Hyperprolactinemia in end‐stage renal disease and effects of frequent hemodialysis

Introduction: End‐stage renal disease is associated with elevations in circulating prolactin concentrations, but the association of prolactin concentrations with intermediate health outcomes and the effects of hemodialysis frequency on changes in serum prolactin have not been examined. Methods: The FHN Daily and Nocturnal Dialysis Trials compared the effects of conventional thrice weekly hemodialysis with in‐center daily hemodialysis (6 days/week) and nocturnal home hemodialysis (6 nights/week) over 12 months and obtained measures of health‐related quality of life, self‐reported physical function, mental health and cognition. Serum prolactin concentrations were measured at baseline and 12‐month follow‐up in 70% of the FHN Trial cohort to examine the associations among serum prolactin concentrations and physical, mental and cognitive function and the effects of hemodialysis frequency on serum prolactin. Findings: Among 177 Daily Trial and 60 Nocturnal Trial participants with baseline serum prolactin measurements, the median serum prolactin concentration was 65 ng/mL (25th–75th percentile 48–195 ng/mL) and 81% had serum prolactin concentrations >30 ng/mL. While serum prolactin was associated with sex (higher in women), we observed no association between baseline serum prolactin and age, dialysis vintage, and baseline measures of physical, mental and cognitive function. Furthermore, there was no significant effect of hemodialysis frequency on serum prolactin in either of the two trials. Discussion: Serum prolactin concentrations were elevated in the large majority of patients with ESRD, but were not associated with several measures of health status. Circulating prolactin levels also do not appear to decrease in response to more frequent hemodialysis over a one‐year period.     

双局域共振机制声子晶体带隙特性研究

提出了一种双局域共振机制,结合有限元法对该机制声子晶体结构的带隙生成机理和带隙的影响因素进行了深入分析研究。2个刚性质量体互为刚性边界和振子,由此产生了2个可以互相转化的局域共振单元。双局域共振结构的带隙位置由2个等效单自由度系统的固有频率共同决定,带隙的宽度与2个质量体密度、内振子半径、弹性介质的弹性模量密切相关。研究发现,2个质量体密度差别越大、弹性介质弹性模量越高,带隙的宽度就越大。该机制在一定程度上削弱了基体与振子的紧密耦合关系,该结构具有较大的带隙变化范围,极大地增大了带隙的宽度,为宽频声子晶体结构的研究提供了新的思路。     

A study on the effect of polishing fluid volume in ball end magnetorheological finishing process

Ball end magnetorheological finishing is a unique process that utilizes a magnetically controlled ball of polishing fluid at the tip of the rotating tool to finish workpiece of different materials and shapes. The aim of this research is to study the effect of polishing fluid volume on finishing spot size and the surface finish associated with it. A magnetostatic simulation is done to find the variation of flux density in the working gap and on the workpiece surface. The maximum limit of the polishing fluid volume is selected on the basis of area of threshold magnetic flux density (minimum value required for finishing) region on the workpiece surface. The surface characteristics and the diameter of the finished spot are analyzed by varying the fluid volume. The surface obtained with high fluid volume is poorly finished and has scratch marks as the excess fluid flows out from the working gap and forms a thick ring at the periphery of the tool tip. Contrary to this, if the fluid volume is too less, then it merely rotates over the workpiece surface without causing any finishing action. An optimum range of fluid volume produces a good quality surface finish with constant finished spot size.     

引入扰动补偿的多电机滑模协同控制研究

目的 解决多电机协同控制时容易受到非线性和外界扰动等不定因素的影响。方法 基于多电机偏差耦合控制结构,与引入扰动补偿的混合非奇异终端滑模变结构控制相结合,并与传统PI(Proportional Integral)调节器控制效果做仿真对比。结果 本文所提控制算法通过计算机仿真软件进行验证分析,该算法能够使得电机在启动时效果较好,转速误差在受到扰动时效果优于传统PI控制约8.50%;电机转矩在受到扰动后控制效果更加理想,几乎不存在迟滞时间就能达到新的负载转矩值;在受到负载扰动时转速误差波动较小,优于传统PI控制约8.83%。结论 通过计算机仿真验证得出,引入扰动补偿后的混合非奇异终端滑模变结构控制系统的响应时间和收敛速度、控制性能和鲁棒性都要优于传统PI控制的。     

铝合金曲轴后端盖压铸模浇注与排溢系统优化设计

为满足某发动机曲轴后端盖铸件高质量的外观与密封要求,针对该铝合金零件进行了高压铸造模具的浇注与排溢系统优化设计。首先根据铸件形貌和尺寸特征进行浇道、内浇口和排溢槽的理论设计,随后采用ProCAST软件模拟高压铸造充型、凝固过程,对铸件的卷气、缩松、缩孔及组织进行预测分析。研究发现,方案1的平直型横浇道浇注方案,金属液冲击型芯容易产生紊流和飞溅,且设置在铸件中间和下部的排溢系统不能减少紊流,易形成裹气和大的缩孔缺陷;而方案2为钳形浇道,去除方案1铸件中部的溢流槽并将下部连通溢流槽改为两个,明显改善铸件内裹气和缩孔现象,确定方案2为最终方案。试模铸件外观质量良好,经X射线探伤发现铸件无裂纹,厚大缩孔位置与缺陷仿真预测良好吻合;金相显微镜(OM)、扫描电镜(SEM)和电子背散射衍射(EBSD)观察组织发现,铸件晶粒细小、组织致密,晶粒取向差小,内部应力小,与组织和应力仿真结果一致;能谱分析(EDS)、X射线衍射(XRD)分析表明,铸件成分均匀,组织内部无杂质。本研究可为端盖类铝合金压铸件模具及工艺开发提供参考。     

车辆四轮转向系统的控制方法

系统地评述了车辆四轮转向系统的原理及其控制方法的发展,在此基础上指出四轮转向系统的研究必须以闭环综合评价为出发点,并与其它主动安全技术相结合才能真正达到实用阶段。     

基于灰关联分析方法

针对一致关联度算法不具有普遍性和动态改变惯性权的自适应粒子群算法(DCW)不易跳出局部收敛能力的缺陷,本文提出了完全关联度算法和自适应变异的动态粒子群优化算法。完全关联度算法主要用来选择软测量的辅助变量。在改进的粒子群优化算法中,除了采用动态惯性权重外,还引入了自适应学习因子和新的变异算子。为了构造一种性能较好的神经网络,采用改进的粒子群优化算法来优化神经网络所有的权值参数,并将提出的软测量建模方法预测延迟焦化的汽油干点,实验结果表明,与DCW算法优化神经网络(DCWNN)的建模方法相比,该算法不仅具有较好的泛化性能,而且具有较高的精度和良好的应用前景。     

基于DSP的列车信号处理算法分析

介绍一种互相关检测解调算法用于列车交通信号的检测,可将不同制式下的各种高频信号送DSP进行处理,提取出承载列车控制信号的低频信号,以便分析其中的载频信息和低频信息;对互相关检测算法流程作了分析说明,提出该算法在DSP器件上的基本实现方案,并给出了部分实验数据;采用互相关解调算法(能量算法)对轨道信号进行解调,具有运算速度快、精度高、抗干扰性能好和对硬件资源要求低等特点;经过反复的轨道信号实测,完全符合国家标准。     

航空全双工交换式以太网探究

针对传统航空总线不能满足下一代航空电子系统对高速和实时性数据通信的要求,提出航空全双工交换式以太网（AFDX）。描述AFDX通信网络的特点、结构、通信机制和协议栈,并给出AFDX终端系统和网络交换机的设计思路,阐明硬件结构和软件流程,对AFDX通信网络的研究具有一定的参考和推广价值。     

光电探测器前置放大电路研究

在弱光检测中,光经过光电探测器转换为电信号,此信号极其微弱。要实现光电转换,并有效地利用这种信号,必须对光电器件采取适当偏置,然后再将已转换的电信号进行放大处理。对光电导器件、光伏型探测器、光电流型探测器的前置电路进行研究与设计。根据不同种类的探测器及探测光信号的频率特性选取不同的偏置与放大电路,使前置电路的性能达到最优。