影响棉种介电式分选效果的主要因素

对影响棉花种子介电常数的重要因素进行了详细论述。对影响种子极化特性的各个因素进行了对比分析，发现了棉花种子极化特性随分选电极各参数变化的规律，并提出了改进分选效果的措施。经过对比表明，新建的模型改进了前人所建模型的不足，更符合于实际情况，对设计合理的棉花种子介电式分选机具有指导意义。     

小颗粒种子介电分选试验研究

介绍了一种介电式种子分选机的结构及工作原理。通过对油白菜和苜蓿等小颗粒种子进行二次回归正交试验，得出了以分选电压和滚筒转速为分选因素的回归方程和较优的分选参数。同时，对回归方程进行了检验，结果表明，两种种子的回归方程都在不同水平达到显著程度。     

食品介电特性参数试验机理分析

分析了食品介电特性参数的理论基础,结合试验研究的现状,探讨了介电特性参数的物理意义和使用条件。指出以测量食品等效电容对应食品其他性质的方法而得出结论的重复性和可验证性较差;食品介电特性研究需同时指出测量的频率,甚至需要通过介电常数频谱测量,找出测量该物料复介电常数的最佳频率;复介电常数测量受到夹持物料应力大小的影响。     

介电式蔬菜种子分选机组通过鉴定

由河北省农业机械化研究所研制的0.2型介电式种子分选机组,于1992年12月通过河北省科委组织的鉴定。该机组主要由5QX—0.2型风筛式清选机、5JDX—0.2型介电式种子分选机及风力提升装置组成。鉴定委员会一致认为,本项研究有如下特点:     

干酪介电特性研究进展

结合干酪介电特性的国内外研究现状,介绍干酪介电特性测试相关参数,以及微波频率下干酪介电特性的测定方法,分析成熟期内干酪成分与介电特性参数的关系,为进一步研究介电特性在干酪品质评定中的应用提供参考。     

谷物和种子介电特性的研究及应用进展

为了更好地研究农业物料介电特性,总结了国内在应用介电特性测量谷物的含水率、种子的介电分选,以及种子电致生物效应等方面的研究进展。     

农业物料介电特性的测试及影响

在进行农业物料相关品质检测与加工时,往往需要测定其许多参数,其中介电特性随物料种类的不同而体现出差异性,可以根据这一特性对不同物料的物性进行表达。此外,同种物料本身的介电特性又与许多因素有关,利用影响因素与介电特性的相关性,可以对物料的品质因素进行判定,对加工过程进行实时监测和优化控制。综述分析了国内外农业物料介电特性的相关研究,介绍了生物电学模型及介电特性的各种测试方法,并概括了各种测试方法的优缺点,总结了不同方法的适用条件以及受约因素。综述农业物料(特别是果蔬)的介电特性受到电磁场参数、温度、物料外形参数以及水和离子行为的影响,为研究果蔬介电特性在果蔬干燥、保鲜、品质检测等方面的应用提供参考。     

介电参数数值实验在探地雷达试验检测中的应用

相对介电常数标定是探地雷达试验检测的重要内容,直接影响探地雷达的试验检测精度,常规的方法是采用取芯进行校正,从反射时间和芯样厚度来获取波速和近似的相对介电常数,常常忽略了介电参数中电导率对雷达波速的影响。为减少单一的取芯校正方法带来的误差,采用时域差分法,对不同电导率的钢筋混凝土介质的双介电参数进行数值实验,分别从数值模拟剖面、单道波信号、电场分量波场快照3个方面,讨论了钢筋混凝土介质的相对介电常数、电导率和波速三者之间的关系,并分别采用三次插值和双调和样条插值方法获得了双介电参数对雷达波速校正的相关关系。结果表明：双介电参数与雷达波速的相关关系呈分段曲面分布,应综合考虑电导率和相对介电常数来进行雷达波波速校正。     

蔬菜和花卉种子清选

清选蔬菜和花卉种子的原理与清选大田作物种子相差甚微。种子清选一般最先使用气流式筛选机,比重式分选机常常作为最后工序。     

棉种介电分选试验

介绍了介电选种机的分选机理,通过对棉花种子的试验,并用试验设计的正交实验设计,从而得出了棉种介电分选的最佳分选电压和转速。     

介电特性在农产品品质检测分析中的应用

阐述了低频范围内水果介电特性与其新鲜度和内部损伤的关系,以及谷物介电特性与颗粒大小、水分含量的关系。介绍了介电特性的基本概念、主要参数和测定方法及其在水果和谷物品质检测分析中的应用。     

Comparison on Physical and Chemical Characteristics and Electric Properties of Three Types of Vegetable Insulating Oil

Three types of vegetable oil, transgenic rapeseed oil, transgenic peanut oil and cotton-seed oil, are used as raw materials in experiments to obtain the refined insulating oil. The dosage of reagent in experiments is studied for vegetable insulating oil refinement. Furthermore, basic physical and chemical properties of the three types of vegetable insulating oil are analyzed. The electrical properties including breakdown voltage, dissipation factor, dielectric constant, and volume resistance are studied and presented. By compared with each item of properties of the three types of vegetable insulating oil, rapeseed-oil-based insulating oil is considered to possess the best properties due to the fact that it is more abundant of mono-unsaturated fatty acid than the other two types of insulating oil.     

滨海盐土棉田棉花水、盐遥感监测系统的设计与实现

 为监测滨海盐土棉田棉花的水、盐状况,对盐碱地植棉提供理论依据。本研究运用软件工程的思维,耦合了基于地面遥感手段构建的棉花功能叶水、盐状况监测模型和土壤介电常数模型,开发了具有监测滨海盐土棉田棉花和土壤水、盐状况功能的遥感监测系统。系统以光谱反射率和土壤介电常数数据为基本输入,对棉花功能叶和棉田土壤水、盐状况进行了预测计算,运行结果以表格和图形的形式输出。应用结果表明,该系统操作简单、运行稳定,监测结果准确,可为农业生产者、管理人员和科技人员提供棉作数字化和科学化的决策支持。     

Field evaluation of transgenic Brassica napus lines carrying a seed-specific chimeric 2S albumin gene

The agronomic performance of transgenic Brassica napus lines carrying chimeric 2S albumin seed protein genes was studied under field conditions. A total of 37 transgenic lines were compared to non-transformed lines. Plant development, morphological characteristics, yield parameters and seed composition were considered. Only a few transgenic lines differed from the control, and then only for particular parameters: four lines had altered leaf morphology, two differed in germination efficiency, one differed in yield, and three differed in some parameters of seed composition. These differences were not correlated with the presence or expression of the transgene and, thus, were more probably linked to cell- or tissue-culture effects, or to residual variation present in cv. ‘Drakkar’. A statistical interaction between variations in a limited number of seed composition parameters and cell haploid culture was observed. While the expression of the chimeric 2S albumin gene was not as high as hoped, this study demonstrates that transgenic lines can be isolated in which the intrinsic morphological and agronomic properties of the original lines are maintained.     

Transfer and water-retention properties of seed-pelleting materials

Until now, the choice of materials for seed pelleting has been mostly empirical. We have analysed coating materials (silicate powder A, clay B and hydrophobic clay C) and their water-transfer properties. Seed-pelleting materials were studied with conventional soil-analysis techniques. An original device for studying water transfer through a thin layer of powder was designed to simulate the transfer of water from the soil to the seed, through the pelleting material. Different parameters were studied: particle-size distribution, water-retention curve of materials, thickness of powder, influence of concentration of adhesive in pelleting, etc. The sintered glass on which the powders were placed in the device constituted a limiting factor. The major component, a silicate powder (A), consisting of large particles, is responsible for the general structure of the pelleting. Introduction of clay (B) gave intermediate properties between A and C to water-transfer capacity. Hydrophobic clay (C) can be used to control the incoming flow. The particle-size distribution and wettability of materials have a direct impact on the transfer capacity of the powder. High adhesive concentration had a negative effect on water transfer. These parameters and the formulation have a direct impact on imbibition of pelleting materials. Objective tools, like the analytical methods used in this study, enable water-transfer parameters and consequences on imbibition of coated seed to be understood.     

Genetic variation among and within populations of <Emphasis Type="Italic">Cordia africana</Emphasis> in seed size and germination responses to constant temperatures

Cordia africana Lam. is a commercial timber species that grows naturally throughout sub-Saharan Africa and tropical Arabia. At present very little is known about genetic variation in this species and baseline information is needed to initiate improvement programs in Ethiopia. Thus, the objectives of the study were to quantify the inter- and intra-population variations in seed size traits and germination responses to different constant temperature regimes. Seeds were collected from 30 open-pollinated families within each of the five populations representing the natural distribution of the species in Ethiopia. To examine seed size variations, seed length, seed width, and 1,000-seed weight were quantified. Inter- and intra-population variations in seed germination were investigated under different constant temperature regimes from 20 to 35°C in climate chambers. Significant variations in seed length, width and weight were detected both at inter- and intra-population levels, and family heritabilities of 0.63–0.76 showed that much of the phenotypic variation in seed size traits were additive genetic variation. Significant variation in germination was also found among and within populations as well as between the different constant temperature regimes. Generally the variation in germination was considerably higher within population than between populations. The optimal temperature for germination of C. africana seeds was 25–30°C with family heritabilities for germination ranging between 0.20 and 0.33, depending on the germination temperature.     

Practical considerations for using a TDR cable tester

Time domain reflectometry (TDR) technology can be used to measure soil water content, but due to an incomplete understanding of this technology, some scientists are still reluctant to adopt it. The objectives of this paper are to discuss the basic principles of TDR to measure soil water content, to present the equations to convert TDR screen readings to soil water content values, and to describe a custom built TDR system. Commercial cable testers operate under the assumption the dielectric constant of the medium is known. For soils applications the dielectric constant varies with soil water content and is unknown. The equations which govern the TDR technology presented in logical order allow the user to understand the relationships between wave velocity, dielectric constant, and soil water content. The custom-built TDR system described here uses a commercially available cable tester; a balun transformer; shielded, two-wire transmission cable; and wave guides constructed from stainless steel welding rod. Several of these systems have been successfully used for six years.