电子商务买方信用评价实证分析

随着网络经济的发展,买方的信用评价以及进一步分析对交易中的卖方越来越重要。人工鱼群算法将人工智能与全局优化思想有机结合,具有全局性、并行性、快速性等优点。结合实例,针对电子商务的特点,对算法进行改进,并调整部分因子将其有效应用于买方信用评价分析中。     

基于人工鱼群算法的水资源可持续供给能力评价方法探讨

人工鱼群算法是一种具有自适应能力和并行性较强、对初始值和目标函数性质及参数选择要求不高、可实现全局寻优等优点的随机搜索优化方法,适宜应用于方案优化、综合评价等问题的研究。本文应用人工鱼群算法,建立水资源可持续供给能力评价模型,运用MATLAB软件编程实现算法,并应用该模型进行了扬州市水资源可持续供给能力评价。案例研究结果表明,基于人工鱼群算法的评价模型优化程度较高,适宜于水资源可持续供给能力评价。     

Meat and fish consumption patterns in Saudi Arabia

This study analyses the demand for meat (beef, chicken and lamb) and fish in Saudi Arabia in a system-wide framework using data for the period 1985–2010. A preliminary data analysis reveals that, in Saudi Arabia, the relative consumption of beef, chicken and fish has a positive growth, while lamb has a negative growth. The average relative price growth rates of beef, chicken and fish are negative, while that of lamb is positive. The expenditure shares of beef, chicken and fish have increased while that of lamb has fallen. The estimation results of the demand system reveal that there is an autonomous trend out of lamb into beef, chicken and fish. The implied income elasticities indicate that beef, lamb and fish are considered to be luxuries, while chicken is a necessity. The demand for all meat products and fish are price inelastic. These elasticities are key inputs for policy analysts in terms of devising policies in relation to meat production, meat imports, taxation and food security issues in Saudi Arabia. The usefulness of the implied elasticities is demonstrated by simulating the consumption of beef, chicken, lamb and fish under various policy scenarios.     

陕西大宗淡水鱼类养殖现状及发展对策

本文对陕西大宗淡水鱼类养殖的主要品种、产量、养殖面积、区域分布、养殖条件、环境质量状况、大宗鱼类质量安全状况进行了综述,对产业发展中存在的主要问题进行了分析,并针对存在的问题提出陕西大宗淡水鱼类发展过程中应加大优良品种的引进和推广力度,调整品种结构;开展旧池塘改造和盐碱地渔业综合开发,探索高效、高产生态养殖模式,探索产业化经营方式以增加产业附加值;加强渔业生态环境污染治理,进一步推进资源、环境和生产要素的优化配置,实现产业发展与环境保护的协调发展。     

水源生态涵养区的鱼文化产业双螺旋发展模式一一以北京市密云县为例

水源生态涵养区发展亟需模式创新来协调生态保护与经济发展之间的矛盾。论文立足于生态涵养区的发展现状和功能定位,提出文化公益链和产业盈利链耦合的鱼文化产业双螺旋发展模式,并从资源盘活、业态融合、效益共赢等方面对该模式进行分析阐释。文章以北京市密云县为案例表明,该模式可以获得生态、经济、社会文化的综合效益,是水源生态涵养区的一种有效发展模式。     

鱼类外来物种入侵的法律管制分析

近年来,外来物种人侵给我国带来了巨大的经济损失,引起了国内学界及相关部门的重视。鱼类外来物种入侵给我国的渔业经济同样造成了巨大的经济损失。目前,却缺乏相应的法律管制。本文从我国当前的鱼类外来物种入侵现状着手,分析我国当前的外来物种人侵法律管制体系及存在的立法理念落后、法律规定缺位、管理机构混乱等问题;在此基础上,对鱼类外来物种入侵的法律管制提出了一些建议,希望能对加强鱼类外来物种入侵管理做出贡献,以促进渔业经济的健康发展。     

Socioeconomic aspects of rice‐fish farming in Bangladesh: opportunities,challenges and production efficiency*

In spite of the potential for rice‐fish farming in Bangladesh, it has been adopted by relatively few farmers because of socioeconomic, environmental, technological and institutional constraints. Rice monoculture remains the main farming system in Bangladesh even though integrated rice‐fish farming is the best farming system in terms of resource utilisation, diversity, productivity, production efficiency and food supply. Only a small number of farmers involve in integrated rice‐fish farming. This study concludes that rice‐fish farming is as production efficient as rice monoculture and that integrated performs better in terms of cost and technical efficiency compared with alternate rice‐fish farming. Integrated rice‐fish farming can help Bangladesh keep pace with the current demand for food through rice and fish production. However, a lack of technical knowledge of farmers, high production costs and risks associated with flood and drought are inhibiting more widespread adoption of the practice.     

A cost-benefit analysis of a public labelling scheme of fish quality

The purpose of this paper is to introduce a new method capable of evaluating the economic welfare for quality graded fish products using the hedonic price method for plaice in Denmark. Today, no labelling scheme exists for the final consumers of different qualities of fish. A scheme only exists at the first hand market. On this basis, a general applicable, theoretical and empirical method is developed to compare the costs and benefits of the hypothetical choice between the total absence of labelling and the presence of a public labelling scheme, which fully informs consumers on the quality and simultaneously allows the producers to differentiate prices between quality grades. It is shown that the economic welfare associated with a public labelling scheme is at minimum €263,000. Sensitivity analysis shows that this result is robust. The policy implication is that a public labelling scheme should not be implemented as the demand and cost functions have low elasticities, implying that the welfare gain is low.     

Change and diversity in smallholder rice–fish systems: Recent evidence and policy lessons from Bangladesh

Efforts to unlock the genetic potential of both rice and fish, when combined with improvements in the management of rice–fish systems, can potentially increase agricultural productivity and food security in some of the poorest and most populous countries in Asia. In Bangladesh, estimates suggest that the country’s potential rice–fish production system encompasses 2–3 million hectares of land. But despite three decades of research on biophysical and technical aspects of rice–fish systems, this potential has not been fully realized due to insufficient attention given to the social, economic, and policy dimensions of rice–fish system improvement. This paper provides a characterization of the diverse and changing nature of rice–fish systems in Bangladesh to shed new light on the economic viability of different rice–fish systems and recommend policy and investment options to accelerate the development of appropriate rice–fish technologies. Data are drawn from a novel subdistrict-level survey of fishery officers, a household/enterprise survey, focus group discussions, and a meta-review of the literature on aquaculture in the country, all of which were conducted in 2010–2011. Findings indicate that concurrent rice–fish systems, alternating rice–fish systems, and collectively managed systems offer considerable potential for increasing productivity and farm incomes in Bangladesh. Findings also suggest that while innovation in these rice–fish systems is being driven by households and communities, there is need for more supportive government policies and investments to enable further innovation. Policymakers need to develop effective regulations to promote feed and fish quality and quantity, for example. More rigorous analysis of the intended and unintended impacts of these policies and investments is also necessary.