RSS技术的应用和发展趋势探讨

RSS是以XML为基础,用于为内容整合客户端提供选择性的、汇总过的Web内容的技术规范。由于RSS具有简单、规范、通用、容易自动生成等特点,因此越来越多的网站也采用这种方式来发布最新信息。本论文先阐述RSS及其相关技术,接着提出RSS阅读器的一个具体实现,最后对RSS的发展趋势进行深一步的探讨。     

A Global Ex-vessel Fish Price Database: Construction and Applications

Synopsis We describe the first effort at creating a global ex-vessel fish price database, which is required for understanding the economic behavior of participants in the world’s fisheries. We demonstrate potential applications of the database by linking it to a spatially defined catch database, which makes it possible to attach landed values to species in both time and space. This is the first database available publicly where interested members of the public, researchers and managers can easily find and access ex-vessel prices of the world’s major commercial fish species. Preliminary results indicate that the average real price of a number of species have declined between 1950 and 2002. The estimated landed value of fish globally, in year 2000 dollars, was about US$24 billion in 1950. It increased steadily to about US$90 billion in the early 1970s, reached a peak of US$100 billion at the end of the 1980s, and declined to about US$80 billion in 2000. The top 15 fishing countries cumulatively account for 79% of total real landed value, with Japan leading, even though the value of its landings has been declining.      

通过加总推出的总供给曲线

总供给曲线的推导是宏观经济学中的最重要内容之一。在大多数宏观经济模型中 ,在推导总供给曲线时 ,加总问题 (aggregationproblem)往往被忽略。一般认为 ,总供给曲线是各企业供给曲线的简单算术和或是一个代表性企业供给曲线的简单放大。但是 ,在现实中 ,各个企业是不同的。只有在非常严格的条件下 ,总供给曲线与企业供给曲线在性质上才是等价的。考虑到中国经济的制度性特点并在解决加总的一系列技术问题的基础上 ,本文推导出了在企业劳动生产率服从均匀分布情况下的总供给曲线。通过这种方法推出的总供给曲线具有许多传统总供给曲线所不具有的新性质。笔者希望本文能为进一步研究处于微观经济和宏观经济之间的往往被忽视的一块重要领域 (“中观经济领域”)做出贡献。     

Social learning with private and common values

Summary. We consider an environment where individuals sequentially choose among several actions. The payoff to an individual depends on her action choice, the state of the world, and an idiosyncratic, privately observed preference shock. Under weak conditions, as the number of individuals increases, the sequence of choices always reveals the state of the world. This contrasts with the familiar result for pure common-value environments where the state is never learned, resulting in herds or informational cascades. The medium run dynamics to convergence can be very complex and non-monotone: posterior beliefs may be concentrated on a wrong state for a long time, shifting suddenly to the correct state.Received: 6 January 2005, Revised: 5 May 2005, JEL Classification Numbers: C72, D82.Jacob K. Goeree: Correspondence toFinancial support from the National Science Foundation NSF (SBR-0098400 and SES-0079301) and the Alfred P. Sloan Foundation is gratefully acknowledged. We thank Richard McKelvey posthumously for insights and conjectures about information aggregation that helped shape our thinking about the problem. We also acknowledge helpful comments from Kim Border, Tilman Börgers, Bogachen Celen, Luis Corchon, Matthew Jackson and seminar participants at University College London, the University of Arizona, Universitat Autonoma de Barcelona, the California Institute of Technology, the 2003 annual meeting of ESA in Pittsburgh, the 2003 Malaga Workshop on Social Choice and Welfare Economics, the 2003 SAET meetings in Rhodos, and the 2003 ESSET meetings in Gerzensee.     

Aggregation of Directional Distance Functions and Industrial Efficiency

Three main objectives are pursued in this paper. First, we intend to analyze the aggregation problem of directional distance functions from a constructive viewpoint. We provide necessary and sufficient conditions concerning the structural properties of the production technology and of the nature of groups of firms. Indeed, exact additive aggregation holds for a linear technology and for a direction solely defined in the output space. Second, since these conditions are somewhat restrictive, we are interested in providing a measure for the aggregation bias through the relationship between industrial and structural technical efficiency. Finally, we show that this aggregation bias is a lower bound for industrial allocative efficiency.     

Classical meets modern in the IDEA protocol for structured expert judgement

Expert judgement is pervasive in all forms of risk analysis, yet the development of tools to deal with such judgements in a repeatable and transparent fashion is relatively recent. This work outlines new findings related to an approach to expert elicitation termed the IDEA protocol. IDEA combines psychologically robust interactions among experts with mathematical aggregation of individual estimates. In particular, this research explores whether communication among experts adversely effects the reliability of group estimates. Using data from estimates of the outcomes of geopolitical events, we find that loss of independence is relatively modest and it is compensated by improvements in group accuracy.     

Performance of Moving Average Trading Rules in a Volatile Stock Market: The Russian Evidence

This article examines the profitability of dual moving average crossover (DMAC) trading strategies in the Russian stock market over the 2003–12 period. It contributes to the existing technical analysis (TA) literature by testing, for the first time, the applicability of ordered weighted moving averages (OWMA) as an alternative calculation basis for determining DMACs. In addition, this article provides the first comprehensive performance comparison of DMAC trading rules in the stock market that is known as one of the most volatile markets in the world. The results show that the best trading strategies of the in-sample period can also outperform their benchmark portfolio during the subsequent out-of-sample period. Moreover, the outperformance of the best DMAC strategies is mostly attributable to their superior performance during bearish periods and, particularly, during stock market crashes.     

Compulsory versus voluntary voting: An experimental study

We report on an experiment comparing compulsory and voluntary voting institutions in a voting game with common preferences. Rational choice theory predicts sharp differences in voter behavior between these two institutions. If voting is compulsory, then voters may find it rational to vote insincerely, i.e., against their private information. If voting is voluntary so that abstention is allowed, then sincere voting in accordance with a voter's private information is always rational while participation may become strategic. We find strong support for these theoretical predictions in our experimental data. Moreover, voters adapt their decisions to the voting institution in place in such a way as to make the group decision accuracy differences between the two voting institutions negligible. The latter finding may serve to rationalize the co-existence of compulsory and voluntary voting institutions in nature.     

Strong Nash equilibrium in games with common and complementary local utilities

A rather general class of strategic games is described where the coalitional improvements are acyclic and hence strong Nash equilibria exist: The players derive their utilities from the use of certain facilities; all players using a facility extract the same amount of local utility therefrom, which amount depends both on the set of users and on their actions, and is decreasing in the set of users; the ultimate utility of each player is the minimum of the local utilities at all relevant facilities. Two important subclasses are “games with structured utilities,” basic properties of which were discovered in 1970s and 1980s, and “bottleneck congestion games,” which attracted researchers’ attention quite recently. The former games are representative in the sense that every game from the whole class is isomorphic to one of them. The necessity of the minimum aggregation for the existence of strong Nash equilibria, actually, just Pareto optimal Nash equilibria, in all games of this type is established.