Effect of ECAP process on liquid distribution of AZ80M alloy during semi-solid isothermal heat treatment

Two kinds of semi-solid samples of AZ80−0.2Y−0.15Ca(wt.%)(AZ80M)magnesium alloy were prepared by semi-solid isothermal heat treatment of materials with and without equal channel angular pressing(ECAP)process.The microstructures of initial and semi-solid treated samples were compared and analyzed.The results showed a significant difference in the liquid phase distribution between three-pass ECAP processed(3P)and as-received samples during the isothermal heating process.The semi-solid 3P sample showed a more uniform liquid distribution due to its smaller dihedral angle.Besides,the coarsening processes of solid grains of as-received and 3P samples were dominated by the coalescence and Ostwald ripening mechanism,respectively.The difference of coarsening processes was mainly related to the proportion of the high-angle grain boundaries in materials,which further affected the evolution behavior of the liquid pools.

The GIS and analysis of earthquake damage distribution of the 1303 Hongtong M=8 earthquake

The geography information system of the 1303 Hongtong M=8 earthquake has been established. Using the spatial analysis function of GIS, the spatial distribution characteristics of damage and isoseismal of the earthquake are studied. By comparing with the standard earthquake intensity attenuation relationship, the abnormal damage dis-tribution of the earthquake is found, so the relationship of the abnormal distribution with tectonics, site condition and basin are analyzed. In this paper, the influence on the ground motion generated by earthquake source and the underground structures near source also are studied. The influence on seismic zonation, anti-earthquake design, earthquake prediction and earthquake emergency responding produced by the abnormal density distribution are discussed.

Analysis of the characteristics of snow drop size distribution in the Qilian Mountains

Under the Watershed Allied Telemetry Experimental Research （WATER） project, a significant amount of snow size data was collected from March to April 2008. However, because of limited observation data for the Qinghai-Tibet Plateau, the modeling behavior was not satisfactory. This paper demonstrates characteristics of the snow drop size distribution （SSD） in this region. The experimental area is located in the northeastern part of the Qinghai-Tibet Plateau. The Heihe River Basin, which is the second largest interior river basin in China and is located on the northern slopes of the Qilian Mountains, was selected as the simulation region. This basin ranges from approximately 5,000 m to 1,000 m in elevation. A new generation Parsivel disdrometer, the OTT Parsivel, was used for measurements. Four data sets were compiled to determine the average distributions for four different snowfall rates. The characteristics of the snow particle size distribution in the mountainous area were analyzed. Similar to the raindrop distribution, there was a multi-peak structure. Most peaks appear in the D 〈 2 mm region （D： diameter of the snow drop size）. An M-P distribution and a Г distribution were developed based on the precipitation data observed in Qilian mountainous area. We found that the Г distribution has a better fit than the M-P distribution for the actual distribution. In addition, we observed that the intercept parameter （N0） and the slope parameter （Λ） correlate well with the shape parameter （μ）. The disdrometer data can also be used to model the reflectivity factor （ZH） and differential reflectivity factor （ZDR）. The radar reflectivity （ZHH, ZVV） and differential reflectivity （ZDR） were modeled in order to facilitate understanding of the connections between radar and ground measurements, and were used to support work for the improvement of rainfall estimates by polarimetric radar. Rain rate estimation using radar measurements was based on empirical models, such as the Z-R relationship and R（ZH, ZDR） in the Qilian mountainous areas. The relationship of R=0.017×100.079×ZH-0.022×ZDR is better than R=0.019×100.078×ZH for estimating R （melted snow）. The normalized errors （NE） of R（ZH） and R（ZH, ZDR） are 13.22% and 5.20%, respectively.

Likelihood and Quadratic Distance Methods for the Generalized Asymmetric Laplace Distribution for Financial Data

Maximum likelihood (ML) estimation for the generalized asymmetric Laplace (GAL) distribution also known as Variance gamma using simplex direct search algorithms is investigated. In this paper, we use numerical direct search techniques for maximizing the log-likelihood to obtain ML estimators instead of using the traditional EM algorithm. The density function of the GAL is only continuous but not differentiable with respect to the parameters and the appearance of the Bessel function in the density make it difficult to obtain the asymptotic covariance matrix for the entire GAL family. Using M-estimation theory, the properties of the ML estimators are investigated in this paper. The ML estimators are shown to be consistent for the GAL family and their asymptotic normality can only be guaranteed for the asymmetric Laplace (AL) family. The asymptotic covariance matrix is obtained for the AL family and it completes the results obtained previously in the literature. For the general GAL model, alternative methods of inferences based on quadratic distances (QD) are proposed. The QD methods appear to be overall more efficient than likelihood methods infinite samples using sample sizes n ≤5000 and the range of parameters often encountered for financial data. The proposed methods only require that the moment generating function of the parametric model exists and has a closed form expression and can be used for other models.

Thermal Modeling of a Multilayer Integrated LC Filter for Temperature Distribution Calculation

Thermal behavior of integrated passive components has become an important issue when designing these components. This paper presents the thermal modeling of a multilayer integrated LC filter used in DC-DC step-down converter for temperature distribution calculation. The approach used for this analysis is based on thermal equivalent circuit. Temperature distribution is obtained from algebraic equation, which is in vector and matrix form. The results of analytical calculation are compared with simulation results from finite element method. These results showed a good correlation.

Diagnostics of electron temperature and ions distribution in expanding Al plasmas pumped by a ns-pulsed 1.06μm laser

Resonance lines are extensively used to diagnose electronic temperature Te and ions distribution. However, the analysis of the x-ray spectroscopy emitted from plasmas produced by a ns laser Jsually needs the help of a code or some assumptions. In this paper, a diagnostic idea of using line-pairs emitted from a doubly-excited state is proposed. By using the method presented in this paper, Te and the fractional population ratio of bare nuclei and H-like ions are directly obtained from the emission intensity ratios.

Málaga湍流信道下改进型光广义空间调制

针对传统光广义空间调制(OGSM)使用固定的光学天线组合集导致系统空间资源浪费和误码率性能受限的问题,提出一种基于低复杂度自适应光学天线组合集选择算法的改进型方案。首先,利用信道状态信息计算光学天线组合之间的欧氏距离矩阵。然后,基于欧氏距离等价原则和最大范数天线选择的思想,删除信道状态较差的光学天线组合,最终保留下的天线组合即当前状态下的最优光学天线组合集。所提算法避免了对所有候选天线组合的遍历,很大程度上降低了算法复杂度。仿真结果表明,所提方案的误码率性能在不同条件下均优于传统OGSM。

分配特殊群桩空间作用效应的双向m法

群桩到单桩的作用分配是桩基计算的关键问题,针对规范中的单向m法只适用于平面作用的局限性,从单桩刚度、群桩刚度、受力平衡方程3个层面进行公式推导,建立了变形协调的群桩刚度矩阵和空间受力平衡方程,形成了适用于空间作用的双向m法,并以对称等长直桩、双向斜桩、不对称桩为计算实例,对比分析了单向m法和双向m法的计算结果。结果表明:单向m法计算对称等长直桩时,结果准确,计算双向斜桩时,单桩的弯矩和剪力波动较大,最大值偏小20%左右,计算不对称桩时,单桩外力之和与总外力不闭合,可信度低;而双向m法的理论解可覆盖这些桩基类型,结果更接近有限元数值解。研究成果为特殊桩基提供了一种快速且简便的计算方法,扩展了公路和铁路桥梁桩基设计规范的适用范围。

皮下注射^(99)Tc^(m)-硫胶体在大鼠体内药代动力学和组织分布研究

目的研究皮下注射^(99)Tc^(m)-硫胶体在大鼠体内的药代动力学、组织分布和排泄特征。方法取颈背部皮下注射^(99)Tc^(m)-硫胶体后不同时间点大鼠血液,采用三氯醋酸(TCA)沉淀法测定血清的放射性摄取值。另取足趾皮下注射^(99)Tc^(m)-硫胶体大鼠进行SPECT/CT扫描,通过图像分析测定其每克组织百分注射剂量率(%ID/g)。结果大鼠皮下注射^(99)Tc^(m)-硫胶体后,药物在血液中极少分布,24h内血清放射性摄取值小于0.017%ID/mL。足趾皮下注射^(99)Tc^(m)-硫胶体后,药物主要聚集在注射部位、腘窝淋巴结和髂骨淋巴结,其他脏器摄取值均小于0.4%ID/g。给药后48h,经胆汁累积排泄率约为1.57%。给药后72h,经粪尿累积排泄率约为6.95%。结论大鼠皮下注射^(99)Tc^(m)-硫胶体后药物主要滞留在注射部位,通过淋巴系统向腘窝淋巴结和髂骨淋巴结扩散,血液和各脏器分布很低,排泄缓慢。

不同标记时间的锝[^(99)Tc^(m)]植酸盐注射液在靶器官中放射性摄取量的显著性差异分析

目的判断在标记后第0小时和标记后第6小时锝[^(99)Tc^(m)]植酸盐注射液在小鼠肝脏和甲状腺中的放射性摄取率是否存在显著差异,为产品有效期的制定提供依据。方法以3批锝[^(99)Tc^(m)]植酸盐注射液和9只小鼠为实验对象,将小鼠分为3组,每组3只。通过尾静脉注射的方式向第1~3组小鼠体内注射第1~3批标记后第0小时的锝[^(99)Tc^(m)]植酸盐注射液604~734kBq,通过单因素方差分析(One-Way ANOVA)对实验数据进行统计分析,先行判断批间显著性差异;以3批锝[^(99)Tc^(m)]植酸盐注射液和18只小鼠为实验对象,将小鼠分为6组,每组3只。其中,通过尾静脉注射的方式向第1~3组小鼠体内注射第1~3批标记后第0小时的锝[^(99)Tc^(m)]植酸盐注射液440~584kBq,同法向第4~6组小鼠体内注射第1~3批标记后第6小时的锝[^(99)Tc^(m)]植酸盐注射液440~584kBq,通过单因素方差分析对实验数据进行统计分析。结果第1~3组小鼠肝脏和甲状腺摄取率的假设检验F值分别为0.307和0.800,均小于F-crit值5.143,即3批锝[^(99)Tc^(m)]植酸盐注射液的肝与甲状腺放射性摄取率差异没有统计学意义;第1~3组、4~6组小鼠肝脏和甲状腺摄取率的假设检验F值分别为0.084和0.941,均小于F-cirt值4.494,即标记后0h和标记后6h的锝[^(99)Tc^(m)]植酸盐注射液在小鼠体内的分布差异无统计学意义。结论标记6h后的锝[^(99)Tc^(m)]植酸盐注射液在小鼠肝脏和甲状腺的放射性摄取率均满足药典要求,且药物仍然可以保持良好的生物分布特性,锝[^(99)Tc^(m)]植酸盐注射液的有效期制定为不大于6h。

具有随机检修-策略M/G/1系统队长的瞬态与稳态分析

研究一个具有随机检修<p,Y>-策略的M/G/1排队系统,当系统变空时,以概率p(0≤p≤1)对系统进行检修,且检修时间是具有任意分布的随机变量。首先,分析了队长的嵌入马尔可夫链,得到了其稳态分布的概率母函数。其次,讨论了在任意时刻t队长的瞬态分布,得到了队长的瞬态分布关于时间t的拉普拉斯变换表达式。在队长瞬态分析的基础上,应用洛必达法则,通过直接计算获得了在任意时刻队长的稳态分布的递推式,给出了稳态队长的随机分解结构。最后,建立了系统的费用模型,并通过数值实例得到了使系统费用最少的最优检修策略。

GLOBAL STABILITY IN HOPFIELD NEURAL NETWORKS WITH DISTRIBUTED TIME DELAYS

In this paper, without assuming the boundedness, monotonicity and differentiability of the activation functions, the conditions ensuring existence, uniqueness, and global asymptotical stability of the equilibrium point of Hopfield neural network models with distributed time delays are studied. Using M-matrix theory and constructing proper Liapunov functionals, the sufficient conditions for global asymptotic stability are obtained.

Steady-State Analysis of the Distributed Queueing Algorithm in a Single-Channel M2M Network

The Distributed Queuing (DQ) algorithm is predicted as one of the solutions to the issues currently found in IoT networks over the use of Aloha based algorithms. Since recently, the algorithm has been of interest to many IoT researchers as a replacement of those Aloha variants for channel access. However, previous works analyzed and evaluated the DQ algorithm without any consideration of the stability of its queues, assuming it is stable for any given number of nodes in the network. In this paper, we define the DQ stability condition in a single-channel M2M environment considering a traffic model of periodic and urgent frames from each node in the network. Besides, a steady-state evaluation of the algorithm’s performance metrics is also presented. In general, the DQ algorithm, when it is stable, was observed not to efficiently use the contention slots for the collision resolution. In a single-channel environment, the DQ algorithm is found to outperform the Aloha based algorithms only in an idle-to-saturation scenario.

基于改进Jacobian-Free Newton-GMRES(m)的电力系统分布式潮流计算

为了提高互联电网分布式潮流算法的实用性,应尽可能减少协调计算中的交换信息。文中采用隐函数方式表示分布式潮流的边界协调方程,并采用具有自适应预处理能力的NewtonGMRES(m)方法构建分解协调算法。该方法具有Jacobian-Free特性,协调计算中只需要交换边界节点状态信息。以IEEE标准系统和大规模实际系统为算例的测试结果表明,新的分布式潮流算法具有较高的收敛性,数据交换接口简单,实用性强,适合于求解连续变化的分布式潮流问题。

配电管理系统(DMS)及其应用功能

结合我国地区电网调度管理体制，将地区电网调度自动化功能以 １０ ｋ Ｖ 为界分为地区调度和配电控制管理两部分，前者采用部分能量管理系统（ Ｅ Ｍ Ｓ）功能，后者采用配电管理系统（ Ｄ Ｍ Ｓ）功能；介绍了 Ｄ Ｍ Ｓ的适用范围、特点、结构及与其他系统的集成关系；叙述了 Ｄ Ｍ Ｓ应用软件的功能和特点；讨论在配电系统中引入地理信息系统（ Ｇ Ｉ Ｓ）的必要性以及 Ｇ Ｉ Ｓ与 Ｄ Ｍ Ｓ的结合方式、 Ｇ Ｉ Ｓ与 Ｄ Ｍ Ｓ的动态数据交换、 Ｇ Ｉ Ｓ在线和离线应用功能；最后强调了在 Ｄ Ｍ Ｓ开发与实施中需要重视的几个问题。

有限精度混沌系统的m序列扰动实现

本文研究利用ｍ序列的扰动来实现有限精度混沌系统的方法．考察了扰动序列的周期、幅度以及扰动分布对混沌信号特性的影响．研究表明，扰动ｍ序列所需的阶数取决于混沌序列所需要达到的周期长度，扰动的位数取决于混沌映射的最大斜率．随着混沌系统实现精度的提高，所需的扰动幅度呈指数减小．

基于Jacobian-Free Newton-GMRES(m)方法的电力系统分布式暂态仿真算法

分布式暂态仿真是实现市场环境下互联电力系统在线一体化仿真分析的有效途径。文中研究了电力系统分布式暂态仿真计算模型,提出了基于Jacobian-Free Newton-GMRES(m)方法的协调求解算法。该算法只需要交换边界母线状态信息,接口简单,实用性强。为了提高算法收敛速度,减少协调求解所需通信次数,提出了自适应预处理和连续修正预处理矩阵、预估边界条件初值及多时步同时协调等改进方法并将其应用于新算法中。测试结果表明,新的暂态仿真分解协调算法收敛快,通信次数少,非常适合在基于广域网络的分布式环境中实现。

推广的(t，T)策略下M/G/1排队系统队长分布的递推解及最优策略

本文考虑当系统变空后的延迟关闭时间为一般概率分布的(t,T)策略下的M/G/1/排队系统。通过引进"服务员忙期"和使用全概率分解技术,首次研究了系统在任意时刻队长的瞬态性质,导出了队长瞬态分布的L变换的递推表达式和稳态分布的递推表达式,进一步得出了系统稳态队长的随机分解结果。最后,建立系统的费用结构模型,讨论了系统变空后的最优关闭时间,并给出了具体数值计算例子。

M-Z干涉仪型光纤分布式扰动传感系统模式识别方法

针对M-Z干涉仪型光纤分布式扰动传感系统输出信号短时频率随外界扰动变化的特征,提出了基于短时频率-时间特性的模式识别算法。采用提取短时过电平率来描述传感信号的短时平均频率-时间特性,并将提取出来的时频特性分段后建立相应的特征元素模型,通过动态规划算法(DTW)筛选出最优特征元素模型,将信号所有最优模型的参数作为信号特征输入到人工神经网络(ANN)进行学习和判决,降低了ANN的训练难度以及对时间的敏感性,提高了系统的环境适应能力。实验结果表明:该方法可以有效区分瞬时作用、长时作用、径向作用和不规则作用等多种不同扰动事件,平均识别速度在0.26 s之内,平均识别准确度在97%以上。

混合威布尔分布参数估计的L-M算法

混合威布尔分布模型常用来分析具有多种失效模式的机械系统或零部件的可靠性寿命数据,为提高混合威布尔分布未知参数估计的精度,利用非线性最小二乘理论,建立了小子样条件下两重混合威布尔分布参数优化估计模型,将L-M算法用于优化求解。以概率图参数估计法的结果作为迭代初始值,提高了迭代求解的速度。计算实例表明利用该方法估计混合威布尔分布参数是可行的,而且能够获得较精确的结果。