Bayesian density regression for discrete outcomes

We develop Bayesian models for density regression with emphasis on discrete outcomes. The problem of density regression is approached by considering methods for multivariate density estimation of mixed scale variables, and obtaining conditional densities from the multivariate ones. The approach to multivariate mixed scale outcome density estimation that we describe represents discrete variables, either responses or covariates, as discretised versions of continuous latent variables. We present and compare several models for obtaining these thresholds in the challenging context of count data analysis where the response may be over‐ and/or under‐dispersed in some of the regions of the covariate space. We utilise a nonparametric mixture of multivariate Gaussians to model the directly observed and the latent continuous variables. The paper presents a Markov chain Monte Carlo algorithm for posterior sampling, sufficient conditions for weak consistency, and illustrations on density, mean and quantile regression utilising simulated and real datasets.     

城市群高质量发展背景下人口聚散规律和驱动因素研究

人口与经济协调发展是城市群发展方式更易实现的目标。影响城市群人口聚散的驱动因素有些方面与城市类似:可分为由资源环境决定的内在驱动因素和政策导向、公共服务水平等主导的外在驱动因素。在市场与政府的共同作用下,内在与外在要素分别通过内链与外链形成两条相互影响的驱动路径共同影响人口聚散;有些则不同:城市群内各城市间可通过“规模借用”与“功能借用”实现要素的交换与替代,更易于克服内在和外在驱动因素壁垒,整体实现资本、人力资源等要素的更高配置效率。在对城市群人口聚散规律及驱动因素进行辨析的基础上,利用生产函数构建数理模型,引入资源要素与政策要素,并以首都都市圈中“一核两翼”结构为例进行了仿真分析,探究各驱动要素对人口聚散的作用强度与实现路径。实现人口疏解与承接的关键是提高城市间要素的可替代性与驱动弹性,城市群间可通过合作机制(借用规模)实现要素的交换与替代。在此基础上,提出促进城市群人口数量和分布合理化的思路:正确认识城市群人口承载力与城市功能定位的内涵;以高质量发展战略为契机,强化市场作用,以产业合理布局带动城市间人口合理分布;改革管理体制,降低省际边界障碍和户籍障碍,推进城市群内部的公共服务与基础设施水平均等化,促进形成与城市群和群中各城市功能定位相匹配的人口聚散形式。     

色散特性对毫米波频率步进雷达影响的研究

对影响毫米波频率步进雷达分辨率的主要因素进行了分析。除目标速度以外,为毫米波频率步进雷达提供频率信号的频率源的色散特性也会对雷达分辨率造成恶化影响。微波频段上的色散特性会被搬移到毫米波频段,导致毫米波发射信号和本振信号的初始相位差不为常数,对雷达系统尤其是距离分辨率造成严重影响。仿真结果与实验结果一致。为了抵消色散特性对雷达分辨率的恶化影响,可以通过对色散特性的补偿来实现。色散特性补偿的方法被应用到实现W波段频率步进频率源的设计中,满足了0.45m距离分辨率的要求。     

内开槽螺纹波导冷腔色散特性模拟研究

根据螺纹波导中模式间的耦合方程组及冷腔色散方程进行了数值计算,分析了2个模式的相互耦合机理。基于圆柱形波导中线性极化TE11模式存在极化简并的特性,将线极化TE11脉冲作为1个探针,采用粒子模拟软件对该腔体进行了3维冷腔模拟;并将模拟结果与数值计算结果进行了比较,两者基本一致。通过计算机模拟得出了混合模式的电场等位线分布图,结合色散方程数值计算分析了内开槽螺纹几何特性变化对波导色散特性的影响规律。     

具有复合周期磁场的电子回旋脉塞

本文从降低回旋脉塞中直流磁场的角度出发,利用线性伏拉索夫——麦克斯韦方程组,对通过静态复合周期磁场的弱相对论电子注与缓变圆波导中沿纵向作任意缓变的TE_(mn)模式之间的互作用机理,在理论上进行了详细的分析和讨论,导出了色散方程并作了数值计算。分析和计算表明,由于采用了静态复合周期磁场,其电子注与波互作用的不稳定性产生在电子回旋共振条件下,从而可以在不同的电子回旋空间谐波上工作而大大地降低直流磁场。     

On Unimodal Regression in the Exponential Family

In this article, we discuss statistical methods for curve-estimation under the assumption of unimodality for variables with distributions belonging to the two-parameter exponential family with known or constant dispersion parameter. An important special case is a one-parameter distribution. We suggest a nonparametric method based on monotonicity properties. The method is applied to Swedish data on laboratory verified diagnoses of influenza and data on inflation from an episode of hyperinflation in Bulgaria.     

A Generalization of Hotelling's T 2

ABSTRACT

We derive an asymptotic version of Hotelling's T ² for the multivariate proper dispersion models of Jøtrgensen and Lauritzen (2000 Jørgensen , B. , Lauritzen , S. L. ( 2000 ). Multivariate dispersion models . J. Multivariate Anal. 74 : 267 – 281 . [CSA] [CROSSREF]  [Google Scholar]), the main tool being the saddlepoint approximation. Multivariate dispersion models are suitable for positive, directional, compositional, and other non normal data. We illustrate the results by a multivariate gamma model.     

The robustness of point optimal testing for rosenberg random regression coefficients

The literature on testing for the presence of Rosenberg's (1973) return to normalcy random coefficient model is well developed with both Shively (1988) and Brooks (1993) advocating the use of point optimal tests. This paper explores the robustness of point optimal testing for the Rosenberg alternative to two departures: the special case HildrethHouck (1968) alternative and non-normality in regression disturbances, finding the point optimal testing approach to be fairly robust to both departures.     

MDEWMA chart: an efficient and robust alternative to monitor process dispersion

Control chart is the most important statistical process control tool used to monitor changes in process location and dispersion. In this study, an EWMA control chart is proposed for efficient and robust monitoring of process dispersion. The proposed chart, namely the MDEWMA chart, is based on estimating the process standard deviation (σ) using the mean absolute deviations (MD), taken from the sample median. The performance of the proposed chart has been compared with the EWMASR chart (a dispersion EWMA chart based on sample range) and MD chart (a Shewhart-type dispersion chart based on MD), under the existence and violation of normality assumption. It has been observed that the proposed MDEWMA chart is more efficient and robust when compared with both EWMASR and MD charts in terms of run length (RL) characteristics such as average RL, median RL and standard deviation of the RL distribution.     

Distance equalizers

Distance equalizers are introduced as empirical measures of central tendency that make distances to univariate data as similar as possible. These measures are made precise by means of various so-called fluctuation functions which account for distances in different ways. Distance equalizers differ from the mean as well as from the median. Also, distance equalizers relate to dispersion measures. Algorithms and closed-form solutions for special cases are given. Some computations require to perform multiextremal function minimization. Distance equalization is extendable to data from higher dimensions and to function quantization in signal processing.