长三角地区多直流馈入及交直流相互作用特性述评

随着长三角地区电力负荷的增长以及西部水电资源的大力开发,我国中路远距离"西电东送"规模迅速扩大,大容量电力由高压直流输电(HVDC)输送.长三角地区即将成为一个具有多馈入直流系统的负荷中心,直流系统输送容量之大、落点之密集在国际上不多见.对长三角多馈入直流输电系统的概况及其特点进行了介绍.描述了多馈入直流输电系统各种相互作用特性,并对研究不同相互作用的研究方法、分析工具和评估指标进行了评述.在此基础上,针对长三角多馈入直流输电系统的特点,对其交直流系统间相互作用的特性及其研究方法给出了一些思路.     

斩波串级调速系统换相失败的分析与仿真

换相失败是串级调速系统逆变器的常见故障,与许多因素有关。分析了串级调速系统换相失败的原因及其影响因素,并针对电源故障引起的换相失败,提出了控制方法,运用MATLAB/simulink对该方法进行仿真研究。结果表明该方法是准确的、可行的,便于工程上的应用研究。     

专用计算机局域网安全性分析与设计方法讨论

通过分析专用计算机网络的特点,运用系统工程方法,总结出普遍适用于专用局域网的安全性分析与设计模型。该模型以整体视角引入故障树分析方法,分析导致整个网络安全受损的所有因素,同时以局部视角,提出了单个网络、节点的安全性分析方法和工作程序,为全面分析网络安全薄弱环节和隐患,提出了新的思路和方法。     

多智能方法及其融合系统在化工过程故障诊断中的应用

简要介绍了决策树、神经网络、K近邻等五种智能方法,提出了一种将这五种智能方法相融合的故障诊断系统,并将其应用在催化裂化装置上.通过对这五种智能方法及其融合系统的性能考察表明,融合策略发挥了各方法的优点,回避了它们的缺点,提升了系统的整体性能,其召回率为100%,精确度为98%.     

摩托车离合器主轴断裂失效分析及其机理

本文分析了摩托车离合器主轴用材、金相组织、显微硬度以及断口扫描电镜(SEM)宏观、微观形貌,结果表明,该摩托车离合器主轴断裂主要原因是轴颈突变截面尖角顶端曲率半径ρ值太小,形成很大的应力集中从而形成裂纹源,然后裂纹逐步扩展造成的。     

MicroRNA Expression in Clear Cell Renal Cell Carcinoma Cell Lines and Tumor Biopsies: Potential Therapeutic Targets

This study was carried out to quantitate the expression levels of microRNA-17, -19a, -34a, -155, and -210 (miRs) expressed in nine clear cell renal cell carcinoma (ccRCC) and one chromophobe renal cell carcinoma cell line with and without sarcomatoid differentiation, and in six primary kidney tumors with matching normal kidney tissues. The data in the five non-sarcomatoid ccRCC cell lines—RC2, CAKI-1, 786-0, RCC4, and RCC4/VHL—and in the four ccRCC with sarcomatoid differentiation—RCJ41T1, RCJ41T2, RCJ41M, and UOK-127—indicated that miR-17 and -19a were expressed at lower levels relative to miR-34a, -155, and -210. Compared with RPTEC normal epithelial cells, miR-34a, miR-155, and miR-210 were expressed at higher levels, independent of the sarcomatoid differentiation status and hypoxia-inducible factors 1α and 2α (HIFs) isoform expression. In the one chromophobe renal cell carcinoma cell line, namely, UOK-276 with sarcomatoid differentiation, and expressing tumor suppressor gene TP53, miR-34a, which is a tumor suppressor gene, was expressed at higher levels than miR-210, -155, -17, and -19a. The pilot results generated in six tumor biopsies with matching normal kidney tissues indicated that while the expression of miR-17 and -19a were similar to the normal tissue expression profile, miR-210, -155, -and 34a were expressed at a higher level. To confirm that differences in the expression levels of the five miRs in the six tumor biopsies were statistically significant, the acquisition of a larger sample size is required. Data previously generated in ccRCC cell lines demonstrating that miR-210, miR-155, and HIFs are druggable targets using a defined dose and schedule of selenium-containing molecules support the concept that simultaneous and concurrent downregulation of miR-210, miR-155, and HIFs, which regulate target genes associated with increased tumor angiogenesis and drug resistance, may offer the potential for the development of a novel mechanism-based strategy for the treatment of patients with advanced ccRCC.     

Boolean difference techniques in fault tree analysis

For an electrical, mechanical, or hybrid system described diagramatically as a network of interconnected components, fault tree modeling of system reliability as a function of individual component failure probabilities gives rise to logic expressions obtained from the network connections. Application of the method of Boolean differences in the analysis of such Boolean expressions is discussed, and it is shown that the influence of the status of specific components on the reliability of the total system may be investigated by straightforward algebraic operations on the network failure function.     

Could SGLT2 Inhibitors Improve Exercise Intolerance in Chronic Heart Failure?

Despite the constant improvement of therapeutical options, heart failure (HF) remains associated with high mortality and morbidity. While new developments in guideline-recommended therapies can prolong survival and postpone HF hospitalizations, impaired exercise capacity remains one of the most debilitating symptoms of HF. Exercise intolerance in HF is multifactorial in origin, as the underlying cardiovascular pathology and reactive changes in skeletal muscle composition and metabolism both contribute. Recently, sodium-related glucose transporter 2 (SGLT2) inhibitors were found to improve cardiovascular outcomes significantly. Whilst much effort has been devoted to untangling the mechanisms responsible for these cardiovascular benefits of SGLT2 inhibitors, little is known about the effect of SGLT2 inhibitors on exercise performance in HF. This review provides an overview of the pathophysiological mechanisms that are responsible for exercise intolerance in HF, elaborates on the potential SGLT2-inhibitor-mediated effects on these phenomena, and provides an up-to-date overview of existing studies on the effect of SGLT2 inhibitors on clinical outcome parameters that are relevant to the assessment of exercise capacity. Finally, current gaps in the evidence and potential future perspectives on the effects of SGLT2 inhibitors on exercise intolerance in chronic HF are discussed.     

P波空间斜入射下沥青混凝土面板堆石坝响应特性及面板破坏评价

地震波入射方位和斜入射角度对于沥青混凝土面板堆石坝地震响应结果有着显著影响。本文从地震动传播机制出发,基于波场叠加原理,推导了P波以任意入射方位角和斜入射角空间斜入射下弹性半空间自由场计算公式,建立了P波空间斜入射波动输入模型。以不同应变率下的沥青混凝土单轴动态拉伸试验结果为基础,提出了考虑抗拉强度随应变率实时变化的沥青混凝土面板破坏评价方法。考虑16种不同入射方位角和斜入射角下的P波空间斜入射工况,从面板应力和加速度两方面分析了入射方位角和斜入射角对某实际沥青混凝土面板地震响应特性的影响,并进行了沥青混凝土面板的抗拉破坏评价,分析了静态评价方法与动态评价方法的差异。结果表明,所建立的P波空间斜入射波动输入模型能够准确模拟半空间自由场,波动输入数值解与解析解符合良好;与垂直输入射相比,面板顺水流向、垂直水流向加速度峰值最大分别增加135.9%和92.7%,竖向加速度峰值最大减少68.3%;空间斜输入导致面板动应力增大,主拉应力和主压应力最大分别增加3.6倍和2.7倍,忽略入射方位角和斜入射角可能会严重低估面板的地震响应。传统将静态强度提高30%作为动态强度的面板抗拉破坏判别方法过于严格,本文提出的考虑应变率效应的沥青混凝土面板破坏评价方法较为符合实际。     

具有数据包丢失的网络控制系统主动容错控制

在保证稳定性的前提下,研究具有数据包丢失的网络控制系统主动容错控制问题.基于一类包含马尔可夫丢包过程的网络控制系统模型,考虑了执行器可能失效的情况.利用Lyapunov稳定性理论和线性矩阵不等式方法,获得了系统的保性能被动容错控制器.从控制性能的角度考虑,针对不同的执行器失效模式,得到了丢包网络环境下系统的主动客错控制器的设计方法.数值示例表明,该控制器设计方法是有效的.