精密播种机PLC控制系统研究

针对传统PC机或单片机控制系统在精密播种控制过程中对工作环境要求高、可靠性低、对操作人员技术要求高、推广性差等问题，提出将PLC作为控制器用于精密播种机控制系统。研究内容包括精密播种机系统总体设计、控制系统设计，以及驱动装置与执行机构动作的编程实现等。试验结果表明，基于PLC控制的精密播种机控制系统稳定性及故障响应率均较高，符合精密播种要求。     

试论排种器分类族谱

文章用精确、可控、定量的观点，对应用较为普遍的排种器从能否形成等时距均匀种子流的角度，分析基排种元件的结构形态、采用的基本原理和运动规律；对各排种元件控制排种量的方式、能否精确控制排种量等进行了探讨，对该排种器是属于精密排种器，是否对种子即能精确控制单粒，又能精确定粒作了评价。期望从原理不一、构造众多的诸排种元件中找出规律，得到启迪，进而创新研究出中耕作物和分蘖作物都适用的精密排种器。     

精密与超精密磨削的发展现状

介绍了精密磨削与超精密磨削的机理，阐述了精密磨床以及精密磨削与超精密磨削技术的研究现状，并分析了精密磨削与超精密磨削的发展趋势．     

霍尔效应电子测微方法的研究

本文介绍用两片 UGN—3501T 线性霍尔集成电路构成的差动输出传感器,配合微处理机技术,设计出一套电子测微仪实验模型。实验结果表明,仪器在0～255μm 范围内分辨率为1μm,线性、迟滞和重复性均较理想,精度可达机械精密加工实时测量用的新型数字显示仪表。     

综述超精密加工技术的特点及发展方向

随着科技的发展,国家尖端技术和国防工业需要超精密加工技术的高水平。为提高技术水平,各国积极投入人力物力进行研发,同时对关键技术进行保密,控制关键速发展和广泛应用,对高精度复杂零件、光学零件加工需求日益迫切。目前,国外已开发了多种精密和超精密车削、磨削、抛光等机床设备,发展了一系列新的超精密加工技术。     

基于单个神经元的线性最优励磁控制器

线性最优励磁控制采用固定反馈增益矩阵来完成对发电机在电力系统运行时的控制，由于发电机功角特性的非线性，因而在不同运行点是不能一直满足最优控制的目的。提出了一种基于神经网络的线性最优励磁控制器，将两者的优点结合在一起，利用神经网络在在线调整控制变量，使同步发电机在不同运行点的动态，暂态稳定性能始终保持最优控制效果。     

精密播种机排种自动控制装置

为提高精密播种机的播种均匀性。解决地轮打滑和手动调换链轮或调整排种器排种量的问题．研究了一种用于精密播种机的排种自动控制装置。系统由五轮仪、智能控制单元、人机接口单元和执行单元组成，可以完成数据的输入、处理和排种器转速的控制。作业时系统采用五轮仪测量播种机的作业速度。用步进电机代替地轮作为执行机构带动排种器转动，减小了地轮打滑对播种均匀性的影响。该控制装置可以直接对五轮仪直径、排种器孔数和播种量等参数进行设置，使用方便。试验结果表明，系统运行稳定，可保证排种器与五轮仪转速同步。提高了播种机的播量均匀性，达到了设计目标。     

基于线性矩阵不等式的Acrobot鲁棒镇定控制

针对欠驱动机器人Acrobot，提出一种基于线性矩阵不等式的鲁棒镇定控制方法。通过将Acrobot在垂直向上不稳定平衡点附近的第一杆角速度看作一种不确定性，得到Acrobot的不确定模型，在此基础上设计一种基于线性矩阵不等式的鲁棒镇定状态反馈控制律，实现Acrobot较大范围的平衡控制。仿真和对比结果验证了方法的有效性和优越性。     

基于超声波传感器的电极长度实时测控系统

设计与开发了以工控机为核心，以MCGS组态软件为开发平台，基于可编程超声波精密传感器的电极长度实时测控系统．提出了实时测量电极挤出长度并控制电极挤出速度的方法．该系统通过测量电极剪切端面与传感器之间的距离，计算电极的挤出长度，并以电极长度为反馈量控制电极挤压速度，实现了电极剪切的零速定位．实际运行表明，系统可靠、有效，电极长度误差小于10mm．     

人参精密点播机的研制

本文主要介绍作者等研究的电磁振动、光电控制人参精密点播机的研究情况.本机已取得国家专利,专利号为87 2 10111。     

Slant perception and shape constancy in infants

Three experiments investigated shape constancy in human infants between 50 and 60 days of age. The first showed that such infants possess some capacity for shape constancy. The second confirmed this finding and showed that the capacity is not attained by correlation of perceived projective shape with perceived orientation.     

Memory Constraints and Flower Choice in Pieris rapae

Darwin hypothesized that flower constancy in insects that feed on nectar results from the need to learn how to extract nectar from a flower of a given species. In laboratory tests, Pieris rapae, the cabbage butterfly, showed flower constancy by continuing to visit flower species with which it had experience. The time required by individuals to find the source of nectar in flowers decreased with successive attempts, the performance following a learning curve. Learning to extract nectar from a second species interfered with the ability to extract nectar from the first. Insects that switch species thus experience a cost in time to learn. These results support recent suggestions on the importance of learning in animal foraging.     

Weber Ratio for Visual Discrimination of Velocity

As an approximation based on various experiments reported in the literature, the least detectable difference in speed (delta w) varies in direct proportion to the speed (w) over a range from 0.1 to 20 degrees of visual angle per second. The constancy of the Weber ratio (deltaw/w) aids in understanding how men react to velocity in various situations.     

Life at high temperatures. Evolutionary, ecological, and biochemical significance of organisms living in hot springs is discussed

The time is now ripe for a concerted attack on the evolutionary, ecological, and molecular aspects of life at high temperatures. Hot springs provide nearly ideal ecosystems for such study, since they are natural environments of great antiquity and relative constancy, where organisms have evolved to meet the environmental challenges of high temperatures. Even from our present limited knowledge, we can draw a number of conclusions.     

论爱因斯坦光速不变原理的认识论重构

爱因斯坦光速不变原理作为狭义相对论的理论基础之一,导出了同时性的相对性,突破了时间和空间传统的形而上学观念,从其诞生之日起就存在着巨大的争议。光速不变原理是对光速问题的近似陈述,从解题的意义上讲,是科学命题而不是伪命题,但它有瑕疵,是一个需要完善发展和精确的命题。只要解决了认识论问题,我们对光速不变原理就会有更好地理解和把握。     

Measurement of a visual motion aftereffect in the rhesus monkey

A monkey was trained to discriminate between a shrinking and expanding test figure presented after steady fixation of the center of a rotating spiral. Differential shifts in the animal's perception of size constancy were found for clockwise and counter-clockwise rotation of the spiral. The magnitude of the aftereffect was within the range found in human subjects.     

Chlorine-36 dating of saline sediments: preliminary results from searles lake, california

Measurements have been made of the ratios of chlorine-36 to chlorine in five halite samples from Searles Lake sediments, previously dated by carbon-14, thorium-230, and magnetostratigraphic techniques. The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio over the last million years.     

Nuclear number in the rotifer asplanchna: intraclonal variation and environmental control

The gastric glands and vitellarium of Asplanchna are exceptions to the rule of constancy of the number of nuclei in rotifers. The two glands of a female may have different numbers of nuclei. Nuclear number in both organs varies widely among different individuals in a single culture. The mean nuclear number characteristic of a clone may be modified by dietary changes.     

Prometheus: Io's wandering plume

Unlike any volcanic behavior ever observed on Earth, the plume from Prometheus on Io has wandered 75 to 95 kilometers west over the last 20 years since it was first discovered by Voyager and more recently observed by Galileo. Despite the source motion, the geometric and optical properties of the plume have remained constant. We propose that this can be explained by vaporization of a sulfur dioxide and/or sulfur "snowfield" over which a lava flow is moving. Eruption of a boundary-layer slurry through a rootless conduit with sonic conditions at the intake of the melted snow can account for the constancy of plume properties.     

逊克产中国林蛙的染色体组型

采用骨髓细胞制片法，对逊克产中国林蛙（Rana chensinensis)的染色体组型分析表明，其染色体数目为2n=24，分为3组，A组（第1-5对）；B组（第6对）；C组（第7-12对）。第1-5对染色体的短臂上告近着丝粒部位往往有一次缢痕。第2、8、10、12对染色体的长臂上也往往有次缢痕，而第10对染色体的长臂上次缢痕是衡定的，雌雄具体间未见异型染色体。