Across-shore distribution of Ocypode quadrata burrows in relation to beach features and human disturbance

Spatial distribution patterns of the ghost crab Ocypode quadrata were analysed using different approaches at one disturbed and two preserved reflective sandy beaches of the Mexican Caribbean. We used spatial correlation analysis to describe the across-shore distribution of O. quadrata and their patch dynamics by beach and sampling time. In addition, we analysed the across-shore variability of habitat extent of O. quadrata (habitat envelope) and its relation to human disturbance and beach features. The spatial structure of burrow density was consistent through time, showing a bimodal distribution with very low abundance in the mid distribution range and a discrete increment of burrows to landward. Nonetheless, the size of patches varied temporally for the three beaches. Burrow size increased from seaward to landward. The location of the first burrow and the habitat envelope varied among sampling times and beaches. The location of the first burrow is mostly mediated by the swash climate, while the habitat envelope is mainly controlled by the level of human disturbance. Despite the low number of disturbed and control beaches, our results suggest that the habitat envelope could be included in future studies when using ghost crabs as indicators of human disturbance. Polynomial models and variographic analysis proved to be useful tools to describe the across-shore distribution and patch dynamics of the ghost crab.     

一类超前型差分方程振动的充分必要条件

讨论了形如ｘｎ＋－ｘｎ＋ｐｘｎ＋ｒ＋ｑｘｎ＋ｎ＋δ＝０的差分方程的振动性，得到了用ｐ，ｑ，ｒ，τ，α，δ表示的该类方程振动的充分必要条件。     

Adaptive augmentation of gain-scheduled controller for aerospace vehicles

This paper proposes an adaptive augmentation control design approach of the gain-scheduled controller.This extension is motivated by the need for augmentation of the baseline gainscheduled controller.The proposed approach can be utilized to design flight control systems for advanced aerospace vehicles with a large parameter variation.The flight dynamics within the flight envelope is described by a switched nonlinear system,which is essentially a switched polytopic system with uncertainties.The flight control system consists of a baseline gain-scheduled controller and a model reference adaptive augmentation controller,while the latter can recover the nominal performance of the gainscheduled controlled system under large uncertainties.By the multiple Lyapunov functions method,it is proved that the switched nonlinear system is uniformly ultimately bounded.To validate the effectiveness of the proposed approach,this approach is applied to a generic hypersonic vehicle,and the simulation results show that the system output tracks the command signal well even when large uncertainties exist.     

Effective envelope method for Stewart platform workspace

The workspace of Stewart platform is the intersection of 6 son workspaces of 6 loop chains, so it is important to determine the boundary of the son workspace when locating the boundary of the son workspace. An effectivc envelope method is proposed in this paper. Firstly the envelope theory of a family of singular parameter curve surfaces is used to find the envelope surfaces of the son workspace. Then the numerical method is applied to determine the effective envelope surface. And after that the full boundary of the son workspace, which is the envelope of the effective envelope surfaces, is determined. Finally the workspace can be obtained with a section plane method.     

Will future anthropogenic climate change increase the potential distribution of the alien invasive Cuban treefrog (Anura: Hylidae)?

The invasive alien Cuban treefrog Osteopilus sepentrionalis is native to Cuba, the Bahamas and some adjacent islands. It was accidentally introduced to Florida, Puerto Rico and some Hawaiian islands, where it has become a predator and competes with native wildlife. We have used a maximum entropy ecological niche modelling approach to model its potential spread derived from current climate conditions as present in its native geographic distribution and we project that model into future climate change scenarios in order to detect new areas that are potentially threatened. Our model, applying current climatic conditions, suggested high probabilities of occurrence in countries around the Gulf of Mexico. Projections of potential distribution under future anthropogenic global warming scenarios suggest an overall extension of the potential distribution. If the predictive maps are interpreted as depicting the invasive potential of O. septentrionalis, strategies to prevent further invasion should focus on biosafety measures within the areas highlighted.     

动物细胞间信息传递系统

讨论了激素，第二信使系统，糖蛋白等信息物质在动物有机体内的相互作用，共同形成了细胞间的信息传递系统。     

成形磨齿砂轮包络计算的双参数点矢量族法

成形磨齿砂轮母线一般为多段直线、圆弧构成的组合曲线,砂轮扫掠体包络面的计算远比常规回转刀具复杂.双参数点矢量族包络法,将砂轮母线上离散点及其法向矢量定义为点矢量且每个点矢量唯一对应着一个虚拟球,点矢量的回转运动生成纬线圆,点矢量包络运动等效生成过球心的截圆,纬线圆与截圆的交点即为特征点;建立了特征点的解析计算模型,特征点由虚拟球几何参数及虚拟球心速度决定,虚拟球几何参数可直接采用点矢量信息计算;分析了典型五轴成形磨齿机的运动几何特性,进行了磨齿机惯性坐标架与活动坐标架的坐标变换,给出了基于磨齿数控代码的虚拟球心速度计算方法;通过1个计算实例验证了文中方法的有效性.该方法可用于五轴成形磨齿的几何仿真、精度评估及路径优化中.     

基于PXI平台功率放大器的包络整形技术

包络跟踪功放与固定电源供电的功放系统不同的是,系统的性能不仅仅与射频输入信号有关,还与包络输入信号有关.将基于PXI平台的同步定时技术进行系统级分析,并讨论固定增益法等不同包络整形技术对于功放效率和线性度等系统性能指标的取舍.另外,还提出了一种新的针对电源调制模块的校准方法.     

缺陷对连续油管极限承载能力影响分析

针对含有缺陷连续油管作业过程中极易发生卡断或拉断等事故,根据现场使用后的连续油管缺陷情况,把缺陷形状归为方形、球形和椭球形三种缺陷,并开展拉伸内压复合载荷工况下连续油管承载能力的研究。对比分析不同尺寸不同形状下含缺陷连续油管应力分布规律,在此基础上绘制轴向载荷(n=N/N_0)与内压载荷(p=P/P_0)包络线,通过现场数据直接判断连续油管是否在安全工作范围。通过有限元计算结果与API5C5标准计算结果验证有限元法的有效性和精确性。在此基础上开发含缺陷连续油管安全评估软件,获得不同型号不同缺陷形状情况下轴向载荷与内压载荷的包络线,为油田现场连续油管安全施工提供保障。     

基于测井曲线相关系数及包络面积的流体识别方法

孔隙度测井及电阻率测井的相关系数及其包络面积大小对储层的响应特征非常敏感,相对于水层,油层相关系数的会明显增大,包络面积也会明显增大。利用相关系数和包络面积的这一反向变化特征,在同一曲线道中合理刻度归一化后的相关系数和包络面积曲线,可以形成明显的镜像包络线。通过计算相关系数及包络面积并结合试油试采数据可以得到用于定量识别油水层的关系图版。该方法在油砂山油田第三系砂泥岩储层的油层识别中,取得了良好的判识效果,拓宽了工区利用测井资料识别复杂储层流体性质的途径。