变频器电磁谐波污染及抑制措施

变频器高次谐波带来的电磁干扰和污染问题危害较大,本文从变频器工程实际应用出发,从隔离、屏蔽、滤波和接地四个方面全面阐述了抑制和消除干扰的方法。     

Principle and Key Technology of Full Automatic Vicat Apparatus

In this paper the working principle and performance character of both the manual and automatic Vicat apparatuses in existence are compared and analyzed,and their existing weakness and the urgent problem to be solved are pointed out.On this basis,adopting the technology of mechatronics and modern sensors,a new sort of full automatic Vicat apparatus that can fully satisfy the national standard in testing the setting time of the cement has been developed.This apparatus can be operated expediently with high precision,the test results are to be analyzed and computed automatically.This paper presents the working principle,performance character,key technology and prospect of application for the full automatic Vicat apparatus.     

Remote sensing of biotic and abiotic stress for irrigation management of cotton

The applicability of commercially available remote sensing instrumentation was evaluated for site-specific management of abiotic and biotic stress on cotton (Gossypium hirsutum L.) grown under a center pivot low energy precision application (LEPA) irrigation system. This study was conducted in a field where three irrigation regimes (100%, 75%, and 50% ET_c) were imposed on areas of Phymatotrichum (root rot) with the specific objectives to (1) examine commercial remote sensing instrumentation for locating areas showing biotic and abiotic stress symptomology in a cotton field, (2) compare data obtained from commercial aerial infrared photography to that collected by infrared transducers (IRTs) mounted on a center pivot, (3) evaluate canopy temperature changes between irrigation regimes and their relationship to lint yield with IRTs and/or IR photography, and (4) explore the use of deficit irrigation and the use of crop coefficients for irrigation scheduling. Pivot-mounted IRTs and an IR camera were able to differentiate water stress among irrigation regimes. The IR camera distinguished between biotic (root rot) and abiotic (drought) stress with the assistance of groundtruthing. The 50% ET_c regime had significantly higher canopy temperatures than the other two regimes, which was reflected in significantly lower lint yields when compared to the 75% and 100% ET_c regimes. Deficit irrigation down to 75% ET_c had no impact on lint yield, indicating that water savings were possible without reducing yield.     

基于Visual C++MSComm通讯控件的排种器实验台变频调速系统设计

介绍了排种器试验台变频调速系统的系统组成,以及实现计算机与变频器之间串行通讯的硬件构成及程序设计方法, 以此实现了计算机与变频器的串行通讯。利用本系统可以满足排种器实验台对计算机控制的速度实时调节的要求。     

PLC及变频调速恒压喷灌系统的设计

针对喷灌系统受作业区域需水量的影响造成系统喷头不能稳定可靠工作的问题,结合工程实例,提出了利用PLC及变频器来实现温室喷灌系统恒压供水.给出了变频调速恒压供水系统原理图,并进行了系统的主电路设计和软件设计.阐述了利用上位机、PIC、变频器、压力变送器、电机-水泵系统等组成的恒压供水系统,能按照设定的工作压力,实时切换泵组投入工频或变频状态运行,达到恒压供水的目的.系统能通过上位机实现下位机的控制参数的设定、系统的实时监测、数据管理等任务,自动化程度高.应用表明,系统实现简单,操作方便,运行稳定,可靠,且具有较好的节能效果.     

生物传感器及其发展概况

简要介绍了生物传感器的概念、结构、基本原理和国内外发展概况。     

SIDE LOBES AND GRATING LOBES ARTIFACTS IN ULTRASOUND IMAGING

Side lobes and grating lobes are both unwanted parts of the ultrasound beam emitted off axis that produce image artifacts due to error in positioning the returning echo. The purpose of this study was to reproduce artifacts associated with side lobes and grating lobes in vitro using different transducer types and recognize these artifacts in vivo. A phantom, composed of a water bath, a metallic wire, and a wooden tongue depressor, was imaged using a linear array, a curved linear array, a vector array, and a sector mechanical transducer. When imaging the metallic wire in a transverse plane, an echogenic artifact was constantly seen on each side of the wire, with a shape and intensity variable with the transducer type. The artifact was curvilinear and concave (linear and curved linear arrays), or curvilinear and convex (vector array and the mechanical transducer). When the tongue depressor was imaged in a longitudinal plane, the artifact was a straight line (linear array), a curved convex line(curved array), a series of convex curvilinear echo (vector array) or a small convex curvilinear echo (mechanical transducer). In vivo situations similar to the phantom experiment were investigated using clinical patients. Artifacts produced in vitro were recognized in vivo when a highly reflective object (urinary bladder wall) was imaged adjacent to an anechoic region (urine). These artifacts corresponded to the principle of secondary ultrasound lobes, and were therefore interpreted as such.     

传感技术在精确检测植物水分中的应用研究

将传感技术应用于植物水分的精确检测,从而达到节水的目的。其关键技术是研究可同时精确测量叶片厚度微变化和温度的双参数融合式传感器,测量叶片厚度微变化的传感器原理实验已经完成。     

铜热电阻平均温度传感器研究与分析

油罐中石油及其液体产品的平均温度测量不准，将直接影响着液体体积的测量精度。从油罐储量对温度测量的要求出发，介绍了铜热电阻平均温度传感器的结构，通过理论分析，指出了提高精度的途径。