基于坡度率的再入飞行器在线轨迹规划

为了实现再入飞行器轨迹快速生成,提出了一种在线轨迹规划方法。利用改进的拟平衡滑翔条件,提出了坡度率的概念。通过设计坡度率,可获得不同航程的纵平面弹道。为了加大航程的调节范围,在基于坡度率的纵向轨迹规划方法基础上,引入了倾侧角,同时规划坡度率和倾侧角可以获得较大范围的航程覆盖区。飞行器航程跟坡度率、倾侧角、初始航向误差角、飞行时间存在对应关系。离线计算若干条不同工况的轨迹并存盘,当给定新的目标点时,只需计算出目标点距离初始点的航程和目标视线角,通过插值得到所需的坡度率、倾侧角、航向误差角和飞行时间,然后利用轨迹积分,能够快速获得一条完整的三自由度轨迹。仿真表明,利用本文的方法,生成一条实际飞行时间2000 s的再入轨迹,只需要0.2 s左右,极大地提高了在线轨迹设计效率。

Barton-Bandis criterion-based system reliability analysis of rock slopes

Several potential failure modes generally exist in rock slopes because of the existence of massive structural planes in rock masses. A system reliability analyses method for rock slopes with multiple failure modes based on nonlinear Barton-Bandis failure criterion is proposed. The factors of safety associated with the sliding and overturning failure modes are derived, respectively. The validity of this method is verified through a planar rock slope with an inclined slope top and tension crack. Several sensitivity analyses are adopted to study the influences of structural-plane parameters, geometric parameters, anchoring parameters and fracture morphology on the rock slopes system reliability.

Organic carbon losses by eroded sediments from sloping vegetable fields in South China

Soil Organic Carbon （SOC） is the most important component of soil. Though small, it determines soil fertility and prevents soil losses. In this study, we examined relationships between the Particle-Size Distribution （PSD） of the eroded sediment and SOC loss, and evaluated the effects of plant coverage ratios （0%, 15%, 30%, 45%, 60% and 90%）, slope lengths （2 m, 4 m）, fertilizer treatments （unfertilized control （CK）, compound N-P-K fertilizer （CF）, and organic fertilizer （OF）） on SOC loss and the SOC enrichment ratio （ERsoc） in the eroded sediments. The experimental results showed that longer slope length and lower surface cover ratios produced larger surface runoff and the eroded sediments, resulting in larger SOC losses. The average SOC loss was greatest in the OF treatment and SOC loss was mainly associated with the eroded sediment. Surface runoff, which causes soil erosion, is a selective transportation process, hence there were more clay- sized particles （〈2 μm） and silt-sized particles （2-50μm） in the eroded sediments than in the original soils. SOC was enriched in the eroded sediments relative to in the original soil when ERsoc 〉 1. ERsoc was positively correlated with ERclay （〈2 pro） （R^2 = o.68） and ERie at （2-20 μm） （R2 = 0.63）, and from all the size particle categories of the original soil or the eroded sediments, more than 95% of SOC was concentrated in small-sized partieles （〈50 μm）. The distribution of SOC in different-sized particles of the original soil and the eroded sediment is primarily associated with clay-sized part-ides and fine silt-sized particles, thus we eonelude that as the eroded sediment partieles became finer, more SOC was absorbed, resulting in more severe SOC loss.

The Application of High-density Resistivity Method to the Evaluation on the Stability of Gongchangling Open Pit＇s Slope

High-density resistivity method is a new, efficient electrical prospecting method, which can complete a two-dimensional （vertical and horizontal） prospecting process, possesses certain imaging functions for the geo-electric structure, and integrates electric profiling method with electric sounding method together. In this paper, the basic principle, data processing, and result explanation and inference of high- density resistivity method are introduced by taking the application of high-density resistivity method to the prospecting project in the slope of Gongchangling Open Pit, Liaoyang. The result of the prospecting result map analysis showed that the prospecting result was basically in line with the actual situation and proved the great significance of high-density resistivity method to the evaluation on the slope stability of Gongchangling open pit.

Effects of a sex ratio gradient on female mate-copying and choosiness in Drosophila melanogaster

In many sexually reproducing species, individuals can gather information about potential mates by observing their mating success. This behavioral pattern, that we call mate-copying, was reported in the fruit fly Drosophila rnelanogaster where females choosing between 2 males of contrasting phenotypes can build a preference for males of the phenotype they previously saw being chosen by a demonstrator female. As sex ratio is known to affect mate choice, our goal was to test whether mate-copying is also affected by encountered sex ratios. Thus, we created a gradient of sex ratio during demonstrations of mate-copying experiments by changing the number of females observ- ing from a central arena 6 simultaneous demonstrations unfolding in 6 peripheral compartments of a hexagonal device. We also tested whether the sex ratio experienced by females during demon- strations affected their choosiness （male courtship duration and double courtship rate） in subse- quent mate-choice tests. Experimental male：female sex ratio during demonstrations did not affect mate-copying indices, but positively affected the proportion of both males courting the female during mate-choice tests, as well as male courtship duration, the latter potentially explaining the for- mer relationship. As expected, the sex ratio affected female choosiness positively, and Drosophila females seem to have evolved a mate-copying ability independently of sex ratio, and a capacity to adapt their choosiness to male availability. This suggests that, as in many animal species, individuals, especially females, can adapt their mate choice depending on the current sex ratio.