• 한국음향학회지
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• 제31권7호
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• pp.449-460
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• 2012

발전소 건설 시에 설치된 지하매설 배관이 대부분 20년 이상 경과됨에 따라서 지하매설 배관의 누설탐지의 중요성이 점차 부각되고 있다. 본 논문의 목적은 발전소와 같이 매설배관 주변에 회전체 기계잡음이 존재하는 경우에 배관의 누설위치 추정성능을 개선하기 위한 방법을 연구하는 것이며, 이러한 목적을 달성하기 위하여 주파수영역에서 배관 주변의 회전체 기계잡음을 효과적으로 제거할 수 있는 방법을 제안하였다. 또한 상호스펙트럼의 위상정보를 이용하여 배관의 누설위치를 추정하는 방법을 제안하였다. 제안된 방법의 타당성 평가를 위하여 실험을 수행하였으며, 실험결과 회전체에서 발생하는 주기적인 잡음성분을 제거함으로써, 배관 누설을 탐지하는 상호상관함수기법의 성능을 개선할 수 있음을 확인하였다.

• 대한가정학회지
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• 제36권5호
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• pp.17-27
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• 1998

The need for periodic investigation on human growth rate and somatotypes has been increased because the scientific development and environmental factors have effected a lot on them recently. This study aimed to investigate the changes of the 638 female somatotypes in the age of 18-54 obtained by direct and indirect measurement. The measurement data were divided into 4 groups early young women age group (18-54), late young women age group (25-34), early middle age group (35-44), late middle age group (45-54) and compared each other based on each group by age. The results obtained from this study were as follows: 1. According to Mollison Curve based on the early young women, items of depth decreased overall and pp.P. length & shoulder length increased as the age increased. The circumference, breadth and thickness tended to increase, especially waist girth and thickness of waist increased markedly. The data showed that the increase rate of thickness was higher than that of breadth. 2. Gradual somatotype changes were observed by overlapping projection drawings obtained by direct measurement. Compared with the young women, the middle aged showed lower should point depth and hip line & crotch depth line were lengthened significantly. No significant difference was observed in overlapping of the early young women and the late young women' figure, neither was in early middle aged and the late middle aged. 3. By overlapping the side view of the young women group (18-37) and middle aged group (35-54), no significant postural characteristics were found, while the back tended to bend forward and the abdomen and hip appeared to get fat.

• International Journal of Fluid Machinery and Systems
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• 제2권1호
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• pp.31-39
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• 2009

The flow instability in a low specific speed mixed-flow pump, having a positive slope of head-flow characteristics was investigated. Based on the static pressure measurements, it was found that a rotating stall in the vaned diffuser occurs at about 65% flow rate of best efficiency point (BEP). A dynamic Particle Image Velocimetry (DPIV) measurement and the numerical simulations were conducted in order to investigate the flow fields. As a result, the diffuser rotating stall was simulated even by Computational Fluid Dynamics (CFD) and the calculated periodic flow patterns agree well with the measured ones by DPIV. It is clarified that a periodical large scaled backflow, generated at the leading edge of the suction surface of the diffuser vane, causes the instability. Furthermore, the growth of the strong vortex at the leading edge of the diffuser vane induces the strong backflow from the diffuser outlet to the inlet. The scale of one stall cell is covered over four-passages in total thirteen vane-passages.

• 대한의용생체공학회:의공학회지
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• 제22권3호
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• pp.241-247
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• 2001

ABR(auditory brainstem response) is one of the audiometry which measures objective hearing threshold level by acquiring electric evoked potentials emanated from auditory nerve system responding to an auditory stimulation. However, the obtained potentials which are largely interfered by power line noise, have extremely low SNR, thus ensemble average algorithm is generally used. The purpose of this study was to investigate the effect of iteration number in ensemble average on the reduction of the power line noise. The power line noise was modeled to be a 60 Hz sinusoidal signal and the energy of the modeled signal was calculated when it was averaged. It was verified by simulation that the energy had the periodic zero points for each stimulation rate, and 60 Hz signal induced by the power line was applied to the developed ABR system to confirm that the period of zero energy point was the same with that of the simulation. By the properly selected iteration number, power line noise could be reduced and more reliable ABR could be acquired.

• 대한소아치과학회지
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• 제21권2호
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• pp.491-495
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• 1994

The ectopic eruption is defined rise to be abnormal eruption, which gives to displacement of the teeth and abnormal root resorption of adjacent teeth. The ectopic eruption of first permanent molar is approximately 2-4% of the population, most of them are in the maxilla, rarely in the mandible. In the case of the second permanent molars, most of them are found in the mandible for the reason of the arch length discrepancies and large size of the teeth. The ectopic erupted molars should be treated early in order to coordinate normal growth pattern and to obtain good occlusal support. So, this should be early diagnosed and treated. But, ectopically erupting molars are often self-corrected, hence periodic follow-up is required. The methods of the treatment are largely classified into surgical, surgical-orthodontic, and orthodontic method. Especially in orthodontic method, they are divided as follows; appliances that is positioned at the contact point for unlocking and the distal movement, fixed and removable appliance that is connected to more than one tooth, and occlusion guiding method after disking or extraction of the second deciduous molar. The report presents the good results in treating patients, whose chief complaint was ectopic eruption of mandibular permanent molars.

• 한국정보통신학회논문지
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• 제3권2호
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• pp.291-304
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• 1999

주 연구에서는 압전체에서의 IDT 변환기, 음향 반사기에 대한 전기 음향 모드의 결합 모드 방정식을 유도, 정리함으로써 SAW 공진기 필터의 결합 모드를 수학적으로 분석할 수 있는 모델링 방법을 소프트웨어 설계 모듈화하고, SAW 공진기 필터를 구성하고 있는 각 구성 요소에 대한 회로적인 결합 방법의 제안을 통하여 SAW 결합 모드 공진기 필터의 설계 및 시뮬레이션 방법을 제안하였다. 또한, 제작된 소프트웨어 설계 모듈을 시뮬레이션 소프트웨어 패키지화함으로써 설계자가 손쉽게 이동통신기기용 결합 모드 공진기 필터를 설계할 수 있도록 그래픽 사용자 인터페이스를 갖는 SAW 결합 모드 공진기 필터의 설계 시뮬레이터를 구현하였으며 이를 통하여 이동통신기기에서 사용할 수 있는 결합 모드 공진기 필터를 모의 설계하고 주파수 특성을 해석함으로써 그 응용 타당성을 제시하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.39-44
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• 2005

In HANARO, a multi-purpose research reactor of 30 MWth, the emergency water supply system consists essentially of an emergency water storage tank located in the level of about thirteen meter (13 m) above the reactor core, a three inch ('3\%') diameter water injection pipe line including injection valves from the tank to the reactor cooling inlet pipe and a test loop to do periodic system performance test. When the water level of the reactor pool comes down to the extremely low due to a loss of reactor pool water accident the emergency water stored in the tank should be fed to the core by the gravity force and at that time the design flow rate is eleven point four kilogram per second (11.4 kg/s). But it is impossible periodically to measure the injection flow rate under the emergency condition because the normal water level should be maintained during the reactor operation. This paper describes a flow network analysis to simulate the flow rate under the emergency condition. As results, it was confirmed through the analysis results that the calculated flow rate agrees with the design requirement under the emergency condition.

• 전기학회논문지
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• 제67권1호
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• pp.142-147
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• 2018

Private electrical facilities are judged whether it is suitable for the insulation aging condition of their incoming underground cables using DC leakage current test method. In the case where the service point of utility is the secondary side of cut out switch installed in the electric pole, there is a problem that it is difficult to separate the lightning arresters(LA) because of their high position of the pole. Therefore, the field test voltage is applied at value lower than DC 30 kV, which are stated in the inspection guideline. However, this test could reduced the insulation performance of the LA by accelerating the electrical stress of the metal oxide varistor element in the pre-breakdown region. In this study, we analyzed the relationship between the DC test voltage and the leakage current using the non-destructive DC high voltage equipment with leakage current measurement function. The results show that the leakage current increases sharply above the specified test voltage. As a consequence, it could be contributed to improve insulation aging inspection method by selecting the possible test area on the VI characteristic curve of the pre-breakdown area of the LA.

• Journal of Multimedia Information System
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• 제5권3호
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• pp.195-200
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• 2018

Recently, as the sensor and big data analysis technology have been developed, there have been a lot of researches that analyze the purchase-related data such as the trajectory information and the stay time. Such purchase-related data is usefully used for the purchase pattern prediction and the purchase time prediction. Because it is difficult to find periodic patterns in large-scale human data, it is necessary to look at actual data sets, find various feature patterns, and then apply a machine learning algorithm appropriate to the pattern and purpose. Although existing papers have been used to analyze data using various machine learning methods, there is a lack of statistical analysis such as finding feature patterns before applying the machine learning algorithm. Therefore, we analyze the purchasing data of Songjeong Maeil Market, which is a data gathering place, and finds some characteristic patterns through statistical data analysis. Based on the results of 1, we derive meaningful conclusions by applying the machine learning algorithm and present future research directions. Through the data analysis, it was confirmed that the number of visits was different according to the regional characteristics around Songjeong Maeil Market, and the distribution of time spent by consumers could be grasped.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제6권2호
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• pp.67-74
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• 2017

본 논문은 손목 착용형 웨어러블 기기를 착용한 사용자의 걸음걸이에서 흔들리는 팔의 패턴을 통하여 사용자를 인증하는 방법을 제안한다. 기기에 내장된 가속도 센서를 이용하여 샘플링된 3축 가속도 센서 데이터를 수집한다. 수집한 데이터를 신호처리 기법을 통해 변환하여 걸음의 주기를 찾고, 푸리에 변환으로 걸음걸이의 주파수와 크기를 특징으로 추출하여, 2D 혼합 가우시안 모델(GMM)로 학습한 뒤, 신뢰구간 검증 방식으로 테스트한다. 실험결과 95%의 신뢰구간에서 사용자 평균 92%로 사용자를 인증함을 보였다.