• 한국항행학회논문지
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• 제25권5호
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• pp.363-369
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• 2021

본 논문에서는 텔레메트리 시스템을 위한 가변 컷 오프 주파수 및 가변 샘플레이트 특성을 지니는 저면적 다채널 디지털 필터구조를 제안한다. 제안하는 디지털 필터는 임의의 컷 비율에 대해 필터 뱅크의 추가적인 설계 없이 컷 오프 주파수와 샘플레이트를 가변적으로 사용할 수 있는 필터 뱅크를 구현함으로써 하드웨어 면적을 줄일 수 있었다. 또한, 멀티플렉서 (MUX; Multiplexer) 컨트롤을 통해 통과하는 필터의 개수에 따라 샘플레이트를 가변적으로 선택할 수 있는 구조를 제안한다. 제안하는 디지털 필터는 Quartus의 FIR (finite impulse response) IP (intellectual property)의 TDM (time division multiplexing)을 이용함으로써, TDM을 사용하지 않았을 때보다 면적이 큰 DSP (digital signal processing) 블록을 80개에서 1개로 줄일 수 있었다. Kaiser 창 함수를 이용하여 Matlab을 통해 필터의 차수와 계수를 계산하였으며, VHDL (very high speed integrated circuits hardware description language)을 통해 하드웨어로 구현하였다. 텔레메트리 시스템에 적용 후, 실험 결과를 통해 제안하는 디지털 필터가 정상적으로 동작하고 있음을 확인하였다.

• 한국강구조학회 논문집
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• 제8권4호통권29호
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• pp.19-29
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• 1996

In this paper, it is presumed that the stress time history was generated by simulation method and investigated compatibility in regard to the reappearance of stress time history. In this procedure, the identified frequency distribution of stress range of the steel railroad bridge varies with the rational values of cut off point and bar width. Thus, we show variable aspect of the equivalent stress range results from change of cut off point and bar width. In addition, we analyze the variable of RMC and RMS model due to the cut off point and bar width of the measured stress history which influencs the prediction of fatigue life in the steel railroad bridge. The simulated stress time history is carried out by the superposition method incorporating the vertical load with rotation moment obtained from the Hermition interpolation function, and compared with developing stress results from measured maxi mum stress. Through this study, we can estimate the remaining fatigue life from a safety point of view and comparative accuracy.

• 조명전기설비학회논문지
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• 제25권1호
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• pp.78-84
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• 2011

Using sensors to detect current or voltage of motors is disadvantaged because motor is exposed to vibration, impacts, corrosion, high temperature and humidity in the machinery structure like HEV. In the case of IPMSM, position information is included not only in the flux or EMF term but also in the rotator inductance because of its saliency. To solve this problem, a new mathematical model of IPMSMs on fixed frame is proposed and an extended EMF includiing rotating position information is defined to estimate extended EMF. A strong low-pass filter through the variable cut-off frequency using velocity function was proposed. This makes it is possible to estimate extended EMF by least order disturbance observer. The proposed method was proved through the experiment.

• 대한임상검사과학회지
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• 제55권3호
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• pp.132-142
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• 2023

서울대학교병원 진단면역검사실에서 HLA 형별 검사를 위한 결과 산출하는 과정에서 HLA-DR 검사 시행 건수 총 611건 중 Lot No.20의 시약에서 빈번히 나타나는 위양성과 위음성으로 의심되는 특이 bead 들의 반응을 발견하게 되었다. 따라서 정확한 결과 산출과정을 모색하기 위하여 특이 bead들의 cut-off 수정을 하지 않은 검사결과 533건과 특이 bead의 cut-off 수정을 한 뒤 결과 산출을 한 78건의 사례들을 가지고 cut-off 수정을 야기시키는 요인을 여러 변수로서 규명하고자 하였다. 검체대상의 인구통계특성과 cut-off 수정 여부를 확인하기 위해 빈도분석, 검사실의 습도를 변수로 넣어 기술통계를 진행하였고, cut-off 수정 여부와 인구통계특성의 연관성을 확인하기 위하여 교차분석을 시행, cut-off 수정 여부에 따른 습도의 차이를 검증하기 위해 독립표본 t검증을 실시하였다. 마지막으로 습도수준에 따른 cut-off 수정비율의 관계를 검증하기 위해 로지스틱 회귀분석을 실시하였다. 결과적으로 검사실의 습도 수준이 증가함에 따라 cut-off 수정사례는 0.986배 감소하는 것으로 나타났다. 이는 습도가 낮아질수록 cut-off 수정률이 증가한다는 것을 의미한다. 따라서 검사실의 습도 또한 HLA typing 결과에 영향을 미치는 요인임을 시사한다.

• 한국컴퓨터정보학회논문지
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• 제8권3호
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• pp.163-169
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• 2003

본 연구에서 개발하고자 하는 기기의 모델은 마이크로 컨트롤을 이용하여 모터속도를 제어 할 수 있는 출력 전자 변속기로써, 자동제어 방식을 사용하여 Switching frequency를 1,000MHz까지 가능한 형태로 변환하는 자동 변속장치이다. 연속출력전류는 5A, 11A, 18A, 25A, 35A, 50A이며, 사용되는 전압은 9V에서 최대 18V까지 가능하도록 설계하였다. Micro-controller 의 software와 hardware의 블록 다아이그램을 고안하였으며, 전력손실을 막기 위해 자동적으로 3.7V에서 Auto Cut-Off기능이 있도록 구성하였다.

• Journal of Power Electronics
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• 제11권3호
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• pp.369-374
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• 2011

Usually, a LPF (low pass filter) is used in the feedback loop of a SRF (synchronous reference frame) - PLL (phase locked loop) system because the measured grid voltage contains harmonic distortions and sensor noises. In this paper, it is shown that the cut-off frequency of the LPF should be designed to suppress the harmonic ripples contained in the measured voltage. Also, a new design method for the loop gain of the PI-type controller in the SRF-PLL is proposed with consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and the PI controller gain are designed in coordination according to the steady state and dynamic performance requirements. Furthermore, in the proposed method, the controller gain and the LPF cut-off frequency are changed from their normal value to a transient value when a voltage disturbance is detected. This paper shows the feasibility and usefulness of the proposed methods through the computer simulations and experimental results.

• 대한통합의학회지
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• 제10권3호
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• pp.107-117
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• 2022

Purpose : The purpose of this study was to establish a model of the predictive factors for success or failure of examinees undertaking the Korean physical therapist licensing examination (KPTLE). Additionally, we assessed the pass/fail cut-off point. Methods : We analyzed the results of 10,881 examinees who undertook the KPTLE, using data provided by the Korea Health Personnel Licensing Examination Institute. The target variable was the test result (pass or fail), and the input variables were: sex, age, test subject, and total score. Frequency analysis, chi-square test, descriptive statistics, independent t-test, correlation analysis, binary logistic regression, and receiver operating characteristic (ROC) curve analyses were performed on the data. Results : Sex and age were not significant predictors of attaining a pass (p>.05). The test subjects with the highest probability of passing were, in order, medical regulation (MR) (Odds ratio (OR)=2.91, p<.001), foundations of physical therapy (FPT) (OR=2.86, p<.001), diagnosis and evaluation for physical therapy (DEPT) (OR=2.74, p<.001), physical therapy intervention (PTI) (OR=2.66, p<.001), and practical examination (PE) (OR=1.24, p<.001). The cut-off points for each subject were: FPT, 32.50; DEPT, 29.50; PTI, 44.50; MR, 14.50; and PE, 50.50. The total score (TS) was 164.50. The sensitivity, specificity, and the classification accuracy of the prediction model was 99 %, 98 %, and 99 %, respectively, indicating high accuracy. Area under the curve (AUC) values for each subject were: FPT, .958; DEPT, .968; PTI, .984; MR, .885; PE, .962; and TS, .998, indicating a high degree of fit. Conclusion : In our study, the predictive factors for passing KPTLE were identified, and the optimal cut-off point was calculated for each subject. Logistic regression was adequate to explain the predictive model. These results will provide universities and examinees with useful information for predicting their success or failure in the KPTLE.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1995년도 제12회 음성통신 및 신호처리 워크샵 논문집 (SCAS 12권 1호)
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• pp.221-224
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• 1995

In speech signal processing, it is necessary to detect exactly the pitch. The algorithms of pitch extraction with have been proposed until now are difficult to detect pitches over wide range speech signals. In this paper, thus, we proposed a new pitch detection algorithm that used a low pass filter with variable bandwidth. It is the method that preprosses to find the first formant of speech signals by the FFT at each frame and detects the pitches for signals LPFed with the cut off frequency according to the first formant. Applying the method, we obtained the pitch contours, improving the accuracy of pitch detection in some noise environments.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.381-386
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• 2013

A new resistance model for a Schottky Barrier Diode (SBD) in CMOS technology is proposed in this paper. The proposed model includes the n-well thickness as a variable to explain the operational behavior of a planar SBD which is firstly introduced in this paper. The model is verified using the simulation methodology ATLAS. For verification of the analyzed model and the ATLAS simulation results, SBD prototypes are fabricated using a $0.13{\mu}m$ CMOS process. It is demonstrated that the model and simulation results are consistent with measurement results of fabricated SBD.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권1호
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• pp.30-36
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• 2004

An iterative sliding mode observer is proposed to sensorless control of a PMSM(Permanent Magnet Synchronous Motor). The proposed sliding mode observer has the character which is robust to the disturbance and parameters variation. A low pass filter with the variable cut-off frequency is also proposed to compensate the delay of the rotor angle according to the rotor speed, it is led to save memory and minimize operation time. Experimental results show that the proposed sliding mode observer leads to the proper performance.