• Title/Summary/Keyword: 해양시스템

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Predictability of Northern Hemisphere Blocking in the KMA GDAPS during 2016~2017 (기상청 전지구예측시스템 자료에서의 2016~2017년 북반구 블로킹 예측성 분석)

  • Roh, Joon-Woo;Cho, Hyeong-Oh;Son, Seok-Woo;Baek, Hee-Jeong;Boo, Kyung-On;Lee, Jung-Kyung
    • Atmosphere
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    • v.28 no.4
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    • pp.403-414
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    • 2018
  • Predictability of Northern Hemisphere blocking in the Korea Meteorological Administration (KMA) Global Data Assimilation and Prediction System (GDAPS) is evaluated for the period of July 2016 to May 2017. Using the operational model output, blocking is defined by a meridional gradient reversal of 500-hPa geopotential height as Tibaldi-Molteni Index. Its predictability is quantified by computing the critical success index and bias score against ERA-Interim data. It turns out that Northwest Pacific blockings, among others, are reasonably well predicted with a forecast lead time of 2~3 days. The highest prediction skill is found in spring with 3.5 lead days, whereas the lowest prediction skill is observed in autumn with 2.25 lead days. Although further analyses are needed with longer dataset, this result suggests that Northern Hemisphere blocking is not well predicted in the operational weather prediction model beyond a short-term weather prediction limit. In the spring, summer, and autumn periods, there was a tendency to overestimate the Western North Pacific blocking.

Image Compression by Linear and Nonlinear Transformation of Computed Tomography (전산화단층촬영의 선형과 비선형변환에 의한 영상압축)

  • Park, Jae-Hong;Yoo, Ju-Yeon
    • Journal of the Korean Society of Radiology
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    • v.13 no.4
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    • pp.509-516
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    • 2019
  • In the linear transformation method, the original image is divided into a plurality of range blocks, and a partial transform system for finding an optimal domain block existing in the image for each range block is used to adjust the performance of the compression ratio and the picture quality, The nonlinear transformation method uses only the rotation transformation among eight shuffle transforms. Since the search is performed only in the limited domain block, the coding time is faster than the linear transformation method of searching the domain block for any block in the image, Since the optimal domain block for the range block can not be selected in the image, the performance may be lower than other methods. Therefore, the nonlinear transformation method improves the performance by increasing the approximation degree of the brightness coefficient conversion instead of selecting the optimal domain block, The smaller the size of the block, the higher the PSNR value, The higher the compression ratio is increased groups were quadtree block divided to encode the image at best.

Compensation of the Distorted WDM Channels in Ultra-long Transmission Link of 80 km × 56 Spans (80 km × 56 spans의 초장거리 전송 링크에서 왜곡된 WDM 채널의 보상)

  • Lee, Seong-Real
    • Journal of Advanced Navigation Technology
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    • v.23 no.3
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    • pp.251-257
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    • 2019
  • The configuration of ultra-long optical transmission link with dispersion management and optical phase conjugation is proposed. The whole transmission link consist of 80 km (single mode fiber span) ${\times}$ 56 fiber spans. The artificial distribution of single mode fibers' lengths and residual dispersions in fiber spans, which are gradually increased/decreased as the span number is increased, is adopted to compensate for the distorted wavelength division multiplexed channels. Since the compensation effect through the artificial distribution in the previous researches is expected to decrease as the number of fiber spans are increased, three-time repetition of the artificial distribution patterns at intervals of 9 fiber spans applied into the link with dispersion management and optical phase conjugation is proposed. From the simulation results, it is confirmed that the compensation in the link configured by the special distribution pattern among 4 proposed patterns is slightly improved than the link configured by the conventional method, which is designed by the repeat-less distribution pattern.

Simulation of Membrane Sloshing Tank by Using MPS (입자법을 이용한 멤브레인 타입 슬로싱 시뮬레이션)

  • Kim, Kyung Sung
    • Journal of the Korea Convergence Society
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    • v.10 no.10
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    • pp.117-122
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    • 2019
  • In the field of fluid dynamics, the sloshing effects are most common and significant problem. It is usually appeared in the tank filled with fluid which is on the main structure, thus, sloshing effects and its impact load may affect to entire system. For the sloshing effects analysis, impact loads due to tank motion is generally investigated theocratically, experimentally and numerically. The difficulty of sloshing phenomenon is non-linearity induced by large deformation at the free-surface. In this regard, it is well known issue that the repeatability on the sloshing problems is very low. In this study, moving particle semi-implicit method was employed to simulate sloshing problem and then the results were compared with corresponding experiments captured by high accuracy high speed camera. The results from numerical simulation was compared to experimental results.

Error Calibration of Initial Value of Weight Measuring Sensors with Different Feature of Forklift (특성이 다른 지게차 적재 중량 센서의 초기 값 오차 보정)

  • Han, Chi-moon;Yim, Choon-Sik;Lee, Seong-Real
    • Journal of Advanced Navigation Technology
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    • v.23 no.2
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    • pp.214-220
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    • 2019
  • The calibration method of the initial value error obtained in the weight measurement through anchor bolt type strain gauge sensor is proposed. The strain gauge sensor is developed for preventing the overturning of forklift, which is the most frequent type of safety-accident in industry. It was confirmed that the initial value error is caused from the physical and mechanical error of anchor bolt, and the environmental problem. Since the elimination of these causes falls outside the realm of this research, we find out the calibrated values based on all the causes, and we adjust the initial values of analog-to-digital convertor (ADC) module consisted of strain gauge sensor block using the calibrated values. We use the linear interpolation method for our calibration. We confirm that four sensor modules have the different under 5% between the real weight and the measured value in the experiment applied with the calibration of initial values. The low correlation between the real weights and ADC values is also improved through the proposed calibration.

The Improvement of Disaster Safety Network using ICT Devices (ICT 기기를 활용한 재난안전통신망 강화 방안)

  • Hong, Sung-Hwa
    • Journal of Advanced Navigation Technology
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    • v.23 no.2
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    • pp.194-199
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    • 2019
  • Natural disasters destroy decades of human effort and investments, thereby placing new demands on society for reconstruction and rehabilitation. In most case, the natural phenomena triggering the disasters are beyond human control. In order to solve the problems that the information resources can not be shared among disaster management sectors and their work is hard to be coordinated in city, an idea of application of ubiquitous sense network and ICT technology to model the architecture of the disaster prevention system based on the analysis of characteristics of disasters. The proposed algorithm simulated that it is possible to locate the terminal by linking the direction angle and the estimated position that can be confirmed at the time of stopping, even if the movement direction of the terminal does not move in a certain direction with only a smaller number of mobile base stations. We also confirmed that the proposed algorithms analyzed through simulation are more efficient than existing algorithms.

Separation Device Development and Flight Test for Marine Recovery of Scientific Balloon (과학기구 기낭의 해상 회수를 위한 분리장치 개발 및 비행시험)

  • Shim, Gyujin;Kang, Jungpyo;Kim, Hweeho;Yee, Kwanjung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.1
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    • pp.49-58
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    • 2019
  • The Scientific balloon is a flight system that could recover an entire platform at the end of the mission. The recovery takes place mainly in low-density populated areas, taking into account for the possible damage to the human life and public safety. In Republic of Korea, on the other hand, marine recovery should be considered due to the dense mountainous terrain and restrictions of the peninsula. In this operating environment, the envelope must be recovered because of severe marine pollution that may occur after the splashdown. Therefore, in this study, the separation device that consists of a location tracker and the waterproof system were developed. The device includes data transmission/reception, separation, and waterproof systems which are manufactured considering the environmental condition of the Korea. The performance of the device and the trajectory of the envelope were verified by conducting a separation test of a 20km platform at a target altitude and the recovery of the zero-pressure balloon.

A Study on the Time-periodic Characteristics of Changes in Typhoon Activities and Precipitation over the Korean Peninsula (시기별 한반도 영향 태풍의 활동 특성 및 강우 변화 분석)

  • Kang, Hyun woong;Park, Jin Hyeog;Jang, Su hyung;Son, Chan Young;Kim, Jung Min
    • Proceedings of the Korea Water Resources Association Conference
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    • 2018.05a
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    • pp.321-321
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    • 2018
  • 태풍은 단시간동안 인류활동에 막대한 영향력을 미치는 저기압 시스템 중 하나로 인류에 중요한 수자원을 공급하여 물 부족 현상을 해소하거나, 열대해역에 축적된 과잉 에너지를 수송하여 에너지 균형을 유지하고, 해양 및 대기 정화로 인한 생태계를 활성화하는 긍정적인 면과 육지에 상륙함에 따라 심한 강풍과 폭우를 동반하여 인적 경제적 피해를 주는 부정적인 면을 동시에 지니고 있는 중요한 대기현상이다(Lee, 2006; Wang, 2010; Xu, 2013; Delphine et al., 2013). 2002년 루사, 2003년 매미, 2012년 볼라벤, 2013년 하이옌 그리고 2016년 차바와 같이 세력이 강한 태풍으로 인해 동아시아 지역은 매년 막대한 인명 및 재산피해가 야기되고 있는 실정임에 따라, 태풍으로 인한 재해를 최소화하고 태풍이 가지는 긍정적인 혜택을 적극 활용하기 위해서는 태풍의 활동 및 호우 예측 및 경향성에 대해 보다 정량적인 연구가 필요하다(Oh et al., 2011; Kim and Jain, 2011; Li and Zhou, 2012; Son et al., 2013). 따라서, 본 연구에서는 Son et al.(2014)이 제시한 태풍의 경로 및 규모를 고려한 태풍 추출기법을 적용하여 한반도에 영향을 미친 태풍 및 태풍강우를 추출하였으며, 이를 과거 1977-1994년(Period 1)과 1995-2012년(Period 2) 두 기간으로 분류하였다. 또한, 태풍의 최대풍속을 기준으로 3단계(35-64kt, 65-94kt, 95kt이상)로 구분하여 과거 시기별 태풍 활동(최대풍속, 최소중심기압, 발생빈도, 발생지점, 전향점, 경로) 특성을 분석하고, 과거 시기별 태풍강우(시간 최대 태풍강우량, 총 태풍 강우량)의 변화 분석을 수행하였다. 본 연구의 결과는 향후, 태풍과 관련하여 수질개선 및 수자원확보 등과 같은 태풍 활용방안과 태풍 피해저감을 위한 치수대책 수립 등에 대한 기초자료로 활용가능하며, 기후변화로 인해 야기될 수 있는 태풍의 활동 및 강우 특성 변화를 파악하는 데 이용가능 할 것으로 판단된다.

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Convergence of Nonlocal Integral Operator in Peridynamics (비국부 적분 연산기로 표현되는 페리다이나믹 방정식의 수렴성)

  • Jo, Gwanghyun;Ha, Youn Doh
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.34 no.3
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    • pp.151-157
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    • 2021
  • This paper is devoted to a convergence study of the nonlocal integral operator in peridynamics. The implicit formulation can be an efficient approach to obtain the static/quasi-static solution of crack propagation problems. Implicit methods require constly large-matrix operations. Therefore, convergence is important for improving computational efficiency. When the radial influence function is utilized in the nonlocal integral equation, the fractional Laplacian integral equation is obtained. It has been mathematically proved that the condition number of the system matrix is affected by the order of the radial influence function and nonlocal horizon size. We formulate the static crack problem with peridynamics and utilize Newton-Raphson methods with a preconditioned conjugate gradient scheme to solve this nonlinear stationary system. The convergence behavior and the computational time for solving the implicit algebraic system have been studied with respect to the order of the radial influence function and nonlocal horizon size.

A Study on The Scale Effect of Landslide Model Tests (산사태 모형실험에서의 Scale Effect에 관한 연구)

  • Jeong, Jisu;Ji, Younghwan;Kim, Yootae;Lee, Seungho
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.8
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    • pp.5-12
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    • 2011
  • This study was performed to analyze the degree of rainfalls, the duration time of rainfalls, the inclination of slopes and other damage causes depending on the ground condition, when the landslide occurs by the rainfall. Based on that, a big and a small model soil box were compared to examine the features of landslides, which is ultimately for forecasting landslides. An artificial rainfall device was installed in the model box, and the large model box has a real-size slope in it. Also, various measures were fulfilled such as collapse forms, a pore pressure, an earth pressure and moisture contents in order to analyze the effect of the model box size on the landslide mechanism and to test the usability of a small model box as a material for landslide experiments.