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排序方式: 共有174条查询结果,搜索用时 31 毫秒
1.
Overhead line energization can be performed under normal or faulty conditions. The latter indicates an occurrence of a fault along the line that exists at the moment of energization. This can lead to significant over-voltages that could endanger proper line operation. The issue gets more complex to protective devices when it comes to high-resistance faults, which impair the ability of relays to react promptly and accurately. Consequently, installation of additional detection devices becomes necessary. This paper proposes a novel method that properly detects and classifies line operating conditions at the moment of energization. The method is designed to be useful for utilities and it can be considered as a low-cost, fast, and accurate detection and classification approach, suitable for dealing with both low-resistance and high-resistance faults. Through comprehensive mathematical modeling it was found that both normal and faulty conditions during line energization are accompanied by the zero-sequence voltages of specific characteristics. The differences between zero voltage sequences are reflected in harmonic content, magnitudes of dominant frequencies, and their phase angles in regard to supply voltage. These findings are taken as the method's detection and classification criteria. The validity of the proposed model is verified by simulations and by field measurements. 相似文献
2.
Huang Zixin Dutta Saikat Misailovic Sasa 《Innovations in Systems and Software Engineering》2022,18(3):369-384
Innovations in Systems and Software Engineering - We present AQUA, a new probabilistic inference algorithm that operates on probabilistic programs with continuous posterior distributions. AQUA... 相似文献
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采用假单胞菌脂肪酶Pseudomonas sp.ECU1011催化乙酰基邻氯扁桃酸进行不对称水解,利用突变后的扁桃酸消旋酶(V29I)对拆分后的产物S-(-)-邻氯扁桃酸进行消旋,消旋后的邻氯扁桃酸经过酰化重新被利用到水解反应中,实现了酶法动态动力学拆分制备R-(-)-乙酰基邻氯扁桃酸。通过对拆分反应、拆分混合物的分离回收以及消旋反应的工艺优化,最终获得光学纯度ee>99.9%的R-(-)-乙酰基邻氯扁桃酸,其收率达80%。本研究建立的R-(-)-乙酰基邻氯扁桃酸的动态动力学拆分工艺,对其工业化应用具有重要的指导意义。 相似文献
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提出一种基于小信号的噪声模型,在精确提取0.13 μm MOSFET的小信号参数后,结合Pospieszalsik和pucel模型,运用噪声相关矩阵转换技术提取出所有噪声参数。利用ADS建立噪声模型,在2~20 GHz频率范围内,仿真结果与测量结果吻合良好,验证了模型的准确性。 相似文献
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Kimikazu Sasa Tsutomu Takahashi Yuki Tosaki Yuki Matsushi Keisuke Sueki Michiko Tamari Takahiro Amano Toshiyuki Oki Shozo Mihara Yoshihiro Yamato Yasuo Nagashima Kotaro Bessho Norikazu Kinoshita Hiroshi Matsumura 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(7-8):871-875
We present the current status and research programs of a multinuclide accelerator mass spectrometry (AMS) system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system), Japan. A maximum terminal voltage of 12 MV is available for the AMS system. The Tsukuba AMS system can measure environmental levels of long-lived radioisotopes of 14C, 26Al, 36Cl and 129I by employing a molecular pilot beam. Recently, enhancements in AMS techniques and equipment, including sample preparation, the ion source and the data acquisition system, have improved the performance of 36Cl-AMS. The standard deviation of fluctuations is typically ±2%, and the machine background level for the 36Cl/Cl ratio is lower than 1 × 10?15 with a halite sample. We have measured over 500 samples in 1 year, including samples for earth and environmental sciences and nuclear safety research. 相似文献
8.
Bojan Joki? Miodrag Mitri?Velimir Radmilovi? Sasa Drmani?Rada Petrovi? Djordje Jana?kovi? 《Ceramics International》2011,37(1):167-173
High temperature hydrothermal syntheses, using calcium nitrate tetrahydrate, sodium dihydrogen phosphate and urea as precursors, and characterization of hydroxyapatite (HAp) whiskers are reported herein. The morphology and chemical composition of the crystals from a monetite to a hydroxyapatite phase were controlled by varying the starting concentrations of the precursors and the solution pH through the amount of urea that is decomposed during heating. X-ray diffraction (XRD) analysis, infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) were used to investigate the products of the syntheses in order to find the optimum reaction conditions for obtaining the desired morphology and phase composition. Different morphologies ranging from single crystals of monetite through rods and plates of hydroxyapatite with different size distribution to whisker-like single hydroxyapatite crystal were achieved by simply varying the starting concentration of urea. Structural refinement of the hydroxyapatite whiskers confirmed a strong preferential orientation along the c-axis direction of the hexagonal crystal structure, which was significantly different from the usually observed random crystal orientation. TEM and SEM analysis of the apatite whiskers confirmed single crystal structure with the a c-axis orientation parallel to the long axis of the whiskers, with sizes up to 150 μm in length, 10 μm in width and with a thickness of about 300 nm, that grew from the same centre of nucleation, forming flaky-like particles. 相似文献
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High-speed n-InAlAs/InGaAs HEMT large-scale integrated circuits must have uniform device parameters. A selectively dry-etched n+ -GaAs/N-InAlAs/InGaAs HEMT which has a very uniform threshold voltage is discussed. Despite the high dislocation density at the n+-GaAs layer, its performance is excellent. For a gate length of 0.92 μm, the maximum transconductance of the HEMT is 390 mS/mm. The measured current-gain cutoff frequency is 23.7 GHz, and the maximum frequency of oscillation is 75.0 GHz. The standard deviation of the threshold voltage across a 2-in wafer is as low as 13 mV 相似文献
10.
Shalini Kot Subha Karumuthil-Melethil Evan Woodley Violeta Zaric Patrick Thompson Zhilin Chen Erik Lykken John G. Keimel William F. Kaemmerer Steven J. Gray Jagdeep S. Walia 《International journal of molecular sciences》2021,22(13)
GM2 gangliosidosis disorders are a group of neurodegenerative diseases that result from a functional deficiency of the enzyme β-hexosaminidase A (HexA). HexA consists of an α- and β-subunit; a deficiency in either subunit results in Tay–Sachs Disease (TSD) or Sandhoff Disease (SD), respectively. Viral vector gene transfer is viewed as a potential method of treating these diseases. A recently constructed isoenzyme to HexA, called HexM, has the ability to effectively catabolize GM2 gangliosides in vivo. Previous gene transfer studies have revealed that the scAAV9-HEXM treatment can improve survival in the murine SD model. However, it is speculated that this treatment could elicit an immune response to the carrier capsid and “non-self”-expressed transgene. This study was designed to assess the immunocompetence of TSD and SD mice, and test the immune response to the scAAV9-HEXM gene transfer. HexM vector-treated mice developed a significant anti-HexM T cell response and antibody response. This study confirms that TSD and SD mouse models are immunocompetent, and that gene transfer expression can create an immune response in these mice. These mouse models could be utilized for investigating methods of mitigating immune responses to gene transfer-expressed “non-self” proteins, and potentially improve treatment efficacy. 相似文献