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81.
82.
北京密云石匣小流域水土保持措施对土壤侵蚀的影响研究 总被引:15,自引:0,他引:15
水土保持措施的实施可有效地控制土壤侵蚀 ,不同的水土保持措施存在不同的水土保持效益值。利用北京密云石匣共 2 0个坡面径流试验小区的野外观测资料 ,分析得出了北京石匣小流域不同水土保持措施下的水土保持效益值 ,其中免耕 (玉米 )为 0 .2 80 ,梯田 (玉米 )为 0 .142 ,人工草地为 0 .0 6 3,荒草地为 0 .0 45 ,水平条林地为0 .0 2 5 ,鱼鳞坑林地为 0 .0 19。人工草地、荒草地、水平条林地和鱼鳞坑林地有显著的水土保持效益 ,但它们之间的水土保持效益并无显著差别。坡耕地 (16 .8°)的年均侵蚀模数为 145 3.8t/ km2 ,远大于土壤自然形成速度和北方石质山区的允许土壤流失量。其研究结果可为土壤侵蚀模型预报、水土保持规划、环境治理和评估提供依据 相似文献
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84.
Two monolayer concrete frames with the same reinforcement, KJ1 and KJ2, were designed. KJ1 was designed to simulate low cyclic reversed loading test under weak earthquake. Besides, the fire response test, including temperature rising and lowing, was made by fixing the axial compression ratio of the column. For KJ2, the fire response test at the fixed axial compression ratio was made. The deformation response of the concrete frames in fire was studied. Comparative analysis of the apparent phenomenon, temperature curves, bearing capacity change of the frames were made based on the test results of KJ1 and KJ2. According to the simplified temperature distribution, the ultimate bearing capacity of the column under the high temperature was preliminarily determined. It is illustrated that the calculation results and finally test phenomenon are consistent according to the simplified section. 相似文献
85.
Abstract:This paper developes a heating coefficient model to study the heating performance of multi-nozzle water-jet steam ejector. It analyzes the factors of heating performance, and explores the relationships between the heating performance and different operating parameters theoretically and experimentally. The results show that the heating performance of multi-nozzle water-jet steam ejector is very good. The heating coefficient decreases with the increase of the inlet water temperature, and increases with the increase of the steam pressure and ejecting coefficient. The relationships between heating performance of ejector and different operating parameters by calculation and experiment are in good agreement. 相似文献
86.
Based on the dependency of the PDTDFB coefficients across the interscale and interdirection and the statistical properties of HMT for the correlation properties, a new HMT in PDTDFB domain was put forward. Compared with the other typical denoising methods, the experimental results demonstrate that the proposed method shows better performance in image denoising, especially in edge maintenance. 相似文献
87.
High temperature mechanical properties are key factors which affect fracture production during deforming process of continuous casting. High temperature properties of weathering steel Q450NQR1 are tested in 3 cooling rates (1.65, 5, 10 ℃/s) using Gleeble thermo-mechanical simulator. Specimens appear austenite dynamic recrystallization at 1 050 ℃, and the ductility reaches the lowest point and the reduction of area approaches 23% at 850 ℃ in 3 cooling rates. As the cooling rate increases, the low ductility area where cracks are easy to be produced in slabs is enlarged and extended towards low temperature, and the ductility troughs are deepened. The increase of the cooling rate decreases the tensile stress and yield stress, while when the cooling rate increases to some degree, it doesn’t affect the stress. The low cooling rate decreases the film or network ferrite producing in austenite grain boundary, and the carbonitride of microalloy is enwrapped in matrix, which is helpful to improve the ductility of steel. 相似文献
88.
Input-output budgets for nitrogen in a typical purple soil sloping ploughland in Three Gorges areas 总被引:2,自引:0,他引:2
The Xinzheng watershed in Zhongxian county, Chongqing, is a typical purple soil sloping ploughland in the Three Gorges areas. In 2009, the input-output budgets in this watershed is investigated and the results indicate that the nitrogen input is 918.26 kg/(hm2·a) and the output are 569.46 kg/(hm2·a). Furthermore, chemical fertilizer nitrogen is the main input source, accounting for 57.63%, and the main output track is nitrogen in crops, accounting for 36.22%. In this small watershed, the nitrogen loss load is 258.77 kg/(hm2·a). And the primary lost nitrogen is gaseous species, which is approximately 65.11% of the total lost nitrogen. In addition, nutrient nitrogen balance index is 3.4 in this watershed and the nitrogen surplus load is 348.80 kg/(hm2·a), much higher than the risk value, indicating potential occurrence pollution in ploughland. 相似文献
89.
As important tool for engine semi-automatic isolation system, the magneto-rheological fluids (MRC) can’t achieve tunable stiffness but damping. Therefore, the MRC’s initial stiffness affects the performance of isolation system. To obtain the better isolation effect of MRC in wide frequency, it is necessary to optimize the initial stiffness. As motor unbalanced force and isolation damping are not considered in traditional mount optimization, the feature of semi-automatic control can not be reflected. For a four-cylinder four-cycle in-line diesel engine, a new method which is suitable for stiffness optimization on vehicle engine isolation is presented by using Genetic Algorithm. The optimal isolation system has small absolute force transmissibility in abroad frequency range and small vibration intensity with impact load by using the new method. 相似文献
90.
基因型及外源因子对小麦花药培养一步成苗的影响 总被引:7,自引:0,他引:7
研究了不同基因型及几种外源因子在小麦花药培养一步成苗中的效应。结果表明 ,花药培养一步成苗的愈伤组织诱导率、绿苗分化率、白苗分化率及绿苗产量存在基因型间的差异。高蔗糖浓度有利于获得高频率的花药愈伤组织 ,但同时又提高了花药培养中白化苗频率。动力精 (KT)对花药愈伤组织诱导率影响的差异不大 ,但对绿苗分化率、绿苗产量及绿苗 /白苗 (G/ W)均有显著影响。在试验浓度范围内 ,随 KT浓度的增大 ,绿苗产量提高 ,绿苗分化率明显增加 ,而白苗分化率下降 ,因而 G/ W值明显增大。说明 KT主要是通过提高绿苗分化率和降低白苗分化率 ,增大 G/ W而提高花培一步成苗效率的。在与 KT的配合使用中 ,2 ,4 - D比 NAA更有利于提高小麦花药培养中的愈伤组织诱导率和苗分化频率 相似文献