Prediction of aeration performance of paddle wheel aerators

Aeration experiments were conducted in brick masonry rectangular tanks of dimensions 2.9×2.9×1.6 and 5.9×2.9×1.6 m to study the effect of geometric and dynamic variables on aeration process based on dimension analysis. Non-dimensional numbers relating to standard aeration efficiency (SAE), effective power (P) and theoretical power per unit volume (P/V) termed as SAE′, Ne and X, respectively, are proposed. An optimal geometric similarity of various linear dimensions was established. It has been established that neither the Reynolds criterion nor the Froude criterion is singularly valid to simulate either SAE′ or Ne, simultaneously for different sizes of aerators, even though they are geometrically similar. Occurrence of scale effects due to the Reynolds and the Froude laws of similitude on both SAE′ and Ne are also evaluated. Simulation equations uniquely correlating SAE′, Ne and X were developed which can predict the aeration performance of paddle wheel aerators having the optimised geometric dimensions as established.     

车辆转向轮前束和外倾角对轮胎磨耗的影响

分析了车辆导向轮侧滑量在允许值范围仍出现轮胎异常磨耗的原因，并讨论了前轮检测中应引起重视的几个问题．     

Determining sample size for assessing species composition in grassland 1

Species composition is measured in grasslands for a variety of reasons. Commonly, observations are made using the wheel‐point apparatus. However, the problem of determining optimum sample size has not yet been satisfactorily resolved. In this study the wheel‐point apparatus was used to record 2 000 observations in each of a range of sample sites. A random number generator was used to select 30 sets of samples of size N (number of point‐observations) from each sample site. A measure of similarity for each sample with every other in a set was calculated to establish the variation that may be expected for that sample size. The Richards function was used to determine the sample size (number of point‐observations) required to retrieve a minimum level of precision. It is proposed that 100 point‐observations are sufficient for coarse management scale investigations, 200 for monitoring programmes and 300 for detailed scientific studies.     

Determining the effect of tree size,bark-wood bond strength and tree form on the productivity of an excavator-based harvester in Acacia mearnsii in the KwaZulu-Natal forestry region of South Africa

The aim of this study was to determine the effect of tree size, bark-wood bond strength and tree form on the productivity of cut-to-length harvesting of Acacia mearnsii, using an excavator-based harvester with a SP Maskiner harvester head in the KwaZulu-Natal forestry region of South Africa. Tree diameter and height measurements were used to determine individual tree volumes, after which the trees were classified into different bark-wood bond strength and tree-form classes. Time studies were carried out to determine harvester productivity. The results showed that tree size plays a crucial role in the productivity of the harvester, but bark-wood bond strength and tree form also influence productivity. The harvester productivity varied from 5.5 m³ per productive machine hour (PMH) in 0.05 m³ trees to 16.9 m³ PMH^?1 in 0.25 m³ trees The bark-wood bond strength did not influence harvester productivity when handling small trees of less than 0.1 m³. In small trees, the productivity of the harvester was also not affected by different form classes, but as tree size increased, there was greater productivity variation between the different form classes.     

实木装饰条加工机械设计

装饰条加工机械是一种多功能木制品加工机械.在生产过程中,它能根据装饰条或板的形状、规格和表面加工精度的要求,更换相应刀具和从动滚轮,调整部分技术参数,从而加工出各种形状和规格的室内装饰材料.文章主要介绍该机械的结构设计、工作原理及具体操作方法等.     

4YB-Ⅰ型甘蓝收获机的总体设计

为实现我国甘蓝收获的机械化,降低农民的劳动强度,本设计从实际需要出发,应用Pro/E软件,对4YB-I型甘蓝收获机整机及主要部件进行了三维实体设计,并对其主要工作部件收集机构、圆盘割刀、压顶导正机构、提升机构等进行了设计计算,确定了主要技术参数.模拟结果表明:该收获机可实现对整棵甘蓝的收集、拔取、切根及运输.     

联合收割机季前准备与试运行

介绍了联合收割机季前的准备调整和试运行方法,以期为联合收割机的正确使用提供参考。     

新疆玉米膜上精密穴播技术现状与发展

针对新疆现有的玉米精密播种技术,综合分析了玉米精密播种技术的研究现状,介绍了不同类型播种装置的结构和工作原理及其优缺点,指出玉米膜上精密穴播技术存在的问题和发展方向。研究结果对提高玉米精密播种技术水平有一定参考价值。     

9265型自走式矮秆青贮饲料收获机研究

针对我国青贮饲料使用现状,分析了矮秆青贮作物的使用价值与前景。鉴于国内矮秆青贮作物机械化程度较为落后,以国内具有代表性的9265型矮秆割台青贮饲料收获机为例,分析研究了该机型的整机和主要工作部件的结构设计以及工作原理,并通过正交试验找出影响该机型喂入性能的主要因素,确定矮秆青贮饲料收获机型的发展方向,为后续矮秆青贮作物收获机械的研究设计提供参考。     

基于Cult3D的牧草收割机切割组件的虚拟装配

为实现牧草收割机的网络交互展示,方便收割机用户对设备的了解和维修,通过对牧草收割机的结构分析,用Pro/E建模工具进行建模,在切割组件三维模型的基础上,基于Cult3D平台,通过对其各元件触发事件和动作等参数的设置,实现在网上交互、动态地展示切割组件的切割原理以及各元件的组装方法和步骤,实现了牧草收割机切割组件网络环境下的虚拟装配。