bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Objective Aerodynamic Design Optimization Based on Camber Line and Thickness Distribution for a Transonic Compressor Rotor
Authors: Wang Xiangfeng , Wang Songtao , Han Wanjin
Published: August 2009

The paper describes a new optimization system for computationally expensive design optimization problems of turbomachinery, combined with design of experiment (DOE), response surface models (RSM), multi-objective genetic algorithm (MOGA) and a 3-D Navier-Stokes solver. A flow field solver code was developed based on three dimensional Navier-Stokes equations and validated by comparing computation results with experimental data. The improved non-dominated sorting genetic algorithm (NSGA-II) was used to solve the multi-objective problems. A constraint handling method without penalty function used to treat constrained optimization problems was improved and applied to constrained multi-objective problems. Data points for response evaluations were selected by the improved-hypercube sampling (IHS) algorithm and 3-D Navier-Stokes analysis was carried out at these sample points. The quadratic response surface model was used to approximate the relationships between the design variables and flow parameters. The genetic algorithm was applied to the response surface model to perform global optimization and obtain the optimum design. The above optimization method was applied to aerodynamic redesign of NASA Rotor37 with camber line and thickness distribution, the objects were to maximize the total pressure ratio and the adiabatic efficiency. Results showed the adiabatic efficiency improved by 0.7% and the total pressure by 0.66%. The multi-objective optimization design method is feasible.
Position Control of Ionic Polymer-Metal Composites Using Fuzzy Logic
Authors: Radmard Sina , Honarvar Mohammad , Alasty Aria , Meghdari Ali , Zohoor Hasan
Published: August 2009

The Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers which generate large deformation under a low driving voltage. In this paper an empirical model of IPMC is developed by measuring the step response of a 23 mm×3.6 mm×0.16 mm IPMC strip in a cantilever configuration. Moreover, a model-based precision position control of an IPMC base on the fuzzy logic is presented. Open-loop position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeatability and reliability. A CCD camera was used to observe the closed loop response of the IPMC strip in order to control this electro-mechanical actuator experimentally. The IPMC actuator could follow various commanded position trajectories such as sinusoidal and square position profiles. The control architecture presented includes a fuzzy system whose structure and parameters were designed by trail-and-error beside a gain scheduled PID controller using fuzzy system. The performance of the IPMC strip is investigated and compared under these controllers.
Down the Fire Pole: Fostering Real-Time Creative Problem Solving in Students and Recent Hires
Authors: Cassino Christopher D. , Lagally Herman O.
Published: August 2009

Crisis management and emergent issue resolution are important to maintaining safe and efficient operations in the energy industry. Emergent issues include unanticipated plant complications, new component degradation mechanisms, or events that can affect outage planning and maintenance schedules. This is especially true in the nuclear power industry because of the short schedules for planned outages and maintenance programs. New hires and recent graduates are often unfamiliar with working in a high pressure environment where the consequences of their actions can have safety implications on a large scale. The Steam Generator (SG) Tube Integrity Specialists (TIS) group of Westinghouse Electric Company has developed a number of programs and policies to aid new employees in becoming familiar with emergent issues resolution during planned utility outages and during unplanned events. A summary of best company practices and how they can be applied in undergraduate and graduate education settings is provided. First, the need for more new engineers capable of handling emergent issues is discussed. Then several human performance tools used in the nuclear industry are introduced that can help technical staff perform in demanding situations. Finally, ideas are presented for integrating those tools into a classroom environment so that students can be exposed to error prevention techniques and energy industry concepts before working in the industry.
Thermodynamic Analysis of the Effects of Fuel-Side and Air-Side Oxygen Addition on Diesel Engine Combustion Characteristics and Pollutant Formation
Authors: Zannis Theodoros C. , Hountalas Dimitrios T. , Yfantis Elias A. , Papagiannakis Roussos G.
Published: August 2009

A multi-zone combustion model is used in the present study to examine the effect of increased in-cylinder oxygen availability (either by using oxygenated fuels or by increasing the oxygen percentage of intake air) on direct injection (DI) diesel engine performance characteristics and pollutant emissions. Simulations are produced for a single-cylinder DI diesel engine (“Lister LV1”) by keeping constant the oxygen content of in-cylinder fuel/air mixture and the engine brake torque. The effects of the two oxygen-enhancement techniques on combustion characteristics, soot and NO concentrations inside the combustion chamber are examined using model predictions for a common diesel oil, a neat oxygenate and the case of increasing the oxygen fraction of intake air. The multi-zone model is also utilized to interpret the relative impact of fuel-side and air-side oxygen on soot formation mechanism by examining the temporal evolution of combustion characteristics and soot formation and oxidation rates inside the fuel jet zones. Evaluation of the theoretical results revealed that the increase of in-cylinder oxygen availability by both techniques resulted in earlier initiation of combustion, increase of peak cylinder pressure and increase of in-cylinder and exhaust NO concentrations. It resulted also in reduction of exhaust gas temperature and exhaust soot values. Fuel oxygen addition was proven to be more influential on combustion process and consequently, on soot and NO formation mechanism compared to oxygen-enhancement of intake air. This is attributed to the higher oxygen availability inside each fuel jet zone, which is observed in the case of oxygenated fuel combustion.
Innovation in Curriculum Development for Manufacturing Education
Authors: Gadalla Mohamed A.
Published: August 2009

To obtain a degree in manufacturing, students traditionally faced with a decision to either join a manufacturing engineering or manufacturing technology program. Normally they make their decision based on several factors such as: the employability at that time, degree of difficulties, the degree plan and its suitability to their current living style, etc. One of the main factor that has a large weight in making their decision is the amount of math. involved in each degree. Students with less desire to get involved in the theoretical engineering science normally join the technology track while the rest join the engineering track. In this research a new degree called manufacturing engineering Technologies is proposed. The purpose of the new degree is to produce a super quality graduate who is capable of handling both the theoretical and the practical aspects in the manufacturing environment. This degree is not intended to compromise between manufacturing engineering and manufacturing technology, it is rather intended to generate a higher quality graduate. Traditionally, manufacturing engineering education focuses on the theoretical, mathematics, and experimentation aspect while manufacturing technology focuses on how to use, mange, maintain the different engineering tools and systems. The proposed degree is intended to produce a graduate that is capable of handling the theoretical and the practical issues very well. The expected performance of this graduate is to be a leader in product and system R&D, cost reduction and innovation initiatives.
A Proposed Roadmap From the Current to Agile Manufacturing
Authors: Gadalla Mohamed A.
Published: August 2009

With growing tendency towards globalization and the number of free trade agreements, we are approaching not only a global market but also a manufacturing era that has no boundaries. This is accomplished through off-shoring and outsourcing. Manufacturing companions and particularly Small to Medium size Enterprise (SME’s) are facing a very tough and fierce competition. This article is intended to provide a roadmap for manufacturing companies to help them survive and excel.
Sound Generated by Gas-Jet Impingement on the Interface of a Supercavity
Authors: Foley Alia W. , Howe Micheal S. , Brungart Timothy A.
Published: August 2009

Predictions are made of the sound produced by the impingement of ventilating air jets on the gas-water interface of a ventilated supercavity. The interface is rippled by the jets, and the unsteady surface forces exerted on the water constitute acoustic sources of dipole type. Typical gas speeds on impact do not normally exceed about 60 m/s. In these circumstances the very large difference in the densities of the gas and water imply that the dynamics of the jet-wall interaction are, in a first approximation, similar to those occurring when a jet impinges on a rigid wall. An independent, canonical experiment is performed to determine the frequency spectrum of the surface force distribution produced by a single turbulent jet impinging on a wall, for several different injection flow rates and jet lengths, and thence to estimate the sound produced in the water when the same jet impinges on the cavity interface. The result is used to predict the contribution produced by this mechanism to the overall water borne noise generated by a specially constructed supercavitating body used at the Applied Research Laboratory at Penn State University, for which the ventilating gas enters the cavity axisymmetrically through a series of radially orientated nozzles equally spaced around a gas injector ring. A comparison is made with predictions based on force measurements of Strong, et al. [1].
Torque and Power-Flow Analyses of Two Input Epicyclic-Type Transmission Trains
Authors: Esmail Essam L. , Hassan Shaker S.
Published: August 2009

This study contributes to the development of a systematic methodology for the torque and power flow analyses of two-input epicyclic gear mechanisms (EGMs) with or without reaction link, based upon the concept of fundamental circuit. The studies on power flow analysis of EGMs are mostly done in the context of efficiency formulations. In the opinion of the authors, the design process of two-input mechanism involves not only finding the configuration that provides the correct velocity ratios, but also meets other dynamic and kinematic requirements and ensures that the two inputs have a mutually constructive nature. To demonstrate the analysis, a new motor/generator integrated hybrid transmission design is used to show how the torque acting on each link of an epicyclic gear train (EGT) can be systematically solved in terms of input torque(s) and/or controlled output torque. This paper presents a unification of kinematic and torque balance approaches for the analysis of two-input epicyclic-type transmission trains. The results presented are meant to deepen the knowledge as to how and why a two-input epicyclic-type transmission should operate in a certain way under the given conditions. In the process, this paper explores the theoretical bases of operation of the Toyota Hybrid System (THS) and the root cause of some confusion in the field of EGTs.
Design and Validation of an In-Mold Shrinkage Sensor
Authors: Panchal Rahul R. , Kazmer David O. , Gao Robert X.
Published: August 2009

Dimensional consistency is a critical attribute of molded products, yet part dimensions are frequently only estimated from cavity pressure or part weight measurements. An in-mold shrinkage sensor is designed and validated. The design includes a deflectable diaphragm instrumented with strain gages connected in a full bridge circuit. In operation, the diaphragm is deflected due to the pressure of the melt in the mold cavity. Molded part shrinkage is then measured as the polymer melt solidifies, shrinks, and retracts from the mold wall. A design of experiments is conducted to validate the performance of the sensor as a function of packing pressures, cooling time, melt temperature, and coolant temperature. The results indicate the sensor outperforms both cavity pressure transducers and regression models, and is able to measure the shrinkage to an absolute accuracy of 0.01 mm for a 2.5 mm thick part.
A Multi-Scale Modeling Based Theory for Mechanical Load Induced Cell Damage in a 3D Cell-Encapsulated Alginate Tissue Construct
Authors: Yan Karen Chang , Nair Kalyani , Sun Wei
Published: August 2009

Bio-fabrication methods utilize mechanical means to manufacture products with living cells incorporated. During the fabrication process, cells are involuntarily manipulated and/or exposed to mechanical disturbances that may not be present in the normal physiological environment. One of fundamental questions that need to be answered is whether cells remain viable and/or functional when subjected to mechanical disturbances. This paper presents the development of a theory that can address relation between applied mechanical forces and cellular response from a mechanics point of view. Specifically, a 3D multi-scale numerical model is developed and applied to determine the stress and deformation fields at the cellular level when the tissue construct is subjected to macro-level loads. Based on the detailed information rendered for the micro stress and deformation fields, a general theory is then formulated. A simulation for a 3D alginate tissue construct with encapsulated cells under uniform compression is conducted to illustrate the solution technique. Comparison between the predicted cell viability and experimental data demonstrates that the proposed theory is capable of capturing the experimental trend.
An Assessment on the FCM Classification of Thermodynamic-Property Data
Authors: Avila Gabriela , Pacheco-Vega Arturo
Published: August 2009

In the present study we consider the algorithmic classification of thermodynamic properties of fluids using the fuzzy C-means (FCM) clustering methodology. The FCM is a technique that can find patters directly from the data. It is based on the minimization of an objective function that provides a measure of the dissimilarity of the data being classified in a particular group. The dissimilarity in the data is commonly formulated in terms of the Euclidean distance between the data points and the cluster centroids. This mathematical formulation and the efficient implementation are among its advantages. However, some drawbacks that lead to misclassification include the convergence to local optima, the particular form of the data, and the choice of the parameters embedded in the scheme. To assess the correct classification performance of FCM algorithm, published data of pressure, volume, and temperature are used with emphasis on the way the algorithm is affected by the natural scale of the data, and the following strategies for the classification: (1) data normalization, (2) transformation, (3) sample size used, and (4) data supply to the algorithm. The results of this assessment show that the natural scaling, and the normalization and transformation strategies are important, whereas the way the data are presented to the algorithm is not a critical factor in the classification. Also, a decrease in the number of data considered degrades the quality of the clustering. A complete consideration of the issues studied here may be helpful when a FCM classification is tried on new data.
Integral Micro-Channel Packages for Enhanced Thermal Performance
Authors: Solovitz Stephen A. , Conder Thomas E.
Published: August 2009

Modern advancements in transistor technology have pushed thermal dissipations from power electronics near the edge of the capability of single-phase micro-channel designs. To alleviate this problem, researchers have begun investigating enhancements to these designs, using methods such as pin fins, turbulators, and impinging jets. These techniques can potentially enhance the convective thermal performance by a factor of 2 to 3, although they do incur a similar magnitude pressure penalty. However, because of the requirements of electrical isolation and mechanical assembly, much of this benefit is tempered, as the convective thermal resistance is only a small fraction of the total resistance. This limitation can be removed through the use of an integral package design where the heat sink passages are fashioned in the electrical stack, which can reduce the conductive resistance until convective enhancements are significant again. These methods include fabrication of micro-channels directly into the active metal braze substrate and potentially even the electrical insulation layer. Thus, while a traditional, non-integral design only experiences a 5% overall benefit when the convective resistance is reduced by 50%, an integral package can have a 20 to 30% improvement for the same enhancement. To examine this capability, a series of computational fluid dynamics studies were conducted to study the performance of several integral micro-channel heat sink configurations. These simulations determined the response for a range of coolants, flowrates, device power dissipations, and operating conditions. These results will serve as a baseline for further development of enhanced, integral micro-channel designs.
A Study of a Variable Compression Ratio Engine With a Double Piston System
Authors: Kondo Takashi , Hirano Makoto
Published: August 2009

Improvement in the thermal efficiency of automobile engines is being demanded as a means to reducing carbon dioxide emissions, which are considered to be the main cause of global warming. Improving thermal efficiency by means of higher compression ratios is known. But, in the case of gasoline engines, there is a limit for high compression ratios caused by knocking under high load conditions. Therefore, various variable compression ratio (VCR) mechanisms have been devised. However, in previous attempts, structural issues have arisen, whereby structural weight has increased, thereby necessitating excessive power at the time of operation. Previous attempts have also necessitated the makeup of an exclusive engine design, which therefore has not been practically utilized. In this study, a double piston method was devised. This mechanism enables the remodeling of a VCR engine through the replacement of only the piston system without changing the dimensions of the engine. In addition, this mechanism operates by piston inertial force. Therefore, it does not need excessive power and enables a lightweight, power-saving engine. In this paper, the basic characteristics of the prototype VCR engine are described based on the experimental results obtained in tests conducted with the engine.
Measurement and Analysis of Adhesion Phenomena in High Speed Train
Authors: Nankyo Masanobu , Nakazawa Shin-Ichi
Published: August 2009

Performance of acceleration or deceleration of railway vehicles is limited to adhesion force. It is well known that adhesion coefficient between wheel and rail tread has some difficult characteristics; one of them is its descending tendency with the ascent of rolling speed particularly under water lubricant condition. We need to know these characteristics as quantitative descriptions, and arrange them to an easy-to-use way for design of running gear such as powering or braking devices. In this paper, a measurement technique on operating train and an advanced evaluation method of the adhesion coefficients are introduced.
Identifying the Mechanisms of Enhanced Water Flow Through Carbon Nanotubes
Authors: Thomas J. A. , McGaughey A. J. H.
Published: August 2009

Pressure-driven water flow through carbon nanotubes (CNTs) with diameters ranging from 1.66 nm to 4.99 nm is examined using molecular dynamics simulation. The flow rate enhancement, defined as the ratio of the observed flow rate to that predicted from the no-slip Hagen-Poiseuille relation, is calculated for each CNT. The enhancement decreases with increasing CNT diameter and ranges from 433 to 47. By calculating the variation of water viscosity and slip length as a function of CNT diameter, it is found that the results can be fully explained in the context of continuum fluid mechanics. The enhancements are lower than previously reported experimental results, which range from 560 to 100000, suggesting a miscalculation of the available flow area and/or the presence of an uncontrolled external driving force (such as an electric field) in the experiments.
Flow of Microsphere Solutions in Converging Microchannels
Authors: Reedy Alexis B. , Macken Nelson
Published: August 2009

The interface between intersecting microfluidic multicomponent flow is investigated experimentally. The system studied has a main channel and an intersecting (at 90 degrees) daughter channel and the fluid is a water-microsphere mixture. Flow visualization is achieved using confocal fluorescence microscopy. Microsphere solutions of 2% and 4% spheres (by weight) are investigated and compared to each other as well as all water flows. A three-dimensional rendering of the location and shape of the interface at the junction for different flow ratios (daughter flow to total) is examined for a combined flow Reynolds number of approximately one. The interface downstream of the junction is reasonably planer (two-dimensional) and the presence of microspheres does not appear to strongly influence the location of the flow interface.
Micromechanical Resonators With Near-Linear Response
Authors: Vummidi Krishna , Abdel-Rahman Eihab M. , Hammad Bashar K. , Raman Sanjay , Nayfeh Ali H.
Published: August 2009

We study the effect of bias voltage VDC on the effective nonlinearity of electrostatically clamped-clamped microbeam resonators. We identify three domains in the resonator response: hardening-type, softening-type, and near-linear behaviors. In the near linear domain we show that we can increase the power handling of the resonator without distorting its phase noise performance. We investigate the mixing of low frequency 1/f noise into the input signal. This causes phase distortion of the output signal and is quantized as its phase noise. We find that the amplitude and phase responses of the resonator’s displacement are coupled to each other through the effective non-linearity co-efficient (S), which distorts its phase response in the nonlinear regime. Finally we also present closed form expressions for resonator displacement and current in both linear and non-linear regimes.
Autonomous Parking Strategy
Authors: Moshchuk Nikolai , Chen Shih-Ken
Published: August 2009

Parallel parking can be a difficult task for novice drivers or drivers who seldom drive in congested city where parking space is limited. Parking Assist is an innovative system designed to aid the driver in performing sometimes difficult parallel parking maneuvers. Many companies are developing such systems with major automakers, such as Valeo, Aisin Seiki, Hella, Robert Bosch, and TRW. For example, Toyota IPA (Intelligent Parking Assist) system uses a rear view camera and automatically steer the vehicle into the parking spot with driver controlling braking. This paper describes the development of parking path planning strategies based on available parking space. A virtual turn center will first be defined and derived based on vehicle configuration. Required parking space for one or two cycle parking maneuver will then be determined. Path planning strategies for both one and two turn parking maneuvers will be developed next. Finally CarSim simulation will be performed to verify the design.
Emissions From Direct or Indirect Combustion of Tire-Derived-Fuel
Authors: Levendis Yiannis A.
Published: August 2009

This paper reports on partial results of a comprehensive laboratory investigation on the emissions from batch-combustion of tire-derived fuel (TDF) in the form of waste-tire chips placed in fixed beds. TDF is a fuel of technological interest based on its high-energy content, in the range of 30–39 MJ/kg. However, there have been issues with health-hazardous emissions from the combustion of tires. The overall goal of the investigation has been to identify techniques and conditions that minimize toxic emissions. This particular work contrasts emissions from direct combustion of TDF with those from indirect combustion, i.e., staged pyrolysis of TDF followed by combustion of the pyrolyzates. Generation of a pyrolysis gas from TDF allows for effective mixing of this gas with air and, hence, for better control of the subsequent combustion and minimization of pollutant emissions. Emissions CO2, CO, semi-volatile polycyclic aromatic hydrocarbons (PAH) and particulates were monitored herein. Results illustrated that the staged pyrolysis-oxidation approach, albeit more complicated, has the potential for low health-hazardous emissions from waste tire-to-energy plants. It produced drastically less PAH (by up to an order of magnitude) and particulates (by more than an order of magnitude). However, it produced more CO and NOx (by factors of 2–5). The presence of an afterburner (1 s residence time at 1000 °C), curtailed the emissions of CO and, interestingly, it was capable of nearly-equalizing the final emissions of PAH from the two different modes of combustion. However, the afterburner treatment was not as successful in reducing the emissions of particulates and, as a result, the indirect combustion of TDF produced an effluent with a drastically lower particulate loading.
Optimal Design of Tank Shield of an Electrical Locomotive Main Transformer Based on 3-D Eddy Current Analysis
Authors: Dai L. , Luo L.
Published: August 2009

This research focuses on the optimal design of the transformer oil tank shield of an electrical locomotive which has the operating speed of 160km/h. The analysis of 3-D eddy current loss in the magnetic leakage field of the tank shield is performed in the research. The optimization of the three-dimensional geometry of the tank shield is also carried out. Based on the analysis of 3-D eddy current loss in the magnetic leakage field of the tank of the main transformer for 200km/h electrical locomotive, an optimal model of the tank shield of the transformer is developed and optimized by using the algorithm of sub-problem approach. The research results show that it is efficient to combine the optimized algorithm with the FEM analysis in optimizing the design of electromagnetic equipment.
Stress Simulation on Elements of Metal Pushing V-Belt for Fatigue on CVT at Start-Up
Authors: Saito Toshihiro
Published: August 2009

As the demand for improved automotive environmental performance increases, manufacturers are focusing on the CVT as a transmission type enabling the achievement of a balance between driving performance and fuel efficiency. In terms of driving performance, CVT offers quietness and smooth acceleration without shift shock. Given this, the requirement to extend the transmission capacity of CVT will increase in future. From the perspective of the maximum input torque that is transmitted to the drive train, the most severe demands are made on the CVT at start-up operation. The pulleys and metal pushing V-belt of a CVT with a torque converter are subjected to a sudden rapid increase in pulley thrust from a stationary state, and are required to transmit maximum torque with minimal time lag. The most important consideration at this time is the dynamic strength of the metal pushing V-belt. Dynamic strength cannot be determined simply from the maximum input torque, but must be determined in relation to the shift ratio, pulley piston pressure as well as the rated speed in time history. This paper reports on research that has succeeded, using a new simulation, in clarifying the stress history on the element neck under transient operating condition at CVT start-up. These results suggest that the compression stress generated by the load on the V surface is a fundamental component of element stress, and that bending stress generated by the pushing force between the elements is superimposed on this stress. A comparison of simulation results with test results for the load distribution on the element, conducted to confirm the accuracy of the simulation, demonstrated good qualitative correlation. This paper also discusses the method used to evaluate dynamic strength in response to transient stress and the application to a variety of vehicle start-up conditions to make it possible to determine operating conditions by considering the dynamic strength of the belt.
Estimation of AE Parameters for Monitoring Bearing in a Lathe Using Multiple Regression and GMDH
Authors: Sathish Kumar K. M. , Ravindra H. V.
Published: August 2009

Bearings are among the most widely used machine elements and are critical to almost all forms of rotating machines. In order to prevent unexpected bearing failure, defects that can occur in bearings should be detected as early as possible. It is widely recognised that Acoustic Emission (AE) is gaining ground as a monitoring method for health diagnosis on rotating machinery. The advantage of AE monitoring over vibration monitoring is that the AE monitoring can detect the growth of subsurface cracks whereas the vibration monitoring can detect defects only when they appear on the surface. The present work involves studying the variation of AE signals obtained from spindle bearing housing of a lathe for various cutting conditions. Simple functional relationships between the parameters were plotted to arrive at possible information on bearing condition. But these simpler methods of analysis did not provide any information about the status of the bearing. Thus, there is a requirement for more sophisticated methods that are capable of integrating information from multiple sensors. Hence, methods like multiple regression analysis and GMDH have been applied for the estimation of AE Counts and AE Energy. From the Experimental data it was observed that as the cutting condition increases there is an increase in the signal level of AE parameters. This is due to increase in load acting on the bearing at higher cutting conditions. Estimates from multiple regression and GMDH were compared and it was observed that, GMDH with regularity criterion gives better results.
A Numerical Study of Three-Dimensional Convective Heat Transfer From a Window Covered by a Simple Partially-Open Plane Blind
Authors: Oosthuizen Patrick H. , Basarir Murat , Naylor David
Published: August 2009

Heat transfer from the room-side surface of a window covered by a plane blind to the surrounding room has been considered. The window is at a higher temperature than the air in the room. There is an open gap between the blind system and the window at the top of the window and the effect of the size of this gap on the window-to-air heat transfer rate has been numerically examined. Three-dimensional flow has been considered. The flow has been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. It has also been assumed that the flow is symmetrical about the vertical centre-plane of the window. The solution has been obtained by numerically solving the full three-dimensional form of the governing equations, these equations being written in terms of dimensionless variables. Results have only been obtained for a Prandtl number of 0.7. The effects of the other dimensionless parameters on the window Nusselt number have been numerically determined.
Strength Evaluation of Polymer Composite Spur Gear by Finite Element Analysis
Authors: Hossan Mohammad Robiul , Hu Zhong
Published: August 2009

Modern advanced polymer composite materials have opened a new level of noiseless, lubricant free, high resilience and precision gearing in power and motion transmission. The proper understanding and evaluation of gear strength and performance is an important prerequisite for any reliable application. In this paper, a 20% short glass fiber reinforced nylon66 spur gear fabricated by injection molding has been carefully investigated. A three-dimensional finite element model was used to simulate the multi-axial stress-strain behaviors of a gear tooth under the dynamic load for a complete working cycle with a special geometry, operating condition, fiber orientation and volume fraction. The strength of composite gears has been compared with isotropic un-reinforced nylon66 and steel gears. The tooth root region of a gear which usually experiences high stress and potential to failure has been carefully investigated. This computer simulation method can be used as a useful tool for evaluating strength and predicting failure of the polymer composite gears.
A Novel Course in Product Innovation
Authors: Vallee Glenn E.
Published: August 2009

A novel course in Product Innovation has been developed at Western New England College which partners teams of senior level mechanical engineering students with local companies for the purpose of bringing fresh insights to the development of new and innovative products. Students benefit through exposure to real-world corporate environments, time to market pressures and contact with all departments typically involved in the New Product Development (NPD) process. Participating corporations benefit from the unique and often revolutionary ideas developed by students who have no preconceived notions about potential innovations, and by a renewed enthusiasm brought to the process by the students. Students perform benchmarking analyses, conduct consumer and market research, and develop functional prototypes of the new product concepts. Participating corporations support the course by providing funding for prototype fabrication and the purchase of benchmark samples, as well as engineering, marketing and sales support throughout the NPD process. To date, 60% of the products developed in the course have been approved for further development by the participating companies. The course has proven to be so successful that the School of Engineering at Western New England College is considering expanding the course to an interdisciplinary, two semester experience.
Lift Generation in Soft Porous Media Under Rapid Compaction
Authors: Barabadi Banafsheh , Nathan Rungun , Wu Qianhong
Published: August 2009

In a recent paper, Wu et al. (Journal of Fluid Mechanics 542, 281 (2005)) have developed a novel experimental and theoretical approach to investigate the dynamic lift forces generated in the rapid compression of highly compressible porous media, (e.g. snow layer), where a porous cylinder-piston apparatus was used to measure the pore air pressure generation and a consolidation theory was developed to capture the pore pressure relaxation process. In the current study, we extend Wu et al.’s approach to various porous materials such as synthetic fibers. A complete redesign of the previous experimental setup was done, where an accelerometer and a displacement sensor were employed to capture the motion of the piston. The pore pressure relaxation during the rapid compaction of the porous material was measured. The consolidation theory developed by Wu et al. was modified by introducing the damping effect from the solid phase of the materials. One uses Carman-Kozeny’s relationship to describe the change of the permeability as a function of compression. By comparing the theoretical results with the experimental data, we evaluated the damping effect of the soft fibers as well as that of the pore air pressure for two different synthetic fibers, A and B. The experimental and theoretical approach presented herein has provided an important methodology in quantifying the contributions of different forces in the lift generation in soft porous media and is an extension of the previous studies done by Wu and others.
Simulation of Molded Micro Components and Systems With Regard to the Grain Structure
Authors: Albers Albert , Enkler Hans-Georg , Leslabay Pablo
Published: August 2009

Miniaturization of macroscopic mechanical systems enables the opening of new areas of application for micro technological systems. Because of actual technological restrictions, especially when applying miniaturized conventional manufacturing techniques, shape and material deviations can not be decreased as strong as the dimensions of the micro parts are reduced. A long-term objective in the development of such systems is to ensure functional capability by adoption of appropriate design measures that compensate these deviations. This work presents methods based on computer simulation that contribute to achieve this objective. One method is based on the utilization of ad-hoc modified and simplified Finite Element Analysis techniques, which now regards some issues of interest from Multi Body Simulation. The introduction of this method also allows studying the behavior of the components and the system with regard to the component’s internal grain structure. When the focus is directed to the robustness or the reliability of the system, another method is presented that is based on a hybrid FEA-MBS solver. It shows better performance both on parameters modeling capability and computational efficiency. Methods to overcome the above mentioned issues, as well as the effects of grain structure on the stress distribution in the individual components will be presented. Some effects affecting the system’s behavior because of this inhomogeneous stress distribution are also discussed. Finally, an investigation about the consequences of having internal defects within individual components is conducted.
On Length Scales for the Radial Rotating Jet Pressure Exchange Mechanism
Authors: Umar Muhammad , Garris Charles A.
Published: August 2009

The crypto-steady rotating jet pressure exchange ejector is a novel concept in turbomachinery where two fluids, at different energy levels, come in direct contact with each other to transfer energy and momentum between them through non-steady interface pressure forces. The current paper seeks to provide an insight into the complex flow phenomena occurring inside the radial flow pressure exchange ejector. The primary mechanisms controlling the process are pressure exchange and mixing. This paper will seek to discriminate between energy transfer by each respective mechanism. The energy and momentum transfer in the near field is shown to be mainly due to the pressure exchange process, as the mixing layer does not develop substantially in this region. As the radius increases, the mixing layer tends to grow and the energy and momentum transfer is governed by the mixing process. As a consequence, the length scales of the pressure exchange zone are small, thus making the pressure exchange ejector more compact in size. The paper will delineate between the two length scales. If this new concept is shown to be viable for gas compression at sufficiently high pressure ratios, then, in refrigeration applications, it would enable environmentally benign refrigerants to replace the harmful chlorofluorocarbons (CFC) and reduce the effluence of greenhouse gases. Applications in many other areas, where conventional ejectors are currently used, are also possible.
Effect of Inhaling Patterns on Aerosol Drug Delivery: CFD Simulation
Authors: Kim Jinho , Chen Jim S.
Published: August 2009

Inhaled Pharmaceutical Aerosols (IPAs) delivery has great potential in treatment of a variety of respiratory diseases, including asthma, pulmonary diseases, and allergies. Aerosol delivery has many advantages. It delivers medication directly to where it is needed and it is effective in much lower doses than required for oral administration. Currently, there are several types of IPA delivery systems, including pressurized metered dose inhaler (pMDI), the dry powder inhaler (DPI), and the medical nebulizer. IPAs should be delivered deep into the respiratory system where the drug substance can be absorbed into blood through the capillaries via the alveoli. Researchers have proved that most aerosol particles with aerodynamic diameter of about 1–5 μm, if slowly and deeply inhaled, could be deposited in the peripheral regions that are rich in alveoli [1–3]. The purpose of this study is to investigate the effects of various inhaling rates with breath-holding pause on the aerosol deposition (Dp = 0.5–5 μm) in a human upper airway model extending from mouth to 3rd generation of trachea. The oral airway model is three dimensional and non-planar configurations. The dimensions of the model are adapted from a human cast. The air flow is assumed to be unsteady, laminar, and incompressible. The investigation is carried out by Computational Fluid Dynamics (CFD) using the software Fluent 6.2. The user-defined function (UDF) is employed to simulate the cyclic inspiratory flows for different IPA inhalation patterns. When an aerosol particle enters the mouth respiratory tract, its particles experience abrupt changes in direction. The secondary flow changes its direction as the airflow passes curvature. Intensity of the secondary flow is strong after first bend at pharynx and becomes weaker after larynx. In flow separation, a particle can be trapped and follow the eddy and deposit on the surface. Particle deposition fraction generally increases as particle size and inhaling airflow velocity increase.
General Robust Design by Semi-Second-Order Taylor Expansion
Authors: Du Xiaoping
Published: August 2009

The purpose of robust design optimization is to minimize variations in design performances and therefore to make the design insensitive to uncertainties. Current robust design methods fall into two types — probabilistic robust design and worst-case (interval) robust design. The former method is used when random variables are involved. In this method, robustness is measure by standard deviations of design performances. The later method is used when uncertainties are represented by intervals. The widths of design performances are then used to measure robustness. In many engineering application, both random variables and interval variables may exist simultaneously. In this paper, a general approach to robust design optimization is proposed. The generality comes from the ability to handle both random and interval variables. To alleviate the computational burden, we employ a previously developed general robustness assessment method — semi-second-order Taylor expansion method, to evaluate the maximum and minimum standard deviations of a design performance. An efficient integration strategy of the general robustness assessment and optimization is proposed. With the integration strategy, the number of function calls can be reduced while good accuracy is maintained. A robust shaft design problem is given for demonstration.
Predicting Phonon Thermal Conductance at Atomic Junctions: Nonequilibrium Green’s Function Approach Compared to Semiclassical Methods
Authors: Hopkins Patrick E. , Norris Pamela M. , Tsegaye Mikiyas S. , Ghosh Avik W.
Published: August 2009

Phonon thermal conductance, λ, in nanostructures is a thermophysical property that is becoming increasingly difficult to accurately predict, especially as thermal management at interfaces of different materials is becoming a major engineering concern. The most widely used models for λ prediction are based on the Boltzmann Transport Equation (BTE), and the when junctions between two different materials enter the picture, the most common BTE-based models to predict the interfacial conductance are the Acoustic Mismatch Model (AMM) and Diffuse Mismatch Model (DMM). The models are developed with equilibrium assumptions. However, thermal transport is clearly nonequilibrium phenomenon. Recently, the Nonequilibrium Green’s Function (NEGF) formalism has been extended to phonon transport. The NEGF formalism is rooted in nonequilibrium quantum transport theory, making it ideal to study energy transfer applications, especially in nanosystems where the concept of thermal equilibrium breaks down due to the small dimensions of the transport regions. The purpose of this paper is to derive, from first principles, the NEGF formalism of thermal conductivity, and compare the assumptions of this formalism to the semi-classical Boltzmann models. The NEGF formalism is applied to a 1D atomic chain with varying masses and compared to similar predictions from BTE-based models.
Nanoscale Heat Transfer Course for Undergraduates
Authors: Hopkins Patrick E. , Norris Pamela M.
Published: August 2009

The growing interest in nanoscale energy transfer research and funding in mechanical engineering departments far out weighs the availability for formal training of fundamental ideas and concepts in this area. Although several universities offer formal graduate courses in nanoscale energy transfer, these courses are often a survey of current research and are typically geared to graduate students or advanced undergraduates with a stonger physics background than the typical undergraduate engineering student. The goal of this paper is to outline a course that is designed to teach fundamental nanoscale energy transfer concepts to the undergraduate engineering student who has not taken advanced physics courses outside of the ABET approved mechanical engineering curriculum. A survey of different nanoscale energy transfer courses from various institutions around the world is discussed in specific context of the benefits for the typical mechanical engineering undergraduate. The limited textbooks that are available on the subject are also discussed. An outline of fundamental topics in quantum physics, statistical mechanics, and solid state physics is presented as important concepts that the typical undergraduate should understand in order to understand basic research and principles of nanoscale energy transfer. Important phenomena and techniques in nanoscale energy transfer research are also discussed. This course was taught as an undergraduate and graduate engineering elective at the University of Virginia in the spring semester of 2008.
Thin Film Thermal Conductivity by Anharmonic Lattice Dynamics Calculations
Authors: Turney J. E. , McGaughey A. J. H. , Amon C. H.
Published: August 2009

Lattice dynamics calculations are used to investigate thermal transport in argon thin films with thicknesses ranging between one and ten nanometers. Quasi-harmonic lattice dynamics calculations are used to find the frequencies and mode shapes of non-interacting phonons. This information is then used as input for anharmonic lattice dynamics calculations, whereby we compute the frequency shift and lifetime of each phonon mode due to interactions with other phonons. The phonon frequencies, group velocities, and lifetimes determined with the lattice dynamics techniques are then used to compute the in-plane thermal conductivity of the thin films as a function of film thickness. The thermal conductivities predicted by the lattice dynamics methods are compared to predictions from molecular dynamics simulations. Differences in the phonon characteristics in thin films compared to bulk crystals are examined by comparing the contribution to the thermal conductivity as a function of frequency.