• 디지털산업정보학회논문지
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• 제8권2호
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• pp.49-58
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• 2012

This paper is on an improved orthogonal projection method which can cancel the acoustic feedback signals in the digital hearing aids. Comparing with the NLMS algorithm which is widely used for simplicity and stability, it shows that this method has the improvement of the convergence performances, and has small computational quantities, for signals with the large auto-correlation as speech signals. This uses the improved orthogonal projection algorithm which reduces the correlation of signals. To verify the convergence characteristics of the proposed algorithm, we simulated about various input signals. The acoustic feedback canceller has a 12-bit resolution with 64-tap adaptive FIR filter. And we compared the results of simulation for this algorithm with the ones for the NLMS algorithm. By these works, it is proved that the feedback canceller adopting the proposed algorithm shows about 3.5dB more high SNR than the NLMS algorithm in the colored input signals.

• 제어로봇시스템학회논문지
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• 제7권11호
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• pp.944-952
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• 2001

Inertial navigation system(INS) errors increase with time due to inertial sensor errors, and therefore it is desired to combine INS with external aids such as GPS. However GPS informations have a randomly abrupt jump due to a sudden corruption of the received satellite signals and environment, and moreover GPS can\`t provide navigation solutions. In this paper, smoothing and prediction schemes are proposed for GPS`s jump or unavailable GPS. The smoothing algorithm which is designed as a scalar adaptive filter, smooths abrupt jump. The prediction algorithm which is proved by Schuler error model of INS, estimates INS error in appropriate time. The outputs of proposed algorithm apply stable measurements to GPS aided INS Kalman filter. Simulations show that the proposed algorithm can effectively remove measurement jump and predict INS error.

• 한국수산과학회지
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• 제32권6호
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• pp.770-773
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• 1999

멸치액젓제품의 풍미, 색택개선 및 유통중 불용성 침전생성 억제를 위한 기초자료를 얻기 위하여 멸치액젓을 활성탄, 활성백토. 알루미늄옥사이드, 규조토 및 celite의 농도를 달리하여 첨가하고 상온에서 60분간 교반한 후 0.45$\mu$m membrane filter로 감압여과 한 다음 탈색률, 총질소, 아미노태질소, 불용성질소, TMA 및 침전생성 억제율을 측정하였다. 탈색율은 활성탄과 활성백토를 첨가하였 때 높았으며 $5\%$ 첨가농도에서 $32\~33\%$의 탈색효과를 나타내었으나 TMA 함량은 각 처리구에서 $7\%$ 이하의 감소를 나타내어 탈취효과는 기대할 수 없었다. 멸치액젓 저장중 침전물의 생성억제 효과는 $5\%$ 처리농도에서 활성백토 $82\%$, 규조토 $73\%$ 및 $Al_2O_3$ $70\%$로 나타났다.

• 대한임베디드공학회논문지
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• 제17권3호
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• pp.149-155
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• 2022

This paper proposes a method for estimating the road surface condition and tilt angle using an inertial measurement unit (IMU) to improve the safety in the use of mobility aids for the elderly. The measurements of the accelerometers of the IMU usually include the accelerations caused by not only the gravitational force but also linear and rotational motions. Thus, the gravitational accelerations are first extracted using several physical constraints and then incorporated into the Kalman filter to estimate the tilt angle. In addition, because the magnitudes of the accelerations produced by the rotational motions (roll and pitch motions) vary with the road surface condition, a criterion based on such accelerations is presented to classify the condition of the road surface. The obtained road surface condition and tilt angle are finally combined to provide the safety information (e.g., safe, warning, and danger) for the user to improve the walking safety. Experiments were carried out and the results showed that the proposed method can provide the condition of the road surface, the tilt of the road surface, and the safety information correctly.

• 상하수도학회지
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• 제31권2호
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• pp.125-139
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• 2017

In this paper, the performance of a synthetic fiber filter aimed at high-speed operation and dosed with different coagulants or filter aids was investigated. Without a coagulant, the filter efficiency was about 62% which was greatly enhanced when three types of coagulants namely PAC, Alum, and $FeCl_3$ were used. Among the coagulants tested, PAC was the most effective, giving 91% filter efficiency, followed by Alum with 90%, and $FeCl_3$ with 78%. PAC worked effectively at a very small range of dose, but Alum was relatively effective in a wide range of concentration. Compared with PAC and Alum, $FeCl_3$ provided more or less contant efficiency regardless of its dose but gave the poorest filter efficiency. Moreover, as the inflow turbidity increased, headloss increased and the efficiency decreased at any dose and type of coagulant. The headloss recorded in this particular synthetic fiber filter is not significant as compared to that observed in typical granular filters. The recovery of solids estimated after filter cleaning was about 80% for both PAC and Alum, but poorer at 72% in the case of $FeCl_3$ due to the heavy and large floc characteristics. The recurrence of filter efficiency verified through repetitive filter runs was found to be satisfactory.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 추계학술대회
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• pp.121-123
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• 1995

This paper presents a new method which compensates loss of loudness for digital hearing aids. Loudness grows more rapidly in frequency domain with substantial shifts of hearing threshold, so that loud sounds reach the uncomfortable sound level (UCL) at about the same physical stimulus level as with normal hearing. The result is a compression of the available dynamic range of hearing. Many techniques have been developed to compensate for hearing losses. In this paper, we propose a digital hearing aid which uses a single digital filter for reducing distortion and the fuzzy function to calculate gain factors. This function describes how much gain is needed for every frequency to restore loudness perception of a normal ear.

• 한국환경과학회지
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• 제18권3호
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• pp.289-298
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• 2009

The blue-green algae which caused odor problem in the tap water are difficult to precipitate in sedimentation basin and clogged the filter void rapidly. The studies of this paper were not only oxidation, coagulation and sedimentation processes for effectively removing blue-green algae but yellow clay and polyamine for verification as coagulants aids. The results of this research are summarized as follows: Higher ozone dose(C) and longer contact time(T) were needed for a high degree of removing blue-green algae efficiency. the removal rate of blue-green algae was proportional to the $C\times T$ value. The removal percent of chlorophyll-a by sedimentation and filter without pre-ozonation was about 75% but 1 mg/L pre-ozonation could increase the removal percent of chlorophyll-a to 99% and more pre-ozonation could remove completely. Though the removal efficiency of turbidity could increased by high dose of chlorination, the dissolved organic carbon was increased. More chlorine dose from 4 to 10 mg/L dissolved organic carbon was decreased. Using yellow clay as coagulant aids increased density of floc so the settling velocity of floc become rising but polyamine could not increase settling velocity of floc though it could formated large floc.

• 한국전자통신학회논문지
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• 제14권6호
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• pp.1249-1256
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• 2019

본 논문에서는 보청기의 음향궤환 및 잡음을 제거하기 위한 새로운 알고리즘을 제안한다. 이 알고리즘은 기존의 FIR 구조를 이용하는 대신 신경망 적응예측필터를 이용한 심층학습 알고리즘으로 궤환 및 잡음제거 성능을 향상시킨다. 먼저 궤환제거기가 마이크 신호에서 궤환신호를 제거하고, 이어서 Wiener 필터기법을 이용하여 잡음을 제거한다. 잡음 제거는 음성신호가 가진 주기적 성질에 따라 선형예측모델을 이용하여 잡음이 포함된 음성신호로부터 음성을 추정해내는 것이다. 한 루프 안에 포함된 두 적응 시스템의 안정적 수렴을 보장하기 위해 궤환제거기 및 잡음제거기의 계수 업데이트를 분리하여 실시하며 제거 후 생성된 잔차신호를 이용하여 수렴시키는 과정을 진행한다. 본 연구에서 제안한 궤환 및 잡음제거기의 성능을 검증하기 위하여 시뮬레이션 프로그램을 작성하고 모의실험을 수행하였다. 실험 결과, 제안한 심층학습 알고리즘을 사용하면 기존의 FIR 구조를 사용하는 경우보다 궤환제거기에서 약 10 dB의 SFR(: Signal to Feedback Ratio), 잡음제거기에서 약 3 dB의 SNRE(: Signal to Noise Ratio Enhancement) 개선효과를 얻을 수 있는 것으로 확인되었다.

• 한국식품과학회지
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• 제36권2호
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• pp.321-328
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• 2004

오디 과실을 이용한 고부가가치의 가공식품의 개발에 관한 연구 일환으로 먼저 최소가공기술을 이용한 오디 과실주스 제조 방법을 조사하였다. 오디 과실의 물추출액을 면포여과, 감압여과(Whatman No. 4 filter paper를 이용한) 및 원심분리를 각각 실시한 결과 원심분리가 가장 좋은 청징효과를 나타내었다. 그리고 여러 여과보조제 및 청징제를 첨가한 후 원심분리하여 얻은 오디 과실즙의 색의 변화는 처리한 여과보조제, 청징제 및 청징 효소의 종류에 따라 차이가 있었으며, 특히 casein, gelatin, chitin, chitosan 및 PVPP는 오디 색소를 강하게 흡착하였으며, 그리고 청징효소 중 ${\alpha}-amylase$ 처리구가 가장 좋은 청징효과를 나타내었다. 다음, 오디 과즙을 원심분리한 후 $0.01\;{\mu}m$ 막여과를 실시한 결과 오디주스의 청징효과가 매우 우수하였으나 한외여과방법은 오디 색소의 강한 흡착으로 적절하지 않았다. 한편, 4가지 갈변저해제 처리에 따른 오디 과실주스의 갈변억제 효과를 측정한 결과 200ppm sodium hydrosulfite 처리구가 가장 갈변억제 효과가 우수하였으며, 아울러 0.1% L-ascorbic acid(L-AsA) 및 citric acid(CA)도 갈변억제 효과가 있었다. 그리고 위의 3가지 갈변저해제를 2중 복합병행 처리한 결과 0.1% L-AsA+0.1% CA 처리구가 가장 좋은 갈변억제 효과를 나타내었다. 마지막으로 관능검사를 실시한 결과 오디주스의 최적 당/산비는 40-50이었으며, 또한 상업적 살균 온도($85-90^{\circ}C$)에서 처리시간은 10분이 가장 적합함을 알 수 있었다.

• 전기학회논문지
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• 제65권11호
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• pp.1868-1878
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• 2016

This paper proposes a novel velocity estimator for long-term underwater navigation of autonomous underwater vehicles(AUVs). Provided that an external position fix is not given, a viable goal in designing a underwater navigation algorithm is to reduce the divergence rate of position error only using the sporadic velocity information obtained from Doppler velocity log(DVL). For such case, the performance of underwater navigation eventually depends on accuracy and reliability of external velocity information. This motivates us to devise a velocity estimator which can drastically enhance the navigation performance even when the DVL measurement is unavailable. Incorporating the Gertler-Hagen hydrodynamics model of an AUV with the measurement models of velocity and depth sensors, the velocity estimator design problem is resolved using the extended Kalman filter. Different from the existing methods in which an AUV simulator is regarded as a virtual sensor, our approach is less sensitive to the model uncertainty often encountered in practice. This is because our velocity filter estimates the simulator errors with sensor aids and furthermore compensates these errors based on the indirect feedforward manner. Through the simulations for typical AUV navigation scenarios, the effectiveness of the proposed scheme is demonstrated.