套管磁化与过套管介质识别

研究套管磁化技术与套管外介质的识别方法.建立了柱状分层介质的电磁响应模型,分析了套管磁导率对电磁响应信号的影响,从理论上说明了对套管进行磁化的必要性.采用带有磁轭的纵向磁化法,对51/2英寸的套管进行了磁化,实验表明,套管被磁化后,电磁信号可有效地穿过套管,并对磁化后套管外的空气、水、盐水等不同的介质的识别进行了实验研究,结果表明,当介质不同时,根据套管内接收线圈所接收到的二次场信号的幅度和延迟时间,可有效地识别套管外的介质,从而证实了采用套管磁化法进行过套管测井的可行性.同时也为生产井的剩余油探测提供了技术支撑和理论依据.     

基于自谐振恒压钳位的线性快速关断技术（英文）

瞬变电磁法(Transiant electromagnetic method, TEM)以其探测效率高、探测深度大等优点,在中浅层地下探测领域得到了广泛的应用。但由于发射线圈本身的电感特性,导致发射电流的关断时间较长,且发射电流激发的一次场将会淹没含有浅层地质信号的早期信号。针对现有的瞬变电磁发射机存在的关断时间长,大功率发射缺少可靠有效的钳位手段的现状,设计了一种新的瞬变电磁发射机快速关断电路。使用自谐振零电压开关技术向钳位电容充能,同时设置相应的时序控制电路,最终研制完成了基于自谐振恒压钳位技术的瞬变电磁发射机一台。发射机额定发射电流20 A,关断时间从550-50μs连续可调,电流下降过程近似线性,不再按照一阶电路的指数规律下降。与现有的钳位方式相比,这种钳位方式解决了传统瞬态二极管(Transient voltage suppressor, TVS)钳位不能用于大功率场合、故障率高、小尺寸发射线圈电感量不足造成使用储能电容钳位时预充电时间过长的问题。该技术为大电流快速关断提供了一种有效的方法。     

恒压钳位高速关断瞬变电磁发射系统

瞬变电磁发射机是瞬变电磁探测设备中的重要组成部分,在大功率电流陡脉冲发射、高精度同步控制、下降沿线性度、短关断时间和关断时间测量等方面,有许多亟待解决的问题.提出了一种瞬变电磁发射系统,DSP和FPGA协同工作为系统提供可靠的驱动信号和保护措施;提出了恒压钳位电路,配合合适的阻尼吸收电路,具有关断时间短、电流下降沿线性度高和发射电流大的特点,并可提升脉冲电流前沿上升速度;提出了新颖的关断时间测量电路,测量准确简单;设计了GPS同步控制器,采用GPS与温补晶振协同工作的方式,解决了GPS短时失效的问题,提高了系统的可靠性.对发射系统做了野外实验,测试表明,系统发射电流大、电流下降沿线性度高、关断时间测量准确、同步方式精确可靠.     

一种基于数字变频思想的电磁信号产生方法

针对频率域电磁法探测器需要形成多频电磁信号,提出一种新的电磁信号产生方法.参考数字变频的思想,由计算机模拟发射线圈电流并产生串行二进制数字代码流,控制开关桥路形成PWM电压,在发射线圈中形成电流信号,产生电磁波.该方法适应多种参数发射线圈,电磁信号频率成分可以灵活调整,电路效率可达90%.     

无线胶囊内窥镜新型接收线圈结构设计与分析方法

目前无线胶囊内窥镜(WCE)供应能量过低,限制了其诊查胃肠道病灶的性能。基于此提出了镂空三维接收线圈,线圈里可放置无线胶囊其他模块,进一步缩小无线胶囊体积。根据电磁场理论提出单匝分析法,分析了此线圈感应电动势和接收功率,并提出均匀度性能指标建立最优化模型,得出线圈最优设计参数;搭建角度姿态旋转平台测量线圈的感应电动势,实验测得感应电动势与理论值误差小于6%,验证了单匝分析法和线圈设计的合理性;将此线圈供能的无线胶囊内窥镜植入活体猪小肠内,得到的图像传输速率稳定为30 f/s,分辨率为400×400。新型线圈可给胶囊内窥镜提供充足稳定的能量,用于胃肠道疾病诊查。单匝分析法的应用不仅限于此结构的线圈,也可用于他它发射、接收装置相对位置和角度变化的植入式医疗设备的功率分析,并且此方法可用于求解发射和接收两级线圈之间的互感等电磁参数。     

一种浅地表探测收发天线的设计分析

通过对浅地表电磁探测系统的探测原理和收发天线的结构及参数研究,分析了频率域浅地表探测系统的工作原理。论证了利用磁场z分量间接探测浅地表地下介质电性结构的可行性。利用MATLAB对发射接收天线进行理论计算,分析了收发天线设计的关键问题;重新设计了探测系统所需的发射和接收天线,采用并联结构使发射天线效率有所提高,接收天线采用8字形结构,从结构上实现一次场的屏蔽,同时,避免了引入参考线圈使结构和计算复杂。通过实际测试,能够辨别出埋藏于土壤9 cm处的2 g电阻率异常体。最后,总结了埋藏深度、有无土壤对探测数据的影响。为浅地表探测天线系统的改进及近地表电磁成像系统研制提供依据及参考。     

基于微线圈阵列的多道神经电刺激信号透皮传输的初步实验研究

通过探索微线圈阵列实现多路神经电刺激信号透皮传输的可行性及影响传输效率的相关因素.根据电磁耦合原理,设计了包括脉冲发生、高频振荡、AM调制、功率放大、选频等刺激信号发射电路,信号接收电路,以及用于多通道信号耦合的微线圈阵列和相应实验测试装置.实验中对电路的性能以及线圈发生横向失配和角形失配时电路的可靠性进行了测试,在此基础上设计了2×2阵列的多通道传输装置.结果表明在调谐网络的作用下通道间信号的干扰较小,各通道输出信号能满足神经电刺激的要求.该方法经试验验证具有可行性,可用作各类植入式医疗仪器刺激或者控制信号的多通道传输装置,具有广泛的应用前景.     

小尺寸TEM非共面偏心自补偿零耦合收发技术研究

发射线圈对接收回路的耦合影响,是导致瞬变电磁(TEM)早期信号失真、浅层盲区大的主要因素之一,对于多匝小尺寸线圈结构,耦合影响更为严重。针对这一问题,提出了一种小尺寸TEM非共面偏心自补偿零耦合收发技术。该技术采用收发线圈非共面偏心的思路设计了一次场自补偿系统,非共面结构实现发射线圈与接收线圈的弱耦合,并基于互感理论获得二者的最佳相对偏心位置,以消除一次场干扰。对基于导电环异常体的探测模型进行实验仿真,结果表明新结构系统在收发线圈±2 mm尺寸误差内,能够忽略一次场的影响,对物理尺寸误差的容忍度较高,易于实现零耦合状态。最后,采用串连法对设计的非共面偏心自补偿TEM系统进行了实测实验,测试结果与理论分析一致,进一步验证新结构性能。研究可为小尺寸TEM系统获得纯二次场信号、提高浅层探测性能奠定理论基础。     

用于体内胶囊式遥测系统的电磁跟踪定位方法

提出了基于电磁检测原理的定位方法。该方法在体表布置多个电磁发射线圈,通过胶囊内密封的接收线圈检测所在点的磁感应强度,利用检测值,根据磁感应强度和该点位置坐标之间的函数模型反向求解出位置信息。设计的悬浮式单维接收线圈,能始终保持接收方向的恒定,不仅大大减少了接收线圈和发射线圈维数,也大大降低了求解模型的复杂性,满足了胶囊内严格的空间限制和功耗限制。设计了完整的电磁定位系统,构建了三维实验平台,并开展了38个位置点处的检测,将结果代入定位软件求解后表明,三个坐标方向的定位误差均在4 cm以下,平均定位误差在2 cm以下,小于同类研究的定位误差。     

WTEM高速关断瞬变电磁探测系统

瞬变电磁测量系统是一种用于地质结构探测的地球物理探测设备,在大功率电流陡脉冲发射、高精度同步控制、大动态范围信号采集等方面,尚有许多亟待解决的问题.本文提出了一种瞬变电磁测量系统,提出了恒压钳位高速关断电路,具有关断延时短、电流下降沿线性度高和发射电流大的特点,并加速了电流的上升,改善了一次场质量;采用蓝牙技术,实现了对接收机的无线操控,改善了系统操控性能;设计了GPS同步控制器,采用温补晶振与GPS协同工作的方式,解决了GPS短时间失效的问题.在山东输油管道腐蚀探测工程中,WTEM系统做了野外和室内实验,测试表明,WTEM系统轻便、操作容易,退饱和的速度也较快,反映浅层地质信息的能力强.     

基于磁敏元件的寄生式时栅传感器仿真分析

传统寄生式时栅位移传感器采用线圈传输电信号,不能保证线圈本身及绕线质量,导致寄生式时栅位移传感器体积大、灵敏度低、功耗大。根据寄生式时栅位移传感器的工作原理,选择一种基于磁敏元件代替绕制线圈的方法。用ANSOFT/Maxwell对磁钢和磁敏元件的气隙磁场、磁敏元件与被测齿轮之间的距离、磁钢大小和形状进行仿真,比较分析可知3mm×3mm×2mm的长方体磁钢在气隙为3mm的情况下能够满足磁敏元件的工作要求。     

Application of artificial neural networks for prediction of coercivity of highly ordered cobalt nanowires synthesized by pulse electrodeposition

This study aims to predict the coercivity of cobalt nanowires fabricated by Alternating Current (AC) pulse. Coercivity is one of the most important properties of magnetic materials and its value shows the needed magnetic field in a way that magnetization of system is decreased to zero. There are many parameters such as pH of solution, oxidative and reductive times, oxidative and reductive voltages, interval between pulses (off-time), and concentration of deposition solution that have direct effect on materials magnetic properties of. Change of initial conditions to obtain the best results is very time consuming, therefore employing a method which can save both the time and cost is necessary. Hence, it this study Artificial Neural Network (ANN), which has numerous applications and has attracted many attentions in various fields, was applied. Through this study, an ANN was designed to present a template that is capable for predicting output data (coercivity) according to input data (pH, oxidative and reductive times, oxidative and reductive voltages, and off-time). Besides, in this research, the results for pH = 4 and 6 were investigated and the effect of off-time as well as the deposition time on coercivity were studied.     

Development of novel clutch utilizing self-locking mechanisms of belt

A novel clutch was developed by using the self-locking property of belt friction. The frictional force is generated automatically by the torque applied. The belt starts to coil around the cylinder by the frictional force of the trigger pin at the end of the belt. Once the belt comes in contact with the cylinder, the belt coils automatically around the cylinder by the frictional force. Then the belt is locked firmly around the cylinder by the self-locking property of belt friction as long as driving torque is applying. The clutch is able to transmit rotational torque even in an off-centered condition.     

Evaluation of the characteristics of the microelectrical discharge machining process using response surface methodology based on the central composite design

Evaluation of the characteristics of a microelectrical discharge machining (Micro-EDM) process is challenging, because it involves complex, interrelated relationships so a proper modeling approach is necessary to clearly identify the crucial machining variables and their interrelationships in order to initiate more effective strategies to improve Micro-EDM qualities (electrode wear (EW), material removal rate (MRR) and overcut). This paper uses a response surface method (RSM) based on the central composite design (CCD) for Micro-EDM problems with four EDM variables (peak current, pulse on-time, pulse off-time and electrode rotation speed). Experimental results indicate that peak current is the EDM variable that most affects the Micro-EDM qualities for SK3 carbon tool steel while pulse off-time had a significant interaction with that. The results show that RSM based on the CCD could efficiently be applied for the modeling of Micro-EDM qualities (EW, MRR, and overcut), and it is an economical way to obtain the performance characteristics of Micro-EDM process parameters with the fewest experimental data.     

抗线圈偏移与倾斜的人工肛门括约肌经皮能量传输系统

传统的经皮能量传输系统大多采用开环系统,充电过程中患者要尽量保持不动,否则会导致线圈错位或翻转,影响接收 功率导致不能正常充电。 针对上述问题,本文首先采用 LCC-S 拓扑结构实现了接收端恒压特征,然后基于互感估计和原边功率 补偿的方法实时调节发射端发射功率对接收端电压进行控制。 仿真和体外实验结果显示,该系统可以使得接收端输出电压在 锂电池整个充电过程中恒定不变;该系统可以允许接收线圈在轴向偏移 25 mm 内、横向偏移 22 mm 内、翻转角度 80°内进行有 限姿态变化,使得患者可以在充电过程中适量运动,大大提高了经皮能量传输系统的稳定性与可靠性,对人工肛门括约肌系统 的进一步应用有重要意义。     

Investigations into the effect of tool shapes with size factor consideration in sink electrical discharge machining (EDM) process

In sink electric discharge machining (EDM) process, the tool shape and size along with wear are of great importance because they adversely affect the accuracy of machined features. This paper presents the application of response surface methodology (RSM) for investigating the effect of tool shapes such as triangular, square, rectangular, and circular with size factor consideration along with other process parameters like discharge current, pulse on-time, pulse off-time, and tool area. The RSM-based mathematical models of material removal rate (MRR) and tool wear rate (TWR) have been developed using the data obtained through central composite design. The analysis of variance was applied to verify the lack of fit and adequacy of the developed models. Further, the confirmation tests were performed to ascertain the accuracy of the developed models. The investigations revealed that the best tool shape for higher MRR and lower TWR is circular, followed by triangular, rectangular, and square cross sections. From the parametric analysis, it is also observed that the interaction effect of discharge current and pulse on-time is highly significant on MRR and TWR, whereas the main factors such as pulse off-time and tool area are statistically significant on MRR and TWR.     

Self-powered wireless thermoelectric sensors

Sensors capable of measuring various performance parameters of an operational power generation unit could help improve system performance and overall efficiencies. For example, measurement of temperatures, temperature differences, or exhaust gas concentrations could provide both a quick quantitative and qualitative assessment of system health and allow for operation of power units with smaller safety margins and therefore higher efficiencies. For this study a technique is presented that can transmit data about an operational system wirelessly in real-time to an external location. For these experiments thermoelectric element leads were connected to a solenoid coil. When the thermoelectric was exposed to a temperature difference a current was generated in the thermoelectric and solenoid coil resulting in a magnetic field. A receiver was then used to measure the changes in magnetic field of the system. Two primary configurations were developed to test this wireless sensor configuration: dynamic and static. For dynamic measurements a pendulum and pneumatic air cylinder were used to simulate a moving component that may pass the external Hall sensor such as a fan or turbine blade. For dynamic measurements it was determined that for accurate results it is very important to maintain the distance constant between the Hall sensor and solenoid coil. For stationary measurements the temperature difference across the thermoelectric was related to output measurements from the Hall sensor. Overall, results show that data can be wirelessly transmitted to an external location using this method.     

Characteristic investigation of pipe cutting technology based on electro-discharge machining

Pipe cutting technology plays an important role in the process of offshore platforms decommissioning, as many devices such as tubing, drill pipe, and casing need to be decommissioned. In this study, a novel cutting pipe technology based on electro-discharge machining (EDM) is proposed, and a cutting pipe mechanism is developed to cut the pipes for decommissioning offshore platforms. The machining principles and characteristics of the technique are described. The effects of machining parameters, including tool polarity, dielectric fluid, electrode material and width, pulse on-time, pulse off-time, peak voltage, and electrode rotation speed to machining performance, are investigated. The material removal rate (MRR) of the machined casing and tool electrode wear ratio (EWR) is obtained based on the calculation of the percentage of mass loss per machining time. The experimental results show that a better cutting performance can be obtained with negative tool polarity at the conditions of dielectric fluid of emulsion, pulse on-time of 500 μs, pulse off-time of 200 μs, peak voltage of 70 V, copper electrode width of 28 mm, and electrode rotation speed of 250 rpm is a better choice. Additionally, the cutting slots surface has been investigated by the means of SEM. The cutting slots machined by the rotary EDM are clean and smooth.     

基于多传感器和4G通信的真空断路器监测系统设计

为了实现对真空断路器由人工定期检修到实时状态检修的转变,文中设计了一种真空断路器监测系统。系统以STM32F103为微处理器,搭载位移传感器、加速度传感器、霍尔电流传感器和压力传感器,对真空断路器触头位移量、机械振动量、线圈电流量及触头接触压力量进行实时监测。采用EC20作为4G通信模块,将实时数据传输给上位机,实现人机交互。诊断系统根据特征波形进行故障分析,最终判断故障原因。实验结果表明,系统可以对真空断路器进行实时监测和故障诊断,确保断路器发生故障时能够及时维修。     

Experimental research on electrical discharge machining characteristics of engineering ceramics with different electrical resistivities

Electrical discharge machining (EDM) is the extensively used nonconventional material removal process for machining engineering ceramics provided they are electrically conductive. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics that can be machined effectively by EDM. This paper investigates the effects of the electrical resistivity and the EDM parameters on the EDM performance of ZnO/Al₂O₃ ceramic in terms of the machining efficiency and the quality. The experimental results showed that the electrical resistivity and the EDM parameters such as pulse on-time, pulse off-time, and peak current had the great influence on the machining efficiency and the quality during electrical discharge machining of ZnO/Al₂O₃ ceramic. Moreover, the electrical resistivity of the ZnO/Al₂O₃ ceramic, which could be effectively machined by EDM, increased with increasing the pulse on-time and peak current and with decreasing the pulse off-time, respectively. Furthermore, the ZnO/Al₂O₃ ceramic with the electrical resistivity up to 3,410 Ω cm could be effectively machined by EDM with the appropriate machining condition.