rate velocity quantity are compared. Understanding the blowing coefficient and its impact on the separation point, results in a predictive relationship between these two attributes of circulation control. The results of this two-dimensional cylinder study found that an increase in trailing edge radius decreased the location of the separation point. In addition, an increase in the jet velocity resulted in an increase in the separation point location. The combination of these two quantities produced a relationship similar to each individually, illustrated by the mass flow rate velocity value, which is the blowing coefficient excluding free stream conditions, versus the angle of separation. Data is therein compared to the theory by Newman [3], which predicts a maximum separation point location at 245 degrees beyond the jet exit plane and an increase in the separation point as the radius of curvature increases. The results of this study found a separation point maximized at 231 degrees, and, contrary to Newman [3], a decrease in the separation point was found as the radius of the cylinders increased.
Unified Methodologies, Formats and Outlines in Online Engineering Education
Authors: Salemi Amir , Jazar Reza N.
Published: May 2012

Online education in engineering is developing as the communication technology advances. Although many online courses are being presented worldwide they have not been broadly accepted. For the online engineering education to be well successful and outperform traditional on-campus education, much has been done since ten years ago. To satisfy the five pillars in online education introduced by Sloan Consortium, there are still rooms for improvement[1]. Access, Learning effectiveness, student satisfaction, faculty satisfaction and cost effectiveness are the five metrics that drive investigations into online education. Problems related to “access” have been largely solved since the beginning of online technology era. Still, many substantive issues remain in gaining attention share and providing optimum modalities to specific classes of learners. Significant progress has also been made in “learning effectiveness”, however not much methodologies and guidelines have been developed to define outlines for transferring engineering text book into interactive/multimedia format featuring non-solitary, instructor-led activities with high communication attributes. Costs for creating and running online courses have plummeted over the decade and the average expense of online courses has decreased in recent years specially due to reducing the call on classroom space. This is a positive indication that online engineering education could potentially cost less than traditional on-campus education down the track. This research will shed light on online engineering education and will develop methodologies, formats and outlines with the aim of creating interactive online engineering courses. The methodologies and guidelines will be ideally covering all courses with general applicability and could be used as reference for all educational institutes that are keen to provide and develop online engineering education. This research will also define teaching methodologies in online engineering education that fit each course with less instructors’ influence and with consideration of specific classes of learners. The extent of instructors’ influence in online engineering education for each course will also be defined as part of this research. The outcome of this research will be used by engineering disciplines for implementation of online engineering education and to improve the efficiency of education.
Numerical Results of Non-Newtonian Displacement in Non-Rectilinear Oil Wells
Authors: Savino Jaques , Naccache Monica , de Souza Mendes Paulo
Published: May 2012

An important problem that occurs during drilling, completion and gravel packing operations is the contamination among fluids. The drilling fluids and cement pastes present a non Newtonian (viscoplastic) behavior, while the spacer fluids, used as an attempt to avoid contamination, are Newtonian. The analysis of the flow displacement and of the interface configuration between these fluids helps to determine contamination and the displacement efficiency, and is an important tool for the process optimization. In this work we performed a numerical study to analyze the displacement of one fluid by another through a non-rectilinear, horizontal annular channel, using Fluent Software (Ansys Inc.). The solution of the conservation equations of mass and momentum is obtained via the finite volume technique, and using the volume of fluid method to handle the multi-fluid situation. The effects of rheological parameters on the interface shape and displacement efficiency are investigated. When the viscoplastic liquid pushes the Newtonian one, the displacement efficiency decreases as we increase the velocity and the viscosity of the displaced fluid. Moreover, the fingering undesired phenomenon is observed for higher velocities. On the opposite situation, when the Newtonian fluid pushes the viscoplastic one, the displacement efficiency increases with the velocity and viscosity of the displacer fluid, and the fingering is observed at lower flow rates. The effect of viscosity ratio was also investigated, but it is shown that it does not affect the displacement efficiency.
Using LEGOs to Teach Product Design and Team-Based CAD Modeling
Authors: Yip-Hoi Derek , Newcomer Jeff
Published: May 2012

Team-based CAD modeling projects offer an opportunity for students to experience the challenge of building a model using inputs from several designers. Such projects are however difficult to formulate in a manner that requires each team member to make an equitable contribution and for the level of complexity across different teams to be similar. Often, realism and the opportunity to use the more advanced modeling features are sacrificed for the sake of expediency. In the Engineering Design Graphics II (EDG II) course at Western Washington University (WWU) a LEGO® based CAD modeling project has been introduced that is designed to encourage students to use more advanced techniques, such as sweep and loft, while at the same time providing a means to achieve realism and better consistency in effort across teams. This paper summarizes the experience of running this type of project. Results show that while some variability exists on how the approach promotes increased usage of advanced part modeling techniques and improved consistency in project complexity across teams, the potential to manage these is greatly enhanced. Further, as the examples show, the approach is rich enough to motivate innovative concept development. Students are able to fully exercise the design process leading to a functioning, physical prototype that closely matches their CAD work.
Numerical and Experimental Analysis of Convection Transfer During Melting by a Mono-Pulsed Laser
Authors: Laazizi Abdellah , Courant Bruno , Jacquemin Fre´de´ric , Andrzejewski Henri , Mattei Simone
Published: May 2012

This paper presents a comparison between simulation and experimental results of the melting process of metallic material by a pulsed laser source Nd-YAG. Variations of the thermophysical properties were considered. Furthermore, the model included the effects of the surface-tension gradient on the fluid surface and the buoyancy force. The keyhole effect induced strong surface deformations and often formed cavities, which arre undesirable in the surface treatment process. An experimental study of the surface profile of the melted zones was also conducted to seek a relationship between the so-called keyhole effect and the laser triangulation measurements. The predicted Laser Melted Zone (LMZ) morphology was in good agreement with the corresponding experimental measurements for various irradiation conditions, as long as the keyhole effect did not occur.
Hot Spot Mitigating With Oblique Finned Microchannel Heat Sink
Authors: Lee Yong-Jiun , Lee Poh-Seng , Chou Siaw-Kiang
Published: May 2012

Sectional oblique fins are employed in contrast to continuous fins in order to modulate the flow in microchannel heat sink. The breakage of continuous fin into oblique sections leads to re-initialization of boundary layers and generation of secondary flows which significantly enhance the cooling performance of the heat sink. In addition, oblique finned microchannel heat sink has the flexibility to tailor local heat transfer performance by varying its oblique fin pitch. Clusters of oblique fins at higher density can be created in order to promote greater degree of boundary layers redevelopment and secondary flows generation to provide more effective cooling at the high heat flux region. Thus the varying of oblique fin pitch can be exploited for hot spots mitigation. Simulation studies of silicon chip with hot spot shows more than 100% increment in local heat transfer coefficient at the high heat flux region for the variable pitch oblique finned microchannel compared with the conventional microchannel heat sink. Both the maximum temperature and its temperature gradient are reduced by 12.4°C as a result. Interestingly, there is only little or negligible pressure drop penalty associated with this novel heat transfer enhancement scheme in contrast to conventional enhancement techniques.
Effect of High Density Electric Current Field on Fatigue Cracks in Stainless Steel
Authors: Hosoi A. , Nagahama T. , Ju Y.
Published: May 2012

A technique was developed to heal a fatigue crack by controlling a high density electric current field. The high-density electric current field was applied at the tip of the crack by using closely spaced electrodes. It was found that the electric stimulation influences the states and propagation behavior of a fatigue crack in the stainless steel. When the electric current was applied to a specimen having a pre-crack with a large opening displacement, a closure effect at the crack tip was shown and the bridges between the crack surfaces were observed. On the other hand, when the electric current was applied to a specimen having a pre-crack with a small opening displacement, an opening effect was shown. These effects were also evaluated quantitatively by the Paris law.
Evaluation of Wellness by Detrended Fluctuation Analysis of Heartbeats
Authors: Yazawa Toru , Shimoda Yukio , Katsuyama Tomoo
Published: May 2012

We used detrended fluctuation analysis (DFA), which was originally developed by Peng et al. (1995) to check power-law characteristics, to study the heartbeats of various subjects. Our purpose was to determine whether DFA is a useful method for the evaluation of a subject’s quality of recovery from cardiovascular-related illness and transition to a normal healthy state. Here, we report on subjects who underwent rehabilitation thermal therapy, subjects who developed premature ventricular contractions, and other subjects, including healthy subjects. The perceived level of wellness varies among subjects because the physiology of no 2 individuals is identical. However, several case studies have shown how wellness of subjects can be evaluated using heartbeat recordings. We conclude that DFA is a new, useful numerical method for quantifying the degree of wellness and the transition from sickness to wellness.
A Demand Based Optimum Solar Panel Orientation
Authors: Naraghi Mohammad H.
Published: May 2012

The clear sky and monthly clearness index models are used to evaluate the hourly and monthly insolation on unit area of a tilted surface for the entire year. The hourly power consumption of a typical municipality (for this case New York City) for typical summer and winter days are used to determine the tilt and azimuth angles of a solar panel such that the solar energy reached the panel best match the energy consumption pattern. For the example case considered, in this work New York City, the electric power consumption peaks during summers at afternoon hours, due to increase in building cooling loads. It is found that orienting the solar panel at a westward azimuth angle with a tilt angle that results in maximum annual insolation is the best orientation of the solar panel for responding to both the peak energy demand and having reasonably high overall annual power generation. Although the model is used to optimize the solar panel orientation for New York City, it can however, be used for any building at any location as long as the needed solar data and power consumption pattern are known.
Direct-Deposition and Multiple Materials Integration of Tissue Engineering Scaffolds
Authors: Wei Chuang , Sonawane Bhushan , Cai Lei , Wang Shanfeng , Dong Jingyan
Published: May 2012

High-aspect-ratio three-dimensional structures using biocompatible materials are critical for tissue engineering applications. This study develops a multi-nozzle direct-write approach to construct tissue engineering scaffolds with complex three-dimensional structures utilizing polymeric materials. This approach provides the capability to fabricate three dimensional scaffolds by depositing biocompatible UV-curable polymeric material and thermoplastic material (paraffin wax) layer-by-layer, which respectively are used as structural material and supporting material that will be removed later on. The designed structure is built by selectively extruding drops and/or filament through a set of syringes that host different functional materials, following a layer-by-layer sequence. The location of the deposition is precisely controlled by a high precision three-dimensional translational stage. After different structural/functional materials and the supporting material are deposited with predesigned pattern, the supporting material is removed by using appropriate chemical solvent which will not affect physical and chemical properties of the designed structure. The mechanical property of the structure, the equilibrium modulus and dynamic stiffness, can be engineered by designing different pore size for the scaffold. The multi-nozzle based direct writing approach provides a practical solution to build scaffolds for tissue engineering and integrate multiple functional materials together into a single scaffold structure.
On the Thermodynamic Cycle of a MEMS-Based External Combustion Resonant Engine
Authors: Bardaweel H. , Richards R. , Richards C. , Anderson M.
Published: May 2012

In this work we investigate the thermodynamic cycle of a resonant, MEMS-based, micro heat engine. The micro heat engine is made of a cavity encapsulated between two membranes. The cavity is filled with saturated liquid-vapor mixture working fluid. Heat is added/rejected from the engine at a frequency equal to its resonant frequency. Both pressure-volume and temperature-entropy diagrams of the resonant engine are used to investigate the thermodynamic cycle of the resonant micro heat engine. The results show that the thermodynamic cycle of the engine consists of four major processes: heat addition, expansion, heat rejection, and compression. pressure-volume and temperature-entropy diagrams are bounded by two constant temperature processes and two constant volume processes. The temperature-entropy and pressure-volume diagrams show deviations from this ideal description and are rounded due to the presence of irreversible effects. Major sources of irreversibility in the engine are heat transfer over finite temperature differences during heat addition and rejection, heat transfer into and out of engine thermal mass and viscous losses due to liquid working fluid motion. The measured second law efficiency of the micro heat engine is about 16%.
Some Aspects Regarding Treatment and Rehabilitation of Weight Bearing Joints for Patients With Osteoarthritis
Authors: Pop Petru A. , Lazar Liviu , Marcu Florin M.
Published: May 2012

The paper presents some aspects and practical solutions of weight bearing joints treatment for patients with osteoarthritis and following by the rehabilitation process, which has realized at Recovery Clinical Hospital of Felix Spa. A model of human body under applied and conjunction forces explains the damping and shocks into synovial joints from elastic modulus of bone cartilages in contact and variation of dynamic viscosity’s synovial fluid and spine fluid. The conservative treatment of osteoarthritis involves balneal-physical-kinetic therapy or balneal-physical-kinetic recovery treatment, which must be repeated periodical, every six months to get good results. In addition, a vibration treatment of patients with osteoarthritis combines with balneal-conservative treatment is proposed. This vibration treatment system is composed of vibration bed, electrical motor to generate the vibration with direct adjustment of frequency by a digital frequency convertor, and a command panel system of measurement, analysis and interpretation of data from FFT electronic vibration gage. These combination treatments have assured an amelioration of patients with osteoarthritis and improving the bio-lubrication between cartilages of synovial joints, respectively of fluid spine.
Low Cost Particle Swarm Algorithm Using Surrogate Model Based Pre-Evaluation for Inverse Heat Conduction Analysis
Authors: Vakili S. , Gadala M. S.
Published: May 2012

Using internal temperature measurements from inside a solid to determine the initial or boundary conditions or material properties is a common inverse heat conduction problem. These problems are ill-posed in nature and a robust mathematical solution is not available for them. Stochastical search algorithms like Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) have been found to be very effective in dealing with some of the challenges in solving inverse problems, such as time step size limit and sensitivity to the measurement errors. However, these methods normally require large population size and do not use the gradient information and, therefore, their computational costs are generally higher than their gradient based alternatives. This is especially true when using a computationally expensive high-fidelity method like finite element analysis as the direct solver in the core of the inverse algorithm. The inherent inefficiency of this procedure is even more obvious when we notice that an algorithm like PSO is rank-based, i.e. the actual magnitude of cost function is not important, and only their relative ordering is used. In a typical implementation of PSO, most of the objective function evaluations are discarded, unless when it is improving the local memory of the particle. A computationally cheaper substitute for full analysis methods is using metamodels also known as surrogate models. They construct an approximation to the direct problem using a set of available data and the underlying physics of the problem. In this research, an inexact pre-evaluation of the boundary heat flux components using a simplified physics and data fitting is used to find the more promising solutions, and then an accurate but computationally expensive three-dimensional finite element discretization of the heat conduction problem is applied only to these elite members of the population. The result is an inverse heat conduction analysis method that has the stability and effectiveness of PSO, and at the same time has a much lower computational cost. In this research, we use a sequential implementation of PSO in dealing with the transient boundary heat flux, and a future time step regularization method is used to create a more stable algorithm. The focus of the test cases in this research paper will be the inverse heat conduction problem in the controlled cooling of steel strips on a run-out table, but the algorithm is readily applicable to other applications of inverse heat conduction analysis.
Development of Simplified Spot Weld Models: Stiffness Prediction and Computational Performance Evaluation
Authors: Khandoker Noman , Takla Monir , Ting Thomas
Published: May 2012

Simple spot weld connection models are desirable in huge and complicated finite element models of automotive body-in-white structures which generally contains thousands of spot weld joints. Hence, in this paper six different individual spot weld joint finite element models simplified in terms of their geometric and constitutive representations were developed including the one that is currently used in automotive industries. The stiffness characteristics of these developed models were compared with the experimental results obtained following a simple strategy to design the welded joint based on the desired mode of nugget pull out failure. It was found that the current spot weld modeling practice in automotive industry under predict the maximum joint strength nearly by 50% for different loading conditions. The computational costs incurred by the developed models in different loading conditions were also compared. Hence, a suitable model for spot welded joints is established which is very simple to develop but relatively cheap in terms of computational costs.
Effects of Bronchodilators Combined With Oscillations on the Contracted Airway Smooth Muscle
Authors: Mathur M. , Al-Jumaily A. M. , Ijpma G. , Alany R.
Published: May 2012

Current asthma treatments using anti-inflammatory agents and airway smooth muscle (ASM) relaxants are expensive, variable in effectiveness and are associated with several cardiovascular side effects. Previous in vitro experiments conducted on ASM tissues suggest that oscillations applied to contracted muscle result in a reduction in the contractile ability of the tissue. This study focuses on investigating the combined effects of muscle relaxants (bronchodilators) and length oscillations on the dynamics of contracted ASM. Isolated porcine tracheal smooth muscle tissues are contracted using Acetylcholine. Isoproterenol (Iso), a β-agonist, is used as a bronchodilator to relax the contracted ASM. Our results suggest that the combined effect of Iso and breathing oscillations is noted to be greater than the added effects of Iso and breathing alone. It can be proposed that breathing oscillations aid the relaxation of ASM by Isoproterenol.
Enhancement of Oxygen Diffusion in a Gas Diffusion Layer of a Fuel Cell Electrode by Magnetizing Force
Authors: Tasaka Eiji , Asako Yutaka
Published: May 2012

Possibility of enhancement of oxygen diffusion in a gas diffusion layer of a fuel cell electrode is numerically investigated. Since oxygen is paramagnetic gas, it is attracted to a field of high magnetic flux density by the magnetizing force. If there exists gradient of the oxygen concentration and the gradient of magnetic flux density in the gas diffusion layer, air flow occurs in the layer. Numerical computations were conducted for air flow in the gas diffusion layer of the electrode under the magnetic field which is generated by parallel electric currents. Darcy model is used to represent the air flow in the layer and the oxygen concentration was solved. The effects of the permiability of the electrode, intensity of the electric current, the location of the electric wire and the thickness of the electrode on the enhancement of oxygen transfer were investigated. As a result, 5 to 20% of enhancement of oxygen transfer by using magnetizing force was observed.
Developing the Coaxial Dual-Pipe Heat Pipe for Applications of Heat Pipe Cooler
Authors: Chen Chien-Chih , Ting Chen-Ching
Published: May 2012

This article presents significant experimental data about the coaxial dual-pipe heat pipe which is new developed for applications of the heat pipe cooler in our CCT laboratory. It’s well known that heat pipe integrated with cooling plates has changed the heat transfer property of the heat pipe to be similar to copper pipe, where the heat transfer property of the bare heat pipe is discrete and the copper pipe is continuous. The integrated cooling plates cause the original heat transfer property of the heat pipe to be destroyed. For recovery of the original heat transfer property of the heat pipe in a heat pipe cooler, the coaxial dual-pipe heat pipe built a coaxial pipe inside the heat pipe in the thermal insulating section to avoid the heat of vapor being earlier taken away in the thermal insulating section. Experimental study in this work first built a home-made square coaxial dual-pipe heat pipe integrated with outside isothermal cycling cooling water. The home-made square coaxial dual-pipe heat pipe has an observation window and is convenient to observe the change of two-phase flow inside the heat pipe influenced by the outside cooling water. The results show that the new developed dual-pipe heat pipe cooler has kept the original heat transfer property of the bare heat pipe and therefore increases its cooling efficiency clearly.
Risk Analysis of Failure Under Combined Damage Modes of Steam Turbine Components
Authors: Fujiyama K. , Suzuki H. , Tsuboi T.
Published: May 2012

The Risk Based Maintenance (RBM) procedure was applied to steam turbine casing as a typical example of components suffering from combined damage modes such as creep-fatigue cracking. Risk analysis was conducted through the field inspection database for cracks at the portion under creep-fatigue conditions. The primary stage of RBM is semi-quantitative risk analysis for risk prioritization of events using risk matrixes coupled with parts breakdown trees and event trees. The secondary stage is quantitative probabilistic risk assessment (PRA) to optimize maintenance intervals for the prioritized issues. The unreliability functions were expressed in two-dimensional log-normal type probability functions of operation time and start-up cycles. As the field data include censored or sustained ones, the precise correlation factors are not always obtained from the data sets. To estimate the most likely correlation factor, the Bayesian inference was introduced to the analysis of two-dimensional probability functions. The risk functions of operation periods were obtained using the assumed operation pattern, that is, the ratio of start-up cycles to operation time by substituting this relation into the two-dimensional probability distribution functions. Total expected cost function was defined as the sum of periodical repair cost rate and the total risk cost of subject event and component. The cost function has usually the optimum cost point and it can be used as the basis of the decision making of maintenance intervals.
Energy Balance of Screw Joints in Modern Component Systems
Authors: Friedrich C. , Kopfer H. , Dinger G. , Gerhard T.
Published: May 2012

Energy Efficiency today is important for engineering design of new technical component systems; almost any design engineer knows about this. But in many cases the (design) engineers do not think about the significant contribution of optimized fastening systems. This paper shows the fundamental influences and gives examples with numeric values. Conclusions with respect to all main steps in life time are drawn which should be considered for future developments of fastening systems in energy efficient products.
Consideration of Customer Requirements in the Design Engineering of Intralogistic Systems by Multicriterial Analysis
Authors: Wieczorek Dorothee , Ku¨nne Bernd
Published: May 2012

The reliability of conveyor systems is the main requirement because of the high consequential costs in case of malfunction of intralogistic systems. In order to ensure this claim manufacturers react with robust modules of which these systems are composed. The consequence of this is that the design of intralogistic systems is not adapted to customer requirements. To develop a basis on which continuous conveyors can be designed, three Response Surface Models based on measurands have been worked out. With the help of a statistical software the response values of the models have been optimised.
Enhancement of the Availability of Intralogistic Systems by Applying the Smart Drive Concept
Authors: Eggert Jan , Ku¨nne Bernd
Published: May 2012

The determination of the overall condition of an intralogistic system is one of the significant requirements of an effective planning of maintenance activities. Conventional maintenance concepts like time-based or event-based concepts already reach their limitations. By the application of condition-based maintenance concepts the single activities take place when the reserve of abrasion of a component is nearly optimally used. The application of the smart drive concept helps to determine the condition of the system while data of stationary and mobile sensor units are gathered and evaluated. Another aspect helps to delay potential breakdowns by the adaption of certain system parameters depending on the actual system load. In that way the individual load on some components can be reduced which makes it possible to schedule an appropriate maintenance activity before the breakdown occurs. Hence the availability can be enhanced since the probability of breakdowns and unplanned maintenance activities can be reduced. To adapt system parameters based on the actual load of an intralogistic system a mathematical model is needed which describes the system behavior to a certain extent. Based on the method of DoE (Design of Experiments) such a model can be established. In the first place screening designs are necessary to determine significant factors and factor interactions. Subsequently more detailed regression experiments have to be performed to derive the mathematical model. The first step of this process (screening experiments) has been performed and will be discussed at one example in this paper while the second step which will be performed in future work (regression experiments) will be introduced and prepared. It will also be explained how the derived model will be used in a technical context at a roller conveyor as an example of an intralogistic system.
Organic Monolayers for Low Temperature Copper – Gold Bonding
Authors: Ang X. F. , Lu H. J. , Wei J. , Zhang H. J. , Wong C. C.
Published: May 2012

In this study low temperature copper-gold bonding in ambient is demonstrated successfully with the help of organic monolayers. Further investigation is made to evaluate the influence of chain length of these monolayers to alleviate bonding temperature. We found that a single coat of organic monolayer on copper showed superior bond strength as compared to a double-coating on both copper and gold surfaces respectively. Despite effective surface passivation against oxide formation (Cu) and organic contaminant from ambient (Au) by long chain organic monolayers, when both surfaces are coated with the longest monolayer, weaker bond strength was observed. The results suggest that the ease of removal of organic monolayers from Cu and Au surface respectively prior to bonding plays a dominant role in enabling low temperature Cu-Au bonding.
Thermal Management for High Power Light-Emitting Diode Street Lamp
Authors: Ying M. , Nai S. M. L. , Shi P. , Wei J. , Cheng C. K. , Lim B.
Published: May 2012

Light-emitting diode (LED) street lamp has gained its acceptance rapidly in the lighting system as one of choices for low power consumption, high reliability, dimmability, high operation hours, and good color rendering applications. However, as the LED chip temperature strongly affects the optical extraction and the reliability of the LED lamps, LED street lamp performance is heavily relied on a successful thermal management, especially when applications require LED street lamp to operate at high power and hash environment to obtain the desired brightness. As such, a well-designed thermal management, which can lower the LED chip operation temperature, becomes one of the necessities when developing LED street lamp system. The current study developed an effective heat dissipation method for the high power LED street lamp with the consideration of design for manufacturability. Different manufacturable structure designs were proposed for the high power street lamp. The thermal contact conductance between aluminum interfaces was measured in order to provide the system assembly guidelines. The module level thermal performance was also investigated with thermocouples. In addition, finite element (FE) models were established for the temperature simulation of both the module and lamp system. The coefficient of natural convection of the heat sink surface was determined by the correlation of the measurement and simulation results. The system level FE model was employed to optimize and verify the heat dissipation concepts numerically. An optimized structure design and prototype has shown that the high power LED street lamp system can meet the thermal performance requirements.
The Effectiveness of Moving Masses in Reducing the Roll Motion of Floating Vessels
Authors: Montazeri N. , Mousavizadegan S. H. , Bakhtiarinejad F.
Published: May 2012

Dynamic motions of Ships in severe conditions of sea may be undesired and should be controlled by some devices. The roll motion is much more significant than the other oscillations which can affect comfort, safety and efficiency of navigation at sea. This motion is controlled by some common stabilizers such as rudder, fins, etc. They may be divided into two categories of passive and active stabilizers or controllers. However controlling devices may be high in cost. Moving masses are employed to reduce the motions of floating vessels or offshore structures. This type of stabilizers consists of a mass with one or more springs and dampers. The movement of the mass produces an inertia force and moment to absorb wave excited motions. In this study the effectiveness of moving masses in vessels with large roll motion is investigated. A rolling vessel equipped with a moving mass can be modeled as a two-degree of freedom system. As in large amplitude roll motion the nonlinearities cannot be neglected, a mathematical model with second-order damping and fifth-order restoring moment is implemented as roll equation in beam waves. Applying to a trawler, this equation is solved simultaneously with the equation of movement of the mass in both frequency-domain and time-domain by analytical and numerical approaches. The computation shows that with an optimum passive control, a moving mass with 0.5% of the displacement of the ship is an effective device in roll minimization and enhance the vessel’s stability in high load conditions.
Enhancement of Mechanical Properties by Reinforcing Magnesium With Ni-Coated Carbon Nanotubes
Authors: Nai M. H. , Goh C. S. , Nai S. M. L. , Wei J. , Gupta M.
Published: May 2012

In this study, carbon nanotubes (CNTs) are coated with nickel (Ni) to improve the wettability of the CNT surface and metal matrix, and allow an effective load transfer from the matrix to nanotubes. Pure magnesium is used as the matrix material and different weight percentages of Ni-coated multi-walled CNTs are incorporated as the reinforcing material. The nanocomposite materials are synthesized using the powder metallurgy route followed by microwave assisted rapid sintering. Mechanical property characterizations reveal an improvement of 0.2% yield strength, ultimate tensile strength and ductility with the addition of Ni-CNTs. As such, Ni-coated CNTs can be used as a reinforcement in magnesium to improve the formability of the material for light-weight, strength-based applications.
Visualization of Thrombus Formation Process on Pipe Orifice Flows by Laser Sheet
Authors: Tamagawa Masaaki
Published: May 2012

This paper describes visualization of thrombus formation process on orifice flows by laser sheet beam. The aim is to investigate the effects of shear stress or shear rate on the thrombus formation or thrombus formation rate. In this investigation, by visualization of the thrombus formation in blood plasma flow, it was found that the high shear rate region of the flow has large effects of the thrombus formation.
Inverse Analytical and Computational Design Method Applied to a Low Pressure Axial Fan
Authors: Miclea-Bleiziffer Mihai , Epple Philipp , Delgado Antonio
Published: May 2012

Nowadays precise and reliable tools for designing and optimizing turbomachines have a high impact on industrial and research fields. The design methods of turbomachines follow usually two main paths: direct design, where performances are achieved by iteratively modifying a given geometry, and inverse design where performance characteristics are prescribed and the proper geometry for reaching them is found (usually using analytical methods). Both of these methods are used today in research and development and they are coupled with numerical simulations (CFD) for shorter design cycles. This paper proposes an inverse design approach for low pressure axial fans based upon performance equations, namely the equations for total-to-static pressure and efficiency. To validate our approach we use numerical simulation of the axial fan in a virtual test rig. Combining inverse design with the CFD for its validation offers an integrated approach for improving the design in the development phase. In the first step analytical energy equations are derived for a blade cascade section and then integrated over the blade surface, i.e. from hub to tip radii, providing a dependency of the theoretical performances characteristics such as for the pressure and the efficiency, as a function of the flow-rate, rotating speed and the outer dimensions and blade angles of the machine. The next step computes inversely the main outer dimensions and blade angles of the geometry required for reaching the performance. In the final design step the blade shape is computed inversely using a NACA 4 Digit camber as it will be shown in the paper upon the required blade angles and other constrains of the cascade. The final shape is generated in CAD software-program and then a proper computational grid is generated so that it can be finally simulated with a commercial Navier-Stokes solver for the complete pressure and efficiency characteristics. The aim of this study is to offer general conclusions about the analytical influence of certain geometry parameters on the design and optimization of axial fans of this type. The last step for the proposed design method is typically the experimental validation with prototypes which will be not covered in this study.