工程图样绘制工作应注意的几个问题

着重阐述了工程图样在生产中的重要作用及正确绘制工程图样应注意的几个问题.     

压电陶瓷微动刀架伺服系统模糊控制器的设计

本文研究了基于模糊数和插值原理的模糊空中算法,并用该算法实现了压电陶瓷微动刀架伺服系统的闭环控制,使其控制精度达到了±0．01μm。     

JHX-5型回柱及调度两用绞车的性能试验方案研究

新型JHX-5型回柱及调度两用绞车是采用少齿差行星传动取代现有的蜗杆-蜗轮传动,该绞车具有结构紧凑、重量轻、传动效率高、加工工艺简单、成本低等特点。通过理论分析并设计制造了样机,拟定了实验方案来测定该新型绞车的拉力、绳速、传动效率等重要参数,对今后的进一步改进和推广应用具有较大的意义。     

渐开线少齿差行星传动的弹流润滑分析

探讨了渐开线少齿差行星传动的弹性流体动力润滑计算,并推导出相应的计算公式以及分析了该传动的润滑状态,为渐开线少齿差行星传动的耐磨损设计提供了必要的理论依据。     

在Y58A插齿机上加工大质数直齿轮的对数分齿计算方法

介绍了在Y58A插齿机上采用对数分齿计算方法加工大质数直齿轮的计算方法和计算实例。生产实践证明,采用对数分齿计算方法既简单易懂、操作方便,同时又能提高工作效率和保证齿轮的加工精度。     

蒙特卡罗方法应用研究

介绍了蒙特卡罗(Monte Carlo)方法,即随机模拟方法,提出了任意分布随机数的产生原理及方法,并用算例说明蒙特卡罗方法的使用过程,同时用2χ拟和优度法验证了其合理性.     

Ultrafine particle concentrations and exposures in seven residences in northern California

Human exposures to ultrafine particles (UFP) are poorly characterized given the potential associated health risks. Residences are important sites of exposure. To characterize residential exposures to UFP in some circumstances and to investigate governing factors, seven single-family houses in California were studied during 2007-2009. During multiday periods, time-resolved particle number concentrations were monitored indoors and outdoors and information was acquired concerning occupancy, source-related activities, and building operation. On average, occupants were home for 70% of their time. The geometric mean time-average residential exposure concentration for 21 study subjects was 14,500 particles per cm(3) (GSD = 1.8; arithmetic mean ± standard deviation = 17,000 ± 10,300 particles per cm(3)). The average contribution to residential exposures from indoor episodic sources was 150% of the contribution from particles of outdoor origin. Unvented natural-gas pilot lights contributed up to 19% to exposure for the two households where present. Episodic indoor source activities, most notably cooking, caused the highest peak exposures and most of the variation in exposure among houses. Owing to the importance of indoor sources and variations in the infiltration factor, residential exposure to UFP cannot be characterized by ambient measurements alone. PRACTICAL IMPLICATIONS: Indoor and outdoor sources each contribute to residential ultrafine particle (UFP) concentrations and exposures. Under the conditions investigated, peak exposure concentrations indoors were associated with cooking, using candles, or the use of a furnace. Active particle removal systems can mitigate exposure by reducing the persistence of particles indoors. Eliminating the use of unvented gas pilot lights on cooking appliances could also be beneficial. The study results indicate that characterization of human exposure to UFP, an air pollutant of emerging public health concern, cannot be accomplished without a good understanding of conditions inside residences.     

裂纹数密度具有空间分布的随机介质模拟理论

利用随机过程的谱展开理论以及Hudson的裂纹介质模型，构造一种裂纹数密度具有空间统计分布的随机介质模型，给出了详细的理论推导过程。该模型利用Hudson理论的将裂纹微观参数(裂纹数密度、裂纹半径等)与裂纹介质的宏观性质(弹性常数)联系起来的特点，对可以用二维指数椭圆型、Gaussian型自相关函数描述裂纹数密度的裂纹介质，进行了二维随机介质的模拟。结果表明：(1)基于这一模拟理论的随机介质模型能灵活、有效地描述实际非均匀、各向异性裂纹介质：(2)裂纹数密度对随机裂纹介质的各个弹性常数具有不同程度的影响：(3)Gaussian型自相关函数能描述单尺度平滑的非均匀介质，而指数型随机介质具有多尺度、自相似的特性。     

室内自然对流数值模拟分析

研究建筑围护结构传热与流体流动综合作用下室内自然对流数值模拟,建立了一套同时在固体-流体区域整体求解连续性方程、动量方程和能量方程的数值模拟方法。具体分析了瑞利数变化范围为104到106时建筑围护结构传热对室内自然对流的影响。数值预测结果表明:该方法能够真实反映室内自然对流问题。为室内自然对流问题数值模拟找到了一种实用有效的方法。     

双代号网络图的绘制方法

从教学及实践的角度出发，就双代号网络图的绘制方法与技巧进行了归纳总结，以便在绘图时能很好地控制整个图形的布局，正确清楚地表达逻辑关系，快速准确地绘出双代号网络图。