• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.187-190
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• 2002

본 논문에서는 잡음 환경에서의 사람의 청각 시스템에서의 신호 에너지에 대한 지각(perception) 패턴을 나타내는 임계 대역에서의 여기(excitation)에너지와 이러한 신호 에너지 사이의 지각적인 간섭 효과를 나타내는 마스킹 특성을 이용하여 지각적인 컨벌루션 잡음(covolutional noise)해석을 통한 잡음 제어 기법을 연구하였다. 이러한 지각적 컨벌루션 잡음은 지각 영역에서 잡음 에너지에 의한 간섭 현상의 영향을 나타내며, 신호의 지각 적인 특성 변화 및 부가 잡음(additional noise) 제어 후에 신호 내에 잔존하는 잔여 노이즈를 반영하는 것이다. 실험 결과 부가 잡음 제어 필터와 컨벌루션 잡음 제어 필터가 대등한 노이즈 제어 성능을 나타내었으며, 다양한 잡음 환경에서 이러한 지각 영역에서의 부가 잡음 제어와 컨벌루션 잡음 제어를 통해 높은 SNR비 개선과 더불어 MOS 측정을 통해서도 높은 음질을 보장할 수 있음을 확인 할 수 있었다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.295-298
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• 2004

본 논문에서는 잡음에 오염된 신호의 지각관계를 해석하여 지각 필터 응답 제어를 통한 음성 신호 개선 알고리즘을 제안한다. 음성 신호 개선 기법은 단일 채널환경에서 사람의 청각시스템에서의 주파수 변별력을 나타내는 각각의 임계대역에 대한 전체 에너지를 나타내는 임계대역 에너지의 지각적인 확산의 영향 즉, 마스킹 확산의 영향을 나타내는 자극에너지를 이용하여 신호와 잡음 에너지에 의해 변화하는 잡음에 의한 신호의 마스킹 구간을 검출하여 묵음 구간 추출 잡음 필터응답과 추정 잡음 오차를 보상시킨 필터응답을 통한 지각 필터 응답을 보상하여 신호를 개선하는 방법이다. 실험 결과 제안한 방법을 통해 SNR에 개선과 음질 개선 효과를 얻을 수 있음을 테스트를 통해 확인하였다.

• Journal of Broadcast Engineering
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• v.8 no.1
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• pp.11-18
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• 2003

In this paper, we introduce a novel signal quality enhancement algorithm with a perceptual interference analysis and perceptual convolutional noise suppression. A perceptual convolutional noise is reflected in the audible disturbance that can still be recognized after the additional noise suppression and tonality change which is caused by the noise energy excitation. The enhancement system is organized with a perceptual additional noise suppression part and a perceptual convolutional noise suppression part. Experimental results show that these two parts have an equivalent quality enhancement performance.

• The Journal of the Acoustical Society of Korea
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• v.19 no.8
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• pp.12-21
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• 2000

In this paper, we propose a novel hearing aid algorithm for sensorinural hearing loss restoration with multi-channel(band) dynamic range compression and psychoacoustics. In this way, we can present a normal perception condition to the impaired listener. The proposed algorithm make loudness scaling function achieve proper loudness level, and analysis masking property for the signal will be perceived to impaired listener, and then, restore normal spectral contrast using SMR(signal-to-masking ratio) defined by distance between the level of each frequency and masking threshold.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.1
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• pp.47-54
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• 2015

In this study, we developed strategies for pre-processing GNSS data for the purpose of separating geodetic factors from crustal deformation due to the earthquakes. Before interpreting GNSS data analysis results, we removed false signals from GNSS coordinate time series. Because permanent GNSS stations are located on a large tectonic plate, GNSS position estimates should be affected by the tectonic velocity of the plate. Also, stations with surrounding trees have seasonal signals in their three-dimensional coordinate estimates. Thus, we have estimated the location of an Euler pole and angular velocities to deduce the plate tectonic velocity and verified with geological models. Also, annual amplitudes and initial phases were estimated to get rid of those false annual signals showing up in the time series. By considering the two effects, truly geodetic analysis was possible and the result was used as preliminary data for analyzing post-seismic deformation of the Korean peninsula due to the Tohoku-oki earthquake.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.1
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• pp.87-96
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• 2012

The U.S. Geological Survey (USGS) announced that an earthquake of 9.0 magnitude had occurred near the east coast of Japan on March 11, 2011, resulting in a displacement of the crust of about 2.4 meters. The Korean peninsula is located on the Eurasian tectonic plate that stretches out to Japan; therefore, there is a high possibility of being affected by an earthquake. The Korean GPS CORS network operated by the National Geographic Information Institute (NGII) was processed for ten days before and after the earthquake. Both static and kinematic baseline processing were tested for the determination of crustal deformation. The static baseline processing was performed in two scenarios: 1) fixing three IGS stations in China, Mongolia and Russia; 2) fixing SUWN, one of the CORS networks in Korea, in order to effectively verify crustal deformation. All data processing was carried out using Bernese V5.0. The test results show that most of the parts of the Korean peninsula have moved to the east, ranging 1.2 to 5.6 cm, compared to the final solution of the day before the earthquake. The stations, such as DOKD and ULLE that are established on the islands closer to the epicenter, have clearly moved the largest amounts. Furthermore, the station CHJU, located on the southwestern part of Korea, presents relatively small changes. The relative positioning between CORS confirms the fact that there were internal distortions of the Korean peninsula to some extent. In addition, the 30-second interval kinematic processing of CORS data gives an indication of earthquake signals with some delays depending on the distance from the epicenter.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.67-70
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• 2009

송수신기 일체형인 소형 루프 시스템을 해저 전자탐사 기술의 적용 가능을 확인하는 과정의 시작 단계로 자기 쌍극자 송신원을 이용한 층서구조에서의 전자가 반응을 계산 하였다. 전도성인 해양 환경에서 측정되는 신호의 크기가 작은 한계가 있지만 전자기장 반응 해석을 통행 지하 하부의 정보를 얻을 수 있었다. 기반암 위의 층이 바닷물보다 저항성인 해저 지각인 경우와 전도성인 열수광상인 경우에 따라 반응이 달라짐을 확인하였고, 그 층의 두께에 따라서 변화하는 전자기 반응을 계산하여 탐지 가능한 층의 두께를 예상할 수 있었다. 송수신기가 모두 바다 속에 위치하기 때문에 송수신기의 배치 방법과 송수신기가 해저면에서 떨어지게 될 때 신호의 반응 변화를 파악하였다. 해양 소형 루프 전자탐사의 실제 적용을 위해서 이상의 연구들이 기초가 될 것으로 기대된다.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.1-14
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• 2008

We present a method for interpreting seismic records with arrivals and waveforms having characteristics which could be generated by extremely inhomogeneous velocity structures, such as non-typical oceanic crust, decollement at subduction zones, and seamounts in oceanic regions, by comparing them with synthetic waveforms. Recent extensive refraction and wide-angle reflection surveys in oceanic regions have provided us with a huge number of high-resolution and high-quality seismic records containing characteristic arrivals and waveforms, besides first arrivals and major reflected phases such as PmP. Some characteristic waveforms, with significant later reflected phases or anomalous amplitude decay with offset distance, are difficult to interpret using only a conventional interpretation method such as the traveltime tomographic inversion method. We find the best process for investigating such characteristic phases is to use an interactive interpretation method to compare observed data with synthetic waveforms, and calculate raypaths and traveltimes. This approach enables us to construct a reasonable structural model that includes all of the major characteristics of the observed waveforms. We present results here with some actual observed examples that might be of great help in the interpretation of such problematic phases. Our approach to the analysis of waveform characteristics is endorsed as an innovative method for constructing high-resolution and high-quality crustal structure models, not only in oceanic regions, but also in the continental regions.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.189-192
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• 2000

본 논문에서는 청각 장애인의 보다 향상된 보청 환경을 조성하고자 청각손실을 심리음향 모델을 적용하여 감음 신경성 난청을 보정하는 알고리즘을 제안한다. 제안한 알고리즘에서는 난청의 유형은 내이에서부터 중추 뇌에 걸친 감음계와 신경계의 장애에서 비롯되는 감음신경성 난청(sensorineural hearing loss)으로 주파수 영역상에서 MTH(minimum hearing threshold)가 균일하지 않게 상승하게되어 가청영역이 좁아지는 문제점을 해결하기 위한 방법으로 각각의 주파수 밴드마다 멀티밴드 압축 알고리즘을 적용하였다. 그러나 이 경우 각각의 주파수 밴드에 따른 서로 다른 가청 영역의 영향에 의한 변형된 스펙트럼 모양으로 인해 spectral contrast reduction과 변형된 마스킹 특성으로 인해 음성 변별력에 제한을 가하게 된다. 이것은 주변 주파수 성분들에 의한 마스킹 효과에 의한 것으로, 신호에 대한 난청인이 느끼는 지각 영역(perceptual domain)에서의 해석과 심리음향 모델 파라미터를 통한 보청기의 개발이 이루어져야 하며, 본 논문에서 그 알고리즘을 적용하였다.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.105-113
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• 2009

The interpretation of observed waveform characteristics identified in refraction and wide-angle reflection data increases confidence in the crustal structure model obtained. When calculating traveltimes and raypaths, wavefront methods on a regular grid based on graph theory are robust even with complicated structures, but basically compute only first arrivals. In this paper, we develop new algorithms to compute traveltimes and raypaths not only for first arrivals, but also for fast and later reflection arrivals, later refraction arrivals, and converted waves between P and S, using the modified wavefront method based on slowness network nodes mapped on a multi-layer model. Using the new algorithm, we can interpret reflected arrivals, Pg-later arrivals, strong arrivals appearing behind Pn, triplicated Moho reflected arrivals (PmP) to obtain the shape of the Moho, and phases involving conversion between P and S. Using two models of an ocean-continent transition zone and an oceanic ridge or seamount, we show the usefulness of this algorithm, which is confirmed by synthetic seismograms using the 2D Finite Difference Method (2D-FDM). Characteristics of arrivals and raypaths of the two models differ from each other in that using only first-arrival traveltime data for crustal structure analysis involves risk of erroneous interpretation in the ocean-continent transition zone, or the region around a ridge or seamount.