Automatic generation of boundary conditions using demons nonrigid image registration for use in 3-D modality-independent elastography

Modality-independent elastography (MIE) is a method of elastography that reconstructs the elastic properties of tissue using images acquired under different loading conditions and a biomechanical model. Boundary conditions are a critical input to the algorithm and are often determined by time-consuming point correspondence methods requiring manual user input. This study presents a novel method of automatically generating boundary conditions by nonrigidly registering two image sets with a demons diffusion-based registration algorithm. The use of this method was successfully performed in silico using magnetic resonance and X-ray-computed tomography image data with known boundary conditions. These preliminary results produced boundary conditions with an accuracy of up to 80% compared to the known conditions. Demons-based boundary conditions were utilized within a 3-D MIE reconstruction to determine an elasticity contrast ratio between tumor and normal tissue. Two phantom experiments were then conducted to further test the accuracy of the demons boundary conditions and the MIE reconstruction arising from the use of these conditions. Preliminary results show a reasonable characterization of the material properties on this first attempt and a significant improvement in the automation level and viability of the method.     

Fretting in copper-to-copper contacts under AC and DC currentconditions

The effect of fretting on the contact resistance behavior of copper-to-copper wire-plate combinations under AC and DC current carrying conditions was investigated. The fretting conditions were as follows: frequency 1 Hz, slip amplitude 100 μm and load 400 g (4N). The current level in both AC and DC conditions was 50 mA. In addition to contact resistance measurements, SEM and EDX were used to examine the surface damage in the fretted contact zones. The results indicate that the overall contact resistance behavior of copper-to-copper wire-plate couples subjected to the same fretting conditions but under AC and DC currents was practically the same. The characteristic feature of the samples under AC current conditions is a pronounced distortion of the waveforms of the contact voltage. The results of SEM surface analysis of the contact zones indicates that the surface damage resulting from fretting under AC current conditions was different from that under DC current conditions     

Reliability Modeling & Evaluation for Networks under Multiple & Fluctuating Operational Conditions

A simple multistate Markov process models a component and a system of any configuration under several operational conditions. Based on it, a simple tie-set approach calculates availability and frequencies-of-system-failure during different conditions; a cut-set approach calculates probabilities and frequencies of system-failure during various conditions. There are two interpretations of operational conditions: 1) environment such as weather or stress, and 2) operating conditions such as occur in several sequential or fluctuating phases. As the system is assumed at any moment under a condition with a certain probability or weight, some relative reliability measures can be further obtained simply to identify which conditions are disastrous.     

The reciprocity and power conservation principles for boundaryconditions on a semitransparent surface

Generalized boundary conditions of coupling on a semitransparent surface are valid only if the Lorentz reciprocity theorem and the electromagnetic power conservation principle are satisfied on the surface with these boundary conditions. These criteria are reformulated as relations between the tensors in the boundary conditions. Some known boundary conditions of coupling are considered     

锌蒸气高温气相氧化对氧化锌的结晶形貌的影响

实验研究了锌蒸气高温气相氧化条件对氧化锌结晶形貌的影响以及形貌变化的规律。研究表明氧化锌有无定形、颗粒状、单针状、四针状、多针状等五种典型的结晶形貌,这些结晶形貌都强烈地依赖于锌蒸气氧化时的物理化学环境,生长条件不同,ZnO晶体的成核和生长过程就不同,因而表现出不同的形貌,通过改变制备条件可以调控氧化锌的结晶形貌。实验同时表明氧化锌的结晶形貌与原料锌粉的粒度及表面状态没有直接联系。     

产生MD5碰撞的新的充分条件集

Wang Xiaoyun等(2005)给出了MD5能产生碰撞的一个充分条件集,并首次成功对MD5进行了碰撞攻击。Yuto Nakano等(2006)指出上述充分条件集中有16个条件是冗余的,并给出了其中14个条件冗余的原因。Liang Jie和Lai Xuejia(2005)指出Wang Xiaoyun等给出的充分条件集并非总能产生碰撞,并增加新的条件使之总能产生碰撞,同时提出了一个新的碰撞攻击算法。本文证明了Yuto Nakano等给出的16个冗余条件中有两个并不冗余,且Liang Jie和Lai Xuejia增加的新条件中有两个是冗余的,指出Liang Jie和Lai Xuejia的碰撞攻击算法在消息修改时忽视了被修改条件之间的制约性,因而未必总能产生碰撞,本文对此进行了修正,给出新的充分条件集,并通过实验验证了该充分条件集总能产生碰撞。     

国内地域差异和供电条件对液晶电视设计的影响

介绍了新版GB8898-2011针对我国的地理条件、气候条件和供电条件的复杂情况新增加的一些主要的要求,以及对电视机安全设计的影响和应该注意的问题。     

电子产品可靠性的云模型评价方法

传统的可靠性评价方法一般限定产品工作于一个或几个典型的不变的条件下,对工作条件可变的情况,目前尚缺少有效的方法。本文采用云模型,通过对定性的环境因素语言描述进行定量不确定转换,建立产品的环境适应性模型和工作条件模型,反映工作条件的改变对产品寿命的影响,并在此基础上,提出了考虑可变工作条件影响的电子产品可靠性评价方法,解决了可变工作条件下电子产品的可靠性问题。     

Sufficient Conditions for Convergence of the Sum–Product Algorithm

Novel conditions are derived that guarantee convergence of the Sum-Product Algorithm (also known as Loopy Belief Propagation or simply Belief Propagation (BP)) to a unique fixed point, irrespective of the initial messages, for parallel (synchronous) updates. The computational complexity of the conditions is polynomial in the number of variables. In contrast with previously existing conditions, our results are directly applicable to arbitrary factor graphs (with discrete variables) and are shown to be valid also in the case of factors containing zeros, under some additional conditions. The conditions are compared with existing ones, numerically and, if possible, analytically. For binary variables with pairwise interactions, sufficient conditions are derived that take into account local evidence (i.e., single-variable factors) and the type of pair interactions (attractive or repulsive). It is shown empirically that this bound outperforms existing bounds.      

印制电路板低气压条件下的耐电压测试

文章简要介绍了低气压条件下对一组印制电路板(PCB)实验样品的耐电压测试情况,总结了在低气压条件下印制板的耐压性能与气压、温度条件的内在关系。     

Hazard-Based Detection Conditions for Improved Transition Fault Coverage of Scan-Based Tests

We define a new type of detection conditions for delay faults, referred to as hazard-based detection conditions, to enhance the coverage of delay faults using the standard scan test application methods. Some delay faults, including irredundant faults, may be undetectable under the conventional detection conditions. These faults may be detectable under the hazard-based detection conditions. The use of hazard-based detection conditions thus improves the delay fault coverage achievable for a circuit. We consider transition faults under standard scan for the study in this paper.      

Thermal Cycling Reliability of Sn-Ag-Cu Solder Interconnections—Part 2: Failure Mechanisms

Part 1 of this study focused on identifying the effects of (i) temperature difference (ΔT), (ii) lower dwell temperature and shorter dwell time, (iii) mean temperature, (iv) dwell time, and (v) ramp rate on the lifetime of ball grid array (with 144 solder balls) component boards. Based on the characteristic lifetime, the studied thermal cycling profiles were categorized into three groups: (i) highly accelerated conditions, (ii) moderately accelerated conditions, and (iii) mildly/nonaccelerated conditions. In this work, the observed differences in component board lifetime are explained by studying the failure mechanisms and microstructural changes that take place in the three groups of loading conditions. It was observed that, under the standardized thermal cycling conditions (highly accelerated conditions), the networks of grain boundaries formed by recrystallization provided favorable paths for cracks to propagate intergranularly. It is noteworthy that the coarsening of intermetallic particles was strong in the recrystallized regions (the cellular structure had disappeared completely in the crack region). However, under real-use conditions (mildly/nonaccelerated conditions), recrystallization was not observed in the solder interconnections and cracks had propagated transgranularly in the bulk solder or between the intermetallic compound (IMC) layer and the bulk solder. The real-use conditions showed slight coarsening of the microstructure close to the crack region, but the solder bulk still included finer IMC particles and β-Sn cells characteristic of the as-solidified microstructures. These findings suggest that standardized thermal cycling tests used to assess the solder interconnection reliability of BGA144 component boards create failure mechanisms that differ from those seen in conditions representing real-use operation.     

烧成和极化条件对PZT—BF—BCN系压电陶瓷电性能的影响

本文探讨了PZT—BF—BCN四元系统压电陶瓷在不同烧成条件下电性能的变化及其显微结构特点,详细研究了极化电场、极化温度和极化时间对该系统电性能的影响,找到了该系统较佳的烧成和极化条件。     

涡流脉冲热像技术中检测条件的粒子群优化

涡流脉冲热像检测中的检测条件优化是最大化裂纹区域生热量以充分发挥检测系统性能的重要保证。针对检测条件选择人工依赖性强等问题,以含有特定尺寸疲劳裂纹的金属平板试件为研究对象,采用仿真和实验相结合的方法,分析了检测条件对裂纹热响应的影响特点,结果表明:裂纹热响应随着激励时间、激励强度的增加而增强;随着提离距离的增加呈现先增强后减弱的趋势。基于仿真与实验结果,提出了一种用于估算特定检测条件下裂纹热响应的多元非线性回归模型,确定了裂纹热响应与不同检测条件之间的定量化关系。最终引入粒子群优化算法进行了检测条件优化,给出了热响应分布图和检出概率分布图。研究成果为涡流脉冲热像检测中的检测条件优化提供理论指导。     

基于不同环境条件下GNSS锚固支持模式研究

针对不同环境条件下 GNSS 锚固支持模式进行了研究，对锚固站在不同环境设定下对 GNSS 基于星间链路的自主导航模式的空间和时间基准保障模式按照预设情况和观测情况的不同进行了分析，从实际应用的角度，对其在地面主控站发生故障、遭遇自然灾害或被战时打击等极端条件下支持方式进行了研究，对 GNSS 锚固支持模式的应用进行了可行性分析。     

Parameter Conditions for Global Stability of FAST TCP

In this letter, we study the global asymptotic stability of FAST TCP in the presence of network feedback delays. Based on a continuous-time dynamic model of FAST TCP and a static approximation of queuing delay at the link, we derive stability conditions for FAST TCP. The derived conditions are explicitly appeared as tuning parameter conditions of FAST TCP, and hence can be satisfied in a distributed way. The simulation results illustrate the validity of the conditions for the global asymptotic stability.     

On an inviable approach for derivation of 2-D stability tests

A tabular stability test for two-dimensional (2-D) discrete systems that was published in these Transaction is shown to be not correct. It is also shown that the claimed new method that it introduced to extend stability conditions from one-dimensional (1-D) to 2-D systems relies on a mathematically inviable argument. The paper tries to find a similar but correct algorithm and stability conditions. The outcome of the search after a stability test with similar algorithm is a variant of the Maria-Fahmy 2-D stability test for which a more concise set of necessary and sufficient conditions for stability are obtained. The search after stability conditions of similar appearance that can be posed on the correct algorithm, yields new necessary conditions for 2-D stability that resemble stability conditions associated with the "reflection coefficient" parameters in the 1-D Schur test.     

Improvement of Temperature Coefficient of Resistance by Co-Implantation of Argon or Xenon or Fluorine in Boron Implanted Polysilicon Resistors

This paper proposes a new method to decrease the absolute value of temperature coefficient of resistance (TCR) in P-type boron implanted polysilicon resistors, at a given intermediate sheet resistance values, by selecting an optimized combination of boron doping implant conditions with co-implantation conditions. The co-implantation ion species that were investigated are fluorine, argon and xenon. Each of the co-implantation species was studied at three different co-implantation conditions and two different boron doping implant conditions of dose and energy.      

Approximate mode conversion coefficients in the Earth-ionosphere waveguide

Constant impedance boundary conditions have been used by many authors to obtain mode reflection and transmission coefficients for propagation across a land-sea discontinuity. The impedance boundary conditions are here replaced by exact boundary conditions and similar formulae are obtained for propagation between a diffuse inhomogeneous isotropic ionosphere and a homogeneous isotropic earth. These formulae permit the use of any ionospheric model with vertical inhomogeneity although some simplification results if impedance boundary conditions are used at the ground. A numerical example is given to illustrate the significance of the formulae.     

无双线性对的门限条件匿名代理重加密方案

条件代理重加密(CPRE)可以根据条件对密文进行细粒度的授权,现有的CPRE方案只检查原密文的条件,忽略了重加密密钥的条件符合性,也不对条件信息进行保护,容易造成隐私泄露。该文构造了基于门限的无双线性对条件匿名代理重加密方案(TB-CAPRE),对密文和重加密密钥的条件同时进行验证,并将敏感的条件信息进行匿名化处理,利用门限将重加密分布到多个代理节点完成,能够抵御合谋攻击。理论分析证明了该方案在随机预言模型下满足适应性选择密文攻击下的不可区分安全性(IND-CCA)。效率和计算量分析表明TB-CAPRE在增加安全性和相关功能后并没有引入过大的开销,可以应用到分布式环境中。