玉米种子加工线的计算机仿真分析

本文用计算机仿真手段对吉林省2000t的玉米种子加工线再现了其两种工艺流程,根据现场反映的配套问题和仿真结果对第一工艺流程提出了改进方案,认为现有系统的精选机生产率应增加一倍,能提高经济性,并且对具有不同仓数的系统进行了分析。     

Irrigation Module and Sowing Date Affect Seed Cotton Yield,Quality, Productivity Indices,and Economics of Cotton in North-western India

ABSTRACT

Delayed sowing and imprecise application of irrigation water to cotton has been the major hurdle in sustaining cotton yield in north-western India. Therefore, studies were initiated to ascertain the impact of heavy or normal level of presowing irrigation (PSI), scheduling time of first postsowing irrigation (POSI) under two sowing dates (SDs) on cotton arranged in a split block design replicated thrice. PSI_h (100 mm) recorded 23.2% higher seed cotton yield over PSI_n (70 mm) owing to better yield attributes and higher stand. First POSI at 4 weeks after sowing (WAS) resulted the highest yield (3072 kg ha^?1), while one at 6 WAS (POSI₆) recorded least due to poor population and reduced yield attributes. Water productivity under POSI₆ was lesser by 29.1%, 25.2%, and 16.2% as compared to POSI₃, POSI₄, and POSI₅, respectively. April sown crop out yielded the May sown cotton crop by 939 kg ha^?1 due to better yield attributes. Nitrogen factor productivity (NFP) among SD remained higher by 23.3% for April as compared to May sowing. PSI_h exhibited better NFP over PSI_n. POSI₆ recorded least NFP by 24.4%, 28.5%, and 16.3% as compared to POSI₃, POSI₄, and POSI₅, respectively and was indicative of relatively poor utilization of N under delayed schedules. Therefore, planting in April after heavy PSI and scheduling first POSI at 4 WAS is best strategy for sustaining cotton yield and maximizing farmer profitability.     

播种机组纯作业时间利用率与地块条件的匹配模型与试验

机械化播种作业是现代农业生产的重要环节,纯作业时间利用率是衡量播种机组作业效率的重要指标。该研究依据农业机组运行机理,在调查研究的基础上,提出季节时间利用率概念,确定了播种机组的作业时间构成,建立了播种机组纯作业时间、转弯时间、加种肥时间的计算模型和3种加肥方式下的播种机组纯作业时间利用率计算模型,明确各参数随地块面积、地块长度等条件变化的一般规律;以此为基础,在机组正常作业状态下,采用定距离多点多设备同步跟踪测的试验方法获取4种典型播种机组各类作业时间数据,并运用3σ原理剔除无效数据;依据所建模型及有效试验数据,采用Matlab 2012b对4种播种机组的纯作业时间利用率随地块条件变化规律进行模拟仿真,并采用Sigmaplot 12.5软件直观表达试验结果;进而探索了播种机组纯作业时间利用率随地块条件化的原因,确定了目标时间利用率条件下不同播种机组与其所适宜的作业地块面积和地块长度的定量关系:播种机组纯作业时间利用率大于0.6时,约翰迪尔7830机组适合作业地块面积大于等于6 hm^2、地块长度为1 200~1 400 m;维美德171机组适宜作业地块面积大于等于6 hm^2、地块长度为1 000~1 200 m;常发504机组适合作业的地块面积大于等于1 hm^2、地块长度为500~1 500 m;黄海254机组适合作业的地块面积大于等于0.3 hm^2、地块长度200~1 500 m。研究成果可为不同地块条件的播种机组选型提供定量依据。     

两种巨桉人工林地土壤抗蚀性的比较研究

[目的]揭示巨桉人工林组培苗和实生苗两种起源对土壤抗蚀性的影响。[方法]利用S形采样法在样地内采集多个样点,按上(0—10cm),中(10—20cm),下(20—30cm)三层分别利用环刀和塑料盒采集原状土壤,测定不同层次土壤容重、非毛管孔隙度、毛管孔隙度、总孔隙度、渗透速率、水稳性团聚体含量等。[结果](1)随着土壤深度增加,两种巨桉林地土壤容重呈现递增趋势,而总孔隙度和通气孔隙度呈递减趋势。组培巨桉林土壤容重低于实生苗巨桉林地,而土壤总孔隙度、通气孔隙度高于显著实生苗巨桉林地(p0.05);(2)随着土壤深度增加,两种巨桉林地土壤水稳性指数、抗蚀指数、团聚状况、团聚度和结构系数呈现下降趋势,水稳性指数和抗蚀指数达到显著水平(p0.05),而分散率和分散系数呈现升高趋势。组培巨桉林地不同土层的抗蚀指数和结构系数均高于实生苗巨桉林地,但分散系数均显著低于实生苗巨桉林地(p0.05);(3)随着土壤深度增加,两种巨桉林地土壤各粒径水稳性团聚体含量和平均重量直径(MWD)呈现出下降趋势,土壤结构体破坏率呈现上升趋势。组培苗巨桉林地不同土层各粒径(5mm;5~2mm;0.5~0.25mm;0.5mm;0.25mm)水稳性团聚体含量和MWD均高于实生苗林地,而结构体破坏率、2~1mm和1~0.5mm水稳性团聚体含量均低于实生苗巨桉林地。[结论]组培巨桉人工林的土壤抗蚀性更佳。     

Impact of selective logging on genetic composition and demographic structure of four tropical tree species

Over-exploitation and fragmentation are serious problems for tropical forests. Most sustainable forest management practices avoid clear-cuts and apply selective logging systems focused on a few commercial species. We applied a simulation model to estimate the impact of such selective logging scenarios on the genetic diversity and demography of four tropical tree species from French Guiana. The simulations used data on genetic and demographic composition, growth, phenology and pollen and seed dispersal obtained for Dicorynia guianensis, Sextonia rubra, Symphonia globulifera and Vouacapoua americana at the experimental site in Paracou. Whereas Symphonia globulifera serves as a model for a species with low logging pressure, the other three species represent the most exploited tree species in French Guiana. In simulations with moderate logging, typical for French Guiana, with large cutting diameter (>60 cm diameter) and long cutting cycles (65 years), the two species V. americana and Sextonia rubra were not able to recover their initial stock at the end of the rotation period, with a large decrease in the number of individuals and in basal area. Under a more intensive logging system (cutting diameter >45 cm diameter, cutting cycles of 30 years) that is common practice in the Brazilian Amazon, only Symphonia globulifera showed no negative impact. Generally, the differences between the genetic parameters in the control scenarios without logging and the logging scenarios were surprisingly small. The main reasons for this were the overlapping of generations and the effective dispersal ability of gene vectors in all species, which guarantee relative homogeneity of the genetic structure in different age classes. Nevertheless, decreasing the population size by logging reduced the number of genotypes and caused higher genetic distances between the original population and the population at the end of the logging cycles. Sensitivity analysis showed that genetic changes in the logging scenarios were principally determined by the growth, densities and cutting diameter of each species, and only to a very small extent by the reproductive system including factors such as pollen and seed dispersal and flowering phenology.     

腾格里沙漠南缘种子植物区系及其资源属性

[目的]调查植物区系,分析资源属性,为提高当地居民经济收入,改善农村产业结构提供依据。[方法]以样地调查数据为基础,通过查阅种子植物名录,对种子植物的区系属性、生活型属性和资源属性进行综合分析。[结果]腾格里沙漠南缘有种子植物31种,隶属16科,31属,大科属种为黎科、菊科和禾本科,草本植物最多,占总种数的67.7%,生态植物、饲(食)用植物和药用植物分别占总种数的83.87%,51.61%%和58.06%。[结论]大科属种为黎科、菊科和禾本科,它们在该保护区系中占有重要的地位,表现出它们在该保护区植物区系中的重要性,植物生活型中草本植物最多,生态植物、以饲(食)用植物和药用植物所占比例较大。     

预切种式木薯排种机构设计与试验

针对当前预切种式木薯播种器存在充种效果差、合格指数低的问题，该研究设计了一种由落种滑板、主动辊筒、型孔摩擦带、支撑辊组、从动辊筒及储种箱等组成的预切种式木薯型孔摩擦带式精密排种机构。阐述了排种机构的基本结构和工作原理。对关键部件参数进行设计，通过理论分析确定影响排种机构充种性能的主要因素为型孔摩擦带型孔形状、型孔数量、型孔摩擦带安装倾角、型孔摩擦带速度以及种茎层厚度。基于离散元法（discrete element method,DEM）建立种茎群-型孔摩擦带仿真模型，通过单因素仿真分析各因素对充种性能及种茎群规律的影响。以充种合格指数和漏充指数为评价指标，通过二次回归正交旋转组合仿真分析确定最优参数，利用Design-Expert数据软件，建立各试验因素与评价指标的数学回归模型，并进行参数优化。结果表明，影响充种合格指数和漏充指数的因素主次顺序为型孔摩擦带速度、型孔摩擦带安装倾角和种茎层厚度，圆整后的最优参数为型孔摩擦带速度0.6 m/s、型孔摩擦带安装倾角45°，种茎层厚度250 mm，此时的模型预测充种合格指数为94.63%，漏充指数为3.42%，重充指数为1.95%。在最优参数下...     

黄土丘陵沟壑区不同复垦时间沙棘纯林物种多样性分析

以生态修复为目的的人工沙棘林具有较好的水土保持效应,在生态环境的恢复建设中意义重大。但是通过对沙棘群落土壤种子库和地上植被的研究发现,随着样地复垦时间的增加,其物种多样性指数的提高趋势下降。由此可见沙棘纯林存在弊端,应考虑生态建设的可持续发展。     

Phylogenetic relationships of Cajanus cajan (L.) Millsp. (pigeonpea) and its wild relatives based on seed protein profiles

Total seed storage protein of 9 accessions of cultivated C. cajan and 10 wild Cajanus species was reported and compared by sodium dodecyl sulphate polyacrylamide gel electrophoresis. A considerable variation was detected among the protein profiles of different accessions of C. cajan while those of wild species were very specific and distinctly different from each other. Relative similarities between various taxa were estimated by Jaccard's similarity index and cluster analysis was performed to produce a UPGMA dendrogram. The clustering of 10 wild species and C. cajan more or less agrees with their sectional classification and available data based on morphological characteristics, crossability, genome pairing in hybrids and nuclear RFLPs. The species closest to C. cajan is C. cajanifolia although the accessions of C. cajan also share some bands present in the profiles of C. scarabaeoides, C. goensis, C. lineatus, C. acutifolius and C. volubilis. This points towards polyphyletic origin of the cultigen which has been discussed in this paper.