bluuebunny/crossref_metadata_2025 huggingface dataset:
Wire Flexure Fatigue Model for Asymmetric Bond Height
Authors: Meyyappan Karumbu Nathan , Hansen Peter , McCluskey Patrick
Published: May 2010

This paper presents the first physics-of-failure based life prediction model for flexural failure of wires ultrasonically wedge bonded to pads at different heights. The life prediction model consists of a load transformation model and a damage model. The load transformation model determines the cyclic strain at the heel of the wire during temperature cycling. This cyclic strain is created by a change in wire curvature at the heel of the wire resulting from expansion of the wire and displacement of the frame. The damage model calculates the life based on the strain cycle magnitude and the elastic-plastic fatigue response of the wire. The model supports virtual qualification of power modules where wire flexural fatigue is a dominant failure mechanism. The model has been validated using temperature cycling test results, and can be used to derive design guidelines and establish a relation between accelerated test results and field life.
Stress Intensity Factor Analyses of Interface Cracks Between Anisotropic Media in Electronic Packages
Authors: Ikeda Toru , Yamanaga Koh , Miyazaki Noriyuki
Published: May 2010

Delamination from interfaces between dissimilar materials is the primary cause of failure in electronic packages. Fracture mechanics is a powerful tool for the evaluation of delamination. However, many materials used in electronic packages such as composite materials and single crystals are anisotropic materials. Stress intensity factors of an interface crack between dissimilar anisotropic materials which proposed by Hwu are useful for evaluating the reliability of plastic packages. However, numerical methods that can analyze the stress intensity factors of an interface have not been developed. We propose herein a new numerical method for the analysis of an interface crack between dissimilar anisotropic materials. The stress intensity factors of an interface crack are based on the generalized plane strain condition. The energy release rate is obtained by the virtual crack extension method in conjunction with the finite element method for the generalized plane strain condition. The energy release rate is separated into individual modes of stress intensity factors, KI, KII, and KIII, using the principal of superposition. The target problem to be solved is superposed on the asymptotic solution of displacement in the vicinity of an interface crack tip, which is described using the Stroh formalism. Analyses of the stress intensity factors of center interface cracks between semi-infinite dissimilar anisotropic media subjected to concentrated self-balanced loads on the center of crack surfaces as well as to uniform loads are demonstrated. The present method accurately provides the mode-separated stress intensity factors using relatively course meshes for the finite element method.
Multiphysics Design and Analysis Simulations for Power Electronic Device Wirebonds
Authors: Wilkerson Patrick W. , Przekwas Andrzej J. , Chen Chung-Lung
Published: May 2010

Multiscale multiphysics simulations were performed to analyze wirebonds for power electronic devices. Modern power-electronic devices can be subjected to extreme electrical and thermal conditions. Fully coupled electro-thermo-mechanical simulations were performed utilizing CFDRC’s CFD-ACE+ multiphysics simulation software and scripting capabilities. Use of such integrated multiscale multiphysics simulation and design tools in the design process can cut cost, shorten product development cycle time, and result in optimal designs. The parametrically designed multiscale multiphysics simulations performed allowed for a streamlined parametric analysis of the electrical, thermal, and mechanical effects on the wirebond geometry, bonding sites and power electronic device geometry. Multiscale analysis allowed for full device thermo-mechanical analysis as well as detailed analysis of wirebond structures. The multiscale simulations were parametrically scripted allowing for parametric simulations of the device and wirebond geometry as well as all other simulation variables. Analysis of heat dissipation from heat generated in the power-electronic device and through Joule heating were analyzed. The multiphysics analysis allowed for investigation of the location and magnitude of stress concentrations in the wirebond and device. These stress concentrations are not only investigated for the deformed wirebond itself, but additionally at the wirebond bonding sites and contacts. Changes in the wirebond geometry and bonding geometry, easily changed through the parametrically designed simulation scripts, allows for investigation of various wirebond geometries and operating conditions.
Reliability of Low Glass Transition Temperature COTS PEM’s for Space Applications
Authors: Sandor M. , Agarwal S. , Peters D. , Cooper M. S.
Published: May 2010

Microcircuit manufacturers of Plastic Encapsulated Microcircuits (PEM’s) have made changes in epoxy molding compound materials and chemistry, which lower Glass Transition Temperature (Tg). PEM users in harsh environments have concerns if either the part in its application, or in evaluation or assembly, is used close to, or above, the Tg. Various Tg measurement techniques are available and discussed. Test results from one technique is reviewed. The implications of the Tg results on usage of these parts in space applications will be presented. Burn-in/ reliability test results of samples with low Tg PEM’s will be presented. The reliability experiments include testing under different temperatures. The issue being addressed is whether outgassing of molding compounds occurs when the temperature of the molding compound exceeds the Tg. This is a caution noted by many vendors. As an example outgassing of flame retardants can degrade parametric performance and wire bond integrity. This would be the case when PEMS are being qualified for Space applications using burn-in or in storage environments. JPL’s past experience has shown that COTS PEMS parametrics can degrade significantly even when the burn-in temperature is well below the Tg. Two different microcircuits exhibiting low Tg were evaluated. Assessment of final electrical test measurements and yield are shown.
Dynamic Compact Thermal Models Used for Electronic Design: A Review of Recent Progress
Authors: Sabry Mohamed-Nabil
Published: May 2010

Both reliability and performance of electronic systems can be seriously affected by dynamic thermal and electro-thermal effects that take place at the device, chip, package, board and system levels. The marked trend towards miniaturization down to the nano-scale, increases problem complexity due to the large number of devices and multiplicity of physical effects involved. It accentuates also the importance of thermal effects. To deal with such complicated systems, design and analysis heavily rely on compact models. Recent advances have been made to extend the relatively more mature knowledge of static compact thermal models to the dynamic case. Although the theory of dynamic compact models is far from being complete, the wealth of methods proposed has deserved a review highlighting advances made and proposing new axis of research, which is the purpose of this paper.
O+-Ion Implantation for Practical InP-Based Digital Optical Switches
Authors: Barrios Pedro , Janz Siegfried , Golub Ilya , Poole Philip , Chow-Chong Phillip , Poitras Daniel , Sproule Irwin , Malloy Mark , Delaˆge Andre´ , McKinnon Ross , Syrett Barry , El-Mougy Shawky , Abdalla Shawkat
Published: May 2010

The fabrication of Digital Optical Switches with O+-ion implanted - electrical isolated - branches is described. Multiple- vs. single-implantation schemes and their effect on sheet resistance is compared using TLM and SIMS measurements.
High-Density Through-Wafer Electrical Interconnects in Pyrex Substrate Integrated With Micromirror Array
Authors: Wang C. C. , Kudrle T. D. , Bancu M. , Hsiao J. , Mastrangelo C. H.
Published: May 2010

A method for the construction of high density (2.4 mm−2) vertical leads through a pyrex substrate is presented. The pyrex substrate behaves as a TCE (Thermal Coefficient of Expansion) matched interposer that permits anodic bonding of silicon micromirrors on one side and flip-chip bumping of multiplexing electronic chips on its opposite side. Electrical leads consist of 250±25 μm-diameter holes formed by AJM machining and coated with evaporated Au yielding via resistances of 0.5–0.7 Ω. The via holes are sealed with a new spin-cast polyimide tenting process that enables the subsequent patterning of multiple levels of metal using conventional lithographic techniques.
Compact Thermal Representations for Several Fundamental Shapes in Natural Convection
Authors: Brucker Kyle A. , Ressler Kyle T. , Majdalani Joseph
Published: May 2010

In this article, general canonical forms for the effective thermal conductivities of compact heat sink models are derived using perturbation tools. The resulting approximations apply to a large number of fundamental heat sink shapes used in natural convection applications. The effective thermal conductivity is a property that can be assigned to the porous block (i.e., volume of fluid) above the heat sink base that was once occupied by the fins. The increased thermal conductivity of the fluid entering the porous block produces a reduced thermal resistance that matches that of the original heat sink. The use of a compact representation is accompanied by substantial computational savings that promote faster optimization and communication between simulation analysts and design engineers. The generalized approximations for the effective thermal conductivity presented here are numerically verified.
Numerical Calculation of Heat Transfer Coefficient of Liquid Flow With NPCM in Microchannels
Authors: Hao Y. L. , Tao Y.-X.
Published: May 2010

A continuum model is applied to the numerical simulation of the laminar hydrodynamic and heat-transfer characteristics of suspension with nano phase change material (NPCM) particles in a microchannel. The analytical/numerical formulation based on CFD modeling technique, and the computer code is developed. Local wall-to-suspension heat transfer coefficients are calculated by the simultaneous solution of the conservation of mass, momentum and thermal energy equations. By providing detailed information on the local behavior of the wall-to-suspension heat transfer coefficients, preliminary calculations expose that there exists a particle-depleted layer next to the wall under the laminar flow condition. It plays an important role on the heat transfer between the suspension and the wall under the laminar flow condition. The main contribution of NPCM particles is the increase in the thermal capacity under the laminar flow condition. The qualitative comparison with the experimental observations and measurements on the flow and heat transfer of microencapsulated PCM slurry in circular duct indicates that the preliminary results are reasonable. It interprets the observation in the literature where heat transfer between the suspension and the wall is weaker than that between the pure fluid and the wall for laminar flow conditions.
On the Treatment of Circuit Boards as Thermal Two-Ports
Authors: Stout Roger P.
Published: May 2010

It is shown that a thin circuit board with a single heat source may be treated as a “two-port,” a concept borrowed from electrical network theory. In situations where a circuit board may be approximated by varying regions of roughly axisymmetric geometry, a cascaded two-port model may be easily constructed and solved analytically. Each axisymmetric segment of the model is a two-port (in thermal terms, a circular fin lacking the traditional adiabatic boundary condition at the outer radius), hence an arbitrarily complex (axisymmetric) board model is represented by a cascaded two-port network. The overall network is driven by a heat source at its inner radius, and some outer radius boundary condition; the two-port concept naturally separates the interior conduction and surface convection properties from the temperature and heat flux boundary conditions. Thus, using this scheme, temperature and heat flow may be easily determined at every position within the model, thus providing necessary information on the interactions between locations within the model — permitting yet more complex analyses of a circuit board as a multiple heat source system. Application of the axisymmetric two-port method is made to thermal characterization of semiconductor devices, including the relationship between so called “min pad” and “1-inch pad” device characteristics. The model is also compared to other experimental data, where the “best fit” of the model parameters shows a reasonable correlation with the expected physical values of the experiment.
Effects of Thermal Aging and Au Addition on the Electrical Resistance of Solder Balls in Flip Chip and Ultra-CSP Packages
Authors: Huang Xingjia , Lee S. W. Ricky , Li Ming , Chen William
Published: May 2010

The present study is aimed at investigating the effects of thermal aging and Au addition on the electrical resistance of solder balls (bumps) in flip chip (FC) and UltraCSP packages. The specimens include one FC with eutectic Sn-Ag-Cu solder bumps and two types of UltraCSP, which have 20-mil and 30-mil eutectic Sn-Pb solder balls, respectively. The thermal aging test is performed with thermal aging at 175°C for FC, and 150°C for CSPs for up to 2000 hours, respectively. The electrical resistance of each daisy-chain pair of solder balls is measured using the Four Point Kelvin Method. With the increase in thermal aging time, electrical resistance of CSPs without Au increases gradually. After 1000 hour, the resistance seems to level off. While the resistance of CSPs with Au addition ascends monotonically with prolonged thermal aging. For Sn-Ag-Cu flip chip solder bumps, at 175°C for only 24 hours, the electrical resistance of a daisy-chain pair of solder bumps drops substantially. From 24 to 2000 hours, the electrical resistance increases at first and soon becomes stable. The change in the electrical resistance is related to the microstructural evolution in the solder balls.
Influence of the Property of the Build-Up Package on Warpage at Flip Chip Assembly Process
Authors: Toyoda Yukihiko , Kawamura Yoichiro , Hiei Hiroyoshi , Yu Qiang , Shibutani Tadahiro , Kim Doseop , Nam Haeki
Published: May 2010

High density and integrated packaging of electronic device requires fine pitch. This packaging causes reliability problem in electronic device. One of them, warpage of the package occurred at chip assembly process may affect reliability. Therefore, if the simulation at the time of a chip assembly process is possible, it will be able to evaluate warpage in advance. It is very effective for development of a new product. Then, in this paper, the build-up package is regarded as a single material and the simulation technique of accuracy warpage at the time of chip assembly is reported. Next it is investigated the simulation technique for package warpage at the chip assembly process. Finnaly, it analyzed about the properties which affect warpage.
Design of a Low-Cost Infrared Sensor Array Through Thermal System Modeling
Authors: Smith Brian R. , Amon Cristina
Published: May 2010

The responsivity, sensitivity (signal-to-noise ratio), and cross talk of pyroelectric infrared sensor arrays are directly related to the thermal performance of the interconnect between sensor elements and readout electronics. Conventional low-cost designs, employing a film of sensor material like polyvinylidenefluoride (PDVF) layered on top of a silicon substrate, function by reading the electronic signal generated in the sensor when infrared radiation causes the sensor to heat up proportional to the radiation intensity. However, the change in temperature of the sensor material, and therefore signal generated, is highly dependent on the thermal properties of the interconnect material between the sensor and silicon substrate. A numerical framework for evaluating the effect of thermal conductivity and specific heat on sensor responsivity, sensitivity, and cross talk is developed. This allows us to analyze the relationships between feature size, thermal properties, and system performance. Using this model, a selection of materials from epoxies and other conventional solutions to emerging material systems such as nanoporous silica (aerogel) can be analyzed. Aerogel is most interesting since its thermal properties are 1–3 orders-of-magnitude better than conventional interconnect materials. Recent developments have also shown its compatibility with low-cost microelectronics fabrication and packaging techniques. The numerical model illustrates the potential of highly miniaturized pyroelectric infrared sensor arrays that have comparable performance at dramatically lower fabrication cost compared to conventional infrared sensor array technology.
Qualification and Reliability Testing of a Microchip Laser System for Space Applications
Authors: Wright M. W. , Franzen D. , Hemmati H. , Sandor M.
Published: May 2010

A compact microchip laser pumped by a single fiber coupled diode laser was developed for a scanning laser radar instrument called Laser Mapper (LAMP) to be used as a guidance and control sensor in future JPL/NASA missions [1]. The system involves commercial-off-the-shelf components that were packaged and qualified for space applications. In particular, the system has to meet a 5000 hour minimum life requirement on a LEO platform. This paper discusses the process being used and the results of the selection and qualification of a low cost prepackaged diode laser with a custom packaged microchip laser crystal. The environmental testing would be applicable to a variety of commercial photonic systems. The topics to be discussed include: • The selection of the diode pump laser; • Upscreening of commercial parts; • Qualification sampling tests including temperature cycling, vibration, outgassing; • Physical construction analysis. The testing requirements and screening flow to ensure the lifetime reliability will be presented. This was determined based on input from Telcordia standards that apply to optoelectronic systems used in the telecommunications industry but upgraded to account for the unique aspects of the devices, such as the high optical power. The key elements in packaging high power optoelectronic devices for harsh environments include managing the thermal loading through the expected spacecraft temperature extremes and addressing the die mounting, optical fiber coupling and jacket assembly. Each of these aspects will be discussed in light of the testing results.
Planar Waveguide: Utility in Amino Acid Detection
Authors: Wulfman David R. , Baas Tracey , McGlennen Ronald
Published: May 2010

A device for the detection of fluorescently labeled nucleic acid sequences immobilized or hybridized to the surface of a planar waveguide has been developed. The device described requires no image gathering or analysis utilities, nor any specially patterned waveguide surface for detection. The system consists of an excitation light source and a photo detector, filters for select fluorescent emissions and a standard glass microscope slide that functions as a planar waveguide (PWG) and assay substrate. The device can discriminate fluorescent DNA products hybridized to a glass based array as effectively as laser based reader instruments, and is a low cost system with a high potential for full automation. The system’s functional parameters are presented along with design schematics of current prototypes. Performance data is also presented showing test results comparable to pre-established fluorescence detection means. Future design goals are also discussed. It is concluded that as a component in telemedicine or other remote medical care strategies, the detection means presented can play a significant role in bringing molecular diagnosis and gene detection to arenas of medical care where it is currently unavailable.
Effects of A Rotated Chip Package on Mechanical and Thermal Performances
Authors: Jung Henry H. , Zhang Ron , Lee Eddie , Ankireddi Sai
Published: May 2010

In the industry, heatsinks have commonly been oriented on IC packages so that their plan outlines are edge-wise parallel to those of the package. However there are situations where a rotated orientation is preferable, wherein the plan outline of the package is not ‘aligned’ with that of the heatsink assembly — in other words a situation where the heatsink location/orientation remain unchanged while the package itself is rotated in-plane. Mechanical design considerations may drive the need for such a non-traditional orientation, since the rotated package is anticipated to have lower mechanical stress levels in the silicon than the non-rotated one under the same heatsink-induced clamping load. In this study we examine the impact of such package rotation(s) on both the junction temperature performance of CPU packages and the package-level clamp-load induced mechanical stresses. Results show that the stress reduction in the rotated package is in the range of 15% to 60%. The thermal analysis also demonstrates that the effects on the hot spot temperature with 45 degrees rotation is an increase of almost 2°C compared with the non-rotated die case. This increase in junction temperature is expected to be even higher with lower airflow as seen in typical computer systems. Thus it may be inferred that it is important to consider the effects of die rotation on package performances.
New Methodology for Mechanical Characterisation of Solders for IC Packaging
Authors: Toh Siew Lok , Chau Fook Siong , Lim Beng Kuan , Wong Ee Hua
Published: May 2010

This paper presents a new methodology for the mechanical characterisation of solders used in integrated circuit (IC) packages. The methodology is formulated on the basis of package-level solder joints (BGA packages) to properly account for the effects of microstructure and intermetallic compound distribution. The methodology is implemented on the lead-free Sn-3.5Ag solder. In the indentation tests, the lead-free solder is found to be sensitive to the applied strain rates as well as the thermal cycling conditions. Finite element analyses, together with the experimental results are used to extract the elastic modulus and the elastic-plastic constitutive relations. The methodology has shown that the extracted properties are in good agreement with other publications.
Electronic Packaging Education Through Internet: A Plan at Tohoku University and Some Challenges in Sight
Authors: Watanabe Ryuzo , Nakayama Wataru , Ishizuka Masaru , Maruyama Shigenao , Behnia Masud
Published: May 2010

In April 2002, Tohoku University, Sendai, Japan, started offering educational programs from the cross-department Internet School of Tohoku University (ISTU). Electronic packaging is one of the pillar subjects of ISTU. The present paper summarizes its curriculum of internet-based electronic packaging education. Following the overall description, the curriculum concerning thermal management of electronic equipment is explained in some detail. The ISTU program is still under development, and some challenges are foreseen. The most visible among them is the need to lower the cost of wide bandwidth communications. The future of internet schooling is discussed.
Co-Firing Technology for Buried Resistors
Authors: Yadagiri G. , Goswami K. K. , Gurumurthy K. S. , Satyam  , Shankara K. N.
Published: May 2010

The complexity and performance of the electronic components and systems is increasing and placing greater demands on compact packaging and interconnection technologies. Multilayer thick film technology is one of the important technologies adopted in the miniaturization of electronic systems. Normally only interconnections are made in the intermediate layers. The possibility of fabricating resistors along with interconnections in the intermediate layers using conventional thick film materials using co-firing process has been examined in this paper. Normally multilayer structures are fabricated by printing / drying / firing of each layer separately starting from the bottom most layer (sequential processing). In this process the bottom layers undergo sintering many times. To avoid many firing cycles and to save power and processing time, a study is taken up to examine the effects of co-firing on the multilayer structure with embedded resistors. The results of the study are presented in this paper.
Analysis of Interface Cracking in Flip Chip Packages With Viscoplastic Solder Deformation
Authors: Heffes M. J. , Nied H. F.
Published: May 2010

This paper examines the modeling of viscoplastic solder behavior in the vicinity of interfacial cracking for flip chip semiconductor packages. Of particular interest is the relationship between viscoplastic deformation in the solder bumps and any possible interface cracking between the epoxy underfill layer and the silicon die. A 3-D finite element code, developed specifically for the study of interfacial fracture problems, was modified to study how viscoplastic solder material properties would affect fracture parameters such as strain energy release rate and phase angle for nearby interfacial cracks. Simplified two-layer periodic symmetry models were developed to investigate these interactions. Comparison of flip chip results using different solder material models showed that viscoplastic models yielded lower stress and fracture parameters than time independent elastic-plastic simulations. It was also found that adding second level attachment greatly increases the magnitude of the solder strain and fracture parameters. As expected, the viscoplastic and temperature dependent elastic-plastic results exhibited greater similarity to each other than results based solely on linear elastic properties.
Modelling the Performance of Lead-Free Solder Interconnects for Copper Bumped Flip-Chip Devices
Authors: Lu Hua , Bailey Chris
Published: May 2010

Traditionally, before flip chips can be assembled the dies have to be attached with solder bumps. This process involves the deposition of metal layers on the Al pads on the dies and this is called the under bump metallurgy (UBM). In an alternative process, however, Copper (Cu) columns can be used to replace solder bumps and the UBM process may be omitted altogether. After the bumping process, the bumped dies can be assembled on to the printed circuit board (PCB) by using either solder or conductive adhesives. In this work, the reliability issues of flip chips with Cu column bumped dies have been studied. The flip chip lifetime associated with the solder fatigue failure has been modeled for a range of geometric parameters. The relative importance of these parameters is given and solder volume has been identified as the most important design parameter for long-term reliability. Another important problem that has been studied in this work is the dissolution of protection metals on the pad and Cu column in the reflow process. For small solder joints the amount of Cu which dissolves into the molten solder after the protection layers have worn out may significantly affect solder joint properties.
Development of Double Metal Bellows Air Pressure Spring With Lead Rubber Bearing Type 3-Dimensional Seismic Isolator
Authors: Nakamura Kyotada , Ogiso Seitaro , Suzuki Michiaki , Umeki K.
Published: May 2010

A new simple 3-dimensional seismic isolator concept for a commercial fast breeder reactor (FBR) building was proposed. The isolator consists of common reliable industrial parts, metallic bellows and lead rubber bearing (LRB). Air pressurized metallic bellows is for vertical isolation and LRB is for horizontal. The isolation frequencies are 0.5Hz for horizontal and 0.56Hz for vertical respectively. The maximum vertical displacement to absorb is 400mm and the vertical load of 9807kN should be supported per each isolator. A conceptual design was performed for these design requirements and a scale model test was carried out to confirm the feasibility of the concept.
Study on Limits of Height-to-Width Ratio for Base Isolated Buildings Under Earthquake
Authors: Li Hong-Nan , Wu Xiang-Xiang
Published: May 2010

The limit of height-to-width ratio (HWR) for base-isolated building with the elastomeric rubber bearings is of considerable concern to structural design engineers. And guidelines and codes on this building in the world have to deal with this issue. Nevertheless, until now, no systematical and quantitative study has been done on this problem for the base-isolated buildings. For this reason, the main objective of this paper is to focus on investigations on the limit of the HWR for isolated building with the rubber bearings under different conditions subjected to earthquake excitations. The simplified formulation is derived and some influenced factors, such as the site soil conditions, seismic ground motion intensity, period of the isolated system, period of the superstructure and layout of isolators, are studied and discussed. According to the numerical results, it has been found that the effects of site soil conditions on the HWR limit values are important, in which the softer the site is, the smaller the HWR limit value is under different seismic intensities; the predominant period of isolated building also plays a considerable role in the HWR limit value, namely, the isolated building with a longer period may have a relatively large HWR value; and the stiffness of superstructure affects the HWR limit value little. Furthermore, an effective method to improve the HWR limit value is proposed.
Dynamic Characteristics of a Hydraulic Damper
Authors: Verma Vishnu , Ghosh A. K. , Kushwaha H. S.
Published: May 2010

The response of a structure to earthquake or any other dynamic excitation can be brought down by using a suitable damper such as a hydraulic damper. An analytical model has been developed for hydraulic damper, which consists of a cylinder and piston arrangement with a bypass pipeline. The stiffness of the system is primarily due to the compressibility of the fluid and the damping is largely due to the pressure drop in the bypass line. The dynamic response of the hydraulic damper has been evaluated for an assumed sinusoidal motion of the piston. The paper presents detailed results of the study of the dynamic response of the damper to variations in input and system parameters. The characteristics of the damper, thus obtained, will be useful in determining the dynamic response of the whole system to which this damper will be attached.
A Study of an Arm Type Damper Consisting of Two Links, Two Joints and a Hinge
Authors: Matsuoka Taichi , Omata Kenichiro , Okano Yasuhisa
Published: May 2010

In this paper, an arm type passive damper consisting of two links, two joints and a hinge, which is similar to a human arm, has developed. Two magnetic ball joints were used for the joints and a rotary friction damper was used for the hinge. The arm type damper has six degrees of freedom and gives damping in three translational and three rotational directions. The resisting force characteristics of the damper in three translational directions were analyzed. A trial damper was made and the load-displacement curves of the damper in three translational directions were measured. The experimental results agree with the theoretical results to some degree. Next, the damper was attached to a three-degree-of-freedom system composed of a mass, three guide rails and four coil springs, in which the mass is able to move in three translational directions along the guide rails. The seismic responses of the mass in three translational directions were measured using a two-dimensional electrohydraulic type shaking table and the experimental results were compared with the calculated results obtained by the Mathematica 3.0. The experimental results agree with the calculated results to some degree, and the effects of vibration suppression of the damper and the propriety of the calculations were substantiated.
Design and Analysis of Viscoelastic Seismic Dampers
Authors: Shimizu N. , Nasuno H. , Yazaki T. , Sunakoda K.
Published: May 2010

This paper describes a methodology of design and analysis of viscoelastic seismic dampers by means of the time domain finite element analysis. The viscoelastic constitutive relation of material incorporating with the fractional calculus has been derived and the finite element formulation based on the constitutive relation has been developed to analyze the dynamic property of seismic damper. A time domain computer program was developed by using the formulation. Dynamic properties of hysteresis loop, damping capacity, equivalent viscous damping coefficient, and equivalent spring constant are calculated and compared with the experimental results. Remarkable correlation between the FE analysis and the experiment is gained, and consequently the design procedure with the help of the FE analysis has been established.
Stochastic Analysis of Sensitivity and Efficiency of Base Isolation System in Seismic Structural Protection
Authors: Dipaola Vincenzo , Marano Giuseppe Carlo , Greco Rita
Published: May 2010

In this research the seismic response of structures isolated at the base by means of High Damping Laminated Rubber Bearings (HDRB) is evaluated. The analysis is performed by using a stochastic approach and a Gaussian zero mean non stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. In order to take into account of the non-linear constitutive behavior both of the base isolation device and of the structure, the hysteretic differential Bouc-Wen model (BWM) is adopted. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non-linear system response in the state space. After estimating the system response variance a sensitivity analysis is carried out. The final aim of the research is to asses the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non-linear response with associated large plastic displacements, and, therefore, by limiting related damage phenomena in structural and non structural members. In order to achieve this objective the stochastic response of a non-linear n-dof shear-type base isolated building is analyzed. The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy.
An Improved FPS Isolator for Seismic Mitigation on Steel Structure
Authors: Tsai C. S. , Chiang Tsu-Cheng , Cheng Chia-Kuan , Chen Wen-Shin , Chang Chih-Wei
Published: May 2010

Structure equipped with base isolators to decouple the superstructure from its foundation has been recognized as an effective and feasible way to mitigate structural response subjected to seismic loadings. In this study, a new lubricant material for the FPS isolator has been developed. The experimental results from shaking table tests show that the acceleration responses of floors of a structure isolated by the FPS isolators coated with the new Teflon composite can be lessened within a desirable range, and the steel structure with the FPS isolators moves nearly as rigid body motions during earthquakes. To verify the durability of the FPS isolators, the component tests of sliding interface coated with advanced Teflon composite and shaking table tests of steel structure with the FPS isolators subjected to hundreds of earthquake events were performed in this study. The experimental results demonstrate that the advanced Teflon composite can sustain hundreds of reversal loadings, therefore, it can be adopted to lubricate the sliding interface of the FPS isolators. Furthermore, a simplified and a finite element formulation for bilateral-spherical-surface-type FPS have been proposed in this study. The numerical results show that the proposed formulation can well predict the dynamic response of structure with bilateral-spherical-surface-type FPS than the formulation proposed by S. Okamura et at.
ZnxNi1-xO Mixed-Metal Oxides by XPS and Auger
Authors: Gaskell Karen J. , Starace Anne , Langell Marjorie A.
Published: May 2010

ZnxNi1-xO samples with a compositional range 0 < × ≤ 0.3 were synthesized via thermal dissolution in air and their surface characterized with x-ray photoelectron spectroscopy (XPS). XPS analysis shows the surface composition to be comparable to the bulk composition. These systems are interesting as they place zinc in an octahedral environment which is unusual for zinc normally preferring a tetrahedral environment. Auger parameter analysis further illustrates this unusual environment yielding a zinc Auger parameter equal to ∼2011 eV, more than 1 eV greater than found for zinc oxide in the wurtzite form, also in the +2 oxidation state. This submission contains the core level and survey spectra for the homogeneous solid solutions, Zn0.05Ni0.95O, Zn0.1Ni0.9O, Zn0.2Ni0.8O, Zn0.3Ni0.7O and for pure NiO and ZnO. All samples have the rocksalt crystal structure except ZnO which has the wurtzite crystal structure.
Sound scattering from two concentric fluid spheres
Authors: McNew Jared , Lavarello Roberto , O’Brien William D.
Published: May 2010

The solution to the problem of plane wave and point source scattering by two concentric fluid spheres is derived. The effect of differences in sound speed, density, and absorption coefficient is taken into account. The scattered field is then found in the limit as the outer sphere becomes an infinitely thin shell and compared to the solution for a single fluid sphere for verification. A simulation is then performed using the concentric fluid sphere solution as an approximation to the human head and compared to the solution of a single fluid sphere with the properties of either bone or water. The solutions were found to be similar outside of the spheres but differ significantly inside the spheres.
Three Historic Blowouts
Authors: Schenkman Lauren
Published: May 2010

The decade from 1969 to 1979 witnessed three massive spills from offshore oil wells around the world.
Science
compares their size and impact.
Close Encounters of the Prehistoric Kind
Authors: Gibbons Ann
Published: May 2010

The long-awaited sequence of the Neandertal genome suggests that modern humans and Neandertals interbred tens of thousands of years ago, perhaps in the Middle East.
Cloned Neandertals Still in the Realm of Sci-Fi
Authors: Pennisi Elizabeth
Published: May 2010

Since the idea of sequencing the Neandertal genome became more than a glimmer in a paleogeneticist's eye, some have asked, "Could we, should we, would we, bring this extinct human species back to life?" But for both technical and ethical reasons, experts say, bringing back a Neandertal is a pipe dream.
Levels of Antibody against 11
Staphylococcus aureus
Antigens in a Healthy Population
Authors: Colque-Navarro Patricia , Jacobsson Gunnar , Andersson Rune , Flock Jan-Ingmar , Möllby Roland
Published: May 2010

Serum samples from 151 healthy individuals aged from 15 to 89 years were investigated by enzyme-linked immunosorbent assay (ELISA) for IgG levels against 11 different purified antigens from
Staphylococcus aureus.
Surface antigens, such as teichoic acid, clumping factors A and B, and bone sialoprotein binding protein, and extracellular proteins, such as alpha-toxin, lipase, enterotoxin A, toxic shock syndrome toxin, scalded-skin syndrome toxin, fibrinogen binding protein, and extracellular adherence protein, were used. The IgG values were analyzed in relation to the state of nasal carriage at the time of sampling. There was great individual variation in antibody levels in both young and elderly healthy subjects. Occurrence of
S. aureus
in the nares at the time of sampling was correlated with higher antibody levels, while elderly individuals over 65 years of age showed slightly lower levels than younger adults. More individuals than was expected from random probability calculations showed high antibody levels against several antigens, and more individuals than would be expected showed low levels against several antigens. Certain extracellular proteins had more often induced IgG levels of the same magnitude in the same individuals, indicating that among these individuals, there was a tendency to respond to certain antigens in the same way. Most individuals had circulating IgG antibodies to the 11 tested antigens, and some individuals had the tendency to be “good responders” to several antigens, while others were “poor responders.” These findings constitute basic knowledge for the development of improved serological diagnostics, immune prophylaxis, individual prognosis tools, and therapy against invasive
Staphylococcus aureus
infections.
Genetic Characterization of Genogroup I Norovirus in Outbreaks of Gastroenteritis
Authors: Xerry Jacqueline , Gallimore Chris I. , Iturriza-Gómara Miren , Gray Jim J.
Published: May 2010

In this study, we demonstrate that differences within the P2 domain of norovirus genogroup I (GI) strains can be used to segregate outbreaks which are unrelated, whereas complete conservation within this region allows tracking of strains that are part of a single outbreak and likely to have a common source.
Inefficient Control of Host Gene Expression by the 2009 Pandemic H1N1 Influenza A Virus NS1 Protein
Authors: Hale Benjamin G. , Steel John , Medina Rafael A. , Manicassamy Balaji , Ye Jianqiang , Hickman Danielle , Hai Rong , Schmolke Mirco , Lowen Anice C. , Perez Daniel R. , García-Sastre Adolfo
Published: May 2010

In 2009, a novel swine-origin H1N1 influenza A virus emerged. Here, we characterize the multifunctional NS1 protein of this human pandemic virus in order to understand factors that may contribute to replication efficiency or pathogenicity. Although the 2009 H1N1 virus NS1 protein (2009/NS1) is an effective interferon antagonist, we found that this NS1 (unlike those of previous human-adapted influenza A viruses) is unable to block general host gene expression in human or swine cells. This property could be restored in 2009/NS1 by replacing R108, E125, and G189 with residues corresponding to human virus consensus. Mechanistically, these previously undescribed mutations acted by increasing binding of 2009/NS1 to the cellular pre-mRNA processing protein CPSF30. A recombinant 2009 H1N1 influenza A virus (A/California/04/09) expressing NS1 with these gain-of-function substitutions was more efficient than the wild type at antagonizing host innate immune responses in primary human epithelial cells. However, such mutations had no significant effect on virus replication in either human or swine tissue culture substrates. Surprisingly, in a mouse model of pathogenicity, the mutant virus appeared to cause less morbidity, and was cleared faster, than the wild type. The mutant virus also demonstrated reduced titers in the upper respiratory tracts of ferrets; however, contact and aerosol transmissibility of the virus was unaffected. Our data highlight a potential human adaptation of NS1 that seems absent in “classically derived” swine-origin influenza A viruses, including the 2009 H1N1 virus. We discuss the impact that a natural future gain of this NS1 function may have on the new pandemic virus in humans.
Ancient Adaptive Evolution of Tetherin Shaped the Functions of Vpu and Nef in Human Immunodeficiency Virus and Primate Lentiviruses
Authors: Lim Efrem S. , Malik Harmit S. , Emerman Michael
Published: May 2010

Tetherin/BST-2 is a host-encoded protein that restricts a wide diversity of viruses at the stage of virion release. However, viruses have evolved antagonists of Tetherin, including the Vpu and Nef proteins of primate lentiviruses. Like other host genes subject to viral antagonism, primate Tetherin genes have evolved under positive selection. We show here that viral antagonists acting at three independent sites of selection have driven the evolution of Tetherin, with the strongest selective pressure on the cytoplasmic tail domain. Human Tetherin is unique among the Tetherins of simian primates in that it has a 5-amino-acid deletion that results in the loss of the residue under the strongest positive selection. We show that this residue at amino acid 17 is the site of the functional interaction of Tetherin with Nef, since single amino acid substitutions at this single position can determine the susceptibility of Tetherin to Nef antagonism. While the simian immunodeficiency viruses SIVcpz and SIVgor are able to antagonize their hosts' Tetherin with Nef, human immunodeficiency virus type 1 (HIV-1) Vpu has evolved to counteract Tetherin in humans. We mapped the adaptations in the N-terminal transmembrane domain of Vpu that allow it to counteract human Tetherin. Our combined evolutionary and functional studies have allowed us to reconstruct the host-pathogen interactions that have shaped Tetherin and its lentivirus-encoded antagonists.
Processing of Lagging-Strand Intermediates
In Vitro
by Herpes Simplex Virus Type 1 DNA Polymerase
Authors: Zhu Yali , Wu Zetang , Cardoso M. Cristina , Parris Deborah S.
Published: May 2010

The processing of lagging-strand intermediates has not been demonstrated
in vitro
for herpes simplex virus type 1 (HSV-1). Human flap endonuclease-1 (Fen-1) was examined for its ability to produce ligatable products with model lagging-strand intermediates in the presence of the wild-type or exonuclease-deficient (exo
−
) HSV-1 DNA polymerase (pol). Primer/templates were composed of a minicircle single-stranded DNA template annealed to primers that contained 5′ DNA flaps or 5′ annealed DNA or RNA sequences. Gapped DNA primer/templates were extended but not significantly strand displaced by the wild-type HSV-1 pol, although significant strand displacement was observed with exo
−
HSV-1 pol. Nevertheless, the incubation of primer/templates containing 5′ flaps with either wild-type or exo
−
HSV-1 pol and Fen-1 led to the efficient production of nicks that could be sealed with DNA ligase I. Both polymerases stimulated the nick translation activity of Fen-1 on DNA- or RNA-containing primer/templates, indicating that the activities were coordinated. Further evidence for Fen-1 involvement in HSV-1 DNA synthesis is suggested by the ability of a transiently expressed green fluorescent protein fusion with Fen-1 to accumulate in viral DNA replication compartments in infected cells and by the ability of endogenous Fen-1 to coimmunoprecipitate with an essential viral DNA replication protein in HSV-1-infected cells.