Water table behaviour in drained lands: effect of evapotranspiration from the water table

Subsurface drain spacing is underestimated by the equations that do not account for evaporation-evapotranspiration (ET) lowering the water table in drained lands. An analytical solution is proposed to evaluate water table behaviour in subsurface drained lands in the presence of ET. A piecewise linear model is proposed and used to describe any realistic functional relation between ET and depth to water table. Characteristics of the solution have been highlighted with the help of numerical examples for which drainage parameters have been chosen from two actually operating drainage systems installed in semi-arid regions. The accuracy of the proposed solution has been verified with the existing numerical scheme as well as by comparing the water table behaviour with the observed field data. Application of the solution in subsurface drainage design has been illustrated which suggests that drain spacing at this particular site could be increased by 9 to 18% if the contribution of ET in lowering the water table is taken into account.     

新型滚刀式棉秸秆粉碎回收机的研制

根据目前棉秸秆粉碎机功耗高、粉尘较大及棉秸秆回收能力差等缺点,设计了一种新型滚刀式棉秸秆粉碎回收机。同时,重点介绍了滚刀式棉秸秆粉碎回收机主要结构和工作原理,对其关键部件切碎装置以及输送装置进行了设计计算,确定了主要的参数。该机结构紧凑,功耗低,可以一次性的完成棉秸秆的粉碎及回收作业,为充分利用开发棉秸秆资源提供了一种新的机型。     

我国油茶果采摘装备研究进展与趋势

近年来,我国油茶产业发展迅速,但采摘环节仍相对滞后,油茶果机械化采摘装备的研究对油茶产业大力发展有着显著地推进作用.重点研究目前国内已研制的油茶果机械化采摘装置和采摘机,系统地比较各自在采摘过程中的机理机制和性能参数等,可以看出当前研究技术不够成熟,采摘装备机械化程度普遍较低.分析油茶果机械化采摘时的科学问题和关键技术...     

Planning and management modeling for treated wastewater usage

Due to urban growth, some agricultural lands have been replaced by residential, municipal, and industrial areas. In some cases the remaining agricultural land will not have enough water because of transfers from agriculture to M&I (municipal and industrial) users. Therefore, in many places, especially in arid and semi-arid regions, the use of treated wastewater as a reliable source of irrigation water has already been, or will be, considered in the future. Due to its unique characteristics, this new resource has many challenges that cannot be ignored, such as health issues, water quality, and long- and short-term effects on soils and crops. The study described herein considered the development of a new GIS-based model for planning and managing the reuse of treated wastewater for the irrigation of agricultural and green lands, considering various factors such as population and urban growth. The model is composed of several different modules, including an urban growth model. These modules are designed to help in the decision-making process for allocations of water resources to agricultural areas, considering factors such as crop types, crop pattern, water salinity, soil characteristics, pumping and conveyance costs, and also by comparing different management scenarios. Appropriate crops that can be grown with a specific water salinity and soil characteristics, proper water resources for each farm (according to pumping and conveyance costs, and analysis of water demand, and water supply) can be determined through the application of this model. The model can also rank agricultural areas and open spaces in and near an urban area according to their suitability for irrigated agriculture.     

四次带参广义Bézier曲面构造与光滑拼接技术

基于一组带参数的四次广义Bernstein基函数,构造了一种带多形状参数λ、γi的四次广义Bézier曲面,该曲面不仅保留了传统Bézier曲面的性质,而且具有优良的形状可调性,同时还以四次Bézier曲面为其特殊情形;其次,详细分析了该曲面的一些基本性质,以及讨论了该曲面的一些特殊退化曲面的构造;最后,为了解决造型设计中复杂曲面难以用单一曲面表示的问题,进一步研究了该曲面的拼接技术,推导了两相邻四次带参广义Bézier曲面片间G1和G2光滑拼接的几何条件,并给出了具体的拼接步骤与几何造型实例。实例结果表明,所提方法不仅简单有效且易实现,可应用于工程复杂曲面的构造与外形设计中。     

滴灌三角形迷宫滴头水力性能稳健性分析

由于滴灌滴头流道曲折复杂,各种结构参数都不同程度地影响着滴头水力性能,滴头水力性能分析时,很难建立显式的解析模型.为此提出基于移动最小二乘响应曲面法建立滴头水力性能可靠性指标对应结构影响参数的灵敏度分析模型.结果表明,滴头流道流量系数的可靠度对流道长度和流道宽度的均值灵敏性较强,对流道转角的均值灵敏性较差;滴头流道流态指数的可靠度对流道宽度和流道转角的均值灵敏性较强,对流道长度的均值灵敏性较差;基本变量标准差的增加会降低滴头流道流量系数和流态指数的可靠度.基于移动最小二乘响应曲面滴头水力性能可靠性灵敏度分析结果与通常的定性分析结果一致,验证了本方法的有效性.     

基于改进RHT及均值漂移聚类方法的双孢菇图像目标提取研究

工厂化生产环境下双孢菇图像存在成簇粘连、菌柄倾斜、白色菌丝繁盛等复杂状态，采用常规阈值分割方法无法准确提取目标，采用改进的随机霍夫变换圆形检测算法与滑动平均聚类算法结合的方法开展目标提取研究。通过图像预处理降低部分背景干扰，改进边缘点取样方式提升圆形检测效率，依据菌盖半径范围剔除无效参数；以双孢菇图像检测出的所有圆形为目标，采用均值漂移聚类算法合并圆形，消除圆形检测算法中识别出的错误目标。采用算法提取目标结果：针对双孢菇规则生长、菌盖附土、菌盖重叠率不高或变形较小的图像，目标提取正确率大于92%；针对大面积菌丝包围菌菇、菌菇成簇倾斜、大小菌菇密集掺杂、菌盖堆积变形严重的图像，存在圆形检测不准、聚类误判或漏判等问题，目标提取正确率大于82%。本文采用的算法数据处理量小、计算速度快、适应性强，能够满足菌菇生产过程中长势自动监测、出菇统计等需求。     

微机开放性实验的实践与思考

就开放性实验的必要性提出了时间开放、空间开放和项目开放的概念，并列举了具有说服力的范例，提出了一些建议，以期对提高实验的教学质量有一定的积极作用。     

基于winSRFR河套灌区小麦不同面积不同生育期的入渗参数和糙率的研究

为了研究小麦不同生育期土壤入渗参数和田面糙率的规律,采用国内外学者对测定土壤入渗参数和田面糙率的方法和模型,根据春小麦不同生育期的水流推进和消退的实测数据,借助win SRFR模型,通过模拟灌溉过程,总结了河套灌区小麦不同畦田面积不同生育期的入渗参数和糙率的规律。结果表明:1春小麦田面糙率的变化范围为0.12~0.17;入渗系数的变化范围为47.78~75.03 mm/hα;入渗指数的变化范围为0.26~0.57。2田面糙率的变化规律总体表现为灌浆期分蘖期孕穗期拔节期,春小麦入渗参数随着小麦生育期逐渐减小,其规律为分蘖期拔节期孕穗期灌浆期。3数据经Sigmaplot显著性分析得出:入渗参数各生育期互相都有显著差异,而糙率在各个生育期除了孕穗期与分蘖期和拔节期无显著性差异其他都有显著差异。     

Determining crop-water production functions using yield–irrigation gradient algorithms

Crop-water production functions (CWPFs) are a useful tool for irrigation planning, but derivation of CWPFs by field experimentation is expensive, and traditional analytical techniques are not well suited to derivation of CWPFs. Physiologically based crop models provide a useful tool for simulation of agricultural experiments, but they have not been extensively applied to the task of CWPF determination. A new algorithm type based upon differential crop yield response to irrigation (“yield–irrigation gradients” [YIG]) is presented that uses these crop models to determine planning-level irrigation schedules and CWPFs. Three specific algorithms are developed within this type, varying in complexity, performance, and computational costs. Performance of the YIG methods is compared against a standard reference evapotranspiration method. In particular, the randomized iterative YIG (RIYIG) algorithm provides near-optimal results but at the highest computational costs of all the methods specified. All of the techniques presented have general applicability and are not limited to any one crop or location.     

密集排水孔幕饱和-非饱和全精细

对于有密集排水孔幕的工程渗流问题，只进行稳定饱和渗流分析往往是不够的，饱和-非饱和排水子结构分析方法正是解决了这一问题，同时为了全面精细地模拟排水子结构的实际渗流状态，首次提出了全精细数值模拟的理论和方法。在针对2类不同排水孔提出不同的完整水力学模型的基础上，详细讨论了不透水边界、已知结点水头边界、饱和逸出面边界、降雨入渗边界、非饱和蒸发入渗边界等有关子结构排水孔及其它表面可能存在的边界条件的分类处理方法，特别针对顶排型排水子结构排水孔内部水位提出了严密的数学处理方法。工程算例表明，本文提出的针对密集排水孔幕的全精细数值模拟方法是正确的，可以解决相关的工程渗流问题。     

Use of kinematic wave theory to model irrigation on cracking soil

Border irrigation in Australia is characterised by excessive run-off and variable water use efficiencies. This paper discusses an analytical irrigation model that, because of its simplicity, represents a tool for improving water management in border irrigation. Infiltration data on four replicate 75-m² plots were obtained from one irrigation of perennial pasture on a duplex, red-brown earth. Infiltration was characterised by high initial and low final rates. Kostiakov, modified Kostiakov, Horton, Philip and linear infiltration functions were fitted to the data. The linear function fitted the data well, and the parameters have physical interpretation. Consequently, an analytical kinematic wave model of border irrigation that incorporates the linear infiltration function is discussed. The analytical model was compared to more complex numerical models of border irrigation. The analytical model does not require a computer and performed sufficiently well to have application for border irrigation management in the field. Received: 6 January 1993     

温室番茄最适宜生态环境管理指标的研究

在湖北省鄂州节水示范基地展开试验研究,利用LPS-05型植物生长检测仪对温室番茄的生理状况及室内环境进行实时监测,定性分析番茄主要器官(茎、叶)对室内温湿环境所响应的微动态变化,以作物自身生理状况为参考标准,确定了适宜番茄生长的温室环境指标。番茄茎粗生长最优的临界夜间最低温度为17.8℃;2类典型天气条件下叶表面露水汽化时间分别为09:30(晴)和11:30(阴雨),均比空气滞后1h;在充分灌水条件下,温室番茄发生水分胁迫时空气饱和水汽压差的临界值约为2.7kPa。     

改进直线解析法确定各向异性含水层参数的计算

为了拓宽直线解析法的应用范围,以便分析抽水试验数据,确定各向异性含水层参数,较传统的简化方法,采用对井函数的级数展开式多保留一项的简化方式,建立了一种新的改进直线解析法。用正问题求逆的思路对其进行了可靠性的验证,并与Cooper-Jacob直线图解法的计算结果进行了对比,最后对方法进行了灵敏度分析。结果表明,改进直线解析法的计算结果与Cooper-Jacob直线图解法的非常相近;敏感性分析的结果则表明此方法对抽水试验数据具有的系统误差并不灵敏。与传统的Cooper-Jacob直线图解法相比,改进的方法具有更宽的适用条件,前者要求u<0.05而改进直线解析法仅要求u<0.2。     

半固定式喷灌系统设计中若干问题的分析

针对半固定式喷灌系统的特点，本文重点探讨了该系统移动部分设计中的一些问题。通过对移动部分投资及费用构成的剖析，提出了相应的数学模型，在此基础上，对部分重要设计参数的取值进行了分析，得出几点结论。     

Comparison of numerical, analytical, and empirical models to estimate wetting patterns for surface and subsurface drip irrigation

Due to increasing competition for water resources by urban, industrial, and agricultural users, the proportion of agricultural water use is gradually decreasing. To maintain or increase agricultural production, new irrigation systems, such as surface or subsurface drip irrigation systems, will need to provide higher water use efficiency than those traditionally used. Several models have been developed to predict the dimensions of wetting patterns, which are important to design optimal drip irrigation system, using variables such as the emitter discharge, the volume of applied water, and the soil hydraulic properties. In this work, we evaluated the accuracy of several approaches used to estimate wetting zone dimensions by comparing their predictions with field and laboratory data, including the numerical HYDRUS-2D model, the analytical WetUp software, and selected empirical models. The soil hydraulic parameters for the HYDRUS-2D simulations were estimated using either Rosetta for the laboratory experiments and inverse analysis for the field experiments. The mean absolute error (MAE) was used to compare the model predictions and observations of wetting zone dimensions. MAE for different experiments and directions varied from 0.87 to 10.43 cm for HYDRUS-2D, from 1 to 58.1 cm for WetUp, and from 1.34 to 12.24 cm for other empirical models.     

Drainage equations for random and irregular tile drainage systems

Subsurface drainage theory has been reviewed and applied to single tile systems in order to predict the hydrology of tile-drained watersheds where irregular or random drainage systems predominate. Simple analytical solutions for subsurface flow towards a single tile are proposed and evaluated. In these solutions, the spacing parameter, which characterizes drainage solutions for parallel systems, is replaced by a variable region of influence for transient scenarios. Evaluation of the proposed solution was carried out by comparisons with results obtained using a robust unsaturated-flow finite element model. The results predicted by the derived solution were found to be in close agreement with those obtained from the numerical simulations. Therefore, it is concluded that the proposed model holds well for situations of practical import and can be used in future work with large-scale hydrologic models.     

An approach for simulating the hydraulic performance of irrigation laterals

A new method for simulating lateral hydraulics in laminar or turbulent flow has been developed. The outflow is considered as a discrete variable and the friction head losses are calculated using the Darcy–Weisbach equation with an equivalent friction factor. Local head losses are also computed by applying equivalent coefficients that can be dependent on Reynolds number. Considering these premises, a compact expression that is valid for any type of regime has been deduced for calculating global head losses along any lateral stretch. The proposed method is useful to workout the hydraulic computation of laterals with the inlet segment at full or fractional outlet spacing, and complex laterals when a different pipeline diameter, slope, flow regime or emitter gap have to be considered.     

基于卷积模型的农业问答语性特征抽取分析

互联网农技推广社区每秒增衍问答数据近万组,这些海量数据具有隐性的词性、情感和冗余向量特征,实现数据聚合与数据块消减是该领域的难题。提出了一种基于卷积神经网络的农业问答情感极性特征抽取分析模型,结合农业分词字典,对数据集进行分词后使用Skip-gram模型转换为256维的词向量,利用批规范后的卷积神经网络对数据集进行训练,从而得到用于识别农技推广社区问答词性情感相似性的神经网络模型参数。试验结果表明,该方法能够准确识别测试样例集中的冗余队列,与其他5种文本分类方法进行比较,各项指标优势明显,针对测试集的语性特征抽取准确率达到82.7%。     

拖拉机悬挂式喷灌机配套技术研究

对拖拉机悬挂式或机的配套理论进行了系统研究和分析,提出了配套参数的计算方法及计算过程。在此基础上,以单台机组为基础,提出了配套机组系列参数计算方法,并在东方红－８０２型拖拉机配套的悬挂式喷灌设计与研制中得到应用,初步证明,提出的理论和计算过程能解决该机组的配套问题。