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981.
对SL4105柴油机的连杆进行了精确的三维建模,并考虑到连杆锻造毛坯和加工误差对连杆刚度的影响,根据实际情况对连杆运动时的整体变形进行了计算分析。分析结果表明:连杆的锻造加工误差会使连杆在最大爆发压力下产生较大的弯曲变形,变形最大值的大小和位置因加工误差的不同而不同。 相似文献
982.
983.
Summary Laboratory studies were conducted to evaluate the effects of drying on soil strength and corn emergence (Zea mays L.). Corn was germinated in Billings silty clay under a bank of heat lamps which operated 9, 14, 19, or 24 h per day. Soil strength (modules of rupture), soil moisture content and emergence were measured daily.The relationship of soil strength to corn seedling emergence as influenced by the four light and heat durations and bare and mulched soil surfaces was determined. As soil strength increased emergence decreased until it ceased at soil strengths of about 80 kPa. Strength of this soil had a high negative correlation with soil water content and increased with time. Mulching decreased initial rate of drying, decreased crust strength, and improved corn emergence. The 14-hour light and heat treatment resulted in the highest corn emergence.Contribution from Colorado State Experiment Station, USDA-ARS Snake River Conservation Research Center, and USDA-ARS Fort Collins, respectively 相似文献
984.
The People's Victory Irrigation System which diverts water from the Yellow River of China covers a total irrigable area of 59 000 ha. The system encountered some serious problems in the first decade of its operation — salinity and waterlogging of irrigated land, siltation of irrigation and drainage channels, as well as a low efficiency of water use. This paper describes a series of structural and functional measures which have been adopted in the past 24 years for the rehabilitation of the system, including: improvement of the existing drainage system and construction of new drainage system on agricultural land, conjunctive use of surface and groundwater supplies, a comprehensive programme to reduce the levels of siltation as well as the implementation of improved water management practices. A model for the optimal operation of the system by using system analysis theory as an aid in reducing the operation and maintenance (O & M) costs has been developed in recent years. The results are that the soil salinity has been controlled and the agricultural production has increased whilst the efficiency of water use has improved and the siltation levels reduced. Experience gained on this system has been successfully used in developing and managing other irrigation projects along the lower reaches of the Yellow River. The proposed procedure of solving the said optimal model has also embodied some benefits from reducing O & M costs in operation. 相似文献
985.
在对设施蔬菜生产中使用的水肥一体化设备进行智能灌溉控制设计中,监测混肥罐和回液桶中液位高低是非常必要的。现有液位检测普遍采用机械开关式液位浮子,工程实践中发现当进出水口与浮子过近,或者水纹波动显著时,浮子上下剧烈抖动会导致水泵随浮子的抖动而经常启停,对于启动电流较大的泵容易造成损伤。本文在软硬件设计中采用了计数器数字滤波电路以及单片机定时器中断,设计了一种替代简单液位浮子的实用智能液位开关。为了检验该设计的性能,在同等条件下,进行了不同液面、不同压力和水流量的对比试验。试验结果表明,计数脉冲发生电路中充电电阻和放电电阻为4.7 kΩ时,滤波后的输出信号比现场实际的数控信号时间迟延了2.11 s,经数字电路滤波后的输出信号已经完全消除了宽度小于2 s的所有干扰信号,并且具有很高的稳定性。迟延时间与计数电路、计数脉冲发生电路有关,通过电路设计调整滤波脉宽可使输出信号有效地滤除干扰成分。同时,利用该方法也可以根据不同工况,如不同功率的水泵设定不同参数滤除干扰信号,提高智能液位开关适用性。 相似文献
986.
987.
Water and land resource competition and environmental degradation pose difficult questions for resource managers. In particular, the ensuing trade-offs between economic, environmental, and social factors and their spatiotemporal variability must be considered when implementing management policies. This paper describes an integrated modelling toolbox that has been developed for highland catchments – specifically the Mae Chaem catchment in Northern Thailand. This toolbox contains models of crop growth, erosion and rainfall-runoff, as well as household decision and socioeconomic impact models. The approach described advances and complements previous approaches by: considering more complex interactions between land-use decisions and the hydrological cycle; modelling household decisions based on uncertain expectations; and assessing impacts of changes not only on flows and household income, but also on subsistence production and erosion. An example of the types of trade-offs and scenarios that can be assessed using the integrated modelling toolbox is also presented. This demonstrates that for the scenarios presented, the magnitude and direction of impacts simulated by the model is not dependent on climate. Further testing of the model is demonstrated in a companion paper. Overall, the plausibility of the model is shown. 相似文献
988.
分析了排灌企业加强货币资金内部控制的必要性.提出了排灌企业加强货币资金内部控制的目标和主要方法.第一,建立严格的货币资金管理制度,着重对于现金和银行存款日常收支过程中最有可能出现的漏洞提出防范措施.第二,建立严格的岗位分工制度,强调经办货币资金收付的不相容各岗位分离,形成相互牵制.第三,建立严格的授权、审批制度.第四,建立严格的会计电算化内控制度,明确会计主管、系统管理员、凭证录入人员的职责权限. 相似文献
989.
主要介绍了自行开发的水泵水轮机流动可视化图像的解析原理,并就示踪物的追踪与最佳相关域的确定问题进行了深入的分析,介绍了图像解析的程序设计的思想与功能。试验与计算结果表明本套软件适合于旋转的流体机械的流场图像的解析计算。 相似文献
990.
Jan L. M. H. Gerards 《Irrigation and Drainage Systems》1992,6(3):223-247
The inability to properly maintain irrigation systems over time forced the Government of Indonesia (GOI) to seek cost recovery from water users through introduction of an irrigation service fee. The plan is to introduce this fee in all of the technical irrigation systems of Indonesia, covering about 4 million hectares, over a 12 year period. Design and Introduction of this service fee in 4 pilot areas of the 4 major rice producing provinces (West, Central and East Java, and South Sulawesi) during 1989–1991 has shown that users are willing to pay. Results of first ISF collection from over 11,000 farmers in Central and East Java in pilot systems was an encouraging 95%. However that acceptance to pay by users depends on their structured and systematic involvement in defining systems needs. They need to understand a differentiation in payment if service levels are different. They appreciate use of collected funds in the system where collected. They understand the organization of water users associations but this requires their active role in fee determination and collection. They understand the establishment of federations of these associations. ISF requires also active involvement of Local Government officials as facilitators and intermediaries between service receivers (the water users) and service providers (personnel of the Public Works irrigation department) in the introduction period. This article describes the experience of the first 21 months of the ISF project, the concept developed, the principles used as basis for ISF, the introduction at the field level, issues related to acceptance by users and by the institutions involved, and the first results.Abbreviations/Acronyms DGWRD
Directorate General of Water Resources Development (Ministry of Public Works)
- EOM
Efficient Operation and Maintenance
- Gabungan
group of WUAs
- IPAIR
Indonesian abbreviation for ISF
- ISF
Irrigation Service Fee
- Juru
gate keeper
- PBB
land tax on irrigated lands
- PPL
agricultural field extension agent
- P3A
Indonesian abbreviation for Water Users Associations
- PU
Indonesian abbreviation for Public Works
- SM
Special Maintenance
- WUA
Water Users Associations 相似文献