• 한국전기전자재료학회논문지
• /
• 제21권1호
• /
• pp.85-89
• /
• 2008

An objective of this paper is to develop a partial discharge (PD) measurement device for monitoring gas insulated switches installed in power distribution system. A capacitive voltage probe was studied and designed to detect PD pulse without an electrical connection. The PD measurement device consists of the capacitive voltage probe attached outside of a bushing, a coupling network which attenuates AC voltage by 270 dB, and a low noise amplifier with the gain of 40 dB in ranges of 500 kHz${\sim}$20 MHz. The sensitivity of the prototype device calculated by a calibrator was 1.98 m V /pc. An application experiment was carried out in a 25.8 kV gas insulated switch and the peak pulse of 76.7 pC was detected. From the experimental results, it is expected that the PD measurement device can be applied to online monitoring system of gas insulated switches.

• 제어로봇시스템학회논문지
• /
• 제16권1호
• /
• pp.12-17
• /
• 2010

The oil tanker ship over 150GRT must equip oil content meter which satisfy requirements of revised MARPOL 73/78. Online measurement of oil content in complex samples is required to have fast response, continuous measurement, and satisfaction of ${\pm}10ppm$ or ${\pm}10%$ error in this field. The research of this paper is to develop oil content measurement system using analysis of light transmission and scattering among turbidity measurement methods. Light transmission and scattering are analytical methods commonly used in instrumentation for online turbidity measurement of oil in water. Gasoline is experimented as a sample and the oil content approximately ranged from 14ppm to 600ppm. TSK Fuzzy Model may be suitable to associate variously derived spectral signals with specific content of oil having various interfering factors. Proposed Parallel TSK Fuzzy Model is reasonably used to classify oil content in comparison with other models. Those measurement methods would be effectively applied and commercialized to oil content meter that is key components of oil discharge monitoring control equipment.

• Asia pacific journal of information systems
• /
• 제31권4호
• /
• pp.491-526
• /
• 2021

Airlines can employ a variety of quality monitoring procedures. In this study, we employ a content analysis of 8 years of online reviews for Korean airlines in contrast to other international airlines. Online airline reviews are infrequent, relative to the total number of passengers - the number of reviews is multiple orders of magnitude lower than passenger volumes - and online airline reviews are, therefore, not representative of passenger attitudes overall. Nevertheless, online reviews may be indicative of specific service issues, and draw attention to aspects that require further study by airline operators. Furthermore, significant words and phrases used in these airline reviews may help airline operators to rapidly automate filtering, partitioning, and analysis of incoming passenger comments via other channels, including email, social media posts, and call center transcripts. The current study provides insights into the contents of online reviews of Korean vs Other-International airlines, and opportunities for service enhancement. Further, we provide a set of marker words and phrases that may be helpful for management dashboards that require automated partitioning of passenger comments.

• 전기학회논문지P
• /
• 제57권2호
• /
• pp.202-208
• /
• 2008

Condition monitoring technologies allow achieving this goal by minimizing downtime through the integrated planning and scheduling of repairs indicated by condition monitoring techniques. Thermal runaways induced by conduction problems deteriorate insulating material and cause disruptive dielectric discharges resulting in arcing faults. Therefore, having the ability to directly measure the temperature of the contacts while in service will provide more information to determine the true condition of the equipment. It allows connective measures to be taken to prevent upcoming failure. Continuous temperature monitoring and event recording provides information on the energized equipment's response to normal and emergency conditions. On-line temperature monitoring helps to coordinate equipment specifications and ratings, determine the real limits of the monitored equipment and optimize facility operations. Using wireless technique eliminates any need for special cables and wires with lower installation costs if compared to other types of online condition monitoring equipment. In addition, wireless temperature monitoring works well under difficult conditions in strategically important locations. Wireless technology for on -line condition monitoring of energized equipment is applicable both as stand alone system and with an interface for power quality monitoring system. The paper presents the results of wireless temperature monitoring: of electrical equipment at a power plant.

• Tribology and Lubricants
• /
• 제36권6호
• /
• pp.307-314
• /
• 2020

In this paper, studies on application cases of machine condition monitoring using oil sensors are reviewed. Owing to rapid industrial advancements, maintenance strategies play a crucial role in reducing the cost of downtime and improving system reliability. Consequently, machine condition monitoring plays an important role in maintaining operation stability and extending the period of usage for various machines. Machine condition monitoring through oil analysis is an effective method for assessing a machine's condition and providing early warnings regarding a machine's breakdown or failure. Among the three prevalent methods, the online analysis method is predominantly employed because this method incorporates oil sensors in real-time and has several advantages (such as prevention of human errors). Wear debris sensors are widely employed for implementing machine condition monitoring through oil sensors. Furthermore, various types of oil sensors are used in different machines and systems. Integrated oil sensors that can measure various oil attributes by incorporating a single sensor are becoming popular. By monitoring wear debris, machine condition monitoring using oil sensors is implemented for engines, automotive transmission, tanks, armored vehicles, and construction equipment. Additionally, such monitoring systems are incorporated in aircrafts such as passenger airplanes, fighter airplanes, and helicopters. Such monitoring systems are also employed in chemical plants and power plants for managing overall safety. Furthermore, widespread application of oil condition diagnosis requires the development of diagnostic programs.

• Smart Structures and Systems
• /
• 제21권5호
• /
• pp.687-694
• /
• 2018

The problem of wheel tread defects has become a major challenge for the health management of high-speed rail as a wheel defect with small radius deviation may suffice to give rise to severe damage on both the train bogie components and the track structure when a train runs at high speeds. It is thus highly desirable to detect the defects soon after their occurrences and then conduct wheel turning for the defective wheelsets. Online wheel condition monitoring using wheel impact load detector (WILD) can be an effective solution, since it can assess the wheel condition and detect potential defects during train passage. This study aims to develop an FBG-based track-side wheel condition monitoring method for the detection of wheel tread defects. The track-side sensing system uses two FBG strain gauge arrays mounted on the rail foot, measuring the dynamic strains of the paired rails excited by passing wheelsets. Each FBG array has a length of about 3 m, slightly longer than the wheel circumference to ensure a full coverage for the detection of any potential defect on the tread. A defect detection algorithm is developed for using the online-monitored rail responses to identify the potential wheel tread defects. This algorithm consists of three steps: 1) strain data pre-processing by using a data smoothing technique to remove the trends; 2) diagnosis of novel responses by outlier analysis for the normalized data; and 3) local defect identification by a refined analysis on the novel responses extracted in Step 2. To verify the proposed method, a field test was conducted using a test train incorporating defective wheels. The train ran at different speeds on an instrumented track with the purpose of wheel condition monitoring. By using the proposed method to process the monitoring data, all the defects were identified and the results agreed well with those from the static inspection of the wheelsets in the depot. A comparison is also drawn for the detection accuracy under different running speeds of the test train, and the results show that the proposed method can achieve a satisfactory accuracy in wheel defect detection when the train runs at a speed higher than 30 kph. Some minor defects with a depth of 0.05 mm~0.06 mm are also successfully detected.

• 한국산학기술학회논문지
• /
• 제21권9호
• /
• pp.229-237
• /
• 2020

본 연구는 실시간 온라인 시험방식을 고안하여 K대학교 간호학과 4학년 33명을 대상으로 2020년 1학기에 7차례의 시험을 실시한 결과를 공유하고, 실시간 온라인 시험에서의 공정성 확보방안을 제시하고자 시도되었다. 본 연구에서의 실시간 온라인 시험은 zoom cloud meetings를 활용하였다. 학생들이 PC나 노트북 중 한 가지 기기와 휴대폰으로 동시에 회의에 참여하도록 하였고, 교수자는 한 문제씩 화면에 실시간으로 띄워주며 비공개톡을 활용하여 답안을 수거하였다. 이러한 방식을 통해 학생들의 모니터 화면과 키보드, 마우스, 자세를 모니터링하고 통제하였다. 실시간 온라인 시험에 대한 설문조사 결과, 93.8%의 학생들이 전반적으로 공정하게 진행되었고 만족스럽다고 응답하였고, 90.6%의 학생들은 온라인 시험을 다른 사람에게 추천할 의향이 있다고 하였다. 다가오는 미래에는 원격강의와 온라인 시험이 보다 활성화될 것이므로 보다 공정하고 체계적이며 누구나 쉽게 활용할 수 있는 온라인 시험방식을 개발함으로써 점차 다른 시험으로도 확대시키려는 노력이 필요하다.

• 디지털융복합연구
• /
• 제15권3호
• /
• pp.287-294
• /
• 2017

본 연구는 최근 메르스와 같은 대규모 감염질환의 확산 경로를 추적하고 관리하는 의료서비스가 요구되면서 ICT 기술 도입을 시도하고 있는 의료환경의 새로운 패러다임에 적극 대응하기 위하여 비콘 스캐너 기반의 병실 모니터링 서비스 개발을 시도하였다. Beacon 하드웨어 개발과 Beacon 저전력 블루투스 4.0(Bluetooth Low Energy, BLE)용 펌웨어 개발 및 서버 및 웹기반 대시 보드 UI 개발을 통하여 위치기반서비스로 환자들의 위치를 파악하고 웹 UI 기반으로 모니터링 하는 등의 기능을 제공하는 개인 맞춤형 모니터링 시스템을 설계하였다. 비콘이라는 온라인 기술이 제대로 접목되지 못했던 곳에 온라인 기술을 접목함으로써 오프라인 병원 서비스의 효율성을 극대화하여 적극적인 감염대응 및 환자안전에 그 가치를 둘 수 있다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.525-526
• /
• 2007

Continuous on-line temperature monitoring provides the means to evaluate current condition of equipment and detect abnormality. It allows corrective measures to be taken to prevent upcoming failure. Continuous temperature monitoring and event recording provides information on the energized equipment's response to normal and emergency conditions. On-line temperature monitoring helps to coordinate equipment specifications and ratings, determine the real limits of the monitored equipment and optimize facility operations. Using wireless technique eliminates any need for special cables and wires with lower installation costs if compared to other types of online condition monitoring equipment. In addition, wireless temperature monitoring works well under difficult conditions in strategically important locations. Wireless technology for on-line condition monitoring of energized equipment is applicable both as standalone system and with an interface with power quality monitoring system.

• Smart Structures and Systems
• /
• 제30권6호
• /
• pp.661-671
• /
• 2022

Stayed cables are the key components for transmitting loads in cable-stayed bridges. Therefore, it is very important to evaluate the cable force condition to ensure bridge safety. An online condition assessment and anomaly localization method is proposed for cables based on the spatiotemporal correlation of grouped cable forces. First, an anomaly sensitive feature index is obtained based on the distribution characteristics of grouped cable forces. Second, an adaptive anomaly detection method based on the k-nearest neighbor rule is used to perform dissimilarity measurements on the extracted feature index, and such a method can effectively remove the interference of environment factors and vehicle loads on online condition assessment of the grouped cable forces. Furthermore, an online anomaly isolation and localization method for stay cables is established, and the complete decomposition contributions method is used to decompose the feature matrix of the grouped cable forces and build an anomaly isolation index. Finally, case studies were carried out to validate the proposed method using an in-service cable-stayed bridge equipped with a structural health monitoring system. The results show that the proposed approach is sensitive to the abnormal distribution of grouped cable forces and is robust to the influence of interference factors. In addition, the proposed approach can also localize the cables with abnormal cable forces online, which can be successfully applied to the field monitoring of cables for cable-stayed bridges.