旱作农业耕作机械系统的探究分析

农业机械发展的方向是机械化、自动化,是农业可持续发展的最终方向。文章结合经过多年的实际农业工作经验,阐述了对机械化农业生产耕作的认识,供同仁研究参考之用。     

农业物料力学试验测控系统设计

介绍了基于计算机的农业物料力学试验测控系统的组成和测控软件。应用结果表明，该系统工作可靠，虚拟仪器面板操作简便，实现了农业物为力学试验数据采集及试验过程自动化。     

谷物循环干燥机控制系统硬件设计

针对循环式缓苏干燥机的工作特性，采用单片机模糊控制方法进行控制系统硬件设计，为解决单片机与计算机的双向通讯，实现干燥过程专家智能控制提供硬件基础。     

A longitudinal examination of business performance indicators for drought-affected farms

Frequent severe droughts can financially cripple dryland farm businesses and farmers need effective business strategies to survive. This study analysed the economic performance of 123 farms in a rainfed agricultural region of Australia from 2004 to 2009, a period that included severe droughts in 2006 and 2007. The business indicators examined were business equity, operating profit/ha, return on capital, and the debt to income ratio and the droughts altered these indicators for many of the farms surveyed. Over the study period the equity position of just over 60% of farms declined, although 55% of these had more than 80% equity in the business initially and were able to absorb a short term decline in equity caused by the drought. In addition, 9% of farms had levels of equity below 80% at the start of the investigation, but actually improved their equity position by the end of the study. Strong links were found between wheat yield and the business indicators. Mostly this was due to the crop dominant nature of the farm businesses where wheat was by far the main crop. However, farms that were able to capitalise on favourable conditions in other years were better placed to enhance or recover their financial position. Farms that cropped a higher proportion of their farm area were at an advantage. Structural indicators, including the percentage of area cropped, had a small but significant effect on the debt to income ratio, the return on capital and operating profit. Farm diversity also favourably lessened the debt to income ratio. Other factors, including farm size did not influence the outcome of any business indicator. Farms that remained resilient, despite the serious droughts were those that cropped more than 50% of their farm area, were prudent in their expenditure, maintained some enterprise diversity and often generated wheat yields in each year that were near the yield potential for that year.     

车用42V电气系统的结构特点及对整车结构的影响分析

分析了提升汽车电源电压从14V到42V的技术原因。重点介绍了组成汽车42V电气系统的结构特点和对整车结构的影响。也指出了发展42V电气系统在技术与市场上存在的困难。     

基于CMAC神经网络的自适应渠道输水自动控制研究

介绍了小脑模型神经网络CMAC的原理及基于CMAC的自动控制方法。在渠道输水控制技术的基础上,依据CMAC神经网络学习速度快、能够表达复杂非线性关系、适合于适时控制的特点,提出了基于CMAC的渠道输水控制模型。仿真结果表明,基于CMAC的渠道输水控制,算法简单方便,具有实时性、稳定性和较强的鲁棒性,控制效果较为理想。     

生活污水厌氧消化出水后处理技术研究进展

本文综述了生活污水厌氧消化系统相关后处理技术的技术特点和研究进展,着重分析了好氧处理、稳定塘处理及土地处理三种后处理技术方法,简要介绍了户用一体化装置的研究及应用状况。     

Livestock water productivity in mixed crop–livestock farming systems of the Blue Nile basin: Assessing variability and prospects for improvement

Water scarcity is a major factor limiting food production. Improving Livestock Water Productivity (LWP) is one of the approaches to address those problems. LWP is defined as the ratio of livestock’s beneficial outputs and services to water depleted in their production. Increasing LWP can help achieve more production per unit of water depleted. In this study we assess the spatial variability of LWP in three farming systems (rice-based, millet-based and barley-based) of the Gumera watershed in the highlands of the Blue Nile basin, Ethiopia. We collected data on land use, livestock management and climatic variables using focused group discussions, field observation and secondary data. We estimated the water depleted by evapotranspiration (ET) and beneficial animal products and services and then calculated LWP. Our results suggest that LWP is comparable with crop water productivity at watershed scales. Variability of LWP across farming systems of the Gumera watershed was apparent and this can be explained by farmers’ livelihood strategies and prevailing biophysical conditions. In view of the results there are opportunities to improve LWP: improved feed sourcing, enhancing livestock productivity and multiple livestock use strategies can help make animal production more water productive. Attempts to improve agricultural water productivity, at system scale, must recognize differences among systems and optimize resources use by system components.     

邓肯-张非线性模型研究及其在ANSYS中的实现

对工程领域使用广泛的邓肯-张非线性本构模型进行了研究,总结了国内外的研究现状及理论成果,针对其无法判定因结压力降低时的加载情况,提出了相应的变形模量的计算方法,同时考虑中主应力、土体抗拉强度的影响对模型进行了修正。利用APDL编写程序实现了ANSYS的材料本构模型的二次开发,运用重启动方法实现单元应力修正后数据重写入数据库,通过试验模拟对比分析验证了模型的适用性。     

秸秆旋埋还田后空间分布效果仿真与试验

对传统旋耕机(TR)、秸秆旋埋还田机(SR)和深松+秸秆旋埋还田机(SSR)进行了秸秆还田离散元仿真和田间试验对比。通过设计的秸秆三维坐标测量装置对秸秆在土壤中的空间坐标进行了测量,并在三维绘图软件中还原了秸秆在土壤中的空间状态,及秸秆在三维图中量化及可视化显示。对取样立方体进行分层、横向及纵向划分等探究了秸秆在土壤中垂直分布及水平分布的均匀性。利用离散元软件建立了相应的仿真模型,并与田间试验设定了相同的作业参数,在仿真作业完成后,通过设置不同尺寸的Geometry Bin计算区域内秸秆数量,并分别对应实际田间作业的分层、横向和纵向划分。在分层处理中,仿真与实测结果表明,SR和SSR埋入土壤中的秸秆量都明显大于TR,尤其是埋入土壤下层的秸秆量均是TR的数倍。TR、SR和SSR作业后各层秸秆占比仿真值和实测值的变异系数均呈递减趋势,其中SSR的变异系数最小,分别为28. 8%和28. 7%。3种耕作装备下仿真值与实测值的变异系数相差不大,平均误差为9. 6%。横向和纵向划分中,TR、SR和SSR的各区域秸秆占比仿真值和实测值的变异系数无绝对规律,SSR的变异系数均最小。离散元仿真和田间试验结果表明,SSR秸秆还田后,秸秆在土壤中垂直分布和水平分布的均匀性均最优。离散元仿真较好地拟合了实际田间作业后秸秆的空间分布状态,相对误差在可接受范围内。