基于模式搜索的轮胎纵向刚度估计方法

提出了一种含有两个参数的轮胎纵向力模型,并通过该模型利用基于模式搜索的最小二乘法对轮胎的纵向刚度和滚动半径进行了动态估计。仿真证明了该算法的可行性。将该算法应用于车辆的实际试验数据,结果证明轮胎的压力与轮胎纵向刚度近似成反比。     

耕播机三点悬挂连接机构有效间距确定方法

以分置式一机三用型耕播机为研究对象,设计三点悬挂连接机构.从分置式耕播机连接机构的设计原则出发,分析了单机连接机构的有效间距.从机组纵向稳定性储备利用系数和爬坡稳定性系数分析了耕整联合作业机组的抗倾翻能力,确定连接机构有效尺寸的最大值为41 cm;通过分析旋耕刀的运动状态、土块的被抛位置和初速度,并对其进行计算和试验,确定连接机构有效尺寸的最小值为19 cm.     

棘轮齿轮式水稻钵苗移栽纵向送秧机构设计与试验

为了研究棘轮齿轮式水稻钵苗移栽纵向送秧机构的可行性,分析了水稻钵苗移栽纵向送秧机构的工作原理和棘轮齿轮式机构的传动特性,针对高速回转式水稻钵苗移栽机送秧机构需满足传动平稳、传动比精确、工作可靠性好、作业中没有积累误差、振动和噪声小的特点,设计棘轮齿轮式水稻钵苗移栽纵向送秧机构,对其结构设计中的重要几何参数建立了数学模型,进行了优化,采用CAD/CAE软件建立虚拟模型。对该机构进行了台架试验,结果表明,该种传动形式的纵向送秧机构能够满足高速回转式钵苗移栽机的工作要求,为研发高速回转式钵苗移栽机纵向送秧机构提供了理论和实践依据。     

鸡舍纵向通风

该文论述鸡舍纵向通风的机理、实践效果及实现鸡舍纵向通风的技术关键。     

清选装置电气控制系统设计

自行研制了纵轴流风筛式清选装置试验台,并对清选装置的电气控制系统进行了设计研究,配有扭矩仪和风速传感器等硬件设备,采用了计算机数据采集与监控系统,可实现数据的实时采集,可以对参数进行实时调节控制,控制面板简洁规范,操作简便。该设计提高了清选装置试验台的操作简便性和试验数据测量的准确性,对于指导清选装置的设计制造具有重要意义。     

Signals of summer drought in crown condition data from the German Level I network

Crown transparency estimates of Scots pine, Norway spruce, common beech, pedunculate and sessile oak, annually surveyed between 1990 and 2004 within a grid over Germany, provide a suitable response variable to study drought effects on forest trees. Major climatic factors, available on a monthly basis as plot-specifically interpolated values and parameters of site and stand conditions, biotic and other relevant factors were used as predictors in different cross- and length-sectional, and longitudinal models. Stand age is a considerable and most constant driver of crown transparency in all species. Pine, spruce and beech responded—mainly with a delay of 1 year—with some foliar loss in areas where there was a surplus of temperature after the generally hot and dry summer of 2003. Parallel time-series analyses delivered species-specific geographic large-scale patterns with delayed or recent precipitation deficits or temperature surpluses. Even if beech is partly responding in current years with leaf loss towards precipitation surpluses, defoliation is especially high 1 year after hot summers, partly a result of high seed sets after such summers. Crown condition of oak responds in dry and warm areas according to the drought stress hypothesis, however, in cool and wet mountainous ranges oak responds after wet summers with higher defoliation. Longitudinal approaches revealed for all 4-tree species significant relationships between crown condition and deviations from the long-term means of temperature, precipitation but also global radiation and wind speed. Results do not always match the drought stress hypothesis, however, this is not to expect considering the heterogeneous site, stand and climatic conditions across Germany. Complex interactions of climatic and biotic factors also impede simple relationships. Soil-related clusters reveal higher sensitivity of spruce and beech towards climatic drought factors on more acid soils with thin humus layers. Also clusters constructed from plot-specific courses of defoliation reveal groups with rather closer relationships like a group of pine plots in the Oberpfalz, which seems to be especially sensitive to summer drought.     

纵向刨切生产薄木中刀具与产品质量的关系

本文探讨了纵向刨切机生产薄木过程中刀具的材料、形状及刀具与压尺的相对位置等因素对产品质量的影响。     

竹材打片刀国产化初步研制及几点看法

引进竹材打片刀耐用度低的主要原因是粗大片状马氏体组织造成的。竹材打片刀的工作条件要求刀具材料在具有高硬度和高耐磨性的同时,还具有更大些的韧性。国产化竹材打片刀的研制,主要从刀具材料的金相组织、硬度与韧性的适当配合以及刀具楔角等三个方面加以考虑和控制。初步试制结果表明,用轴承钢(GCr15)制造的刀片比进口刀片更适用于本国的毛竹加工。     

The incidence of calf morbidity and mortality due to vector-borne infections in smallholder dairy farms in Kwale District, Kenya

An observational longitudinal study was carried out on 92 randomly selected smallholder farms in two coastal lowland zones of Kwale District in Kenya between December 1997 and November 1999. The objective was to estimate the incidence of the main vector-transmitted diseases in pre-weaned calves. From an initial 41 pure or cross-bred Bos taurus calves which were less than 2 months and whose birth and disease histories were known, study calves were recruited progressively and monitored until they were weaned at around 146 days. Overall, 130 calves in 67 farms were monitored and these contributed a total risk period of 30,062 days.

Disease parameters were analysed and compared as true annual and age-specific incidence rates. The incidences of East Coast fever (ECF) (23.1%) and trypanosomosis (29.1%) were the highest among the vector-borne diseases. The corresponding mortality incidence rates of ECF and trypanosomosis were 10.9 and 3.6%, respectively. The annual incidence rates of anaplasmosis and babesiosis were 10.9 and 1.2%, respectively. There was no mortality arising specifically from anaplasmosis or babesiosis. Analysis of survival times to natural infection indicated that the field challenge resulting to cases of trypanosomosis was much higher compared to the risk of either ECF or anaplasmosis. It was concluded that these vector-borne diseases constrain production of replacement stock in this coastal lowlands region of Kenya.     

A longitudinal study to identify constraints to dairy cattle health and production in rural smallholder communities in Northern Vietnam

The objective of the study was to investigate constraints to dairy cattle health and production in rural smallholder communities in northern Vietnam, one of the target areas of the Vietnam government's dairy development programme. A total of 99 dairy farms (11 per commune) were recruited from 9 of 32 communes in Ba Vi District, using random two-stage cluster sampling. After the initial questionnaire interviews were conducted, farms were visited at three monthly intervals over a period of 1 year. Information on several health and production parameters relating to the study cattle was collected. Using multiple indicator modelling, it was found that Fasciola infestation, farmers who had been involved in dairying for longer (not indicative of better management skills), larger herd size, and cattle being kept in a shed were linked to reduced reproductive performances.