低渗透砂岩石油渗流的微观模拟实验研究

采用天然低渗透砂岩微观模型，通过与实际地质状况较为相似条件下的油驱水实验，模拟石油在低渗透砂岩孔隙内的渗流，分析和探讨了低渗透砂岩孔隙介质中石油的微观渗流机理。研究结果表明，石油在低渗透砂岩中渗流路径曲折复杂，运移渗流模式有稳定式、指进式和优势式3种；石油在低渗透砂岩中渗流存在启动压力梯度，启动压力梯度与砂岩孔隙度关系复杂，而与砂岩渗透率有很好的相关性；石油的渗流速度与驱替压力呈很好的相关性，石油以相同速度在不同渗透率级别的砂岩内渗流时所需要的驱替压力随砂岩渗透率的增大而降低。     

Detection of jump location curve in spatial linear regression model with two-dimensional threshold

In the context of spatial linear regression, we discuss detection of jump location curve treated as threshold curve which cannot be expressed by independent variables but indirectly determines two specific model forms. The threshold curve in this paper is described by a straight line with two location variables, longitude and latitude, and can be estimated by maximizing the coefficient difference between two one-sided linear regression models. Theoretical results show that the estimator is consistent. Our method performs well by numerical studies.     

Threshold Conditions for the Persistence of Plague Transmission in Urban Rats

In this article we derive a mathematical expression characterizing the tendency for Yersinia pestis, the etiologic agent of plague, to become established in an urban rat population upon introduction, and evaluate this risk for several cities. The expression gives a threshold condition for the persistence of Y. pestis transmission in terms of measurable attributes of a local urban rat population: the average flea density and the rat colony size. If the local rat and flea populations exceed this threshold, plague circulation is predicted to continue; if not, it will burn out of its own accord. This expression may be used to evaluate both the vulnerability of a specific neighborhood and the effect of pest control strategies upon that vulnerability.     

Extreme behaviour for bivariate elliptical distributions

The authors examine the asymptotic behaviour of conditional threshold exceedance probabilities for an elliptically distributed pair (X, Y) of random variables. More precisely, they investigate the limiting behaviour of the conditional distribution of Y given that X becomes extreme. They show that this behaviour differs between regularly and rapidly varying tails.     

中师学生体育炼身运动负荷标准探讨

运用现代科学体育方法学的基本原理———炼身运动负荷价值阈 ,在中师体育教育实践中进行实验研究 ,以求全面提高中师体育教育教学质量     

具有依赖于总人数的有效接触率的生态-传染病模型

研究了具有依赖于总人数的有效接触率的生态-传染病模型.建立了一个具有依赖于总人数的有效接触率的模型,在模型的不变子集上先求出阈值R0的表达式.如果R0≤1,则疾病消除平衡点全局渐近稳定;如果R0>1,则存在唯一的传染病平衡点,且是全局渐近稳定的.对带有双线性传染率和标准传染率的两个模型作了相应的讨论.     

中国金融发展与经济增长门限效应的实证研究

采用门限模型对中国金融发展与经济增长之间的非线性关系进行了相关研究.实证结果表明金融发展与经济增长之间虽然存在门限效应,但门限模型表明除股票市场外无论是金融发展处于较高水平还是较低水平,中国金融发展与经济增长之间表现为负相关关系,这说明中国金融发展抑制了经济增长,同时也验证了中国现阶段金融发展与经济增长之间仍为线性关系.     

基于阈值分割的数学形态学道路标识线检测

针对边缘检测算子对噪声敏感的缺点,提出了一种新的基于阈值分割的形态学道路标识线的检测方法.仿真结果表明,这种方法保留了更多的图像细节,具有更强的去除噪声能力,可以有效地从道路图像中检测道路标识线.     

重庆市农民收入与工业化的区域差异及阈值效应研究

为了能更准确地把握区域工业化发展给农民收入带来的影响,综合运用计量经济学方法研究了重庆市农民收入与工业化之间的非线性关系。结果发现：重庆市农民收入水平存在连片集聚现象,区域间工业化发展极不平衡,且二者之间不存在长期均衡的协整关系,工业化水平的提高并不能带来农民收入的长期持续增长。工业化对农民收入的影响具有双面阈值效应,在不同工业化阶段,对农民收入的影响弹性先快速增加后逐渐减弱;在不同区域,工业化的影响呈现出倒“U”和“U”两种类型。