• 제목/요약/키워드: Grace

검색결과 334건 처리시간 0.03초

Spatio temporal analysis of land subsidence due to declining groundwater levels in arid region of Pakistan using Sentinel-1 SAR imegery

  • Ahmad, Waqas;Kim, Dongkyun;Kim, Soohyun
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2017년도 학술발표회
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    • pp.192-192
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    • 2017
  • In this paper we showed the application of European Space Agency's C-band Sentinel-1 Synthetic Aperture Radar (SAR) imagery to identify land subsidence in a heavily groundwater pumping area. We used the repeat pass satellite interferometry method in combination with persistent scattering (PS) interferometric technique to generate and analyze twenty-eight interferograms for the period October 2014 to November 2016. The interferometry results show that land subsidence is more pronounced in the urban areas. Excessive groundwater pumping in the study area is believed to be the main reason for land subsidence. The results are compared with the subsidence rate measured by GPS as reported in other studies and with the mean change in total water storage field of GRACE solutions provided by the Jet Propulsion Laboratory (JPL), the German Research Centre for Geosciences (GFZ) and the Center for Space Research (CSR). The comparison shows persistently decreasing trends during the period of study. A strong reliance of the trend of land subsidence on the temporal decline in total water storage proposes that much of the land subsidence can be attributed to heavy pumping of the groundwater.

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Indefinite sustainability of passive residual heat removal system of small modular reactor using dry air cooling tower

  • Na, Min Wook;Shin, Doyoung;Park, Jae Hyung;Lee, Jeong Ik;Kim, Sung Joong
    • Nuclear Engineering and Technology
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    • 제52권5호
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    • pp.964-974
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    • 2020
  • The small modular reactors (SMRs) of the integrated pressurized water reactor (IPWR) type have been widely developed owing to their enhanced safety features. The SMR-IPWR adopts passive residual heat removal system (PRHRS) to extract residual heat from the core. Because the PRHRS removes the residual heat using the latent heat of the water stored in the emergency cooldown tank, the PRHRS gradually loses its cooling capacity after the stored water is depleted. A quick restoration of the power supply is expected infeasible under station blackout accident condition, so an advanced PRHRS is needed to ensure an extended grace period. In this study, an advanced design is proposed to indirectly incorporate a dry air cooling tower to the PRHRS through an intermediate loop called indefinite PRHRS. The feasibility of the indefinite PRHRS was assessed through a long-term transient simulation using the MARS-KS code. The indefinite PRHRS is expected to remove the residual heat without depleting the stored water. The effect of the environmental temperature on the indefinite PRHRS was confirmed by parametric analysis using comparative simulations with different environmental temperatures.

Analysis of Inter-satellite Ranging Precision for Gravity Recovery in a Satellite Gravimetry Mission

  • Kim, Pureum;Park, Sang-Young;Kang, Dae-Eun;Lee, Youngro
    • Journal of Astronomy and Space Sciences
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    • 제35권4호
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    • pp.243-252
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    • 2018
  • In a satellite gravimetry mission similar to GRACE, the precision of inter-satellite ranging is one of the key factors affecting the quality of gravity field recovery. In this paper, the impact of ranging precision on the accuracy of recovered geopotential coefficients is analyzed. Simulated precise orbit determination (POD) data and inter-satellite range data of formation-flying satellites containing white noise were generated, and geopotential coefficients were recovered from these simulated data sets using the crude acceleration approach. The accuracy of the recovered coefficients was quantitatively compared between data sets encompassing different ranging precisions. From this analysis, a rough prediction of the accuracy of geopotential coefficients could be obtained from the hypothetical mission. For a given POD precision, a ranging measurement precision that matches the POD precision was determined. Since the purpose of adopting inter-satellite ranging in a gravimetry mission is to overcome the imprecision of determining orbits, ranging measurements should be more precise than POD. For that reason, it can be concluded that this critical ranging precision matching the POD precision can serve as the minimum precision requirement for an on-board ranging device. Although the result obtained herein is about a very particular case, this methodology can also be applied in cases where different parameters are used.

토양수분 기반 FDII를 활용한 돌발가뭄의 시공간적 정량화 (Quantitative analysis of spatiotemporal characteristics of flash drought using Flash Drought Intensity Index based on soil moisture)

  • 이희진;남원호
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2023년도 학술발표회
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    • pp.46-46
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    • 2023
  • 돌발가뭄 (Flash drought)은 일반적인 가뭄과 달리 기후변화에 따른 기상 이상으로 인해 단기간 급속하게 발생하는 가뭄이다. 짧은 기간에 식생 스트레스가 증가하며, 작물생산량의 감소로 인해 농업 생태계에 피해를 야기하며, 과도한 증발 수요 및 급격한 토양수분의 감소는 수문학적 영향을 미치게 된다. 본 연구에서는 최근 개발된 Flash Drought Intenisty Index (FDII, 2021)를 활용하여 2014년부터 2018년까지 5년간 발생한 돌발가뭄에 분석하였다. FDII는 가뭄 심화속도, 평균 심각도의 두 가지 요소를 곱하여 나타내며, 일반적으로 가뭄 및 비가뭄에 대한 정도를 나타내는 아노말리 (Anomaly) 대신 백분위수 (Percentile)를 활용한다. 국내 돌발가뭄 분석을 위하여 Gravity Recovery and Climate Experiment (GRACE) 위성영상 기반 근역층 토양수분 자료를 활용하였다. 2014년부터 2018년까지 전국 8도 (경기, 강원, 충남, 충북, 전남, 전북, 경남, 경북)를 대상으로 돌발가뭄 사상에 대하여 토양수분 백분위수의 월별 공간분포 및 FDII를 산정하여 국내 돌발가뭄의 강도를 정량화하였다. 지역 및 시기별로 다르게 발생하는 돌발가뭄을 대상으로 FDII를 활용하여 돌발가뭄의 초기 발생, 가뭄 전이 현상 등 시공간적 특성을 분석하고자 한다. 향후 대상 지역의 세분화 및 장기적인 관점에서의 FDII 적용으로 신뢰성 높은 국내 돌발가뭄 모니터링 및 분석 기술로 활용할 수 있을 것으로 기대된다.

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Impact of assimilating the terrestrial water storage on the water and carbon cycles in CLM5-BGC

  • Chi, Heawon;Seo, Hocheol;Kim, Yeonjoo
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2021년도 학술발표회
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    • pp.204-204
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    • 2021
  • Terrestrial water storage (TWS) includes all components of water (e.g., surface water, groundwater, snow and ice) over the land. So accurately predicting and estimating TWS is important in water resource management. Although many land surface models are used to predict the TWS, model output has errors and biases in comparison to the observation data due to the model deficiencies in the model structure, atmospheric forcing datasets, and parameters. In this study, Gravity Recovery And Climate Experiment (GRACE) satelite TWS data is assimilated in the Community Land Model version 5 with a biogeochemistry module (CLM5.0-BGC) over East Asia from 2003 to 2010 by employing the Ensemble Adjustment Kalman Filter (EAKF). Results showed that TWS over East Asia continued to decrease during the study period, and the ability to simulate the surface water storage, which is the component of the CLM derived TWS, was greatly improved. We further investigated the impact of assimilated TWS on the vegetated and carbon related variables, including the leaf area index and primary products of ecosystem. We also evaluated the simulated total ecosystem carbon and calculated its correlation with TWS. This study shows that how the better simulated TWS plays a role in capturing not only water but also carbon fluxes and states.

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Buyer's EOQ problem with inventory-level-dependent demand rate when the supplier allows day-terms credit

  • Song Chang-Yong;Shinn Seong-Whan
    • 대한안전경영과학회:학술대회논문집
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    • 대한안전경영과학회 2001년도 춘계학술대회
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    • pp.199-203
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    • 2001
  • In today's business transactions, it is more and more common to see that the buyers are allowed some grace period before they settle the account with the supplier. In this regard, we analyze the problem of determining the buyer's EOQ when the supplier allows day-terms credit. For the analysis, it is assumed that the buyer's demand rate is a function of the on -hand inventory level and the relevant mathematical model is developed.

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편대비행 위성간 거리변화 및 외력과의 관계식 연구

  • 김정래
    • 한국우주과학회:학술대회논문집(한국우주과학회보)
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    • 한국우주과학회 2004년도 한국우주과학회보 제13권1호
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    • pp.59-59
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    • 2004
  • 최근에 발사되어 임무를 수행중인 GRACE(Gravity Recovery And Climate Experiment) 위성사업은 편대비행하는 두 개의 저궤도 위성 간 거리를 측정하여 지구중력장을 관측하는 연구인데, 여기에 사용되는 위성간 거리측정기 성능분석을 위한 기본연구단계로, 해석식을 이용하여 외력과 위성간 거리변화와의 관계를 연구하였다. 원궤도에 근접한 궤도를 비행하는 위성의 운동은 Hill's 방정식을 사용하여 나타낼 수 있는데, 이로부터 위성에 가해지는 외력에 의한 위성의 운동 관계식을 얻을 수 있다. (중략)

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소프트웨어 TPM 을 사용한 신뢰형 채팅룸 설계 및 구현 (Design and Implementation of Trusted Chatting Room Using Software TPM)

  • 치녜레 그레이스 케네디;조동섭
    • 한국멀티미디어학회:학술대회논문집
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    • 한국멀티미디어학회 2012년도 춘계학술발표대회논문집
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    • pp.259-261
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    • 2012
  • Chatting room has become widely using technology and it is vulnerable to the internet attackers. We proposed a chatting system using a Purebasic programming language to communicate across networks system. Chatting room text is a form of instant messaging between two or group of people. A Communication experiment was designed and implemented to confirm the validity of the developed chatting system on a trusted platform.

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Geoid of Western Mongolia from airborne gravity data 2004

  • Forsberg, Rene;Olesen, A.;Dalkhaa, Munkhtsetseg;Begzsuren, Amarzaya
    • 한국지형공간정보학회:학술대회논문집
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    • 한국지형공간정보학회 2005년도 아시아 태평양 국제 GSIS 학술발표회
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    • pp.93-99
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    • 2005
  • This paper summarizes a preliminary geoid computation for western Mongolia, utilizing the airborne data collected fall 2004, as part of the NGA-DNSC-ALAGaC-MonMap cooperative airborne gravity project. A gravimetric geoid has been computed using the airborne gravity data, SRTM terrain models and GRACE/EGM global fields. The gravimetric geoid has subsequently been fitted to GPS-leveling data across Western Mongolia, as well as for a special Ulaanbaatar city geoid model.

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보도육교의 구조적인 컨셉에 대한 세계적인 추세 (A world-wide trends in structural concepts of footbridge)

  • 박선우
    • 한국공간정보시스템학회:학술대회논문집
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    • 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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    • pp.197-205
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    • 2004
  • A vocabulary for a understanding bridge has a different scope. There are the urban setting, landscape, lightness, from minimum to maximum, continuity, material, erection, motion and dynamic. Aesthetics criteria of footbridge design are movement and grace, space and experiment, symbolism, iconic, sculpture, innovation, spectacle, lighting, gemetry and wonder. New structural concepts of pedestrian bridges are presented on examples of recently built structures. The main characteristics of described structures are appropriateness, humanity, structural efficiency and aesthetics.

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