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Experimental and finite element analysis on determining the fatigue life of pb-free solder joint(Sn-0.5Cu-3Bi-1Ag)used in electronic packages under harmonic loads

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International Journal of modeling, Simulation, and Scientific Computing 2020年第3期11卷 60-67页

作者： Jayesh S jacob Elias Department of mechanical Engineering School of Engineering Cochin University of Science and Technology KochiKerala-682022India

Electronic packages that are used these days are exposed to different types of vibration loadings in their usage *** vibration exposure can be categorized as harmonic and random *** reliability assessment of modern electronic systems is considered,vibration loading has an important role to *** of the biggest challenges facing today is the accurate and rapid assessment of fatigue life under the vibration *** solder joints were made of lead-tin *** to many environment legislations and rules,lead is prohibited as an ingredient in the solder *** reason for the prohibition of the usage of the lead is that it poisons the *** this study,Sn-0.5Cu-3Bi-1Ag is used as the lead-free solder *** life prediction of electronic package containing SAC405 is conducted with the aid of vibration testing and Finite element analysis under harmonic vibration loading.A specially designed Plastic Ball Grid Array Package(PBGA)component is mounted on Printed Circuit Board(PCB).It is taken as a test vehicle for the vibration *** test vehicle is excited by a sinusoidal *** frequency of this excitation equals the fundamental frequency of the test vehicle and it is continued till the component *** the solder balls are very small for direct measurement,Finite Element analysis(FEA)is used for noting down the *** stress versus failures cycles(S-N)curve is made by relating both the stresses on the solder balls obtained and the number of failure cycles from vibration *** fatigue life of the component can be estimated from the generated S-N *** is analyzed that the methodology is effective in predicting the component’s ***,the reliability of electronic package can be improved.

关键词： PCB lead free solder joint FEA PBGA S-N curve

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An Iterative Pose Estimation Algorithm Based on Epipolar Geometry With Application to multi-Target Tracking

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IEEE/CAA Journal of Automatica Sinica 2020年第4期7卷 942-953页

作者： jacob H.White Randal W.Beard the Brigham Young University ProvoUtah 84058 USA

This paper introduces a new algorithm for estimating the relative pose of a moving camera using consecutive frames of a video sequence. State-of-the-art algorithms for calculating the relative pose between two images use matching features to estimate the essential matrix. The essential matrix is then decomposed into the relative rotation and normalized translation between frames. To be robust to noise and feature match outliers, these methods generate a large number of essential matrix hypotheses from randomly selected minimal subsets of feature pairs, and then score these hypotheses on all feature pairs. Alternatively, the algorithm introduced in this paper calculates relative pose hypotheses by directly optimizing the rotation and normalized translation between frames, rather than calculating the essential matrix and then performing the decomposition. The resulting algorithm improves computation time by an order of magnitude. If an inertial measurement unit(ImU) is available, it is used to seed the optimizer, and in addition, we reuse the best hypothesis at each iteration to seed the optimizer thereby reducing the number of relative pose hypotheses that must be generated and scored. These advantages greatly speed up performance and enable the algorithm to run in real-time on low cost embedded hardware. We show application of our algorithm to visual multi-target tracking(mTT) in the presence of parallax and demonstrate its real-time performance on a 640 × 480 video sequence captured on a UAV. Video results are available at https://***/Hh K-p2 h XNn U.

关键词： Aerial robotics epipolar geometry multi-target tracking pose estimation unmanned aircraft systems vision-based flight

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microwave ablation of hepatocellular carcinomas in octogenarians

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Hepatoma Research 2020年第3期6卷 24-30页

作者： jacob Freedman Department of Surgery and Urology Danderyd University HospitalStockholm 18288Sweden Department of clinical sciences Karolinska InstitutetStockholm 18288Sweden

Aim:To evaluate wether it is safe and meaningful to treat octogenarians with microwave ablation for hepatocellular *** an ageing population being healthier than previous generations,old limits for treating disease founded on patient age need to be *** of the most common tumour related death causes is hepatocellular carcinoma(HCC).With the development of minimally invasive therapies with curative potential,new ground is being broken offering treatments to older patients in the hope of achieving prolongation and better quality of ***:In this retrospective single centre study of patients having a first microwave ablation therapy for HCC in a national referral centre for ablative liver treatments,septuagenarians(n=161,age 70-80)were compared with octogenarians(n=32,age 80-90).Results:Octogenarians selected for microwave ablation of HCC at a regional multidisciplinary team conference have similar outcomes as their younger control ***,complications and length of stay are not ***:Octogenarians who are fit for ablative treatment of HCC should not be disqualified on grounds of age,recognising that this group has an obvious immortality,or lead-time,bias as well as a probable selection bias in part explaining their good results.

关键词： microwave ablation hepatocellular carcinoma octogenarians survival complications

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The Epigenetic Reprogramming Roadmap in Generation of iPSCs from Somatic Cells

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Journal of Genetics and Genomics 2015年第12期42卷 661-670页

作者： jacob Brix Yan Zhou Yonglun Luo Department of Biomedicine Aarhus University

Reprogramming of somatic cells to induced pluripotent stem cells （iPSCs） is a comprehensive epigenetic process involving genome-wide modifications of histones and DNA methylation. This process is often incomplete, which subsequently affects iPSC reprograming, pluripotency, and differentiation capacity. Here, we review the epigenetic changes with a focus on histone modification （methylation and acetylation） and DNA modification （methylation） during iPSC induction. We look at changes in specific epigenetic signatures, aberrations and epigenetic memory during reprogramming and small molecules influencing the epigenetic reprogramming of somatic cells. Finally, we discuss how to improve iPSC generation and pluripotency through epigenetic manipulations.

关键词： Induced pluripotent stem cells (iPSCs) Reprogramming Epigenetics Histone modification DNA methylation Epigenetic memory

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Towards an L^p Potential Theory for Sub-markovian Semigroups:Kernels and Capacities

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Acta mathematica Sinica,English Series 2006年第4期22卷 1227-1250页

作者： Niels jacob RenéL.SCHILLING Department of mathematics University of Wales SwanseaSingleton ParkSwansea SA 2 8 PP.United Kinadom FB 12-mathematik Philipps-Universitat MarburgD-35032 MarburgGermany

We study in fairly general measure spaces （X,μ） the （non-linear） potential theory of L^p sub-markovian semigroups which are given by kernels having a density with respect to the underlying measure. In terms of mapping properties of the operators we provide sufficient conditions for the existence （and regularity） of such densities. We give various （dual） representations for several associated capacities and, in the corresponding abstract Bessel potential spaces, we study the role of the truncation property. Examples are discussed in the case of R^n where abstract Bessel potential spaces can be identified with concrete function spaces.

关键词： nonlinear potential theory (r,p)-capacity Bessel potential space gamma.transform sub-markovian semigroup

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The impact of seasonality on multi-scale feature extraction techniques

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International Journal of Digital Earth 2020年第1期13卷 9-21页

作者： Brian moore jacob J.mcKee Geographic Information Science and Technology Group Computational Sciences and Engineering DivisionOak Ridge National LaboratoryOak RidgeTNUSA

A key component in constructing a broad-scale,gridded population dataset is fine resolution geospatial data accurately depicting the extent of human *** datasets are often developed using a wide range of methods and classification techniques,including the use of spatial features,spectral features,or the coupling of both to identify the presence of man-made structures from high-resolution satellite *** using spatial and textural-based descriptors to generate highresolution settlement layers for two dissimilar regions at the peak of seasonal disparity,this study attempts to quantify the influence of seasonality on the accuracy of a supervised,multi-scale,feature extraction framework for automated delineation of human *** generated by numerous models are evaluated against a reference dataset allowing for assessment of seasonal and feature differences in the context of *** or regional mapping of human settlement requires the assemblage of high-resolution satellite images with variegated acquisition characteristics(season,sun elevation,off-nadir,etc.)to produce a cloud-free composite image from which features are *** of this study suggest an emphasis on imagery criteria,in particular acquisition date,could improve classification accuracy when mapping human settlement at scale.

关键词： Remote sensing highresolution imagery image processing human settlement accuracy

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亲缘选择在植物从营养分配向繁殖分配转变中的潜在作用

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Journal of Plant Ecology 2023年第6期16卷 135-145页

作者： Renfei Chen Cenxi Shi Liang Zhang Chengyi Tu jacob Weiner School of Life Science Shanxi Normal UniversityTaiyuan 030000China State Key Laboratory of Grassland Agro-Ecosystem School of Life SciencesLanzhou UniversityLanzhou 730000China School of Economics and management Zhejiang Sci-Tech UniversityHangzhou 310000China Department of Environmental Science Policyand ManagementUniversity of CaliforniaBerkeleyCA 94720USA Department of Plant and Environmental Sciences University of CopenhagenDK-1871 FrederiksbergDenmark

根据经典的最优繁殖分配理论,植物生长过程中从营养生长向繁殖分配的转变是突然发生的。一些植物确实如此,这也是农作物产量最大化的一种有效策略。然而,自然界很多植物从营养生长向繁殖分配的转变是渐进发生的。一些修正的生物量分配... 详细信息

根据经典的最优繁殖分配理论,植物生长过程中从营养生长向繁殖分配的转变是突然发生的。一些植物确实如此,这也是农作物产量最大化的一种有效策略。然而,自然界很多植物从营养生长向繁殖分配的转变是渐进发生的。一些修正的生物量分配理论也预测了这种渐变趋势。本研究假设亲缘选择能够改变最优分配理论的预测。通过数学模型,我们研究了正负亲缘选择对植物向繁殖器官分配能量起始时间的影响。基于代价与收益的合理假设,当繁殖器官与营养器官起始生物量比值较高时,处于亲缘选择作用下的植物更可能以一种突变的方式实现从营养生长向繁殖生长的转变。经验数据的观测支持我们的理论预测。这一研究在连接植物生活史与能量分配以及提高农业产量方面具有重要意义。

关键词：广义适合度资源分配繁殖器官营养生长繁殖分配进程

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Enhancing accessibility to web mapping systems with technology-aligned adaptive profiles

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International Journal of Digital Earth 2014年第4期7卷 256-278页

作者： jacob Delfos Bert Veenendaal Tele Tan Department of Spatial Sciences Curtin UniversityPerthWAAustralia Department of Computing Curtin UniversityPerthWAAustralia

Web-based geographic information systems have advanced rapidly on the back of web-based technologies,increased bandwidths and access to Digital Earth imagery and ***,these advances are causing its capabilities to slowly overtake those of ***,the introduction of non-desktop devices such as smartphones,tablets and netbooks is starting to undo progress made towards standardisation of web-based *** varia-tions in screen sizes,computational power,bandwidth,and operating environ-ments are once again introducing the need to ensure software remains functional across different platforms,standards-compliant or *** two issues highlight the need for a mechanism to tune content and capability to end-users and their environment,to prevent information and complexity overload in a field already troubled by poor usability,while promoting cross-platform *** paper proposes the use of adaptivity to accommodate for users from different backgrounds accessing web mapping systems in different technical *** describes adaptive profiles aligned to the finite number of states a system can adopt,rather than the limitless range of user or environment characteristics that cannot be adapted *** profile consists of a combination of adaptive states comprising functionality,information detail,or technical demands to optimise for individual users or technical environments.

关键词： web mapping digital earth adaptivity usability compatibility user modelling

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Evaluation of the 20 L dust explosibility testing chamber and comparison to a modified 38 L vessel for underground coal

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International Journal of mining Science and Technology 2018年第6期28卷 885-890页

作者： Robert Eades Kyle Perry Catherine Johnson jacob miller Department of mining and Nuclear Engineering Missouri University of Science and Technology

The phenomenon of combustible dust explosions is present within many industries. Tests for explosibility of dust clouds per ASTm E1226 use a 20 L explosive chamber that places the combustible dust directly below the dispersion nozzle which generates a thorough mixture for testing purposes. However, in the underground coal mining industry, there are a number of geologic, mining, and regulatory factors that change the deposition scheme of combustible coal dust. This causes the atmosphere of a coal mine to have a variable rock dust-coal dust mixture at the time of ignition. To investigate the impact of this variable atmosphere, a series of lean explosibility tests were conducted on a sample of Pittsburgh Pulverized coal dust. These explosibility tests were conducted in a 38 L chamber with a 5 kJ Sobbe igniter. The 38 L chamber generates a variable air-dust mixture prior to ignition. The test results indicate that the 38 L chamber experiences reduced explosive pressures, and lower explosibility index values when compared to the 20 L chamber.

关键词： Dust explosion Coal mining Coal dust Explosibility testing

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Resonant Raman scattering in GaN single crystals and GaN-based heterostructures: feasibility for laser cooling

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Chinese Optics Letters 2013年第1期11卷 63-71页

作者： Yujie J. Ding jacob B. Khurgin Department of Electrical and Computer Engineering Lehigh University Department of Electrical and Computer Engineering The Johns Hopkins University

The recent progress on Raman scattering in GaN single crystals and GaN/A1N heterostructures is re- viewed. Anti-Stokes Raman scattering is used to determine electron-phonon scattering time and decay time constant for longitudinal-opticat phonons. In a typical high electron mobility transistor based on GaN/A1N heterostructures, strong resonances are reached for the first-order and second-order Raman scattering processes. Therefore, both Stokes and anti-Stokes Raman intensities are dramatically enhanced. The feasibility for laser cooling of a nitride structure is studied. A further optimization will enable us to reach the threshold for laser cooling. Raman scattering have potential applications in up-conversion lasers and laser cooling of nitride ultrafast electronic and optoelectronic devices.

关键词： GaN Ra Resonant Raman scattering in GaN single crystals and GaN-based heterostructures feasibility for laser cooling

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