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111.
三阶随机占优准则在证券选择中的应用   总被引:1,自引:0,他引:1  
通常可以用分布函数和分住数函数描述随机占优准则,Man-Chung Ng列举的两个例子说明在三阶随机占优条件下用两种方法得到的结论是不一致的,这与Levy的观点相反。该文分别将这两种方法描述的三阶随机占优准则用于上海证券市场的基金选择,发现用两种方法在应用中得到的结论并不总是一致的。由此验证用Levy提出的分位数方法描述的随机占优准则进行实证研究是不正确的,一阶和二阶条件除外。  相似文献   
112.
    
Monitoring is an important and costly activity in resource management problems such as containing invasive species, protecting endangered species, preventing soil erosion, and regulating contracts for environmental services. Recent studies have viewed optimal monitoring as a Partially Observable Markov Decision Process (POMDP), which provides a framework for sequential decision making under stochastic resource dynamics and uncertainty about the resource state. We present an overview of the POMDP framework and its applications to resource monitoring. We discuss the concept of the information content provided by monitoring systems and illustrate how information content affects optimal monitoring strategies. Finally, we demonstrate how the timing of monitoring in relation to resource treatment and transition can have substantial effects on optimal monitoring strategies.  相似文献   
113.
    
Well-being has a multidimensional nature as it depends on multifaceted factors such as material conditions and quality of life. The Organization for Economic Co-operation and Development (OECD) has developed the Better Life Index (BLI) as part of the OECD Better Life initiative to facilitate the better understanding of what drives well-being of people. The BLI is a three-level hierarchical composite indicator that covers several socio-economic aspects. In this paper, considering the entire hierarchical structure of the index, we introduce a bottom-up procedure for the aggregation of the components at each level. We formulate the assessment of BLI as a multiple objective programming (MOP) problem that facilitates the implementation of different concepts to derive different aggregation schemes. We incorporate the data from previous years into the normalization process of the indicators, to take into account the discrepancy on their observed values and smooth their deviations across the years. Also, we consider the public opinion about well-being that is captured from the worldwide responses in the web platform of OECD BLI. We incorporate the public opinion into the assessment models in the form of weight restrictions. In this way, we reduce the effect of compensation that might be imposed by the adopted modelling approach. We apply our methodology to the data of 38 countries (35 OECD and 3 non-OECD economies) for the year 2017. Our findings illustrate that the public opinion in the form of weight restrictions can effectively drive the optimization process and depict the collective preferences to the BLI scores.  相似文献   
114.
濮海坤 《价值工程》2013,(36):235-236
本文简述了可编程控制器(PLC)的基本特点和发展情况,介绍了PLC的顺序功能图、梯形图、功能模块图、指令表和结构文本等编程语言及其功能特点,阐述了PLC在编程过程中梯形图与指令表语言编程的规则和注意事项等。熟练掌握PLC程序的编程语言、编程方法及编程注意事项,对于PLC编程的快速入门及工程应用具有十分重要的意义。  相似文献   
115.
Agents’ perceptions on the state of the economy can be affected during economic crises. Tendency surveys are the main source of agents’ expectations. The main objective of this study is to assess the impact of the 2008 financial crisis on agents’ expectations. With this aim, we evaluate the capacity of survey-based expectations to anticipate economic growth in the United States, Japan, Germany and the United Kingdom. We propose a symbolic regression (SR) via genetic programming approach to derive mathematical functional forms that link survey-based expectations to GDP growth. By combining the main SR-generated indicators, we generate estimates of the evolution of GDP. Finally, we analyse the effect of the crisis on the formation of expectations, and we find an improvement in the capacity of agents’ expectations to anticipate economic growth after the crisis in all countries except Germany.  相似文献   
116.
杜国良  傅洪志 《经济地理》2006,26(6):1030-1032
在建设和谐社会的大背景下,节约和集约使用土地,充分发挥土地利用总体规划在调控经济结构和转变经济增长方式方面的调控作用具有深远的战略意义。文章提出了建设用地乘数,并把其应用于土地利用总体规划可行性评价工作中,旨在提高科学性和可操作性。  相似文献   
117.
118.
Shinji Yane 《Applied economics》2013,45(17):2337-2348
This article examines the robustness of efficiency score rankings across four distributional assumptions for trans-log stochastic production-frontier models, using data from 1221 Japanese water utilities (for 2004 and 2005). One-sided error terms considered include the half-normal, truncated normal, exponential and gamma distributions. Results are compared for homoscedastic and doubly heteroscedastic models, where we also introduce a doubly heteroscedastic variable mean model, and examine the sensitivity of the nested models to a stronger heteroscedasticity correction for the one-sided error component. The results support three conclusions regarding the sensitivity of efficiency rankings to distributional assumptions. When four standard distributional assumptions are applied to a homoscedastic stochastic frontier model, the efficiency rankings are quite consistent. When those assumptions are applied to a doubly heteroscedastic stochastic frontier model, the efficiency rankings are consistent when proper and sufficient arguments for the variance functions are included in the model. When a more general model, like a variable mean model is estimated, efficiency rankings are quite sensitive to heteroscedasticity correction schemes.  相似文献   
119.
    
This article evaluates the impact of credit constraints on the performance of Chinese agricultural wholesalers. We estimate a stochastic frontier function using transaction and credit data of agricultural wholesalers from across China to estimate the efficiency and productivity impacts of credit constraints on sales of affected agricultural wholesalers. Empirical results show that micro- and smaller wholesalers are disproportionally impacted by credit constraints and that eliminating these constraints would increase the sales of affected agricultural wholesalers by approximately 15%. Thus, policies aimed at providing credit access for these wholesalers would significantly boost the performance of smaller agricultural wholesalers while improving the overall performance of the Chinese food supply chain without requiring additional non-credit inputs.  相似文献   
120.
    
Overfishing and excess capacity in mostfisheries around the world have generated considerableand increasing concern about their biological and economic performance ramifications. Theseproblems, in part, stem from substantialinvestment in technical improvements to boats andequipment in fishing fleets, which exacerbatesexcess fishing capacity and low returns tofishing effort and investment, given regulatoryand biological constraints. However, little attempt hasbeen made to quantify the extent or effects oftechnical change in fisheries. In this paper, we usedetailed data on innovation patterns for 19vessels in the Sète trawl fleet of southernFrance to evaluate the contributions oftechnical change to catch rates. We find thatembodied technical change enhanced productivity by approximately one percent per year between 1985 and 1999, but that external (disembodied) events counteractedthis trend, causing a net output decline ofabout three percent per year.  相似文献   
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