bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration and Stability of Cylindrical Shells Containing Flowing Fluid
Authors: Zolotarev Igor
Published: June 2008

Natural frequencies and the thresholds for loosing the stability of thin-walled cylindrical shell conveying by flowing fluid are theoretically studied. Potential flow theory for fluid and 3D theory for thin shells are used. The shells of finite length are considered for the different case of boundary conditions at the edges of the shell, and their influence on the critical flow velocities for flutter are demonstrated. The fundamental importance of boundary conditions considered for fixing the edges of the cylindrical shell of finite length is shown. When the clamped - simply supported boundary conditions are assumed, the critical flow velocity for flutter is very low, even if the energy dissipation due to the fluid viscosity was taken into account.
Crashworthiness Challenges in Steel-to-Aluminum Front End Design
Authors: Baccouche Mohamed R. , Wagner David A. , Mahmood Hikmat F. , Yaman Ismail O.
Published: June 2008

The search for weight reduction opportunities to improve corporate average fuel economy has led the auto industry to investigate light weight materials such as aluminum and magnesium. These materials can reduce vehicle weight while satisfying crash safety requirements of corporate, government, and independent insurance agencies. As a result, designs of several vehicles have been fully migrated from steel to aluminum while many other vehicles have opted to substitute lighter materials at the component and system levels. An investigation has been conducted on the front end principal crash energy absorbing rails to convert the original HSLA350 steel structural members into 5754NG aluminum. The investigation shows that while the substitution of aluminum at the right thickness can achieve lighter weight and higher specific energy, additional design parameters such as design load targets remain a major challenge. A comparison of steel versus aluminum mean crash loads, crash energy management, weight saved, specific energy, and design load target highlights some of these challenges. The results from an experimental investigation of stamped 5754NG aluminum sheet rails show the substitution of stamped 5754NG aluminum sheets for steel rails reduces the weight of each of the front rails by 3.3 (lb) and enhances the specific crash energy management efficiency by 38%. To solve the design load target challenge, the same investigation extends to higher strength 6xxx series extruded aluminum material using CAE modeling and demonstrates an increase in crash energy management efficiency of up to 80%.
Experimental Study on the Crash Performance of Aluminum and Steel Rails
Authors: Madasamy Chelliah , Faruque Omar , Tyan Tau
Published: June 2008

Increasing government mandated CAFE´ standards are forcing the OEMs to aggressively reduce vehicle weight. Aluminum, with a density of about a third of that of steel, has been established as a viable alternative to steel for the construction of the automotive body structure. However, for aluminum sheet metals, there are still lingering concerns about the reliability and robustness of the available joining techniques such as spot-welding, riveting etc. The investigation reported in this paper was aimed at evaluating the relative performance of self-pierced riveted aluminum rails as compared to spot-welded mild steel and high strength steel rails. A series of straight and curved (S-shaped) rails made of aluminum, mild steel, and high strength steel have been tested. Other design parameters considered in this study include sheet metal thickness, rivet/weld location, rivet/weld spacing, adhesives, temperature, and impact speed. As were observed from the tests, axial crush mode dominated the deformation of all straight rails while bending dominated the deformation of the curved rails. Statistical analysis was performed to find the relative importance and effects of each variable on the average crush load, maximum load and energy absorption. For aluminum rails, the thickness of the sheet metal was found to be the primary controlling factor for both straight and S-rails. Other factors i.e. rivet spacing/location, adhesives, temperature and impact speed, had no significant affect on the performance of the rails. For the steel rails, the sheet metal thickness, impact speed, temperature and material properties, were all found to be significant for the crash behavior. It was also found that the aluminum rails have higher specific energy absorption than the steel rails confirming that aluminum as a material is more efficient in absorbing crush energy than steel.
Use of Stochastic Analysis for FMVSS210 Simulation Readiness for Correlation to Hardware Testing
Authors: Sharma Amit , Deshpande Ashok , Nayak Raviraj
Published: June 2008

The FMVSS210 regulation establishes requirements for seat belt assembly anchorages to be strong enough for effective occupant restraint. The belt separation from the vehicle structure in crash tests needs to be avoided. Federal government mandate requires use of Pelvic and Torso Body Blocks for testing belt anchor strengths for lap and shoulder belts respectively. The belt anchorages are expected to withstand loads of 13.34 kN if both lap and shoulder belts are used and 22.24 kN if only lap belts are used. The analytical simulation of the hardware test is done using explicit dynamic code LS-DYNA. Hardware testing is of quasi-static nature while the simulation uses the dynamic code. However the analysis could be made to approach the quasi-static test by adjusting some input parameters in the simulation. In addition some input parameters need adjustment for making the model robust and to make it correlate to the hardware test. This study involves the use of Optimal Symmetnc Latin Hypercube Design to explore the design space, and to develop a fast surface response model. This response model can be viewed as a surrogate model to the actual LS-DYNA simulation and is used in this work to rank the input parameters by the percent contdbution they make towards the variation of the desired output responses. After determining the fit of the response model, it is used to perform the stochastic simulation. The confidence interval for test correlation prediction can then be estimated. This technique can further be used to do design sensitivity studies and for optimizing the vehicle structure with respect to FMVSS210 regulation.
Integration of Hydroforming Analysis of Front-End Structures Into Full Vehicle Crash Analysis
Authors: Mahadevan Kumar , Faruque Omar , Cheng James , Qiu Yishan J. , Dombek Barry L.
Published: June 2008

Changes in gauge and material properties are the trademarks of hydroforming process used for any parts. These changes may be large enough to affect the vehicle responses under impact loading in a significant way. An investigation was carried out to determine how full vehicle crash responses are affected by these changes and the findings are reported in this paper. Key to this study has been a methodology to map the gauge and property changes, obtained from a forming simulation, to FEA models created for crash analyses. The mapping process thus allows one to consider the property and gauge changes as an initial condition during crash simulation. A number of full vehicle crash simulations were conducted and the results are compared with the corresponding test data. The entire procedure has been verified using the CAE models developed for simulating hydroforming and frontal impact behavior of a vehicle program. The implementation of the developed methodology to other vehicle programs is straightforward.
A Frequency Domain Force Model With Shearing and Ploughing Mechanisms for a Generalized Helical End Mill
Authors: Wang J.-J. Junz , Zheng C. M.
Published: June 2008

For a generalized helical end mill, this paper presents a frequency domain force model considering the ploughing as well as the shearing mechanisms. The differential chip load and the corresponding cutting forces are first formulated through differential geometry for a general helical cutting edge. The differential cutting force is assumed to be a linear function of the chip load with a proportional shearing force and a constant ploughing force. The total milling force in the angle domain is subsequently composed through convolution integration and analyzed by Fourier analysis. The frequency domain model has the parameters of a general milling process all integrated in a single framework with their roles clearly defined so that Fourier coefficients of the milling force can be obtained for any analytically definable helical cutter. Applications are illustrated for three common helical cutters: the cylindrical, taper, and ball end mills. Furthermore, as an inverse application, a linear algebraic equation is formulated for the identification of six cutting constants from the average forces of two slot milling tests. Demonstration and verification of the milling force model as well as the identification of cutting constants are carried out through experiments with three types of milling cutters.
Thermal Warpage and Pressure Nonlinearity Analyses for Monolithic Piezoresistive Sensing Elements
Authors: Chiou J. Albert
Published: June 2008

This paper presents thermal stress simulation results for a monolithic pressure sensing element design. The basic design concept is to fabricate a standard submicron CMOS process with appropriate modifications to integrate on-chip signal conditioning circuits with piezoresistive sensing elements with anisotropic-etched diaphragms. The stress simulation is used to estimate the electromechanical behavior of a new monolithic sensing element design. The major tasks are to predict ripple deformation of the silicon diaphragm due to thermal residual stresses from multiple passivation layers, find an optimal placement location for the piezoresistive transducer with the highest stress sensitivity or largest full scale span (FSS), and estimate the pressure nonlinearity.
A Wafer-Level Vacuum Packaging Technology Utilizing Electroplated Nickel
Authors: Stark Brian H. , Najafi Khalil
Published: June 2008

In recent years, there has been an increasing demand for low temperature (<400°C) packaging technologies that can vacuum seal MEMS devices at the wafer level with a minimal amount of wasted die area. Several emerging classes of devices require wafer-level vacuum packaging. There has been growing development of micro-resonators for RF communications systems [1]. The devices require the high Q-factor performance generated by vacuum sealing in order to function as highly selective filters and oscillators. There has also been considerable development in the field of resonant gyroscopes [2], which also require a low pressure ambient for optimal performance. The rapid development of MEMS devices requiring low cost vacuum packaging has outpaced the development of suitable sealing technologies.
Finite Element Analysis on Soft-Pad Grinding of Wire-Sawn Silicon Wafers
Authors: Xin X. J. , Pei Z. J. , Liu Wenjie
Published: June 2008

Silicon is the primary semiconductor material used to fabricate microchips. The quality of microchips depends directly on the quality of starting silicon wafers. A series of processes are required to manufacture high quality silicon wafers. Surface grinding is one of the processes used to flatten the wire-sawn wafers. A major issue in grinding of wire-sawn wafers is the reduction and elimination of wire-sawing induced waviness. Several approaches (namely, combination of grinding and lapping, reduced chuck vacuum, soft-pad, and wax mounting) have been proposed to address this issue. The results of finite element analysis modeling of these approaches have shown that soft-pad grinding is the most promising approach since it is very effective in reducing the waviness and very easy to be adopted to conventional grinding environment. This paper presents a study of finite element analysis on soft-pad grinding of wire-sawn silicon wafers, covering the mechanisms of waviness reduction and the effects of pad material properties.
Mechanical Response of Surface-Micromachined Beams Exposed to Short-Pulse Laser Irradiation
Authors: Rogers James W. , Phinney Leslie M.
Published: June 2008

Due to the small dimensions of microelectromechanical systems (MEMS), real-time imaging and metrology techniques must be developed for characterizing MEMS devices. This paper describes an interferometric imaging system used to visualize the mechanical response of MEMS structures during laser irradiation. By incorporating a high-speed CCD camera into the interferometric imaging system, video showing the transient repair of adhered microcantilevers is captured. The video clearly reveals that the failed structures peel from the substrate as they are repaired. The time-scale for repair is on the order of ten milliseconds and depends on the temperature difference between the cantilever and substrate created by the laser. Transient buckling and relaxation due to differential thermal expansion and subsequent cooling is also captured using the transient imaging system. These experimental results provide insight into the energy absorption and transport processes in microstructures during and after laser heating.
MEMS Foundry for High Volume Manufacturing and Product Reliance
Authors: Koester David A. , Baumhover James P.
Published: June 2008

The establishment of standard processes has become increasingly important in the growth of MEMS technology. Standard processes enable developers to leverage stable process platforms without the risk, time and costs associated with extensive process development. JDS Uniphase has established multi-user programs in three different process technologies—polysilicon, SOI and metal—that provide easy, cost-effective vehicles for early stage development. These processes also provide low-risk pathways to manufacturing in high volume. This paper discusses these processes and provides additional background on the importance of a quality system in the management of foundry product development. Product reliability testing is discussed in the context of a customer/foundry model.
Ultrasonic Rapid Manufacturing: Implementation and Thermo-Mechanical Analysis
Authors: Yadav Shailendra , Doumanidis Charalabos
Published: June 2008

This paper addresses a novel non-thermal Ultrasonic Rapid Manufacturing (URM), for layered parts based on Ultrasonic Metal Welding (USW). Its laboratory implementation, automation and integration are described first. The thermo-mechanical process aspects (i.e. heat generation and resulting temperature effects) during each cycle of ultrasonic welding are then studied. The technical advantages of ultrasonic welding process, including fabrication of dense, full-strength functional solid metal parts, multi-material composites, and active parts with embedded intelligent components and electronic, mechatronic, optic and fluidic structures, are examined.
Enhanced Industrial Applicability of Aluminum Alloy by Coating Technique With Titanium/Carbon Compositionally Gradient Film Using Magnetron Co-Sputtering
Authors: Sonoda T. , Watazu A. , Zhu J. , Shi W. , Kamiya A. , Kato K. , Asahina T.
Published: June 2008

Coating of Aluminium alloy substrates with Ti/C compositionally gradient films was examined by magnetron sputtering, in order to improve not only the abrasion resistance of the alloy but also the adhesion between the deposited film and the alloy substrate with preserving the high hardness of such ceramic coatings. The Ti/C compositionally gradient films were deposited by co-sputtering of 2 sputter cathodes which had a pure titanium target and a titanium carbide target respectively, and their compositionally gradient was realized by varying continuously the electric power supplied to each sputter cathode. Under visual observation, the obtained Ti/C compositionally gradient films appeared to be uniform and adhesive. According to AES in-depth profiles, the carbon (C) concentration in the film gradually decreased in depth direction from trhe surface toward the substrate, confirming that a Ti/C compositionally gradient film had formed on the alloy substrate. On the basis of XRD, it was found that titanium carbide and α-titanium phases were formed in the gradient film. Furthermore the Vickers hardness of the film reached over Hv=2600. Therefore the abrasion resistance of the alloy and the adhesion of the hard coatings were expected to be improved by this method.
Parallel Computation of Unsteady Incompressible Viscous Flows Using an Unstructured Multigrid Method
Authors: Zhao Yong , Tai Chin Hoe
Published: June 2008

The development and validation of a parallel unstructured non-nested multigrid method for simulation of unsteady incompressible viscous flow is presented. The Navier-Stokes solver is based on the artificial compressibility method (ACM) [10] and a higher-order characteristics-based finite-volume scheme [8] on unstructured multigrids. Unsteady flow is calculated with an implicit dual time stepping scheme. The parallelization of the solver is achieved by a multigrid domain decomposition approach (MG-DD), using the Single Program Multiple Data (SPMD) programming paradigm and Message-Passing Interface (MPI) for communication of data. The parallel codes using single grids and multigrids are used to simulate steady and unsteady incompressible viscous flows over a circular cylinder for validation and performance evaluation purposes. Speedups and parallel efficiencies obtained by both the parallel single-grid and multigrid solvers are reasonably good for both test cases, using up to 32 processors on the SGI Origin 2000. A maximum speedup of 12 could be achieved on 16 processors for the unsteady flow. The parallel results obtained agree well with those of serial solvers and with numerical solutions obtained by other researchers, as well as experimental measurements.
Ion Engine and Hall Thruster Development at the NASA Glenn Research Center
Authors: Domonkos Matthew T. , Patterson Michael J. , Jankovsky Robert S.
Published: June 2008

NASA’s Glenn Research Center has been selected to lead development of NASA’s Evolutionary Xenon Thruster (NEXT) system. The central feature of the NEXT system is an electric propulsion thruster (EPT) that inherits the knowledge gained through the NSTAR thruster that successfully propelled Deep Space 1 to asteroid Braille and comet Borrelly, while significantly increasing the thruster power level and making improvements in performance parameters associated with NSTAR. The EPT concept under development has a 40 cm beam diameter, twice the effective area of the Deep-Space 1 thruster, while maintaining a relatively-small volume. It incorporates mechanical features and operating conditions to maximize the design heritage established by the flight NSTAR 30 cm engine, while incorporating new technology where warranted to extend the power and throughput capability. The NASA Hall thruster program currently supports a number of tasks related to high power thruster development for a number of customers including the Energetics Program (formerly called the Space-based Program), the Space Solar Power Program, and the In-space Propulsion Program. In program year 2002, two tasks were central to the NASA Hall thruster program: 1.) the development of a laboratory Hall thruster capable of providing high thrust at high power; 2.) investigations into operation of Hall thrusters at high specific impulse. In addition to these two primary thruster development activities, there are a number of other on-going activities supported by the NASA Hall thruster program. These additional activities are related to issues such as thruster lifetime and spacecraft integration.
Effect of Curing Process on Intercalation and Exfoliation Behavior of Epoxy/Clay Nanocomposites
Authors: Song Chunfang , Lin Weiwei , Wang Qi , Qiu Yiping
Published: June 2008

Effects of curing agents, curing conditions, and curing degree on intercalation and exfoliation behavior of epoxy/clay nanocomposites were investigated. Epoxy was cured with five curing agents, DETA, DDM, DMP-30 and two modified amines, with different curing speeds at various temperatures (from low to high). Curing degree and distance between layers of clay were measured by FTIR, XRD and TEM respectively. It was found that it was easy to intercalate clay in epoxy resin, while clay exfoliation in epoxy resin was dependent more on the curing conditions than on curing agents. Under certain curing conditions when curing speed of interlayer epoxy resin is faster than that of extralayer and fully reaches curing, exfoliation easily takes place with all these curing agents and epoxy/clay nanocomposites can be prepared. At the same time, the distance between clay layers increased from 17.5Å to about 100Å. When the curing temperature was too low, diffusion speed of the epoxy resin and the curing agents can influence the clay exfoliation. When the curing temperature was too high, epoxy was cured too rapidly, such that the high viscosity and the resultant mechanical forces will stop the exfoliation process. Only under properly temperatures when the curing speed of the interlayer epoxy is higher than that of the extralayer epoxy can exfoliation take place.
Mechanical Properties of Carbon Nanotubes
Authors: Sun Xuekun , Wang Youqi
Published: June 2008

Nano-scale finite element approach was used to predict the mechanical properties of carbon nanotubes. The unit-cell isolation scheme was same as that from Eric Seather [1], and nothing was assumed to exist inside any nanotube. Arm-chair, zigzag and chiral type of nanotubes with different radii were discussed in detail. The longitudinal modulus of nanotubes Ez was found to decrease with increasing nanotube radius, but to be independent of nanotube helicity. The modulus was not over 0.5 TPa for any case. Meanwhile, Poisson’s ratio νzθ was also predicted.
VLSI Hotspot Cooling Using Two-Phase Microchannel Convection
Authors: Koo Jae-Mo , Im Sungjun , Cho Eun Seok , Prasher Ravi S. , Wang Evelyn , Jiang Linan , Bari Abdullahel , Campion David , Fogg David , Kim Min Soo , Kenny Thomas W. , Santiago Juan G. , Goodson Kenneth E.
Published: June 2008

Two-phase microchannel heat sinks are promising for the cooling of high power VLSI chips, in part because they can alleviate spatial temperature variations, or hotspots. Hotspots increase the maximum junction temperature for a given total chip power, thereby degrading electromigration reliability of interconnects and inducing strong variations in the signal delay on the chip. This work develops a modeling approach to determine the impact of conduction and convection on hotspot cooling for a VLSI chip attached to a microchannel heat sink. The calculation approach solves the steady-state two-dimensional heat conduction equations with boundary conditions of spatially varying heat transfer coefficient and water temperature profile. These boundary conditions are obtained from a one-dimensional homogeneous two-phase model developed in previous work, which has been experimentally verified through temperature distribution and total pressure drop measurements. The new simulation explores the effect of microchannels on hotspot alleviation for 20 mm × 20 mm silicon chips subjected to spatially varying heat generation totaling 150 W. The results indicate that a microchannel heat sink of thickness near 500 μm can yield far better temperature uniformity than a copper spreader of thickness 1.5 mm.
Cooling of a Finned Cylinder by a Jet Flow of Air
Authors: Gori F. , De Nigris F. , Pippione E. , Scavarda G.
Published: June 2008

The paper describes a patented proposal to use jets of air in the cooling system of heavy trucks. Preliminary tests have been carried out, in the Heat Transfer Laboratory of the University of Rome “Tor Vergata”, to evaluate the heat transfer characteristics of a jet flow of air, impinging onto an externally finned cylinder. The cylinder is internally heated with an electric system. Thermocouples, located inside the cylinder, allow to measure the wall temperatures, in order to calculate the local and average convective heat transfer coefficients. A preliminary design of the practical apparatus, applied to heavy trucks, has been done in cooperation with Iveco. Nozzles are designed to be put after the fan of heavy trucks to converge air, in the form of jets, onto the tube where the charged air is flowing from the outlet of the turbo-compressor. The efficiency of the jet flow increases the cooling performances but, due to the high temperature at the outlet of the turbo-compressor, it may not be enough. The heat transfer cooling performances are enhanced if the tube to be cooled is externally finned. Some preliminary experiments have been carried out in a real scale bank test of an heavy truck engine at the Engineering Testing Laboratories Department of Iveco. Comparisons are done between the experiments and a simple theoretical model. Some conclusions are drawn about the cooling at different fluid dynamics conditions of the impinging jets.
Study of Refrigerant Mixtures With Gas/Liquid Injection
Authors: Sami Samuel M. , Aucoin Shawn
Published: June 2008

In this paper, the impact of gas/liquid injection on the behaviour of new alternative refrigerant mixtures such as; R-410A, R-507, R-407C, and R-404A is discussed, analysed and presented. The test results were obtained using an air-source heat pump set up with enhanced surface tubing heat exchanger under various gas/liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE Standards. During the course of this experimental study, the performance characteristics of some proposed substitutes under various gas and gas/liquid injection ratios have been investigated, analysed and compared to that with no injection. The performance data demonstrated that the effect of gas/liquid injection on mixture behaviour and the heat exchanger capacity varies from mixture to another depending upon the mixture composition, boiling point and the evaporation temperature.
Transient Reflectance Response to Hot Electron Relaxation in InP Based Films
Authors: Klopf J. Michael , Hostetler John L. , Norris Pamela M.
Published: June 2008

Advancements in technologies related to thin film growth have led to astoundingly complex integrated photonic devices. The reliability of these devices relies upon the precise control of the band gap and absorption mechanisms in the thin film structures. Photon absorption in these devices can result in a reduction of laser efficiency as well as thermal runaway. To improve device performance prediction, an increased understanding of the localized absorption processes is paramount. A pump-probe technique is being developed to measure the transient absorption during hot carrier relaxation. This method relies upon the generation of hot carriers by the absorption of an intense ultrashort laser pulse. The change in reflectance due to hot carrier generation and relaxation is monitored using a probe pulse focused at the center of the excited region. The transient reflectance is measured as a function of the relative delay between the pump and probe pulses. Utilizing ultrashort laser pulses (τp ∼ 190 fs) it is possible to attain sub-picosecond resolution of the transient reflectance during hot carrier relaxation. Transient changes in the reflectance can then be related to transient changes in the absorption mechanisms of the film. Preliminary measurements made with this technique have shown clear differences in the transient reflectance of doped and undoped Indium Phosphide (InP) based films. This study will form the basis for development of a transient thermoreflectance model during hot carrier relaxation in III-V semiconductors.
Failure Prediction of Flip Chip Packages Using Finite Element Technique
Authors: Hasan Abm , Mahfuz H. , Saha M. , Jeelani S.
Published: June 2008

Flip-chip electronic package undergoes thermal loading during its curing process and operational life. Due to the thermal expansion coefficient (CTE) mismatch of various components, the flip-chip assembly experiences various types of thermally induced stresses and strains. Experimental measurement of these stresses and strains is extremely tedious and rigorous due to the physical limitations in the dimensions of the flip-chip assembly. While experiments provide accurate assessment of stresses and strains at certain locations, a parallel finite element (FE) analysis and analytical study can complementarily determine the displacement, strain and stress fields over the entire region of the flip-chip assembly. Such combination of experimental, finite element and analytical studies are ideal to yield a successful stress analysis of the flip-chip assembly under the various loading conditions. In this study, a two-dimensional finite element model of the flip-chip consisting of the silicon chip, underfill, solder ball, copper pad, solder mask and substrate has been developed. Various stress components under thermal loading condition ranging from −40°C to 150°C have been determined using both the finite element and analytical methods. Stresses such as (σ11, σ12, ε12 etc. are extracted and analyzed for the individual components as well as the entire assembly, and the weakest positions of the flip-chip have been discovered. Detailed description of FE modeling is presented and the different failure modes of chip assembly are discussed.
Effective Thermal-Mechanical Modeling of Solder Joints
Authors: Cheng Hsien-Chie , Yu Chin-Yin , Chen Wen-Hwa
Published: June 2008

An effective, two-staged global/local finite element (FE) modeling technique is proposed for characterizing the thermal-mechanical behaviors of solder joints in area array type packages under the temperature cycling. It consists of two essential features: the employment of a compact global FE model in the global analysis, and a two-staged, hybrid constitutive modeling strategy for solder materials, which is to apply the elastoplasticity constitutive law for solder joints in the global analysis during the first temperature rise while utilize the viscoelasticity in the rest of periods. To substantiate the proposed modeling technique, a large-scaled, 3-D FE model with a very fine mesh is constructed as a baseline model. The result derived from the proposed approach is then accordingly compared with those of the baseline solution. From these comparing results, it turns out that the proposed 3-D global/local FE modeling technique is an effective mean for simulating the thermal-mechanical behaviors of solder joints.
A Lithography-Based Compliant Chip-to-Substrate Wafer-Level Interconnect
Authors: Zhu Qi , Ma Lunyu , Sitaraman Suresh K.
Published: June 2008

As the rapid advances in IC design and fabrication continue to challenge and push the electronic packaging technology, in terms of fine pitch, high performance, low cost, and good reliability, compliant interconnects show great advantages for next-generation packaging. β-fly is designed as a compliant chip-to-substrate interconnect for performing wafer-level probing and for packaging without underfill. β-fly has good compliance in all directions to compensate the coefficient of thermal expansion (CTE) mismatch between the silicon die and an organic substrate. The fabrication of β-fly is similar to standard IC fabrication, and wafer-level packaging makes it cost effective. In this work, self-weight effect and stress distribution under planar displacement loading of β-fly is studied. The effect of geometry parameters on mechanical and electrical performance of β-fly is also studied. β-fly with thinner and narrower arcuate beams with larger radius and taller post is found to have better mechanical compliance. In addition to mechanical compliance, electrical characteristics of β-fly have also been studied in this work. However, it is found that structures with excellent mechanical compliance cannot have good electrical performance. Therefore, a trade off is needed for the design of β-fly. Response surface methodology and an optimization technique have been used to select the optimal β-fly structure parameters.
Prediction of Equilibrium and Stability of Molten Solder Profiles by Finite Element Analysis
Authors: Nagata Takahiro , Kobayashi Takaya , Sakuta Hiroshi
Published: June 2008

In development of surface mount technology for Ball Grid Array (BGA) or flip-chip assemblies, it is important to reduce stress concentration in solder joints as it is immediately effective in improving the fatigue life of the assembly. Thus, the ability to predict and control the joint geometries is critical to obtaining robust and reliable designs of interconnects. Other than the issue of the bump shape, there are many problems concerning soldering such as bridging or self-alignment in which surface tension is definitely involved. This paper attempts to apply the FEM approach in solving these problems. Rigid-plastic FEM which is based on iteration for the velocity field in an incompressible viscous fluid is an approach to large deformation analysis. The flow stress is described by the viscosity of the fluid and the strain rate. By introducing an automatic mesh updating procedure, transient problems with free boundary can be treated. We applied this concept to the prediction of solder joint shapes. In this kind of problem, effects of surface tension dominate. Since surface tension is a distributed load that depends on surface curvature, we employed 2D and 3D methods in which the load is updated based on instantaneous state of surface. To verify the accuracy of this method, we analyzed some shape and stability problems of liquid drops for which theoretical solutions were given. Practical applications of the method were also performed for the 2D and 3D solder joint problems, and the results showed a good agreement with experimental ones.
Intersection of the RNA Interference and X-Inactivation Pathways
Authors: Ogawa Yuya , Sun Bryan K. , Lee Jeannie T.
Published: June 2008

In mammals, dosage compensation is achieved by X-chromosome inactivation (XCI) in the female. The noncoding
Xist
gene initiates silencing of the X chromosome, whereas its antisense partner
Tsix
blocks silencing. The complementarity of Xist and Tsix RNAs has long suggested a role for RNA interference (RNAi). Here, we report that murine Xist and Tsix form duplexes in vivo. During XCI, the duplexes are processed to small RNAs (sRNAs), most likely on the active X (Xa) in a Dicer-dependent manner. Deleting
Dicer
compromises sRNA production and derepresses
Xist.
Furthermore, without Dicer, Xist RNA cannot accumulate and histone 3 lysine 27 trimethylation is blocked on the inactive X (Xi). The defects are partially rescued by truncating Tsix. Thus, XCI and RNAi intersect, down-regulating
Xist
on Xa and spreading silencing on Xi.
Effects of sports activity in athletes with bicuspid aortic valve and mild aortic regurgitation
Authors: Galanti G , Stefani L , Toncelli L , Vono M C R , Mercuri R , Maffulli N
Published: June 2008

Objective

In this study, the impact of regular training on left ventricle morphology in a group of athletes with bicuspid aortic valve (BAV) was evaluated.

Design

Longitudinal cohort study. A group of competitive athletes with BAV was followed up with a yearly standard echocardiographic examination for 5 years.

Setting

Sport Medicine Centre, University of Florence, Pre-Participation Protocol Study

Participants

A group of 88 consecutive athletes diagnosed with BAV was identified in the period January to December 1999, and 30 of these completed a 5-year follow-up. They were compared with a group of 56 athletes with a normal tricuspid valve (TAV).

Results

BAV athletes showed significant progressive increase in left ventricular dimensions and aortic diameters at four levels. The values were within the range of the general and non-athletic BAV populations. In TAV athletes, the aortic and left ventricle dimensions did not increase significantly and remained within physiological range.

Conclusions

Left ventricular dimensions in competitive BAV athletes remain within the normal range. There is, however, a significant progressive increase in the BAV group compared with the TAV group. These results are in agreement with data obtained in previous studies on the non-athletic BAV population. Sports activity does not have an additional effect on cardiac morphology in athletes with asymptomatic BAV associated with mild regurgitation, for at least 5 years.
Longitudinal rates of smoking in a schizophrenia sample
Authors: Goldberg J O , Van Exan J
Published: June 2008

Objectives:

Despite the well documented link between high rates of smoking and schizophrenia, there have been no longitudinal studies that have looked at rates of smoking and associated factors over time. This prospective study examined the longitudinal rates of smoking in a schizophrenia clinic sample over a decade.

Methods:

Longitudinal survey research was conducted in a well established community-based psychiatric rehabilitation program in Hamilton, Ontario, Canada, providing long-term intensive case management and rehabilitation skills training. Stable community outpatients diagnosed with schizophrenia were surveyed initially in 1995 (n = 102) and then resurveyed 11 years later in 2006 (n = 76). The main outcome measure was self-report of smoking status.

Results:

Smoking rates dropped significantly over time, with evidence that the number of “quitters” tripled over the past decade and the number of “everyday” smokers decreased by almost a third from 63.2% down to 43.3% (p<0.001).

Conclusions:

The findings from the present study suggest that it is possible to obtain reduced smoking prevalence over time in a selected schizophrenia outpatient sample, though further research is required to better understand the factors related to quitting smoking in individuals with schizophrenia.
SERVICE-ORIENTED COMPUTING: A RESEARCH ROADMAP
Authors: PAPAZOGLOU MICHAEL P. , TRAVERSO PAOLO , DUSTDAR SCHAHRAM , LEYMANN FRANK
Published: June 2008

Service-Oriented Computing (SOC) is a new computing paradigm that utilizes services as the basic constructs to support the development of rapid, low-cost and easy composition of distributed applications even in heterogeneous environments. The promise of Service-Oriented Computing is a world of cooperating services where application components are assembled with little effort into a network of services that can be loosely coupled to create flexible dynamic business processes and agile applications that may span organizations and computing platforms. The subject of Service-Oriented Computing is vast and enormously complex, spanning many concepts and technologies that find their origins in diverse disciplines that are woven together in an intricate manner. In addition, there is a need to merge technology with an understanding of business processes and organizational structures, a combination of recognizing an enterprise's pain points and the potential solutions that can be applied to correct them. The material in research spans an immense and diverse spectrum of literature, in origin and in character. As a result research activities are very fragmented. This necessitates that a broader vision and perspective be established — one that permeates and transforms the fundamental requirements of complex applications that require the use of the Service-Oriented Computing paradigm.

This paper provides a Service Oriented Computing Roadmap and places on-going research activities and projects in the broader context of this roadmap. This research roadmap launches four pivotal, inherently related, research themes to Service-Oriented Computing: service foundations, service composition, service management and monitoring and service-oriented engineering.
Reactive hyperemia in the human liver
Authors: Hinghofer-Szalkay Helmut G. , Goswami Nandu , Rössler Andreas , Grasser Erik , Schneditz Daniel
Published: June 2008

We tested whether hepatic blood flow is altered following central hypovolemia caused by simulated orthostatic stress. After 30 min of supine rest, hemodynamic, plasma density, and indocyanine green (ICG) clearance responses were determined during and after release of a 15-min 40 mmHg lower body negative pressure (LBNP) stimulus. Plasma density shifts and the time course of plasma ICG concentration were used to assess intravascular volume and hepatic perfusion changes. Plasma volume decreased during LBNP (−10%) as did cardiac output (−15%), whereas heart rate (+14%) and peripheral resistance (+17%) increased, as expected. On the basis of ICG elimination, hepatic perfusion decreased from 1.67 ± 0.32 (pre-LBNP control) to 1.29 ± 0.26 l/min (−22%) during LBNP. Immediately after LBNP release, we found hepatic perfusion 25% above control levels (to 2.08 ± 0.48 l/min, P = 0.0001). Hepatic vascular conductance after LBNP was also significantly higher than during pre-LBNP control (21.4 ± 5.4 vs. 17.1 ± 3.1 ml·min−1·mmHg−1, P < 0.0001). This indicates autoregulatory vasodilatation in response to relative ischemia during a stimulus that has cardiovascular effects similar to normal orthostasis. We present evidence for physiological post-LBNP reactive hyperemia in the human liver. Further studies are needed to quantify the intensity of this response in relation to stimulus duration and magnitude, and clarify its mechanism.
Increased colonic sodium absorption in rats with chronic renal failure is partially mediated by AT1receptor agonism
Authors: Hatch Marguerite , Freel Robert W.
Published: June 2008

To test the hypothesis that colonic Na+transport is altered in the 5/6 nephrectomized rat model of chronic renal failure (CRF), we measured Na+fluxes across distal colon from control (CON), CRF, and CRF rats treated with the angiotensin II (ANG II) receptor antagonist losartan (+LOS). We also evaluated overall fluid and Na+balance and compared colonic protein and mRNA expression profiles for electroneutral [sodium-hydrogen exchanger (NHE)] and electrogenic Na+transport [epithelial sodium channel (ENaC)] in these groups. Consistent with a 60% enhancement in colonic Na+absorption in CRF, urinary Na+excretion increased by about 50% while serum Na+homeostasis was maintained. These CRF-induced changes in Na+handling were normalized by treatment with LOS. Net Na+absorption was also stimulated in in vitro tissues from CON rats following acute serosal addition of ANG II (10−7M), and this increase was blocked by AT1antagonism but not by an AT2antagonist. In CRF, colonic protein and mRNA expression variably increased for apical NHE2, NHE3, and ENaC α-, β-, γ-subunits, whereas expression of basolateral NHE1 and Na+-K+-ATPase (α-isoform) remained unaltered. Upregulation of the ENaC subunit mRNA was attenuated somewhat by LOS treatment. Previously, we showed that colonic AT1receptor protein is upregulated twofold in CRF, and here we find that AT1and AT2mRNA and AT2protein abundance is unchanged in CRF. We conclude that Na+absorption in CRF rat distal colon is increased due to elevated expression of proteins mediating electroneutral and electrogenic uptake and that it is partially mediated by AT1receptors.
Mesenchymal stromal cells genetically engineered to overexpress IGF-I enhance cell-based gene therapy of renal failure-induced anemia
Authors: Kucic Terrence , Copland Ian B. , Cuerquis Jessica , Coutu Daniel L. , Chalifour Lorraine E. , Gagnon Raymonde F. , Galipeau Jacques
Published: June 2008

We previously demonstrated that erythropoietin (EPO)-secreting mesenchymal stromal cells (MSC) can be used for the long-term correction of renal failure-induced anemia. The present study provides evidence that coimplantation of insulin-like growth factor I (IGF-I)-overexpressing MSC (MSC-IGF) improves MSC-based gene therapy of anemia by providing paracrine support to EPO-secreting MSC (MSC-EPO) within a subcutaneous implant. IGF-I receptor RNA expression in murine MSC was demonstrated by RT-PCR. Functional protein expression was confirmed by immunoblots and MSC responsiveness to IGF-I stimulation in vitro. IGF-I was also shown to improve MSC survival following staurosporin-induced apoptosis in vitro. A cohort of C57Bl/6 mice was rendered anemic by right kidney electrocoagulation and left nephrectomy. MSC-EPO were subsequently admixed in a bovine collagen matrix and implanted, in combination with MSC-IGF or MSC null, by subcutaneous injection in renal failure mice. In mice receiving MSC-EPO coimplanted with MSC-IGF, hematocrit elevation was greater and enhanced compared with control mice; heart function was also improved. MSC-IGF coimplantation, therefore, represents a promising new strategy for enhancing MSC survival within implanted matrices and for improving cell-based gene therapy of renal anemia.
Essential amino acid and carbohydrate ingestion before resistance exercise does not enhance postexercise muscle protein synthesis
Authors: Fujita Satoshi , Dreyer Hans C. , Drummond Micah J. , Glynn Erin L. , Volpi Elena , Rasmussen Blake B.
Published: June 2008

Ingestion of an essential amino acid-carbohydrate (EAA + CHO) solution following resistance exercise enhances muscle protein synthesis during postexercise recovery. It is unclear whether EAA + CHO ingestion before resistance exercise can improve direct measures of postexercise muscle protein synthesis (fractional synthetic rate; FSR). We hypothesized that EAA + CHO ingestion before a bout of resistance exercise would prevent the exercise-induced decrease in muscle FSR and would result in an enhanced rate of muscle FSR during postexercise recovery. We studied 22 young healthy subjects before, during, and for 2 h following a bout of high-intensity leg resistance exercise. The fasting control group ( n = 11) did not ingest nutrients, and the EAA + CHO group ( n = 11) ingested a solution of EAA + CHO 1 h before beginning the exercise bout. Stable isotopic methods were used in combination with muscle biopsies to determine FSR. Immunoblotting procedures were utilized to assess cell signaling proteins associated with the regulation of FSR. We found that muscle FSR increased in the EAA + CHO group immediately following EAA + CHO ingestion ( P < 0.05), returned to basal values during exercise, and remained unchanged at 1 h postexercise. Muscle FSR decreased in the fasting group during exercise and increased at 1 h postexercise ( P < 0.05). However, the 2 h postexercise FSR increased by ∼50% in both groups with no differences between groups ( P > 0.05). Eukaryotic elongation factor 2 phosphorylation was reduced in both groups at 2 h postexercise (EAA + CHO: 39 ± 7%; fasting: 47 ± 9%; P < 0.05). We conclude that EAA + CHO ingestion before resistance exercise does not enhance postexercise FSR compared with exercise without nutrients.
Diagnóstico del estreñimiento en niños
Authors: Sauvat Fréderique
Published: June 2008

El estreñimiento es un motivo frecuente de consulta con el pediatra. Como síntoma el estreñimiento puede deberse a diversas causas en términos de frecuencia, naturaleza y gravedad. El estreñimiento puede ser de origen médico o quirúrgico o bien idiopático. Las etiologías quirúrgicas están representadas principalmente por la enfermedad de Hirschsprung. Este es el diagnóstico diferencial principal a pesar de ser 50 veces menos frecuente que el estreñimiento idiopático o funcional. La mejor manera de establecer un diagnóstico es la realización de una historia clínica y una exploración física detalladas con inclusión de la exploración anal. En la mayoría de los casos no se precisan otras exploraciones y todas las investigaciones se han realizado en conformidad con las consideraciones clínicas.
Macroamylasemia as the First Manifestation of Celiac Disease
Authors: Depsames Roman , Fireman Zvi , Niv Eva , Kopelman Yael
Published: June 2008

Macroamylasemia is a biochemical disorder characterized by an elevated serum amylase activity resulting from the circulation of a macromolecular complex of amylase with a serum component, often an immunoglobulin. The increased molecular weight of this complex prevents the normal renal excretion of the enzyme. A few cases of celiac patients with macroamylasemia have been published in whom the biochemical disorder disappeared after treatment with a gluten-free diet.