平面二次包络环面蜗杆副的现状及有关技术问题研究

平面二次包络环面蜗杆副是一种极其重要且应用广泛的传动方式。笔者在查阅大量文献的基础上,对环面蜗杆副的基本特性进行了简单的介绍,并对其国内外发展现状进行了研究,同时又对环面蜗杆副参数的选择、传动参数的适应范围及控制制造水平等方面进行了分析和探讨。研究结果表明,蜗杆副齿面的曲面结构将直接影响蜗杆副的性能优劣,合理的曲面结构能充分发挥蜗杆副的优点,相反则会影响蜗杆副的啮合传动,损害蜗轮蜗杆元件;蜗杆副的曲面结构与它的结构参数、传动参数有直接的关系,因此,对蜗杆副齿面进行接触分析,讨论齿面不同接触线的出现条件,意义重大,能够为今后蜗杆副的力学分析、误差分析以及仿真建立一定的基础。     

弧齿锥齿轮传动误差曲线的双层优化法

针对轮齿啮合分析得到的传动误差曲线与预置的对称抛物线型传动误差曲线的差别,提出了弧齿锥齿轮传动误差曲线的双层优化法。分为外层优化和内层优化,两者交替进行。在内层,基于局部综合法设计小轮机床加工参数,进行轮齿啮合分析,获得传动误差曲线和齿面接触印痕。为了保证实际传动误差曲线与理论传动误差曲线在最小二乘意义下吻合,建立吻合度目标函数,通过调整加工小轮时的4个高阶变性系数,消除轮齿啮合分析得到的实际传动误差曲线与理论传动误差曲线的差距。在外层,为了保证传动误差曲线对称,建立对称度目标函数,通过调整齿面参考点沿齿高的位置,使传动误差曲线两侧对称。以某弧齿锥齿轮副为例进行验证计算。结果表明,双层优化法能够实现预置的对称抛物线型传动误差曲线。     

基于MATLAB的滚柱环面蜗杆副三维实体建模

为了得到更加简单直观的滚柱蜗杆副,根据环面蜗杆副啮合过程中的啮合方程以及蜗杆自身的齿面方程,利用MATLAB数据可视化的功能绘制出蜗杆齿面的φ1线,通过Pro/E的三维建模功能,即可构造环面蜗杆和蜗轮的三维实体,最后将其装配完成。本文力图将复杂的理论公式研究变得更加具体化,希望为今后的蜗杆副理论研究提供参考。     

平面二次包络环面蜗杆的建模与五轴数控加工技术研究

在获得平面二次包络环面蜗杆三维模型的基础上,运用Cimatron E8.5进行数控编程与仿真加工,为平面二次包络环面蜗杆的五轴数控加工提供了可靠的依据,并使其加工更快捷、简便。     

超环面行星蜗杆传动啮合特性研究

采用空间啮合理论对超环面行星蜗杆传动的啮合特性进行了系统的研究，给出了定子螺旋面和转子蜗杆齿廓曲面方程以及行星轮轮齿滚珠与定子螺旋面及转子蜗杆之间的接触线方程以上述工作为基础，进而导出了行星轮轮滚珠与定子螺旋面及转子蜗杆之间的接触线上诱导法曲率以及接触线与相对速度之间有计算公式，分析了啮合特性的影响因素和影响规律，为该种传动的设计与制造提供了理论依据。     

基于啮合过程的斜齿轮高阶传动误差设计

齿轮传动误差的形状和幅值是影响齿轮振动噪声的关键因素。根据齿轮啮合过程,提出了一种新的齿轮传动误差的设计方法。根据一个啮合周期啮合点的位置,设计了一种高阶传动误差曲线,来避免齿轮的边缘接触,降低应力集中,并利用齿面接触分析技术对齿轮的啮合状况进行了仿真,验证了上述结论。     

同平面相交轴线齿轮的正反转啮合分析与稳定性评价

线齿轮是一种基于空间曲线啮合的精密齿轮传动件,特别适用于微机电系统的设计。由于装配误差、尺寸误差等因素,加上线齿轮副在正反转时所受的推力方向不共线,导致线齿轮啮合的稳定性和传动精度受影响。本文以最常用的同平面相交轴线齿轮为例,在建立线齿轮数学曲面模型的基础上,分析线齿轮的啮合特性,计算线齿接触线的基本矢,求得线齿根部所受推力方向的偏差。对线齿轮进行反转分析,发现线齿轮反转时的空间曲线啮合方程与正转时不同,导致其线齿接触线方程和其推导出的主法矢与正转时均存在差异。应用Mathematica软件推导出线齿轮反转时的空间曲线啮合方程、线齿接触线方程以及啮合点处的基本矢,再利用主法矢的夹角评价该差异。最后,通过实例数据的代入计算,对分析和推导进行验证,为线齿轮啮合稳定性和传动精度提供评价方法与指标。     

汽车后桥锥齿轮测量及传动仿真

基于一种新的齿轮误差测量方法本文提出一种新的误差表示方式,即以实际齿面上的点相对于对应理论齿面上点的法向偏移量为齿轮误差。该误差可以包含齿轮所有误差信息。考虑齿轮副啮合过程中的正常啮合、脱啮和齿背啮合及碰撞的情况建立齿轮传动系统振动数学模型。通过对该模型的分析探讨了在考虑齿轮传动误差的情况下作用在该系统的静力矩以及动力矩之间的关系对齿轮副啮合拍击的影响。     

平行动轴少齿差传动多齿接触问题研究

以有限元弹性接触分析理论为基础，建立了平行动轴少齿差内啮合齿轮多齿接触时的有限元模型，提出了一种对平行动轴少齿差内齿轮副啮合过程中实际接触齿对数、齿间载荷的分配及齿面载荷分布的分析计算方法。以SH－350型平行动轴少齿差双环减速器为例，分析了其在额定载荷工况下的实际接触齿对数、齿间载荷分配及齿面载荷分布规律等，并利用应变测试方法进行了相应的实验，验证了理论分析计算的结论，为平行动轴少齿差内啮合齿轮传动承载能力的估算，齿轮几何参数的确定及零部件的强度分析计算提供了理论依据。     

基于齿面印痕控制的弧齿锥齿轮公差优化设计

应用基于特征变动的三维公差建模理论和传递矩阵累积方法,建立了系统综合安装误差与弧齿锥齿轮4个当量错位量的关系.给出了考虑安装误差的齿面接触分析算法,并对齿面印痕数字化特征完成了定义.以齿面啮合印痕相对于安装误差的敏感度为优化目标函数,在满足传动性能要求和成本限制的情况下,应用遗传算法对零部件精度进行优化.以弧齿锥齿轮为例,通过对优化前后啮合印痕、传动误差的比较,验证了该公差优化方法的可行性.     

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。