The damage to structures during an earthquake can be varied depending on the frequency characteristics of seismic waves and the geological properties of the ground. Therefore, considering such attributes in the design ground motions is crucial. The Korean seismic design standard (KDS 17 10 00) provides design response spectra for various ground classifications. If required for time-domain analysis, ground motion time series can be either selected and adjusted from motions recorded at rock sites in intraplate regions or artificially synthesized. Ground motion time series at soil sites should be obtained from site response analysis. However, in practice, selecting suitable ground motion records is challenging due to the overall lack of large earthquakes in intraplate regions, and artificially synthesized time series often leads to unrealistic responses of structures. As an alternative approach, this study provides a case study of generating ground motion time series based on the hybrid broadband ground motion simulation of selected scenario earthquakes at sites in the Nakdonggang delta region. This research is significant as it provides a novel method for generating ground motion time series that can be used in seismic design and response analysis. For large-magnitude earthquake scenarios close to the epicenter, the simulated response spectra surpassed the 1000-year design response spectra in some specific frequency ranges. Subsequently, the acceleration time series at each location were used as input motions to perform nonlinear 1D site response analysis through the PySeismoSoil Package to account for the site response characteristics at each location. The results of the study revealed a tendency to amplify ground motion in the mid to long-period range in most places within the study area. Additionally, significant amplification in the short-period range was observed in some locations characterized by a thin soil layer and relatively high shear wave velocity soil near the upper bedrock.

Recently, domestic fishing production of Japanese horse mackerel has been continuously decreasing. To achieve sustainable fishing of this species, it is essential to acquire its target strength (TS) for accurate biomass estimation and to study its ecological characteristics. To date, there has been no TS research using a broadband echosounder targeting Japanese horse mackerel. In this study, for the first time, we synchronized an underwater camera with a broadband frequency (nominal center frequency of 200 kHz, range: 160-260 kHz) to measure the TS according to the body size (16.8-35.5 cm) and swimming angle of the species. The relationship between Japanese horse mackerel length and body weight showed a general tendency for body weight to increase as length increased. The pattern of the frequency spectra (average values) by body length exhibited a similar trend regardless of body length, with no significant fluctuations in frequency observed. The lowest TS value was observed at 243 kHz while the highest TS values were recorded at 180 and 257.5 kHz. The frequency spectra for the swimming angles appeared to be flat at angles of –5, 0, 30, 60, 75, and 80° while detecting more general trends of frequency spectra for swimming angle proved challenging. The results of this study can serve as fundamental data for Japanese horse mackerel biomass estimation and ecological research.

In this work, we developed silver nanowires and a silicon based Schottky junction and demonstrated ultrafast broadband photosensing behavior. The current device had a response speed that was ultrafast, with a rising time of 36 μs and a falling time of 382 μs, and it had a high level of repeatability across a broad spectrum of wavelengths (λ = 365 to 940 nm). Furthermore, it exhibited excellent responsivity of 60 mA/W and a significant detectivity of 3.5 × 1012 Jones at a λ = 940 nm with an intensity of 0.2 mW cm2 under zero bias operating voltage, which reflects a boost of 50%, by using the AC PV effect. This excellent broadband performance was caused by the photon-induced alternative photocurrent effect, which changed the way the optoelectronics work. This innovative approach will open a second door to the potential design of a broadband ultrafast device for use in cutting-edge optoelectronics.

In this study, the frequency response analysis of a bistable electromagnetic vibration energy harvester is performed, based on an electromagnetic oscillator model, to investigate its nonlinear dynamic behaviors. The displacement and current responses are obtained, by the direct integration of the model, with the variations of mechanical and electromagnetic parameters. It is shown that the operating frequency band of the system can be broadened by the increase in mechanical parameters(inertial mass and Q-factor), but it does not depend significantly on any electromagnetic parameters(an external load resistance and the internal resistance of a coil). On the other hand, the output current of the energy harvester is affected only by the electromagnetic parameters (specifically, the sum of two resistances). Thus, the mechanical and electromagnetic parameters of the electromagnetic energy harvester must be designed properly, respectively, for broader and more efficient performance.

선박 및 수중구조물의 고속, 대형화 및 요구조건 강화의 추세에 따라 유동소음 예측기술의 중요성이 강조되고 있다. 항공, 철도 등의 공력소음 분야에서는 음향상사법을 이용하여 순음 및 광대역 유동소음에 대해 활발히 연구되고 있는 반면 조선해양분야에서는 수중추진기의 날개주파수소음에 대해서만 일부 고려되고 있다. 본 논문에서는 날개면 형상의 주요 유동소음발생 메커니즘 뒷날소음을 고려 가능한 FW-H Formulation 1B를 이용하여 수중추진기 및 선저부가물의 기초요소인 수중익에 대해 광대역소음 예측기법을 연구하였다. 기존의 FW-H Formulation 1B는 공기 중의 압력상관관계 모델에 기반하여 구성되어 있어 매질에 대한 일반성 및 정확도의 한계를 가지므로 수중환경에 대해 일반성을 가지는 벽면변동압력 모델로 확장하는 방법론을 제시하였다. 공기 중 날개면의 소음계측결과와 비교해 벽면변 동압력 모델을 이용할 경우 기존모델의 해석결과 대비 5 dB 이내의 오차로 정확도 관점에서의 유용성을 확인할 수 있었으며 전산유체역 학과 벽면변동압력을 이용한 수중환경의 광대역소음해석 절차를 확립하고 수중익의 광대역소음 예측을 수행하였다.

이 연구에서는 Earth Observing System Terra 위성에 탑재된 Moderate Resolution Imaging Spectroradiometer (MODIS) 협대역 방출율(채널 29, 30, 31) 자료와 다중선형회귀모형을 이용하여 지표면 광대역 방출율을 추정하였다. 다중선형회귀모형 도출 및 검증을 위한 분광 방출율 자료는 MODIS University of California, Santa Barbara와 Advanced Spaceborne Thermal Emission and Reflection Radiometer spectral library 의 307종(토양 123종, 식생 32종, 물 19종, 인위적 재료 43종, 바위 90종)을 사용하였다. 도출된 다중선형회귀모형의 결정계수(R 2 )는 0.95 (p< .001)로 높 게 나타났고 또한 이 모형 결과와 이론적 광대역 방출율 값의 평균제곱근오차(Root Mean Square Error)는 0.0070이었다. 그리고 이 연구 결과에 따라 계산된 지표면 광대역 방출율을 선행 연구 Wang et al. (2005)의 결과와 비교하였다. 그 결과 아시아, 아프리카, 오세아니아 지역에서 이 연구와 Wang et al. (2005)의 결과에 대한 1월 평균 지표면 광대역 방출율의 평균제곱근오차는 0.0054이었고 최소와 최대 편차는 각각 0.0027과 0.0067이었으며 이러한 통계 값은 8월에 도 유사하였다. 이 연구에서 다중선형회귀모형에 의하여 계산한 지표면 광대역 방출율은 Wang et al. (2005)의 값과 큰 차이가 없이 비교적 정확하게 산출되었으나 산출 정확성 향상을 위해서는 토지피복특성에 따른 차별화된 회귀모형 적 용 필요성이 제기된다.