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991.
在小麦玉米轮作的前提下,分析了黄淮海地区小麦玉米轮作机械化作业模式;以10年承包年限为例,计算了购买农机具10年内作业总费用,将其与租用农机具作业费用进行比较,找到了自购农机具费用低于租赁农机具作业的最低土地面积。在自购农机具的基础上,以40hm^2土地为例计算开始盈利年限。结果表明:在一定范围内,只有通过提高粮食作物的生产规模和承包年限,才能通过土地流转切实提高农民的收入。 相似文献
992.
WZ-4型大蒜种植机械的概述及研究 总被引:2,自引:0,他引:2
介绍了大蒜的食用价值、需求及种植情况,体现农民对大蒜种植机械化与自动化的迫切需求。基于对国内外大蒜种植机型的研究,通过对比国内外大蒜种植机的结构、分析各种大蒜种植机种植时的优缺点、对大蒜外型的研究及各种试验,以有效解决大蒜的单粒取种及直立种植为目的,设计了一种大蒜种植机,并对大蒜种植机的关键部位及整机进行了仿真及试验。 相似文献
993.
The surface of silk is modified by a cationic reagent, N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride(CHTAC) in order
to enable the fibre to be dyed with superfine pigments by an exhaust process. The effects of cationization pretreatment conditions
such as the amount of cationic reagent, pH, treatment temperature and time on color yield are discussed in detail. The result
shows that the condition suitable for modification treatment is that the concentrationc of cationic reagent is 10 g/l, pH 8, liquor to goods ratio of 100:1 and 60°C for 30 min. The white index decreases with the increase of alkali of cationic
treatment. The crock fastness and wash fastness of silk dyed by pigment exhaust dyeing achieve 3–4 and 4 scale, respectively.
The treated silk fabrics still retain a soft handle because the bending rigidity B and hysteresis 2HB increase slightly after
cationization pretreatment and dyeing procedure. It has been demonstrated that properties of surface modified silk dyed with
superfine pigment by exhaust process are acceptable. 相似文献
994.
用表观收获指数和粒茎比不同的12个亲本配制11个组合,对其后代表观收获指数和粒茎比进行了研究。结果表明,大豆F_1代表观收获指数和粒茎比存在一定的杂种优势,其优势程度因组合而异。表观收获指数和粒茎比在F_2代均呈广泛分离,多数组合表现出超亲现象,其遗传属于数量性状遗传,无母体效应。F_2、F_3代,表观收获指数和粒茎比与中亲值相关显著。F_2代表观收获指数和粒茎比的广义遗传力分别平均为46.19%和37.47%。可将表观收获指数和粒茎比(?)入高产育种、高光效育种和株型育种的选择指标。 相似文献
995.
In this study, two biodegradable polymers, polycaprolactone (PCL) and polyvinyl alcohol (PVA) were used to fabricate nanofiber nonwovens (NFNs). Also, the silver nanoparticles (AgNPs) successfully reduced by using tea polyphenols (TP) and incorporated in the NFNs via electrospinning. The morphologies of the NFNs and AgNPs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. The PCL nanofibers and PVA nanofibers interweaved each other, and AgNPs with average diameter 1.53±0.15 nm were embedded in the PVA nanofibers. The properties of electrospun NFNs were characterized by pore property, swelling/weight loss, water contact angle, mechanical property, and antibacterial activity. The nanofibers cross-linked to each other forming the 3Dnetwork porous structure with diameter about 1-1.5 μm. Although the hydrophobic PCL was added in the hybrid NFNs, the NFNs still showed hydrophilic propriety, high swelling degree (i.e. swelling degree is 330 % for 48 h), and low weight loss (i.e. weight loss is 22.4 % for 48 h). Also, the hybrid PCL/PVA/AgNPs NFNs exhibited a suitable mechanical property for wound dressings (i.e. tensile strength is 4.27 MPa, and breaking elongation is 88 %). Moreover, the hybrid NFNs effectively inhibited growth of Escherichia coli and Staphylococcus aureus. In summary, this PCL/PVA/AgNPs NFNs may provide a promising candidate for accelerating wound healing. 相似文献
996.
机械弹性车轮提高轮胎耐磨性和抓地性分析 总被引:5,自引:5,他引:0
为提高轮胎接地性能,对新型机械弹性车轮垂直静态接地特性进行了研究。通过对车轮结构和承载方式进行分析,分别建立了基于Timoshenko圆形梁的车轮外圈弹性圆环模型和基于连续辐板的铰链组模型,并通过非线性有限元法和试验进行了验证。根据所建立的非线性有限元模型对机械弹性车轮和子午线充气轮胎的接地特性进行了对比研究,结果表明机械弹性车轮通过悬毂式承载控制车轮外圈变形,没有胎肩处的应力集中。在载荷为5 000 N时,机械弹性车轮和充气轮胎接地印迹中心0.14 m×0.265 m矩形区域内的接地压力偏度值分别为0.424和0.536 MPa。机械弹性车轮有效降低了接地压力偏度值,改善了轮胎接地的均匀性,提高了车轮耐磨损性能和抓地性能,研究为车轮性能优化提供了参考。 相似文献
997.
Purpose
Hydroxyl ion release by maize (Zea mays L.) roots under acidic conditions was investigated with a view to develop a bioremediation method for ameliorating acid soils in tropical and subtropical regions.Materials and methods
Two hydroponic culture experiments and one pot experiment were conducted: pH, nitrogen state, and rhizobox condition, which investigated the effects of different nitrogen forms on hydroxyl release by maize roots under acidic conditions.Results and discussion
The pH of the culture solution increased as culture time rose. The gradient of change increased with rising NO3 ?/NH4 + molar ratios. Maize roots released more hydroxyl ions at pH 4.0 than at pH 5.0. The amount of hydroxyl ions released by maize roots at a constant pH was greater than those at a nonconstant pH. Application of calcium nitrate reduced exchangeable acidity and increased the pH in an Ultisol rhizosphere, compared with bulk soil. The increasing magnitude of soil pH was greater at higher doses of N. The absorption of NO3 ?–N increased as the NO3 ?/NH4 + molar ratios rose, which was responsible for hydroxyl ion release and pH increases in culture solutions and rhizosphere.Conclusions
Root-induced alkalization in the rhizosphere resulting from nitrate absorption by maize plants can be used to ameliorate acidic Ultisols. 相似文献998.
999.
1000.