bluuebunny/crossref_metadata_2025 huggingface dataset:
Multifunctional Structure-Battery Materials for Enhanced Performance in Small Unmanned Air Vehicles
Authors: Thomas James P. , Keennon Matthew T. , DuPasquier Aurelien , Qidwai Muhammad A. , Matic Peter
Published: May 2008

We have developed a new multifunctional structure battery material that replaces unifunctional structure in a micro-air vehicle (MAV) for the purposes of increasing the flight time endurance. Multiple layers of thin plastic lithiumion bicell battery material were combined with packaging and used as wing-skin in a developmental multifunctional MAV named WASP. This WASP vehicle has successfully demonstrated 107-minutes of continuous flight. Endurance flight time increases of ∼26% are predicted for multifunctional designs using the best available (highest specific energy) battery material as wing-skin.
Prediction of Low Temperature Hot Corrosion Rate in Film Cooled Coal Fired Gas Turbines
Authors: Krishnan Vaidyanathan , Bharani Sanjeev , Kapat J. S. , Sohn Y. H. , Desai V. H.
Published: May 2008

The concept of coal based gas turbine power plants has drawn considerable interest in recent years. Coal or syngas based power plants like IGCC have shown significant potential for meeting the ever-increasing power demands as well as stricter environmental regulations. The trouble free operational life of such power plants is limited by a major factor namely hot corrosion of the turbine components. Hitherto, the mechanism of hot corrosion has been investigated in a simpler context, which is not directly applicable to gas turbines in the presence of film cooling techniques. The present paper is an attempt to model hot corrosion in the presence of film cooling relevant to gas turbines, using a simple resistance model and the inherent analogy between heat and mass transfer. This paper considers film cooling air temperatures in the range of 450°C to 550°C, and a free stream gas temperature of 1425°C, with 0.5% sulfur in the fuel. For lower cooling air temperatures (less than 500°C), film cooling air suppresses corrosion, whereas for higher cooling air temperature corrosion rate is more in the presence of film cooling. With film cooling, there is a sharp peak in corrosion rate close to the cooling hole (within 10 slot widths). Due to the possibility that the base superalloy may be exposed in this region, designers should consider the high corrosion rate seriously. However, the present model is limited in its prediction because of its simplicity. Further improvement of the model is essential for optimization purposes.
Dynamic Analysis of Flexible Supercavitating Vehicles Using Modal Based Elements
Authors: Choi Jou-Young , Ruzzene Massimo , Bauchau Olivier A.
Published: May 2008

This presents a numerical model for the simulation of the flight mechanics behavior of flexible supercavitating vehicles. Supercavitating vehicles exploit supercavitation as a means to reduce drag and increase the underwater speed. In the proposed formulation, the vehicle’s rigid body motion is described by 6 degrees of freedom, which define pitch, yaw and roll motion and the displacement of the center of gravity with respect to a fixed inertial reference system. The forces applied to the vehicle include the control actions at the nose and at the fins, propulsion, gravity and cavity/vehicle periodic interactions associated to typical operating conditions. The elastic displacements are superimposed to the rigid body motion through a modal superposition technique. The mode synthesis is performed using Herting’s Transformation, which provides maximum flexibility in the selection of the elastic modes to be used for the used for the superposition, and the possibility of easily handling free-free modes. The developed numerical model predicts the dynamic response of the considered class of supercavitating vehicles resulting from assigned maneuvers. The analysis is motivated by the need of accurately modeling the structural characteristics of supercavitating vehicles in order to estimate vibrations in the structure and to envision and design systems that improve their guidance and control efficiency.
A Novel Transition-Sensitive Conjugate Methodology Applied to Turbine Vane Heat Transfer
Authors: York William D. , Walters D. Keith , Leylek James H.
Published: May 2008

A documented numerical methodology for conjugate heat transfer was employed to predict the metal temperature of an internally-cooled gas turbine vane at realistic operating conditions. The conjugate heat transfer approach involves the simultaneous solution of the flow field (convection) and the conduction within the metal vane, allowing a solution of the complete heat transfer problem in a single simulation. This technique means better accuracy and faster turn-around time than the typical industry practice of multiple, decoupled solutions. In the present simulations, the solid and fluid zones were coupled by energy conservation at the interfaces. In the fluid zones, the Reynoldsaveraged Navier-Stokes equations were closed with a three-equation, eddy-viscosity model, developed in-house and previously documented, with the capability to predict laminar-to-turbulent boundary-layer transition. The single-point model is fully-predictive for transition and requires no problem-dependent user inputs. For comparison, a simulation was also run with a commercially available Realizable k-ε turbulence model. A high-quality, unstructured gird was employed in both cases. Numerical predictions for midspan temperature on the airfoil surface are compared to data from an open-literature experiment with the same geometry and operating conditions. The new model captured transition of the initially laminar boundary layer to a turbulent boundary layer on the suction surface. The results with the new model show excellent agreement with measured data for surface temperature over the majority of the airfoil surface. The new model showed a marked improvement over the Realizable k-ε model in all regions where laminar boundary layers exist, highlighting the importance of accurately modeling transition in turbomachinery heat transfer simulations.
Three-Dimensional Transient Residual Stress Finite Element Analysis for a Laser Clad Surface
Authors: Ghosh S. , Choi J.
Published: May 2008

Laser aided manufacturing process inherently includes many nonlinear and non-equilibrium transport phenomena due to non-uniform and rapid heat flow caused by the laser and the material interaction. Comprehensive understanding of the transport phenomenon and heat transfer analysis including phase transformation is essential to predict the effects of thermally induced residual stresses and distortions in deposited materials. It not only helps to improve the process but also reduces the long and cumbersome experimental route to compile sufficient data to predict the material behavior under similar loading conditions. This paper is an attempt towards a methodology of finite element analysis for the prediction of quenching related macroscopic as well as microscopic residual stress in a laser cladding process. A finite element program has been written to account for the micro-residual stress effects. The program is essentially a coupling between a preliminary estimation of temperature history of the system and the final prediction of residual stresses which also include the phase transformation kinetics of the material during its cooling. The importance of considering phase transformation effects during quenching is also verified through the comparison of the magnitudes of residual stresses with and without the inclusion of phase transformation kinetics. The FEA program for this model is a very useful tool for designing and optimizing Laseraided Direct Metal Deposition (DMD) process conditions so that products with the best internal quality and dimensional accuracy can be built.
Modeling and Analysis of RF MEMS Filters
Authors: Motiee Mehrnaz , Khajepour Amir , Mansour Raafat R.
Published: May 2008

In this paper, new designs for IC-compatible microelectromechanical intermediate frequency filters are introduced. These filters have been fabricated using the multiuser polysilicon surface micromechining process, MUMPs [1]. They composed of two cantilever beam micromechanical resonators coupled by a soft flexural-mode beam. Different configurations of the resonators coupled together along with their RF responses are presented. One of the advantages of these cantilever resonators is that coupling elements can be added from more than one side in order to fabricate filters with elliptical responses. A step-by-step flow-chart for lumped modeling approach is presented, which allows a fast and accurate modeling and optimizing of the structures. In the modeling all the distributed structure and multi-physics parameters of the problem are considered. With the help of finite element analysis from CoventorWare software [2], validity and accuracy of the lumped modeling is investigated. Presented filters have center frequencies varying from 390 kHz to 1.1 MHz, quality factors of 3000 to 5000 and associated insertion losses of less than −2 dB.
Artificial Plasmonic Metamaterial Fabricated by Micro-Stereolithography
Authors: Wu Dongmin , Fang Nicholas , Sun Cheng , Zhang Xiang , Padilla Willie J. , Basov Dimitri N. , Smith David R. , Schultz Sheldon
Published: May 2008

Micro-structured materials, which contain engineered subwavelength components, can be designed to have positive or negative ε and μ at desired frequency. In this paper, we demonstrate a high pass Terahertz (THz) filter which utilizes the lowered plasma frequency of thin metal wire structures. This high pass filter may have applications in the THz imaging systems. The filter is formed by two-dimensional cubic lattice of thin metal wires. The diameter of the wire is 30 μm, the lattice constant is 120 μm, and the length of the wire is 1mm. Micro-stereolithography technique is applied to fabricate this high aspect ratio cylinders. The reflection property of the filter is characterized by Fourier transform infrared (FTIR) spectroscopy, and a plasma frequency at 0.7 THz is observed, which agrees with the approximate theory.
Enhancement of Heat Transfer in Miniaturized Channels Using Ferrohydrodynamic Convection
Authors: Ganguly Ranjan , Sen Swarnendu , Puri Ishwar K.
Published: May 2008

Heat transfer in miniaturized channels and slots in electronic cooling applications is restricted by relatively low convection due to flow limitations. The flow is generally laminar and heat transfer in these small geometries is usually conduction limited. We have proposed the use of ferrofluids as coolants in the presence of a nonuniform external magnetic field to enhance the heat transfer. A magnetic ferrofluid consists of a stable colloidal dispersion of subdomain magnetic nanoparticles in a liquid carrier that remain suspended due to their thermal Brownian energy. Under a varying external magnetic field (B), a ferrofluid experiences a local volumetric body force (M.∇)B. The magnetization M of the ferrofluid is coupled with the fluid temperature through its density and magnetic susceptibility. In our simulations, a strong magnetic field is considered to be applied by placing an edge pole adjacent to one of the walls of a rectangular channel. The channel is assumed to carry a pressure-driven ferrofluid flow. The resulting flowfield is predicted by numerically solving the coupled mass, momentum, energy, and Maxwell’s equations. A parametric study is performed to identify the influence of the magnetic field strength on the temperature distribution and the resulting heat transfer. A comparison based on the local and average Nusselt numbers shows that there is a significant heat transfer augmentation due to the magnetic field.
Methods of Analysis of Tube Array Fluid Elastic Instability Data
Authors: Catton Ivan , Alquaddoomi Omar , Adinolfi Pierangelo
Published: May 2008

Fluid-elastic instability (FEI) is the cause of mechanical failures and expensive damage in tube bundle heat exchangers. The purpose of this experimental study is to develop a methodology to analyze the vibrations due to fluid-elastic instability in a tube array. The motions of a square array of 15 stainless steel vibrating tubes (␀ 25.4mm) in water cross-flow, suspended using stainless steel piano wire have been recorded with a CCD camera. The captured images are analyzed using two different methods. The individual motion and relative motion of the tubes are reported and can be used for computational model validation. The relative displacement of the tubes allows identification of the most potentially damaging patterns of tube bundle vibration. A critical reduced velocity may be determined by specification of an allowable limit on tube motion amplitude. Eventually, critical velocities for various tube array configurations and flow conditions can be measured and compared with existing criteria for heat exchanger design and operation.
Design, Modeling, and Fabrication of a Micro Corona Motor
Authors: Lee Sanghoon , Kim Daejong , Bryant Michael D. , Ling Frederick F.
Published: May 2008

Design, modeling, and fabrication of a micro corona motor was studied. Important design parameters including number of corona electrodes, air gap spacing, and electrode tilt angle were investigated using an electrostatic field simulator. From estimated charge distributions on the stator and rotor, force and torque were estimated, with the result that the spatial phase difference between the charge distributions on the stator and rotor determines the torque-speed relationship. For motor manufacture, X-ray lithography was adopted due to its special ability of precise and high aspect ratio characteristics. Built-on X-ray mask fabrication technique is briefly discussed. Finally, preliminary experiments were performed to verify working principle and characteristics.
Distortion Analysis of Memory-Less Nonlinear Sensors
Authors: Suranthiran Sugathevan , Jayasuriya Suhada
Published: May 2008

Distortion associated with memory-less nonlinear sensors is analyzed and several distortion compensation techniques are presented. Sensor nonlinearity is considered a defect in sensory systems because it introduces distortion into the system. Due to the fact that no efficient technique is available to deal with the issues related sensor nonlinearity, nonlinear primary sensors tend to be ignored. In this paper, we point out that there are certain advantages of using nonlinear sensor and nonlinear distortion caused by sensor nonlinearity may be completely compensated. A robust and efficient signal recovery procedure is derived to facilitate the design of nonlinear sensors. Not having an accurate sensor will result in errors and it is shown that the error can be minimized with a proper choice of a convergence parameter whereby stability of the developed algorithm is established. Simulation results are presented to validate the algorithms developed.
Assembly FMEA: A Simplified Method for Identifying Assembly Errors
Authors: Kmenta Steven , Cheldelin Brent , Ishii Kosuke
Published: May 2008

Manual assembly errors are a significant source of manufacturing defects. Therefore, an efficient method is needed to identify and alleviate potential assembly defects. Process Failure Modes and Effects Analysis (Process FMEA) is one technique used to anticipate, evaluate, and resolve potential manufacturing and assembly issues. However, performing FMEA is widely considered to be tedious and time-consuming, and not always worth the effort. In response, many researchers have attempted to automate FMEA using Artificial Intelligence (AI) to make it less arduous. Unfortunately, automated techniques are limited to systems with predictable behaviors (e.g., electronic circuits) and are rarely used on unpredictable processes such as manual assembly. “Assembly FMEA” is a novel technique developed specifically to identify manual assembly errors. Assembly defect levels are related to assembly complexity, which can be estimated using “Design for Assembly” (DFA) time penalties. Hence, Assembly FMEA uses a series of DFA-related questions to elicit potential assembly defects. The questions help to focus, standardize, and expedite the FMEA process. Assembly FMEA quickly identifies a large number of assembly errors with significantly less effort than conventional FMEA. This paper describes the Assembly FMEA procedure and illustrates its use on a conceptual design and on an existing product.
Fabrication of Piezoelectric Al0.3Ga0.7As Heterostructures
Authors: Kumar Parshant , Li Lihua , Calhoun L. C. , Boudreaux P. , DeVoe Don L.
Published: May 2008

A new process has been developed for the fabrication of AlGaAs-based MEMS which the inherent piezoelectric transduction present in this material to be used for sensing and actuation. The process combines molecular beam epitaxial growth of single-crystal Al0.3Ga0.7As multilayer, inductively coupled plasma reactive-ion etching (ICP-RIE), and highly selective wet etching of GaAs to produce released Al0.3Ga0.7As structures. The process has been validated through the fabrication of both cantilever and doubly clamped beam structures, and has wider use for applications where large electromechanical coupling strength and single-crystal heterostructure are desired.
Optical-Thermal Response and Dynamic Thermal Damage of Bio-Tissue During Laser Thermotherapy
Authors: Zhu G. M. , Liu W. , Zeng T. F. , Yang K.
Published: May 2008

Laser thermotherapy is a technique used for tumor treatment. It generates a local heating, causes thermal coagulation of living tissue and eliminates the tumor. Precise heating of tumor tissue with healthy minimum thermal injury to adjacent tissue is essential to thermotherapy. Understanding of heat transfer and optical-thermal interaction is important for control of temperature and design of thermotherapy. This study applies the Arrhenius damage model to describe the heat-induced change of optical properties. It calculates the distribution temperature, damage and optical-thermal response of bio-tissue during the laser treatment, and shows how these factors affect the effectiveness of laser thermotherapy. Similar research has been performed by Kim and coworkers [1996], Iizuka and coworkers [2000], and Whelan and coworkers [2000]. This study relaxes some conditions in previous investigations. It reveals the importance and the effect of size of the laser head.
Thermal Conductivity Model for Nearly Pure and Doped Thin Silicon Layers at High Temperatures
Authors: Asheghi M. , Goodson K. E.
Published: May 2008

Simulation of the temperature field in Silicon-on-insulator (SOI) transistors can benefit from better models and data for thermal conduction in pure and doped semiconducting materials. This work develops simple algebraic expressions to account for the reduction in thermal conductivity due to the size effect and to the presence of dopant impurities. The model applies to temperatures above 300 K and the results are compared with experimental data for pure and doped silicon layers.
Vibrational Analysis and Experimental Implementation of Rotational Indexing Mechanisms
Authors: Tsay Der-Min , Liu Chung-Han , Ho Sheng-Ying
Published: May 2008

To analyze residual vibrations of rotational, globoidal cam indexing mechanisms (GCIMs) with/without torque balancing cam (TBC) systems operated at high speeds, a simulation tool together with experimental verification has been established. In the analysis of the vibrational responses of such a rotational indexer, a 5-DOF model is built to account for the non-rigid behavior of the motor shaft, the coupling of the motor, the input shaft of the indexer, the TBC system, and the output shaft of the indexer with its load. Equations of motion of the model are formulated based on the bond graph method, and they are solved by the Runge-Kutta approach. To verify the feasibility of the model and its simulation results, a practical indexing device has been built and measured for its residual vibrations in a wide speed range.
Sensitivity Analysis of the Conical-Shaped Equivalent Model of a Bolted Joint
Authors: Manring Noah D.
Published: May 2008

In this paper, the conical-shaped equivalent model for a bolted joint is considered. In particular, the governing equations for this model are made non-dimensional for the purposes of conducting sensitivity analysis. From this work, a plot of the dimensionless spring-rate of the clamped material is generated for all reasonable designs for which the conicalshaped equivalent model applies. The sensitivity analysis is then used to discuss the relative importance of estimating the proper model and design parameters and a maximum percent of uncertainty in the spring-rate calculation is also presented. It is shown in this discussion that the calculations are quite sensitive to a proper estimation of the cone angle (a model parameter) and that uncertainty within this calculation can range from 5 to 20%.
Material Interaction Effects in the Reliability of High Density Interconnect (HDI) Boards
Authors: Mahalingam Saketh , Hegde Shashikant , Ramakrishna Gnyaneshwar , Pucha Raghuram V. , Sitaraman Suresh K.
Published: May 2008

This paper studies several base substrate materials and interlayer dielectric materials for High Density Interconnect (HDI) boards, addressing reliability issues such as warpage, dielectric cracking and microvia cracking. Design of simulation models with an optimization technique is developed to study material interaction effects on the HDI reliability. A plastic strain gradient-based computational algorithm is developed to study the thermo-mechanical deformation of fine-feature microvia structures.
Failure Behavior of Filament-Wound Carbon Fiber/Epoxy Composite Tubes Under Axial Compression
Authors: Sancaktar Erol , Schauber David A.
Published: May 2008

The behavior of filament-wound carbon fiber/epoxy composite tubes under axial compression is not widely understood. Although experiments have been conducted on short tubes, there is still not a fundamental understanding of the response of longer tubes in compressive loading. The primary objective of this study was to determine the general strengths and dominant modes of failure in such tubes, as well as to analyze the effects of three important input variables on this behavior: Tube length, Fiber orientation, and Displacement Rate (strain rate). In particular, attention was paid to the effects of the above variables on the following: Load versus displacement response, Compressive strength, Overall compressive displacement, Modes of failure, and Extent of failure. Using the process of computer-controlled filament winding, tubes of two different lengths, and four different lay-up configurations were manufactured. They were then tested under compressive load between two converging metal platens. These tests were conducted at two different crosshead speeds (speed, at which the platens close together) to observe the effect of strain rate on the behavior of these tubes.
Inverse Methods for Design and Control of Thermal Systems: Validation in a 2-D Visible Light Enclosure
Authors: Gamba Mirko , Pavy Trey , Howell John R.
Published: May 2008

Inverse methods have recently been introduced and applied to the design and control of thermal systems, particularly to systems where radiative transfer is the main heat transfer mode. The results of the steady state design of a representative radiative system using inverse methods have been experimentally validated on a modeled physical system. Few experiments have been developed to validate radiative transfer calculations even in simple systems. This is because it is difficult to separate other modes of energy transfer from radiative transfer, and, in transient systems, thermal inertia effects often mask the precise measurement of radiative effects. The present study is a continuation of the earlier validation work, performed to further study and eventually validate the inverse design and control methods by modeling and designing a simplified physical thermal system. A main focus of the present study is to exploit the similarities between thermal radiative systems lacking thermal inertia and visible light systems. Because of the absence of thermal capacitance, the response of a visible light system depends intrinsically on the state of the light source. The present study considers the inverse design of a newly developed experimental apparatus designed to simulate a low capacitance, two-dimensional radiative enclosure. The apparatus relies on the direct analogy between visible light and radiative heat transfer in a cold, low capacitance system where conduction and convection are suppressed. The system is designed so that both steady state and transient conditions can be achieved. The enclosure is equipped with individually controlled low-power lamps as the source of radiant flux, and these mimic radiant heaters in a real system. The design surface is instrumented with light detectors so that the intensity of the illumination on this surface can be quantified and eventually compared with the design goal. This paper illustrates the characteristics and capabilities of the experimental setup, along with the validity of inverse methods for steady state inverse design of the enclosure to achieve specified conditions on the design surface and sequent validation of the results on the experimental system.
On ALT and Field Reliability: Challenges and Solutions
Authors: Qian Zhengfang , Tomase Joe
Published: May 2008

This paper presents a critical overview of the current state-of-the-art of Accelerated Reliability Tests (ALTs) and field reliability. Investigations have been focused on a few critical issues, including test philosophy, test physics, test procedure, and test statistics. It has been identified that there is a huge gap between ALT and field reliability. Challenges and solutions include bridging gap between deterministic and statistical approaches, identifying failure modes/mechanisms and their interaction, making scientific judgement of complicated ALT procedures, determining sample size and targeted failure rate for test plans, building databases of ALT and field reliability for knowledge discovery, and developing powerful and integrated tools for virtual qualification and reliability prediction.
Methods for Predicting the Remaining Life of Electronic Assemblies With Carbon Nanotubes and an Optical Transduction Technique
Authors: Casey Paul , Ganesan Sanka , Pecht Michael , Anand Davinder K.
Published: May 2008

Life consumption monitoring is a method of quantifying the degradation of a system by monitoring the life cycle environment. With current research demonstrating the value of nanotubes as sensors, they may prove to be an inexpensive, compact, and reliable means to monitor not only system environments, but also physical signs of degradation. Life consumption monitoring of electronic assemblies can be cost-effectively done using optical strain measurement techniques. In this study, current output from an optical sensor can be used to interpret combined temperature and vibration histories. This may be accomplished by passing monofrequency light through optical fibers in a peripheral arrangement on a dummy chip. Any deviation from the null condition results in misalignment of the fibers, and hence reduction in intensity and current output. With appropriate failure data at different stress levels, it is possible to determine damage and estimate the remaining life. The key challenges are to determine whether such an optical health monitoring scheme can be sufficiently accurate and robust, and whether the results can be applied to a variety of packages at any location on a circuit assembly.
Cost Allocation in Cogeneration With Reduced-Exergy Method and Simplified Reduced-Exergy Method
Authors: Ye Xuemin
Published: May 2008

For several decades, although many kinds of allocation methods for heat-electricity cost allocation were proposed, there are remarkable differences computed with those methods due to each method having its relative merit and limitation in application. Based on the different roles of anergy and exergy in the heat supply process of cogeneration, two novel methods including the simplified reduced exergy method (SREM) and reduced exergy method (REM) are established by introducing the concept of reduced exergy and available anergy. Those methods consider not only the energy differences in quantity and quality, but also the roles of available anergy and exergy. Some practical conditions for typical units are computed and compared with present methods and existing methods. Calculations verify the feasibility of SREM and REM and indicated that those two methods are more rational, convenient and practical than existing methods in applications.
An Analytical Model of Phase Changing Chemically Reacting Mixture Flows
Authors: Dulikravich George S. , Colac¸o Marcelo J.
Published: May 2008

A complete and consistent mathematical model of multiphase flows allowing for chemical reactions and/or phase changes has been derived from basic continuum mechanics principles. Comparison of elements of this model with models published by other sources has been elaborated. A set of analytic relations linking mixture and fluid components has been derived. Conclusions about closure of the system have been drawn based on these derivations.
Optimization of Wall Electrodes for Electro-Hydrodynamic Control of Natural Convection Effects During Solidification
Authors: Colac¸o Marcelo J. , Dulikravich George S. , Martin Thomas J.
Published: May 2008

This paper presents a numerical procedure to reduce and possibly control the natural convection effects in a cavity filled with a molten material by applying an external electric field whose intensity and spatial distributions are obtained by the use of a hybrid optimizer. This conceptually new approach to manufacturing could be used in creation of layered and functionally graded materials and objects. In the case of steady electro-hydrodynamics (EHD), the flow-field of electrically charged particles in a solidifying melt is influenced by an externally applied electric field while the existence of any magnetic field is neglected. Solidification front shape, distribution of the charged particles in the accrued solid, and the amount of accrued solid phase in such processes can be influenced by an appropriate distribution and orientation of the electric field. The intensities of the electrodes along the boundaries of the cavity were described using B-splines. The inverse problem was then formulated to find the electric boundary conditions (the coefficients of the B-splines) in such a way that the gradients of temperature along the horizontal direction are minimized. For this task we used a hybrid optimization algorithm which incorporates several of the most popular optimization modules; the Davidon-Fletcher-Powell (DFP) gradient method, a genetic algorithm (GA), the Nelder-Mead (NM) simplex method, quasi-Newton algorithm of Pshenichny-Danilin (LM), differential evolution (DE), and sequential quadratic programming (SQP). The transient Navier-Stokes and Maxwell equations were discretized using the finite volume method in a generalized curvilinear non-orthogonal coordinate system. For the phase change problems, we used the enthalpy method.
CFD Comparison of Clearance Flow in a Rotor-Casing Assembly Using Asymmetric vs. Symmetric Lobe Rotors
Authors: Abu-Hijleh Bassam , Tu Jiyuan , Subic Aleksander , Li Huafeng , Ilie Katherine
Published: May 2008

The performance of a Rotor-Casing Assembly is influenced more by the internal air leakages than by any other thermo-fluid aspect of its behaviour. The pressure difference driving the air along a leakage path varies periodically and does so in a manner that may not be the same for every leakage path. So the distribution of leakage through the various leakage paths within the machine is important for the improvement of its performance. The total volume of air leakage and the distribution of the leakage among the different paths depend on the rotor-rotor and rotor-casing clearances as well as the geometry of the rotors’ lobes. Computational Fluid Dynamics (CFD) analysis was carried out using the FLUENT. Geometry definition, mesh generation, boundary and flow conditions, and solver parameters have all been investigated as the part of the numerical analysis. This analysis was conducted for static rotors at different positions. The results indicate that the size of the clearances as well as the geometry of the rotors’ lobes can have a significant effect on the total volume of the air leakage as well as the distribution of the leakage among the three main leakage paths. The results can be used to ascertain the proper levels of clearances to be used and the best rotor lobes geometry to be used for the practical reduction of air leakage.
An Experimental Study of Circulation Patterns in Natural Convection Using PIV
Authors: Akyuzlu K. M. , Nemani S. , Chakravarthy K.
Published: May 2008

The objective of this study is to investigate, experimentally, using Particle Image Velocimeter (PIV), the effect of different heat transfer boundary conditions on natural convection (specifically on flow patterns) inside a storage tank (a rectangular enclosure in this case with an aspect ratio of 0.5.) Purified water is used as the working fluid and it is seeded with 10 micron hollow glass sphere particles. The results of the first set of experiments are used to verify the flow patterns expected for the constant wall temperature boundary condition, the benchmark case. Similar experiments are conducted for the constant heat flux boundary condition. The Rayleigh number for all the cases studied lie between 106 and 107. The time averaged velocity field is determined using standard cross correlation techniques. Streamlines, and velocity contour plots are generated using this velocity field. Finally, the results of both cases are compared to identify the differences in circulation patterns and thermal stratification in the fluid.
Thermomechatronics of Power Electronics
Authors: Watts R. E. , Fedje K. , Brown E. R. , Shaw M. C.
Published: May 2008

The coupled effects of mechanical stress and thermal expansion on the electrical function of power electronic circuits are explored within a new analytical framework called thermomechatronics. The problem of interest is the progressive performance degradation of the power electronics owing to the growth of thermomechanically induced fatigue cracks within the die-attach interlayer between power devices and substrates. Building on previous efforts, the present analysis focuses on experimentally confirming the system-level degradation of a simple power electronics circuit subject to variations in junction temperature of the electronics that would result from variations in interlayer damage.
Application of Fuzzy Adaptive Networks in Manufacturing: Waviness Removal in Grinding of Wire-Sawn Silicon Wafers
Authors: Jiao Yue , Wu Jian , Lei Shuting , Pei Z. J. , Lee E. Stanley
Published: May 2008

Silicon is the primary semiconductor material used to fabricate microchips. The quality of microchips depends directly on the quality of the starting silicon wafers. One of the manufacturing problems in the manufacturing of silicon wafers is the presence of waviness on the surface as a result of wire-sawn slicing. To reduce this waviness, soft-pad grinding, a patented method, is used. Many factors influence the waviness reduction capacity during soft-pad grinding. The method of finite element analysis has been used to analyze the various factors. However, the grinding process is very complicated, the various factors are very vague and difficult to define. In this research, the recently developed fuzzy-neural adaptive network, which is ideally suited for the modeling of vague phenomenon, is used to model and to improve this waviness problem. To illustrate the usefulness of the approach, the process is modeled based on simulation data. The results, even though based on some very limited data, illustrate the influences of the various factors clearly.
Transport During Hot Embossing Micro-Manufacturing Studied via Stylus Profilometry and SEM
Authors: Rowland Harry D. , Charest Joseph L. , Wright Tanya L. , King William P.
Published: May 2008

This work investigates processing parameters affecting replicated feature size during hot embossing micro-manufacturing. Silicon micromachined masters were heated and pressed into polymer layers of different thermophysical properties. Imprinting with loads ranging from 20–35 MPa, load rates from 1–15 MPa/sec, load times from 90–115 sec, and imprint temperatures at, below, and above the polymer glass transition temperature (Tg) replicated features in polymer with varying degrees of conformity. Replicated features were measured by profilometry and inspected by scanning electron microscopy, revealing polymer feature heights ranging from 25–100% conformal matching of silicon master features and polymer feature widths closely matching the period of features on the silicon master. Statistical analysis determined replicated feature height was positively dependent on tip sharpness, master feature height, temperature, and load rate while negatively dependent on master feature width. Replicated feature width was found to depend positively on master feature height and width, temperature, load rate, and load time. Optimization of imprint parameters during hot embossing micro/nano-manufacturing can possibly lead to a high-throughput manufacturing process offering nanometer resolution.
The Welding Process Based on Intelligent Features in Car Body Development and Production
Authors: Mbang Sama , Haasis Siegmar
Published: May 2008

Today’s automotive market is highly competitive. As a result carmakers are being forced to offer newer, better, and cheaper cars in a shorter period of time in order to stay competitive in the global market. One way to achieve this goal is the introduction of platforms where each part is produced in a highly integrated and cost-efficient process. Now, during the design phase, the demands of cost-effective manufacturing must be taken into account. During the design phase, parts — in addition to the optimization of their function — have to be optimized with respect to their manufacturing process. Design, engineering, and production planning of a part are integrated to a high degree and often take place at the same time (concurrent engineering). Starting with the analysis of the joining process, this paper discusses requirements for an automated welding process based on feature technology. In this sense, flange creation and design, manufacturing, and welding requirements for automatic generation of spot weld are described. A process-oriented prototype is described, which has been integrated in CATIA V5, currently used as CAD-CAM system, and which fit the requirements of the designers and process planners.
Theoretical Analysis of Focusing and Intensity Mechanisms for a Spot Bonding Process Using Femtosecond Laser
Authors: Sarkar M. , Joshi S. P. , Shiakolas P. S. , Bulusu A.
Published: May 2008

In this paper we present the analysis of the focus and intensity mechanisms for a spot bonding process using a femtosecond pulsed laser with a Gaussian beam profile. The bonding process bonds two thin optically transparent materials by focusing the laser beam at their interface to form a joint with minimum damage to the surrounding material. The parameters that effect the bonding process are the focal length of the lens used, the beam intensity and waist, the angle of incidence of the laser on the material surface, and material characteristics such as thickness and refraction index. We performed numerical analysis for a number of focal lengths considering the above-mentioned factors. Plots showing the heat affected zone and energy loss to reflection through the thickness of the material as functions of focal length are presented. These plots help in determining the focal length to be used for surface bonding with femtosecond lasers.
Fuzzy Logic Regulator for the Performance Improvement and the Energy Consumption Reduction of an Industrial Chiller
Authors: Barelli Linda , Bidini Gianni , Arce Rube´n
Published: May 2008

Nowadays producers of household and industrial appliances need to optimize the efficiency of their products to diminish electric consumptions. In the case of refrigerators, the compressor is the component characterized by the highest electric absorption. The aim of the present study is to develop a compressor control algorithm for an industrial chiller to improve the performances and reduce the energy consumption. Results obtained by the authors in previous studies, encourage to the implementation of the fuzzy logic for regulator design. In particular a refrigerator for pastry shop was considered as the object of the study. A fuzzy controller was developed for the particular application by software simulation. The controller has greater performances of the PID and optimal linear regulators designed by the author for the same system. Subsequently a fuzzy adaptive procedure was defined to generalize the control algorithm, and allow the implementation of the controller to different refrigerators.
“Sweet Spot” or “Sweet Zone”? Modal Analysis of a Wooden Baseball Bat for Design Optimization
Authors: Jaramillo Paola , Manarky Kevin S. , Adrezin Ronald S. , Celmer Robert D. , Reinard John T. , Shetty Devdas
Published: May 2008

This paper describes modal testing of a wooden baseball bat with the purpose of finding the peak frequencies and vibration modes and their relation to the so-called “sweet spot”. Initial vibration testing was done by performing a tap test along a Louisville Slugger wooden baseball bat. The bat was suspended by elastic rubber bands to approximate free-free boundary conditions. The peak frequencies and bending mode shapes of the baseball bat were obtained. To verify the results, a modal analysis of the baseball bat was performed to simulate the structure’s dynamic behavior. The animated model validated the accuracy of the parameters obtained in the tap test. The bending mode shapes were also compared to the bending elastic mode shapes of a uniform, homogeneous beam undergoing no shear distortion. The exact solution of the beam equation of motion was solved. The mode shapes were plotted to compare them with the ones obtained from the baseball bat. This comparison indicated that the bat and the beam structures presented the same type of bending mode.
Calculation of the Unsteady Gas Flow Around a Projectile Moving Through a Gun Barrel
Authors: Ponyavin Valery , Akberov Roald , Chen Yitung , Hsieh Hsuan-Tsung , Pepper Darrell W.
Published: May 2008

The calculation of gas flow during the motion of a projectile in the gun barrel is a complicated computational task due of the presence of numerous factors, such as nonisothermicity, turbulence, changes in the shape of the computational domain with time, etc. In this study, an attempt to calculate the characteristics of gas flow around a projectile during the motion of the projectile in the gun barrel is undertaken. The flow is considered axisymmetrical, nonstationary, nonisothermal, compressible, and turbulent. For calculating the flow around the projectile, the finite volume method was employed. During the motion of the projectile, the flow pattern behind it changed from subsonic to supersonic. The results of the calculations are represented in figures depicting the flow at different moments of time. The figures show the fields of velocity, pressure and density, as well as the appearance of shock waves inside the gun barrel at subsonic and supersonic speeds.
Cooperative Range Estimation and Sensor Diagnostics for Vehicle Control
Authors: Howell Adam , Song Bongsob , Hedrick J. Karl
Published: May 2008

An integrated sensor fusion and fault diagnostic for the cooperative estimation of range and range rate in automated vehicles is presented in this paper. A virtual range sensor created by combining local sensor measurements and a wireless communication link between vehicles is fused with measurements from a Doppler radar and lidar. The sensor fusion is conducted by using a sequential variant of the nonparametric probabilistic data association filter with validation gating. Fault diagnostics are incorporated into the sensor fusion by thresholding the Mahalanobis distance computed in the validation stage. Performance of the integrated system is verified and demonstrated using experimental data obtained from low-speed vehicle following tests.
The Importance of Inherently Safer Processes to Site Security
Authors: Lindsey Pamelyn G. , Hendershot Dennis C.
Published: May 2008

Inherently safer processes (ISP) have become increasingly more important in recent years, specifically since the terrorist events of September 2001. New emphasis on site security and vulnerability has made it imperative for the chemical industry to view new and existing processes in a creative way. The tools available in designing an inherently safer process will allow industry to make these changes. “We ought, when possible, to be removing hazards rather than controlling them” (Kletz [1]). The concepts of inherent safety will be reviewed with specific examples with site security implications. For example the in-situ intermediate generation of methyl isocyanate (MIC) is a striking example of the concept of minimization and is of particular interest, since after the Bhopal incident, large quantities of MIC would be a target for terrorism. Other examples such as in-situ generation of phosgene use of aqueous ammonia instead of anhydrous, and elimination of chlorine cylinders in water treatment will be discussed with site security implications. The concepts used to create these inherently safer designs can then be integrated into existing process safety management programs to improve the overall safety of the chemical industry.
Fuzzy Non Linear PI Controller for High Performance
Authors: Aly Mohamed F. , Veldhuis Stephen C. , Hu Baogang
Published: May 2008

This paper presents a new technique for controlling different processes with high accuracy and fast response. The techniques is based on a fuzzy logic controller that was found to give better performance than a nonlinear PI compensator while maintaining the characteristics of a conventional PID controller. The approach uses two different control actions based on the feedback error obtained from the process. The error signal is used to determine the control output commands for the two different controller parameters (Kp and KI). This approach gives the system flexibility as well as a fast method for performing the control calculations. Fast response is achieved based on the use of a high proportional gain at the beginning of the process which adjusts to provide a rapid convergence time when reaching the reference position. One of the main advantages of this technique is that it provides a closed form solution describing the controller actions in terms of the tuning parameters. Another advantage is that while other approaches are based on a manual technique for tuning the controller parameters, this one uses optimization techniques. Through these techniques the optimal values of the controller parameters, required to achieve fast response, can be determined while maintaining high accuracy and disturbance rejection. Simulation results of the proposed technique are presented for processes varying from single to five degree of freedom system. The same under damped linear single input single output plant as used by Shahruz and Schwartz (1997) is presented to highlight the improved performance of this new technique.