一步法RT-PCR快速检测鸡新城疫病毒强毒株

本文参照NDV融合蛋白(F)基因序列设计引物,通过一步法RT-PCR扩增到NDV强毒株的170bp大小的特异条带。试验中未检出NDV弱毒株、IBV、AIV、IBDV的RNA,能够检出NDV尿囊液毒的最低滴度为10-5稀释度(相当于103.7EID50病毒量)。对山东省不同地区于1997至2003年所分离的21个NDV强毒株检测全为阳性,而6个NDV弱毒株全为阴性。整个实验操作从病毒核酸提取到判定结果,在5h内即可完成。实验结果表明,该方法特异、敏感,适用于强毒感染鸡群的快速检测     

Depletion of Soil Potassium under Exhaustive Cropping in Inceptisol and Alfisol

Pot-culture studies of intensive cropping without potassium (K) application, taking three successive crops of rice on Sonakhali (Inceptisol) and Ranibundh (Alfisol) soils, revealed that all the forms of soil K declined after the third crop compared to the corresponding initial soil status. A similar trend was also found for nonexchangeable K extracted sequentially and termed as Step K and CR-K (constant rate K). The CR-K contents showed little variations with cropping. Except for the potential buffering capacity of the soil for K at equilibrium (PBC^K ₀) values, all the quantity/intensity (Q/I) parameters, namely activity ratio of potassium (AR^K _e), labile K (–ΔK₀), specifically held K (K_X), and total labile pool of K (K_L) values, decreased in both the soils as they were subjected to repeated cropping. The PBC^K ₀ values changed to a smaller extent in both the soils. In both soils, the threshold levels for release of intermediate K in terms of activity ratio, exchangeable K, and K concentration in soil solution decreased after the third cropping as compared to the initial status. The dry-matter weight of rice, K concentration, and K uptake decreased with the cropping sequence. The difference in values of each parameter between initial status and the third crop was much wider in Inceptisol than in Alfisol.     

步进电机软件锁相方法的研究

本文针对步进电机硬件锁相电流大的问题,提出了用软件对步进电机锁相的方法。文中着重分析了软件锁相方法的合理性和可行性;并阐明了软件锁相使步进电机精确定位的可靠性。软件锁相法在微机改造车床的过程中得到了验证,并显示了它的优越性。     

基于仿真的半挂汽车列车转向盘转角阶跃输入下的稳定性分析

基于任意载荷分布的非线性轮胎模型,应用汽车列车动力学仿真软件ARCSIM,分析了半挂汽车列车在转向盘转角阶跃输入时的转向特性。通过在不同车速、不同结构参数等条件下的仿真计算,揭示了半挂汽车列车的转向特性与车速、结构参数之间的内在联系,给出了半挂汽车列车转向特性在这些条件下的表现特征,为半挂汽车列车操纵稳定性分析提供了参考和借鉴。     

农机液压系统故障诊断思路的探讨

在分析液压系统的故障特点基础上,探讨了农机液压系统故障诊断的原则和步骤,并以油缸故障诊断为例说明了诊断过程。     

退耕还林草背景下宁夏气候生产潜力变化研究

对宁夏退耕还林、还草重点区域进行研究,采用＂逐步订正法＂计算该地区近50年的气候生产潜力和光温生产潜力。结果表明：宁夏灌区、中部干旱带、南部山区玉米的光温生产潜力呈线性增加趋势,但考虑光、温、水3因素的气候生产潜力,因降水稀少而数值很低,无灌溉便无农业;中部干旱带冬小麦的光温生产潜力、气候生产潜力无明显趋势,但气候生产潜力变幅很大,南部山区冬小麦光温生产潜力无明显变化趋势,气候生产潜力呈弱的下降趋势,说明冬小麦生产受到水分的极大制约。利用RegCM3-WOFOST/LINGRA耦合模式模拟的气象要素数据计算了未来宁夏中、南部冬小麦气候生产潜力,均呈弱的增长趋势,说明退耕还林后宁夏气候有利于冬小麦产量的提高。     

Abandonment of soil and water conservation structures in Mediterranean ecosystems: A case study from south east Spain

Traditional rainfed agriculture in semi-arid regions heavily relies on soil and water conservation (SWC) structures to supplement the sparse rainfall. As referring to the ecosystem functions of these constructions, when extensive such systems prevent any runoff into the fluvial system. The extent to which these dams and terraces resist major events is variable, and earthen dams can be major sediment sources. Extensification and increasing mechanization of rainfed agriculture in marginal areas have led to a change in cropping systems. Large-scale almond and olive plantations with widely spaced trees do not rely on runoff water, but draw the soil water from a large soil volume of bare soil maintained by regular shallow tillage. The high density of terraces has now become a nuisance to the farmers. The aim of this paper is to i) demonstrate the degradation of SWC structures and the relative importance of the driving forces, ii) assess the limits of the protection that earthen dams can provide by surveying their resistance during a heavy storm (return period 8.2 years) and iii) demonstrate the implications of the abandonment of SWC structures over the period 1956–2005 for the hydrological connectivity between croplands and the ephemeral rivers system. The headwaters of a marl catchment with a continuous area treated with SWC structures in Murcia region (Spain) already had a very high density of step terraces and check dams (182 m ha^− 1) in 1956. This density decreased by 27% in the period 1956–2005. Furthermore, many terraces have not been maintained and flow traces indicate that they no longer retain water. This is particularly true for the check dams in abandoned lands. The distance between the step terraces has increased over time, making them vulnerable to erosion. The mean drainage area of the dams that failed during the heavy storm was significantly (3.16 ha) higher than that of the ones that remained intact (1.11 ha). The probability of failure increases with drainage area from P = 0.16 for an area of 1.8 ha to P = 0.8 for an area of 20 ha. The percentage of cropland draining directly on the river system without interference of a check dam has increased from just 9% in 1956 to 31% in 2005 and 40% after the storm in November 2006.     

Modelling tillage translocation using step, linear-plateau and exponential functions

The distance over which soil is displaced and mixed during tillage has important implications for the understanding the dynamics of soil variability within complex soil-landscapes. In two preceding studies of tillage translocation, tillage was observed to displace soil over a length of approximately 1 m following single passes of four tillage implements (chisel plough, mouldboard plough, tandem disc and field cultivator), and over a length of approximately 2 m per sequence of conventional tillage (one pass of mouldboard plough, two passes of tandem disc and one pass of field cultivator). Using data from these studies step, linear-plateau and exponential functions were assessed for their ability to estimate the magnitude of translocation and the redistribution pattern of soil within the till-layer, and to predict the redistribution pattern of soil within the till-layer. On average, step, linear-plateau and exponential models estimated 100.0%, 100.2% and 102.5% of the magnitude of translocation and 76%, 88% and 93% of the soil redistribution pattern, respectively. Based on these results, it was concluded that linear-plateau and exponential functions are suitable models of tillage translocation. The exponential model was superior to the step and linear-plateau models, and an improvement over the existing diffusion model.     

阶梯螺旋孔口式孔板消能降压装置性

提出一种管道孔板消能装置,利用孔板扭转形成阶梯螺旋孔口使水流强制扭转,因水流在短距离内瞬间作较大角度的扭转而形成强度较大的螺旋流,其消能降压比率较高,并可在较大范围内进行调节,是一种农业节水灌溉管道系统消能降压装置,可用于农业节水灌溉供水系统和其他类似需要消能降压的管道系统.     

南水北调梯级泵站技术管理研究

分析了江苏省江水北调泵站技术管理现状，根据准市场化运作要求，对南永北调东线工程大型梯级泵站的技术管理体制、运行管理、日常管理和维护检修管理等进行研究。对提高工程管理的合理性，提高工程调水可靠性与经济性，促进工程良性循环与发展有较大意义。