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51.
近几十年来.由于人类活动导致大气中CO2含量呈明显上升趋势,预计到下世纪中叶CO2浓度将达到450ppm左右,下世纪末,将达到工业革命前的两倍,各种数值模式表明,届时全球气温将升高1.5-4.5℃。  相似文献   
52.
本文对N个人验血的检验方法进行研究.得到如下结果:(1)设普查对象的阳性概率为p,对当时,采用分组检验最优;当p≥0.3078时,采用单个检验最优、(2)当采用分组检验时,分组人数或时,检验次数最少.  相似文献   
53.
Rubinstein (1982) considered the problem of dividing a given surplus between two players sequentially, and then proposed a model in which the two players alternately make and respond to each other's offers through time. He further characterized the perfect equilibrium outcomes, which depend on the players time preferences and order of moves. Using both equal and unequal bargaining cost conditions and an unlimited number of rounds, two experiments were designed to compare the perfect equilibrium model to alternative models based on norms of fairness. We report analyses of final agreements, first offers, and number of bargaining rounds, which provide limited support to the perfect equilibrium model, and then conclude by recommending a shift in focus from model testing to specification of the conditions favoring one model over another.  相似文献   
54.
The difficulty of making social choices seems to take on two forms: one that is related to both preferences and the method used in aggregating them and one which is related to the preferences only. In the former type the difficulty has to do with the discrepancies of outcomes resulting from various preference aggregation methods and the computation of winners in elections. Some approaches and results which take their motivation from the computability theory are discussed. The latter institution-free type of difficulty pertains to solution theory of the voting games. We discuss the relationships between various solution concepts, e.g. uncovered set, Banks set, Copeland winners. Finally rough sets are utilized in an effort to measure the difficulty of making social choices.  相似文献   
55.
品牌基础问题研究评述   总被引:3,自引:0,他引:3  
王方华  陈洁 《管理学报》2006,3(5):622-628
品牌问题一直是国际营销学术界的研究热点领域。对文献总结发现,在品牌基础问题的理论和方法研究中,主要集中在品牌认识、品牌选择和品牌发展3个方面。国内外研究者从不同的理论出发运用不同方法解释了品牌的认识、选择和发展,主要是分别从消费者和企业2个角度来分析和探讨品牌问题,但是缺乏二者之间互动关系的研究,使得品牌基础问题的研究不能为企业品牌创建、品牌战略和品牌延伸提供合理建议。  相似文献   
56.
有效数字是大学化学实验课程的主要教学内容之一,是培养学生在课程中理解并在日常学习与工作中规范使用有效数字,提升其对有效数字与测定误差之间关系的认识水平,树立良好规范的数字记录习惯,具有十分重要的现实意义。论述介绍了目前大学化学实验教学中关于有效数字方面存在的主要问题,并采用相应的举措建立和完善了教学方案以利于更好地解决存在的问题。通过几个学期的教学实践发现新教学方案取得了初步的成效,同时严格按照有效数字的要求记录与计算数据也是培养学生具有严谨科学素养的一条重要途径。  相似文献   
57.
In this paper, semiparametric methods are applied to estimate multivariate volatility functions, using a residual approach as in [J. Fan and Q. Yao, Efficient estimation of conditional variance functions in stochastic regression, Biometrika 85 (1998), pp. 645–660; F.A. Ziegelmann, Nonparametric estimation of volatility functions: The local exponential estimator, Econometric Theory 18 (2002), pp. 985–991; F.A. Ziegelmann, A local linear least-absolute-deviations estimator of volatility, Comm. Statist. Simulation Comput. 37 (2008), pp. 1543–1564], among others. Our main goal here is two-fold: (1) describe and implement a number of semiparametric models, such as additive, single-index and (adaptive) functional-coefficient, in volatility estimation, all motivated as alternatives to deal with the curse of dimensionality present in fully nonparametric models; and (2) propose the use of a variation of the traditional cross-validation method to deal with model choice in the class of adaptive functional-coefficient models, choosing simultaneously the bandwidth, the number of covariates in the model and also the single-index smoothing variable. The modified cross-validation algorithm is able to tackle the computational burden caused by the model complexity, providing an important tool in semiparametric volatility estimation. We briefly discuss model identifiability when estimating volatility as well as nonnegativity of the resulting estimators. Furthermore, Monte Carlo simulations for several underlying generating models are implemented and applications to real data are provided.  相似文献   
58.
In this paper, we introduce classical and Bayesian approaches for the Basu–Dhar bivariate geometric distribution in the presence of covariates and censored data. This distribution is considered for the analysis of bivariate lifetime as an alternative to some existing bivariate lifetime distributions assuming continuous lifetimes as the Block and Basu or Marshall and Olkin bivariate distributions. Maximum likelihood and Bayesian estimators are presented. Two examples are considered to illustrate the proposed methodology: an example with simulated data and an example with medical bivariate lifetime data.  相似文献   
59.
This paper explores one aspect of unresolved trauma, namely dissociation. Its relevance to child protection is discussed with reference to two aspects: emotional neglect and choice of partner. There is an exploration of the implications for both assessment and treatment. The central place of shame in relation to dissociation is also explored. It is argued that dissociation is an important concept in child protection assessments and that social work assessments should be alert to this.  相似文献   
60.
We study how well individuals in a face-to-face situation can delude others. We exploit data from a laboratory experiment in which participants were asked to assess video-taped statements as being rather truthful or untruthful. The statements are face-to-face tax declarations. The video clips feature each subject twice making the same declaration: One time the subject is reporting honestly, and the other time willingly dishonestly. This allows us to investigate within-subject differences in perceived truthfulness. Our study provides several novel insights. We find that individuals can cover up their lies successfully. On average, a subject is perceived as more truthful if she deceives than if she reports honestly. In particular, individuals with a genuine dishonest appearance manage to increase their perceived truthfulness by up to 14 percent when lying. Moreover, our results show that a subject appears less truthful if she had previously been caught lying. Being detected as a liar previously appears to impair self-confidence and to thereby lower an individual’s ability to deceive.  相似文献   
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