基于ADAMS的玉米收割机主要部件仿真分析

采用离散梁法建立玉米秸杆模型,利用UG建立分禾器和摘穗辊模型,导入ADAMS后添加相应约束进行仿真分析。通过该方法实现了分禾器和摘穗辊参数设计的系列化,得到了满足实际需要的三维模型,缩短了开发周期,为新型自走式玉米收割机的研制提供了一定的理论依据。     

基于ADAMS的玉米植株收获过程仿真

在Pro/E中建立了摘穗辊及玉米植株收获模型,利用Pro/E与ADAMS的接口MECHANISM/Pro将所建模型导入了ADAMS中,通过分析植株受力,在ADAMS中建立了玉米植株与摘穗辊收获过程的虚拟样机模型,并添加约束和驱动.运用传感器技术,通过脚本仿真控制实现了玉米植株与摘穗辊收获过程的仿真,分析了玉米植株在倾角为79°时的收获数据,最后依据收获时间、果穗啃伤分析了倾角对收获过程的影响,得出了玉米植株收获的理想倾角为89°,为立辊式玉米收获机关键部件的设计提供了参数支持.     

玉米收获机分禾器的研究

分禾器虽然结构简单,但是对整机性能影响较大.一方面,要求分禾器具有扶禾的能力;另一方面,还要求分禾器能够适应不同行距要求.分禾器直接决定着玉米植株能否被顺畅地喂入并导入到摘穗装置,完成摘穗工作.为此,通过对分禾器结构参数与玉米植株折断临界角关系的分析,提出了分禾器结构的优化设计方案,提高了分禾器的扶禾能力,有效地降低了玉米植株在喂入过程中折断与被推倒的可能性.     

间距自适应差速玉米摘穗辊设计与试验

分析了影响卧辊式玉米收获机摘穗过程中作业质量的主要因素。通过改变摘穗辊间距以适应不同直径的玉米秸秆,有效解决了玉米收获机工作时堵塞的问题。通过两摘穗辊转速不同步的办法减少了玉米果穗的掉粒损失。通过CATIA软件对间距自适应差速摘穗辊进行了建模,并通过ADAMS软件与间距固定摘穗辊进行了仿真对比分析,通过ADAMS仿真试验,确定了内外摘穗辊的最佳转速,即内侧摘穗辊转速为900 r/min,外侧摘穗辊转速为860 r/min。田间试验中无秸秆堵塞摘穗辊现象发生,且籽粒破损率和损失率之和为0.11%,远小于国家标准的5%。     

水平摘穗辊与可退让拨禾器组合式玉米摘穗机构研究

传统玉米收获机的摘穗辊结构长度和质量较大。不易与我国大量拥有的中小型拖拉机悬挂配套，而采用短摘穗辊后果穗损失增加。针对这一问题，研制出水平摘穗辊与可退让拨禾器组合式摘穗机构。文中论述了这种摘穗机构的结构，在分析研究其基本原理和作业性能的基础上。试验验证了摘穗辊和拨禾器结构参数对作业性能的影响。     

基于激振理论的玉米多棱摘穗辊设计与试验

针对当前纵卧辊式玉米收获机作业存在籽粒啃伤严重和落粒损失大的问题,以激振理论为指导,以玉米果穗与茎秆分离为条件,建立了适于玉米机械化收获的玉米激振摘穗理论模型;以该激振摘穗模型为指导,构建并优化了适于玉米激振运动的摘穗辊外形结构和配置方式,开发了相应的激振摘穗试验台;采用Box-Behnken试验设计方法,研究了激振摘穗辊棱边数、振幅、摘穗辊转速对果穗摘穗过程籽粒破损率和落粒损失率的影响规律,建立了试验因素与考察指标之间的回归方程,并生成了相应的响应曲面。结果表明,激振摘穗装置中棱边数、振幅和摘穗辊转速对收获过程果穗籽粒破损率和落粒损失率有显著的影响。以非线性规划理论为指导,确定了最佳组合为摘穗辊转速950 r/min、棱边数8、振幅0. 75 cm,在该条件下进行了试验验证,得出平均籽粒破损率为0. 124%,平均落粒损失率为0. 228%,均低于国家玉米收获机械技术标准要求。     

新型仿生摘穗辊的设计

根据人工摘穗中的仿生学原理,建立了玉米摘穗过程受力情况的力学模型;运用软件对摘穗辊进行三维建模和运动学仿真分析,模拟出主要部件的运动过程,得出不同摘穗辊材料以及不同摘穗辊倾角的摘穗特征,并对摘穗过程中摘穗辊的受力情况进行了理论计算,基于以上分析结果设计制造新型玉米摘穗辊。该摘穗辊在实验室模拟摘穗过程中成功应用表明受力分析及设计是科学合理的。     

旋切数学建模下的玉米收获机结构优化分析

以玉米收获机为研究对象,针对现有玉米收获机在摘穗过程中造成玉米穗出现的咬伤、无法正常采摘现象,通过旋切数学建模的方法进行摘穗辊结构优化设计。对摘穗辊的现有结构进行分析,得出玉米收获正常进行的限制条件,并计算出摘穗过程中摘穗辊上的受力及功率消耗。根据计算结果进行摘穗辊的结构设计,同时采用旋切数学建模的方法,建立摘穗辊工作中的碰撞模型和接触模型。仿真分析表明:玉米穗在进入或脱出阶段,摘穗辊会出现较大的动量变化及力的冲击变化,研究结果可为后续玉米收获机摘穗辊的设计提供参考。     

立辊型玉米收获机摘穗辊辊型对工作性能的影

摘穗辊辊型对玉米联合收获机作业效果的影响显著.通过正交试验研究了立辊型玉米收获机摘穗辊辊型对作业主要性能参数的影响,同时对各运动参数的交互作用进行对比分析,确定了各运动参数的最佳组合.摘穗辊的花纹形状对损失率的影响显著,圆顶花纹在摘穗辊转速为1 000 r/min的条件下工作可以获得最佳效果.辊型对功率影响显著,圆顶花纹在摘穗辊转速为900 r/min的条件下工作的功率消耗最低.摘穗辊的工作间隙与损失率之间呈线性关系.     

基于ADAMS的玉米茎秆与收获割台仿真

茎秆折断在玉米收获过程中已成为一个迫切需要解决的问题。为此,通过ADAMS/VIEW拉伸法建立玉米茎秆柔性体模型,利用Pro/E建立割台三维模型,导入Adams后添加相应约束和驱动进行仿真。仿真结果表明:分禾器外表面过渡处越平滑,植株越不易被推倒,减少了玉米茎秆的折断的几率。同时,通过虚拟正交试验,得到拉茎辊转速和机器行走速度的最优组合为n=900r/min,v=2.16km/h,可以降低对玉米茎秆的损伤程度,减少折断玉米茎秆的几率。     

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。