变性高阶比傅里叶非圆齿轮驱动差速泵设计与试验

为进一步提高差速泵性能,提出了一种变性高阶比傅里叶非圆齿轮驱动的六叶片差速泵。建立了变性高阶比傅里叶非圆齿轮传动模型和六叶片差速泵性能指标计算模型,编写差速泵性能分析软件。计算和分析不同阶数比和不同变性系数下的差速泵排量、流量和脉动率等性能,计算结果表明,高阶数比非圆齿轮副有利于提高六叶片差速泵综合性能,变性系数改变有利于降低单泵脉动率。经试验台测试,在相同泵尺寸及管路环境下,变性高阶比差速泵第一叶轮输入轴微应变均值下降35. 2%,降低了差速泵流量脉动。而非圆齿轮的不根切最大模数增加27. 7%,增强了承载能力。排量变化不大,降低了1. 2%。该设计更有利于低脉动、大载荷工况。     

自由节曲线非圆齿轮驱动差速泵设计与性能试验

为进一步改善差速泵性能,提出一种自由节曲线非圆齿轮驱动的四叶片差速泵,建立自由节曲线非圆齿轮驱动差速泵性能计算模型,编写差速泵性能计算软件,分析不同控制点下的差速泵排量、流量和脉动率等性能指标。结果表明,相比最优傅里叶节曲线,自由节曲线具有更好的局部优化能力,可有效提升非圆齿轮不根切最大模数和差速泵排量,降低差速泵脉动率,更有利于提高差速泵综合性能。试验表明,在相同泵尺寸及管路环境下,相比最优傅里叶非圆齿轮驱动的四叶片差速泵,自由节曲线非圆齿轮驱动的差速泵排量增加6.6%,不根切最大模数增加18.7%,有效提升了非圆齿轮承载能力,差速泵单泵脉动率降低8.3%,说明自由节曲线非圆齿轮更有利于提升差速泵性能。     

傅里叶非圆齿轮驱动四叶片差速泵设计与特性分析

提出了一种傅里叶非圆齿轮驱动的四叶片差速泵,并在叶片上安装与转动方向相同的单向阀。建立了傅里叶非圆齿轮传动模型和差速泵瞬时流量模型,采用Matlab编写了分析设计软件。利用该软件分析了相同泵结构参数下的3组典型节曲线参数对节曲线形状、差速泵瞬时流量、排量、单双泵和单向阀对脉动率的影响,并与偏心圆-非圆齿轮驱动的四叶片差速泵比较,得到双泵并联的傅里叶非圆齿轮驱动的差速泵相比偏心圆-非圆齿轮驱动的差速泵在排量相当的情况下能使脉动率降低10.3%,在叶片上安装与转动方向相同的单向阀有效地解决了困液问题。     

高阶椭圆锥齿轮泵的流量特性

针对齿轮泵的变量功能及非圆锥齿轮的应用,提出了一种新型相交轴变量齿轮泵——高阶椭圆锥齿轮泵.该齿轮泵是以高阶椭圆锥齿轮为工作转子的非圆锥齿轮泵.根据齿轮的空间啮合原理,给出了其工作转子高阶椭圆锥齿轮副的齿形生成方法.基于该种齿轮特殊的运动学特性,分析了高阶椭圆锥齿轮泵的传动特性,并对其工作结构进行了设计.依据球面微分理论,推导出了高阶椭圆锥齿轮泵的平均理论流量公式、瞬时流量公式以及流量脉动公式,同时分析了高阶椭圆锥齿轮的偏心率、阶数等参数对其流量特性的影响.在同等参数模型及工况条件下,将对高阶椭圆锥齿轮泵的平均理论流量、瞬时流量及其变量范围与圆柱齿轮泵和非圆柱齿轮泵的流量特性进行了对比分析,获得了该锥齿轮泵在同等条件下排量最大、变量范围最大的特点.     

差速泵叶轮边缘结构对转矩特性的影响

傅里叶非圆齿轮驱动的差速泵在负载工况下有明显的周期性冲击现象,而在空载状态不存在。为提升差速泵运行平稳性,开展数值计算和试验研究,首先建立差速泵数值计算模型,利用数值计算方法对差速泵流场和驱动非圆齿轮进行流固耦合计算。计算结果表明,差速泵在吸、排液工况交替瞬间,叶轮存在转矩突变现象,主要原因是叶轮旋转对进、出口关闭或打开瞬间形成了水锤效应。为此,对差速泵叶轮边缘进行微圆角优化处理以形成流场过渡区。仿真结果显示,叶轮优化后的输入轴周期性转矩突变峰值至少可降低21. 58%,且吸、排液腔压力分布更为均匀。经试验验证,转矩变化趋势及转矩突变点基本吻合,2个叶轮优化后转矩最大变化幅度平均降低51. 20%。结果表明,差速泵叶轮边缘对转矩特性影响较大,叶轮边缘优化对减弱水锤效应及改善叶轮转矩特性非常有效。     

内啮合渐开线齿轮泵角度变位参数的优化

渐开线内啮合齿轮泵是一种广泛应用在液压系统中的动力原件。研究了齿轮副角度变位参数对齿轮泵的排量、流量脉动性能的影响,以齿轮泵单位体积排量最大和流量脉动最小为目标建立多目标优化数学模型,进行参数优化。性能指标得到明显改善。     

基于最大形状系数的齿轮泵轻量化研究

为实现高综合性能渐开线齿轮泵的轻量化目的。首先,由泵的设计流程,推结出其轻量化在于关乎齿形参数的啮合角和关乎体积参数的模数确定;其次,由极限啮合位置和限定的齿顶角,以啮合角为变量,双节圆柱体积最小为目标,构建单变量优化模型;然后,针对泵用的这对具有最大形状系数的齿轮,创新出一款能无根切滚齿加工的双压力角齿刀轮廓;最后,以齿顶限速确定出标准化的模数。结果表明:齿轮泵归结为啮合角与模数的轻量化设计,概念清晰,计算简单;单变量齿形优化,质量好、效率高;近上限的模数标准化取值,泵的综合性能好;压力角和顶隙系数对轻量化影响甚微,为恒取标准的20°压力角提供依据;齿顶角越小,齿数越少,最大形状系数越大;所推荐的齿数为7,重合度约1.1,困油性能好,啮合角约30°,传动效率较高;双压力角齿刀具有顶刃圆角小和齿轮滚齿加工无根切的特点等。为其它容积泵的轻量化设计,提供一种创新的途径和方法。     

非圆齿轮行星轮系传动的栽植机构参数优化与试验

为了进一步优化栽植嘴的轨迹、姿态及其挖出的穴口形状,提高钵苗移栽的立苗率,提出了基于两级非圆齿轮行星轮系传动的栽植机构组合设计思路,运用变性椭圆-共轭非圆齿轮、变性偏心圆-共轭非圆齿轮、变性巴斯噶蜗线非圆齿轮、变性傅里叶非圆齿轮和变性正弦非圆齿轮5类非圆齿轮副,组合设计了25种不同的栽植机构。建立了基于非圆齿轮行星轮系传动的栽植机构通用数学模型,并将通用数学模型代入旋转式钵苗栽植机构多目标优化模型,根据给定的栽植农艺条件,优化得到了满足理想栽植要求的栽植机构类型及其对应的机构参数。选取其中的偏心-椭圆齿轮行星轮系栽植机构与变性椭圆齿轮行星轮系栽植机构进行对比分析,结果表明运用多种非圆齿轮副进行组合设计的栽植机构具有优越性。根据优化得到的栽植机构类型及其对应的参数进行结构设计和样机研制,并进行了运动学高速摄像试验和模拟田间栽植试验。由高速摄像试验得到的轨迹、姿态、速度等指标和理论计算的对比分析,验证了通用数学模型的正确性;由模拟田间栽植试验可得本栽植机构立苗率较高,约为95%。     

拖拉机最终传动多目标模糊可靠性优化设计

综合考虑拖拉机单级外啮合直齿圆柱齿轮最终传动的承载能力、结构、齿面磨损和传动效率等问题,应用模糊数学和可靠性理论以及多目标优化技术对该机构进行设计.建立了以机构的体积和两齿轮的最大滑动系数最小、效率最高为目标函数,以模数、小齿轮齿数、齿宽和啮合角为设计变量的多目标模糊可靠性优化设计数学模型,应用多目标优化的模糊解法和遗传算法对其进行求解.在保证最大滑动系数不超限的前提下,模糊可靠性优化设计方案比常规可靠性优化设计和原设计方案体积分别减小1.55%和6.74%,且传动效率得以提高.     

基于多目标遗传算法的404P型拖拉机齿轮系优化

针对404P型拖拉机变速箱齿轮系存在的齿轮总质量大、疲劳强度低、换挡平顺性较差的问题,建立了以变速箱齿轮系总质量最小、疲劳强度最高、换挡平顺性最高为优化目标的齿轮系多目标参数优化数学模型。提出利用带精英策略的非支配排序遗传算法(NSGA-Ⅱ)进行多目标优化求解。基于Matlab优化工具箱编写程序进行齿轮系参数的优化设计,结果表明,齿轮系总质量优化率差值为187.30%,齿轮系疲劳强度优化率差值为85.27%,齿轮系换挡平顺性优化率差值为9.09%。相比于传统经验设计,进一步提高了404P型丘陵山地拖拉机的变速箱传动性能。     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。