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31.
In climatology and hydrology, univariate Extreme Value Theory has become a powerful tool to model the distribution of extreme events. The Generalized Pareto Distribution (GPD) is routinely applied to model excesses in space or time by letting the two GPD parameters depend on appropriate covariates. Two possible pitfalls of this strategy are the modeling and the interpretation of the scale and shape GPD parameters estimates which are often and incorrectly viewed as independent variables. In this note we first recall a statistical technique that makes the GPD estimates less correlated within a Maximum Likelihood (ML) estimation approach. In a second step we propose novel reparametrizations for two method-of-moments particularly popular in hydrology: the Probability Weighted Moment (PWM) method and its generalized version (GPWM). Finally these three inference methods (ML, PWM and GPWM) are compared and discussed with respect to the issue of correlations. 相似文献
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Jian Hua Li Zheng Ping Zhang Rui Huan Jing Chong Fu Huang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(4):485-492
In this paper, we introduce a value chain approach, on the view of the value chain analytic in business management, to be
the framework of a crisis response system serving for crisis management strategy in identifying risk sources, responding to
unexpected events, and recovering from a shock. This system is not only a computer system but also a system of governmental
emergency response mechanism and it is tremendous and complex. The system integrates and coordinates the correlative resources
of emergency response units of the city. We consider the efficiency of the system. In addition, the run cost of the system
also is taken into account. Based on this framework, the Qingdao’s practical situation is analyzed. As a result, a design
proposal of the Qingdao’s crisis response system is put forward. 相似文献
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随着煤层气勘探的不断深入,对煤层含气量预测精度提出了更高的要求。基于煤层含气量测井响应特征,分析测井参数与含气量的相关性,提出MIV(Mean Impact Value)技术与LSSVM(Least Squares Support Vector Machine)结合的测井参数优选策略,优选最优测井参数作为网络建模的输入自变量组合,通过粒子群算法优化LSSVM网络核心参数,最后构建一套适用于煤层含气量预测的MIV-PSO-LSSVM模型。在此基础上,分别对比分析LSSVM、PSO-LSSVM、MIV-LSSVM和MIV-PSO-LSSVM模型对煤层含气量的预测性能,并与传统多元回归方法进行了对比,利用拟合优度和均方根误差对此5类模型进行评价。结果表明:PSO优化下的LSSVM模型预测精度得到有效提升,结合MIV方法优选测井参数可大幅度改善神经网络建模性能,MIV-PSO-LSSVM模型可实现煤层含气量高精度预测,为煤层气勘探及其储层评价提供新的技术支撑,且本研究的建模策略及思想可广泛应用于其他机器学习建模研究领域。 相似文献
37.
Flood occurrence has always been one of the most important natural phenomena, which is often associated with disaster. Consequently,
flood forecasting (FF) and flood warning (FW) systems, as the most efficient non-structural measures in reducing flood loss
and damage, are of prime importance. These systems are low cost and the time required for their implementation is relatively
short. It is emphasized that for designing the components of these systems for various rivers, climatic conditions and geographical
settings different methods are required. One of the major difficulties during implementing these systems in different projects
is the fact that sometimes the main functions of these systems are ignored. Based on a systematic and practical approach and
considering the components of these systems, it would be possible to extract the most essential key functions of the system
and save time, effort and money by this way. For instance, in a small watershed with low concentration and small lead time,
the main emphasis should be on predicting and monitoring weather conditions. In this article, different components of flood
forecasting and flood warning systems have been introduced. Then analysis of the FF and FW system functions has been undertaken
based on the value engineering (VE) technique. Utilizing a functional view based on function analysis system technique (FAST),
the total trend of FF and FW functions has been identified. The systematic trend and holistic view of this technique have
been used in optimizing FF and FW systems of the Golestan province and Golabdare watersheds in Iran as the case studies. 相似文献
38.
Richard Titmuss’ classical 1970 study of blood donation has provided a powerful conceptual model for characterising transactions involving human bodily materials. This now paradigmatic model suggests that such transactions are typically organised in accordance with one or other of two dichotomous, and mutually exclusive, modes of exchange: gifting or commodification. In this paper I utilise findings from my own and others’ empirical research to illustrate the range of complex, multiply constituted, and contested modes of commodification that now typically attend the exchange of human body parts and tissues of which Titmuss’ model can take no effective account. Drawing on work by Radin, Callon, and Miller I illustrate the complex justificatory work that those involved must perform to fit their lived experiences of tissue exchange into this now outmoded paradigm. I then consider how the protagonists themselves ontologise their practices and with what effects. In the second part of the paper I consider how neo-liberal ideologies and instruments are being employed to suborn a variety of highly differentiated and geographically distinct practices of bodily commodification to the ‘logic of the market’. I explore here what the operative effects of defining the global circulation of body parts and tissues as a new ‘economy’ might be. I then consider how, if at all, a market logic could ‘Value’ all those ‘calculations of interest’ and ‘values’ that underpin exchanges of human body parts and tissues in specific national, communal or institutional settings. I conclude by reflecting on the desirability or possibility of performing normative assessments of the ethicacy of highly geographically and culturally differentiated practices of bodily commodification. 相似文献
39.
《Marine Policy》2016
Vertical chain collaboration is a strategy for customers’ value creation. However, Dutch fishermen are hardly participating in integrated value chains. While supply chain literature describes factors that contribute to successful chain partnerships, scarce research has been done on the dynamics of the sociocultural context for chain collaboration.In 10 semi-structured interviews, representatives of supply chain parties were asked for their perceptions on chain collaboration, trust, and the role of the local community. The interviews were directed at obtaining so-called ‘tacit’ knowledge, the non-spoken codified truths of social networks. Without generalizing, this research provides benchmarks to monitor how the different domains, laid out in this study, impact chain collaboration: community values, network participation and company competences. An overview is given of socio-economic factors blocking and enhancing chain collaboration at company and community level. Factors such as the strong bonding of family with business in tightly knit networks, a high level of social control, entrepreneurial autonomy, and loyalty as community norm hamper collaboration within the supply chain.Respondents’ discourse demonstrates that cultural codes and identity form the very core of the entrepreneur, driving rather than ‘embedding’ economic behavior. Kinship, religion and peer pressure determine ‘windows on the world’ when engaging in chain collaboration. Consequently, any analysis of economics that does not integrate sociological and psychological methodology is flawed from the outset. 相似文献
40.
刘新国 《中国海洋大学学报(自然科学版)》1989,(3)
本文讨论一类求解线性最小二乘问题的正则化方法的可行性。给出两条较为实用的可行性检验准则,推广了经典的Greville定理。 相似文献