• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.3
• /
• pp.71-79
• /
• 2023

It is not efficient to install a maintenance system that measures seismic acceleration and displacement on all bridges and buildings to evaluate the safety of structures after an earthquake occurs. In order to maintain this, an on-site investigation is conducted. Therefore, it takes a lot of time when the scope of the investigation is wide. As a result, secondary damage may occur, so it is necessary to predict the safety of individual structures quickly. The method of estimating earthquake damage of a structure includes a finite element analysis method using approved seismic information and a structural analysis model. Therefore, it is necessary to predict the seismic information generated at arbitrary location in order to quickly determine structure damage. In this study, methods to predict the ground response spectrum and acceleration time history at arbitrary location using linear estimation methods, and artificial neural network learning methods based on seismic observation data were proposed and their applicability was evaluated. In the case of the linear estimation method, the error was small when the locations of nearby observatories were gathered, but the error increased significantly when it was spread. In the case of the artificial neural network learning method, it could be estimated with a lower level of error under the same conditions.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.24 no.6
• /
• pp.277-283
• /
• 2020

In order to improve the ground-motion prediction equation, which is an important factor in seismic hazard assessment, it is essential to obtain good quality seismic data for a region. The Korean Peninsula has an environment in which it is difficult to obtain strong ground motion data. However, because digital seismic observation networks have become denser since the mid-2000s and moderate earthquake events such as the Odaesan earthquake (Jan. 20, 2007, M_L 4.8), the 9.12 Gyeongju earthquake (Sep. 12, 2016, M_L 5.8), and the Pohang earthquake (Nov. 15, 2017, M_L 5.4) have occurred, some good empirical data on ground motion could have been accumulated. In this study, we tried to build a ground motion database that can be used for the development of the ground motion attenuation equation by collecting seismic data accumulated since the 2000s. The database was constructed in the form of a flat file with RotD50 peak ground acceleration, 5% damped pseudo-spectral acceleration, and meta information related to hypocenter, path, site, and data processing. The seismic data used were the velocity and accelerogram data for events over M_L 3.0 observed between 2003 and 2019 by the Korean National Seismic Network administered by the Korea Meteorological Administration. The final flat file contains 10,795 ground motion data items for 141 events. Although this study focuses mainly on organizing earthquake ground-motion waveforms and their data processing, it is thought that the study will contribute to reducing uncertainty in evaluating seismic hazard in the Korean Peninsula if detailed information about epicenters and stations is supplemented in the future.

• Journal of Astronomy and Space Sciences
• /
• v.24 no.4
• /
• pp.417-430
• /
• 2007

The selection of ground stations is one of the essential process of IGS (International GNSS Service) products. High quality GPS data should be collected from the globally distributed ground stations. In this study, we investigated an effect of ground station network selection on GPS satellite ephemeris. The GPS satellite ephemeris obtained from the twelve ground station networks were analyzed to investigate the effect of selection of ground stations. For data quality check, the observations, the number of cycle slips, and multipath of pseudoranges for L1 and L2 were considered. The ideal network defined by Taylor-Karman structure and SOD (Second Order Design) were used to obtain the optimal ground station network.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.6
• /
• pp.5-11
• /
• 1996

This paper is the study for recognizing single vowels of speaker-independent, and we suppose a method of speech recognition using VQ(Vector Quantization)/NN(Neural Network). This method makes a VQ codebook, which is used for obtaining the observation sequence, and then claculates the probability value by comparing each codeword with the data, finally uses these probability values for the input value of the neural network. Korean signle vowels are selected for our recognition experiment, and ten male speakers pronounced eight single vowels ten times. We compare the performance of our method with those of fuzzy VQ/HMM and conventional VQ/NN According to the experiment result, the recognition rate by VQ/NN is 92.3%, by VQ/HMM using fuzzy is 93.8% and by VQ/NN using fuzzy is 95.7%. Therefore, it is shown that recognition rate of speech recognition by fuzzy VQ/NN is better than those of fuzzy VQ/HMM and conventional VQ/HMM because of its excellent learning ability.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2007.05a
• /
• pp.282-284
• /
• 2007

연구 해역의 양식 굴 폐사는 여름철을 지나 수온이 하강하기 시작하는 9월 초순에서 중순경부터 시작되었으며, 강진만 중앙부분 양식장의 경우 조사당시에도 상당수 굴의 폐사가 진행되고 있었다. 병리학적 조사 결과, 각 조사정점별 채집한 굴에서 비브리오 속 세균들이 검출되었으나, 이들 세균은 해수 중에 상존하는 종류로 알려저 있으며, 기생충은 검출되지 않았다. 강진만과 인근한 남해와 산청기상관측소에서 측정된 기온(8${\sim}$9월)은 남해는 2005년에 전반적으로 낮았으며, 산청은 전년비 $2{\sim}5^{\circ}C$ 높은 상태를 유지하였으며, 강수량은 강진만에 유입되는 담수의 대부분을 차지하는 남강댐 수위에 영향을 미칠 것으로 예상되는 산청지방의 2005년 여름철(7${\sim}$9월) 일별 강수량은 집중호우의 특성을 보이지 않았으며, 굴 폐사가 발생한 9월의 강수량은 남해와 산청지방에서 전년과 평년비 $99.9{\sim}188.0mm$나 적은 양을 보였다. 해양환경측정망(St. 2, 강진만) 자료에 2005년 하계 수온이 2004년에 비해 $2^{\circ}C$, 2003년에 비해 $2.6^{\circ}C$ 높은 값을 보였으며, 양식 굴의 먹이생물과 직접적으로 연관이 있는 Ch1-a 농도는 2005년에는 대단히 낮은 값(2.15ug/L)을 보였으며, SS 농도도 낮은 값(4.6mg/L)을 보였다. 조사당시 수질환경은 양식 굴의 폐사에 직접적인 영향을 미칠만한 요인은 관찰되지 않았으나, 조사정점 1(지족)의 저층에서 2.87mg/L의 낮은 용존산소가 관찰되었으며, 2005년 8월 15일 관찰된 강진만의 남-북방향 수직분포도 저층을 따라서 3mg/L이하의 빈산소 수괴가 관찰되었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.11
• /
• pp.1285-1294
• /
• 2010

This study describes the design and verification of short range UWB(Ultra Wideband) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. We describe the relationship between bandwidth of transmitting signal and range resolution. A vivaldi antenna is designed and it's radiation pattern and reflection are measured. It is easy to make array antenna because of small size and thin shape. Aperture size of receiving array antenna is determined by azimuth resolution of radar image. The relation of interval of receiving antenna array, image resolution and aliasing of target on a radar image is analyzed. A vector network analyzer is used to obtain the reflected signal and corner reflectors as targets are positioned at grass field. Applicability of the proposed radar to UGV is proved by analysis of image resolution and penetrating capability for grass in the experiment.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.21 no.3
• /
• pp.139-144
• /
• 1988

The vertical distribution of eggs and larvae of anchovy. Engraulis japonica were studied based on ichthyoplankton and the temperature distribution in the southwestern part of the Sea of Japan off Korea during the summer of 1985 and 1986. Thermoclines occurred at the surface layer in the coastal area and at the sub-surface layer in the offshore area in the early summer of 1985. However, they occurred at the surface layer throughout the summer of 1986. Anchovy eggs and larvae were abundant in the offshore in 1985 and in the coastal area in 1986. It seems that the spawning ground of anchovy in 1985 shifted to the offshore owing to the sloping of thermoclines. According to the distribution layer of anchovy eggs by developmental stage, the eggs in the early developmental stage were abundant at $0\~30m$ layer about 06:00. But the eggs in the late developmental stage were abundant at $30\~100m$ loom layer about 24 : 00. These results suggest that anchovy spawn at the $0\~30m$ layer at night and eggs tend to sink to the $30\~100m$ layer in the course of development.

• Journal of Korean Society for Geospatial Information Science
• /
• v.4 no.2 s.8
• /
• pp.195-203
• /
• 1996

The 3-D analysis of terrain for route design and selection is being used as important basic data for effective judgement of political draft. This study is to decide efficient alignment of the entry route and design bridge by modeling, analyzing and displaying surface with digital terrain data. In this study we analyze slope, aspect, shaded-relief, line of sight and watershed on the base of DTM such as contour, TIN and grid. And we can not only esti mate end-area volume for road construction by calculating cut and fill and displaying mass-curve but also recognize the scene after execution with simulation of road and terrain. The result of this study reveals that visual effects of the 3-D terrain data are very effective for designer and decisionmaker to select and review alternative route with regard to terrain characteristics.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.24 no.2
• /
• pp.167-173
• /
• 2006

Ionosphere is the largest error source on propagation of GPS signals. Dual frequency (L1,L2) GPS receiver can be effectively able to eliminate the ionosphere error by using linear combination of two frequencies, but the single frequency receiver (L1) have to compute the ionosphere error. In this research, we developed the new ionospheric model with $1^{\circ}$ by $1^{\circ}$ spatial resolution based on the grid from using 9 GPS reference stations which have been operated by KASI (Korea Astronomy and Space Science Institute) and computed TEC (Total Electron Contents) over South Korea by epoch. This paper gives the positioning results of Klobuchar model with that of a newly developed KASI regional ionospheric model and shows the positioning precision of the KASI regional ionospheric model along with TEC variation of ionosphere.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.6 no.4
• /
• pp.257-263
• /
• 2008

We analyzed the statistical properties for the conductive background fractures in the Low and Intermediate Level Waste(LILW) disposal site to conceptualize of its groundwater flow system. The background fractures were classified to fracture sets based on their trends and plunges that were obtained from the borehole logging data, and then the fracture transmissivity distribution was inferred from the fixed interval hydraulic test results. The fracture size distribution of each fracture set was estimated using the fracture density and fracture mapping data. To verify the analyzed results, we compared observed field data to simulated one from the DFN model that was constructed with the analyzed statistical properties of the background fractures, and they showed a good agreement.