Nitrate leaching from loamy soils as affected by crop rotation and nitrogen fertilizer application

Nitrate leaching as affected by cropping system/crop rotation, history of farmyard manure application or fertilizer nitrogen application (0 N, 0.5 N and 1 N) was studied at nine sites on loamy soils during 1986/87, 1987/88 and 1988/89. Soil solution from 80 to 90 cm soil depth was sampled every second week in the period November to May by the use of porous ceramic cups and analysed for NO₃-N and Cl. Climatical conditions were obtained from standard meteorological observations in the region. Drainage from soil profiles was calculated from measured and simulated values of precipitation and actual evapotranspiration, respectively.The results show that type of crop is of the utmost importance for the leaching magnitude of nitrate as 40% of the total variance in nitrate concentrations in the soil solution could be explained by the type of crop.The second factor of importance was the history of farmyard manure (FYM) application, which was able to explain 28% of the total variation in nitrate concentration in the soil solution. Nitrate concentration/leaching from arable land without FYM ever being applied was considerably lower than from arable land which received periodical FYM applications until the early 70's or from arable land which besides periodical FYM applications in the past presently still receives regular applications of FYM. Only about 1% of the total variation in nitrate concentration in the soil solution was explainable by the level of fertilizer nitrogen application.Differences between years explained 14% of the total variation in nitrate concentration in the soil solution due to differences between the years in soil temperatures and water run-off. The run-off during the autumn and winter of 1986/87, 1987/88 and 1988/89 was 95, 275 and 55 mm, respectively. As expected nitrate leaching increased with increasing run off. However, nitrate leaching at the 275 mm run off was considerably lower than expected, which seems explainable by a substantial denitrification. The soil at the sites in question seems thus partly to purify the soil solution for nitrate before it leaves the root zone at the observed high run off conditions.     

电涡流式钞票厚度检测传感器设计

在ATM机和纸币清分机中,钞票的厚度检测是必须的功能,通过钞票的厚度特征可以识别钞票上粘贴的胶带和折角等,从而剔除不合格钞票。本文论述了一种电涡流式钞票厚度检测传感器,采用并列的结构相同的多路厚度传感器,通过每路独立的厚度传感器检测出来的信号,拼接成整张钞票的厚度特征,从而识别钞票是否有异常。本传感器具有电路简单、成本低、检测范围大等优点。     

螺线型爆磁压缩发生器工程计算

根据发生器的等效电路模型,建立了单级爆磁压缩发生器运行时的电路方程;建立了接触磁通损失模型并推导了磁通损失等效电阻计算公式。根据电路方程和发生器电阻、电感和磁通损失等效电阻的计算公式编制了一个计算程序,利用该程序对文献介绍的某分段变螺距的圆柱型爆磁压缩发生器进行了计算,结果表明,该计算程序能很好地预测发生器的性能并验证接触磁通损失模型的可行性。     

曲面薄壁零件非接触在线精密测量

设计了利用计算机进行误差补偿强化曲面薄壁零件轮廓面非接触测量的实用方案,介绍了解决问题的思路和原理,并提出采用ＬＣ震荡法的数字式涡流测微传感器,阐述了自动定标原理。     

小湾水电站水库淹没与移民初议

小湾水电站装机容量４２０万ｋＷ，水库总库容１５１．３亿ｍ３，可进行多年调节，是澜沧江中下游河段梯级开发的关键性工程。虽然有巨大的库容，但淹没损失相对来说还是比较小的。可行性阶段统计，水库淹没耕地３７１２ｈｍ２，占涉及县总耕地面积的１．１４％，迁移农业人口３．２３万人，占涉及县总农业人口的１．５８％。水库淹没处理和移民补偿投资只占工程建设静态投资的１０．７％。水库的建设不会对当地农业生产产生大的影响，移民难度不大；水库的投资不会对工程建设起制约作用。由于水库补偿资金的注入，对促进当地经济的发展和移民的生活改善，将起重要的作用。     

电涡流缓速器转子盘风道散热结构参数影响分析

电涡流缓速器(ECR)实施缓速制动时将车辆行驶动能转化为热能,使得转子盘产生较大温升,导致其制动性能不稳定.针对这一现象本文提出在转子盘风道内安装圆柱扰流强化散热装置.为合理选择扰流圆柱结构尺寸,建立不同直径圆柱扰流强制散热结构转子盘单风道物理模型,采用K-ε标准双方程和能量方程分析各模型不同进口气流速度条件下热交换改...     

分解区域方法在涡流检测仿真中的应用

随着现代制造业的发展,涡流检测仿真问题日渐复杂。传统的单一求解区域方法的运用遇到瓶颈,而分解区域方法将复杂的单一区域上的求解转化为较简单的若干个子区域上的求解,克服了传统方法遇到的困难。该文主要介绍分解区域方法在涡流检测仿真中的应用。     

精细表面下细小缺陷的磁光涡流成像实时探测

磁光涡流成像检测装置可实现精细表面下细小缺陷探测。在该装置中，通过物体表面上方的交流激励线圈实现传统的涡流感应，涡流所感应的磁场由法拉第效应来检测。为了实现表面下缺陷的检测目标，激光穿过安放在激励线圈中的特殊的磁光晶体，激光偏振方向在晶体中的旋转大小取决于检测区域磁场的大小，缺陷将使检测区域磁场分量发生变化并使偏振光的旋转角发生相应变化，通过一光学装置转化成“明”或“暗”图像，该光学装置由传统的显微镜、照明系统、偏振器和CCD图像传感器组成。给出了初步的实验探测结果。     

Optimal network restructure via improved whale optimization approach

Latterly, reduction of power loss in distribution system is the objective of many researches due to its impact on total costs and voltage profiles. It can be handled by optimal restructure of radial distribution system (RDS). This article introduces an innovative approach to restructure of RDS by electing the optimal switches combination subject to the system operating constraints, which is improved whale optimization approach (IWOA). The suggested approach combines exploitation of WOA with exploration of differential evolution (DE), and thus, it supplies a promising candidate solution. The suggested approach is tested on IEEE 33 and 69 bus RDS. The superiority of the suggested approach compared with other well‐known approaches is verified through simulation results by observation of total losses, cost, and saving. Also, the impact of alterable loading is investigated to prove the effectiveness of the suggested IWOA.     

涡流技术在检测钢件淬火层厚度中的应用

涡流检测实质上就是通过运用法拉利电磁感应定律来反映金属导电材料表面缺陷和厚度变化。文章主要研究电涡流检测钢件淬火层厚度时表面阻抗的变化,通过阻抗变化来反映淬火层厚度的变化,经过数据处理得到待测钢件的厚度。由于在电涡流测厚传感器设计过程中会受到多种因素的干扰,对测量精度和可靠性有很大的影响,这里也对主要的干扰因素进行了推导和分析,通过对标准涂层试块进行测量和对数据的分析,能够大略的反映出淬火层厚度的变化。