云存储环境下的负载均衡策略研究

云存储系统具有高容错性、部署在低廉的硬件上、易扩展性、提供高传输率访问数据的优点,但是在云存储环境下的HDFS架构中,原有的数据节点选择策略有可能造成大文件存储负载不均衡,从而影响整个系统的性能。针对这一问题,综合考虑多个因素对其进行改进,提出了设备选择策略算法,用以均衡系统的负载。并设计仿真实验,验证了算法的有效性。     

多元混合数据回归分析方法

针对加速寿命试验中经常遇到完全数据、定数截尾数据和定时截尾数据混合的情况,提出一种多元混合数据回归分析方法,建立了多元混合回归模型,给出回归系数和标准差的最佳无偏估计,以及百分位值的点估计和置信限估计.该方法不但适用于正态分布,而且还适用于Weibull分布、极值分布等其他各种位置-尺度分布,从而将传统只适用于完全数据...     

高职院校开展生命教育的有效途径探析

从高职院校的发展趋势和学生成长的现实要求分析了高职院校开展生命教育的必要性,从教师素养、课程开发、校园氛围三个方面阐述了高职院校开展生命教育的有效途径.     

Closed bioregenerative life support systems: Applicability to hot deserts

Water scarcity in hot deserts, which cover about one-fifth of the Earth’s land area, along with rapid expansion of hot deserts into arable lands is one of the key global environmental problems. As hot deserts are extreme habitats characterized by the availability of solar energy with a nearly complete absence of organic life and water, space technology achievements in designing closed ecological systems may be applicable to the design of sustainable settlements in the deserts. This review discusses the key space technology findings for closed biogenerative life support systems (CBLSS), which can simultaneously produce food, water, nutrients, fertilizers, process wastes, and revitalize air, that can be applied to hot deserts. Among them are the closed cycle of water and the acceleration of the cycling times of carbon, biogenic compounds, and nutrients by adjusting the levels of light intensity, temperature, carbon dioxide, and air velocity over plant canopies. Enhanced growth of algae and duckweed at higher levels of carbon dioxide and light intensity can be important to provide complete water recycling and augment biomass production. The production of fertilizers and nutrients can be enhanced by applying the subsurface flow wetland technology and hyper-thermophilic aerobic bacteria for treating liquid and solid wastes. The mathematical models, optimization techniques, and non-invasive measuring techniques developed for CBLSS make it possible to monitor and optimize the performance of such closed ecological systems. The results of long-duration experiments performed in BIOS-3, Biosphere 2, Laboratory Biosphere, and other ground-based closed test facilities suggest that closed water cycle can be achieved in hot-desert bioregenerative systems using the pathways of evapotranspiration, condensation, and biological wastewater treatment technologies. We suggest that the state of the art in the CBLSS design along with the possibility of using direct sunlight for photosynthesis and recent advances in photovoltaic engineering can be used as a basis for building sustainable settlements producing food, water, and energy in hot deserts.     

Fundamentals of Design and Technology of Rolling Element Bearings

This article presents an overview of fundamentals of rolling element bearing designs and technologies. The aim is to outline the complex interrelation of all fundamentals with the rolling contact fatigue and the attainable bearing life. Such fundamentals include, amongst others, bearing stressing and life capability. The article shows the different types of rolling bearing stressing and the analysis of the stress distribution (principal stresses and equivalent stresses) in the material under the rolling contact area. It becomes obvious that the contamination of the bearing with foreign particles leads to a drastic reduction in bearing life. Furthermore, it demonstrates the impact of the bearing lubrication and coating as well as the effect of additives on the attainable life and wear. Further fundamentals of rolling element bearing design are the materials, the material cleanliness and the heat treatment. The article reveals the importance of the cleanliness of bearing steels as well as different types of inclusions and their effect on rolling contact fatigue. Additionally the article describes how to optimize the material properties (strength, toughness and residual stress) by the heat treatment processes. The outcome of these investigations is that endurance life of a rolling element bearing can be achieved if specific operating conditions, an adequate lubrication, good system cleanliness and specific bearing stressing are met. The article provides a guideline for bearing engineers on how designs and technologies can be applied to optimizing a bearing for a particular industry or aerospace application.     

HP40奥氏体耐热钢炉管长期高温时效的安全性分析

为判别炉管的损伤程度和运行安全性,本文对运行了约46 000 h的苯乙烯生产加热炉炉管,在大修期间进行了宏观检查、氧化物的XRD(X-ray d iffraction)分析、管径测量、超声波测厚、硬度试验、金相组织分析及炉管的危险点计算分析等。实验结果表明:炉管表面发生了高温氧化以及碳化腐蚀,炉管壁厚明显减薄。与新管相比硬度也明显下降,显微组织明显退化,骨架状共晶碳化物形态消失,一次碳化物和从奥氏体晶内析出的二次碳化物明显粗化,且析出少量块状σ相。并在此基础上对炉管的剩余使用寿命作了估算。     

对搞好天津高校健康教育的初探

通过不同侧面说明在高校开展健康教育的意义，简要介绍了我市高校开展健康教育的现状，提出了促进我市高校开展健康教育的看法。     

THE SPACE APPLICATION ACHIEVEMENTS OF THE CHINESE UNMANNED SPACECRAFT "SZ-3"

During the 3rd mission of Chinese Unmanned Spacecraft the application sys tem of "SZ-3" (Shenzhou, a divine ship) gets a great success, all its goals are achieved. Many areas of science and breakthrough technology, including earth observation, earth environment monitoring, space material, space life science etc., are carried out in the mission. There are 44 payload instruments totally.All the instruments are working well during the orbit flight and a lot of good results are obtained. Many areas, for example the moderate resolution imag ing spectroradiometer, the solar ultraviolet spectral irradiance monitor and the space protein crystallization facility perform better than required and expected.A brief introduction of the experiments and the achievements of the mission is given in this paper.     

螺栓室温应力松驰试验研究

提出了一种改进的应力松弛试验方法，并用改进的装置测量了法兰接头紧固螺栓的室温应力松弛值，拟合了松弛方程曲线。根据螺栓应力松弛模型无温度变量的特点，利用Ｌ－Ｍ方法把温度引入了松弛模型，据此可推算在一定范围内革本温度和时间下的应务松弛指标。     

航空直流发电机用轴承的受力分析

对航空直流发电机所选用的轴承进行了受力分析、寿命计算和强度审核。此方法同样适合于航空直流起动发电机和交流发电机轴承的受力分析。