大鸨的濒危机制及保护对策

基于大鸨(Otis tarda)的一系列野外研究数据,从内因和外因两个方面探讨了大鸨的濒危机制,并提出相应保护对策.大鸨的濒危内因主要体现为繁殖力低下、变通性差和行为表现上的神经质;外因主要体现在人为干扰和破坏上,人为无节制的活动导致大鸨繁殖成功率下降、生境片断化和生境质量退化.因此提出保护对策如下:严格控制并约束草原上的人为活动,尽可能保证大鸨栖息生境的优质化和完整化;加强人工繁殖及野化实验,壮大野生种群.     

微热光电系统燃烧室内突扩台加工位置的选择

通过实验找出微热光电系统燃烧室在最优影响因素下的各测温点的温度值,用灰色系统理论对其建立灰色预测模型,预测最高温度值所处位置.由普朗克定律可知:温度值的高位变动对辐射力产生的影响要比低位变动大.突扩台加工位置从壁面温度的最高点处开始,既增加了微热光电系统燃烧室外壁面最大温度值,又减缓了壁面温度的最大值到出口处的温度分布,对提高微型热光电系统的热电转化效率有显著作用.     

沿空掘巷预留煤柱宽度及支护方案的优化设计研究

煤柱留设宽度和位置合理与否,直接关系到本层位蝶层在回采过程中煤柱受力状态,所选择的巷道支护方式对巷道围岩的稳定性有决定性的影响。本文通过数值模拟,计算优化确定了预留煤拄的合理范围以及巷道锚杆支护方案与具体参数。     

Obtaining the best possible predictions of habitat selection for wintering Great Bustards in Cangzhou,Hebei Province with rapid machine learning analysis

Great Bustards （Otis tarda dybowskii） are one of the world＇s heaviest flying birds, occupying grassland hab- itats in Eastern Asia. Our study is located at the most eastern Chinese wintering site in Cangzhou, Hebei Province, where approximately 100 individuals are concentrated in a small area （17.53 km2）. Solid information is still lacking about the wintering areas for this subspecies in its eastern range and specifically for China. The study area consists of intensely used farmland in proximity to humans and is lacking con- servation areas and wild, open fields. Here, we present our results from two years of field data collection on habitat selection. We choose a machine learning model approach based on a rapid assessment methodology for the winter habitat of the Great Bustard. It is based on a spatial analysis of the best available environmental data, which were col- lected relatively quickly. These relatively new methods in ecology are based on an ensemble of decision trees and include algorithms such as TreeNet, Random Forest and CART used in parallel. In this study, we collected bustard droppings （presence only） from 48 locations between December 2011 and January 2012 and used the sites as training data. Droppings from 23 locations were collected in November 2012, and those sites were used as test data. We used eight environmental variables as predictor layers for the response variable of bustard presence/availability. We employed a Geographic Information System （ArcGIS 10.1and Geospatial Modelling Environment） and Google Earth. Compared with the other three models, we found that pre- dictions from Random Forest obtained a significant differ- ence between presence and absence. According to this model, the three most important factors for wintering Great Bustards are distance to residential area, distance to water pools, and farmland area. Our model shows that wintering Great Bustards prefer locations that are over 400 m away from residential areas, within 900 m of water pools and on areas o     

兰新线即有土堤式挡风墙的改造形式对背风侧流场的影响

为了研究兰新线即有土堤式挡风墙的挡风性能,寻找即有土堤式挡风墙不能满足列车安全运行的原因及解决方法,本文应用数值模拟以及分析实测数据的方法得到即有土堤式挡风墙背风侧的流场特性,并为即有土堤式挡风墙的改造提出2种方案,分析对比3种优化改造后土堤式挡风墙在不同风速下背风侧的特征线风速、流场结构、大风遮蔽效应系数。结果表明:即有土堤式挡风墙背风侧无明显涡流区,挡风性能不满足列车安全运行的要求,相对于即有土堤式挡风墙,改造后土堤式挡风墙在不同风速下左侧加高、中部加高、右侧加高土堤式挡风墙挡风性能差异小,但挡风性能均有明显提高,均能满足列车安全运行的要求。优化改造后的土堤式挡风墙为将来类似防风沙工程优化设计提供参考和依据。     

徽派建筑马头墙的文化意蕴浅析

微派建筑一般以青瓦白墙、高墙深院及天井飞檐为典型特征,其中又以高于两山屋面的墙垣--“马头墙”最为抢眼。从历史渊源,文化渐染,实用美观和文化寓意四个角度对之进行解析,有助于相关学者挖掘隐藏于这一建筑现象背后的深层文化内涵。     

雅礼大学预科办学的精英化透视

清末由外国差会雅礼会创办的雅礼大学堂是一所由美国耶鲁大学毕业生直接创办的大学预科学校。雅礼大学预科办学过程中,从培养目标、生源师资到课程设置,都渗透着精英化的教育思想。这不仅成就了雅礼大学后来精英化的生源基础,也铸就了雅礼精英化的中等教育,为那个时代输送了大量的社会精英。     

《墙上的斑点》:女性主义视角下的修辞设计

《墙上的斑点》作为英国作家弗吉尼亚·伍尔夫的第一篇意识流小说而倍受关注。作为女性主义思想家的伍尔夫,致力于用写作来争取女性话语权。《墙上的斑点》通过对叙述视角、关键词及幻象进行精心修辞设计,成功传达了女性的声音。