Study of Ablation of Arc Contacts and Dynamic Contact Resistance in High Current Breaker

Licheng Xing,Xiaodong Zhang,Qingbin Tong,Gaoqi Xing 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3

The fault of power circuit breaker (PCB) can lead very serious problems, especially in high voltage–power grid. The structure of contacts may be composed of main contacts and arc contacts, and this structure can avoid ablation of main contacts efciently. It is necessary to study the eroded state of the arc contacts and the dynamic contact resistance of arc contacts to estimate the operating state of the PCB. The wear of contacts contains arc ablation and mechanical wear through the characteristics of contacts. The arc ablation is caused by the high temperature of the arc and the mechanical wear is caused by the mechanical friction of static and movable contacts. Some experiments have been done under diferent size of contacts and diferent current through them. The results show that the mechanical wear increases, sometimes heavier, with the increase of the size of fxed contacts and the decrease of the size of movable ones because the force between fxed and movable contacts becomes larger. The results also show that the ablation of arc contacts increases with the increase of current, especially when the current is up to 20 kA. With the high temperature of arc reaching the hardness point of copper, the arc ablation and mechanical erosion are increasing obviously since the contacts become soft and easy to wear. Another result of the study shows it is important to choose the material of contacts and the force between movable and fxed contacts. The harder and less resistance the material of contacts, the better the operating situation. To monitor the operating situation of the breaker, the dynamic contact resistance was measured 25 times. As a result, the dynamic contact resistance is sensitive to the current and increasing with the increase of continuous experiment time because of the increasing of metal ions. Furthermore, if the SF6 in the PCB is changes, the dynamic contact resistance would be changed. The dynamic contact resistance in this experiment varies substantially within the range of 80–250 μΩ at the current of 20 kA.

The conditional risk probability-based seawall height design method

Xing Yang,Xiaodong Hu,Zhiqing Li 대한조선학회 2015 International Journal of Naval Architecture and Oc Vol.7 No.6

The determination of the required seawall height is usually based on the combination of wind speed (or wave height) and still water level according to a specified return period, e.g., 50-year return period wind speed and 50- year return period still water level. In reality, the two variables are be partially correlated. This may be lead to overdesign (costs) of seawall structures. The above-mentioned return period for the design of a seawall depends on economy, society and natural environment in the region. This means a specified risk level of overtopping or damage of a seawall structure is usually allowed. The aim of this paper is to present a conditional risk probability-based seawall height design method which incorporates the correlation of the two variables. For purposes of demonstration, the wind speeds and water levels collected from Jiangsu of China are analyzed. The results show this method can improve seawall height design accuracy.

Design and Analysis of a Novel 16/10 Segmented Rotor SRM for 60V Belt-Driven Starter Generator

Xiaodong Sun,Zhengwang Xue,Shouyi Han,Xing Xu,Zebin Yang,Long Chen 한국자기학회 2016 Journal of Magnetics Vol.21 No.3

This paper proposes a novel 16/10 segmented rotor switched reluctance motor (SSRM) for belt-driven starter generators (BSGs). Different from conventional SRMs, the stator of the proposed SSRM consists of two types of stator poles, i.e., exciting and auxiliary poles, and the rotor is constructed from a series of discrete segments. The topology and operation principle of this proposed SSRM are illustrated firstly, and then the design rules are listed. In addition, the finite element method (FEM) is employed to get the static and dynamic characteristics of the proposed SSRM. Finally, the simulation results are presented to show the validity of the proposed SSRM for BSGs.

The 16-year experience in treating low-risk gestational trophoblastic neoplasia patients with failed primary methotrexate chemotherapy

Xiaodong Wu,Jiale Qin,Tao Shen,Weidong Fei,Lili Chen,Xing Xie,Weiguo Lu 대한부인종양학회 2020 Journal of Gynecologic Oncology Vol.31 No.4

Objective: To assess the outcomes and toxic effects of 5-day actinomycin D (Act-D) salvagetherapy and to explore the predictors of Act-D resistance in patients with low-risk gestationaltrophoblastic neoplasia (GTN)who failed 5-day methotrexate (MTX) chemotherapy. Methods: This retrospective study analyzed patients with low-risk GTN administered Act-Dsalvage therapy after failing MTX chemotherapy at Women's Hospital, School of MedicineZhejiang University between January 2000 and December 2015. The clinical parameters ofthese patients were collected and analyzed. Results: The final analysis included 89 cases. Of these, 73 cases (82.02%) responded tosalvage Act-D. The remaining 16 resistant cases were switched to etoposide, MTX, Act-D/cyclophosphamide, and vincristine chemotherapy and achieved complete remission. Serumhuman chorionic gonadotrophin levels before Act-D salvage therapy (hCGAct-D)in the Act-D resistant cases were significantly higher than those in the Act-D responders (median 605 vs. 103 IU/L, p=0.009). However, the range of hCGAct-D values in Act-D responders was wider thanthat in Act-D-resistant cases (5.76–16,664 IU/L vs. 11.43–6,732 IU/L). Thus, assigning a generalcut-off value was difficult considering the individual setting. Except for 2 cases requiring othersalvage regimens due to Act-D toxicity, 97.80% of cases (89/91) tolerated the toxicity. During atleast 1-year follow-up, the survival rate was 100.00% and no case developed recurrence. Conclusion: Based on the good therapeutic effect and tolerable toxicity, we recommendAct-D salvage therapy for all patients with low-risk GTN who fail primary MTX chemotherapy. The higher serum hCG levels before Act-D salvage therapy may be associated with resistanceto this treatment.

The conditional risk probability-based seawall height design method

Yang, Xing,Hu, Xiaodong,Li, Zhiqing The Society of Naval Architects of Korea 2015 International Journal of Naval Architecture and Oc Vol.7 No.6

The determination of the required seawall height is usually based on the combination of wind speed (or wave height) and still water level according to a specified return period, e.g., 50-year return period wind speed and 50-year return period still water level. In reality, the two variables are be partially correlated. This may be lead to over-design (costs) of seawall structures. The above-mentioned return period for the design of a seawall depends on economy, society and natural environment in the region. This means a specified risk level of overtopping or damage of a seawall structure is usually allowed. The aim of this paper is to present a conditional risk probability-based seawall height design method which incorporates the correlation of the two variables. For purposes of demonstration, the wind speeds and water levels collected from Jiangsu of China are analyzed. The results show this method can improve seawall height design accuracy.

Impedance Ground Faults Detection and Classification Method for DC Microgrid

Wang Xiaodong,Wang Ruojin,Liu Yingming,Gao Xing 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.6

Aiming at the practical engineering problem, it is easy to be confused and difficult to detect, such as the single pole high impedance ground fault and load switching of the DC microgrid. This paper proposes a method, which the impedance ground faults detection and classification method. Based on the combination of improved complete ensemble empirical mode decomposition with adaptive noise and random forest. First, the dependence of original signal is reduced by complete ensemble empirical mode decomposition with adaptive noise. Secondly, by comparing the cumulative slope sum k with the threshold, the abnormal conditions can be distinguished from the normal condition, load switching and the ground faults can be further distinguished through the energy ratio Rratio. Finally, the random forest is used to further classify the ground faults to achieve precise classification of impedance ground faults in the DC microgrid. The analysis of calculation examples shows the method, it is quickly and effectively to detect and classify impedance ground faults in DC microgrid quickly and effectively, without being affected by fault resistance, fault initiation time and fault location.

Microstructures and Mechanical Properties of Equiatomic NiTi Shape Memory Alloy Undergoing Local Canning Compression and Subsequent Annealing

Dong Sun,Shuyong Jiang,Xiaodong Xing,Bingyao Yan,Junbo Yu,Yanqiu Zhang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

Local canning compression is imposed on equiatomic NiTi shape memory alloy (SMA) with complete B19′ martensite. Afraction of retained nanocrytalline grains are embedded in the dominant amorphous phase. The compressed NiTi samples areannealed for 2 h at various temperatures, including 300, 450 and 600 °C. Grain size increases with increasing crystallizationtemperature during heat treatment. Under annealing at 300 °C, nanocrystalline grains are dominant in NiTi SMA, where thereexists local amorphous zone. Under annealing at 450 °C, almost complete nanocrystalline can be obtained. Under annealingat 600 °C, grain size increases substantially, but there still exists a small amount of nanocrystalline grains. Under annealingat 300 °C, NiTi SMA exhibits extremely high elastic limit, but its plasticity is poor. Under annealing at 450 °C, NiTi SMAexhibits very high yield stress and it simultaneously keeps high plasticity. Under annealing at 600 °C, NiTi SMA exhibitsrelatively low yield stress, but its yield stress is still higher than that of as-received NiTi SMA and its plasticity is also high.

A Novel 3-D Imaging Configuration Exploiting Synthetic Aperture Ladar

Liang Guo,Yinli Huang,Xiaozhen Li,Xiaodong Zeng,Yu Tang,Mengdao Xing 한국광학회 2017 Current Optics and Photonics Vol.1 No.6

Traditional three-dimensional (3-D) laser imaging systems are based on real aperture imaging technology,whose resolution decreases as the range increases. In this paper, we develop a novel 3-D imaging techniquebased on the synthetic aperture technology in which the imaging resolution is significantly improved anddoes not degrade with the increase of the range. We consider an imaging laser radar (ladar) system usingthe floodlight transmitting mode and multi-beam receiving mode. High 3-D imaging resolutions areachieved by matched filtering the linear frequency modulated (LFM) signals respectively in range, syntheticaperture along-track, and the real aperture across-track. In this paper, a novel 3-D imaging signal modelis given first. Because of the motion during the transmission of a sweep, the Doppler shift induced bythe continuous motion is taken into account. And then, a proper algorithm for the 3-D imaging geometryis given. Finally, simulation results validate the effectiveness of the proposed technique.

The management of hydatidiform mole with lung nodule: a retrospective analysis in 53 patients

Xiao Li,Yaping Xu,Yuanyuan Liu,Xiaodong Cheng,Xinyu Wang,Weiguo Lu,Xing Xie 대한부인종양학회 2019 Journal of Gynecologic Oncology Vol.30 No.2

Objective: To investigate the significance of lung nodule in hydatidiform mole, we retrospectively compared the clinical outcomes of those patients treated with different strategies. Methods: The patients were divided into three groups: chemotherapy immediately once lung nodule was detected (group 1, n=17), delayed chemotherapy until human chorionic gonadotrophin (hCG) level met the diagnostic criteria for gestational trophoblastic neoplasia (GTN) (group 2, n=18), and hCG surveillance alone until hCG level was normalized spontaneously (group 3, n=18). The clinical parameters of these patients were collected and analyzed. Results: Totally 53 (4.0%) patients were included from 1,323 cases with molar pregnancy during past 16 years. Among them, the diameters of lung nodules were 0.3–2.5 cm. Chemotherapy cycles for achieving hCG normalization and the failure rate of first-line chemotherapy in group 1 were significantly increased than that in group 2 (5 vs. 3 cycles, p=0.000, 58.8% vs. 11.1%, p=0.005). The hCG level of all 18 cases in group 3 was normalized spontaneously within 6 months. Of those, lung nodules of 9 patients disappeared spontaneously, accounting for 25% (9/36) of patients who initially selected observation. The proportion of single nodule in group 3 was significantly higher than that in group 2 (10/18 vs. 2/18, p=0.012). Conclusion: Our results suggest that lung nodule alone is not an adequate indication of chemotherapy in molar pregnancy. hCG surveillance is safe for patients with lung nodule, especially with single nodule, as long as their hCG levels do not meet International Federation of Gynecology and Obstetrics diagnostic criteria for GTN.

Genome-wide scan for runs of homozygosity identifies candidate genes in Wannan Black pigs

Wu Xudong,Zhou Ren,Zhang Wei,Cao Bangji,Xia Jingjing,Wang Caiyun,Zhang Xiaodong,ChuMing-Xing,Yin Zongjun,Ding Yueyun 아세아·태평양축산학회 2021 Animal Bioscience Vol.34 No.12

Objective: Runs of homozygosity (ROH) are contiguous lengths of homozygous genotypes that can reveal inbreeding levels, selection pressure, and mating schemes. In this study, ROHs were evaluated in Wannan Black pigs to assess the inbreeding levels and the genome regions with high ROH frequency.Methods: In a previous study, we obtained 501.52 GB of raw data from resequencing (10×) of the genome and identified 21,316,754 single-nucleotide variants in 20 Wannan Black pig samples. We investigated the number, length, and frequency of ROH using resequencing data to characterize the homozygosity in Wannan Black pigs and identified genomic regions with high ROH frequencies.Results: In this work, 1,813 ROHs (837 ROHs in 100 to 500 kb, 449 ROHs in 500 to 1,000 kb, 527 ROHs in >1,000 kb) were identified in all samples, and the average genomic inbreeding coefficient (FROH) in Wannan Black pigs was 0.5234. Sixty-one regions on chromosomes 2, 3, 7, 8, 13, 15, and 16 harbored ROH islands. In total, 105 genes were identified in 42 ROH islands, among which some genes were related to production traits.Conclusion: This is the first study to identify ROH across the genome of Wannan Black pigs, the Chinese native breed of the Anhui province. Overall, Wannan Black pigs have high levels of inbreeding due to the influence of ancient and recent inbreeding due to the genome. These findings are a reliable resource for future studies and contribute to save and use the germplasm resources of Wannan Black pigs. Objective: Runs of homozygosity (ROH) are contiguous lengths of homozygous genotypes that can reveal inbreeding levels, selection pressure, and mating schemes. In this study, ROHs were evaluated in Wannan Black pigs to assess the inbreeding levels and the genome regions with high ROH frequency. Methods: In a previous study, we obtained 501.52 GB of raw data from resequencing (10×) of the genome and identified 21,316,754 single-nucleotide variants in 20 Wannan Black pig samples. We investigated the number, length, and frequency of ROH using resequencing data to characterize the homozygosity in Wannan Black pigs and identified genomic regions with high ROH frequencies. Results: In this work, 1,813 ROHs (837 ROHs in 100 to 500 kb, 449 ROHs in 500 to 1,000 kb, 527 ROHs in >1,000 kb) were identified in all samples, and the average genomic inbreeding coefficient (FROH) in Wannan Black pigs was 0.5234. Sixty-one regions on chromosomes 2, 3, 7, 8, 13, 15, and 16 harbored ROH islands. In total, 105 genes were identified in 42 ROH islands, among which some genes were related to production traits. Conclusion: This is the first study to identify ROH across the genome of Wannan Black pigs, the Chinese native breed of the Anhui province. Overall, Wannan Black pigs have high levels of inbreeding due to the influence of ancient and recent inbreeding due to the genome. These findings are a reliable resource for future studies and contribute to save and use the germplasm resources of Wannan Black pigs.