bluuebunny/crossref_metadata_2025 huggingface dataset:
Joule Heating and Thermal Conductivity Determination of Nanoscale Metallic Thin Films and Interconnects
Authors: Gurrum Siva P. , King William P. , Joshi Yogendra K. , Ramakrishna Koneru
Published: April 2008

Evolution of high performance microprocessors has resulted in a steady decrease in on-chip feature sizes. Increasing requirements on maximum current density are expected to increase interconnect temperature drastically due to Joule heating. As interconnect dimensions approach the electron mean free path range, effective conductivity reduces due to size effects. Thermal characterization of sub-micron interconnects and thin films is thus highly important. This work investigates current crowding and the associated Joule heating near a constriction in a thin metallic film and proposes a novel technique to determine thermal conductivity of thin metallic films and interconnects in the sub-100 nm range. Scanning Joule Expansion Microscopy (SJEM) measures the thermal expansion of the structure whose thickness is comparable to the mean free path of electrons. Numerical solution of heat conduction equation in the frequency space is used to obtain a fit for effective thermal conductivity. A thermal conductivity of ~ 80.0 W/mK provides a best fit to the data. This is about one-third the bulk thermal conductivity of gold, which is 318 W/mK at room temperature. Using Wiedemann-Franz Law a thermal conductivity of 92.0 W/mK is obtained after measuring the electrical resistivity of the metal line. This is close to that obtained through numerical fit.
Reduction in Body Vibration and Spinal Impact With HACS Cushioning
Authors: Colvin David P. , McKinney Richard A.
Published: April 2008

High vibration and impact injuries continue to cause problems for military and civilian personnel in aircraft, trucks and armored vehicles. Crashes in helicopters and fixed wing aircraft as well as repetitive impacts in armored vehicles and trucks over rough terrain can pose serious problems and potential injuries for their occupants. Protective seat cushions can be engineered to absorb or mitigate a significant fraction of the mechanical energy before it is transmitted to the body. It has been shown, however, that conventional foam seat cushions can actually increase the potential for injury by allowing the body accelerations to overshoot. On the other hand, new and novel designs for cushioning materials can significantly reduce the potential for injuries from whole body vibration as well as spinal impact by extending and altering the duration of the high energy mechanical pulse. Based on unique computer models and subsequent CAD/CAM designs, prototype HACS seat cushions were fabricated from elastomers of three different durometers that incorporated precision, lateral choked airflow passages molded into the cushioning material. Subsequent testing with the NAVY Crew System Horizontal Accelerator at Patuxent River Naval Air Station, MD showed that the novel HACS seat cushion was 40% more effective than any other conventional aircraft seat cushion for the reduction of lumbar spinal load transmission to crash test dummies of all sizes during 23g impact tests. In more recent testing for the AAAV armored vehicle program, HACS seat cushioning has been shown to reduce whole body vibration by 36%.
Electric Field-Assisted Assembly of Type-I Collagen for Applications in Biomedical Micro-Systems
Authors: Miller Tiffany E. , Enikov Eniko T.
Published: April 2008

In the field of nanotechnology and applied engineering, an area that has received a great deal of attention is that of nanoassembly. The objective of this study was to demonstrate nanoassembly of type-I collagen on specified surfaces in response to an electric field. Two, otherwise identical, collagen solutions were prepared and adjusted to pHs of 5.5 and 8. The isoelectric fosusing point of collagen occurs at pH=6.7 which implies that the suspended collagen fibers in the aforementioned solutions possessed a net positive or negative charge, respectively. In each collagen solution, one volt was applied through a set of submerged electrodes for one minute. Atomic force microscopy was used to detect if and where assembly had occurred on the electrodes. The positively charged fibrils (pH=5.5) assembled on the negative electrode, but not on the positive electrode. The negatively charged fibrils (pH=8) assembled only on the positive electrode, but not on the negative electrode. In both cases, assembly occurred on the electrode of opposite charge of the suspended collagen fibrils, which was anticipated. The assembly of the positively charged fibrils (pH=5.5) on the cathode produced larger fibers than the fibers that were produced by the negatively charged fibrils (pH=8) on the anode. This indicated the more favorable environment for nanoassembly was the positively charged fibril solution (pH=5.5).
Optimization of Heat Pipe Thermal Transport Using Axially Graded Capillary Wick Structures
Authors: North Mark T.
Published: April 2008

One strategy for improving heat pipe heat transport performance will be discussed in detail. Using an axially graded wick, in which the capillary pore radius is varied as a function of axial position, the liquid pressure drop can be reduced allowing for increased heat transport. A one-dimensional analytical model is presented showing how the optimal continuously graded wick profile is developed for the case with constant vapor pressure and adverse (against gravity) orientation. General results are presented in terms of nondimensional parameters. For a particular case where the evaporator and condenser are each one-quarter of the length of the heat pipe, the optimal graded wick is capable of transporting over 5.6 times more power than an optimal uniform wick. In the worst case, the graded wick can transport over 3.3 times as much power as a uniform wick.
Tribological and Thermal Effects of Cutting Fluid Application in Machining With Coated and Grooved Cutting Tools
Authors: Jayal Anshu D. , Balaji A. K.
Published: April 2008

The use of Cutting Fluids (CFs) in machining operations is being increasingly questioned in recent years for environmental and economic reasons, leading to efforts in promoting dry, as well as minimal quantity of lubricant (MQL), machining. However, the tribological effectiveness and thermal aspects of CF action at modern cutting conditions, which not only involve relatively high cutting speeds but also advanced tool coatings and chip-breaking geometric features, need better understanding. This paper presents an experimental investigation into the effects of different CF application methods on various machining performance measures while cutting with commercially available flat-faced, as well as grooved, uncoated and coated cemented tungsten carbide tools. CF effects under dry, flood, and MQL conditions, were gauged through their influence on cutting forces, tool temperatures, tool-chip interfacial contact, and chip morphology during machining of AISI 1045 steel. The results show new trends on the individual cooling and lubricating effects of CF application methods, and the effects of their interactions with the tool coatings and the presence/absence of chip-breaking grooves.
On Improvement of Graduate Mechatronics Course
Authors: Du Winncy Y.
Published: April 2008

Colleges and Universities across the world have developed Mechatronics courses, programs, certificates, and even degrees in order to meet the increasing demands of Mechatronics products and engineers. These Mechatronics courses, mainly focusing on undergraduate level, consist of lecture presentations, well-designed laboratory experiments, and team projects. However, how to teach Mechatronics courses at graduate level remains to be an open area for discussion. The challenge is: what subjects should be addressed, at the graduate level, to closely reflect the latest Mechatronics technologies with much broad coverage and fast growing features, while distinguished from an undergraduate-level Mechatronics course. This paper discusses the approaches that the author used when teaching a graduate level Mechatronics course (ME285 Mechatronics Systems Engineering) at San Jose State University (SJSU). The course outline, laboratory experiments, and sample course projects are presented. The goal is to provide graduate students with a challenging, timely, hands-on, minds-on, and enjoyable experience in advanced Mechatronics. A suggestion of future topics for graduate Mechatronics education is also discussed.
Single and Two-Phase Heat Transfer in a Low-Density, 3-Dimensional Microchannel
Authors: Snyder Mark W. , Bryan James E.
Published: April 2008

A test section was developed to study 3-D microchannel surfaces made from copper strip. Selected results were presented for single and two-phase heat transfer through a low-density, 3-D micro channel using ethanol as the working fluid. Details of the single phase and two-phase heat transfer and fluid flow can be resolved from the experimental data. For 4 selected cases the total resistance was measured to be lower as the flow transitioned to two-phase flow for a given pressure drop. However, as the rate of two-phase heat transfer increased so did the pressure drop fluctuations.
Effect of Inlet Fluid Temperature on the Buoyancy Induced Flow in Circular Tube Inserted With Twisted Strip
Authors: Thombre S. B. , Prayagi S. V. , Deshpande N. V.
Published: April 2008

The present work deals with experimental studies on heat transfer characteristic for buoyancy induced flow through inclined tubes inserted with twisted strips. The parameters varied during the experimetation are; tube inclination, heat supply twist pitch and fluid inlet temperature. It was found that the percentage enhancement in heat transfer coefficient decreases with increase in pitch and tube inclination. The flow rate is found to decrease with decrease in the pitch and increase in the tube inclination. It was also observed that the heat transfer coefficient and flow rate decreases with the increase in the inlet fluid temperature. This may be due to reduction in Rayleigh number caused because of higher heat loss at the tube surface.
Numerical Analysis of Opposing Mixed Convection in Air in a Vertical Channel With a Moving Plate
Authors: Andreozzi Assunta , Bianco Nicola , Naso Vincenzo , Manca Oronzio
Published: April 2008

In this study a numerical investigation of mixed convection in air due to the interaction between a buoyancy flow and a moving plate induced flow in a vertical channel is carried out. The moving plate has a constant velocity and moves in the opposite direction with respect to the buoyancy force. The channel principal walls are heated at uniform heat flux. The numerical analysis is obtained by means of the commercial code Fluent. The effects of the channel spacing, heat transfer and moving plate velocity are investigated and results in terms of the channel wall and moving plate temperatures and Nusselt numbers are given. The wall temperature profiles allow to observe different behaviors of the flow motion inside the channel, a buoyancy flow, a forced flow and a transition flow related to the velocity of moving plate. The transition velocity increases as the heat flux and the channel gap increase. Dimensionless heat transfer results, Nu/Re0.68 as a function of Richardson number, Ri, present a good agreement with two correlations obtained for the buoyancy dominant flow, at Ri > 10, and forced dominant flow, at Ri < 10−3.
Development and Application of a Dynamic Decomposition Strategy for the Optimal Synthesis/Design and Operational/Control of a SOFC Based APU Under Transient Conditions
Authors: Rancruel Diego , von Spakovsky Michael
Published: April 2008

A typical approach to the synthesis/design optimization of energy systems is to only use steady state operation and high efficiency (or low total life cycle cost) at full load as the basis for the synthesis/design. Transient operation is left as a secondary task to be solved by system and control engineers once the synthesis/design is fixed. However, transient regimes may happen quite often and the system response to them is a critical factor in determining the system feasibility. Therefore, it is important to consider the system dynamics in the creative process of developing the system. A dynamic optimization approach developed by the authors and called Dynamic Iterative Local-Global Optimization (DILGO) is applied to the dynamic synthesis/design and operational/control optimization of a solid oxide fuel cell based auxiliary power unit. The approach is based on a decomposed optimization of individual units (components and sub-systems), which simultaneously takes into account the interactions between all the units which make up the overall system. The approach was developed to support and enhance current engineering synthesis/design practices, producing improvements in the initial synthesis/design state of the system and its components at all stages of the process and allowing for any degree of detail (from the simple to the complex) at the unit (component or sub-system) level. The total system is decomposed into three sub-systems: stack sub-system (SS), fuel processing sub-system (FPS), and the work and air recovery sub-system (WRAS). Mixed discrete, continuous, and dynamic operational decision variables are considered. Detailed thermodynamic, kinetic, geometric, physical, and cost models are developed for the dynamic system using advanced state-of-the-art tools. DILGO is then applied to the dynamic synthesis/design and operational/control optimization of the system using total life cycle costs as the objective function. Results for this system and component optimization are presented and discussed.
An Efficient Volumetric-Error Measurement Method for Five-Axis Machine Tools
Authors: Wang Shih-Ming , Yu Han-Jen , Liao Hung-Wei
Published: April 2008

Accurate measurement of volumetric errors plays an important role for error compensation for multi-axis machines. The error measurements for volumetric errors of five-axis machines are usually very complex and costly than that for three-axis machines. In this study, a direct and simple measurement method using telescoping ball-bar system for volumetric errors for different types of five-axis machines was developed. The method using two-step measurement methodology and incorporating with derived error models, can quickly determine the five degrees-of-freedom (DOF) volumetric errors of five-axis machine tools. Comparing to most of the current used measurement methods, the proposed method provides the advantages of low cost, high efficiency, easy setup, and high accuracy.
MADYMO Simulations of Occupant and Vehicle Kinematics in Offset and Oblique Barrier Tests
Authors: Shea Rex T. , Kral Jiri
Published: April 2008

Oblique and offset impacts occur more frequently than full frontal impacts and the resulting occupant and vehicle kinematics are more complicated. Simulations of these test modes are more involved with added vehicle degrees of freedom. Additional occupant interactions with the vehicle interior need to be considered so that the occupant kinematics can be correlated more accurately. In order to capture the vehicle motion in an offset or oblique impact, a prescribed motion approach is preferred where the vehicle is given a three-dimensional motion with six degrees of freedom. With a planar motion assumption, the dominant angular motion about the vertical direction can be derived from linear accelerations measured at two locations where the vehicle deformation is a minimum. In a previous study the angular kinematics was given to a coordinate origin located on the vehicle centerline and longitudinally near the rear rocker. The instantaneous center of rotation was assumed to be fixed at this point during the event. This is referred to as Method I in this paper. A new approach, referred to as Method II, applied translational displacement to three bodies, which carried the passenger compartment through stiff spring elements. The displacements were integrated from measured accelerations, eliminating the uncertainty of a shifting center of rotation. Both methods assumed the vehicle frame between the front and rear rockers as a rigid body. The IP and steering column intrusions and floor deformations were neglected. The results from both methods were correlated to a pair of 40 kph 30 degree angle impact tests and an IIHS ODB test. Method II showed a slightly better timing correlation for the angle tests and the IIHS ODB test. However, both methods didn’t predict the lateral head contact for the driver in the left angle test and the passenger in the right angle test. More interior details have to be included in the model to capture the lateral motion of the occupants. The prescribed motion method is a more general approach than the commonly used inverse kinematics method, and can be applied to full frontal impact as well. The versatility of the method provides a basis for a modular approach in occupant simulations.
Aerodynamic Properties of Avian Flight as a Function of Wing Shape
Authors: March Andrew I. , Bradley Charles W. , Garcia Ephraim
Published: April 2008

Presently, all man-made aircraft are optimized for one specific flight regime. Commercial aircraft fly at a specific cruising altitude at which they are most efficient, and military aircraft, which require excellent performance in many flight regimes are designed to be ‘good’ at all of them. A new concept in aviation, morphing aircraft, or aircraft that can fully change their shape, will allow for optimization at nearly any flight regime. This concept has been millennia in the making, well before mankind. Looking to various bird species, tails and wings can completely change shape to optimize their morphology for a given flight regime. Raptors, especially, have mastered the air in that they must out compete and overcome other birds while hunting. For soaring, these birds spread their wings fully to maximize their lift to drag ratio and maintain a low energy, long endurance flight. To maximize speed in a dive they will bring their wings close to their bodies to minimize drag. This study seeks to quantify the aerodynamic properties of the wing. From bird wings the aerodynamic properties of shape changing elastic structures can be understood. The coefficient of lift versus angle of attack plot of a bird wing is not like that of a typical airfoil, it has no distinct point where the wing stalls, instead the bird wing will twist into the flow. Additionally, the induced drag of an avian wing is significantly less than the theoretical induced drag on a wing predicted by the aspect ratio. A flow visualization around the slotted wingtips of a bird reveals smooth streaklines near the primary feathers. These feathers are canted downward and accordingly generate lift in the thrust direction of the wing, which acts to reduce the induced drag on the wing.
A Novel Anisotropic Conductive Adhesive for Lead-Free Surface Mount Electronics Packaging
Authors: Ramkumar S. Manian , Srihari Krishnaswami
Published: April 2008

The electronics industry, in recent years, has been focusing primarily on product miniaturization and lead-free assembly. The need for product miniaturization is due to the continuous demand for portable electronic products that are multifunctional, yet smaller, faster, cheaper, and lighter. This is forcing the industry to design and assemble products with miniature passive and active devices. These devices typically have fine pitch footprints that provide a very small surface area for attachment. The solder attach technique relies primarily on the formation of intermetallics between the mating metallic surfaces. With a reduction in the surface area of the pads, the ratio of intermetallic to solder is very high once the solder joint is formed. This could result in unreliable solder joints, due to the brittle nature of intermetallics. In addition, the need to eliminate lead-based materials as a means of interconnection has renewed the industry’s interest in exploring other means of assembling surface mount devices reliably. This paper discusses the performance characteristics and preliminary research findings pertaining to a novel Anisotropic Conductive Adhesive (ACA) for electronics packaging applications, utilizing the Z Bond™ technology from Nexaura Systems, LLC. Typically, ACAs require the application of pressure during the curing process, to establish the electrical connection. The novel ACA uses a magnetic field to align the particles in the Z-axis direction and eliminates the need for pressure during curing. The formation of conductive columns within the polymer matrix provides a very high insulation resistance between adjacent conductors. The novel ACA also enables mass curing of the adhesive, eliminating the need for sequential assembly. The novel ACA’s I-V characteristics and performance under thermal and temperature-humidity aging are discussed in detail.
A Repeatable and Reliable Rework Process for Lead-Free Fine Pitch BGA’s
Authors: Manjunath Deepak , Iyer Satyanarayan , Eckel Shawn , Damodaran Purushothaman , Srihari Krishnaswami
Published: April 2008

Fine pitch leadless components, such as Ball Grid Arrays (BGAs) and Chip-Scale Packages (CSPs), are increasingly used in modern day circuitry to aid miniaturization. Assembling these surface mount components using lead-free solder pastes has been a subject of interest for the past several years. Reworking a BGA is complicated as the solder joints are hidden underneath the component. The process window available for the rework process is very narrow and there are number of other critical factors, which complicate and affect the repeatability of the rework process. Consequently, the primary objective of this research endeavor is to develop a reliable and a repeatable process to rework lead-free fine pitch BGAs. The process steps to rework a BGA are component removal, site redressing, solder paste/flux deposition, component replacement and reflow. This experimental study evaluates a number of alternatives for several rework process steps during the course of developing a reliable and repeatable rework process. Two alternatives for site redressing namely, (i) copper wick with soldering iron, and (ii) vacuum de-soldering methods are evaluated. Similarly the application of solder paste versus gel flux is compared. A localized reflow method for replacing the component at the SRT machine is developed and it is compared with forced convection in reflow oven. The pros and cons of using the two reflow methods and the effect of multiple reflows on solder joint reliability is discussed in the paper. A reliability study was conducted on the samples and the results are presented to compare the various alternatives.
Modeling and Experimentation of Viscous Damping for LIGA Structures
Authors: Yagci Baris , Naik Tikeswar , Lu Wei-Yang
Published: April 2008

LIGA (from German, LIthographie, Galvanoformung und Abformung) is one of the most viable manufacturing techniques for creating precise micro-mechanical components. Due to their monolithic construction, LIGA structures lack the most important contributor to energy dissipation; the joints. In shock and vibration environments, the low damping capacity can cause functional and structural failures. As a means of increasing the energy dissipation of LIGA structures, this paper experimentally investigates coupled fluid-structural dynamics of LIGA structures when submersed into fluids. The experiments are conducted by base-exciting a rectangular cross-section cantilever LIGA beam with a shaker, and measuring the response through a laser Doppler vibrometer. The paper also evaluates simple fluid dynamics models from the literature for their effectiveness in capturing the experimentally-observed behavior.
Flow Measurements in a First Stage Nozzle Cascade Having Leakage and Assembly Features: Effects of Endwall Steps and Leakage on Aerodynamic Losses
Authors: Piggush J. D. , Simon T. W.
Published: April 2008

This work supports new gas turbine designs for improved performance by evaluating endwall leakage and assembly features in a cascade that is representative of a first stage stator passage. The present paper documents component misalignment and leakage flow effects on the aerodynamic losses within a passage having one contoured and one straight endwall. Steps on the endwall and leakage flows through the endwall can lead to thicker endwall boundary layers, stronger secondary flows and possibly additional vortex structures in the passage. The paper compares losses with steps of various geometries and leakage of various flow rates to assess their importance on aerodynamic losses in this contoured passage. In particular, features associated with the combustor-to-turbine transition piece and the slash-face gap, a gap between two vane segments on the vane platform, are addressed.
Laser-Assisted Nanoscale Material Processing (Invited)
Authors: Lu Y. F.
Published: April 2008

Laser material processing demonstrated its significance in many areas such as microelectronics, data storage, photonics and nanotechnology, since versatile laser sources provide flexible and unique energy source for precise control of material processing. With current laser technology, a short wavelength down to X-ray range and a short pulse duration down to femtosecond range can be achieved. The extreme conditions created by laser irradiation have provided strong impact on material research. To achieve nanoscale laser material machining and processing, we need to overcome the diffraction limit of the laser wavelengths. Recently, different approaches have been explored to overcome the diffraction limit and to achieve feature sizes down to 10 nm order, way beyond the diffraction limits. This paper will provide an overview in the areas of laser-based nanoscale machining and processing, including the author’s own research experience on laser-assisted scanning probe microscope, superfocusing by optical resonance in spherical particles, laser nanoimprinting, laser synthesis of quantum dots, laser annealing of ultrashow pn junctions, nanometer-order film thickness detection using rotational Raman spectroscopy, and laser cleaning of nanoparticles.
Thermal Design and Optimization of an IGBT Power Electronic Module
Authors: Mital Manu , Scott Elaine P.
Published: April 2008

This paper presents thermal design optimization of an insulated gate bipolar transistor (IGBT) integrated power electronic module (IPEM). A commercially available finite element package was used to create a 3D geometric layout of the IGBT module. Thermal simulations were performed under different forced air convection conditions, and for both single and double-sided cooling, to study the effects on the hot-spots and maximum temperature rise of the module. The design optimization for the module was performed by varying parameters (choice of materials and layer thicknesses) and studying their effect on the thermal performance of the module. The results of these studies were several improved designs for the module.
Measurement of Radiation Transfer Through Nano-Apertures Using Near-Field Scanning Optical Microscopy
Authors: Jin Eric X. , Xu Xianfan
Published: April 2008

Ridge apertures in various shapes have attracted extensive studies which showed their potential capabilities in realizing both enhanced transmission and nanoscale optical resolution, therefore, enabling ultrahigh density near-field optical recording. In this work, the optical near field distributions of an H-shaped ridge aperture and comparable regular apertures made in aluminum film are experimentally investigated using a home-made near-field scanning optical microscope. With a sub-100 nm aperture probe, the full-width half-magnitude (FWHM) near-field spot of the H aperture is measured as 106 nm by 80 nm, comparable to the gap size but substantially smaller than that obtained from a square aperture with the same area. The elongated near-field light spot in the direction across the ridges is due to the scattering of the transmitted light on the edges based on results of numerical calculations.
On the Design Parameters of the Delamination in Stacked Plastic Package
Authors: Yang C. , Zhao J. F. , Wang J. F.
Published: April 2008

Stacked Chip Scale Package (SCSP) becomes popular recently because it increases package density and offers flexible component design at low cost. However, package reliability issues need to be carefully addressed because of the complex package geometry and structure. As one of the common failure modes, delamination is often encountered due to pre-existing defect and external loadings, such as thermal stress caused by different CTE of materials, hydro-swelling stress and vapor pressure caused by moisture desorption during reflow soldering. In SCSP, delamination often occurs along the interface of two dissimilar materials, primarily due to the weak interface bonding. Therefore, proper material selection and optimization of package structure are critical to reduce the risk of delamination in the design stage. Material selection is mainly based on the measurement of the interfacial fracture toughness or some quick-turn test to determine interface strength. Usually, the interfaces between die attach/die, die attach/substrate, mold/substrate and mold/die are evaluated. On the other hand, structural optimization is mainly carried out through numerical modeling to investigate the delamination sensitivity to stress, flaw size and position. Design parameters, such as die overhang, die thickness and bonding layer thickness are considered to have impact on the local stress distribution, which can lead to different delamination performance. Fracture mechanics based modeling, which can deal with pre-exist cracks, is adopted for this study. A typical multi-die stack chip scale package (CSP) is modeled by finite element to study the relationship between design parameters (die overhang, die thickness and bonding layer thickness) and stress intensity factor (SIF) for a delamination along die to mold compound interface. The effect of bonding layer (paste or adhesive film) CTE is also included in the present research as practically it can be changed by choosing different DA (die attach) materials. Optimized design parameters and considerations in package design can be proposed based on the modeling results.
The Effects of Combination of EGR, Injection Retard and Injection Pressure on Emissions and Performance of Diesel Engine Fuelled With Jatropha Oil Methyl Ester
Authors: Suryawanshi J. G. , Deshpande N. V.
Published: April 2008

Retarded injection is used to control NOx emissions. Exhaust Gas Recirculation (EGR) is also an effective means of reducing NOx emissions from compression ignition engines. Higher fuel injection pressure may improve the combustion. EGR can be combined advantageously with other emission reducing measure such as retarded injection timing and performance improvement measures such as higher fuel injection pressure to have a good effect. The methyl ester of jatropha oil, known as biodiesel, is receiving increasing attention as an alternative fuel for diesel engines. Biodiesel is a non-toxic, biodegradable and renewable fuel with the potential to reduce engine exhaust emissions. The jatropha oil methyl ester was obtained through transesterification process. Various properties of the biodiesel thus developed were evaluated and compared in relation to that of conventional diesel oil. In the present investigation neat jatropha oil methyl ester (JME) as well as the blends of varying proportions of JME and diesel were used to run a CI engine with standard conditions (No EGR, No Injection Retard and 20 MPa Fuel Injection Pressure) and with combination of 20 % EGR, 4° retarded injection timing and 30 MPa fuel injection pressure. The addition of jatropha oil methyl ester (JME) to diesel fuel has significantly reduced HC, CO and smoke emissions but it increases the NOx emissions slightly with standard conditions. The NOx emission was drastically decreased with modified conditions. Further the smoke and unburned hydrocarbon emissions were decreased with modified conditions as compared to standard conditions. The brake thermal efficiency was improved with modified conditions at various loads. Exhaust gas temperatures were similar. The maximum cylinder gas pressure and heat release rate were lowered.
Robust Electric Load Sensing Applied to an Open Circuit Axial Piston Pump
Authors: Hansen Michael Rygaard , Andersen Torben Ole , Pedersen Henrik Clemmensen
Published: April 2008

Electronic load sensing (ELS) systems have long been expected to start replacing traditional (hydro-mechanical) load sensing (LS) systems, which today are the standard on most medium and high-end mobile hydraulic applications. The reason for this being the potentials that ELS brings relative to traditional LS-systems, in terms of better control and system utilization possibilities, combined with the increased acceptance and use of electronic sensors in mobile hydraulic machinery. The current work is to evaluate the suitability of an ELS concept applied to a Sauer Danfoss Series 45 H-frame open circuit axial piston pump. Emphasis is on performance robustness with respect to both variations in internal physical parameters of the pump as well as the type of application dependent load which the pump is expected to drive. The pressure control is established by means of cascade control utilizing four control loops with the outer being the pump pressure and then, in succession, the swash plate rotation, the spool position and the voice coil current. The proposed controller has been implemented experimentally and verified.
A Simulation Study of Vehicle Curve Speed Control System
Authors: Lee Yong H. , Deng Weiwen
Published: April 2008

In this paper, a speed control system for vehicle approaching, traveling, and coming out of a curve is investigated using simulation. In order to assist driver in ahcieving safer and more comfortable curve following performance, vehicle speed is controlled using the preview data of the road ahead, which is obtained from the GPS and Map or vision system. The control system is comprised of a method for determining a desired curve speed profile to help achieve the best cornering performance for an up-coming curve and regulating vehicle speed toward the desired speed. The lateral dynamics of vehicle is used for computing the desired speed for a curve. From the current vehicle speed and the desired speed profile, the acceleration profile for a curve ahead of the vehicle is computed. Then, the acceleration command is generated to slow the vehicle so the driver can achieve the optimal curve following. From the simulation studies, it is concluded that the system can potentially improve driver cornering performance.
Thermal Fatigue Life Prediction Model of CCGA Tin-Lead and Lead-Free Interconnects
Authors: Wong T. E. , Chu C.
Published: April 2008

A thermal fatigue life prediction model of a ceramic column grid array (CCGA) solder joint assembly has been developed when the 90Pb/10Sn solder columns of the CCGA package are soldered onto the printed circuit board with either tin-lead or lead-free solder paste. This model was evolved from an empirically derived formula by correlating the solder nonelastic strain energy density increment to the fatigue life test data. To develop the solder joint fatigue life prediction model, a nonlinear finite element analysis (FEA) was conducted using the ABAQUS computer code. A thermal fatigue life prediction model was then established. The test results, obtained from various sources in which tin-lead and lead-free solder pastes on PCB were used, combined with the FEA derived nonelastic strain energy density per temperature cycle, ΔW, were used to calibrate the proposed life prediction model. In the analysis, 3-D finite element global- and sub-modeling techniques were used to determine the ΔW of the CCGA solder joints when subjected to temperature cycling. The analysis results show that: 1) solder joint would typically fail across solder column instead of along solder pad interfaces; and 2) higher nonelastic strain energy densities of solder occur at the solder columns at the package corners and these solder joints would fail first. These analysis predictions are consistent with the test observations. In the model calibration process, the 625- and 1657-pin CCGA test results, which were cycled between 20°C/90°C, 0°C/100°C, -55°C/110°C, or -55°C/125°C, were reasonably well correlated to the predicted values of ΔW. Therefore, the developed life prediction model could be used and is recommended to serve as an effective tool to determine the integrity of the CCGA solder joints during temperature cycling. In addition, the following future work is recommended: 1) selecting more study cases with various solder joint configurations, package sizes, environmental profiles, etc. to further calibrate this life prediction model; 2) using this model to conduct parametric studies to identify critical factors impacting solder joint fatigue life and then seek an optimum design; and 3) developing a simplified method instead of the FEA approach to make preliminary thermal fatigue life estimates of the CCGA solder joints.
Probabilistic Analysis for the Mechanical Properties of Cross-Ply Fiber-Reinforced Composite Laminate
Authors: Chuang Shui-Nan
Published: April 2008

A probabilistic micromechanics model had been developed for the unidirectional fiber-reinforced composite material design screening. In which, we used the predicted mechanical properties of IM-7 carbon fiber from the existing IM-7/5250-4 composite material system together with the observed 977-3 matrix mechanical properties to predict the probability density functions for the mechanical properties of IM-7/977-3 unidirectional composite. To include the material design in the structural design process, we had extended the probabilistic analysis to predict the probability density functions for the off-axis mechanical properties. The angle-ply and cross-ply laminates have been used extensively in aerospace structural designs. It is logical to extend the probabilistic analysis to predict the probability density functions for the mechanical properties of the laminated composite. We had provided the probabilistic analysis for a symmetric regular angle-ply laminate of IM-7/5250-4 composite laminate. In this report, we will focus on the probabilistic analysis of symmetric and anti-symmetric regular cross-ply laminates of IM-7/5250-4 fiber-reinforced composite with odd-number plies parallel to and even-number plies perpendicular to the laminate principal axes. These probabilistic micromechanics models provide a design-screening tool to help material producers to eliminate the unnecessary time-consuming and costly material fabrications and to reduce the numbers of testing to a minimum but enough to verify the model prediction. They also provide a structural analysis tool to help the structural designer to manage the structural and material uncertainties during the structural design process. And consequently, it provides a means to accelerate the insertion of materials into AF productions.
Wireless Control of Parabolic Shells Using Photostrictive Actuators
Authors: Shih Hui-Ru , Tzou Horn-Sen
Published: April 2008

Photostrictive actuator, which can turn light energy into mechanical energy, is a new promising photoactuation technique for non-contact wireless active control of flexible structures. Optical mirrors, communication antennas, solar/optical reflectors, nozzles, rocket fairings, etc. often have the shape of parabolic shells or shells of revolution, due to their required focusing, aiming, or reflecting performance. In this paper, the active control of flexible parabolic shells using discrete photostrictive actuators is investigated. Parabolic shell of revolution is considered one of the most difficult geometry among all shell and non-shell structures. Because of this, an approximate way to estimate the dynamic behavior and light-induced control forces of a photostrictive coupled parabolic shell is presented. Based on the approximate model, the effects of actuator locations as well as membrane and bending components on the control action are analyzed. The results obtained indicate that the control forces are mode and location dependent. It is also shown by analysis that the membrane control action is much more significant than the bending control action. The validation of the approximate model is done by comparing the light-induced control forces of the photostrictive coupled shells obtained by the approximate equivalent spherical shell model and those obtained by the parabolic shell model.
The “Virtual Power Plant” Concept: Coordinating the Management of Fuel Cell Clusters
Authors: Carraretto Cristian
Published: April 2008

The fuel cells are interesting energy conversion systems for combined heat and power applications. In particular the proton exchange membrane (PEM) and the solid oxide fuel cells are promising alternatives to other distributed solutions for residential uses. This paper analyzes the feasibility of a fuel cell network in a residential area. A set of fuel cells is installed in different buildings of an urban district, to supply thermal and electric energy to the users. When not required in situ, the electric production of the fuel cells is sold to other neighboring users or traded through the grid. By coordinating the production of the various fuel cells, a sort of "virtual" power plant is hence obtained. Different PEM fuel cells are used here to build the network, extended both to commercial and residential buildings. To investigate the profitability of this solution, a non-linear constrained optimization problem is built. The problem consists in optimizing the power output of each fuel cell over a selected period of time, in order to meet the users' demand and maximize the revenues associated with the trade of the residual production. Preliminary results are discussed for different solutions (fuel cell size, user characteristics, etc.) considering the seasonality of the electric and thermal demands.
Smart Impact Management Devices: Experimental Validation of Crush Response of Rapidly Expanded Aluminum Honeycomb
Authors: Browne Alan L. , Johnson Nancy L. , Webb Scott R.
Published: April 2008

A major limitation of current dedicated impact energy management structures and passive devices used in the transportation industry is that their starting volume is their maximum volume, i.e. they dissipate energy by crushing or stroking from a larger to a smaller volume. Since they occupy their maximum volumes in their uncrushed-as-installed state they occupy space that is then only functional in an impact and is otherwise wasted. This limitation has led to the proposal of a class of "smart" impact energy management devices, based on unexpanded aluminum honeycomb (HOBE), that initially occupy a small volume and based on sensor input are rapidly expanded to a much larger crushable volume (nominally 75 times greater) just prior to or in response to an impact. Energy management devices based on this technology, should this technology successfully pass through the many steps needed to prove its viability, would thus allow empty space to be left adjacent to them for operational clearances, serviceability and repair functions, etc. which spaces would yet be fully utilized, due to the expansion of the device, for impact energy management. This paper documents the second portion of an experimental exploration of the viability of this technology. The specific goal of the here-in documented portion of the test program was the demonstration that the crush response of the rapidly expanded honeycomb is comparable to that of the standard pre-expanded commercial product.
A Hands-On Approach in Teaching Dynamic Systems Modeling and Control
Authors: Barakat Nael , Jack Hugh
Published: April 2008

Most engineering products nowadays are multi-part integrated systems that are produced by teams of engineers. These systems are characterized by their complexity and diversity of components that range between being fully mechanical to being fully electrical components. A vital aspect in successfully building and running of these systems is the proper modeling and control of their dynamics. As mechanical engineering students graduate and face this reality, a hands-on preparation to deal with similar systems during college experience becomes very rewarding. The important elements of applying knowledge in dynamic systems modeling and control are practiced during the laboratory session in college. At the Grand Valley State University (GVSU) School of Engineering (SOE) the integration of electrical, mechanical and software systems is instructed and practiced in a required course (EGR 345) entitled "Dynamic systems Modeling and Control." This course includes a theoretical part where principles of system dynamics, system components, and system control are emphasized. The course capitalizes on students' previous knowledge of the simple isolated systems and modifies their strategies and approach to look and treat engineering systems as complete integrated entities. In addition, the course includes a significant lab component and a major project through which the student gains vital hands-on experience. In this paper, the philosophy and major components of the course are discussed. The focus is on presenting a sequence of lab experiments that serve the application of principles of dynamic systems modeling and control, as well as the final project. These experiments are characterized by its comprehensiveness and cost effectiveness. Moreover, an innovative method of making the lab equipment available to the students, and mostly owned by them, will also be summarized. As this approach minimizes the financial burden of the lab equipment, it also gives the students an element of ownership and comfort dealing with equipment they own and use. As a matter of fact, it ultimately leads to the utilization of these pieces of equipment in an innovative way to produce an engineering electromechanical system that will perform the tasks required by their final project description. A discussion on the pros and cons in the outcomes of this approach and some modification plans for the next course offering will be provided at the end of the paper.
Designing Aspects of Cylindrical Transmission
Authors: Bara Mircea
Published: April 2008

The cylindrical transmission with balls is a new type of mechanical transmission, that allows movement transmission between two coaxial shafts [1]. In the first part of this paper presents the geometric and kinematics study of the elements of cylindrical -sinusoidal transmissions with balls, determining in this way the transmission ratios. In the second part of this paper presents the geometric and kinematics study of the elements of differential cylindrical transmission with balls, determining in this way the transmission ratios. An advantage of this transmission, as compared to other mechanical transmissions, is given by the possibility to obtain more transmission ratios. In case all cylinders of simple cylindrical transmission are moving elements a differential transmission it obtained. Another advantage is given by the possibility of obtaining complex transmissions by series and/or parallel arrangement of cylindrical transmission simple units.