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Automated Detection of Rotor Faults for Inverter-Fed Induction Machines Under Standstill Conditions
Byunghwan Kim,Kwanghwan Lee,Jinkyu Yang,Sang Bin Lee,Wiedenbrug, E J,Shah, M R IEEE 2011 IEEE transactions on industry applications Vol.47 No.1
<P>It is difficult to apply conventional online motor current signature analysis techniques for diagnosis of rotor faults for closed-loop induction motor drives for many applications due to the masking effect of the feedback current controller and/or variable frequency or load operation. Relying solely on traditional offline inspection techniques during regular maintenance does not allow frequent monitoring of rotor problems and is inconvenient since it requires rotor disassembly and/or manual rotor rotation. In this paper, a new automated technique for testing voltage source inverter-fed squirrel-cage induction machines at a standstill for rotor faults is proposed. The main concept is to use the inverter to excite the machine with a pulsating field at a number of angular positions to observe the variation in the impedance pattern due to broken rotor bars, whenever the motor is stopped. An experimental study on a 7.5-hp induction motor verifies that broken bars can be detected with high sensitivity and reliability. It will be shown that the proposed method can provide automated and reliable assessment of rotor condition frequently without motor disassembly, manual rotation, or additional instrumentation. The proposed test can also provide rotor quality assessment independent of variations in motor or load operating conditions since it is a standstill test.</P>
抗結核劑 長期服用者에 있어서 Peripheral Polyneuropathy에 對한 調査硏究
楊秉煥 大韓神經精神醫學會 1975 신경정신의학 Vol.14 No.1
Since the introduction of INH into antituberculous therapy, symptoms of neuropathy have been noticed in many patients. The author studied 27 cases with INH polyneuropathy among 86 patients who had been treated with INH (300mg) in a rural community from June to September 1974. High frequency of INH polyneuropathy could be attributed partially to malnutrition of the patients from poor economic condition. The longer duration of medication, the higher was frequency of INH polyneuropathy. No correlation of frequency of polyneuropathy to sex, age, and severity of lung tuberculosis was noticed. It was also proved that combined therapy with PAS and presence of digestive symptoms did not influence on the frequency of polyneuropathy.
온라인 쇼핑몰의 사용자 특성과 정보프라이버시가 구매의도에 미치는 영향에 대한 연구
양재민(Jaemin Yang),현병환(Byunghwan Hyun) 한국인터넷전자상거래학회 2020 인터넷전자상거래연구 Vol.20 No.6
Buying clothing from Internet shopping malls is a very natural routine, and transactions have exploded recently. However, research on the existing integrated technology acceptance model and privacy concerns have been conducted on all online shopping malls, but there is a lack of research on online shopping malls that sell clothing products. In particular, since clothing products require more information, such as physical information, in addition to basic information, research on concerns about information privacy is needed for clothing products. The purpose of this study is to find out how privacy concerns affect purchasing intentions, and to derive implications by applying an integrated technology acceptance model to test the direct impact of Internet shopping mall characteristics and user characteristics on purchasing intentions, as well as the mediating effects and causality of information privacy concerns and perceived usefulness. Based on the theoretical study, the research model was set and the data of 500 people collected in the survey were analyzed using stata 13.0 and AMOS 18.0. As a result of empirical analysis, the impact on purchasing intention was influenced by product quality, self-efficacy, and individual innovation among independent variables. In addition, there were no mediated effects on perceived information privacy concerns, and perceived usefulness was shown to have mediated effects. Studies have shown that innovative shopping contents or processes are needed, efforts should be made to recognize that they are not vulnerable to privacy along with the development of functions and performance, and that database construction and technology development should be carried out to improve product quality. However, this study requires in-depth research by matching the ratio of general characteristics such as gender and age, considering various types of shopping malls, and supplementing survey questions. In addition, the hypothesis of information privacy concerns needs to be studied in depth in the future to follow up on what variables may have resulted from.
A New Strategy for Condition Monitoring of Adjustable Speed Induction Machine Drive Systems
Sang Bin Lee,Jinkyu Yang,Jongman Hong,Ji-Yoon Yoo,Byunghwan Kim,Kwanghwan Lee,Jangho Yun,Myungchul Kim,Kwang-Woon Lee,Wiedenbrug, E J,Nandi, S IEEE 2011 IEEE transactions on power electronics Vol.26 No.2
<P>A new strategy for monitoring the condition of adjustable speed induction machine drive systems is presented in this paper. The main concept of the new method is to use the inverter to perform off-line tests for quality assessment of the vulnerable components in the inverter, cable, and induction motor automatically whenever the motor is stopped. This new approach is suitable for monitoring system components that deteriorate gradually to failure, if the degradation is observable. Off-line test methods for monitoring the quality of the 1) dc-link aluminum electrolytic capacitor; 2) electrical connections; 3) cable and stator winding insulation; 4) stator core; and 5) rotor bar are presented along with a summary of the failure mechanism and existing test methods. It will be shown that the new strategy can be implemented with minimal hardware requirements, and that it has many advantages over existing off-line and on-line tests. An experimental study performed under simulated fault conditions for each component shows that the method provides a reliable and sensitive indication of drive system problems for reliable, efficient, and safe operation.</P>
Fractal Analysis of EEG During Waking and Hypnosis: Laterality and Regional Differences
JunSeok Lee,SaeByul Kim,ByungHwan Yang,David Spiegel,JuYeon Choi,JunHo Choi,SeokHyeon Kim,JangHan Lee,SunIl Kim 대한신경정신의학회 2005 PSYCHIATRY INVESTIGATION Vol.2 No.1
We studied the trends of EEG signals during waking and hypnosis, by using fractal analysis to define the physiological concomitants of hypnosis. The subjects in this study were 6 psychiatric outpatients who were in good medical condition. The hypnotist induced hypnosis using a modified version of the hypnotic induction profile (HIP) technique. EEG data were acquired by means of a Telefactor EEG monitoring device installed in the EEG recording room. Twenty-five sets of data were analyzed using detrended fluctuation analysis (DFA), which is a well-established fractal analysis technique. The following results were obtained. 1) All of the scaling exponents, which constitute the result of fractal analysis, were greater than 0.5 and less than 1.5 in both the waking and hypnotic conditions. In addition, significant differences in the scaling exponents were found between the waking and hypnotic condition in most of the channels (except, Fp1 and F4). 2) We analyzed the individual changes in the scaling exponents of each subject, resulting from a number of hypnotic trials. In all of the trials, the differences among the scaling exponents of each trial were statistically nonsignificant. 3) The examination of the right-left symmetries did not yield any statistically significant difference. In this research, the scaling exponents of fractal analysis are reduced nearly to the level of white noise during the hypnotic condition. Therefore, this technique can differentiate the hypnotic condition from the waking condition. Additionally, the findings of this study suggest that hypnosis comes from a change in organization of neural activity in the whole brain network, rather than being a “specific area” phenomenon.
강전연,윤재철,김호영,김병환,최중호,양상선,유지훈,김용진,Kang, Jun-Yun,Yun, Jaecheol,Kim, Hoyoung,Kim, Byunghwan,Choe, Jungho,Yang, Sangsun,Yu, Ji-Hun,Kim, Yong-Jin 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.3
A cold-work tool steel powder is used to fabricate 3-dimensional objects by selective laser melting using a high-pressure gas atomization process. The spherical powder particles form continuous carbide networks among the austenite matrix and its decomposition products. The carbides comprise Nb-rich MC and Mo-rich $M_2C$. In the SLM process, the process parameters such as the laser power (90 W), layer thickness ($25{\mu}m$), and hatch spacing ($80{\mu}m$) are kept fixed, while the scan speed is changed from 50 mm/s to 4000 mm/s. At a low scan speed of 50 mm/s, spherical cavities develop due to over melting, while they are substantially reduced on increasing the speed to 2000 mm/s. The carbide network spacing decreases with increasing speed. At an excessively high speed of 4000 mm/s, long and irregularly shaped cavities are developed due to incomplete melting. The influence of the scan pattern is examined, for which $1{\times}1 mm^2$ blocks constituting a processing layer are irradiated in a random sequence. This island-type pattern exhibits the same effect as that of a low scan speed. Post processing of an object using hot isostatic pressing leads to a great reduction in the porosity but causes coarsening of the microstructure.