Features of EEG Signal during Attentional Status by Independent Component Analysis in Frequency-Domain

In this paper, electroencephalographic (EEG) signal of one among subjects measured biosignal with visual evoked stimuli inducing the concentration was analyzed to detect the changes in the attention status during attention task fulfillment from January to February, 2011. The independent component analysis (ICA) was applied to EEG signals to isolate the attention related innate source signal within the brain and Electroculogram (EOG) artifact from measured EEG signals at the scalp. The consecutive accumulation of short time Fourier transformed (STFT) attention source signal with excluded EOG artifact can enhance the regular depiction of EPOCH graph and spectral color map representing time-varying pattern. The extracted attention indices associated with somatosensory rhythm (SMR: 12-15 Hz), and theta wave (4-7 Hz) increase marginally over time. Throughout experimental observation, the ICA with STFT can be used for the assessment of participants' status of attention.ope

An Optimal Mill Work

Maste

클러스터 컴퓨팅 환경에서의 분산 대량 FEM 데이터의 과학적 병렬 가시화

학위논문(석사)--서울대학교 대학원 :협동과정 계산과학전공,2005.Maste

Oceanic ambient noise generated by breaking surf in the sandy coast

Low-frequency ocean noise has recently been of concern with relation to behavior of marinemammals [1]. It is reported that underwater noise generated by breaking waves in surf zone greatlycontributes low-frequency oceanic ambient noise in coastal waters [2]. Generation mechanisms ofunderwater noise due to breaking waves in surf zone have been studied by some researchers [3, 4].Underwater noise was measured to investigate the effect of surf noise on oceanic ambient noise in the eastern sandy coast of the middle part of the Korean Peninsula. The measurements results of ocean noise generated by breaking waves in the surf zone are discussed. And it is considered that the effect of the surf noise on the oceanic ambient noise.in coastal waters [2]. Generation mechanisms ofunderwater noise due to breaking waves in surf zone have been studied by some researchers [3, 4].Underwater noise was measured to investigate the effect of surf noise on oceanic ambient noise in the eastern sandy coast of the middle part of the Korean Peninsula. The measurements results of ocean noise generated by breaking waves in the surf zone are discussed. And it is considered that the effect of the surf noise on the oceanic ambient noise.1

APPARATUS FOR MEASURING OF GEOACOUSTIC PROPERTIES FOR OCEAN SEDIMENTS LAYER

본 발명은, 해저 퇴적층 시료가 수집된 피스톤코어의 길이방향을 따라 이동하면서, 피스톤코어에 음파신호 를 송신하고 피스톤코어에 투과된 음파신호를 통해 해저 퇴적층의 퇴적 높이별 음파 속도 및 음파 감쇠를 측정하는 해저 퇴적층 음향특성 측정 장치에 관한 것이다. 본 발명에 의하면, 홀더에 의해 수직 고정된 피스톤코어의 길이방향을 따라 도파관이 수직 이송되고, 도파 관의 전파매질로 물이 사용되며, 도파관에 결합된 송신기에 의해 송신된 송신음파신호와 송신기로부터 발 생되어 피스톤코어에 투과하여 수신기에 수신된 수신음파신호에서 40 kHz ~ 1 MHz 주파수 대역의 음파신호 만을 필터링 피스톤코어에 수집된 해저 퇴적층 시료에 대한 음파 속도 및 감쇠를 해저 퇴적층의 퇴적 높이 별로 측정함으로써, 실제 해수중에서 측정된 해저 퇴저층의 음향특성과 유사한 결과를 제공하고, 피스톤코 어를 고정시키는 홀더가 수평방향으로 유동 가능하도록 마련됨에 따라, 해저 퇴적층 시료 채취 시에 충격 에 의해 소정의 휨이 발생된 피스톤코어의 사용 또한 가능하여, 측정을 위한 시료 선택에 편의를 제공하 는 효과가 있다

Synthesis of Electrocardiogram V Lead Signals from Limb Lead Measurement using R peak Aligned Generative Adversarial Network

Recently, portable electrocardiogram (ECG) hardware devices have been developed using limb-lead measurements. However, portable ECGs provide insufficient ECG information because of limitations in the number of leads and measurement positions. Therefore, in this study, V-lead ECG signals were synthesized from limb leads using an R-peak aligned generative adversarial network (GAN). The data used the Physikalisch-Technische Bundesanstalt (PTB) dataset provided by PhysioNet. First, R-peak alignment was performed to maintain the physiological information of the ECG. Second, time domain ECG was converted to bi-dimensional space by ordered time-sequence embedding. Finally, the GAN was learned through the pairs between the modified limb II (MLII) lead and each chest (V) lead. The result showed that the mean structural similarity index (SSIM) was 0.92, and the mean error rate of the percent mean square difference (PRD) of the chest leads was 7.21%.restrictio

Snapping shrimp noise in the coastal sea of Korea

Snapping shrimp noise at a site in the coasts of the southern sea and the Yellow Sea of Korea was measured for one day on August,2001 and 2002, respectively. The waveform of the snapping shrimp noise was a temporal waveform with a positive broad peak pressure at initial time and a negative narrow peak pressure at after the time. The frequency spectrum of the snapping shrimp noise broadly appeared between 0 and 100 kHz. Main frequency response bandwidth was between 2and 20 kHz. The diurnal variation of snapping shrimp noise spectra was dominant at sunset and sunrise. The snapping shrimp noise observed in the coast of the southern sea of Korea dominantly affected the ambient noise levels between 2 and 20 kHz, while that in the coast of the Yellow Sea of Korea weakly affected the ambient noise levels. Snapping shrimp noise was also measured in anechoic water tank under laboratory conditions. Typical waveform of the snapping shrimp noise was similar to that measured in the coast. The frequency spectrum was broadly appeared up to about 400 kHz.1

천해에서의 소형 무인수상선 방사소음 측정 및 특성 분석

수상선 또는 잠수정이 발생시키는 수중방사소음의 크기 및 특성을 정확하게 파악하는 것은 해양 생태계 보호뿐만 아니라 조선업, 군사적인 목적과 관련해서도 중요하다. 근래에는 해양 무인체가 활발하게 개발 및 활용됨에 따라 이들이 발생시키는 수중방사소음에 대해서도 관심이 증대되고 있다. 하지만 해양 무인체에 대해서 수중방사소음을 측정하고 평가할 수 있는 공인인증체계는 아직까지 전세계적으로도 구축된 바 없다. 본 연구자들은 이러한 공인인증체계 구축을 위한 기초 작업으로서, 천해 환경에서 수중방사소음을 정확히 측정할 수 있는 조건을 파악하고자 상용 소형 무인수상선 1 종을 이용한 실해역 측정을 수행하였다. 측정 시, 소형 무인수상선은 두 가지 선속으로 운행하였으며, 수중청음기 계류지점으로부터 무인수상선까지의 거리를 몇 가지로 바꾸어 가며 운행하였다. 우리는 이 운행시간 동안의 수중청음기에 수신된 소음 신호를 분석함으로써, 무인 수상선의 수중방사소음 측정에 적절한 수중청음기 거리, 소음 분석에 사용하기 적절한 선박 운행 구간, 신뢰할 만한 음원레벨을 획득할 할 수 있는 주파수 구간 등을 도출할 수 있었다. 이러한 결과는 향후에 해양 무인체 수중방사소음 평가 절차서를 확립하는 데에 실증적인 근거자료로서 활용될 수 있을 것이다. [해양수산부 재원으로 해양수산과학기술진흥원의 지원을 받아 수행된 연구임(RS-2023-00256122)]2

Influence of a Warm Eddy on Low-frequency Sound Propagationin the East Sea

It is well known that sound waves in the sea propagates under the influence of sea surface andbottom roughness, the sound speed profile, the water depth, and the density of sea floor sediment. Inparticular, an abrupt change of sound speed with depth can greatly affect sound propagation through aneddy. Eddies are frequently generated in the East Sea near the Korean Peninsula. A warm eddy withdiameter of about 150 km is often observed, and the sound speed profile is greatly changed within about400 m of water depth at the center by the eddy around the Ulleung Basin in the East Sea. The characteristicsof low-frequency sound propagation across a warm eddy are investigated by a sound propagation model inorder to understand the influence of warm eddies. The acoustic rays and propagation losses are calculatedby a range-dependent acoustic model in conditions where the eddy is both present and absent. We foundthat low-frequency sound propagation is affected by the warm eddy, and that the phenomena dominate theupper ocean within 800 m of water depth. The propagation losses of a 100 Hz frequency are variable within±15 dB with depth and range by the warm eddy. Such variations are more pronounced at the deep sourcenear the sound channel axis than the shallow source. Furthermore, low-frequency sound propagation fromthe eddy center to the eddy edge is more affected by the warm eddy than sound propagation from the eddyedge to the eddy center.33Nscopuskc