一类二次系统存在极限环的充分条件

在平面二次系统(Ⅱ)类方程形式为{dx/dt=-y δx lx^2 mxy ny^2 dy/dt=x(1 ax),(a≠0),的基础上做了一些研究．给出了当n=0,m=-a,l-aδ≠0时,二次系统(Ⅱ)类方程形式为{dx/dt=-y δx lx^2-axy dy/dt=x(1 ax),(a≠0)。存在极限环的一个充分条件。     

葡萄花油层高分辨率层序地层划分及沉积微相研究

应用岩心、测井、地震等资料,以高分辨率层序地层学原理为指导,并结合陆相湖盆层序地层特征,将他拉哈-常家围子地区葡萄花油层划分为1个长期基准面旋回,5个中期基准面旋回,25个短期基准面旋回,建立起该区葡萄花油层高分辨率层序地层格架.在岩心、测井曲线综合分析的基础上建立了该区测井相模式,并绘制相应沉积微相图.平面垂向相序及...     

最大度为6且不含4-圈和7-圈的平面图的边列表和全列表

令G是一个最大度为△(G)的平面图.运用Dischanging方法,进一步探究△(G)≥6的平面图的边列表色数,得到了最大度为6且不含4-圈和7-圈的平面图的边列表色数为△,全列表色数为△+1.     

干湿循环作用下石灰处治土强度特性试验研究

以广西膨胀土为研究对象,通过一系列室内试验获得了石灰处治膨胀土的胀缩性指标(最大干密度、最优含水量、自由膨胀率和黏粒含量)随掺灰比和龄期的变化规律.针对石灰处治膨胀土在特定恒温恒湿条件下进行了标准吸湿含水率试验,以探讨标准吸湿含水率检验膨胀土处治效果的适用性.考虑干湿循环效应及反复交通荷载的共同作用,分别开展了不同干湿循环次数后的处治土静、动三轴试验,研究了处治膨胀土静、动力学强度指标随干湿循环次数的变化规律,并对处治膨胀土在干湿循环作用下的破坏特征进行了分析.     

具有捕获的Beddington-DeAngelis功能性反应捕食-食饵模型极限环的存在唯一性

研究具有捕获的Beddington-DeAngelis功能性反应捕食-食饵模型。通过变量变换,将系统转换成一个性质更好的Gause型捕食-食饵模型,在适当条件下得到极限环的存在唯一性结果,补充T.K.Kar的结果。     

黑河中上游地区最高、最低气温非对称变化的时空特征分析

运用气候倾向率、趋势系数法、复值Morlet小波及Mann-kendall突变检测等方法,对黑河中上游地区1960-2009年最高、最低气温非对称变化的时空特征进行了分析．结果表明,近50a来,年和四季的平均最高、最低气温均呈明显增温趋势,最低气温空间上表现为由西北向东南方向依次递增,最高气温在流域东部和西南部为强增温区．年平均最高气温变化的突变点为1994年,最低气温变化的突变点为1989年．黑河中上游地区最高气温年变化具有明显的14a振荡周期,而最低气温主振荡周期为12a．     

Cycles of juvenile hormone esterase activity during the juvenile hormone-driven cycles of oxygen consumption in pupal diapause of flesh flies

Summary During diapause O₂ consumption in fly pupae is a cyclic event (4-day periodicity at 25°C) driven by cycles of juvenile hormone activity. Levels of juvenile hormone esterase activity change systematically during the cycle, with highest activity observed at the nadir of the O₂ consumption cycle.Supported in part by grant 88-37153-3473 from the USDA Competitive Grants Office and grant 23-088 from the USDA Forest Service. Thanks to Dr Ming Tu Chang for her helpful advice.     

A spontaneous benomyl-resistant mutant ofPodospora anserina exhibiting a diurnal growth rhythm

Summary A spontaneous mutant ofP. anserina isolated by screening for benomyl resistance exhibited a diurnal growth rhythm dependent on light-dark cycles. The rhythmic character, the benomyl resistance and a growth rate reduced to 50% of that of the wild type were inherited together over more than 10 generations. The locus was mapped on linkage group II, 0.35 map units distal to the locusz (=0.81 map units from the centromere).     

International interdependence of business cycles in the manufacturing industry: The use of leading indicators for forecasting and analysis

This article introduces new leading indicators for fifteen industrialized countries which enable the business cycle in manufacturing to be forecast fairly reliably between 4 and 6 months ahead. These indicators are based on an improved variant of the NBER method, yielding a composite leading indicator characterized by less erratic movements and clear turning points. The indicators are used to explore the international interdependence of business cycles and to examine the degree to which this interdependence is affected by growing economic integration, as in the EC. For each of the countries studied, the various foreign economies affecting the local business climate are identified. Since the business cycles of some countries clearly lead those of others, this international interdependence can be used to further improve the predictive power of the leading indicators in the lagging countries.