不同特性泵串并联系统的性能预测

不同特性的离心泵串、并联工作的情况较多，运行较复杂。传统的性能预测方法不能得出水泵串并联系统的完全性能曲线。该文引入了水泵全特性中的两个制动工况，即正转倒流制动工况和正转正流制动工况，通过图解得到了两不同特性泵串、并联工作时的完全性能曲线；同时引入了泵的水泵工况和两种制动工况的性能曲线方程，通过理论方法计算出泵串并联系统的完全性能曲线。     

马铃薯淀粉螺旋式清洗机研制

马铃薯淀粉清洗机是淀粉加工工序中的清洗设备，为淀粉的后序加工及保证淀粉的品质起到了关键环节。本文主要介绍马铃薯淀粉螺旋式清洗机的工作原理、性能特点、关键部件设计和使用效果。     

车辆液力机械传动系统换挡过程动态特性仿真

为研究车辆液力机械传动系统换挡过程的动态特性，基于动力换档离合器及其液压控制系统的结构和工作原理，建立了车辆动力－传动系统的动力学模型，并进一步分析建立了各组成部分的数学模型。在Matlab/Simulink图形建模环境的支持下建立了车辆动力－传动系统的仿真模型。仿真结果表明，该模型能够有效地模拟车辆液力机械传动系统换挡的动态过程，可以用来预测系统的性能，进而为结构的改进和控制系统的设计提供依据。     

叶片宽度对锥体叶轮离心风机性能影响的试验研究

本文基于对出口速度三角形的分析，建立了叶片宽度、流量与性能间的函数关系，并进行了较系统的试验研究，建立了相应的性能预测模型，为该类风机的变型设计和性能预测提供了依据．     

马铃薯淀粉全旋流分离系统计算机模拟

在对现有分离系统分析的基础上，根据近几年的生产实践及在实验台上测量的数据，利用数学应用软件Matlab中的SIMULATE功能模拟实际生产过程。通过对全旋流分离马铃薯淀粉过程的计算机模拟，可以在已知进料流量、淀粉浓度、进水量以及各级配置的情况下得出各级的分离情况以及整个系统分离状况，以达到预测的目的；可以指导全旋流分离系统的优化设计并为调试安装节省大量的人力和物力。     

基于近红外光谱的神经网络预测大米直链淀粉含量

借助主成分分析，确立了用于近红外光谱分析的BP神经网络的输入输出模式对；并用BP神经网络方法建立了不同类型、不同粒度的大米样品直链淀粉含量预测模型；考察了模型的预测能力，其预测值与用标准方法取得的化学测定值间具有良好线性关系（相关系数达0．9）。用BP神经网络可降低因样品粒工的不同而对预测结果造成的差异。     

马铃薯淀粉分离用旋流管的性能研究

阐述了旋流管内流体运动的规律，分析了马铃薯淀粉旋流分离的内在机理及特点，通过单级试验，具体分析了旋流管的压降、底流直径和进料浓度对处理量、底流分离和淀粉分离效率的影响，为系统研究提供了依据。     

低矮花卉浇灌系统的自动控制设计

针对低矮花卉浇灌系统成本较高、温湿度控制滞后的问题,对其自动控制部分进行了设计和改进。浇灌系统主要由单片机、参数采集模块、浇水模块、远程控制模块、报警模块和显示器组成。浇灌系统通过采用时间序列预测方法预测土壤温湿度,采用CUSUM算法检测土壤温湿度是否偏离预测值,以保证浇灌过程中土壤的温湿度始终在最适宜范围。为验证该低矮花卉浇灌系统的性能,对其进行试验,结果表明:浇灌系统可预测土壤温湿度变化,对花卉浇灌系统进行自动控制,且节水性能良好。     

一种基于车路偏差模型的车道保持系统开发

为解决由于行驶环境较大的不确定性影响车辆横向运动控制系统对于车道中心线的跟随性能问题,通过状态预测方法,结合最优控制策略设计了车辆横向控制算法。本文通过基于状态预测的横向车辆模型的建立和控制器的设计,预测了车-路偏差,提高了控制系统的控制精度。试验结果说明,采用本文建立的基于状态预测的最优控制算法能够有效降低被控车辆在行使环境变化范围较大工况下的车-路偏移量,在该工况下系统具有良好的跟随性能。     

基于先进通信技术的农田灌溉系统研究

针对传统灌溉方式浪费水资源的问题,基于电力线设计了自动灌溉系统,由一个主模块和N个从模块构成,以单片机为控制中心。系统通过电力线进行通信和远程控制,采用灰色预测模糊PID控制算法控制灌溉系统的需水量。为验证该系统的性能,对系统进行了灌溉试验。试验结果表明:系统可以完成灌溉系统数据的稳定传输,能够稳定控制灌溉过程的水流量,且灌溉系统运行稳定,工作性能良好。     

Estimates of deep percolation beneath cotton in the Macquarie Valley

Expansion of flood irrigation in the Lower Macquarie Valley of New South Wales, Australia, has been suggested as a major cause of increased groundwater recharge. The aim of this study was to estimate deep percolation under irrigation on two soils in the valley, in order to infer groundwater recharge. Three methods were used; water balance, Darcian flux calculations and chloride mass balance modelling. Chloride mass balance modelling and the water balance method gave comparable estimates of deep percolation for each soil. Chloride mass balance modelling was identified as the most reliable method for estimating deep percolation, but only gave an estimate for the entire growing season. These estimates were 214 and 104 mm for a cracking clay and red brown earth, respectively. While there is potentially greater error associated with estimates obtained using the water balance, this technique provided estimates of deep percolation for each individual irrigation. Results of the water balance indicated that deep percolation was greatest early in the growing season, following initial wetting of the soil, when the crop had a low leaf area index. Results calculated using Darcian flux equations were highly variable, and were therefore unreliable estimates of deep percolation. Groundwater recharge, inferred from estimates of deep percolation determined with the chloride mass balance model, was used to estimate the magnitude of potential annual groundwater rise. The potential groundwater rise during the 1992/1993 cotton growing season ranged from 465 mm beneath the cracking clay to 267 mm under the red brown earth. It is suggested that groundwater recharge and rise were highly dependent on the weather conditions prevailing during this period. Received: 24 January 1997     

三组非圆齿轮行星轮系振动发生器的动平衡分析

为了提高果秧分离振动发生器的工作效率和稳定性,针对非圆齿轮啮合传动因质心变化而造成的轴上受力不平衡及振动较大等问题,对非圆齿轮行星轮系结构进行了动平衡分析。简化项目组前期提出的3组非圆齿轮行星轮系振动发生器模型,得到非圆轮系偏心质量的大小和分布,并通过对非圆齿轮行星轮系静力学分析,确定了其平衡面间距,利用质径积的分解求得了非圆行星轮系的平衡质量。利用3组非圆行星轮系虚拟模型进行运动学仿真分析,获取平衡前后轴承座支反力变化曲线并对其最大幅值进行对比分析,发现平衡后轴承座的受力明显减小,说明了3组非圆行星轮系振动发生器受力更均衡,证明了动平衡分析的正确性。该研究可为3组非圆行星轮系振动发生器装置进一步优化奠定理论基础。     

Correcting soil water balance calculations for dew, fog, and light rainfall

In Mediterranean climates, adoption and use of the ET-based scheduling method is limited to regions characterized by considerable contributions to evapotranspiration from fog interception, dew, and light rainfall. While the crop evapotranspiration is often accurately estimated, the water balance is frequently in error because a considerable portion of the energy expended is used to vaporize water from the plant surfaces rather from inside the leaves (i.e., transpiration). Growers in regions with considerable fog, dew, and light rainfall are hesitant to use ET-based scheduling because the cumulative crop evapotranspiration between irrigations is often considerably higher than the soil water depletion. A correction for these surface contributions is clearly needed to improve the water balance calculations and to enhance adoption of the ET-based scheduling method. In this paper, we present a simple, practical method to estimate the contribution of fog interception, dew, and light rainfall to daily crop evapotranspiration, and we show how to use the method to improve water balance calculations.     

Water balance estimates over Greece

Water balance for 31 locations in Greece is calculated on the basis of long-term average monthly precipitation, evapotranspiration and combined soil and vegetation characteristics, according to the method proposed by Thomthwaite and Mather. Monthly evapotranspiration estimates are calculated from 27 years (1960–1987) of routine meteorological data using the original Penman method. Soil and vegetation characteristics specific for the locations under study are combined in the water capacity of the root zone (WCRZ). similar water balance calculations were carried out using various fixed values of WCRZ for all stations, to evaluate the effects of soil and vegetation through the WCRZ in the final estimates of soil moisture deficits. Water balance calculations were also performed using average monthly evapotranspiration estimates calculated according to the empirical Tbomthwaite method. Results were compared in order to show possible differences that could be attributed to the method of estimating evapotranspiration. Finally, results obtained with a value of WCRZ fixed at 300 mm and potential evapotranspiration estimated by the Thomthwaite method for the period 1969–1987 were compared with existing similar results over a longer period in the past (1931–1968), in order to detect diachronic changes in the water balance components over the same regions in Greece.     

自适应弹塑性数值模拟系统的工程应用

数值模拟技术对于预示金属成形过程中的流动规律进而指导工艺过程及模具设计具有重要作用。国外已在金属成形数值模拟中引入自适应技术,该技术消除了网格生成的盲目性,实现了以尽可能少的计算量获得指定精度要求的解,而国内这方面的研究不多。本文研究开发了自适应弹塑性数值模拟系统,阐述了该系统的功能及特点,重点论述了系统的工程应用价值。     

Conjunctive use modeling for multicrop irrigation

A mathematical model is developed to arrive at an optimal conjunctive use policy for irrigation of multiple crops in a reservoir-canal–aquifer system. The integration of the reservoir operation for canal release, ground water pumping and crop water allocations during different periods of crop season (intraseasonal periods) is achieved through the objective of maximizing the sum of relative yields of crops over a year considering three sets of constraints: mass balance at the reservoir, soil moisture balance for individual crops, and governing equations for ground water flow. The conjunctive use model is formulated with these constraints linked together by appropriate additional constraints as a deterministic linear programming model. A two-dimensional isotropic, homogeneous unconfined aquifer is considered for modeling. The aquifer response is modeled through the use of a finite element ground water model. A conjunctive use policy is defined by specifying the ratio of the annual allocation of surface water to that of ground water pumping at the crop level for the entire irrigated area. A conjunctive use policy is termed stable when the policy results in a negligible change in the ground water storage over a normal year. The applicability of the model is demonstrated through a case study of an existing reservoir command area in Chitradurga district, Karnataka State, India.     

人工湿地生态系统氮循环试验研究

构建人工湿地生态系统,可将其分为3个阶段,其中,第一和第三阶段以硝化反应和有机氮生物合成为主,第二阶段以反硝化为主;以质量平衡理论为基础,建立了人工湿地生态系统中各形态氮化合物迁移转化模型,并利用各形态氮实测值计算得到氮循环质量平衡图。结果表明:在人工湿地生态系统的水体-基质-植物多介质中,不同形态氮之间发生迁移转化,水体和基质中氨态氮和硝态氮均有所减少,植物吸收合成部分有机氮,系统最终出水脱氮效率为85%。     

碳平衡法测量燃油消耗量的应用研究

介绍了碳平衡原理,依据碳平衡原理建立的油耗快速检测系统在测量车辆耗油量上可实现不解体检测。本着实用要求,结合试验对所建立的试验系统分别用市售90#汽油和93#汽油进行验证,获得了较好的效果。试验证明,依据碳平衡法理论建立的简单流量测试系统是可行的。     

Water use by an irrigated almond orchard

The evapotranspiration rate of a high-yielding (4.3 t/ha) almond orchard was measured by the eddy covariance technique. The site was subject to advection (LE/Rn > 1) for one-third of the mid-season. The slope of energy balance equation calculated from half-hourly flux data was 0.87. Flux data were transformed by forcing closure of the energy balance to give a seasonal ET of 1,450 mm (ETo 1,257 mm). This value could be reconciled with ancillary measures of soil salinity and water content, and plant water status. The mid-phase crop coefficient was 1.1 which was 0.1 higher than a recently published value. Use of the transformed value of ET in calculations of field application efficiency and annual drainage gives values of 98% and 24 mm, respectively.     

Experimental study of water flow and sulphate transport at monolith scale

In this study, sulphur transport processes and effect of flow rate on sulphate breakthrough curves (BTCs) were studied on six undisturbed large soil monoliths (each having roughly a volume of 0.5 m³), collected from two different agricultural soils being loamy and sandy loam. In the laboratory, each monolith was equipped with different measuring devices to monitor soil water content, bulk soil electrical conductivity (ECa), soil temperature, pressure head, outlet flux, and pH. Four unsaturated steady state experiments were carried out on each monolith using two different imposed fluxes (referred to as low and high). First a chloride breakthrough experiment was performed to identify the basic transport processes followed by sulphate breakthrough experiment for the identification of the important sulphate transport processes. Water and solute (chloride and sulphate) mass balances were made to evaluate effective sulphate transformations at the scale of the monolith.The relative water mass balance errors ranged between −4.0% and 5.0%. The chloride mass balances were almost as good as those obtained for water, whereas the sulphate mass balance revealed that sulphate was subjected to adsorption and immobilization during the transport. The high flux sulphate experiments resulted in relatively large mass balance discrepancies compared to the low flux sulphate experiments. The sulphate breakthrough curves (BTCs) were somewhat retarded in the loamy monoliths whereas both chloride and sulphate BTCs were significantly affected by preferential flow in the sandy loam monoliths. Standard batch experiments showed that the adsorption isotherm was linear and immobilization occurred in both soils studied whereas net mineralization was essentially low. The effect of flow rate on the BTCs and influence of water content on immobilization process was not apparent.