SARS沿交通线的“飞点”传播模型

20 0 3年春SARS在中国部分地区暴发与蔓延 ,情况非常危急。全国集中力量对SARS病原学、实验室诊断和临床治疗以及传播模型、应急反应系统等展开研究。综观此次SARS的传播 ,除有以往流行性疾病传播的一些共同特点外 ,还有一个很明显的特点 :远距离跳跃式传播。这是以往以及目前针对SARS建立的点源扩散模型无法单独解决的。因此提出建立沿交通线的“飞点”传播模型 ,以交通工具为一尺度 ,建立相对封闭的交通工具内的SARS传播模型 ,另以此为基础 ,建立沿交通线这一尺度上的有人员流动的空间传播模型 ,建立二尺度的“飞点”传播模型 ,模拟交通工具内SARS传播的主要影响因子 ,SARS疫区对非疫区疫情的影响效果 ,为SARS防治提供决策支持。

基于复合波形识别算法的“飞点”检测和还原方案研究

智能变电站以全站信息的数字化为基本要求,利用数字采样代替传统的模拟采样,采样装置数量大大增加。站域保护对数字采样的可靠性提出了更高要求,而SV(采样值)中存在大幅值“飞点”(数据异常点)是引起保护误动的主要原因。在深入研究“飞点”产生原因及其特征的基础上,提出一种基于复合波形识别算法的“飞点”检测和还原方案:采用基于积分型波形对称法和导数型波形识别法的复合波形识别算法,利用标准正弦波窗的概念,能迅速、准确地识别“飞点”数据。另外,根据正弦恢复算法可对“飞点”数据进行修复,无需闭锁判据即可保证保护的可靠性。通过建立PSCAD仿真模型,模拟单个“飞点”和连续“飞点”的正常运行和短路故障时波形,验证了所提“飞点”识别及修复方案的可靠性。仿真结果证明,保护装置动作正常,不会发生误动、拒动。

准分子激光矫正屈光不正的原理及其实现

研究了准分子激光治疗屈光不正的原理及其实现方法 ,介绍了准分子激光治疗屈光不正的原理及其种类。在初始角膜模型假设的基础上 ,提出了能够用于近视、远视和散光等屈光手术的数学模型 ,计算出切削量和切削的层数 ,并给出了相应的算法框图。就准分子激光角膜切削机理和“飞点扫描”等关键技术进行了研究 ,研究成果直接用于准分子激光眼科治疗机 ,并给出了准分子激光眼科治疗机的原理框图。实验和临床数据表明 。

Igniting the Statistical Spark in the Social Sciences—Abilities, Student Feedback and Teacher Observations

A quasi-experimental design was used to measure file impacts on student attainment in statistics, mathematics and critical thinking （16-18 years of age） on an experimental group who received a 21 week long contextualised statistics course （called the Pilot Scheme in SA （social analytics））, in South Wales. This paper will discuss the changes in statistical abilities observed, student feedback from the course and also teacher observations, in relation to the Pilot Scheme in SA. Results suggest that the course did lead to increase in students＇ abilities, in comparison to two control groups. Whereas students in both control groups who did not receive the treatment, showed a decrease in their abilities with respect to mathematics and statistics. Student feedback suggests they could see the value of the course to their other studies and they also felt the statistics delivered was linked well with relevant examples. Results from an analysis of teacher observations support findings from the course evaluation of the Pilot Scheme in SA, which include an increase in student confidence with mathematics and statistics.

Design and simulation for large parafoil fix line object homing algorithm

Traditional parafoil homing usually uses a point as object. As the mobility of parafoil is limited by its glide ratio and wind, in some cases when the parafoil scatter area is large, or the glide ratio of parafoil is small, the deviation of its landing point to object point will be arduous to control. Accordingly, during these situations, when parafoil is used in recovery of spacecraft or satellite, the landing area of parafoil can be set as a rectangle, and the object of parafoil can be set as a line segment. The thesis of this work is designing an algorithm for parafoil homing using line segment as object. The algorithm of wind velocity and direction calculation in different flying segments was also investigated. The algorithm designed navigates the parafoil to land into the predestined area and largely reduce the probability of recovery loads falling to unwanted area to damage houses and people.

Comparative study on aerodynamic heating under perfect and nonequilibrium hypersonic flows

In this study, comparative heat flux measurements for a sharp cone model were conducted by utilizing a high enthalpy shock tunnel JF-10 and a large-scale shock tunnel JF-12, responsible for providing nonequilibrium and perfect gas flows, respectively. Experiments were performed at the Key Laboratory of High Temperature Gas Dynamics(LHD), Institute of Mechanics, Chinese Academy of Sciences. Corresponding numerical simulations were also conducted in effort to better understand the phenomena accompanying in these experiments. By assessing the consistency and accuracy of all the data gathered during this study, a detailed comparison of sharp cone heat transfer under a totally different kind of freestream conditions was build and analyzed. One specific parameter, defined as the product of the Stanton number and the square root of the Reynold number, was found to be more characteristic for the aerodynamic heating phenomena encountered in hypersonic flight. Adequate use of said parameter practically eliminates the variability caused by the deferent flow conditions, regardless of whether the flow is in dissociation or the boundary condition is catalytic. Essentially, the parameter identified in this study reduces the amount of ground experimental data necessary and eases data extrapolation to flight.

Affine groups and flag-transitive triplanes

Let D be a nontrivial 2-(v, k, 3) symmetric design (triplane) and let G≤Aut(D) be flag-transitive and point-primitive. In this paper, we prove that if G is an affine group, then G≤AΓL1(q), where q is some power of a prime p and p≥5.

Floquet-based design and control approach to spacecraft formation flying in libration point orbits

A method for spacecraft formation flying (SFF) design and control near libration point orbits was developed by making use of the Floquet theory for periodic orbits. Firstly, the Floquet theory used in libration point orbits was introduced and the coefficients of four Floquet periodic modes were proved to be nearly constant when the amplitude in z direction of earth-moon L1 halo orbits is less than 20000 km. On this basis, a configuration design approach to SFF in L1 halo orbits was proposed, and several types of special configurations were obtained with periodic mode 3 and mode 5 or mode 4 and mode 6. Then, in order to control the SFF configuration concisely, those coefficients of the 5 modes (except the stable one) must be kept constant. A stationkeeping method for SFF was developed, which controls 5 Floquet modes simultaneously. Finally, simulations showed that the Floquet-based approach of configuration design and control for SFF is effective, simple and convenient. The research may be of value for deep space explorations.