浅议抽样方法中的二重分层抽样及多重抽样

浅议抽样方法中的二重分层抽样及多重抽样马勤抽样方法是现代统计学的重要组成部分，是统计调查与统计分析集于一身的一种强有力认识社会的方法，尤其对当前我国由计划经济逐步转向市场经济的大变革时代，抽样调查更有它特殊的作用。比如，一个企业要想了解自己的产品在市...

事后分层权重的估计方法与Stata软件实现

目的:从方法学角度为复杂抽样数据事后分层权重的估计提供方案。方法:以2010年全国普查人口为标准人口,按照年龄(56层)、性别(2层)、城乡(2层)三个辅助变量共计224层的分组,使用Stata13.1软件对2011年CHARLS基线调查样本的事后分层权重进行估计。结果:撰写完成事后分层权重估计的Stata程序脚本,并以此获得CHARLS基线样本的事后分层权重及最终权重。应用事后分层权重调整后的样本人口学构成与标准人口构成一致。结论:事后分层调整与标准化方法相比,优势是不仅可以获得参数的合计估计值,而且可获得依据辅助变量分层后各层的参数估计值。

分层标准差权重系数法在临床护理过程质量评价中的应用

目的为了研究护理过程质量评价中指标权重系数的确定,及其指标合成运算的科学可行方法。方法通过对四个科室的120位住院患者的问卷调查,将所得结果,运用本文提出的标准差权重系数法进行运算。结果不仅确定了各个层次指标的权重系数,而且得到各个科室的评分值,对各科室的优劣进行了比较。结论通过实际运算结果的分析,以及与层次分析法、模糊数学法的比较分析,表明该方法具有一定的科学性、新颖性和可行性,值得研究和推广应用。

基于多样性向导的自适应重采样粒子滤波研究

由于在非线性非高斯系统和多模处理能力上的优越性,粒子滤波算法已经被广泛应用。针对粒子滤波算法现有缺陷分析,提出一种基于多样性向导的自适应重采样粒子滤波。首先,基于多样性向导自适应调整重采样阈值。在基于有效样本大小的自适应重采样技术之上,借助了另一多样性测度即种群多样性因子来自适应地调整有效样本大小的阈值;而且,在重采样之后引入样本变异操作来确保样本的多样性。然后,提出了一种改进的部分分层重采样算法。该算法借鉴部分分层重采样执行快、时间短的优点,同时结合权重优化的思想改进重采样的样本权重计算。最后,通过仿真实验验证了所提粒子滤波算法的性能和有效性。

基于分层模态综合法的大型汽轮发电机组转子-末级叶片耦合系统扭转振动分析

针对应用三维有限元法计算大型汽轮发电机组转子-末级叶片耦合系统扭转振动时存在自由度多和难以实现等问题,在模态综合法(CMS)的基础上,推导了计算转子-末级叶片耦合系统振动的分层二重CMS法的基本方程,给出了降阶的思路和原理.采用该方法对某1 000 MW汽轮发电机组的转子、末级和次末级叶片组成的耦合系统进行了扭转振动特性计算和分析,与不考虑末级、次末级叶片实际结构影响的固有振动特性进行了对比.结果表明:如果不考虑末级叶片的实际结构,会漏掉一些重要的振动模态,给转子和叶片的安全带来隐患;降阶前系统的自由度达到1.5亿,而降阶后系统的广义自由度仅为原自由度的0.07%;分层二重CMS法可用于大功率机组转子、末级、次末级耦合系统的扭转振动分析.

双重抽样

本世纪六十年代以来,各国在抽样调查领域内有了新的发展,尤其在应用于经济和社会调查方面取得了许多重要的进展,诸如关于抽样比例和百分比估计,决策问题中的样本含量,由于分层而得益的估计,分层抽样中的比率和回归估计,系统抽样(或称等距抽样),双重抽样(或称二相抽样),以及调查中关于误差来源的研究等等,都是较为新颖的技术,引起各国特别是发展中国家有关人员的广泛兴趣。本文试就其中的双重抽样作简略介绍。

Experimental investigation of vibration pretreatment-microwave curing process for carbon fiber reinforced resin matrix composites

The vibration pretreatment-microwave curing process is an efficient,low energy consumption,and high-quality out-of-autoclave curing process for carbon fiber resin matrix composites.This study aims to investigate the impact of vibration pretreatment temperature on the fiber weight content,microscopic morphology and mechanical properties of the composite laminates by using optical digital microscopy,universal tensile testing machine and thermo-gravimetric analyzer.Additionally,the combined mode of Bragg fiber grating sensor and temperature measurement fiber was employed to explore the effect of vibration pretreatment on the strain process during microwave curing.The study results revealed that the change in vibration pretreatment temperature had a slight impact on the fiber weight content when the vibration acceleration remained constant.The metallographic and interlaminar strength of the specimen formed at a vibration pretreatment temperature of 80℃ demonstrated a porosity of 0.414% and a 10.69% decrease in interlaminar shear strength compared to autoclave curing.Moreover,the introduction of the vibration energy field during the microwave curing process led to a significant reduction in residual strain in both the 0°and 90°fiber directions,when the laminate was cooled to 60℃.

Non-isothermal oxidation and ignition prediction of Ti-Cr alloys

The non-isothermal oxidation behavior and oxide scale microstructure of Ti-Cr alloy （0≤w（Cr）≤25%） were studied from room temperature to 1723 K by thermogravimetric analysis （TGA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The influencing mechanism of chromium on the oxidation resistance of Ti-Cr alloys was discussed. The results show that the oxidation resistance of the alloys decreases with Cr below a critical chromium content wC and increases above wC; above 1000 K, the oxidation kinetics obeys parabolic rule and titanium dominates the oxidation process; after oxidation, the oxygen-diffusing layer is present in the alloy matrix, the oxide scale is mainly composed of rutile whose internal layer is rich in chromium, and chromium oxides separated out from TiO2 near the alloy-oxide interface improve the oxidation resistance. Ignition of metals and alloys is a fast non-isothermal oxidation process and the oxidation mechanism of Ti-Cr alloys during ignition is predicted.

一种改进的自适应优化粒子滤波算法研究

粒子滤波算法在非线性滤波领域受到广泛关注,但是该算法存在样本退化问题.为了改进粒子滤波算法的性能,这里结合自适应优化机制对粒子滤波算法的建议分布选择机制及重采样技术进行改进.对于粒子滤波的建议分布选择,提出一种基于自适应退火参数优化的混合建议分布方法.通过混合建议分布不足的分析,利用退火参数来优化控制状态转移先验分布函数和观测似然函数之间的比例,同时,基于自适应参数优化机制来动态调整退火参数的值.对于粒子滤波的重采样,提出了基于部分分层重采样优化算法的自适应重采样技术.通过有效样本大小的评估来执行自适应重采样策略,此外,基于部分分层重采样算法,利用权重优化的思想对其重采样前后权重计算的方法进行优化.通过相关算法的性能比较,所提改进粒子滤波算法的有效性得以验证.

大型民航通信系统鲁棒性测试模型仿真分析

民航通信系统属于复杂网络通信系统,系统的通信节点数目庞大,传统的复杂网络鲁棒性分析算法性测试结果存在失真。为此提出一种分层权重划分理论的鲁棒性分析模型,并应用到航空通信系统的鲁棒性检测中,塑造BP神经网络大型民航通信系统鲁棒性评价模型,对影响大型民航通信系统鲁棒性的各项指标进行打分,依据综合得分进行不同的加权,获取大型民航通信系统鲁棒性评价指标的分层权重样本测试数据,按照获取的大型民航通信系统信息以及信息的改变量,对自适应加权BP神经网络权向量进行修正,建立大型民航通信系统中不同节点间的关联约束关系,将某种约束条件引入传统的关联规则中,提高大型民航通信系统鲁棒性测试的效率,获取准确的测试结果。实验结果表明,采用所提模型能更精确的分析出航空通信设备的鲁棒性。

Effects of Biogas Slurry Irrigation on Heavy Metal Contents in Soils

[Objective] This study aimed to investigate the effects of biogas slurry irri- gation on heavy metal contents in soils. [Method] A pot experiment was carried out to investigate the effects of biogas slurry irrigation on the accumulation of heavy metals in soils by measuring the contents of Cu, Zn, Pb, Cr and Cd in different soil layers. [Result] The results showed that original and 30-fold biogas slurry increased the contents of Cu, Zn, Pb, Cd and Cr in soils; Cr might partially reach an exces- sive level in a short term. Biogas slurry irrigation increased the downward migration velocity of Cu and reduced the downward migration velocity of Zn in soils. [Conclu- sion] Biogas slurry irrigation influences the contents of heavy metals, and long-term application of biogas slurry will lead to the accumulation of heavy metals in soils.

基于决策树的电网企业信息化项目风险管控

创新性地提出基于决策树的信息化项目风险管控方法。对电网企业的信息化项目从业务、技术、开发能力、标准规范、协调沟通等方面进行风险管控需求的详细分析;对典型的项目管控基础进行介绍,明确典型的信息化项目的实施过程及风险点;创新性地引入了分层权重法对信息化项目风险进行分类加权,并将决策树理论引入信息化项目风险管控中,从而有效辨识、估计以及评价风险点,增强管理人员对信息化项目风险的管控能力,减少可能发生的对项目的不良影响。

Thermogravimetric study of the effect of a PVA oxygen-insulating barrier on the spontaneous combustion of coal

Coal samples in the air for three months were characterized by Thermogravimetric Analysis (TGA). The effect of a PVA oxygen-insulating barrier on the spontaneous combustion of coal was examined. The moisture loss activation energy, oxidation activation energy and combustion activation energy were calculated by an integral method using the Coats-Redfen formula. The results show that the tendency for spontaneous combustion of three coal samples (judged by the activation energy) falls in the order: CYW>YJL>SW. The oxidation activation energy and combustion activation energy of coal protected by the PVA oxygen-insulating barrier increased. A significant increase in the combustion activation energy was noted, especially for the CYW coal where the in-crease was 28.53 kJ/mol. Hence, oxidation of the protected coal samples was more difficult. The PVA oxygen-insulating barrier helps to prevent spontaneous combustion of the coal.

一种改进的无人机FastSLAM1.0算法

无人机Fast SLAM1.0算法粒子滤波的预测过程没有考虑地标的观测值,并不能利用新的测量数据更新无人机的位姿,使得粒子集偏离无人机真实位姿,需要大量粒子改进粒子滤波的精度,增加了算法的计算复杂性。为此,提出采用模拟退火算法更新粒子的预测值,调整提议分布,使得粒子集中在无人机真实位姿的周围,并利用分层重采样解决粒子退化问题。在无人机环境下对该算法进行仿真研究,结果表明其估计精度明显优于Fast SLAM2.0算法,验证了算法的有效性和可行性。

Analysis of bulked segregants to identify molecular markers linked with cocoon weight and cocoon shell weight in the silkworm Bombyx mori L

Two silkworm strains viz, B20 A (high cocoon shell ratio) and C.Nichi (low cocoon shell ratio) were sib mated for 10 generations to determine the homozygosis. Both bulked segregant analysis(BSA) and near isogenic lines (NIL) studies were done to identify the RFLP markers closely linked to cocoon shell parameters. Three hundred and fifty two random clones were identified as the low copy number sequence and used for identification of Restriction Fragment Length Polymorphic (RFLP) marker linked to cocoon weight and cocoon shell character. In the bulk segregant analysis, DNA from the parents (B20 A, C.Nichi), F 1 and F 2 progeny of high shell ratio (HSR) and low shell ratio (LSR) were screened for hybridization with the random clones. Polymorphic banding pattern achieved through southern hybridization with different probes indicated the probable correlation of polymorphism with high and low cocoon shell character which are possible landmarks in identifying the putative marker(s) for the cocoon shell character. Out of the 100 probes tried with parents, F 1, F 2 and their bulks, 10 probes were found to be closely linked to cocoon shell characters.

A compound objective reconfiguration of distribution networks using hierarchical encoded particle swarm optimization

With the development of automation in smart grids,network reconfiguration is becoming a feasible approach for improving the operation of distribution systems.A novel reconfiguration strategy was presented to get the optimal configuration of improving economy of the system,and then identifying the important nodes.In this strategy,the objectives increase the node importance degree and decrease the active power loss subjected to operational constraints.A compound objective function with weight coefficients is formulated to balance the conflict of the objectives.Then a novel quantum particle swarm optimization based on loop switches hierarchical encoded was employed to address the compound objective reconfiguration problem.Its main contribution is the presentation of the hierarchical encoded scheme which is used to generate the population swarm particles of representing only radial connected solutions.Because the candidate solutions are feasible,the search efficiency would improve dramatically during the optimization process without tedious topology verification.To validate the proposed strategy,simulations are carried out on the test systems.The results are compared with other techniques in order to evaluate the performance of the proposed method.

A method of reconstructing complex stratigraphic surfaces with multitype fault constraints

The construction of complex stratigraphic surfaces is widely employed in many fields, such as petroleum exploration, geological modeling, and geological structure analysis. It also serves as an important foundation for data visualization and visual analysis in these fields. The existing surface construction methods have several deficiencies and face various difficulties, such as the presence of multitype faults and roughness of resulting surfaces. In this paper, a surface modeling method that uses geometric partial differential equations （PDEs） is introduced for the construction of stratigraphic surfaces. It effectively solves the problem of surface roughness caused by the irregularity of stratigraphic data distribution. To cope with the presence of multitype complex faults, a two-way projection algorithm between three- dimensional space and a two-dimensional plane is proposed. Using this algorithm, a unified method based on geometric PDEs is developed for dealing with multitype faults. Moreover, the corresponding geometric PDE is derived, and an algorithm based on an evolutionary solution is developed. The algorithm proposed for constructing spatial surfaces with real data verifies its computational efficiency and its ability to handle irregular data distribution. In particular, it can reconstruct faulty surfaces, especially those with overthrust faults.

A novel technique of three-dimensional reconstruction segmentation and analysis for sliced images of biological tissues

A novel technique of three-dimensional (3D) reconstruction, segmentation, display and analysis of series slices of images including microscopic wide field optical sectioning by deconvolution method, cryo-electron microscope slices by Fou-rier-Bessel synthesis and electron tomography (ET), and a series of computed tomography (CT) was developed to perform si-multaneous measurement on the structure and function of biomedical samples. The paper presents the 3D reconstruction seg-mentation display and analysis results of pollen spore, chaperonin, virus, head, cervical bone, tibia and carpus. At the same time, it also puts forward some potential applications of the new technique in the biomedical realm.

Natural history of heartburn:A 10-year population-based study

AIM： To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. METHODS： A population-based postal study was carried out. Questionnaires were mailed to the same age- and gender-stratified random sample of the Icelandic population （aged 18-75 years） in 1996 and again in 2006. Subjects were classified with heartburn if they reported heartburn in the preceding year and/or week, based on the definition of heartburn. RESULTS： Heartburn in the preceding year was reported in 42.8% （1996） and 44.2% （2006） of subjects, with a strong relationship between those who experienced heartburn in both years. Heartburn in the precedingweek was diagnosed in 20.8%. There was a significant relationship between heartburn, dyspepsia and irritable bowel syndrome. IndMduals with a body mass index （BMI） below or higher than normal weight were more likely to have heartburn. Heartburn caused by food or beverages was reported very often by 20.0% of subjects. CONCLUSION： Heartburn is a common and chronic condition. Subjects with a BMI below or higher than normal weight are more likely to experience heartburn. Heartburn has a great impact on daily activities, sleep and quality of life.