Markov chain Monte Carlo methods for high dimensional inversion in remote sensing

Summary.  We discuss the inversion of the gas profiles (ozone, NO₃, NO₂, aerosols and neutral density) in the upper atmosphere from the spectral occultation measurements. The data are produced by the 'Global ozone monitoring of occultation of stars' instrument on board the Envisat satellite that was launched in March 2002. The instrument measures the attenuation of light spectra at various horizontal paths from about 100 km down to 10–20 km. The new feature is that these data allow the inversion of the gas concentration height profiles. A short introduction is given to the present operational data management procedure with examples of the first real data inversion. Several solution options for a more comprehensive statistical inversion are presented. A direct inversion leads to a non-linear model with hundreds of parameters to be estimated. The problem is solved with an adaptive single-step Markov chain Monte Carlo algorithm. Another approach is to divide the problem into several non-linear smaller dimensional problems, to run parallel adaptive Markov chain Monte Carlo chains for them and to solve the gas profiles in repetitive linear steps. The effect of grid size is discussed, and we present how the prior regularization takes the grid size into account in a way that effectively leads to a grid-independent inversion.     

Goodness of fit for the inverse Gaussian distribution

For testing the fit of the inverse Gaussian distribution with unknown parameters, the empirical distribution-function statistic A² is studied. Two procedures are followed in constructing the test statistic; they yield the same asymptotic distribution. In the first procedure the parameters in the distribution function are directly estimated, and in the second the distribution function is estimated by its Rao-Blackwell distribution estimator. A table is given for the asymptotic critical points of A². These are shown to depend only on the ratio of the unknown parameters. An analysis is provided of the effect of estimating the ratio to enter the table for A². This analysis enables the proposal of the complete operating procedure, which is sustained by a Monte Carlo study.     

Assessing accuracy of a continuous screening test in the presence of verification bias

Summary.  In studies to assess the accuracy of a screening test, often definitive disease assessment is too invasive or expensive to be ascertained on all the study subjects. Although it may be more ethical or cost effective to ascertain the true disease status with a higher rate in study subjects where the screening test or additional information is suggestive of disease, estimates of accuracy can be biased in a study with such a design. This bias is known as verification bias. Verification bias correction methods that accommodate screening tests with binary or ordinal responses have been developed; however, no verification bias correction methods exist for tests with continuous results. We propose and compare imputation and reweighting bias-corrected estimators of true and false positive rates, receiver operating characteristic curves and area under the receiver operating characteristic curve for continuous tests. Distribution theory and simulation studies are used to compare the proposed estimators with respect to bias, relative efficiency and robustness to model misspecification. The bias correction estimators proposed are applied to data from a study of screening tests for neonatal hearing loss.     

高等教育制度改革后贫困大学生心理健康问题浅析

本文阐述了高等教育制度改革后贫困大学生的心理健康问题,分析了贫困大学生心理健康问题的原因,并提出了化解贫困大学生心理健康问题的对策。     

Joint tests of non-nested models and general error specifications

This paper is concerned with joint tests of non-nested models and simultaneous departures from homoskedasticity, serial independence and normality of the disturbance terms. Locally equivalent alternative models are used to construct joint tests since they provide a convenient way to incorporate more than one type of departure from the classical conditions. The joint tests represent a simple asymptotic solution to the “pre-testing” problem in the context of non-nested linear regression models. Our simulation results indicate that the proposed tests have good finite sample properties.     

CAI——信息时代的教育手段

计算机辅助教学是信息时代的教育手段之一。本文介绍了CAI系统及其应用,并探讨了目前CAI在学校应用中存在的问题、发展策略,说明CAI在学校教育中的重要性和作用。     

Industry and the environment: a case study of cleaner technologies in selected European countries

The aim of this case study is to discuss the role of technology in addressing environmental problems. The paper tries to scratch beneath the surface of the increasingly frequent ‘quick-fix’ solutions to the present environmental problems, based on such beguiling catchwords as Cleaner Technologies, Best Available Technologies, and Best Available Technologies Not Exceeding Excessive Costs, etc., in an attempt to discover whether there is any substance in them, or whether they are just full of hot air. Recent data from case studies performed by the author in Germany and Finland as well as a postal questionnaire in Denmark are presented. The paper analyses and discusses the roles and responsibilities of designers, industrialists, and government policy-makers. It is argued that existing regulatory regimes, supranational industrial structures, and market mechanisms do not favour the development of cleaner technologies, nor do they promote a reduction in consumption patterns. Evidence from ongoing empirical research in Northwest Europe suggests that industry is far from developing and/or implementing cleaner technologies. The paper closes with a discussion of some of the policy implications involved and some examples of urgently needed further research.     

The impact and management of cognitive gap in high performance product development organizations

The close alignment of applied research and development units with manufacturing operational structures can provide excellent opportunities for maintaining robust product pipelines and reducing product development cycle times. Within such an integrated organizational model (IOM), however, lies a potentially disruptive psychological mechanism that can lead to the dissolution of this delicate partnership if it is not handled properly. This mechanism is cognitive gap, which can take several basic forms: first, as differences between the nature and difficulty of the problem at hand and the cognitive resources of the problem solvers tasked with its solution; and second, as differences between the cognitive abilities and approaches of the problem solvers themselves. In this paper, we define and discuss cognitive gap within the context of Kirton's Adaption-Innovation theory, a useful framework for understanding problem solving (and problem solvers) in general. Specific implications (both favourable and potentially destructive) of cognitive gaps for high performance product development organizations are discussed, and suggestions for their effective management are offered.     

论我国目前行政问责制的突出问题及对策探微

目前我国在行政问责制方面还存在一些问题:行政问责的范围不清、对象不明确;行政问责的主体缺位、有名无实;行政问责的法律体系不健全、无程序性。因此,有必要寻求问责制之出路:规范行政问责原则;明确行政问责范围;健全行政问责法律;强化行政问责意识。     

语用学维度:人工智能框架问题与自然语言理解

语用学的基本理论有助于从语言的本质在于使用的角度来理解智能,为人工智能的框架问题提供哲学的视域和分析方法。现代人工智能的符号逻辑研究框架在哲学意义上具有脱离经验的根本局限性,联结论研究框架实质上与此相同。人工智能的框架问题研究需要奠基于"自然机制"为内核、"算法机制"为辅的哲学纲领。现代自然语言理解的句法和语义研究是脱离使用者与语境知识而处于指称层次的片面理解,而只有基于语用学层次的理解才是完整的。