Calculating the contact area of trailer tyres in the field

The spectacular increase in the weight of self-propelled harvesters since the early 1980s also applies to trailed implements such as slurry spreaders, compost spreaders, cutter-blowers and general farm trailers. With axle loads exceeding 10 tonnes/axle (tandem 20 tonnes, tridem 27 tonnes), risks of severe compaction can now be expected, not only in field crops but also in grassland. Calculation tables for accurately evaluating contact surfaces of transport tyre, given their properties, load and inflation pressure, are insufficient at the present time. Equations for traction tyres are not suitable for trailer tyres.To overcome this deficiency, contact areas in the field were recorded on 19 sites, from soft to hard surfaces, using 24 different trailer tyres, with varying loads and inflation pressures. The regression calculations for evaluating the contact area apply to a total of 143 measurements.The dimensions of the tyre (width × unladen diameter), the load on the wheel and the inflation pressure are all highly significant variables for evaluation of the soil contact area. Considering the average residual standard deviation for each regression calculation, the best approximations are achieved by taking into account the tyre structure (cross-ply and radial), the width of tyre for cross-ply tyres and the type of tyre, in the case of a radial tyres (low profile or terra profile).Moreover, contrary to expectations, observations show that with low levels of load, reducing inflation pressure can also reduce the contact area.As regards soil hardness, observations show that there is no direct link between a hard soil and a reduced contact area; this relationship does not appear to be linear. The calculations are considered to be reliable on semi-firm to firm soil, frequently found on temporary grassland or natural grassland (penetration resistance 6.5–25.0 MPa).     

冀东冬麦区雀麦的田间识别 发生规律及其化学防除技术的初步研究

通过田间观察对冀东冬麦区雀麦的形态特征进行了系统完整的描述,修正和完善了文献记载的不足,重点突出了直观性,使农民能够在麦田里容易地识别出雀麦。通过定期田间调查,明确了雀麦在冀东冬麦区的发生规律：在冀东冬麦区雀麦属越年生杂草,绝大部分在秋季出苗,占发生总量的97%以上;雀麦分蘖力强,单株平均分蘖达10.6个。同时进行了啶磺草胺7.5%WG 3个剂量处理（135、180、360 g/hm2）对雀麦的田间防除药效试验,结果表明：啶磺草胺7.5%WG是目前防除麦田雀麦的理想除草剂,春季在雀麦7叶期前用啶磺草胺7.5%WG 135～180 g/hm2＋专用助剂225 mL/hm2,对雀麦鲜重防效达97%以上,对混发的荠菜和播娘蒿也有较好的兼治效果,并且对小麦安全。     

A highly polymorphic caprine keratin-associated protein gene identified and its effect on cashmere traits

Five keratin-associated protein 6 genes (KRTAP6) have been identified in sheep and variation in some KRTAP6 has been associated with wool fiber diameter-related traits, but none of these homologues have been identified in goats. In this study, we reported the identification of the sheep KRTAP6-5 homologue on goat chromosome 1 and polymerase chain reaction (PCR)-single strand conformation polymorphism analysis in 300 Longdong cashmere goats revealed the existence of 12 variant sequences. Both coding region and 3′UTR of the putative caprine KRTAP6-5 displayed a biggest sequence similarity to ovine KRTAP6-5 gene. This suggested that the gene represents caprine KRTAP6-5 sequences, and these sequences composed 23 genotypes, which was the most polymorphism gene in KRTAPs that have been studied. Among these sequences, 15 nucleotide substitutions and a 24-bp insertion/detection were identified. Variation in goat KRTAP6-5 was associated with variation in mean-fiber diameter, suggesting that KRTAP6-5 is worthy of further study in the context of variation in cashmere traits.     

Analysis of regional variation of height growth and slenderness in populations of six urban tree species using a quantile regression approach

Inventory data of six urban tree species from seven cities across Germany were used to model regional variation of height growth, allometric scaling, and slenderness over a wide range of size and age using a quantile regression approach. Variation within and between species and cities was large. Height did not reach an asymptote but declined at higher ages, presumably because of reduction cuts. Allometric scaling and slenderness varied with wind climate, modulus of elasticity, and coefficient of drag. Our data do not support the use of a threshold value of slenderness in tree risk assessment.     

基于人机界面优化目的的森林灭火手泵操作力研究

为了优化森林灭火手泵的人机操作界面,提高操作的舒适性和效率,该文通过最大操作力的测量,研究了森林灭火手泵的握持直径、握持长度和握持姿势对操作者操作力的影响。结果表明:①手泵握持直径、握持长度以及握持姿势对操作力的影响都很显著。② 手泵合理握持长度为450～800 mm,握持直径为32～35 mm,内筒直径取144 mm,握持姿势以采用出水方向偏离水平面向上为宜。      

林分平均胸径100倍圆法测定每公顷断面积的理论初探(之二)--误差分析与修正系数

通过对100Dg圆公式含义的分析,对影响林分断面积精度的2个主要因子:样地株数密度与林分平均胸径估测值进行了误差分析与探讨,提出了样地株数密度估计林分株数密度采用典型选样,林分平均胸径估测值采用目测法等相应解决办法。其中,当目测值有偏差时采用修正系数可使100Dg圆的可靠性进行了理论上的探讨。     

变换半群的完全正则性和超富足性

令M是有限集合,A是M的非空子集,TM是M上的全变换半群.定义FM={f∈TM|f(A)A}显然,FM是TM的子半群.主要刻画了FM的完全正则元和超富足元的性质,同时描述了FM的完全正则性和超富足性的条件.     

绵羊KAP1.1基因多态性与毛纤维直径的相关性分析

以768只中国美利奴羊(新疆军垦型)为材料,采用测序和PCR技术分析KAP1.1(B2A)基因单核苷酸多态性及其与羊毛纤维直径的相关性。结果表明:中国美利奴羊(新疆军垦型)KAP1.1基因存在30个碱基的插入/缺失和6种基因型,分别为(341 bp)AA基因型、(311 bp)BB基因型、(281 bp)CC基因型、(341 bp/311 bp)AB基因型、(341 bp/281 bp)AC基因型和(311 bp/281 bp)BC基因型。AA、BC、AC、AB和CC基因型间的毛卷曲度、细度离散、毛长、污毛重、净毛率和密度差异不显著(P>0.05),而BB基因型羊只的平均纤维直径显著小于AA、BC、AC、AB和CC基因型羊只的平均纤维直径(P<0.05)。以上结果表明,KAP1.1基因可作为绵羊毛纤维直径的主要候选基因之一,BB基因型可作为分子标记用于预测绵羊毛纤维直径。     

Effects of Infill Walls in Frame Structures under Frequent Earthquake:Revelation from Wenchuan Earthquake

Based on a three-story RC frame, the analysis of the structure with various layouts of infill walls under frequent earthquake was conducted. The results indicate that when the infill walls and their different layouts are incorporated into the structural model, the seismic performance, such as dynamic properties, characteristics of regularity, and internal force distributions would change significantly. It should be also mentioned that because of the constraint of infill walls, the sum of moments at column ends is much larger than that at beam ends at the frame column-beam joints. It is suggested that infill walls should be adequately considered in the mechanical models during seismic analysis.     

基于机器视觉的蒜头最大横切面直径分级方法

针对中国蒜头分选率和分选精度较低而影响其商品价值等现状,设计了一套基于机器视觉技术的大蒜蒜头分选系统,以蒜头最大横切面直径作为分级标准,利用VC6.0编程实现上述分级模型的算法。试验选择3 2 0个金乡蒜头样本对其进行测试,该装置对蒜头总体筛选精度达到9 0.9 3 7 5%。试验结果表明:利用机器视觉技术可以对大蒜蒜头进行分级。