绿色GDP与环境成本核算研究

从环境成本与绿色G D P的关系入手,总结了环境成本核算的一些基础理论和方法,最后提出了绿色G D P核算存在的主要问题以及推行绿色G D P核算的五大对策。     

Evolutionary analysis of herbivorous insects in natural and agricultural environments

Herbivorous insects offer a remarkable example of the biological diversity that formed the foundation for Darwin's theory of evolution by natural selection. The ability of insects to evolve resistance rapidly to insecticides and host‐plant resistance present a continual challenge for pest management. This paper considers the manner in which genetic constraints, host‐plant availability and trade‐offs affect the evolution of herbivorous insects in natural and agricultural environments, and the extent to which lessons learned from studying natural systems may be applied to improve insect resistance management in agricultural systems. Studies on the genetic architecture of adaptation by herbivores to host plants and to insecticides are reviewed. The genetic basis of resistance is an important component of simulation models that predict the evolution of resistance. These models often assume monogenic resistance, but available data suggest that this assumption may be overly narrow and that modeling of resistance as oligogenic or polygenic may be more appropriate. As omics (e.g. genomics and proteomics) technologies become more accessible, a better understanding of the genetic basis of resistance will be possible. Trade‐offs often accompany adaptations by herbivores. Trade‐offs arise when the benefit of a trait, such as the ability to feed on a novel host plant or to survive in the presence of an insecticide, is counterbalanced by fitness costs that decrease fitness in the absence of the selective agent. For resistance to insecticides, and resistance to insecticidal transgenic crops in particular, fitness costs may act as an evolutionary constraint and delay or prevent the evolution of resistance. An important observation is that certain ecological factors such as host plants and entomopathogens can magnify fitness costs, which is termed ecological negative cross‐resistance. The application of omics technologies may allow for more efficient identification of factors that will impose ecological negative cross‐resistance, thereby bolstering insect resistance management. Copyright © 2009 Society of Chemical Industry     

从双黄连口服液分析中兽药提取制剂的应用前景

和中兽药非提取制剂（主要是散剂）相比,虽然中兽药提取制剂具有明显优点,但片面于讲究现代化制剂工艺和指标性质量标准,导致生产成本增高,失去了经济动物应用价值。针对经济动物临床应用特点,中兽药提取制剂应遵循中兽医药客观特点及发展规律,既要满足药剂学要求,又要保持中兽医药特色,即要充分利用现代先进制剂技术,还有保持制剂成本符合经济规律。     

Effects of Weed-Free Periods on Organic Romaine Lettuce Production

Weed management in Romaine lettuce (Lactuca sativa L. var. longifolia) is an economic challenge for organic farmers. This study evaluated the effect of weed-free durations on crop yield and quality, weed densities and biomass, and weeding time in two growing seasons. Treatments included weedy entire-season; weed-free for 7 days after transplanting (DAT), 14 DAT, 21 DAT, 28 DAT, 35 DAT, 42 DAT; and weed-free entire season (49 DAT). Weeds were removed by hand-hoes and the time taken to weed each plot was recorded. Weed densities were recorded prior to each weeding and weed biomass was recorded at crop harvest. Total and marketable lettuce heads were recorded and crop quality was estimated. Weed interference up to 21 DAT resulted in approximately 45% total and 58% marketable yield loss. Weed control beyond this period did not result in significant (p < 0.05) increases in crop yield and quality. However, weed densities at the end of the season were 4- to 15-fold and weed biomass approximately 18-fold greater in plots kept weed-free only for 21 DAT compared with plots kept weed-free season-long. This suggested that weed seed-return may be a concern if late-season weeding is not conducted. To minimize weed seed-return, the plots would have to be kept weed-free for about 35 DAT. However, labor costs must be taken into consideration because the time required to hand-hoe was approximately 87 hr ha^?1 person^?1 greater in plots kept weed-free for 35 DAT compared with plots kept weed-free for 21 DAT.     

我国荔枝示范园生产投入及经济效益分析

基于2014—2015年6省调研数据,分别从成本结构、产出结构、成本收益、生产效率等方面分析荔枝示范园生产投入及经济效益。结果表明,荔枝示范园资本、劳动力、土地等要素价格在不断提升,荔枝生产成本逐年增长。可变物质投入中,农家肥投入增长最快,化肥投入则在下降。2014—2015年荔枝示范园收益率有下降的趋势,生产系统对资源和要素投入的转化率与产出率有待提高。在此基础上,提出了相关建议。     

从社会经济角度分析气刺微割的可行性

气刺微割技术是近十几年来兴起的一种全新采胶技术。从社会经济发展、气刺微割在提高采胶劳动生产率上的优势、气刺微割需增加的费用三个方面,分析气刺微割技术在经济上的可行性。     

Prediction of Repair and Maintenance Costs of Two-wheel Drive Tractors in Iran

Predicting of repair and maintenance （R＆M） costs of tractors in any mechanized farm is necessary for owners and managers to obtain information on overall costs and to control financial balance and production economy. In this context a study was conducted to predict accumulated R＆M costs （Y） of two-wheel drive （2WD） tractors based on accumulated usage hours （X） in Misagh-e-Sabz Agribusiness Company in Iran. Recorded data of the company were used to determine regression models for predicting accumulated R＆M costs （as percentage of initial purchase price） based on accumulated usage hours. The statistical results of the study indicated that in order to predict accumulated R＆M costs of 2WD tractors with accumulated usage hours of 2260 h or less the power regression model Y=0.013 （X/100）1.677 with R2=0.976, and to predict accumulated R＆M costs of 2WD tractors with accumulated usage hours of 2260 h or more the polynomial regression model Y=0.004 （X/100）2-0.181 （X/1 00）＋4.373 with R2=0.998 can be strongly suggested.     

农民专业合作组织——推动农业可持续发展的制度安排

30a的改革开放,土地集体所有的家庭联产承包责任制推动农业增长的潜力有限,小农经营模式导致增收困难,石油农业导致生态污染严重,发展生态农业势在必行;从公平的角度来讲,当前的土地制度不可抛弃,如何降低个体农户所面临的这种风险,是我国农业可持续发展的关键;笔者认为农民专业合作组织是破解我国农业可持续发展进程中这两大难题的一项重要制度安排。     

基于单向哈希链的Ad Hoc网络密钥协商协议

基于B -S定价模型的基础,利用Ito公式及保值策略,研究了股票价格服从CEV模型和B&P过程且存在交易费用的亚式期权的定价模型.得出了该类期权价格所满足的微分方程,并对模型做了数值分析.结论拓宽了亚式期权的研究范围,更适用于实际金融市场.