• 한국음향학회지
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• 제12권5호
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• pp.54-63
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• 1993

적응 능동 잡음제거를 위한 새로운 방식을 기술했으며, 잡음원이 존재하는 환경에서 물리적인 잡음 제거를 하는데 목표를 두었다. 기존의 시스템 식별 방식과 달리 적응 예측기를 사용하였으며 신호를 검출하는데 쓰이는 마이크를 하나로 구성하였다. 잡음 신호 자체를 예측함으로써 적극적인 대처를 할 수 있으며 적응 알고리즘은 한번만 사용되고 적응 제어형 시스템 식별 방식에서 필요로 하는 피드백 항을 제거시킴으로써 시스템을 간략화시켰다. 컴퓨터 모의 실험 결과를 통하여 제안한 방식이 주기성을 갖거나 혹은 대역 제한된 잡음에 대해서 매우 유용함을 보였다.

• 소음진동
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• 제9권3호
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• pp.600-606
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• 1999

본 논문은 길이 방향에 따라 단면적이 감소하는 경로와 증가하는 경로 2개가 존재할 경우 길이 방향에 따른 단면적 변화율과 경로의 길이에 의하여 특정 주파수에서 음파의 위상이 반대되는 현상이 발생하여 전달 경로 하단에서 해당 주파수의 소음이 상쇄되는 현상을 규명하였다. 단면적 변화를 고려한 1차 파동 방정식을 적용하여 매우 간단한 해석적인 해를 구하였으며, 원형 덕트 내의 속이 빈 콘 형상의 단면적 변화를 적용하여 실험적으로 검증하였다. 질량 효과에 의하여 필터링 주파수는 1, 2차 모드에서는 이론보다 더 낮은 주파수에서 결정되나, 3차 이상 고차 모드에서는 이론식으로 그 해당 주파수를 예측할 수 있다. 본 연구의 결과는 좁은 공간에서 덕트의 특정 소음의 주파수를 제거하여 음질을 개선할 필요가 있는 경우 이를 덕트 내부에 적용하는 콤팩트한 필터로 적용할 수 있다.

• 대한전자공학회논문지TC
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• 제47권9호
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• pp.37-43
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• 2010

간섭제거 무선중계기는 미약한 기지국/단말의 RF신호를 곧바로 증폭해서 송출하여 기지국과 단말간의 연결범위를 확장하는 중계기로 송출된 신호의 일부가 주위환경에 의해 반사되어 입력되는 간섭신호를 제거하는 기능이 필수적이다. 본 논문에서는 궤환 신호 제거를 위한 채널 추정 알고리즘으로 Variable Stepsize Complex Signed-Signed(VSCSS) LMS 적응 알고리즘을 제안하였다. 제안된 알고리즘은 곱셈/나눗셈 연산이 없이 구현할 수 있어 FPGA 구현시 소요되는 논리 자원(Resource)을 획기적으로 줄일 수 있다. 알고리즘의 성능을 CSS-LMS 알고리즘과 비교 분석하였으며 모의실험을 통해 얻어진 학습곡선(Learning Curve)으로부터 분석의 유효성을 검증하였다. 또한 페이딩 궤환 채널 환경에서 WCDMA 신호에 대한 모의실험으로 널리 사용되고 있는 NLMS 알고리즘과 수렴 속도 및 오차 측면에서 거의 같은 성능을 보임을 입증하였다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.740-745
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• 1994

In the actual situation of measuring the environmental noise, it is very often that only the resultant phenomenon fluctuation contaminated by the additional noise of arbitrary distribution type can be observed. Furthermore, the observed data is usually given in a sound level form the purpose of estimating only the undisturbed objective output response, some estimation method is necessary to reasonably remove the effect of the above additional noise. In this paper, first, a mathematical model of arbitrary sound insulation systems is introduced in the form of a linear system on intensity scale, by using the well-known additive property of energy quantities. Next, some estimation method of the output response under the existence of background noise is derived. Then, based on the expression of the above estimation method, a new prediction method of only the output response probability function form for arbitrary sound insulation systems without. a background noise is proposed by use of observed data contaminated by a background noise. Finally, the effectiveness of the proposed method is confirmed experimentally too by applying it to the actual various type sound wall systems.

• Clinical and Experimental Reproductive Medicine
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• 제24권2호
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• pp.217-223
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• 1997

This study was performed to determine if women with day 3 serum inhibin-B concentrations <45pg/ml (conversion factor to SI unit, 1.00) demonstrate a poor response to ovulation induction and assisted reproductive technology outcome to women with inhibin-B${\ge}45pg$/ml, independant of day 3 FSH, E2 and patient age. From Jan 1996 to Dec 1996, 16 volunteers patients who underwent 25 IVF cycles with luteal phase GnRH agonist suppression and HMG stimulation were allocated to the study group. We evaluated day 3 serum inhibin-B, FSH, E2, peak E2, cancellation rate per initiated cycle (%) and clinical pregnancy rate per initiated cycle (%) according to the above two groups and independent of patient age, day 3 FSH, day 3 E2 and all of above combined. Women with day 3 serum inhibin-B${\ge}45pg$/ml demonstrated higher average day 3 inhibin-B level, clinical pregnancy rate per initiated cycle ($20.3{\pm}2.5$ pg/ml vs $80.9{\pm}5.0$ pg/ml, p<0.05; 24.8% vs 8.5%, p<0.05) and lower day 3 FSH level, cancellation rate per initiated cycle ($6.9{\pm}0.3$ mIU/ml vs $8.5{\pm}0.5$ mIU/ml, p<0.05; 1.5% vs 9.0%, p<0.05). Women with day 3 serum inhibin${\ge}45pg$/ml and age<40 year demonstrated higher pregnancy rate per initiated cycle (28.2% vs 7.4%, p<0.05) and lows. day 3 FSH level, cancellation rate per initiated cycle ($6.9{\pm}0.5$ mIU/ml vs $8.2{\pm}0.7$ mIU/ml, p<0.05; 1.0% vs 9.0%, p<0.05). Women with day 3 serum inhibin${\ge}45pg$/ml and day 3 FSH<15mIU/ml demonstrated higher pregnancy rate per initiated cycle (33.5% vs 9.5%, p<0.05) and lower day 3 FSH level, cancellation rate per initiated cycle ($7.7{\pm}0.2$ mIU/ml vs $8.5{\pm}0.5$ mIU/ml, p<0.05; 1.5% vs 10.0%, p<0.05). Women with day 3 serum inhibin${\ge}45pg$/ml and day 3 E2<50pg/ml demonstrated higher pregnancy rate per initiated cycle (30.0% vs 9.5%, p<0.05) and lower cancellation rate per initiated cycle (1.5% vs 9.5%, p<0.05). Women with day 3 serum inhibin${\ge}45pg$/ml, age<40 year, day 3 FSH<15mIU/ml and day 3 E2<50pg/ml demonstrated higher pregnancy rate per initiated cycle (30.0% vs 10.8%, p<0.05) and lower day 3 FSH level, cancellation rate per initiated cycle ($6.8{\pm}0.6$ mIU/ml vs $8.4{\pm}0.9$ mIU/ml, p<0.05; 1.5% vs 7.8%, p<0.05). Therefore women with low day 3 serum inhibin-B concentrations demonstrate a poorer response to ovulation induction and are less likely to conceive a clinical pregnancy though ART relative to women with high day 3 inhibin-B and day 3 serum inhibin-B, in addition to a day 3 FSH, E2 and patient age, appears helpful in prediction in IVF-ET outcome.

• The Journal of the Acoustical Society of Korea
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• 제15권2E호
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• pp.39-44
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• 1996

The performance of two-channel adaptive noise canceller is ofter degraded by the weights perturbation due to the speech signal. In this paper, an adaptive noise canceller employing a speech detector and two adaptation algorithms which are switched according to the speech detector is proposed. When highly correlated speech signal is detected, the tap weights of the adaptive filter are adapted by the sign algorithm. On the other hand, the weights are adapted by the NLMS algorithm when silence is detected or when the characteristics of the noise propagation channel is changed. The employed speech detector utilizes the power ratio of the input and the output of an adaptive linear prediction-error filter. According to the computer simulation, the proposed method yields better performance than conventional ones.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2003년도 10월 학술대회지
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• pp.101-104
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• 2003

In this paper, speech quality is improved by removing abrupt noise intervals and then substituting the gaps with estimates of the previous speech waveform. An abrupt noise detection signal has been proposed as a prediction error signal by utilizing LP coefficients of the previous frame. Abrupt noise intervals are estimated by using spectral energy. After removing estimated noise intervals, we applied several waveform substitution techniques such as zero substitution, previous frame repetition, pattern matching, and pitch waveform replication. To prove the validity of our algorithm, the LPC spectral distortion test and the recognition test are executed and, the results show that the speech quality is fairly well improved.

• 대한산업공학회지
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• 제36권1호
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• pp.13-21
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• 2010

The prediction of contract cancellation of customers is essential in insurance companies but it is a difficult problem because the customer database is large and the target or cancelled customers are a small proportion of the database. This paper proposes a new data mining approach to the binary classification by handling a large-scale unbalanced data. Over-sampling, clustering, regularized logistic regression and boosting are also incorporated in the proposed approach. The proposed approach was applied to a real data set in the area of insurance and the results were compared with some other classification techniques.

• Journal of information and communication convergence engineering
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• 제8권6호
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• pp.640-644
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• 2010

When we talk with hands-free in a car or noisy lobby, the performance of the echo canceller degrade because background noise added to echo caused by the distance from mouth to microphone is relatively long. It gives a reason for necessity of noise-robust and high convergence speed adaptive algorithm. And if acoustic echo canceller operated not perfectly, residual signal going through the echo canceller to far-end speaker remains residual echo, which degrade quality of talk. To solve this problem, post-processing needed to remove residual echo ones more. In this paper, we propose a new acoustic echo canceller, which has noise robust and high convergence speed, linked with linear predictor as a post-processor. By computer simulation, it is confirmed that the proposed algorithm shows better performance from acoustic interference cancellation (AIC) viewpoint.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2022년도 제66차 하계학술대회논문집 30권2호
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• pp.455-456
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• 2022

본 연구에서는 항공편 결항 시, 이용객이 겪게 되는 시간적 / 비용적 피해를 최소화하기 위해 머신러닝·딥러닝 기법을 이용하여 항공편 결항 예측 모델을 제안한다. 이 모델은 5가지 이진 분류기법을 사용하여 과거 2017년~2021년 제주공항 기상 데이터와 항공편 스케줄 데이터를 병합하여 결항, 출발을 분류한다. 본 연구는 기상으로 인한 항공편 결항의 피해 최소화를 목적으로 한다.