Grain marketing and National Competition Policy: Reform or Reaction?

Grain marketing arrangements in Australia have been controversial for many years. Following an account of the historical background to grain marketing, this article concentrates on more recent debates. The most interesting technical economic argument concerns the validity of claims that statutory marketing authorities with export monopoly powers can obtain higher prices. The article also discusses how marketing in Australia has been affected by Commonwealth and State Government policies with respect to microeconomic reform and privatization. Although major changes appear to have been made in grain marketing and its institutions, there are inherent economic problems with the current approach to deregulation.     

Did the Federal Crop Insurance Reform Act Alter Farm Enterprise Diversification?

We estimate how much United States farms changed enterprise diversification in response to a marked increase in crop insurance coverage brought about by the 1994 Federal Crop Insurance Reform Act, which substantially increased insurance subsidies. The analysis exploits farm‐level panel census data to compare farm‐specific changes in enterprise diversification over time. By examining diversification decisions of the same farms over time, we control for time‐invariant unobserved individual heterogeneity. We then use pooled cross‐sectional data from the United States Department of Agriculture (USDA) Agricultural Resource Management Survey to estimate the relationship between farm diversification and average returns. We find that the insurance subsidies caused a modest increase in enterprise specialisation and production efficiency. Estimated efficiency gains are far less than the subsidies.     

What is the Appropriate Counterfactual When Estimating Effects of Multilateral Trade Policy Reform?

Multilateral trade reforms, such as may eventually emerge from the WTO's Doha Development Agenda (DDA), tend to be phased in over a decade or so after agreement is reached. Given the DDA's slow progress, that implementation may not be completed before the end of the next decade. Ex‐ante analysis of the DDA's possible effects thus requires first modelling the world economy to 2030 and, in that process, projecting what trade‐related policies might be by then without a DDA. Typically, modellers assume the counterfactual policy regime to be a ‘business‐as‐usual’ projection assuming the status quo. Yet we know developing country governments tend to switch from taxing to assisting farmers in the course of economic development. This paper shows the difference made by including political economy‐determined agricultural protection growth endogenously in the baseline projection. We reveal that difference by projecting the world economy to 2030 using the Global Trade Analysis Project (GTAP) model with those two alternative policy regimes and then simulating a move to global free trade (the maximum benefit from a multilateral trade reform) in each of those two cases. The welfare effects of removing the counterfactual price distortions in 2030 are shown to be much larger in the case where agricultural protection grows endogenously than in the case assuming no policy changes over the projection period. This suggests the traditional way of estimating effects of a multilateral agricultural trade agreement may considerably understate the potential welfare gains.     

不同利用方式下草地CH4、CO2及N2O通量研究

[目的]在全球气候变化背景下,研究天然草地和人工草地的温室气体通量以及与部分环境因子的相关关系,进而明确不同草地对温室气体通量的影响情况,为当地相关部门合理开发利用草地提供理论依据,推进草业绿色发展、高质量发展。[方法]文章以内蒙古自治区的阿鲁科尔沁旗选取退化的天然牧草地、混播型放牧人工草地以及刈割型人工牧草地为研究对象,利用目前较为普遍的箱法进行了野外实验,对比分析不同草地利用类型的主要温室气体CO₂、CH₄和N₂O的通量变化情况,并进一步探讨了温室气体与土壤含水量、箱内温度、地表温度以及其他土壤养分指标的相关性。[结果](1)不同利用方式下草地的CO₂通量在整个生长季均表现为排放,其中刈割人工草地的CO₂排放量为67.00±9.15 mg/(m²·h),显著高于放牧人工草地35.50±5.37 mg/(m²·h)和天然草地30.17±4.57 mg/(m²·h)(P<0.05),且CO₂     

H2O/CO2污染对煤油燃料超声速燃烧影响数值研究

在纯净空气与H₂O/ CO₂污染空气来流对比试验结果基础上,采用数值计算方法和化学动力学方法,研究了H₂O和CO₂污染组分对煤油燃料超声速燃烧的影响,获得了试验手段难以得到的燃烧室流场参数和性能数据。完成了相应的煤油燃料超声速燃烧室二维数值计算,其中匹配了进口总温、总压、马赫数、氧气摩尔分数和工作当量油气比。将数值计算结果与相应试验测量值进行了对比分析,并结合燃烧室流场数据、性能参数分析了H₂O和CO₂污染的动力学影响、以及对燃烧室性能的影响。研究表明:(1)数值计算结果与实验测量值总体上吻合,两种手段均体现了纯净空气来流时不同煤油当量油气比的燃烧室性能,并反映了一致的“污染效应”影响趋势;(2) H₂O污染、H₂O+ CO₂污染的存在降低了煤油燃料超声速燃烧室性能,体现在燃烧诱导压升、燃烧效率、流向冲量增量的下降,而且随着污染组分含量的增加,燃烧室性能下降越加显著。      

Fe2O3@浮石催化臭氧降解水中有机物的实验研究

以天然浮石载体，氯化铁为活性组分金属源，采用等体积浸渍法制备了Fe₂O₃@浮石催化剂。对比研究Fe₂O₃@浮石和浮石催化臭氧分解水中微量对氯硝基苯。实验结果表明，与单独臭氧氧化相比，Fe₂O₃@浮石和浮石催化臭氧化工艺可以明显提高水中对氯硝基苯的去除率，分别为92.5%和71.2%。焙烧温度对Fe₂O₃@浮石活性影响最为显著，350℃为最佳焙烧温度。另外，通过叔丁醇抑制实验可以说明催化臭氧化过程遵循羟基自由基机理。