土岩复合地层中深基坑开挖对邻近管线变形影响分析

为探究土岩复合地层中深基坑开挖对邻近管线变形的影响规律,开展了土岩复合地层中深基坑开挖的现场监测和数值模拟研究.以南京地铁一号线北延工程二桥公园站车站基坑为工程依托,基于现场实测数据进行了管线沉降变形分析,并使用PLAXIS 3D有限元分析软件进行数值模拟,揭示了管线与基坑间距、管线埋深等因素对管线变形的影响规律,并定...     

量子信道对纠缠鲁棒性的影响

考虑量子信道对多体纠缠鲁棒性的影响. 先根据可分态之集为一个凸闭集, 证明可以取到纠缠鲁棒性定义中的下确界, 再证明同一纠缠态ρ的两个最优态的凸组合仍是最优态, 纠缠鲁棒性作为定义态集合上函数是下半连续的; 最后, 分别给出一个量子信道不增加、 不减少[KG*8]及保持所有量子态的纠缠鲁棒性的充分必
要条件.     

塔河油田4区岩溶缝洞型储层及其控制因素*

塔河油田4区下奥陶统碳酸盐岩储层以溶洞、溶孔和裂缝为主,溶洞是最有效的储集体,裂缝次之。基质孔渗性极差,难以构成有效的储集空间。受海西早期构造运动的影响,研究区发育北北东、北北西以及北东向3个方向的裂缝。综合岩芯岩溶特征描述、电子探针元素分析以及同位素分析等方面的研究,发现研究区发育4期岩溶作用,其中加里东中晚期与海西早期的岩溶作用对研究区溶洞的形成起到了重要的控制作用。岩溶地貌控制了缝洞型储集体的分布,处在不同岩溶相带的古水系对缝洞体形态产生影响,断裂及其伴生裂缝增加了地表水及地下水与碳酸盐岩的接触面积和溶蚀范围,使得研究区内放空漏失井90%集中在断裂带附近,断裂带是裂缝与岩溶发育的密集带。     

Preliminary results pertaining to coseismic displacement and preseismic strain accumulation of the Lushan M S7.0 earthquake, as reflected by GPS surveying

This paper presents the coseismic displacement and preseismic deformation fields of the Lushan M _S7.0 earthquake that occurred on April 20, 2013. The results are based on GPS observations along the Longmenshan fault and within its vicinity. The coseismic displacement and preseismic GPS results indicate that in the strain release of this earthquake, the thrust rupture is dominant and the laevorotation movement is secondary. Furthermore, we infer that any possible the rupture does not reach the earth’s surface, and the seismogenic fault is most likely one fault to the east of the Guanxian-Anxian fault. Some detailed results are obtainable. (1) The southern segment of the Longmenshan fault is locked preceding the Lushan earthquake. After the Wenchuan earthquake, the strain accumulation rate in the southeast direction accelerates in the epicenter of the Lushan earthquake, and the angle between the principal compressional strain and the seismogenic fault indicates that a sinistral deformation background in the direction of the seismogenic fault precedes the Lushan earthquake. Therefore, it is evident that the Wenchuan M _S8.0 earthquake accelerated the pregnancy of the Lushan earthquake. (2) The coseismic displacements reflected by GPS data are mainly located in a region that is 230 km (NW direction) × 100 km (SW direction), and coseismic displacements larger than 10 mm lie predominantly in a 100-km region (NW direction). (3) On a large scale, the coseismic displacement shows thrust characteristics, but the associated values are remarkably small in the near field (within 70 km) of the earthquake fault. Meanwhile, the thrust movement in this 70-km region does not correspond with the attenuation characteristics of the strain release, indicating that the rupture of this earthquake does not reach the earth’s surface. (4) The laevorotation movements are remarkable in the 50-km region, which is located in the hanging wall that is close to the earthquake fault, and the corresponding values in this case correlate with the attenuation characteristics of the strain release.     

Positronium annihilation in oxygen and nitrogen mixture

Formed in silica aerogels, positronium annihilation in oxygen and nitrogen mixture is studied by a simple and convenient method. The results show that ortho-positronium (o-Ps) lifetime is significantly shortened when some oxygen is introduced into nitrogen gas and that the o-Ps collisional quenching rate for an oxygen molecule is (28.0±0.4) μs^?1·amagat^?1 (1 amagat = 2.69×10²⁵ m^?3). It is found that the o-Ps annihilation rate in oxygen of 1atm at room temperature is (25.5±0.5) μs^?1 and that the effective number of electrons per oxygen molecule available for 2γ annihilation of positron in the o-Ps is (34.6±0.4).     

基于Hopkinson杆技术的混凝土动态压缩性能研究

采用分离式Hopkinson压杆对混凝土试件(D=74mm)进行了动态压缩试验,得到了不同应变率下的混凝土动态抗压强度,研究了它的率敏感性,并得到了相应的临界应变率。结果表明:随着试件中应变率的增大,混凝土的动态抗压强度相应有不同比例的增加;同时在试验的基础上,分析了应变率对混凝土抗压强度的影响。抗压强度在相应的应变率超过一定值后会有一个较大比例的增加,抗压强度的临界应变率大约是40s-1。     

基于RS和GIS的城市建设用地监测模型构建与验证研究——以重庆市南岸区为例

以重庆市南岸区为例,基于RS和GIS的地理技术,建立了城市建设用地监测模型,以精确监测和预测城市新增建设用地的变化趋势,为区域土地利用及土地监察提供理论和技术指导,研究发现:利用RS与GIS的平台可以构建用于监测城市新增建设用地动态变化的模型,适时监测某区域内城市新增建设用地情况,并直观地反应在RS影像上,其监测精度可以通过相同监测方法对不同区域的监测进行合理验证.     

大口径天线伺服系统的建模及控制算法设计

在大口径天线伺服系统存在高频未建模动态不确定性和低频风扰动的情况下,传统的PID控制算法无法满足天线伺服系统的高指向和跟踪精度要求.针对该问题,文中设计了一种基于灵敏度函数和补灵敏度函数的、兼顾系统性能和稳定性的混合灵敏度H_infinity控制算法,并将其应用于天线伺服系统.仿真结果表明,该算法不仅能显著提高天线伺服系统的动态性能,而且具有较强的扰动抑制能力和鲁棒性.     

框架-核心筒超限高层结构的抗震性能评估

以结构整体地震响应、材料应变、主要受力构件变形作为抗震性能评估指标,从结构整体和局部的地震响应层面上,综合考察结构的抗震性能.以某体型不规则、高度超限的框架-核心筒超高层结构为研究对象,利用Perform3D非线性软件对该结构进行非线性动力时程分析.分析结果表明:结构整体变形满足规范要求;各主要受力构件变形性能处于基本完好状态,仅位于结构平面缩进处的剪力墙和框架梁发生较大弹塑性变形,但其平均变形仍处于基本完好状态.基于结构整体与局部构件抗震性能评估可知,该框架-核心筒超高层结构满足抗震性能指标要求.