• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.551-554
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• 2005

The method of the reduction of the automotive induction noise can be classified by the method of passive control and the method of active control. However, the passive control method has a demerit to reduce the effect of noise reduction at low frequency (below 500Hz) range and to be limited by a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used the LMS (Least-Mean-Square) algorithm because the LMS algorithm can easily obtain the complex transfer function in real-time. Especially, When the Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm goes bad when the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. Thus Normalized FXLMS algorithm was developed to improve the control performance under the rapid acceleration. The advantage of Normalized FXLMS algorithm is that the step size is no longer constant. Instead, it varies with time. But there is one additional practical difficulty that can arise when a nonstationary input is used. If the input is zero for consecutive samples, then the step size becomes unbounded. So, in order to solve this problem. the Correlation FXLMS algorithm was developed. The Correlation FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Correlation FXLMS Is presented in comparison with that of the other FXLMS algorithms based on computer simulations.

• 한국멀티미디어학회논문지
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• 제17권4호
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• pp.478-489
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• 2014

Recently, flood damage by frequent localized downpours in cities are on the increase on account of abnormal climate phenomena and growth of impermeable area by urbanization. In this study, we are focused on flooding on roads which is the basis of all means of transportation. To calculate real-time accumulated rainfall on a road link, we use the Coefficient of Correlation Weighting method (CCW) which is one of the revised methods of missing rainfall as we consider a road link as a unobserved rainfall site. CCW and real-time accumulated rainfall entered through the Internet are used to estimate the real-time rainfall on a road link. Together with the real-time accumulated rainfall, flooding history, rainfall range causing flooding of a road link and frequency probability precipitation for road design are used as factors to determine the Flood Risk Index on roads. We simulated two cases in the past, July, 7th, 2009 and July, 15th, 2012 in Busan. As a result, all of road links included in the actual flooded roads at that time got the high level of flood risk index.

• Asian Pacific Journal of Cancer Prevention
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• 제15권4호
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• pp.1527-1530
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• 2014

Background: Time to colposcopy (TC) after abnormal Pap smears was evaluated for influence on cytohistologic correlation (CHC). Materials and Methods: This retrospective study assessed the correlation between TC and CHC of women who had abnormal Pap smears. Colposcopic chart review included participants from 2010-2013 who attended a colposcopic clinic, Thammasat University Hospital, Thailand. Results: Four hundred and sixty cases who had abnormal Pap smears were recruited. Pap reports were atypical smears with low grade squamous intraepithelial lesion (SIL), high grade SIL and cancer at 339, 114 and 7 cases, respectively. One hundred and twenty four patients underwent loop electrosurgical excision procedure (LEEP). A half of the cases were colposcopically examined within 1-2 months after abnormal Pap collection. CHC was 88 percent and not affected at all by TC. Subjects who attended cervical cancer screening from affiliated health providers had shorter TC than those screened in our tertiary hospital. Conclusions: Time to colposcopy with abnormal Pap smears conducted at Thammasat University Hospital had a highest frequency of 42 days, in line with the literature. Length of TC does not affect the correlation between Pap and histopathologic reports. A longer waiting period for colposcopy did not alter progression or regression of the disease.

• 대한인간공학회지
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• 제19권1호
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• pp.1-9
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• 2000

This study was performed to investigate some characteristics on human error proneness in the computerized work environment. Our concerning theme was on human error likelihood according to personal temperament. Two experiments were performed. The first experiment was to study the effect of field- independence/dependence on error likelihood. The second experiment was on error proneness. These experiments were performed in information search task. which was most frequent task in computerized work environment such as the control room of nuclear power plant. Ten subjects were participated in this study. Analyzed results are as follows. Field-independence/dependence had a significant effect in both information search time and error frequency. Error proneness had a significant effect in both factors, too. And, a positive correlation was found between error frequency and information search time. These results will be utilized as a basis to study operator's error proneness in the computerized control room of nuclear power plant. later on.

• 한국안전학회지
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• 제12권4호
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• pp.191-200
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• 1997

This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

• 가족자원경영과 정책
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• 제12권1호
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• pp.41-55
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• 2008

The purpose of this study was to clarify variables affecting time management practice and the relationship between the practice and academic achievement of middle school students. Questionnaires including a time management scale were used for this study and the survey data were taken from 352 middle school students in Seoul and Gyeonggi-do. The statistical methods for the analysis were frequency, percentage, average, t-test, ANOVA and Pearson's correlation. The variables affecting student time management were gender, their standard of living, parental educational level and parental occupation. Religion and residential area were indicated as variables affecting several subscales of time management but the academic year of student had no effect on student time management behavior. The relationship between time management and the academic achievement of middle school students was slightly positive. Developing programs for time management in the field of family resource management is also necessary.

• 한국항행학회논문지
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• 제18권5호
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• pp.476-482
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• 2014

최근 다양한 센서를 활용하는 응용분야의 증가로, 가변전송률을 지원하는 무선 통신 시스템의 필요성이 증가하고 있다. 이를 위해 2.45 GHz 주파수 대역을 사용하는 IEEE 802.15.4 LR-WPAN 시스템이 보편적으로 활용되고 있으나, LR-WPAN 시스템은 250 kbps의 단일 전송률만을 지원하고 있어 다양한 센서 네트워크 시스템에 응용되기에는 한계가 존재한다. 따라서, 본 논문에서는 31.25 kbps, 62.5 kbps, 125 kbps의 가변 전송률을 지원할 수 있는 프리앰블 구조를 정의하고, 주파수 오프셋에 강인한 이중 상관알고리즘을 기반으로 저복잡도 특성을 갖는 시간 동기부의 하드웨어 구조를 설계하였다. 제안된 시간 동기부는 18.36 K의 logic slices 및 4개의 DSP48s로 합성되었으며, 기존의 구조 대비 각각 79.1%와 99.4%의 감소를 보였다.

• 한국정보통신학회논문지
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• 제19권7호
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• pp.1593-1598
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• 2015

본 논문에서는 사회적 감성과 주가의 상관성을 분석한다. 먼저, 주가 폭락 또는 폭등 기간과 그 직전의 극성을 각각 분석하고 이 결과를 이용하여 사회적 감성과 주가 사이의 상관관계를 분석한다. 본 연구를 위하여 과거의 다우존스산업평균지수 데이터를 수집하고 주가의 폭등과 폭락 시점을 검출한다. 검출한 시점에 근거하여 뉴욕 타임즈 기사를 수집하고 극성을 분석한다. 분석 결과에 의하면 주가 폭락 기간보다 폭등 기간에는 부정적 용어의 출현 빈도가 감소하고 긍정적 용어의 출현 빈도가 증가한다. 주가 폭락 또는 폭등 직전에는 부정적 용어의 출현 빈도와 긍정적 용어의 출현 빈도 사이에 차이가 커지 않다. 상관관계 분석에 의하면, 주가 폭락과 폭등 기간에는 사회적 감성과 주가 사이에 양의 상관관계를 보인다. 반면에, 주가 폭락과 폭등 직전에는 사회적 감성과 주가 사이에 유의한 수준의 상관관계를 나타내지 않는다.

• 한국산학기술학회논문지
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• 제21권5호
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• pp.69-76
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• 2020

수중에서 방사된 음원의 신호는 해수면, 해저면 반사에 의한 다중경로 시간지연(multi-path time-delay)을 포함하여 체계(system)의 센서에 수신된다. 다중경로 환경과 복잡한 해양환경의 외란(disturbance)에 의해 수신된 신호간 상관성(coherence)이 저하된다. 따라서, 신호간 시간지연값을 이용하여 수중음원의 위치를 추정하는 체계는 추정성능의 저하가 나타난다. 이러한 환경에서도 강인한 음원 위치 추정성능을 위해 선배열(uniform line array), 평면배열(rectangular array)과 같은 다양한 형태의 센서배열과 빔형성(beamforming) 기법, 비용함수(cost-function)과 같은 신호처리를 이용하여 왔다. 본 연구에서는 선배열 형태의 doublet array와 추정된 시간지연값 보정 기법을 이용하고자 한다. 3 개의 doublet array를 동일 선에 위치하였으며 각각의 doublet array에 수신된 신호간의 시간지연값을 2 단계로 추정하였다. 수신신호에 대해 상호상관(cross-correlation) 함수를 적용하여 추정된 시간지연값을 수신신호의 중심주파수(center-frequency)와 array의 개구경(aperture) 및 수중음원과의 기하학적 관계에 따라 보정하여 최종의 시간 지연값을 얻었으며 이로부터 음원의 거리와 방위를 추정하였다. 제안한 기법의 타당성을 확인하기 위해, Monte-Carlo method를 이용하여 시뮬레이션하였다.

• International Journal of Fluid Machinery and Systems
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• 제8권4호
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• pp.264-273
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• 2015

This presentation describes an experimental approach for the detection of cavitation in hydraulic machines by use of ultrasonic signal analysis. Instead of using the high frequency pulses (typically 1MHz) only for transit time measurement different other signal characteristics are extracted from the individual signals and its correlation function with reference signals in order to gain knowledge of the water conditions. As the pulse repetition rate is high (typically 100Hz), statistical parameters can be extracted of the signals. The idea is to find patterns in the parameters by a classifier that can distinguish between the different water states. This classification scheme has been applied to different cavitation sections: a sphere in a water flow in circular tube at the HSLU in Lucerne, a NACA profile in a cavitation tunnel and two Francis model test turbines all at LMH in Lausanne. From the signal raw data several statistical parameters in the time and frequency domain as well as from the correlation function with reference signals have been determined. As classifiers two methods were used: neural feed forward networks and decision trees. For both classification methods realizations with lowest complexity as possible are of special interest. It is shown that two to three signal characteristics, two from the signal itself and one from the correlation function are in many cases sufficient for the detection capability. The final goal is to combine these results with operating point, vibration, acoustic emission and dynamic pressure information such that a distinction between dangerous and not dangerous cavitation is possible.