Problems and prospects in the utilization of animal traction in semi-arid west Africa: evidence from Niger

The use of animal draft power for soil tillage has long been a major theme of agricultural development programmes in semi-arid West Africa. The rationale for animal traction utilization ranges from increasing agricultural productivity and income to relieving the drudgery in farm work. Yet, its adoption remains low and localized. Previous research has identified the conditions which favour the adoption of animal traction, but evidence on the potential benefits realizable from its use is mixed. The issue of how to improve the adoption and profitable utilization of animal traction in semi-arid West Africa remains an important topic given that mechanization of agriculture is inevitable. This paper uses data collected from villages in two different agroclimatic zones of Niger to demonstrate the regional variability of potential gains from animal traction. Production functions were estimated to determine the impact of animal traction use on area cultivated, labour input and aggregate yield. Multi-year partial budget streams were also estimated to evaluate the profitability of animal traction at each location. The results show that the use of animal traction did not have any significant impact on area cultivated, but increased the yields of sorghum (Sorghum bicolor (L.) Moench) and maize (Zea mays L.) by 12–15%. It increased labour input by 15 man-hha⁻¹ (man hours per hectare) in the dry agroclimatic zone, but reduced it by 50 man-h ha⁻¹ in the wet zone. Rates of return on animal traction investment ranged from −4 to 18% in the dry zone and from 14 to 58% in the wet zone. These results suggest that the impact of animal traction on agricultural production varies by region and depends on a broad set of agroecological and economic conditions. The absence of these conditions in marginal areas strictly limits potential utilization and profitability. On efficiency grounds, it is recommended that animal traction should be promoted only in areas where the climate, soil and economic conditions permit its intensive and profitable utilization.     

植物侧根对土壤牵引效应的计算机仿真

植物侧根对土壤增强和斜坡稳定具有重要作用，探讨根土作用的机械效应，建立侧根对土壤牵引效应模型为定量分析植被生态护坡奠定了基础。但多侧根对土壤的牵引效应较复杂且难于分析求解，使计算机仿真成为有效研究方法。该文分析了多侧根对土壤牵引效应的力学过程，建立了可用于计算机仿真的多侧根土壤牵引效应模型，并以MATLAB为工具，建立了仿真系统。通过计算机仿真，为复杂的多侧根土壤牵引效应的分析提供仿真平台，不仅可以求解计算模型，而且还能通过改变模型的输入变量和模型参数对模型的系统行为进行观察和预测。最后，以云南松侧根为例进行了仿真和试验测试，结果表明仿真模型具有一定的精度，所建立的仿真系统是有效的。     

拖拉机负载增扭/梭行换挡副变速器设计

动力换挡变速器换挡时动力不中断,且能够将复杂的换挡过程简化为按钮操作,在国外的拖拉机上已得到了广泛应用。为此,设计了一种新型的负载换挡行星齿轮副变速器,增加了原变速箱的挡位数,并实现了增扭负载换挡与梭行换挡。在分析了整体功能要求的基础上,确定了变速器的传动方案及结构,设计了副变速器液压控制系统,并对拖拉机各挡总传动比及理论车速进行了设计计算。同时,绘制了拖拉机牵引力和比油耗曲线,定义拖拉机牵引功率利用率和比油耗损失率用以评价拖拉机动力性和燃油经济性,并通过计算比较了改进前后拖拉机的动力性和燃油经济性情况。     

农用拖拉机牵引装置智能化测试与改进

为进一步提升农用拖拉机牵引装置的牵引效率和整机作业效率,针对其牵引装置进行智能化测试与改进研究。在全面理解农用拖拉机牵引装置工作机理及组件结构的基础上,建立牵引系统理论模型,并对相关联的悬挂装置同步改进,将驱动、牵引、悬挂形成闭环且协调的智能控制系统,进行试验测试。测试表明:选定牵引效率、燃油消耗率(经折合换算后)、悬挂稳定保持率和拖拉机整机作业效率4个变量参数,改进后的优化效果分别达到+2.8%、-3.7%、+12.1%和+15.8%,改进效果明显,可为农用拖拉机或其他动力驱动机械的类似部件优化提供思路和参考。     

推拿结合电针与单纯牵引治疗神经根型颈椎病的疗效观察

目的 研究推拿结合电针与单纯牵引治疗神经根型颈椎病的临床效果。方法 本次研究对象从湖北省中医院门诊两年来收治的颈椎病患者1 480例,遴选神经根型颈椎病患者200例,根据患者的治疗方案随机分为观察组（推拿联合电针治疗）和对照组（牵引治疗）各100例,观察对比两组患者治疗后的McGill疼痛指数和临床疗效。结果 观察组患者治疗后的PRI、VAS和PPI指数均显著低于对照组,且治疗总有效率以85.0%高于对照组59.0%,差异均有统计学意义（P<0.01）。结论 非手术疗法能有效缓解神经根型颈椎病患者的临床症状与体征,缓解周围组织压迫,但相比单纯治疗治疗,复合型治疗更能改善患者的疼痛感,效果也更显著。     

Use Of Traction During Magnetic Resonance Imaging Of Caudal Cervical Spondylomyelopathy ("Wobbler Syndrome") In The Dog

Cervical spondylomyelopathy or "wobbler syndrome" is a well-defined disorder of large-breed dogs, characterized by a compressive lesion affecting the cervical spinal cord that in many dogs may have a dynamic component. Determination of whether this dynamic component is present is important in the decision-making process as regards therapeutic intervention. Despite a significant risk of neurologic deterioration following myelography in some large dogs affected by wobbler syndrome, myelography is considered an essential part of the assessment, primarily as it allows assessment of whether a dynamic compression exists. This same neurologic deterioration is not apparent following magnetic resonance (MR) imaging; however, the use of MR imaging in the investigation of wobbler syndrome has thus far been limited by the inability to perform the traction studies required to ascertain whether a dynamic component to the spinal cord compression exists. This paper presents a technique of applying traction during MR imaging of the cervical spine to reduce a dynamic wobbler syndrome lesion.     

Self-balance Principles and Formulae for Axle-linked Cable-car

Even if pulled by single wire rope, the axle-linked cable-car can under some conditions automatically balance the eccentric moment caused by the carried loads. This paper expounds the self-balance principles of the four-wheel axle-linked cable car, deduces the associated formulae and analyzes the conditions for its application, laying a theoretic foundation for the design of transverse container cable car.     

基于VB 的电力机车牵引变压器分析软件开发

结合VB在界面设计和ANSYS,MATLAB 在二次开发方面的优势,开发了牵引变压器通用的分析软件.研发人员只需在软件界面中填写结构参数和电气参数,参数与ANSYS的APDL命令流中的变量参数已构成对应关系,通过VB调用ANSYS分析软件,建立牵引变压器的有限元模型,再通过多次调用不同物理场的分析程序和后处理程序,即可完成多物理场的分析与计算;通过VB调用MATLAB编写的复合短路阻抗计算程序,进行复合短路阻抗的计算,结果表明该分析软件避免了繁琐的命令流输入,可有效缩短产品设计周期,具有较大的工程应用价值.     

4U-1400FD型马铃薯联合收获机挖掘铲的参数优化

对4U-1400FD型马铃薯联合收获机的挖掘铲建立牵引阻力的数学模型,在此模型下分析挖掘铲的铲面倾角、作业速度、挖掘深度、铲体长度等因素对挖掘铲牵引阻力的影响.结果表明:挖掘铲参数的最佳组合为铲面倾角20°,铲体长度470 mm,铲宽1 400mm.通过田间试验,该挖掘铲的性能符合规定的指标.     

水稻高秆翻埋快腐还田机研究

为适应东北高寒地区水稻秸秆的机械化还田作业,降低还田作业的牵引阻力、加快秸秆的腐解,设计了具有滑切减阻特性的还田弯刀组成的高秆翻埋装置和使秸秆均匀平铺同时施入秸秆腐解剂的秸秆梳理-腐解剂施入装置。采用旋转正交设计方法设计试验方案,考察机器前进速度、刀辊转速、还田深度三个因素对牵引阻力的影响,建立牵引阻力模型,得到牵引阻力最优的参数组合：机器前进速度为1.4 m/s,刀滚转速210 r/min,还田深度为10 cm。影响阻力的因素主次顺序为：刀辊转速>机器前进速度>还田深度。