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.     

基于Solidworks的弧齿锥齿轮齿面三维精确建模

弧齿锥齿轮的三维建模是用ANSYS对齿轮副进行分析的基础。根据弧齿锥齿轮加工原理和齿轮啮合原理得到齿面方程,用Matlab编程计算出齿面点坐标,将坐标导入到Solidworks中,生成空间曲线,将曲线转化为实体模型,完成弧齿锥齿轮的三维建模。     

弧齿锥齿轮大轮齿顶倒角加工模型与虚拟加工

通过分析弧齿锥齿轮大轮齿顶倒角加工原理,推导了弧齿锥齿轮大轮齿顶倒角刀具轨迹模型,基于VERICUT虚拟加工软件平台,建立了弧齿锥齿轮齿顶倒角NC机床模型及弧齿锥齿轮齿顶倒角虚拟加工模型.对一具体的弧齿锥齿轮进行了刀具轨迹计算,并在VERICUT环境下进行了虚拟加工,测量结果表明弧齿锥齿轮大轮齿顶倒角虚拟加工模型满足设计要求.     

弧齿锥齿轮切齿机床参数的调整计算

针对弧齿锥齿轮传动的综合问题,阐述了弧齿锥齿轮切齿参数在刀具成形半径受限、展成链传动比受限、刀具成形半径和展成链传动比同时受限三种条件下机床调整的计算方法,从而为满足弧齿锥齿轮传动啮合质量,即局部接触斑点尺寸范围、旋转传动相对均匀性,提供了切实可行的思路,并用典型计算实例,演示了弧齿锥齿轮磨齿机床参数调整的步骤、方法。     

螺旋锥齿轮研齿系统的动态响应

考虑齿侧间隙和齿轮传动误差的影响,建立了两自由度螺旋锥齿轮研齿系统的振动模型。通过数值计算,得到了不同制动转矩下,研齿系统的动态响应。根据时间历程和相图可知,制动转矩较小时,轮齿的啮合、碰撞和脱啮交替进行,随着制动转矩的增大,齿背碰撞消失,最后进入完全的齿面啮合状态。     

螺旋锥齿轮齿面误差修

研究了基于数控加工螺旋锥齿轮齿面误差修正技术.提出了一种由摇台型机床调整参数向Free-Form机床转换的方法,建立了基于数控加工齿面误差模型;在此基础上,以齿面误差平方和最小为目标函数,优化摇台型机床调整参数,再将其转换为数控加工形式,从而实现数控齿面修正.最后通过算例表明,经过改变加权系数和优化可以达到齿面误差较高精度修正要求.     

混合弹流润滑下弧齿锥齿轮传动啮合效率计算方法

齿轮的实际润滑状态为兼具完全弹流润滑和边界润滑的混合弹流润滑.通过推导混合弹流润滑下齿轮的平均滑动摩擦因数,结合弧齿锥齿轮的几何接触特性与承载接触特性,计算其瞬时接触椭圆长轴上各点的滑动摩擦功率损失,拟合了啮合周期内的滑动摩擦功率损失函数,经过积分运算得到了混合弹流润滑下弧齿锥齿轮传动的啮合效率.通过与格利森公司计算锥齿轮传动啮合效率的方法对比分析,表明该方法计算正确且精度高.     

上海纽荷兰SNH550拖拉机后桥中央传动的检查与调整

拖拉机后桥中央传动的使用寿命与传动效率,在很大程度上决定于锥齿轮配合关系的正确性。本文主要讲叙了上海纽荷兰SNH550拖拉机主动弧齿锥齿轮轴承间隙检查调整、齿轮啮合情况的检查与调整。     

基于romax修形斜齿轮动力学特性研究

斜齿轮是齿轮传动的重要组成部分,由于标准齿面斜齿轮传动过程中存在传动误差峰峰值和接触应力过大的问题,使得传动系统振动和噪声过大.而采用修形的方法可以有效提高齿轮传动稳定性和齿面啮合效果,用以提高齿轮传动系统动力学特性.本文基于romax软件提供的修形算法——优化遗传算法进行修形,修形曲线选择抛物线,并将得到的最佳修形结...     

中央传动锥齿轮副早期磨损的原因

修理中,中央传动锥齿轮副早期磨损的主要原因是:未能保证其正确的啮合条件,缩短了锥齿轮副的使用寿命。归纳为以下六点: (1)检修中安装调整不当。破坏了大小锥齿轮的啮合条件,导致齿面剥落及早期磨损。如旧锥齿轮副仍按新锥齿轮副的间隙安装,使大小锥齿轮之间的相对位置发生变化,同时,又没有合理的调整,则破坏了原啮合条件。     

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。