감속기 기어의 결함진단에 관한 연구

이재현,국재창,이재응 중앙대학교 기술과학연구소 1999 기술과학연구소 논문집 Vol.29 No.-

본 논문에서는 감속기 기어의 결함진단의 문제가 고려되었고, 시간-주파수 영역의 분석 방법인 위이블렛 변환을 결함진단 연구에 이용하였다. 웨이블렛 변환은 시간-주파수 영역에서 좋은 성능을 나타내며 다양한 기본 웨이블렛 함수를 가지고 있고 융통성과 적응력이 있는 변환방법과 해상도를 가지고 있어서, 급격히 변화하는 신호나 비정상 충격신호를 위치신호의 손실없이 잘 분석할 수 있는데, 이는 기어면에서 금속충돌이 일어나고 여거 기어이를 가지고 있는 복잡한 기어 시스템에서 더욱 유용하게 쓰일 수 있다. 또한 웨이블렛이 가진 주요 특성 중 하나인 잡음제거(de-noise) 기능을 사용하여 잡음이 합쳐져 있는 실제 신호를 더욱 효과적으로 분석 할 수 있었다. 실험대상은 두 쌍의 기어 물림이 있는 기어구동계를 사용하였고, 먼저 실험대상인 기어열에서 이론적으로 발생할 수 있는 싸인파들의 합성으로 이루어진 신호를 가지고 시뮬레이션을 실시하였고, 실험장치를 통해 정상상태기어에서의 신호와 기어에 인위적으로 발생시틴 결함에 의해 발생되는 신호를 측정하였으며 이러한 신호를 웨이블렛 변환하는 방법을 통해 결함을 분석하였다. In this paper, the problems of the fault detection of gear trains are considered, and the wavelet transforms are applied to evaluate the performance of detecting the incipient gear damage with real experimental data. The wavelet transform enables one to look at the evolution in time of a signal's frequency content. This property make it very suitable for the detection of transient vibrations generated by developing localized faults in gear trains. Recent applications of the wavelet technique have focused on the use of DWT(Descret Wavelet Transform) coefficients only. In this study, the wavelet denosing is also applied to remove the effect of the noise in the measured vibration signals. The denoised wavelet map is found to display distinctive features in the presence of several kinds of fault in a tooth.

대동맥판막에 발생한 유두상 섬유탄력종 1례

김응중,최재성,이명묵,김어진 동국대학교 의학연구소 2009 東國醫學 Vol.16 No.1

유두상 섬유탄력종은 주로 심장판막에 발생하는 원발성 종양으로 심장종양 중 두 번째로 많은 양성종양이나 전체적으로 그 빈도는 매우 드물다. 78세 여자 환자가 흉부 불편감을 주소로 내원해서 대동맥판막에 위치한 유두상 섬유탄력종이 발견되어 개심술 하에 대동맥판막의 손상 없이 종양을 제거하였기에 문헌고찰과 더불어 이를 보고하는 바이다. Cardiac papillary fibroelastoma is the rare primary cardiac tumor, though it is the second most common benign cardiac tumor. It usually involves the cardiac valve. Papillary fibroelastoma of the aortic valve was found in a 78-year-old woman with chest discomfort and it was excised without valvular injury under cardiopulmonary bypass. Thus we report the present case with relevant review of the literatures.

FESWMS-2DH를 이용한 하천의 흐름 해석

이철응,심재욱,박동헌 江原大學校 産業技術硏究所 2009 産業技術硏究 Vol.29 No.A

In this study, flood stage was computed by HEC-RAS, 1-D numerical analysis model and FESWMS-2DH, 2-D numerical model. Flood stages computed by two different models were compared for straight line, dot axle watercourse, dead-zone watercourse, section sudden-changing watercourse, and curved watercourse. From the results, flow velocity and water level were similar in straight watercourse and dot-reduction watercourse. However, there was difference of flow velocity and water level in dead-zone watercourse, sudden expansion, dot-reduction, and curve-watercourse. This result might be influenced by rapid change of watercourse due to dead-zone, the angle of inflow and outflow, and the curvature. Especially in this study, numerical model was applied to Wol-Song-Cheon at Chuncheon in order to analyze the effect of flood stage by two different models. By flowing properties around the bridge and confluence of rivers, it was found that flow velocity and water level was changed. Therefore, it was concluded that a lot of uncertainties are contained in the present bank.

職業選擇과 職業價値觀에 關한 硏究

전재일,여광응 한국사회사업대학 학생지도연구소 1975 학생지도연구 Vol.2 No.-

심실중격결손을 동반한 폐동맥폐쇄에서 선천적우회순환의 기시 및 분포 : A Cineangiographic Study

최재영,이종균,차응석,설준희,이승규,최규옥 대한순환기학회 1998 Korean Circulation Journal Vol.28 No.9

만성요통 환자의 우울수준과 통증감소에 미치는 전통적 물리치료의 효과

유재응,정은하 대한물리치료학회 2001 대한물리치료학회지 Vol.13 No.3

The object of this study is in the comparison of level of depression between patients with chronic low back pain & normal adult, of the relation between reduction of pain & level of depression and in the examination of the influence of traditional physical therapy against the reduction of pain & level of depression of the patients with chronic low back pain for the new recognition of psychological factors to the physical therapists as well as patients. This study was targeted for 40 patients with chronic low back pain who were diagnosed as lumbar sprain & herniated intervertebral disk and compared & analyzed how traditional physical therapy has an influence to their reduction of pain and level of depression by questioning with visual analog scale of Beck's depression inventory & pain inventory to them. The results are as follows. 1. Traditional physical therapy has an effect in the reduction of pain of the patients with chronic low back pain. 2. Although traditional physical therapy relieved a little the level of depression of patients with chronic low back pain, there was no evident effect statistically. 3. In the relation between the reduction of pain and level of depression, level of depression also showed somewhat relief according to the reduction of pain and appeared that they have some relationship. However, it's degree was not big. 4. In the comparison of the level of depression between the normal adult and the patient with chronic low back pain, the level of depression of the patient with low back pain are high rather than that of normal adult.

10종 경기에서 선수의 선행 종목이 경기력에 미치는 영향

김응식,안재오 한국스포츠리서치 2003 한국 스포츠 리서치 Vol.14 No.4

This study made a comparative analysis of the winning points in different sporting events of decathletes and positively identified how the preceding items experienced by them influenced competitive performance. The results are to be used as basic data for the selection of decathletes and improvement of their competitive performance. For the study, performance of 29 players who won 5500 points in total were sampled from athletic sports records from 1999 to 2002 published by the Korea Athletics Federation. After that, the following results were obtained through averaging, correlation analysis, multi-regression analysis and covariance analysis. 1) It was demonstrated that for Korean decathletes, competitive performance in Short put is relatively stronger compared with that of jumping and throwing, but that of throwing is relatively very low. 2) It was demonstrated that an individual item that has the greatest influence on performance was discus Throw and weight do not influence performance. 3) Items that have a significant difference of performance according to preceding athletic items performance were 110mH, long jump, pole vault and discus Throw. For 110mH, long jump, and pole vault, a good record was found when a preceding item was jump. For throwing, the best record was found in discus Throw.

랜덤진동에서 응답함수에 나타나는 각 모우드의 기여도 평가

이재응,이병림 중앙대학교 기술과학연구소 1994 기술과학연구소 논문집 Vol.24 No.-

In this paper, the dispersion analysis methodology which is a physical meaningful way of assessing the relative importance of the estimated vibrational modes based on their contribution ("dispersions") to the vibration signal energy is introduced. The effects of modal cross-correlation are fully accounted for, physical interpretations are provided in both the correlation and spectral domains.

大豆油 高溫處理時 BHA, TBHQ, Silicone 및 시트르산 添加가 品質에 미치는 영향

全濟鉉,李應昊,金世權 釜山水産大學校 1984 釜山水産大學 硏究報告 Vol.24 No.1

튀김할 때 식용유는 가열매체인 동시에 풍미나 영양원이 된다. 튀김용 식용유의 품질변화방지를 위한 기초자료를 얻을 목적으로 식용대두유로서 고온처리 및 튀김을 할 때 BHA, TBHQ, silicone 및 시트르산 첨가가 식용유의 품질에 미치는 영향을 실험하였다. 98℃이하의 열처리 결과 시트르산 1ppm, TBHQ는 50∼200ppm첨가한 것이 산화방지에 효과적이었으나 BHA와 silicone은 효과가 거의 없었다. 180℃ 가열처리 및 튀김시험에 있어서는 시트르산은 산화를 촉진하는 경향이 있었고 BHA 및 TBHQ는 별 효과가 없었으며 silicone이 가장 효과가 좋았다. silicone 1∼5ppm가지는 품질변화방지효과에 큰 차이가 없었으나 튀김할 때는 원료에 이행하는 양이 있으므로 첨가량이 증가할수록 효과가 좋았다. 그러므로 식용유 품질변화를 방지하는데 있어 100℃이하에서 처리할 때는 시트르산을 첨가하는 것이 효과적이고, 튀김처럼 고온처리하는 식용유에서는 1∼5ppm의 silicone을 첨가하는 것이 효과적이라는 결론을 얻었다. Edible oils serve both as a heat transfer medium and a source of flavor and nutrition since ,some of the fat is absorbed by the food being fried. In this paper, the effects of butyl hydroxyanisole(BHA), teritary butyl hydroquinone(TBHQ), silicone and citric acid on thermal stability of the soybean oil during heating and frying were evaluated. Judging from the results of swift stability test (active oxygen method) that the minimum effective concentration of citric acid and TBHQ for ,the thermal stability of soybean oil when heated at 98℃ was 1 ppm and 50 to 200 ppm, respectively. But BHA and silicone showed no effect. On the other hand, silicone seemed to improve the thermal stability of soybean oil during heating at 180℃ or frying with potato while BHA and TBHQ showed no significant effect.

기어의 缺陷診斷에 關한 硏究

이재응,유근희,한재영,장흥석 중앙대학교 기술과학연구소 1997 기술과학연구소 논문집 Vol.27 No.-

본 논문에서는 기어의 결함을 진단하는데 있어 다양한 신호처리방법에 의한 결함추적방법에 대해 연구하였으며 이를 실험 결과와 비교함으로서 그 방법들의 타당성을 검증하였다. 시간영역에서는 Time Synchronous Averaging을 이용한 방법, Kurtosis를 이용한 방법, Demodulation을 이용한 방법을 사용하였으며 주파수영역에서는 스펙트럼에 의한 결함진단방법, 켑스트럼을 이용한 결함진당방법, 그리고 시간-주파수영역에서는 Moving Window 에 기초한 STFT(Short Time Fourier Transformation)에 의한 방법, Wavelet Transform에 의한 방법 등을 사용하였다. 각각의 방법마다 결함을 추적하는데 있어 정도의 차이를 보여왔지만 대부분이 결함을 진단할 수 있는 방법임이 증명되었다. 각각의 방법들은 장단점과 한계를 가지고 있으므로 이를 비교하였으며 이 결과를 토대로 측정대상과 측정목적에 따라 각각의 진단방법을 선택할 수 있게 하였다. 기어의 결함을 추적하는데 있어 전달오차가 존재하거나 복잡한 구조물에서는 이러한 진단방법들을 다중적으로 사용함으로서 각각의 장점을 살리며 단점을 보완하는 최적의 진단방법을 구축할 수 있을 것이라 사료된다. In this thesis, the problems of the fault detection of gears are considered, and the several methods are applied to evaluate the performance of detecting the incipient gear damage with real experimental data. A typical gear fault(wear) is intentionally introduced on a gear and the signals are compared with those obtained from the unfault reference gear. The acceleration and the noise signal are measured, and analyzed by time synchronous averaging, demodulation, kurtosis in the time domain, frequency analysis, cepstrum analysis, the short-time moving window, and wavelet transform method in the time-frequency domain. The results show that each method have their own advantages/disadvantages, and therefore it is recommended to use several methods in the field applications.