A Geometric Examination of Linear Model Assumptions

From a geometric perspective, linear model theory relies on a single assumption, that (‘corrected’) data vector directions are uniformly distributed in Euclidean space. We use this perspective to explore pictorially the effects of violations of the traditional assumptions (normality, independence and homogeneity of variance) on the Type I error rate. First, for several non‐normal distributions we draw geometric pictures and carry out simulations to show how the effects of non‐normality diminish with increased parent distribution symmetry and continuity, and increased sample size. Second, we explore the effects of dependencies on Type I error rate. Third, we use simulation and geometry to investigate the effect of heterogeneity of variance on Type I error rate. We conclude, in a fresh way, that independence and homogeneity of variance are more important assumptions than normality. The practical implication is that statisticians and authors of statistical computing packages need to pay more attention to the correctness of these assumptions than to normality.     

Underground storage tanks (UST): A closer investigation statistical implications to changing the shape of a UST

ABSTRACT

Gasoline service stations that use underground storage tanks (UST) assume that the manufactured tank is an ideal cylindrical shape. This cross-sectional shape plays a crucial role in determining a functional form for the volume of liquid that remains inside the tank. In industry, these formulas are used to compute strapping charts. But realistically, the manufacture, assembly, and installation of a tank may have deviation from the actual tank design (for which strapping charts had been developed). A theoretical volume function (based on tank dimensions) is used alongside of statistical methodology to reconcile volume differences in gasoline dispensed at the pump meters versus that displaced inside the tank. Statistical inventory reconciliation of this nature falls within the family of leak detection methods approved by the EPA (Environmental Protection Agency) and the California Water Resources Board. This methodology can also be used to assess deformation of the cross-sectional shape of the tank. We consider a deformation to an ellipse. Through simulation, we estimate the tank dimensions based on a nonlinear model with normal errors. The use of normal errors naturally facilitates a likelihood ratio test. Through this exploration, an approximation function is developed to help improve the power of the likelihood ratio test.     

Blind source separation filters-based-fault detection and isolation in a three tank system

Fault detection and Isolation takes a strategic position in modern industrial processes for which various approaches are proposed. These approaches are usually developed and based on a consistency test between an observed state of the process provided by sensors and an expected behaviour provided by a mathematical model of the system. These methods require a reliable model of the system to be monitored which is a complex task. Alternatively, we propose in this paper to use blind source separation filters (BSSFs) in order to detect and isolate faults in a three tank pilot plant. This technique is very beneficial as it uses blind identification without an explicit mathematical model of the system. The independent component analysis (ICA), relying on the assumption of the statistical independence of the extracted sources, is used as a tool for each BSSF to extract signals of the process under consideration. The experimental results show the effectiveness and robustness of this approach in detecting and isolating faults that are on sensors in the system.     

智库学：学科基础·现实困境·可能路径

加强中国特色新型智库建设,推进国家治理体系和治理能力现代化,需要构建中国特色智库学,以推进对智库建设的特点、本质、发展规律和运行机制等方面的研究。智库学作为一门新兴学科,学科意识淡薄、学科定位模糊、学科知识不全,虽已基本具备作为一门独立学科的学科标准,但目前尚处于前学科状态。推动中国特色新型智库建设,要推进智库研究的学科化,加强对智库学的学科范畴、基本规律以及学科架构等智库学元理论问题研究。     

新型高校智库建设需要把握的几个问题

当今世界,智库已成为影响政府决策、推动社会发展的重要力量,成为国家“软实力”的重要组成部分。面对复杂多变的决策环境,为了提高决策的科学性,更多的政府机构选择“借脑”的方式,力求决策的专业化,提高决策的科学性。作为知识生产、传播和转化的重地,高校具有学科齐全、人才密集等优势,这些优势成为高校智库快速发展的有利条件。新型高校智库建设,应重点把握国家战略需求这一根本出发点,把握高校优势这一立足点,把握机制创新这一着力点,把握在“高原”上建造“高峰”的发展思路,着力解决人才缺乏、成果转化、品牌打造等方面的重点、难点问题。     

智库产品质量标准模型构建研究

智库产品质量是智库生存和发展的基石，对智库产品质量的控制和管理是智库建设的关键环节；标准化是质量管理的基础和手段，制定和实施智库产品质量标准有利于加强和完善质量管理、有效提升产品质量，并为科学评价提供参考依据，因此构建智库产品质量标准具有深刻的理论和现实意义。论文首先界定了智库产品，分析了智库产品质量标准的基本内涵；其次采用文献调研、调查问卷、专家访谈等方法明确了智库产品质量标准核心要素；在此基础上遵循四大原则，构建了由环境、资源、过程、成果、影响效果等五要素组成的PRICE"蛛网式"智库产品质量标准模型。     

基于失效模式分析的脱硫罐全面检验

基于脱硫罐结构以及脱硫工艺分析,研究脱硫罐的失效模式,应力集中是其产生裂纹导致疲劳失效的主要原因。在此基础上采用宏观检查、超声波测厚、表面磁粉检测等检测方法对脱硫罐进行全面检测,安全评定脱硫罐的失效现状,同时提出了此类压力容器安全运行及检验的改进建议,提高安全监管的科学性和有效性,避免事故的发生,确保设备安全、长周期运行。     

智能钻杆导电环结构有限元分析

导电环是智能钻杆导电性能及可靠性的关键。介绍了加工的智能钻杆导电环结构，结构中的内导电环和外导电环分别位于钻杆母接头和公接头的螺纹内径端部，它们之间的柱面接触实现了钻杆接头处的电力及信号导通。对室内钻杆上卸扣试验中导电环的变形过程进行了受力分析，得出轴向力F 是导致导电环变形的主要原因。采用有限元分析方法分别对内外导电环的接触过程和单个导电环受轴向力F 时的变形状态进行了数值模拟。模拟结果分析表明，将内外导电环过盈配合时的过盈量控制在0.024 mm 以下，结合面锥度控制在1：5 以上时，导电环在钻杆上卸扣过程中不会产生塑性变形，具有较高的可靠性。     

曲面零件冲压成形内皱发生时刻的分析

本文利用内皱模型，结合曲面零件在成形过程中的几何条件及应力分析分别推导了圆锥形零件和球形零件不发生内皱的临界条件；通过对临界条件的数学分析进而得到了曲面零件在成形过程中内皱发生的具体时刻。综合上述结果得到了曲面零件成形过程中不用压边也不发生内皱的判 据。     

Fejér定理的一种多元推广

将一元傅立叶分析中关于傅氏级数及其共轭级数之间的收敛性关系的 Fejér 定理推广到多元情形。主要结果为定理:若函数 f∈L(E_k)(k≥2)的傅氏积分的球形平均σ_R(f;x)在域 D 内一致收敛,则它的共轭傅氏积分韵球形平均(?)_R(f;x)在其(C,1)可和点处一定收敛。