数控铣齿机主轴系统温度场有限元分析

热误差是影响机床加工精度的主要因素之一。主轴的热变形是机床总的热变形的重要组成部分。因此本文在分析数控铣齿机主轴热源的基础上,计算发热量,确定边界条件,并利用有限元软件abaqus建立主轴系统的温度场模型并进行了数字模拟仿真,为主轴系统的进一步热变形控制提供了基础。     

园艺领域专业学位研究生创新能力培养研究——以黑龙江八一农垦大学为例

研究生教育是我国现阶段最高层次的学历教育,培养具有一定创新能力的创新型专业人才,是时代赋予研究生教育者的使命与责任。该文深入分析研究生创新能力培养的重要性,分析国内外研究生创新能力培养的现状,提出提高研究生创新能力的培养方法。     

早稻旱直播栽培技术

从稻田选择及处理、品种选择、播种、田间管理等方面总结了早稻旱直播栽培技术,以供参考。     

Economic valuation of cultivated lands as nitrogen removal/effusion sites by newly proposed replacement cost method

To valuate the multifunctionality economically is effective to make it possible to realize the value for the nation and to compare functionalities among countries of the world. In this paper, the external economies of paddy fields and fallow paddy fields including wetlands as N removal function sites, and of upland fields and orchards as pollution sites are valuated by the newly proposed replacement cost method, by replacing them with construction costs of water quality improvement facilities. In addition, we discuss an agricultural land-use scenario in which cultivated land has no net negative economic effect on the water environment. The results showed that (1) paddy fields and fallow paddy fields including wetlands were respectively valued at 1.2×10³ and 2.81×10³ JPY m⁻² on average as the N removal sites, (2) upland fields had 0.32×10³ JPY m⁻² on average of economic value, and suggested that paddy fields have an external economic value that compensates for the negative external economic value of upland fields 3.65 times their size.     

Nitrous oxide emission measurement with acetylene inhibition method in paddy fields under flood conditions

Nitrous oxide (N₂O) emission from flooded rice paddy fields was continuously measured by the closed chamber method at an experimental plot in Thailand for a whole cultivation period. To characterize the N₂O emission with regard to the denitrification N loss, the C₂H₂ inhibition method was applied. Flood water on the soil greatly suppressed the N₂O emission. The N₂O emission was mitigated considerably by even a thin film of the flood water. The overall average N₂O emissions under flood conditions for one crop season (83 days) at the control site and the C₂H₂ treated site were 10.3 and 11.8 μg N m⁻² h⁻¹, respectively. The N₂O emission from the C₂H₂ treated site was consistently higher than that from the control site and the N₂O emission from both sites followed the same diurnal and seasonal variation pattern, indicating the effect of denitrification inhibition by the supplied C₂H₂. The N₂O emission enhanced along with temperature increase when NO₃–N concentration in the soil water was above 0.4 mg N l⁻¹ and soil temperature was above 24°C, suggesting specific temperature influence over the emission. The increase in NO₃–N concentration and temperature in the soil affected only the N₂O emission while the difference in the emission at the C₂H₂ treated site and the control site was not so much affected. It was suggested that most of the actively produced N₂O under higher NO₃–N concentration and temperature would likely to quickly emit to the atmosphere rather than to undergo further reduction to N₂.     

A combined technique of floodplain storage and reservoir irrigation for paddy rice cultivation

This paper introduces an irrigation system developed in the floodplain of a lake and studies the water management technique of the irrigation system by estimating the total water balance of the whole system. The system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system. Two main models are used for calculating the total water balance. The first model is the water balance of the reservoir. The inputs to the model are water level of the reservoir, precipitation, lake evaporation, infiltration, and area–volume curve of the reservoir. The outputs are inflow and outflow of the reservoir. The supply from the reservoir to paddy fields is computed from the outflow. The second model is the water balance of paddy fields, based on which the water requirement in paddy fields is derived. The reference evapotranspiration needed to calculate the water requirement is simulated for monthly time series using the FAO Penman–Monteith model. Since there is no drainage network in the irrigation system, surface drainage and runoff are not included in the calculation of the water balance, and seepage is considered negligible in the flat floodplain area. The evapotranspiration, rice variety, soil type and irrigated area are used to simulate water consumption in paddy fields. Finally, the two models are connected to produce the total water balance from the reservoir to paddy fields. The total outflow from the reservoir is estimated and the total water consumption for dry season cultivation is also determined. Finally, the efficiency of the whole system is examined.     

播种期对杂交稻种子纯度海南种植鉴定结果的影响

通过比较不同播种时期杂交水稻种子样品在海南种植鉴定的农艺性状表现,发现播始历期、株高、结实率等主要性状均表现出不同程度的变化,且部分组合与其亲本的变化幅度不同,从而影响鉴定的准确性。根据品种特性,确定最佳播种时期,并采用合理的栽培与管理技术,是提高杂交水稻种子纯度种植鉴定结果准确性的关键。     

搞好钵盘育苗抛秧 持续发展水稻生产

在分析了水资源短缺、整地质量难以保证、稻区劳动力充足是影响水稻钵盘育苗抛秧技术面积继续扩大的主要因素的同时提出了充分认识抛秧技术的重要性,采取多种措施、因地因时因势制宜,稳定发展水稻钵盘育苗抛秧的具体措施。     

南方亚麻田杂草防治药效试验及应用技术

南方冬春季种植的亚麻，田间主要杂草有看麦娘、牛繁缕、man草及碎米荠。试验表明：72%郁尔乳油每666.7m^2用量130ml，在亚麻播后发芽前封土处理，其鲜重防效达84.7%；17.5%快刀乳油、10.8%高效盖草能乳油及5%禾草杀星乳油每666.7m^2用量60ml，在亚麻出苗后20～30天喷雾，其鲜重防效分别为98.1%、87.1%和92.7%。上述药剂对亚麻安全无药害，一次用药能完全控制亚麻全生育期的杂草危害。     

豆田蚜虫防治指标的研究

本文通过1988—1990三年研究,测定了大豆花荚期豆田蚜量与大豆产量的关系,并依据这种关系及目前大豆商品生产状况提出了新的豆田蚜虫防治指标。