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病态数据处理的岭估计迭代解法 预览
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作者 吴光明 鲁铁定 《大地测量与地球动力学》 CSCD 北大核心 2019年第2期178-183,共6页
岭估计通常无法单次计算使得均方误差达到最小,因此提出岭估计迭代法。将岭估计参数估值代入平差模型,更新观测向量,再次用岭估计法求解参数。依此迭代,每次迭代计算方差和偏差,当均方误差达到最小或收敛时终止。模拟算例验证结果表明,... 岭估计通常无法单次计算使得均方误差达到最小,因此提出岭估计迭代法。将岭估计参数估值代入平差模型,更新观测向量,再次用岭估计法求解参数。依此迭代,每次迭代计算方差和偏差,当均方误差达到最小或收敛时终止。模拟算例验证结果表明,该方法有效、可行。 展开更多
关键词 岭估计 方差 偏差 迭代 均方误差
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Detecting Intensity Evolution of the Western North Pacific Super Typhoons in 2016 Using the Deviation Angle Variance Technique with FY Data
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作者 Meng YUAN Wei ZHONG 《气象学报:英文版》 SCIE CSCD 2019年第1期104-114,共11页
This paper analyzes the complete lifecycle of super typhoons in 2016 in the western North Pacific(WNP) using the deviation angle variance technique(DAV-T). Based on the infrared images from Fengyun(FY) satellites, the... This paper analyzes the complete lifecycle of super typhoons in 2016 in the western North Pacific(WNP) using the deviation angle variance technique(DAV-T). Based on the infrared images from Fengyun(FY) satellites, the DAV-T enables quantification of the axisymmetry of tropical cyclones(TCs) by using the DAV values;and thus, it helps improve the capability of TC intensity estimation. Case analyses of Super Typhoons Lionrock and Meranti were performed to explore the distribution characteristics of the DAV values at the various stages of TC evolution. The results show that the minimum DAV values(i.e., map minimum values: MMVs) gradually decreased and their locations constantly approached the circulation center with enhancement of the TC organization;however, when a ring or disk structure was formed around a TC, significant changes in MMV locations were no longer observed. Nonetheless,when large-scale non-closed deep convective cloud clusters appeared at the early stage or the dissipation stage of the typhoon, the axisymmetry of the TC was poor and the MMV locations tended to lie in the most convective region rather than in the TC circulation center. Overall, the MMVs and their locations, respectively, exhibited a strong correlation with the TC intensity and circulation center, and the correlation increased as the TCs became stronger. Combined with the China Meteorological Administration BestTrack dataset(CMA-BestTrack), statistical analysis of all research samples reveals that the correlation coefficient between the MMVs and maximum surface wind speeds(Vmax) was –0.80;the root mean square error(RMSE) of relative distance between the MMV locations and TC centers was 140.3 km;and especially, when the samples below the tropical depression(TD) intensity were removed, the RMSE of the relative distance decreased dramatically to 95.0 km. The value and location of the MMVs could be used as important indicators for estimating TC intensity and center. 展开更多
关键词 deviation angle variance technique(DAV-T) AXISYMMETRY super TYPHOON Fengyun(FY) SATELLITES
犹豫模糊软集的相关系数及其在决策中的应用
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作者 黄先玖 汤静 《控制与决策》 EI CSCD 北大核心 2019年第4期821-826,共6页
犹豫模糊软集结合了Torra(2010)的犹豫模糊集理论和Molodtsov(1999)的软集理论.鉴于相关系数是数据分析中应用最广泛的指标之一,提出一种犹豫模糊软集相关系数,同时给出犹豫模糊软集的平均值和方差的定义,基于这些概念给出犹豫模糊软集... 犹豫模糊软集结合了Torra(2010)的犹豫模糊集理论和Molodtsov(1999)的软集理论.鉴于相关系数是数据分析中应用最广泛的指标之一,提出一种犹豫模糊软集相关系数,同时给出犹豫模糊软集的平均值和方差的定义,基于这些概念给出犹豫模糊软集相关系数的计算公式.新的犹豫模糊软集相关系数的值在区间[-1, 1]上,而不是[0, 1]上,这与统计学中经典相关系数一致,因此克服了已有犹豫模糊软集相关系数中存在的缺陷.为了提升其应用的广泛性,提出犹豫模糊软集加权相关系数的概念.最后,通过医院评估的实例验证所提出的犹豫模糊软集相关系数的适用性和有效性. 展开更多
关键词 犹豫模糊软集 平均值 方差 相关系数 加权相关系数 决策
Cloud detection from visual band of satellite image based on variance of fractal dimension 预览
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作者 TIAN Pingfang GUANG Qiang LIU Xing 《系统工程与电子技术:英文版》 SCIE EI CSCD 2019年第3期485-491,共7页
Cover ratio of cloud is a very important factor which affects the quality of a satellite image, therefore cloud detection from satellite images is a necessary step in assessing the image quality. The study on cloud de... Cover ratio of cloud is a very important factor which affects the quality of a satellite image, therefore cloud detection from satellite images is a necessary step in assessing the image quality. The study on cloud detection from the visual band of a satellite image is developed. Firstly, we consider the differences between the cloud and ground including high grey level, good continuity of grey level, area of cloud region, and the variance of local fractal dimension (VLFD) of the cloud region. A single cloud region detection method is proposed. Secondly, by introducing a reference satellite image and by comparing the variance in the dimensions corresponding to the reference and the tested images, a method that detects multiple cloud regions and determines whether or not the cloud exists in an image is described. By using several Ikonos images, the performance of the proposed method is demonstrated. 展开更多
关键词 CLOUD detection VISUAL IMAGE SATELLITE IMAGE variance of local FRACTAL dimension (VLFD)
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小直径刀具高速铣削316L不锈钢试验的切削合力、振动方差分析 预览
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作者 阙燚彬 《柳州职业技术学院学报》 2019年第1期83-86,共4页
根据选定的因素水平和正交试验,进行关于切削合力和振动影响的316L不锈钢小直径刀具高速铣削加工正交试验,并对试验结果进行方差分析,得到减少切削合力、振动的切削要素调整方案。
关键词 正交试验 切削合力、振动、方差 钎削试验
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Global, regional, and cladistic patterns of variation in climatic niche breadths in terrestrial elapid snakes
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作者 Long-Hui Lin Xia-Ming Zhu +2 位作者 Yu Du Meng-Chao Fang Xiang Ji 《动物学报:英文版》 SCIE CAS CSCD 2019年第1期1-9,共9页
We obtai ned geo-refere need occurre nee and climatic data from in dividual localities for 59 species of terrestrial elapid snakes, used phylogenetic generalized least squares regression to investigate spatial and cla... We obtai ned geo-refere need occurre nee and climatic data from in dividual localities for 59 species of terrestrial elapid snakes, used phylogenetic generalized least squares regression to investigate spatial and cladistic patter ns of variation in climatic niche breadths, and compared patter ns within and across regions and clades to see if they parallel or differ from each other. Specifically, we test (1) whether a species' climatic niche breadth on a given niche axis relates to its position along that axis, and to its climatic niche breadth on another niche axis, and (2) whether variation in niche breadths among species is explained by within-locality variation in climatic conditions or by among-locality variation. We found that:(1) there is an overall global patter n, and patter ns in individual regi ons or clades gen erally parallel each other and global patter ns;(2) species in wanner environments have narrower temperature niche breadths (TNBs);(3) precipitation niche breadth (PNB) and position are positively related;⑷ TNB and PNB are not related;and ⑸ within-locality variation in climatic conditions explains most variation in TNBs, whereas among-locality variation explains most variation in PNBs. Our results are consistent with those reported for lizards of the families Phrynosomatidae and Varanidae, con firm the importance of withi n-locality n iche breadth to species n iche breadth, and show a more im porta nt role of amon g-locality n iche breadth in affecting species niche breadth in terrestrial elapids than in lizards. 展开更多
关键词 climate ELAPIDAE NICHE BREADTH NICHE position NICHE variance precipitation temperature
液压阀块加工误差概率分析与应用浅析 预览
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作者 赵已龙 张永锋 +1 位作者 丘铭军 刘杰 《液压气动与密封》 2019年第5期58-61,共4页
针对大型高集成度液压阀块,液压元件排列紧凑尺寸多,加工成本高,风险大等客观问题,利用概率统计学分析的方法计算出各尺寸误差及尺寸链累积误差对加工精度的影响,从而确定液压阀块最佳的基准面和最佳尺寸链,以达到最高加工精度,降低液... 针对大型高集成度液压阀块,液压元件排列紧凑尺寸多,加工成本高,风险大等客观问题,利用概率统计学分析的方法计算出各尺寸误差及尺寸链累积误差对加工精度的影响,从而确定液压阀块最佳的基准面和最佳尺寸链,以达到最高加工精度,降低液压阀块的次品率要求。 展开更多
关键词 集成块 均值 方差 标准偏差
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A convergence analysis for a class of practical variance-reduction stochastic gradient MCMC
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作者 Cliangyou CHEN Wenlin WANG +2 位作者 Yizhe ZHANG Qinliang SU Lawrence CARIN 《中国科学:信息科学(英文版)》 SCIE EI CSCD 2019年第1期64-76,共13页
Stochastic gradient Markov chain Monte Carlo(SG-MCMC)has been developed as a flexible family of scalable Bayesian sampling algorithms.However,there has been little theoretical analysis of the impact of minibatch size ... Stochastic gradient Markov chain Monte Carlo(SG-MCMC)has been developed as a flexible family of scalable Bayesian sampling algorithms.However,there has been little theoretical analysis of the impact of minibatch size to the algorithm’s convergence rate.In this paper,we prove that at the beginning of an SG-MCMC algorithm,i.e.,under limited computational budget/time,a larger minibatch size leads to a faster decrease of the mean squared error bound.The reason for this is due to the prominent noise in small minibatches when calculating stochastic gradients,motivating the necessity of variance reduction in SG-MCMC for practical use.By borrowing ideas from stochastic optimization,we propose a simple and practical variance-reduction technique for SG-MCMC,that is efficient in both computation and storage.More importantly,we develop the theory to prove that our algorithm induces a faster convergence rate than standard SG-MCMC.A number of large-scale experiments,ranging from Bayesian learning of logistic regression to deep neural networks,validate the theory and demonstrate the superiority of the proposed variance-reduction SG-MCMC framework. 展开更多
关键词 MARKOV chain Monte Carlo SG-MCMC variance REDUCTION deep NEURAL networks
Uncertainties in the Effects of Climate Change on Maize Yield Simulation in Jilin Province:A Case Study
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作者 Yanxia ZHAO Chunyi WANG Yi ZHANG 《气象学报:英文版》 SCIE CSCD 2019年第4期777-783,共7页
Measuring the impacts of uncertainties identified from different global climate models(GCMs),representative concentration pathways(RCPs),and parameters of statistical crop models on the projected effects of climate ch... Measuring the impacts of uncertainties identified from different global climate models(GCMs),representative concentration pathways(RCPs),and parameters of statistical crop models on the projected effects of climate change on crop yields can help to improve the availability of simulation results.The quantification and separation of different sources of uncertainty also help to improve understanding of impacts of uncertainties and provide a theoretical basis for their reduction.In this study,uncertainties of maize yield predictions are evaluated by using 30 sets of parameters from statistical crop models together with eight GCMs with reference to three emission scenarios for Jilin Province of northeastern China.Regression models using replicates based on bootstrap resampling reveal that yields are maximized when the optimum average growing season temperature is 20.1°C for 1990–2009.The results of multi-model ensemble simulations show a maize yield reduction of 11%,with 75%probability for 2040–69 relative to the baseline period of 1976–2005.We decompose the variance so as to understand the relative importance of different sources of uncertainty,such as GCMs,RCPs,and statistical model parameters.The greatest proportion of uncertainty(>50%)is derived from GCMs,followed by RCPs with a proportion of 28%and statistical crop model parameters with a proportion of 20%of total ensemble uncertainty. 展开更多
关键词 analysis of variance (ANOVA) climate change ensemble simulation maize yield UNCERTAINTY
A general framework for frequentist model averaging In Celebration of Professor Lincheng Zhao’s 75th Birthday
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作者 Priyam Mitra Heng Lian +2 位作者 Ritwik Mitra Hua Liang Min-ge Xie 《中国科学:数学英文版》 SCIE CSCD 2019年第2期205-226,共22页
Model selection strategies have been routinely employed to determine a model for data analysis in statistics, and further study and inference then often proceed as though the selected model were the true model that we... Model selection strategies have been routinely employed to determine a model for data analysis in statistics, and further study and inference then often proceed as though the selected model were the true model that were known a priori. Model averaging approaches, on the other hand, try to combine estimators for a set of candidate models. Specifically, instead of deciding which model is the ’right’ one, a model averaging approach suggests to fit a set of candidate models and average over the estimators using data adaptive weights.In this paper we establish a general frequentist model averaging framework that does not set any restrictions on the set of candidate models. It broaden, the scope of the existing methodologies under the frequentist model averaging development. Assuming the data is from an unknown model, we derive the model averaging estimator and study its limiting distributions and related predictions while taking possible modeling biases into account.We propose a set of optimal weights to combine the individual estimators so that the expected mean squared error of the average estimator is minimized. Simulation studies are conducted to compare the performance of the estimator with that of the existing methods. The results show the benefits of the proposed approach over traditional model selection approaches as well as existing model averaging methods. 展开更多
关键词 ASYMPTOTIC distribution BIAS variance trade-off local mis-specification model AVERAGING ESTIMATORS optimal weight selection
基于差异的高校网络校际协作学习策略研究 预览
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作者 范雪菲 《湖北开放职业学院学报》 2019年第7期22-24,共3页
网络校际协作学习蕴含着共同性、差异性、建构性等三个基本特征。本文从“网络校际协作学习环境”“学生自主学习能力的培养”和“教师的角色定位”三个方面对基于差异的高校网络校际协作学习策略研究进行初步探讨,希望对高校网络校际... 网络校际协作学习蕴含着共同性、差异性、建构性等三个基本特征。本文从“网络校际协作学习环境”“学生自主学习能力的培养”和“教师的角色定位”三个方面对基于差异的高校网络校际协作学习策略研究进行初步探讨,希望对高校网络校际协作学习的发展有所启迪。 展开更多
关键词 网络校际协作学习 构建策略 差异性
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基于差分进化的两阶段文本特征选择算法 预览
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作者 肖晓丽 吴瑶 +1 位作者 周锡玲 廖卓凡 《计算机工程》 CAS CSCD 北大核心 2019年第2期303-309,314共8页
为降低文本特征空间维度,提高数据挖掘处理数据的效率,提出两阶段文本特征选择算法。结合方差和平均中位数2种方法构建高相关性的特征子集进行初步降维,并将其作为差分进化算法的初始特征种群。利用特征词的累计词频和文档频率设计适应... 为降低文本特征空间维度,提高数据挖掘处理数据的效率,提出两阶段文本特征选择算法。结合方差和平均中位数2种方法构建高相关性的特征子集进行初步降维,并将其作为差分进化算法的初始特征种群。利用特征词的累计词频和文档频率设计适应度函数,将多个特征差向量和局部最优特征引入变异操作中,增加特征子集的扰动性,加快差分进化算法的收敛速度,获得最优特征子集。在WebKB和Reuters-21578数据集上进行实验,结果表明,该算法在准确率、召回率和F1值上均优于TDM5、MADAC等算法,能够降低文本特征空间的维度,提高文本聚类效果。 展开更多
关键词 混合特征选择 降维 差分进化算法 方差 平均中位数 文本聚类
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中印佛教文学比较研究的若干问题——侯传文教授访谈录 预览
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作者 张叉 侯传文 《燕山大学学报:哲学社会科学版》 2019年第4期32-38,共7页
文章是四川师范大学外国语学院张叉教授对青岛大学文学院侯传文教授就中印佛教文学比较研究的若干问题所作的专题访谈。访谈主要围绕三方面问题展开:一是总结了印度佛教文学对中国文学产生的影响,归纳了佛教文学融入中国文学后保留的异... 文章是四川师范大学外国语学院张叉教授对青岛大学文学院侯传文教授就中印佛教文学比较研究的若干问题所作的专题访谈。访谈主要围绕三方面问题展开:一是总结了印度佛教文学对中国文学产生的影响,归纳了佛教文学融入中国文学后保留的异质特性和本土化特征,列举了佛教文学在中国文学中的主要变异;二是分析了印度偈颂对中国诗歌的主要影响,论述了中国僧传比印度佛传僧传更有历史内涵与史学意义的主要缘由,阐述了“佛教诗学”概念,特别是它的主要理论特点;三是从影响与接受、主题学、文类学、诗学、文学的跨学科研究及外延等六方面展开,指出了有待于进一步深化的中印佛教文学比较研究领域。 展开更多
关键词 中印佛教文学 比较文学 变异学
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树型结构分子图的两类Zagreb指标 预览
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作者 翟登鑫 阿依古丽·马木提 《曲阜师范大学学报:自然科学版》 CAS 2019年第1期7-12,共6页
图G的第三Zagreb指标和第三版Zagreb指标分别是M3(G)=∑uv∈E(G)|d(u)-d(v)|, M′1(G)=∑u∈V(G)dG(u)δG(u).该文研究了树型结构分子图的两类Zagreb指标.更准确地说,得到了一个随机选择的树型结构的n阶分子图的两类Zagreb指标的平均值... 图G的第三Zagreb指标和第三版Zagreb指标分别是M3(G)=∑uv∈E(G)|d(u)-d(v)|, M′1(G)=∑u∈V(G)dG(u)δG(u).该文研究了树型结构分子图的两类Zagreb指标.更准确地说,得到了一个随机选择的树型结构的n阶分子图的两类Zagreb指标的平均值和方差的界. 展开更多
关键词 ZAGREB指标 平均值 方差
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GNSS长度测量不确定性试验分析
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作者 刘以旭 曲国庆 +3 位作者 薛树强 苏晓庆 王胜利 齐珂 《测绘科学》 CSCD 北大核心 2019年第5期157-163,共7页
针对GNSS定位结果总是存在点位误差,由此导出的长度测量值为点位误差的非线性映射,对于长距离定位量测,其非线性影响较小,线性化近似一般可以满足精度要求,但对于短距离量测,其非线性影响不容忽略的问题.该文探讨了GNSS长度测量不确定... 针对GNSS定位结果总是存在点位误差,由此导出的长度测量值为点位误差的非线性映射,对于长距离定位量测,其非线性影响较小,线性化近似一般可以满足精度要求,但对于短距离量测,其非线性影响不容忽略的问题.该文探讨了GNSS长度测量不确定性来源,通过单点定位和差分定位试验验证了长度测量不确定性与定位精度、点间距离的关系,测试不同偏差和方差估计公式的适用性.试验表明,对于GNSS高精度、长基线测量,其长度统计偏差可以忽略,且方差为基线向量的方向方差;现有不确定性评估公式在超短基线情形适用性会变差,在这种情形下,试验表明二阶偏差和方差估计更为精确.通过消除长度统计偏差得到无偏估计量,可以有效提高距离量测的可靠性,为提高用户距离量测精度提供有益帮助. 展开更多
关键词 GNSS基线 长度测量 偏差 方差
基于电子管理系统的2型糖尿病临床路径变异分析 预览
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作者 路庆 张亚平 李亚新 《基层医学论坛》 2019年第23期3257-3259,共3页
目的分析基于电子管理系统2型糖尿病临床路径开展过程中产生的变异环节及变异原因,提出可行性整改措施,初步建立医院临床路径的变异管理模式,促进临床路径管理的顺利实施。方法收集医院电子管理系统2015年1月—2016年12月实施临床路径... 目的分析基于电子管理系统2型糖尿病临床路径开展过程中产生的变异环节及变异原因,提出可行性整改措施,初步建立医院临床路径的变异管理模式,促进临床路径管理的顺利实施。方法收集医院电子管理系统2015年1月—2016年12月实施临床路径管理的2型糖尿病纸质病历与电子病历资料进行回顾性分析,统计不同变异类型的发生率,并实施针对性整改措施。结果2型糖尿病临床路径总变异率高达48.79%,其中可控变异561例,占39.07%;不可控变异875例,占60.93%。结论通过提高患者依从性,明确医务人员责任,完善绩效考核办法及优化电子管理系统,可有效降低2型糖尿病临床路径变异的发生率。 展开更多
关键词 电子管理系统 2型糖尿病 临床路径 变异 分析
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Mask-based denoising scheme for ghost imaging
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作者 周阳 郭树旭 +1 位作者 钟菲 张天 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第8期148-155,共8页
Ghost imaging(GI)is thought of as a promising imaging method in many areas.However,the main drawback of GI is the huge measurement data and low signal-to-noise ratio.In this paper,we propose a novel mask-based denoisi... Ghost imaging(GI)is thought of as a promising imaging method in many areas.However,the main drawback of GI is the huge measurement data and low signal-to-noise ratio.In this paper,we propose a novel mask-based denoising scheme to improve the reconstruction quality of GI.We first design a mask through the maximum between-class variance(OTSU)method and construct the measurement matrix with speckle patterns.Then,the correlated noise in GI can be effectively suppressed by employing the mask.From the simulation and experimental results,we can conclude that our method has the ability to improve the imaging quality compared with traditional GI method. 展开更多
关键词 GHOST imaging MAXIMUM between-class variance MASK image quality
Study on the Perturbation Characteristics of Two-Channel Laser Propagation in Atmospheric Turbulence
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作者 杨晓东 高明 《理论物理通讯:英文版》 SCIE CAS CSCD 2019年第6期731-735,共5页
In order to study the influence factors of acquisition detection target information by lidar and understand the influence degree of each factor, the two-channel phase perturbation model and the two-channel eikonal var... In order to study the influence factors of acquisition detection target information by lidar and understand the influence degree of each factor, the two-channel phase perturbation model and the two-channel eikonal variance model are derived in detail by using the geometrical optics method in this paper, and each factor is discussed in detail. The results show that the transmission distance is the main factor to affect the two-channel perturbation. With the increase of the transmission distance, the disturbing degree will gradually weaken. With the increase of transverse coordinates,the disturbing of two channels will also be weakened. In order to further weaken the disturbing degree, the feature dimension should be far larger than the wavelength, but far less than the transmission distance. 展开更多
关键词 atmospheric TURBULENCE two-channel phase PERTURBATION EIKONAL variance
用于监控均值和方差的非参数变点模型
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作者 周茂袁 刘志敏 罗晓 《南开大学学报:自然科学版》 CAS CSCD 北大核心 2019年第4期81-85,共5页
统计过程控制被广泛应用于工业过程,服务领域和其他行业.尽管在特定过程的情况下参数控制图是有效的,但通常情况下都没有足够的信息确定过程分布,所以在此情况下非参数控制图是必要的.但大多非参数控制图要么是监控位置参数的,要么是监... 统计过程控制被广泛应用于工业过程,服务领域和其他行业.尽管在特定过程的情况下参数控制图是有效的,但通常情况下都没有足够的信息确定过程分布,所以在此情况下非参数控制图是必要的.但大多非参数控制图要么是监控位置参数的,要么是监控尺度参数的,而不是既可以监控位置参数又可以监控尺度参数的.通过整合Wilcoxon秩和检验和Ansari-Bradley检验到变点模型,提出了一个新的非参数控制图,并且模拟结果也展现了该控制图在探测位置和尺度漂移时,是优于其他的非参数控制图的. 展开更多
关键词 位置参数 尺度参数 统计过程控制 非参数
Analysis of the Dominant Types of Rural Tourism in Beijing Suburbs 预览
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作者 FU Hua ZHANG Mingqing MENG Tiantian 《景观研究:英文版》 2019年第4期83-89,共7页
Taking 140 administrative villages for tourism expert diagnostic training as the object, using the minimum variance method and spatial analysis method, this paper studied leading types of rural tourism industry in Bei... Taking 140 administrative villages for tourism expert diagnostic training as the object, using the minimum variance method and spatial analysis method, this paper studied leading types of rural tourism industry in Beijing based on a comprehensive analysis of the tourism business types in the villages. The results showed that rural tourism businesses are mostly the combination of many types, dominated by picking gardens and leisure farms, and the second dominant type is the combination of leisure farm and natural village household, with the clear regional distribution. The combined-business structure and its distribution is influenced by geographical location, natural conditions and industrial investment and many other factors. Water element is an important symbol of rural tourism in the suburbs of Beijing. The newly-emerging operation modes should be concluded in the scope of new format. 展开更多
关键词 Minimum variance method BEIJING SUBURBAN TOURISM CHARACTERISTIC BUSINESS type Distribution
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