拉压、扭转载荷下铸铝合金的亿周疲劳性能研究

应用超声疲劳试验机对铸铝合金2-AS5U3G-Y35在扭转和拉压循环载荷下进行了超高周疲劳性能测试.介绍了超声扭转疲劳试验装置的设计.应用35 Hz常规疲劳试验机和20 kHz的超声疲劳试验机完成应力比R=-1的拉压、扭转疲劳试验,进而研究不同载荷条件、加载频率对铸铝合金超高周疲劳性能的影响.S-N曲线显示,铝合金在105～1010疲劳周次间仍发生疲劳断裂,不存在疲劳极限.断口分析表明,在超高周循环拉压载荷下,疲劳裂纹常萌生于试样次表面材料内部缩孔.与循环拉压载荷下的疲劳断裂机理不同,在循环扭转载荷下疲劳裂纹主要萌生于试样表面,疲劳断裂面为一种典型的沿试样轴向45°的螺旋面,即沿最大主应力平面断裂.扭转疲劳断面清晰的剪切条带表明扭转疲劳断裂实质上是剪切断裂.     

照射系统故障树的建造及BITE检测点的设置

遵循ＧＪＢ７６８．１提供的方法。以某型雷达为例，探索建造照射系统故障树的方法，阐明取顶事件的角度，故障定义，建树假设等问题，并对其ＢＩＴＥ检测点的设置作了评述。     

片梭织机卷取辊涂布金刚砂的研制

介绍了片梭织机卷取辊涂布金刚砂的制造工艺，并对制造工艺进行了讨论。     

A biophysical model for estimating the frequency of radiation-induced mutations resulting from chromosomal translocations.

Gene mutations can be induced by radiation as a result of chromosomal translocations. A biophysical model is developed to estimate the frequency of this type of mutation induced by low-LET radiation. Mutations resulting from translocations are assumed to be formed by misrejoining of two DNA double strand breaks (DSB), one within the gene and one on a different chromosome. The chromosome containing the gene is assumed to occupy a spherical territory and does not overlap spatially with other chromosomes. Misrejoining between two DSB can occur only if the two DSB are closer than an interaction distance at the time of their induction. Applying the model to mutations of the hprt gene induced in G0 human lymphocyte cells by low-LET radiation, it is calculated that mutations resulting from translocations account for about 14% of the total mutations. The value of the interaction distance is determined to be 0.6 micrometers by comparing with the observed frequency of translocations in the X-chromosome.     

阈值温度,临界能量与航天器带电特性

采用加权求和方法确定不同能量入射电子对应不同次级(二次发射和反向散射)电子产率公式,用来计算航天材料高压带电的阈值温度T~* 和临界能量E~*,得到了与观测数据较为接近的临界带电特性。文中进一步阐明运用T~* 和E~* 两个概念,可以定性解释航天器带电的复杂特性。     

Maximum likelihood identification of glint noise

If the non-Gaussian distribution function of radar glint noise is known, the Masreliez filter can be applied to improve target tracking performance. We investigate the glint identification problem using the maximum likelihood (ML) method. Two models for the glint distribution are used, a mixture of two Gaussian distributions and a mixture of a Gaussian and a Laplacian distribution. An efficient initial estimate method based on the QQ-plot is also proposed. Simulations show that the ML estimates converge to truths     

跨声速欧拉方程的一种隐式有限元解法

本文用有限体积Ｇａｌｅｒｋｉｎ法求解了跨声速二维欧拉方程。求通量运用了Ｏｓｈｅｒ格式，通过外插把原来只有一阶精度的逆风格式改进成二阶精度。并采用基于一性化流量的隐式格式和非结构化网格，使程序具有较高的收敛效率。     

大型百货商场应急疏散措施安全性评价初探

大型百货商场应急疏散措施对减轻事故发生后的严重后果极其重要,因而有必要对其进行安全评价以确保其在事故发生时能正常发挥其功能.本文首次提出了商场应急措施安全评价方法,给出了简单实用的安全评价及安全评价规则,对商场建筑设计、消防管理、安全管理等都有一定的参考价值.     

高精度双星快速定向方法研究

采用转动基线的方法解决利用“北斗”卫星载波相位进行定向的关键技术问题——初始相位整周模糊度的确定,并进行了仿真实验,结果表明:当原始载波相位观测精度优于2％周时,利用2m基线在5min时间内可达到方位0.01°的定向精度.     

Measurements of upper atmosphere wind and temperature from meteorological rocket experiments during winter 1979

This institute conducted a series of meteorological rocket experiments for the upper-atmospheric sounding in the winter of 1979. Within the overlap altitude range with balloon flights, a comparison of the results with the standard radiosonde data indicated that the rocket-borne system was reliable. The measurements from foru rocket flights for the region between 20 and 30 km showed a degree of compatibility to each other while those for above 30 km differed considerably from one another. At low latitude, the temperature profiles in the winter stratosphere in general showed a reasonably good agreement with the U.S. Standard Atmospheric Supplements, 1966 (USSAS 66). A temperature of 2–24°C lower than the USSAS 66, however, was recorded in the lower mesosphere. Above 30 km the maximum diurnal variation in temperature was 9°C or so. In the winter, the wind profile showed the westerlies and the maximum wind velocity of 92.1 Msec^?1 was obtained from these experiments at the height of 60 km.