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日本水稻生产现况及其启示 总被引：1，自引：0，他引：1
日本是发达的工业国家,其农业生产总值仅占国民生产总值的1.5%.但水稻生产在日本仍具有重要的意义,在过去的几十年里,日本政府对水稻生产采取严格的保护与支持政策.在贸易自由化、经济全球化的背景下,日本水稻政策面临着巨大的挑战.为了提高日本稻米的国际竞争力,日本政府开始改革国内水稻支持政策,取消了价格管制,更多地采用了市场化的手段来管理水稻生产.本文讨论了日本水稻生产的现况及其支持政策,并就我国的水稻生产支持政策的制定提出了建议. 相似文献
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In order to improve the error in image reconstruction caused by changeable positions of the electrodes in closed electrical impedance tomography, we propose an open electrical impedance tomography (OEIT) model using fixed electrode array. The problem was approximately assumed to be a virtual field by defining certain local sensitive area instead of solving the boundary problem in the whole electromagnetic field strictly. Modeling and simulation of OEIT have been conducted to define reasonable boundary parameters and electrode array structure. The finite element method is used for forward computation while Newton one step error reconstructor is used for image reconstruction. The target position, area and conductivity change can be reflected by the relative change of the boundary voltage and the reconstructed image is clear. Better resolution and positioning accuracy can be obtained in the shallower surface of the body by OEIT, so it is valuable in clinical applications. 相似文献
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The corrosion and extraction toxicity of heavy metal in ancient smelting slag is analyzed. Leaching behavior of heavy metal in smelting slag is discussed through extraction toxicity test of different pH values. The results show that the pH of smelting slag is alkalescence, the heavy metal content is high and the average content of heavy metal (zinc plus plumbum) is up to 6.97%. However, most of heavy metal in smelting slag is in residual state. Its extraction toxicity is low and potential harm for environment is obviously weakened. It indicates that forecasting heavy metal’s potential harm for environment in smelting slag by totalizing method is not accurate. The leachable quantities of heavy metals significantly increase in extremely acidic and alkaline condition. The leachable quantities of Zn, Pb, Cr and Cd are all up to maximum when pH<3. The leachable quantities of Zn, Pb and Cr all increase when pH>12, but the extracting amount is lower than that in acidic condition. The leachable quantity of Zn, Pb, Cr and Cd is minimal in neutral condition. Under normal rainfall conditions, potential harm for environment of ancient smelting slag is decreased to a lower level. It can be treated according to the requirement for general industrial solid wastes. 相似文献
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This paper introduces phenomenon of electric erosion of gear and the research condition and evolution of it; puts forward a point of view that a system of electric erosion of gear is a especial tribology system which is in relation to many subjects and in which many phenomena exist and coupling each other , moreover , it is very difficult and complex to study electric erosion of gear by experiment ; have made statistical datas about typical example of electric erosion of gear inland ,at this base ,summarizes characters of electric erosion of gear and the study means of it. 相似文献
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This paper studies the problem of computer vision in the vehicle intelligent auxiliary driving system. An effective and real time method in highway to search and track obstacle is presented. Obstacle candidates are tracked and analyzed, false alarms generated by the object detector are recognized and rejected. It also supplies some valuable discussion on problems existing in its experiments. 相似文献
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To make the biomass tablets heated fully in a fluidized pyrolysis liquefaction process, it ought to be ensured that sufficient biomass granules stay long enough in the bed so as to meet or exceed the expected pyrolysis temperature. That is, the prerequisite is that the staying time must be more than or equal to the pyrolysis time. However, the staying time is decided by the flow speed and CFB parameters, and the pyrolysis time is controlled by the heat transfer process of biomass particles in a fluidized bed both of which are closely related to the parameters of biomass particles. This paper analyses the heat transfer process of the biomass in the pyrolysis reaction tower, establishes a simplified model of heat transfer with a gas solid flow, studies the rule of pyrolysis time and staying time changing with the biomass size and finds out a theoretical method of selecting the expected parameters of biomass granule to ensure the full pyrolysis of biomass materials. 相似文献
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A typical clayey loess obtained along the Shenyang Ha’erbin Express Railway was taken as a case study. The effect of non saturated water content, temperature, freezing rate, supplying water condition and freezing thawing circulation on the frost susceptibility of soil were investigated with freezing and thawing experiments. It was shown that in the closed system, the frost heaving ratio of unsaturated soil increased with water content increasing and eventually reached a stable value. And for the soil samples with low water content, the frozen heave rate increased with the decrease of temperature. While for the samples with relatively higher water content, the frozen heave rate decreased with the increase of temperature. As regards the open system, the frost heaving ratio increased with a growing gradient as the freezing rate decreased. Water feeding made the frost heave amount increase significantly, while less with the increase of water content. The frost heave deformation showed exponential decline trend with the increase the frequency of freezing and thawing for soil with low dry density, while exponential increase for the soil with high dry density. 相似文献
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The theory of Artificial Neural Networks and image processing are analyzed. ANN theory is also investigated . A Back Propagation network is used for classification. Based on the ANN and feature extraction, a character recognition and entry system is developed. Its drawbacks are discussed. Some solutions are presented. An odd feature database is constructed to promote the performance for learning. A 3 layer feedforward network has been proved that it has the ability to identify hand written characters. 相似文献
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This paper do some research on the problem of computer vision on autonomous vehicle navigation system on highways. This algorithm first extracts the lane edges by means of wavelet transformation. Then the feature model of the lane markings is built,Which are tracked them in real time. Finally in terms of the parameterized model for the appearance of the lane in the image it fits the lane and get the road direction. This information assures that the whole system can realize lateral control and longitude control. 相似文献