4H-2型花生收获机挖掘部件载荷试验与分析

4H-2型花生收获机是采用新原理研制成功的一种花生收获机械，以此花生收获机的挖掘部件作为试验对象，通过载荷测试，采集挖掘部件工作时圆周力、向心力和扭矩载荷变化的时域曲线，在此基础上，进行了4H-2型花生收获机的载荷自功率频谱分析。试验结果证明，该花生收获机以反平行四边形机构组成的传动系统很好地实现了机器工作时侧向载荷的平衡，而且频率集中、工作稳定。     

FEM analysis of subsoil reaction on heavy wheel loads with emphasis on soil preconsolidation stress and cohesion

Heavy sugarbeet harvesters may compact subsoil. But it is very difficult to study this by field experiments that resemble agricultural practice. Therefore, an analysis was made by a finite element method (FEM) for a relevant calcaric fluvial soil profile, the mechanical properties of which were largely known. Measuring data of this Lobith loam soil includes preconsolidation stress, compression index and swelling index, all as a function of depth. Using these three types of soil parameters calculations have been done for tyre sizes, inflation pressures and wheel loads that occur with heaviest sugarbeet harvesters available on the European market in 1999. Because no values on soil cohesion were available, the calculations were done for several cohesion levels. The results include the detection of regions with Mohr–Coulomb plasticity and regions with cap plasticity (compaction hardening). For the soil studied—a typical soil strength profile for arable land with ploughpan in the Netherlands in the autumn of 1977—all studied combinations of wheel load and inflation pressure did not induce compaction in and below the ploughpan. The size of the region with Mohr–Coulomb plasticity decreased with increasing cohesion. It appeared from a sensitivity analysis that, although soil modelling may use a great number of soil parameters, the most important parameters seem to be: preconsolidation stress and cohesion. There is an urgent need for data of these parameters that are measured on a great range of subsoils and subsoil conditions.     

联合收割机跨区机收发展分析

阐述我国联合收割机跨区机收的发展历程，分析了联合收割机跨区机收的主要贡献、发展动因；提出了联合收割机跨区机收正处于由政府主导向市场主导转换时期，要充分发挥政府部门市场监管和信息服务的职能，推动联合收割机跨区机收快速、健康发展，并给出了有关政策建议。     

玉米收获机械化技术现状与发展趋势

玉米是中国种植面积第二大的粮食作物,在国民经济发展中具有举足轻重的地位。现阶段玉米种植机械化技术已趋于成熟,实现玉米收获机械化具有十分重要的意义。     

4ZBL-2背负式籽瓜联合收获机的设计

半机械化收获籽瓜需耗费大量的劳动力,整个生产过程劳动强度大,劳动效率低,收获成本高。为解决这个问题设计了4ZBL-2背负式籽瓜联合收获机,并对样机的工作性能进行了试验验证,结果表明该机可满足设计要求,可在籽瓜自然状态下一次完成籽瓜的集条、捡拾、脱粒及装袋等作业。该项技术填补了国内籽瓜联合收获的空白,并受到当地农户好评。     

Adaptive tree bucking using group-guiding of harvesters: A simulation approach

Abstract

The objective of this study was to test harvester group-guiding methods by comparing how the total log output distribution of independent harvesters differs from the total log output distribution of group-guided harvesters. In this simulation study four harvesters worked in their own stands in the same region for an identical target, given by a sawmill. Group-guiding was done by utilizing other harvesters’ bucking outcomes to fulfil the target log distribution better. Harvesters were combined to form a group in an adapting phase where a new price list was formed. For group-guiding, four different price list adapting methods were developed. There were five different simulations: four with adaptation and one reference simulation without adaptation. Apportionment degree and log/pulpwood proportions were calculated to compare the difference between the methods and reference simulation. With group-guiding, by adapting the price list harvesters reached the target distribution better than working independently. The best group-guiding method fulfilled the target distribution almost 9% better than independently working harvesters. However, the pulpwood proportion increased as a result of using the group-guided method.     

Comparison of two harvesting systems for the production of forest biomass from the thinning of Picea abies plantations

Abstract

This study compares two principally different harvesting systems used for the thinning of Norway spruce [Picea abies (L.) Karst.] plantations in the Alps. The first system was whole-tree harvesting (WTH), producing only whole-tree chips for energy purposes. This system minimizes the production costs by simplifying the harvesting process. The other system was cut-to-length (CTL) mechanical harvesting with an excavator-based harvester. This system maximizes value recovery by producing both short sawlogs and quality fuel chips. Trials were conducted on two similar sites in the Dolomites, in northern Italy, and demonstrated that the CTL system resulted in slightly higher harvesting costs, and also higher revenue. The price differences between the different products determine which system offers the best economic results. If the delivered price of sawlogs does not exceed [euro]25 t^?1, WTH and CTL harvesting offer very similar economic performances, and become profitable only if the delivered price of raw chip wood exceeds [euro]40 t^?1. If the delivered price of sawlogs increases to [euro]50 t^?1, the mechanized CTL system always becomes preferable, and it will turn some profits when the price of raw biomass exceeds [euro]35 t^?1. The CTL system is less sensitive to long extraction and transport distances than the WTH system.     

道者,自然之理——浅析珠三角绿道网规划建设的价值

通过对珠三角绿道网规划的解读,阐述了珠三角绿道网概念的由来,以及绿道在自然理念的延伸、人文生态价值的演绎和多功能并存等三方面的价值塑造,揭示了绿道独具中国"道者,自然之理"之大智慧,以及引领理想城市生活、弘扬新广东精神等方面的精神内涵。     

A comparison between excavator-based harvester productivity in coppiced and planted Eucalyptus grandis compartments in KwaZulu-Natal,South Africa

Due to the labour challenges in South Africa, mechanised forestry equipment has increasingly been required to operate in complex forest conditions – such as coppiced Eucalyptus compartments – where they have not operated before. For this reason, harvesters are either used in certain coppiced compartments with uncertain productivity expectations, or harvesters are not used in these compartments due to a lack of productivity knowledge. This research aimed to determine the influence of tree volume and tree form on the productivity of an excavator-based harvester in coppiced regrowth – with either double or single stems, or planted single stems – in Eucalyptus grandis pulpwood compartments. In addition, the stem felled first and the distance between stems were investigated for coppiced double stems. The stem felled first is whichever stem between the two coppiced double stems the harvester grabbed, felled and processed first. The tree volume was determined; thereafter the trees were classified into different form classes. The tree volume and the cycle time were used to determine productivity. The research results showed that planted trees had the highest productivity across all tree sizes, followed by coppiced single stems and then coppiced double stems. When harvesting a 0.2 m³ tree, the mean harvester productivity was 8.7 m³ per productive machine hour (PMH₀) in coppiced double stems, 13.8 m³ per PMH₀ in coppiced single stems and 16.1 m³ per PMH₀ in planted trees. In coppiced double stems the productivity was significantly influenced by the size of the stem felled first. In coppiced double stems the productivity was not significantly influenced by the distance between stems. The productivity for both coppiced single stems and coppiced double stems was significantly influenced by stem form. The poorly formed trees had lower productivity compared to the trees with good form.     

联合收割机前进速度电控系统设计

以联合收割机的电控系统为研究对象,针对其电控系统工作过程中出现的问题,提出了采用模糊自适应控制方法对其进行自适应控制。针对性地设计了基于单片机的自适应控制的速度控制装置,建立了自适应控制参考模型和模糊控制规则,试验表明,此设计完全满足联合收割机的电控系统设计要求,提高了工作效率。