国外生物学期刊出版概况和特点

以《外国报刊目录》第九版为资料,对生物学期刊的学科分布、国别分布、类别分布、出版频率及出版机构等进行了认真调查,并对其突出的特点进行了简要的描述。     

基于频度与价格指标法比较的服务贸易壁垒研究

以中国入世承诺表及服务业上市公司的财务数据为基础,分别运用频度和价格指标法对中国各服务部门的贸易壁垒进行研究,并与制造业比较。结果显示,中国服务贸易对外开放广度大,但深度低,与制造业相比,服务贸易壁垒水平仍很高;服务部门间的壁垒水平差异大,除运输服务业外,传统服务业的贸易壁垒低于现代服务业,其中金融业的贸易壁垒限制最多;除教育服务外,其他部门的市场准入限制大于国民待遇限制。因此,应明确政府在服务贸易中的管理职能,完善相关法律体系。同时,逐步降低市场准入壁垒,优化产业结构,提高现代服务业竞争水平。     

Combinatorial Equivalence of Fractional Factorial Designs

Two symmetrical fractional factorial designs are said to be combinatorially equivalent if one design can be obtained from another by reordering the runs, relabeling the factors and relabeling the levels of one or more factors. This article presents concepts of ordered distance frequency matrix, distance frequency vector, and reduced distance frequency vector for a design. Necessary conditions for two designs to be combinatorial equivalent based on these concepts are presented. A new algorithm based on the results obtained is proposed to check combinatorial non-equivalence of two factorial designs and several illustrating examples are provided.     

软件无线电中正交数字变频的DSP实现

介绍了软件无线电的概念及DSP基本原理,利用DSP实现软件无线电中的正交数字变频技术,给出了中频下变频的数字化实现的主程序.     

A Probabilistic Methodology for the Assessment of Safety from Dropped Loads in Offshore Engineering

Pipeline damage by dropped objects from crane activities is a significant hazard for offshore platform installations. In this paper a probabilistic methodology is utilized for the estimation of the pipeline impact and rupture frequencies; this information is obtained both for the overall pipeline section exposed to the hazard and for a number of critical locations along the pipeline route. The presented algorithm has been implemented in a computer program that allows the analysis of a large number of possible drop points and pipeline target point locations. This methodology may be used in common risk analysis studies for evaluating the risk for platform personnel from dropped objects; however, the proposed technique may also be useful for other applications where engineering judgment has so far been the main driving criterion. In particular, two sample cases have been analyzed. The first one is the problem of selecting the best approaching route to a platform. By analyzing different route alternatives, a reduction of the impact frequency and therefore of the risk for the platform personnel may be achieved. The second application deals with the selection of the location for a safety valve at the riser base. The analysis may give useful information, such as the highest impact frequency location and the rupture frequencies upstream and downstream of the valve as a function of the valve position; this information, together with the transported medium inventory upstream of the valve, may give the designer a documented and justifiable rationale for selecting the best location for the valve from a safety point of view.     

Estimation of Correlation for Continuous Semimartingales

Abstract. In this study we are concerned with inference on the correlation parameter ρ of two Brownian motions, when only high‐frequency observations from two one‐dimensional continuous Itô semimartingales, driven by these particular Brownian motions, are available. Estimators for ρ are constructed in two situations: either when both components are observed (at the same time), or when only one component is observed and the other one represents its volatility process and thus has to be estimated from the data as well. In the first case it is shown that our estimator has the same asymptotic behaviour as the standard one for i.i.d. normal observations, whereas a feasible estimator can still be defined in the second framework, but with a slower rate of convergence.     

步进电机的定位及速度控制软件设计

结合步进电机在数控系统中的应用，介绍８０３１ 单片机控制步进电机的方法及实现步进电机的精确定位、换向和速度控制的软件设计。     

宽带LFM信号去斜率数字脉压方法性能分析

在宽带LFM信号数字脉压中,去斜率数字脉压方法能有效地降低采样率,但是受到目标回波信号与参考信号的时延差的限制,只能作局部脉压处理。同时目标回波信号与参考信号的时延差和目标多普勒频率的变化,对去斜率数字脉压结果有一定的影响。该文通过理论分析和较全面的仿真,定量地分析了去斜率数字脉压中目标回波信号与参考信号时延差和多普勒频率的变化对数字脉压性能的影响,为工程应用中合理选择信号带宽、采样率和目标回波信号的时延提供了参考。     

相控阵雷达低仰角目标DOA估计的算法

在相控阵雷达跟踪低仰角目标时,采用频率捷变技术可以有效地减小雷达回波中直射信号和反射信号的相关性,抑制多径效应对目标到达方向估计造成的影响,提高角度估计的精度和性能。再用修正的AR模型算法,不仅可以在此基础上进一步去掉这两种信号的相关性,而且能正确估计出目标和镜像的仰角。计算机仿真实验结果验证了频率捷变和修正AR模型算法理论的正确性,以及在与其他方法比较的情况下,两者结合在去相关性能上的优越性和工程实用性。