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81.
分析了拖拉机液压悬挂装置的组成及工作原理,建立了系统的数学模型;并应用MATLAB软件对系统进行了稳定性分析和仿真,效果良好.建模仿真技术是研究机组系统整体的最佳设计(匹配)、最佳使用和提高机组效益的有效途径,为解决拖拉机机组系统分析与综合有效途径提供了参考依据. 相似文献
82.
基于UG平台的直齿圆锥齿轮的三维精确建模 总被引:6,自引:0,他引:6
直齿圆锥齿轮是现代机械中应用最为广泛的一种传动机构。它可以用来传递空间两轴之间的运动和动力,而且传动准确、平稳、机械效率高。为此,介绍了一个在UG平台上建立直齿圆锥齿轮三维模型的新方法,该方法符合《机械原理》一书对直齿圆锥齿轮齿廓线的定义.实现了精确建模的目的。最后通过一个简单的实例。进一步阐明了该方法的实现过程。 相似文献
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对前期提出的三平移并联机构2P4R(Pa)-PR(Pa)R进行了动力学分析及其性能优化。首先,基于该机构的符号式位置正解,直接求得其各杆件(角)速度和(角)加速度;然后,采用基于虚功原理的序单开链法,对该机构进行动力学建模,并通过比较3个驱动力的理论计算值与仿真结果,验证了动力学建模的正确性;进一步,以杆件长度和质量参数作为设计变量,以可达工作空间和能量传递效率两种性能指标为目标函数,对该机构进行运动学和动力学性能的二级递进优化,得到机构在上述两种性能指标下的最优解,使机构可达工作空间性能指标提高56.2%,全局能量传通效率性能指标提高63.6%,为机构设计与样机研制奠定了基础。 相似文献
88.
Field and pot experiments were conducted to evaluate the effect of co-cultivation and crop rotation on the growth and corm rot disease of gladiolus (Gladiolus grandiflorus sect. Blandus) cv. Aarti caused by Fusarium oxysporum f.sp. gladioli (Massey) Snyd. and Hans. In the field experiment, gladiolus was co-cultivated with 10 agricultural/horticultural crops viz. Allium cepa L., Brassica campestris L., Capsicum annuum L., Eruca sativa Mill., Helianthus annuus L., Tagetes erectus L., Zea mays L., Vinca rosea L. and Rosa indica L., in a soil infested with F. oxysporum. All the crops except V. rosea and R. indica reduced disease incidence. The effect of H. annuus and T. erectus was significant and more pronounced than other co-cultivated crops. In general, root and shoot dry biomass, corm fresh weight, number of cormlets and number of flowers per spike decreased as compared to the un-inoculated monoculture gladiolus treatment (negative control) but these parameters enhanced as compared to the F. oxysporum inoculated monoculture gladiolus treatment (positive control). In a pot experiment, all the crops of the field experiment except V. rosea and R. indica were sown in rotation with gladiolus. Pot grown plants of different species were harvested at maturity and the soil was inoculated with F. oxysporum. Gladiolus was cultivated 1 week after inoculation. Disease incidence was significantly suppressed in all the treatments ranging from 29% to 53%. The highest suppression of disease incidence was recorded in T. erectus (53%) followed by B. campestris (49%). The effect of preceding crops on various vegetative parameters was similar in the pot experiment to that of the field experiment. The present study suggests that corm rot disease of gladiolus can be managed by mixed cropping of H. annuus and T. erectus or cultivation of T. erectus and B. campestris in rotation. 相似文献
89.
Amare Haileslassie Don Peden Solomon Gebreselassie Tilahun Amede Katrien Descheemaeker 《Agricultural Systems》2009,102(1-3):33-40
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. 相似文献
90.
Kullapapruk Piewthongngam Supachai Pathumnakul Kanchana Setthanan 《Agricultural Systems》2009,102(1-3):58-66
The poorly integrated cane supply planning between mills and cane growers in the Northeast of Thailand generates an excess of cane supplies that exceeds the mills’ capacity during the peak of harvest season. Each grower individually determines his/her cultivation plan by selecting planting dates and cultivars based on one’s own preference without taking into account the individual mill’s capacity and other growers’ plans. This situation causes most sugarcane grown in this area to reach its mature stage at the same period. In this study, we propose a framework of cultivation planning to cope with the problem. The focus of the cultivation plan is a long-term plan to determine the cultivation time, the cultivar selection and the corresponding prospective harvesting time window for each field such that overall sugar production is optimized.The crop growth model and a mathematical model are employed for yield simulation and optimization task. The crop growth model enables decision-makers to visualize cane production of each individual field at different dates with different cultivars and allow decision-makers to apply the mathematical programming to cultivation planning. The suggested framework has the potential to increase sugar production by 23% when compared to the traditional method. 相似文献