Quantifying uncertainty in the biospheric carbon flux for England and Wales

Summary.  A crucial issue in the current global warming debate is the effect of vegetation and soils on carbon dioxide (CO₂) concentrations in the atmosphere. Vegetation can extract CO₂ through photosynthesis, but respiration, decay of soil organic matter and disturbance effects such as fire return it to the atmosphere. The balance of these processes is the net carbon flux. To estimate the biospheric carbon flux for England and Wales, we address the statistical problem of inference for the sum of multiple outputs from a complex deterministic computer code whose input parameters are uncertain. The code is a process model which simulates the carbon dynamics of vegetation and soils, including the amount of carbon that is stored as a result of photosynthesis and the amount that is returned to the atmosphere through respiration. The aggregation of outputs corresponding to multiple sites and types of vegetation in a region gives an estimate of the total carbon flux for that region over a period of time. Expert prior opinions are elicited for marginal uncertainty about the relevant input parameters and for correlations of inputs between sites. A Gaussian process model is used to build emulators of the multiple code outputs and Bayesian uncertainty analysis is then used to propagate uncertainty in the input parameters through to uncertainty on the aggregated output. Numerical results are presented for England and Wales in the year 2000. It is estimated that vegetation and soils in England and Wales constituted a net sink of 7.55 Mt C (1 Mt C = 10¹² g of carbon) in 2000, with standard deviation 0.56 Mt C resulting from the sources of uncertainty that are considered.     

解读人与自然的和谐

人与自然和谐包含着丰富和深刻的内涵 ,从理论层面上看 ,它应是人与自然互相适应的辩证统一 ;从实践层面上讲 ,它应是人与自然双方均处于既被改造又应保护的关系之中。必须反对在这个问题上的各种片面的观点与看法     

用声学测量预报等温淬火球墨铸铁强度

等温淬火球墨铸铁的机械性能与其声学性能相关。本文将两种碳当量球铁在８４５，８９９和９４５℃温度进行奥氏体处理，在２６０，３１６和３７１℃温度进行等温淬火得到证实。声学性能测量包括共振频率，声速和内耗。由共振频率转换成动态模量表示出这种关系可以用来预报球墨铸铁不同热处理条件下的机械性能。     

Some remarks on the physical models concerning two different approaches to inference in statistical process control

Summary For technological applications it can be useful to identify some simple physical mechanisms, which, on the basis of the available knowledge of the production process, may suggest the most appropriate approach to statistical control of the random quantities of interest. For this purpose the notion of rupture point is introduced firstly. A rupture point is characterized bym randomly arising out of control states, assumed to be mutually exclusive and stochastically independent. Shewhart's control charts seem to represent the natural statistical tool for controlling a rupture point; however it is shown that they are fully justified only when the hazard rates attached to the causes of failure are constant. Otherwise, typically in the presence of time increasing hazard rates, Shewhart's control charts should be completed by a preventive intervention rule (preventive maintenance). In the second place, the notion of dynamic instability point is introduced, which is specifically characterized by assuming that the random quantity of interest is ruled by a stochastic differential equation with constant coefficients. By discretization, developed according to a possibly new approach, it is shown that the former model reduces to an equation error model, which is among the simplest used in adaptive control, and thus particularly easy to deal with in regard to parameter estimation and the definition of the optimum control rule.     

基于顾客资源的动态竞争优势

随着市场竞争环境变化的加剧,企业战略竞争的基点正在从企业内部的资源转移到企业适应外部环境的动态能力上,顾客资源因能有效地衔接企业内部资源和外部环境机会而成为弥足珍贵的战略性资源,以顾客资源为基础构筑的核心竞争力正日益体现出强大的动态竞争优势。因此,企业只有通过加快转变企业的战略管理理念、重构企业内部的业务流程、改革传统的价值链模式和实施企业的顾客忠诚化管理等途径构筑基于顾客资源的动态竞争优势,才能将企业立于竞争的不败之地。     

Women's Changing Attitudes Toward Divorce, 1974–2002: Evidence for an Educational Crossover

This article examines trends in divorce attitudes of young adult women in the United States by educational attainment from 1974 to 2002. Women with 4‐year college degrees, who previously had the most permissive attitudes toward divorce, have become more restrictive in their attitudes toward divorce than high school graduates and women with some college education, whereas women with no high school diplomas have increasingly permissive attitudes toward divorce. We examine this educational crossover in divorce attitudes in the context of variables correlated with women's educational attainment, including family attitudes and religion, income and occupational prestige, and family structure. We conclude that the educational crossover in divorce attitudes is associated most strongly with work and family structure variables.     

乌鲁木齐县安宁渠镇社会经济变化调查报告

该文通过对乌鲁木齐县安宁渠镇的调查 ,揭示了城镇化进程中所发生的社会经济变化 ,以及这一变化所产生的后果 ;论述了加快安宁渠镇发展急需解决的问题 ,即社会意识整合问题、知识更新问题、基础设施建设问题、体制问题等。     

斜腿刚构桥几何布局的优化设计

采用数学规划的方法从静力和动力两方面对斜腿刚构桥的几何布局进行优化设计。静力优化设计的优化目标是截面截面应力平方均值最小，动力优化设计的优化目标是结构自振周期平方和最小。采用了直接搜索法寻优。通过算例可知，这两种优化设计方法均可行，且均为刚性设计。     

基于可达性的用户最优动态交通配流模型研究

以多种已有模型为基础，建立了动态配流流量细化原则，并依据这一原则，在避免估算路段走行时间的情况下构造了一个改进的新模型．该模型的解释性强，具有全局收敛性，并考虑了距离不同带来的可达性的影响．在对该模型最优解条件的充要性进行说明的同时，对新模型的择路机理也予以了推证．     

生物学中的相异构想及转变探讨

研究表明，学生学习科学的过程是一种由前概念向科学概念转变的过程。学生头脑中形成的与科学概念不一致的相异构想是造成学生学习困难的重要原因。本文分析了学生在生物学学习中相异构想的成因及来源，并在此基础上提出了生物学教学中相异构想的转变模式及策略。