共查询到20条相似文献,搜索用时 140 毫秒
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针对直流逆变电阻焊机焊接电流精确测量的需求,提出基于光纤电流传感技术的焊接电流测量方法。建立了光纤电流传感器闭环检测系统动态模型,通过优化系统的前向增益,提升了传感器响应速度和带宽。仿真和实验结果表明:传感器的上升时间约为4.1 μs,在DC~30kHz范围内幅频特性衰减小于0.3%。基于该动态模型计算传感器对焊接电流纹波分量的响应,仿真结果表明:系统的动态跟踪能力可满足对纹波电流的测量需求。利用等安匝法对光纤电流传感器进行校准,在直流5~50kA范围内,传感器的测量误差优于±0.05%。现场实验结果证明了光纤电流传感器用于直流逆变焊接电流测量及电焊电流测试仪现场校准的可行性。 相似文献
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扩展相互作用速调管由多个重入式多间隙耦合腔构成,毫米波段高功率微波源的需求推动了Ka波段扩展互作用速调管的研制.本文采用基于微波网络理论的多间隙耦合腔输出回路间隙阻抗冷测方法,对Ka波段滤波器加载三间隙耦合腔输出回路进行冷参数测试,得到该回路的间隙阻抗频率特性曲线与群时延曲线.并将冷测结果与三维电磁场软件仿真结果进行对比,分析了两者产生异同点的原因.从阻抗频率特性的测量结果可观察到该输出回路的相对“冷”带宽达到4.3%,满足设计要求. 相似文献
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分析了高速大功率RSD(Reversely Switched Dynistor)电子开关开关暂态电流试验平台的构建原理、试验回路的简化模型和基于自积分式罗氏线圈检测系统的工作机理.为便于优化包括RSD开关暂态电流试验平台和罗氏线圈检测装置的整个系统的电气参数,利用MATLAB/SINMULINK仿真环境,建立整个系统的仿真模型,并利用该模型开展试验验证.研究表明,文章获得的描述基于自积分式罗氏线圈整个试验测试系统的仿真模型是可行的,它可以为开关试验状态电流测试试验提供一套合适的计算机仿真平台,有利于优化试验回路和检测系统的电气参数,确保试验成功. 相似文献
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直线电机驱动的微小型活塞压缩机特性分析 总被引:2,自引:0,他引:2
讨论了微小型化的直线电机驱动的活塞压缩机特性.运用电磁场有限元方法对直线电动机电磁场模型进行求解,分析了电动机内部的磁场和磁力线分布情况;建立了电动机动子动力学模型和驱动电路模型,得到系统的运行方程组并对其求解,根据计算结果对压缩机的驱动力、活塞行程、绕组电流和频率特性等进行了分析,同时就余隙容积和泄漏对这种微小型活塞压缩机的影响进行了探讨.结果表明直线电机驱动的微小型活塞压缩机在理论上是可行的,有进一步研究、优化的必要. 相似文献
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I. A. Dan’kov V. I. Ivannikov E. F. Tokarev V. N. Shekhovtsov 《Measurement Techniques》2010,53(1):23-27
Constructions for high-temperature acoustic transducers of submersible and clamped types, and a bench for testing them, are
described. Transducer technical characteristics are provided and the fields of their potential practical application are indicated. 相似文献
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Ludwig R Lord W 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1988,35(6):809-820
The authors present a finite-element formulation for an overall ultrasonic NDT (nondestructive testing) system, including appropriate models for transmitter and receiver transducers. Transducer considerations are discussed. Results are given for two-dimensional plane-strain geometry simulations that agree qualitatively with corresponding experimental measurements and show the potential of the method. 相似文献
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Steven E. Fick Thomas M. Proctor 《Journal of research of the National Institute of Standards and Technology》2011,116(6):821-826
The National Institute of Standards and Technology (NIST) Conical Reference Transducer (CRT) is designed for purposes requiring frequency response characteristics much more uniform than those attainable with ultrasonic transducers conventionally used for acoustic emission (AE) nondestructive testing. The high performance of the CRT results from the use of design elements radically different from those of conventional transducers.The CRT was offered for sale for 15 years (1985 to 2000). Each CRT was furnished with data which expressed, as a function of frequency, the transducer sensitivity in volts per micrometer of normal displacement on the test block. Of the 22 transducers constructed, eight were reserved for long term research and were stored undisturbed in a laboratory with well controlled temperature and humidity. In 2009, the sensitivities of these eight units were redetermined. The 2009 data have been compared with data from similar tests conducted in 1985. The results of this comparison verify the claim “Results of tests of the long term stability of CRT characteristics indicate that, if proper care is taken, tens of years of service can reasonably be expected.” made in the CRT specifications document furnished to prospective customers. 相似文献
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目的为了客观准确地将目标用户认知需求转化为产品技术特性的设计要求,提升可移动电力检测设备目标用户认知需求满意度及明确产品创新方向,提出QFD和FBS集成的创新设计模式。方法首先,通过访谈和问卷调研获取用户需求,借助AHP法求解用户认知需求权重;其次,运用QFD法构建质量屋,明确可移动电力检测设备待改进的关键技术特性指标;最后,将用户旅程图引入FBS的功能—行为—结构展开模型中,以解决可移动电力检测设备的关键技术特性问题,指导产品创新设计。结论QFD与FBS理论的融合应用能够将用户认知需求精准转化为技术特性层面的设计要求,对可移动电力检测设备的人机、造型、功能、收纳等方面的不足提出了相应的解决方案,实现了用户认知需求与产品技术特性之间的映射转换,证明了该方法具有可行性。 相似文献
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Erez Shmueli Ronen Mansuri Matan Porcilan Tamar Amir Lior Yosha Matan Yechezkel Tal Patalon Sharon Handelman-Gotlib Sivan Gazit Dan Yamin 《Journal of the Royal Society Interface》2021,18(181)
Current COVID-19 screening efforts mainly rely on reported symptoms and the potential exposure to infected individuals. Here, we developed a machine-learning model for COVID-19 detection that uses four layers of information: (i) sociodemographic characteristics of the individual, (ii) spatio-temporal patterns of the disease, (iii) medical condition and general health consumption of the individual and (iv) information reported by the individual during the testing episode. We evaluated our model on 140 682 members of Maccabi Health Services who were tested for COVID-19 at least once between February and October 2020. These individuals underwent, in total, 264 516 COVID-19 PCR tests, out of which 16 512 were positive. Our multi-layer model obtained an area under the curve (AUC) of 81.6% when evaluated over all the individuals in the dataset, and an AUC of 72.8% when only individuals who did not report any symptom were included. Furthermore, considering only information collected before the testing episode—i.e. before the individual had the chance to report on any symptom—our model could reach a considerably high AUC of 79.5%. Our ability to predict early on the outcomes of COVID-19 tests is pivotal for breaking transmission chains, and can be used for a more efficient testing policy. 相似文献
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针对直线交变冲击机构高频、高速、难以检测的特点,提出了基于电磁感应原理的检测方法,完成了对直线交变冲击机构的冲击特性检测。基于ANSYS Maxwell软件建立了检测系统电磁场仿真模型。通过仿真计算与试验结果的对比分析,验证了电磁感应检测方法的可行性以及电磁仿真模型的正确性。进一步,分析了气缸材料、线圈匝数、线圈柱面径向位置等不同参数对磁电式速度传感装置性能的影响。研究结论为方便、准确地测量气驱直线交变冲击机构冲击特性参数提供了有效依据。 相似文献
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Dahl JJ Pinton GF Palmeri ML Agrawal V Nightingale KR Trahey GE 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(2):301-312
Radiation force-based techniques have been developed by several groups for imaging the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one such method that uses commercially available scanners to generate localized radiation forces in tissue. The response of the tissue to the radiation force is determined using conventional B-mode imaging pulses to track micron-scale displacements in tissue. Current research in ARFI imaging is focused on producing real-time images of tissue displacements and related mechanical properties. Obstacles to producing a real-time ARFI imaging modality include data acquisition, processing power, data transfer rates, heating of the transducer, and patient safety concerns. We propose a parallel receive beamforming technique to reduce transducer heating and patient acoustic exposure, and to facilitate data acquisition for real-time ARFI imaging. Custom beam sequencing was used with a commercially available scanner to track tissue displacements with parallel-receive beamforming in tissue-mimicking phantoms. Using simulations, the effects of material properties on parallel tracking are observed. Transducer and tissue heating for parallel tracking are compared to standard ARFI beam sequencing. The effects of tracking beam position and size of the tracked region are also discussed in relation to the size and temporal response of the region of applied force, and the impact on ARFI image contrast and signal-to-noise ratio are quantified. 相似文献
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研究借助气动-声学风洞试验平台,首先针对某高速列车的1:8缩尺比例的三车编组模型建立了气动噪声试验方法和突显不同的噪声源的模型处理方法,并结合流场外自由场传声器和传声器阵列的测量结果,分析了模型上的主要噪声源特性及对整个模型的贡献量大小。研究表明:转向架和受电弓噪声是模型的最主要噪声源,其次是车连接部位间隙,再次是鼻尖和排障器,最后是尾车,同时,并给出了这些噪声源的特性,这对于认识高速列车气动噪声和改善设计有重要的参考价值。研究也说明所提出的试验研究方法是一种研究高速列车气动噪声较为有效地方法。 相似文献