期刊文献+
共找到60篇文章
< 1 2 3 >
每页显示 20 50 100
控制阀的故障保位
1
作者 冯华 《化工设计通讯》 CAS 2019年第2期112-112,共1页
重要控制回路在故障时的保位一直是一个重要的问题,随着工程技术的发展,保位的意义没有发生变化,但保位的方法却一直在发展中,对目前保位方法的实现进行了研究。
关键词 保位 保位 故障保位
下载PDF
调节阀的故障保位 被引量:4
2
作者 王福珍 《石油化工自动化》 CAS 2011年第2期54-56,59,共4页
为满足现代化生产装置对自控系统提出的安全控制、精细控制的高性能要求,结合工作实践中的工程实例,对特殊控制要求的控制系统的执行机构调节阀的故障形式:断电、断气、断信号进行"三断"保位,以保障整个装置生产的稳定性和连... 为满足现代化生产装置对自控系统提出的安全控制、精细控制的高性能要求,结合工作实践中的工程实例,对特殊控制要求的控制系统的执行机构调节阀的故障形式:断电、断气、断信号进行"三断"保位,以保障整个装置生产的稳定性和连续性,减少不必要的停产和相应的经济损失。就化工生产中常见的气动调节阀门,分别从调节阀的断电、断气、断信号三个方面阐述了各自保位的工作原理、相应的硬件配置及工作原理,并列举调节阀的故障保位方案进行佐证。 展开更多
关键词 故障保位 分散型控制系统 保位 闭锁阀
下载PDF
控制阀的保位方法分析 被引量:1
3
作者 邢新刚 《医药工程设计》 2003年第4期36-37,共2页
重要控制回路在故障时的保位一直是一个重要的问题,随着工程技术的发展,保位的意义没有发生变化,但保位 的方法却一直在发展中,本文就目前保位方法的实现作一探讨。
关键词 控制阀 保位方法 控制回路 故障处理
下载PDF
勺管保位控制系统在核电厂电动给水泵系统上的应用 被引量:1
4
作者 连建国 张世伟 孙明远 《中小企业管理与科技》 2018年第23期169-171,共3页
国内部分核电厂电动给水泵系统(APA)采用了德国福伊特公司(Voith)的未带勺管保卫功能的液力耦合调速系统,当该液力耦合调速系统出现例如勺管位置整定值断线等特定故障时会出现勺管直接降到最小位置,造成给水泵转速下降无法给蒸汽发生器... 国内部分核电厂电动给水泵系统(APA)采用了德国福伊特公司(Voith)的未带勺管保卫功能的液力耦合调速系统,当该液力耦合调速系统出现例如勺管位置整定值断线等特定故障时会出现勺管直接降到最小位置,造成给水泵转速下降无法给蒸汽发生器正常供水,不利于核电厂的安全运行;研究增加液力耦合器勺管保位功能能在特定故障模式下保证勺管保持在当前位置,可有效增加电动给水泵给蒸汽发生器供水的可靠性。 展开更多
关键词 液力耦合调速系统 勺管 保位控制 电动给水泵(APA)
下载PDF
调节阀“三断”保位方案在焦化厂的应用
5
作者 蔡海峰 《自动化应用》 2014年第2期21-22,共2页
根据厂区所使用的调节阀自身具备的功能以及生产工艺需求,选择合适的(三断)保位方案,分析了所选择方案的工作原理及优、缺点及适用条件。
关键词 三断保位 调节阀 阀门定位器 空气锁闭阀 电磁换向阀 失电比较器
下载PDF
气动调节阀保位系统在原油管道上的应用探究
6
作者 徐俊平 《装备维修技术》 2021年第2期57-57,共1页
为了确保原油管道可以安全且平稳运行,不仅需要对输油管道设置合理的运行压力,还需使用气动调节阀来对输油站场管道的进出站压力以及管道压力波进行自动调节。对于原油管道输送工艺中的气动调节阀,其中一个重要的要求就是调节阀在出现... 为了确保原油管道可以安全且平稳运行,不仅需要对输油管道设置合理的运行压力,还需使用气动调节阀来对输油站场管道的进出站压力以及管道压力波进行自动调节。对于原油管道输送工艺中的气动调节阀,其中一个重要的要求就是调节阀在出现故障的时候本身必须处在保位状态。实现调节阀的故障保位功能,才能使气动调节阀在原油管道中可以有效使用,保障输油管道安全平稳的运行。 展开更多
关键词 气动调节阀 保位系统 原油管道
下载PDF
Effect and mechanism of on-chip electrostatic discharge protection circuit under fast rising time electromagnetic pulse
7
作者 Mao Xinyi Chai Changchun +3 位作者 Li Fuxing Lin Haodong Zhao Tianlong Yang Yintang 《强激光与粒子束》 CAS CSCD 北大核心 2024年第10期44-52,共9页
The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with ... The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit. 展开更多
关键词 fast rising time electromagnetic pulse damage effect electrostatic discharge protection circuit damage location prediction
下载PDF
Research Progress on the Protection of Wild Rice Resources in China 被引量:1
8
作者 张金伟 谢建坤 万勇 《Agricultural Science & Technology》 CAS 2010年第2期95-97,共3页
[Objective] The research aimed to summarize the research progresses on the protection of wild rice resources in China in recent 20 years.[Method] The protection effects of wild rice by using the methods of in situ pro... [Objective] The research aimed to summarize the research progresses on the protection of wild rice resources in China in recent 20 years.[Method] The protection effects of wild rice by using the methods of in situ protection,ectopic protection,the combination of in situ protection and ectopic protection were expounds,the research progresses on the protection of wild rice resources at present were summarized.[Result] Some scholars thought that in situ protection was an effective way for the protection of wil... 展开更多
关键词 Wild rice In situ protection Ectopic protection
下载PDF
关于我国开设石油期货交易品种的可行性探讨 被引量:8
9
作者 陈怀东 《国际石油经济》 2003年第4期41-43,共3页
期货市场有两个主要功能:即发现远期价格和套期保值、规避风险。尽管从远期看我国开设石油期货交易品种是大势所趋,但是由于我国石油市场还是一个有限开放、竞争并不十分充分的市场,因此,目前国内总体上尚不具备设立石油期货的市场条件... 期货市场有两个主要功能:即发现远期价格和套期保值、规避风险。尽管从远期看我国开设石油期货交易品种是大势所趋,但是由于我国石油市场还是一个有限开放、竞争并不十分充分的市场,因此,目前国内总体上尚不具备设立石油期货的市场条件。目前,较为现实的尝试是选取市场竞争比较充分的燃料油进行期货试点工作,为今后条件成熟时推出原油和汽柴油期货交易品种提供经验。 展开更多
关键词 中国 石油市场 期货交易品种 可行性 套期保位 价格风险 政策法规
下载PDF
岭澳二期核电站电动主给水泵系统调速原理的改进 被引量:4
10
作者 牛云 赵东升 +1 位作者 黄新帅 柴大虎 《核科学与工程》 CAS CSCD 北大核心 2019年第1期78-82,共5页
针对在多种故障模式下,岭澳二期核电站电动主给水泵系统不能稳定在当前转速的问题,在结合系统调速功能、原理、软硬件配置与故障报警的基础上,对现有调速原理进行了改进。增加保位电磁阀,重设油路;将勺管位置传感器电流值反馈至手/自动... 针对在多种故障模式下,岭澳二期核电站电动主给水泵系统不能稳定在当前转速的问题,在结合系统调速功能、原理、软硬件配置与故障报警的基础上,对现有调速原理进行了改进。增加保位电磁阀,重设油路;将勺管位置传感器电流值反馈至手/自动控制程序;串接可编程控制器的模拟量输出通道至输入通道,以及新增主控报警提醒。该方案能够解决多种故障模式下主给水泵转速剧烈下降并失去控制的问题,也为国内其他电站类似改进提供了值得借鉴的方法。 展开更多
关键词 电动主给水泵系统 液力耦合器 勺管 保位
下载PDF
半山公司燃气轮机控制阀的(三断)保护方案及分析
11
作者 刘晟 《科技风》 2016年第16期126-126,共1页
本文阐述了杭州半山公司热工控制中涉及到的控制阀三断保护中的几种方案,分析了各方案的工作原理及优、缺点及适用条件。
关键词 三断保护 控制阀 保位 电磁换向阀
下载PDF
Fabrication and Electromechanical Characteristics of 2×2 Torsion-Mirror Optical Switch Arrays with Monolithically Integrated Fiber Self-Holding Structures
12
作者 吴文刚 郝一龙 +2 位作者 栗大超 张培玉 武国英 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2002年第10期1024-1030,共7页
Novel 2×2 torsion-mirror optical switch arrays are fabricated by using the mixed micromachining based on the surface and bulk silicon microelectronics,then are investigated electromechanically in applied direct a... Novel 2×2 torsion-mirror optical switch arrays are fabricated by using the mixed micromachining based on the surface and bulk silicon microelectronics,then are investigated electromechanically in applied direct and alternating electric fields.When the thickness of the elastic torsion beams suspending the aluminum coated polysilicon micro-mirrors of the switches in the arrays is about 1μm,the electrostatic yielding voltages for driving the mirrors to achieve their ON-state are in the range of 270~290V,and the minimum holding voltages for mirrors ON-state are found as 55V or so.Theoretical analysis manifests that the yielding voltage is more sensitive to beam thickness than other design parameters do about the torsion-mirror switch structures.The lifetime can reach 10 8 times.The estimated shortest switching time of the switches at least lasts for less than 2ms.The force analysis on the two kinds of new fiber self-holding structures integrated monolithically in the chip of the optical switch arrays indicates that the structures can feature self-fixing and self-aligning of optical fibers. 展开更多
关键词 MEMS optical switch torsion-mirror fiber self-holding structures mixed micromachining
下载PDF
Effect of NGF on c-fos mRNA Expression in Spinal Neuron after Spinal Cord Injury
13
作者 苏振刚 曹晓建 罗永湘 《Journal of Nanjing Medical University》 2003年第4期183-186,共4页
Objective: To expound the mechanism of nerve growth factor (NGF) to protectspinal cord against injury. Methods: Forty-five rats with 10 g X 2. 5 cm impact T_8 spinal cordinjury (SCI) were divided into 3 groups. The ex... Objective: To expound the mechanism of nerve growth factor (NGF) to protectspinal cord against injury. Methods: Forty-five rats with 10 g X 2. 5 cm impact T_8 spinal cordinjury (SCI) were divided into 3 groups. The experimental animals received 60 g NGF purified frombovine seminal plasma instantly, 1, 2, 4 h after in jury and an equal volume of normal saline wasgiven to the control group at the same time. The c-fos mRNA levels were detected by in situhybridization. Results: The results showed no evident c-fos expression in normal control group. Thec-fos expression increased markedly in damaged neurons. The peak value of c-fos mRNA arose at 1 h,and c-fos levels in NGF group reduced evidently. Conclusion: NGF could inhibit c-fos expression. Itmay serve as one of the action mechanisms of NGF to protect spinal cord against injury. 展开更多
关键词 spinal cord NEURON injury c-fos mRNA nerve growth factor
下载PDF
液压促动器控制系统设计与性能分析
14
作者 刘兵 王超光 +3 位作者 王建任 于安才 赵斌 张建 《机床与液压》 北大核心 2017年第8期102-104,110,共4页
介绍了液压促动器控制系统的集成化结构、PROFIBUS-DP通信和闭环控制策略,并对数千个样品进行闭环控制、保位和变负载随动实验。经过大量实验证明了促动器定位精度及动态性能可完全满足项目的需求,结构合理,具有良好的实用性。
关键词 液压促动器 闭环控制 保位 变负载
下载PDF
气动调节阀在氢气压缩机运行中的故障及消除
15
作者 潘登 钟国院 《氯碱工业》 CAS 2014年第11期43-45,共3页
对氢气压缩机运行中出现的气动调节阀的气源管脱落、定位器反馈杆断裂等问题,进行了技术改造。改造后,降低了因阀门故障导致生产系统的停车次数,保障了系统的安全稳定运行。
关键词 气动调节阀 氢气压缩机 气源管 定位器 保位
下载PDF
西门子汽轮机低压缸阀位故障机组控制优化改进
16
作者 杜春城 李华欢 《中国核电》 2022年第4期550-554,共5页
本文通过对某厂西门子汽轮机低压缸阀门控制逻辑进行分析,研究低压缸阀门控制与机组状态的关系,针对原低压缸阀门阀位反馈故障时将缓慢关闭影响机组效率,且低压缸阀门阀位反馈存在单一通道故障引起机组异常的问题。本文针对并网期间低... 本文通过对某厂西门子汽轮机低压缸阀门控制逻辑进行分析,研究低压缸阀门控制与机组状态的关系,针对原低压缸阀门阀位反馈故障时将缓慢关闭影响机组效率,且低压缸阀门阀位反馈存在单一通道故障引起机组异常的问题。本文针对并网期间低压缸阀门阀位故障提出保位的改进建议,并全面深入分析对机组状态的影响和可行性。其改进措施可有效避免单一故障引起机组功率损失的问题,保证机组稳定运行。 展开更多
关键词 低压缸 保位 单一故障 改进
下载PDF
Privacy-Preserving Relative Location Based Services for Mobile Users 被引量:4
17
作者 Fei Ning Zhuang Yi +2 位作者 GU Jingjing Cao Jiannong Yang Liang 《China Communications》 SCIE CSCD 2015年第5期152-161,共10页
Location-aware applications have been used widely with the assistance of the latest positioning features in Smart Phone such as GPS,AGPS,etc.However,all the existing applications gather users' geographical data an... Location-aware applications have been used widely with the assistance of the latest positioning features in Smart Phone such as GPS,AGPS,etc.However,all the existing applications gather users' geographical data and transfer them into the pertinent information to give meaning and value.For this kind of solutions,the user's privacy and security issues might be raised because the geographical location has to be exposed to the service provider.A novel and practical solution is proposed in this article to provide the relative location of two mobile users based on their WiFi scanned results without any additional sensors.There is no privacy concern in this solution because end users will not collect and send any sensitive information to the server.This solution adopts a Client/Server(C/S) architecture,where the mobile user as a client reports the ambient WiFi APs and the server calculates the distances based on the WiFi AP's topological relationships.A series of technologies are explored to improve the accuracy of the estimated distance and the corresponding algorithms are proposed.We also prove the feasibility with the prototype of "Circle Your Friends" System(CYFS) on Android phone which lets the mobile user know the distance between him and his social network friends. 展开更多
关键词 relative location privacy-preserv-ing CYFS
下载PDF
Entanglement Capacity of Two-Qubit Unitary Operator with the Help of Auxiliary System 被引量:2
18
作者 HU Bao-Lin DI Yao-Min 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第6期1029-1032,共4页
The'entanglement capacity of general two-qubit unitary operators is studied when auxiliary systems are allowed, and the analytical results based on linear entropy when input states are disentangled are given. From th... The'entanglement capacity of general two-qubit unitary operators is studied when auxiliary systems are allowed, and the analytical results based on linear entropy when input states are disentangled are given. From the results the condition for perfect entangler, α1 = α2 = π/4, is obtained. Contrary to the case without auxiliary system, the parameter α3 may play active role to the entanglement capacity when auxiliary systems are allowed. 展开更多
关键词 unitary operator entanglement capacity linear entropy auxiliary system
下载PDF
Hepatoprotective effect of manual acupuncture at acupoint GB34 against CCl_4-induced chronic liver damage in rats 被引量:3
19
作者 Yun-Kyoung Yim Hyun Lee +4 位作者 Kwon-Eui Hong Young-Il Kim Byung-Ryul Lee Tae-Han Kim Ji-Young Yi 《World Journal of Gastroenterology》 SCIE CAS CSCD 2006年第14期2245-2249,共5页
AIM: To investigate the hepatoprotective effect of manual acupuncture at Yanglingquan (GB34) on CCl4-induced chronic liver damage in rats. METHODS: Rats were injected intraperitoneally with CCh (1 mL/kg) and tre... AIM: To investigate the hepatoprotective effect of manual acupuncture at Yanglingquan (GB34) on CCl4-induced chronic liver damage in rats. METHODS: Rats were injected intraperitoneally with CCh (1 mL/kg) and treated with manual acupuncture using reinforcing manipulation techniques at left GB34 (Yanglingquan) 3 times a week for 10 wk. A nonacupoint in left gluteal area was selected as a sham point. To estimate the hepatoprotective effect of manual acupuncture at GB34, measurement of liver index, biochemical assays including serum ALT, AST, ALP and total cholesterol, histological analysis and blood cell counts were conducted. RESULTS: Manual acupuncture at GB34 reduced the liver index, serum ALT, AST, ALP and total cholesterol levels as compared with the control group and the sham acupuncture group. It also increased and normalized the populations of WBC and lymphocytes. CONCLUSION: Manual acupuncture with reinforcing manipulation techniques at left GB34 reduces liver toxicity, protects liver function and liver tissue, and normalizes immune activity in CCh-intoxicated rats. 展开更多
关键词 Manual acupuncture Yanglingquan (GB34) CCl4-induced liver damage Hepatoprotective effect
下载PDF
Improvement of hydrogen embrittlement and stress corrosion cracking by annealing for Al-4.4Mg-0.6Mn alloy 被引量:1
20
作者 Seong-Jong KIM Min-Su HAN +1 位作者 Seong-Kweon KIM Seok-Ki JANG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第A01期17-22,共6页
With no annealing treatment, cathodic polarization trends in 5083F A1 alloy revealed concentration polarization and activation polarization. However, the annealed specimens have lower current densities at corrosion pr... With no annealing treatment, cathodic polarization trends in 5083F A1 alloy revealed concentration polarization and activation polarization. However, the annealed specimens have lower current densities at corrosion protection potential compared to the non-annealed specimen. The results of SSRTs conducted in seawater at the applied potential range of-l.8 V to -0.5 V indicated that the maximum tensile strength, elongation, and time-to-fracture had high values at applied potentials of -0.7 to -1.4 V. The maximum tensile strength, elongation, and time-to-f?acture decreased when the potential values were beyond this range in either anodic or cathodic direction. In general, the increased shear lip caused by annealing treatment indicates elongation. Time-to-fracture would likely increase with elongation. Potentials between -0.5 V to -0.6 V were found to be in the region of stress corrosion cracking. The corrosion protection zone was determined to be -0.7 V to -J,4 V because these potential ranges produced good mechanical properties. Potential less than -1.4 V produced a fractured surface with a mixture of dimples (ductile fractures) and a quasi-cleavage pattern resulting from the effects of hydrogen gas. 展开更多
关键词 ANNEALING 5083F A1-Mg alloy corrosion seawater slow strain rate tests
下载PDF
上一页 1 2 3 下一页 到第
使用帮助 返回顶部