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141.
Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investment. By the analysis of the conceptions of risk and return, together with the three hypotheses of technological analysis, a novelty model of metering and evaluating the risk and return of stock investment is established. The major indicator of this model , risk-return ratio K, combines the characteristic indicators of risk and return. Regardless of the form of the risk-return probability density functions, this indicator K can always reflect the risk-return performances of the invested stocks clearly and accurately. How to use the model to make optimum investment and how to make portfolio combined with clustering analysis is also explained. 相似文献
142.
A group of grafted PET fibers with different graft yield are formed by grafting acrylamide onto the PET main chains. The structure of grafted fibers are studied by scanning electronic microscope ( SEM ), infra-red spectrophotometer ( IR ), and differential scanning calorimetry(DSC). At the same time, the moisture regain, dyeability, strength, and elongation at break of the samples are measured and their relations with structural changes are discussed. Compared with ungrafted fiber, shape of the fiber cross-section, IR characteristic absorption peaks, and melting behavior of the grafted fibers have been changed, causing the fiber dyeability and moisture regain to be increased, and mechanical properties to be changed. 相似文献
143.
A set of new current sensing device is used to realize joint torque control based on current measurement in a precision assembly robot's third joint. The output torque's model of the joint's brushless DC motor is founded. Disturbance factors and the compensated effect of the torque's closed loop based on current measurement are analyzed. Related simulations and experiments show that the system has good current tracking and anti-disturbances performance, which improve the force control performance of the robot in assembly. 相似文献
144.
With layer-measured contours, an algorithm that can extract the contour segments from a rotational surface is presented. The extraction can be divided into two stages, i. e. the rough segmentation and the refinement. In the rough segmenting stage, an optimal contour matching method is put forward to find similar contour segment from another closed contour with respect to the seed contour. In the refining stage, an iterative way that can extract a circular arc precisely is presented based on parameters identification and contour-ends expanding/shrinking operation. The algorithm can extract the open contour segments from a rotational surface precisely, as demonstrated in the examples. Based on the work of this paper, further research, such as parameter identification of 3 - D surface and CAD model creation, can be conducted. 相似文献
145.
A novel hyper-redundant manipulator named RT1 is designed and studied. The unique feature of RT1 is all degrees of freedom (DOF) are actuated with only one motor via special designed hinge bar universal joints. The mechanisms of RT1 are introduced in detail. Some experiments are carried out in order to test the movability and adaptability of the manipulator. RT1 is actuated by pulse string and acts discretely. The discrete working space of RT1 is described and the parameter optimization for kinematical redundancy resolution is studied also. The optimization criterion is altering the design parameter as little as possible during manipulator's motion from the initial position to the expected position. An optimization example is given that is realized with Matlab optimize tool-box. 相似文献
146.
147.
从中国化妆品工业发展史、发展现状以及发展前景等方面论述了中国化妆品工业的进程。同时阐述了中国化妆品工业与世界水平的差距以及中国化妆品工业所面临的机遇和挑战,并对中国化妆品的发展进行了预测。 相似文献
148.
ASP开发信息服务系统示例 总被引:1,自引:0,他引:1
随着网络技术的迅猛发展,ASP已成为Web应用程序的一种重要开发工具。用ASP(Active Server Pages)技术创建的此信息服务系统分为前端的客户信息浏览、查询和后台的数据库维护两大部分。对数据库设计,程序设计和实现,系统安全进行了详细论述。 相似文献
149.
介绍了演绎数据库的系统结构,并着重介绍了基于SQL Serverr之上的递归查询算法和将以规则形式存放于外存的虚关系转化为内部表示的过程。 相似文献
150.
谷峰 《西南师范大学学报(自然科学版)》2003,28(5):741-745
在一般的Banach空间中证明了非线性方程x tx=f的解的具误差的Ishikawa迭代过程的新的稳定性定理,推广和改进了近期的一系列相关结果. 相似文献