4-D inversion of DC resistivity monitoring data acquired over a dynamically changing earth model   总被引：2，自引：0，他引：2  

Jung-Ho Kim  Myeong-Jong Yi  Sam-Gyu Park  Jae Gon Kim 《Journal of Applied Geophysics》2009,68(4):522-532

Geophysical monitoring is used principally to interpret the locations and amounts of ground condition changes. To achieve these objectives, differences are computed and examined using time-lapse images calculated under the time-invariant static assumption, that any material property changes during the data measurement can be practically ignored. These monitored data, however, can be contaminated with noise and frequently generate false anomalies of ground condition changes. Furthermore, the assumption of the static model can be invalid if the material property changes significantly during data acquisition. To alleviate these problems, we developed a new least-squares inversion algorithm that allows for the subsurface properties to continuously change in time. We define the subsurface structure and the entire monitoring data in the space–time domain, allowing us to obtain a four-dimensional space–time model using just one inversion process. We introduce the regularizations not only in the space domain but also in time, resulting in reduced inversion artifacts and improved stability of the inverse problem. We demonstrated the performance of the proposed algorithm through numerical experiments that assumed several scenarios of ground condition changes and data acquisition sequences. Finally, the applicability to field data was proven by applying the developed algorithm to the monitoring data of crosshole resistivity tomography jointly performed with a dye tracer flooding experiment. This experiment had a small enough scale that we could not ignore the change of material properties during the data measurement.  相似文献   

A 2000-year environmental history of the Upo Wetland on the Korean Peninsula     

Heungtae Kim  Jae Geun Kim 《Journal of Paleolimnology》2010,44(1):189-202

The Upo Wetland was designated an internationally important wetland by the Ramsar Convention and is the largest inland wetland on the Korean Peninsula. This study was conducted to reveal the environmental history of the wetland and its surroundings, and to evaluate the influence of human activities on the ecosystem. We used information from historical documents and sediment records to investigate the wetland. A 40-cm sediment core was collected and dated using ²¹⁰Pb and ¹⁴C. Physical and chemical variables in the core were measured and pollen was analyzed. The environmental history of the Upo Wetland over the last 2,000 years was divided into three phases. Seawater may have entered the wetland around 2,000 years ago. Upo was probably a riverine wetland with a floodplain that experienced relatively rapid water flow and erosion until about AD 870. Thereafter, Upo became a palustrine wetland with lacustrine characteristics during an unstable environmental phase until some time between 870 and 1880 AD, when water flow decreased and both the water retention time and the area of flooding within the wetland increased. Construction of artificial levees within the wetland during the twentieth century constituted an anthropogenic impact superimposed on natural changes, and Upo became a shallow lake. Inputs of nutrients and other pollutants from the catchment continue to threaten the Upo ecosystem despite the establishment of policies intended to protect this important ecosystem.  相似文献   

Simulations of mesospheric and thermospheric IR radiance measured in the CIRRIS-1A shuttle experiment   总被引：1，自引：0，他引：1  

S. Adler-Golden  D. R. Smith  J. Vail  A. Berk  R. Nadile  L. Jeong 《Journal of Atmospheric and Solar》1999,61(18):389

Comprehensive simulations of upper atmospheric limb radiance from 2.5 to 25 μm, carried out using a moderate-resolution non-LTE code and a series of model atmospheres, are compared with data from the 1991 CIRRIS-1A shuttle experiment. Good agreement, typically within a factor of two, is found at most wavelengths over a five-order-of-magnitude range in spectral radiance. The comparisons yield information on the temperature profile, the production and concentrations of odd-oxygen and odd-hydrogen species in the mesopause region and NO in the thermosphere, and the kinetics of CO₂ vibrational states.  相似文献   

Fluid–structure interaction analysis of 3-D rectangular tanks by a variationally coupled BEM–FEM and comparison with test results     

Hyun Moo Koh  Jae Kwan Kim  Jang-Ho Park 《地震工程与结构动力学》1998,27(2):109-124

A variationally coupled BEM–FEM is developed which can be used to analyse dynamic response, including free-surface sloshing motion, of 3-D rectangular liquid storage tanks subjected to horizontal ground excitation. The tank structure is modelled by the finite element method and the fluid region by the indirect boundary element method. By minimizing a single Lagrange function defined for the entire system, the governing equation with symmetric coefficient matrices is obtained. To verify the newly developed method, the analysis results are compared with the shaking-table test data of a 3-D rectangular tank model and with the solutions by the direct BEM–FEM. Analytical studies are conducted on the dynamic behaviour of 3-D rectangular tanks using the method developed. In particular, the characteristics of the sloshing response, the effect of the rigidity of adjacent walls on the dynamic response of the tanks and the orthogonal effects are investigated. © 1998 John Wiley & Sons, Ltd.  相似文献   

An analysis on the mean sea level change of the seas adjacent to Korea     

Byung Ho Choi  Sang Jun Roh  Jae Hak Lee  Fang Guohong 《海洋学报(英文版)》1999,18(3):337-353

  相似文献   

Chromaticity of gravitational microlensing events     

Cheongho Han  Seong-Hong Park  Jang-Hae Jeong 《Monthly notices of the Royal Astronomical Society》2000,316(1):97-102

In this paper, we investigate the colour changes of gravitational microlensing events caused by the two different mechanisms of differential amplification for a limb-darkened extended source and blending. From this investigation, we find that the colour changes of limb-darkened extended source events (colour curves) have dramatically different characteristics depending on whether the lens transits the source star or not. We show that for a source transit event, the lens proper motion can be determined by simply measuring the turning time of the colour curve instead of fitting the overall colour or light curves. We also find that even for a very small fraction of blended light, the colour changes induced by blending are equivalent to those induced by limb darkening, causing serious distortion in the observed colour curve. Therefore, to obtain useful information about the lens and source star from the colour curve of an event, it will be essential to correct for blending. We discuss various methods of blending correction .  相似文献   

Directional‐oriented wavefield imaging: a new wave‐based subsurface illumination imaging condition for reverse time migration          下载免费PDF全文

Young Seo Kim  Constantine Tsingas  Woodon Jeong 《Geophysical Prospecting》2018,66(6):1097-1110

The key objective of an imaging algorithm is to produce accurate and high‐resolution images of the subsurface geology. However, significant wavefield distortions occur due to wave propagation through complex structures and irregular acquisition geometries causing uneven wavefield illumination at the target. Therefore, conventional imaging conditions are unable to correctly compensate for variable illumination effects. We propose a generalised wave‐based imaging condition, which incorporates a weighting function based on energy illumination at each subsurface reflection and azimuth angles. Our proposed imaging kernel, named as the directional‐oriented wavefield imaging, compensates for illumination effects produced by possible surface obstructions during acquisition, sparse geometries employed in the field, and complex velocity models. An integral part of the directional‐oriented wavefield imaging condition is a methodology for applying down‐going/up‐going wavefield decomposition to both source and receiver extrapolated wavefields. This type of wavefield decomposition eliminates low‐frequency artefacts and scattering noise caused by the two‐way wave equation and can facilitate the robust estimation for energy fluxes of wavefields required for the seismic illumination analysis. Then, based on the estimation of the respective wavefield propagation vectors and associated directions, we evaluate the illumination energy for each subsurface location as a function of image depth point and subsurface azimuth and reflection angles. Thus, the final directional‐oriented wavefield imaging kernel is a cross‐correlation of the decomposed source and receiver wavefields weighted by the illuminated energy estimated at each depth location. The application of the directional‐oriented wavefield imaging condition can be employed during the generation of both depth‐stacked images and azimuth–reflection angle‐domain common image gathers. Numerical examples using synthetic and real data demonstrate that the new imaging condition can properly image complex wave paths and produce high‐fidelity depth sections.  相似文献   

Spatial disaggregation of ASCAT soil moisture under all sky condition using support vector machine     

Seongkyun?Kim  Jaehwan?Jeong  Muhammad?Zohaib  Minha?ChoiEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(12):3455-3473

With recent advances in downscaling methodologies, soil moisture (SM) estimation using microwave remote sensing has become feasible for local application. However, disaggregation of SM under all sky conditions remains challenging. This study suggests a new downscaling approach under all sky conditions based on support vector regression (SVR) using microwave and optical/infrared data and geolocation information. Optically derived estimates of land surface temperature and normalized difference vegetation index from MODerate Resolution Imaging Spectroradiometer land and atmosphere products were utilized to obtain a continuous spatio-temporal input datasets to disaggregate SM observation from Advanced SCATterometer in South Korea during 2015 growing season. SVR model was compared to synergistic downscaling approach (SDA), which is based on physical relationship between SM and hydrometeorological factors. Evaluation against in situ observations showed that the SVR model under all sky conditions (R: 0.57 to 0.81, ubRMSE: 0.0292 m³ m^?3 to 0.0398 m³ m^?3) outperformed coarse ASCAT SM (R: 0.55 to 0.77, ubRMSE: 0.0300 m³ m^?3 to 0.0408 m³ m^?3) and SDA model (mean R: 0.56 to 0.78, ubRMSE: 0.0324 m³ m^?3 to 0.0436 m³ m^?3) in terms of statistical results as well as sensitivity with precipitation. This study suggests that the spatial downscaling technique based on remote sensing has the potential to derive high resolution SM regardless of weather conditions without relying on data from other sources. It offers an insight for analyzing hydrological, climate, and agricultural conditions at regional to local scale.  相似文献   

Numerical Study on Behavior of Groundwater Flow in Single Rough Fractures Under Mechanical Effect          下载免费PDF全文

Woochang Jeong 《Ground water》2017,55(1):38-50

This paper numerically investigates the characteristics of groundwater flow in spatially correlated variable aperture fractures under the mechanical effect. Spatially correlated aperture distributions are generated using the geostatistical method (i.e., turning bands algorithm in this study). To represent a nonlinear relationship between the effective normal stress and the fracture aperture, a simple mechanical formula is combined with a local flow model. Numerical results indicate that the groundwater flow is significantly affected by the geometry of aperture distribution, varying with the applied effective normal stress as well as the spatial correlation length of aperture distribution. Moreover, using the flow results simulated in this study, two empirical formulae are proposed: (1) the first one (modified Louis formula) is to represent the relationship between the effective normal stress and the effective permeability of fracture and (2) the second one is to represent the relationship between relative roughness and effective permeability.  相似文献   

Impact of the dam water discharge on the circulation system in the Kangjin Bay,South Sea,Korea     

Young Jae Ro  Kwang Young Jung 《Ocean Science Journal》2010,45(1):7-25

This study is based on a series of numerical modeling experiments to understand the impact of the Namgang Dam water discharge into the Kangjin Bay (KB). Numerical model performances were tested in terms of various skill analyses, with skill scores for elevation and tidal current over 85 %. The models successfully reproduced the tidal circulation and the response of fresh water input and subsequent dilution of salinity field. The behavior of the fresh water plume in the KB was investigated and analyzed. The different pattern of densitydriven current field was described at tidal phases. The modified tidal ellipse characteristics are estimated as a result of interaction between tidal current and density current.  相似文献