混流式水泵工况起动过渡过程导叶漏水的计算

本文利用动量矩定理推导出抽水蓄能电站水泵轮机导叶漏水量与漏水转矩的计算公式。同时在考虑漏水转矩的情况下,完成了两座抽水蓄能电站混流式水泵机组泵工况起动过渡过程的校核计算,分析了导叶间隙、漏水量等对起动过程的重要影响,过大的导叶间隙将使机组不能起动。计算分析表明,本文提出的考虑导叶间隙漏水影响进行泵工况起动过渡过程的计算方法是正确的。正确考虑漏水转矩影响,对水泵水轮机的运行特性和过滤过程的准确计算具     

2019年国外导航技术发展综述

近年来,国外导航技术的发展呈现出多系统融合的发展态势,结合2019年国外导航技术的发展动态,对美国、欧盟、俄罗斯、印度等国家和地区的卫星导航、惯性导航、天文导航、视觉导航、数据库匹配导航、仿生导航、量子导航和全源导航等技术发展现状进行了总结分析,并对相关技术发展进行了展望。     

基于疲劳-蠕变载荷等效转换的涡轮盘载荷谱编制及寿命预测

针对雨流计数法在峰谷值提取时进行等值压缩,忽略保载时间的问题进行了改进,提出了一种基于损伤曲线的疲劳-蠕变载荷等效转换方法。利用非线性疲劳损伤累积函数和损伤等效原则,建立了不同应力水平、不同保载时间下疲劳-蠕变载荷与疲劳载荷之间的等效换算模型。利用涡轮盘材料试验数据,计算了不同循环加载条件下的等效换算比,得到了其随保载时间的变化规律。利用改进的雨流计数法,编制了航空发动机高压涡轮盘载荷谱,并将其与寿命-时间分数预测法相结合,得到了涡轮盘剩余寿命。结果表明,改进的雨流计数法综合考虑了疲劳-蠕变耦合损伤对涡轮盘寿命造成的影响,相比于传统雨流计数法,寿命预测误差降低了15.02%,验证了该方法的有效性。     

An Investigation into Vertical Bias Effects

ABSTRACT

In three experiments, after exploring a virtual environment (VE), adult participants made spatial judgments about the location of target objects that were higher and lower than their perceived test location within the VE. In Experiment 1, the locations of the target objects were inferred from verbal instructions. The main results were a tendency to judge objects as closer to the horizontal plane than their true locations, and more efficient downward than upward judgments. Both effects generally accord with findings reported by Wilson et al. (2004a Wilson, P. N., Foreman, N., Stanton, D. and Duffy, H. 2004a. Memory for targets in a multilevel simulated environment: Evidence for vertical asymmetry in spatial memory. Memory & Cognition, 32: 283–297. [Crossref] , [Google Scholar], 2004b Wilson, P. N., Foreman, N., Stanton, D. and Duffy, H. 2004b. Memory for targets in a multi-level simulated-environment: A comparison between able-bodied and physically disabled children. British Journal of Psychology, 95: 325–338.  [Google Scholar]). In Experiments 2 and 3, which were closely modeled on the design of the Wilson et al. studies, regression to the horizontal plane was noted but no downward bias was observed. A misperception in the viewing height between the floors and ceilings of the virtual rooms was apparent in both experiments. The results from the present study together with earlier investigations suggest different hierarchical encoding of between-axis and within-axis information.     

Revisiting Perspective-Taking: Can People Maintain Imagined Perspectives?

Abstract

Three experiments were conducted to examine whether people can adopt and maintain imagined perspectives in the absence of target information. The task used entailed providing information about an imagined perspective in advance of target information to examine whether this would facilitate perspective-taking performance and reduce or eliminate alignment effects that are commonly reported in the literature. The three experiments employed different types of spatial environments: an environment learned from navigating a computer screen (Experiment 1), and an immersive environment that was either remote (Experiment 2) or immediate (Experiment 3) at the time of retrieval. Across the three experiments, results showed that information about an imagined perspective can be utilized ahead of target information. Furthermore, they suggested that alignment effects can be reduced as a result of processing information about perspective ahead of target information, but only when reasoning about specific nonimmediate spatial relations (Experiments 1 and 2). Results are discussed in connection with previous findings on spatial updating and the organizational structure of spatial memory.     

航天器多继电器线圈并联电路的可靠性研究

航天器配电系统中广泛采用多继电器线圈并联电路作为平台设备和负载的供电通路开关。文章从继电器互感效应入手,对多继电器线圈并联电路在指令发出、指令结束2 种工况下的电路可靠性进行了分析,结果表明目前常用的继电器线圈并联电路存在可靠性隐患。因此,针对隐患提出了在继电器线圈前串接二极管的电路可靠性优化方案。试验结果表明,优化后的电路形式可以有效提高电路的可靠性。     

环氧树脂基形状记忆复合材料的制备与性能

以自制的形状记忆环氧树脂为基体,CCF300级碳纤维U-3160织物为增强材料,采用真空袋成型工艺制备形状记忆复合材料,分析碳纤维含量对复合材料的形状记忆性能的影响。结果表明,当碳纤维含量为0%~50%时,随着增强体碳纤维含量的增加,复合材料的形状固定率由98%降至91%,形状回复率也由98%降至91%。在有限次的循环实验中,循环次数对形状固定率和形状回复率没有明显的影响。     

空间平台量子密钥纠错处理研究

空地量子通信受诸多因素的影响,量子密钥的原始码存在一定的误码率,需要通过空间平台与和地面之间的双向数据交互对错误的密钥进行纠正。受空间平台硬件设备限制,数据的传输速度、存储空间以及处理能力等均有限,对空间平台量子纠错算法提出了更高的要求。为此给出了一种适合空间平台环境的基于汉明码的Winnow纠错算法,这种纠错处理算法不仅容易实现,而且在空间平台资源受限的情况下可以兼顾运算效率和纠错效率。     

射线透照等效系数测试方法分析

为获得不同透照电压下不同标准材料的射线透照等效系数,以50 kV 透照电压为例,以钛为标准 材料,揭示了同时透照法和图像法两种等效系数的测试方法。通过对同时透照法步骤及存在问题的分析,引入 了解决问题的阶梯扩展和厚度校正两种手段。在等效系数图像法的分析过程中,明确了曝光曲线种类和黑度 选取的原则,阐述了曝光曲线与图像法的关系,结合数学手段运用,获得了等效系数与透照电压相关,但不随曝 光量改变而变化的结论。     

一种新型的低噪声硅微机械陀螺电容读出电路

陀螺系统的微机械敏感结构部分的性能提升受到成本、工艺的限制,有较高难度,故提升接口电路的各项性能成为提升整个系统性能的关键。因此,电容读出电路作为微机械陀螺系统中非常重要的组成部分,该电路性能的优劣直接决定着陀螺的测量精度。为实现硅微陀螺高精度检测,设计了一款低噪声的电容读出电路。在陀螺与读出电路之间设计斩波开关,基于斩波技术进行低噪声设计,采用相关双采样技术用来降低关键的第一级放大电路的低频闪烁噪声和开关噪声。采用了一种简化的陀螺测试模型,用于读出电路的独立测试。读出电路在0.18μm CMOS工艺下设计流片,测试结果表明,该电容读出电路输出噪声为-122.8dBV/Hz1/2,可实现0.06aF/Hz1/2的电容分辨率。