• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.116-126
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• 2008

In gas hydrate survey, seismic amplitude and frequency characteristics play a very important role in determining whether gas hydrate exists. According to the variation of source frequency and scatterer size, we study seismic amplitude characteristics using elastic modeling applied at staggered grids. Generally speaking, scattering occurs in proportion to the square of source frequency and the scatterer volume, which has an effect on seismic amplitude. The higher source frequency is, the more scattering occurs in gas hydrate bearing zone. Therefore, BSR is hardly observed in high frequencies. On the other side, amplitude blanking zone and BSR is clearly observed in lower frequencies although the resolution is poor as a whole. Seismic reflections traveling through free-gas layer below gas hydrate bearing zone decay so severely a high frequency component that a low frequency term is dominant. Amplitude anomaly of BSR result from high acoustic impedance contrast due to free-gas, which is a very crucial factor to estimate gas hydrate bearing zone. Seismic frequency analysis is carried out using wavelet transform method that frequency component could be decomposed with time variation. In application of wavelet transform to the seismic physical experiments data, we can observe that reflections traveling through air layer, which corresponds to the free-gas layer, decay a high frequency component.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.771-777
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• 2008

In this paper, a frequency doubler using modified time-delay technique is proposed. A voltage controlled delay line (VCDL) in the proposed frequency doubler compensates the group delay time mismatching between input and delayed signal. With the group delay time matching and waveform shaping using the adjustable Schmitt triggers, the unwanted fundamental component($f_0$) and the higher order harmonics such as third and fourth are diminished excellently. In result, only the doubled frequency component($2f_0$) appears dominantly at the output port. The frequency doubler is designed at 1.15 GHz of $f_0$ and fabricated with TSMC $0.18\;{\mu}m$ CMOS process. The measured output power at $2f_0$ is 2.67 dBm when the input power is 0 dBm. The obtained suppression ratio of $f_0,\;3f_0$, and $4f_0$ to $2f_0$ are 43.65, 38.65 and 35.59 dB, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.1
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• pp.1-6
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• 1975

The sea noise of moving trawl net was recorded by an underwater tape recorder which was set wireless, and was analyzed by a sound level meter and an octave-band analyzer. The frequency distribution of sea noise of the moving otter trawl net ranged from DC to 5000 Hz, and the dominant frequency zone ranged from 500 Hz to 700 Hz, and the maximum sound pressure is about 22 dB at the otter trawl net. The main sound source of the sea noise from the moving trawl net was found to be sea noise due to the resistance of the ground rope against the sea bottom.

• 한국해양학회지
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• v.27 no.3
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• pp.228-236
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• 1992

Internal temperature oscillations of tidal periods were studied using data observed by a thermistor chain in summer of 1980 off Jukbyun on the mid-east coast of korea. The vertical stratification was well established during the observation period. The spectral energy was found to be predominant in the semidiurnal tidal band and its energy increased with depth with maximum near the bottom. The coherence in the semidiurnal band between different depths is high with a small phase difference. The results suggest the existence of the internal tide of semidiurnal period. The amplitude of internal tide was of the order of 10 m and the largest just before the disappearance of the internal tide signal.

• Phonetics and Speech Sciences
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• v.11 no.1
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• pp.9-18
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• 2019

The purpose of this study is to determine whether the mean fundamental frequency (F0) changes depending on language, task, or language proficiency for Korean-English bilinguals. A total of forty-eight Korean-English speakers (28 balanced bilinguals and 20 Korean dominant bilinguals) participated in the study. Participants were asked to read aloud two types of tasks in English and Korean. For statistical analyses, the language ${\times}$ task two-way repeated ANOVAs were conducted within the balanced bilingual group first, and then group ${\times}$ language two-way mixed ANOVAs. The results showed that the females in both bilingual groups changed their mean F0 depending on the language they used and the tasks (p<.05), whereas no significant results were found in the males in either group under any conditions. The mean fundamental frequency in the Korean reading task was significantly higher than that in the English reading task for females in both balanced and Korean dominant bilingual groups. Thus, changes in mean F0 depending on language and context may reflect gender-specific characteristics, and females seem to be more sensitive to the socio-cultural standards that are imposed on them.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2003.05a
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• pp.107-110
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• 2003

본 연구에서는 EEG를 이용하여 정신집중 시, 뇌 기능의 변화를 알아보았다. 실험은 건강한 남녀 고교생 9명을 대상으로 EEG는 Fp1. Fp2, F3, F4, P3, P4, T5, T6, O1, O2의 10위치에 대하여 정신집중 작업 진의 3분과 작업 시 30분간을 측정하였다. 작업은 PC를 이용하였으며 모니터 상의 움직임에 집중하고 목표자극을 탐지하였을 때 신속하게 적절한 반응키를 누르도록 하였다. 각 주파수 대역은 theta2와 (6.0-8.0Hz), alpha1파 (8.0-10.0Hz), alpha2파(10.0-12.0Hz)로 구분하였으며 비대칭지수를 이용하여 분석하였다. 그 결과, 정신집중 작업 시 theta1, theta2, alpha1대역에서 두정엽의 우반구과 측두엽 및 후두엽의 좌반구영역이 우세하였다. 이들 영역은 시갈, 지각, 움직임 기능을 수행하며 theta2파가 주의, alpha1파가 각성 관련이다. 이상의 결과에서 두정엽의 우반구와 측두엽 및 후두엽의 좌반구영역의 theta1파, theta2파, alpha1파가 정신집중 작업 시 중요한 역할을 담당하는 것으로 나타났다.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.403-405
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• 2003

An iterative Green's function method (IGFM) is introduced to analyze complex electromagnetic waveguide structures in view of the university student. The IGFM utilizes the Green's function and iteration scheme. The physical mechanism with simple mathematical equations is used to formulate the IGFM. Scattering characteristics of a standard E-plane T-junction in a parallel-plate waveguide are theoretically investigated in terms of the IGFM. Numerical computations illustrate the characteristics of resection and transmission powers versus frequency. A dominant-mode solution is presented and compared with the higher-mode solutions.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.10
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• pp.1086-1097
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• 1990

The design of multivariable control systems using the Inverse Nyquist Array method is described in this paper. The INA is a simple design technique, which permits a designer to achieve his objectives for a controller specification in a step-by-step fashion using Gershgorin band and Ostrowski circle. The application to a multivariable system of CANDU nuclear power plant with 5 inputs, 8 outputs, and 24 state variables is reviewed and the simulation shows satisfactory results.

• Proceedings of the Speleological Society Conference
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• 2001.06a
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• pp.3-29
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• 2001

파파리반딧불이(H papariensis)의 생태학적 특성을 규명하고자 서식처 환경, 개체군, 고도별 출현양상과 지역별 분포양상, 발광양상, 교미행동을 조사하였다. 춘천시 서면 지암리에서 H. papariensis 성충의 개체군 밀도를 1998년 5월부터 7월에 걸쳐 조사하였으며, 전체 채집 개체수는 703개체였다. 이중 수컷은 680개체, 암컷은 23개체를 채집하였다. 지암리에서 전체 출현기간은 50여 일로 추정되었다. 처음 출현한 날로부터 2주에서 3주 사이에 최대 정점을 나타내었으며, 이후 점진적으로 감소하는 출현양상을 나타내었다. 수컷 680개체중 47개체는 재 포획되었으며, 이로서 추정된 최대수명은 6일 이상, 평균수명은 3.26일로 나타났으며, 수컷과 암컷의 상대적인 성비는 27.5/l로 나타났다. 한국산 Hotaria속 반딧불이 2종의 고도별 출현 및 지역별 분포양상에 대하여 1999년 5월부터 7월까지 18개 지역을 선정하여 조사하였다. 전체 채집개체수는 1096개체였으며 이중 H. papariensis는 584개체, H unmunsana는 512개체였다 두 종은 제주도를 제외한 전 조사지역에서 공서 하고 있었으며 H. papariensis는 북쪽지역에 우세하게 분포하였고 H. unmunsana는 남쪽지역에 우세하게 분포하는 양상을 나타내었다. 성충 반딧불이의 최고 출현성기는 고도가 높아질수록 늦어지는 경향을 나타내었다. 고도별로 200m 이하 지역에서는 6월 초순에서 중순, 200-400m 지역에서는 6월 중순에서 말경, 400-600m 지역에서는 6월말 경부터 7월 초순, 600-800m 지역에서는 7월 초순부터 중순에 각각 최고 성기를 나타내었다. H. papariensis의 암컷과 수컷의 발광양상을 분석하고자 정지발광과 구애 발광을 구분하여 조사하였고 각각의 발광지속시간과 발광주기를 구분하여 측정하였다. 수컷의 발광지속시간은 정지발광(0.12초)보다 구애발광(0.17초)에서 1.4배 증가하였으며 암컷의 발광지속시간은 정지발광(0.15초)보다 구애발광(0.19초)에서 1.5배 증가하였다. 발광주기는 수컷에서 정지발광(1.26초)보다 구애발광(1.12초)에서 0.88배 감소하였고, 암컷에서 정지발광(2.99초)보다 구애발광(1.06초)에서 0.35배 감소하였다. 발광양상에서 발광주파수는 수짓의 정지발광에서 0.8 Hz, 수컷 구애발광에서 0.9 Hz, 암컷의 정지발광에서 0.3 Hz, 암컷의 구애발광에서 0.9 Hz로 각각 나타났다. H. papariensis의 발광파장영역은 400 nm에서 700 nm에 이르는 모든 영역에서 확인되었으며 가장 높은 첨두치는 600 nm에 있고 500에서 600 nm 사이의 파장대가 가장 두드러지게 나타났다. 발광양상과 어우러진 교미행동은 Hp system과 같은 결과를 얻었다.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.9-16
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• 1997

Ferroelectric $Pb_5Ge_{3-x}Ti_xO_{11}$(x=0, 0.015, 0.021, 0.03) single crystals were obtained from the melt by the Czochralski method. Grown crystals were pale brownish yellow and fully transparent. The dielectric relaxation of the $Pb_5Ge_{3-x}Ti_xO_{11}$ single crystals has been studied in the frequency range from 100 Hz to 10 MHz between $20^{\circ}C$ and $600^{\circ}C$. From the results of the these measurements. the temperature of the permittivity maximum was shifted to low temperature with increasing Ti content and the permittivity maximum decreased with increasing Ti content. The frequency dependent dielectric response of $Pb_5Ge_{3-x}Ti_xO_{11}$ single crystals exhibits a Debye type relaxation, with a distribution of relaxation times. Dielectric behavior is characteristic of carrier-dominated response.