Improvement of overtopping risk evaluations using probabilistic concepts for existing dams     

Hyun-Han Kwon  Young-Il Moon 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(4):223-237

Hydrologic risk analysis for dam safety relies on a series of probabilistic analyses of rainfall-runoff and flow routing models, and their associated inputs. This is a complex problem in that the probability distributions of multiple independent and derived random variables need to be estimated in order to evaluate the probability of dam overtopping. Typically, parametric density estimation methods have been applied in this setting, and the exhaustive Monte Carlo simulation (MCS) of models is used to derive some of the distributions. Often, the distributions used to model some of the random variables are inappropriate relative to the expected behaviour of these variables, and as a result, simulations of the system can lead to unrealistic values of extreme rainfall or water surface levels and hence of the probability of dam overtopping. In this paper, three major innovations are introduced to address this situation. The first is the use of nonparametric probability density estimation methods for selected variables, the second is the use of Latin Hypercube sampling to improve the efficiency of MCS driven by the multiple random variables, and the third is the use of Bootstrap resampling to determine initial water surface level. An application to the Soyang Dam in South Korea illustrates how the traditional parametric approach can lead to potentially unrealistic estimates of dam safety, while the proposed approach provides rather reasonable estimates and an assessment of their sensitivity to key parameters.  相似文献   

Correlation of geologic logs with spectral methods     

Byung-Doo Kwon  Albert J. Rudman 《Mathematical Geology》1979,11(4):373-390

Spectral studies of geologic logs demonstrate that automatic well—log correlation can be processed more efficiently in the frequency domain. Cross correlation of the power spectra of well logs identifies the direction and degree of thickening of stratigraphic sequences between two wells. Given the stretch, the displacement between logs is computed by correlation processes without relying on iterative procedures. Beginning with digitized log data of unequal lengths, power spectra are computed. The stretch factor between the two logs is observed as a difference in frequency scaling. A transform to logarithmic frequencies converts the spectra to a form that reduces the scaling effect of the frequencies to a simple displacement between the plots. A Lagrange interpolation procedure permits cross correlation of the two spectra with a variable window size. The peak value of the resultant correlation function identifies the displacement between the spectra and this, in turn, permits calculation of the stretch factor.  相似文献   

Accurate absolute GPS positioning through satellite clock error estimation   总被引：11，自引：0，他引：11  

S.-C. Han  J. H. Kwon  C. Jekeli 《Journal of Geodesy》2001,75(1):33-43

 An algorithm for very accurate absolute positioning through Global Positioning System (GPS) satellite clock estimation has been developed. Using International GPS Service (IGS) precise orbits and measurements, GPS clock errors were estimated at 30-s intervals. Compared to values determined by the Jet Propulsion Laboratory, the agreement was at the level of about 0.1 ns (3 cm). The clock error estimates were then applied to an absolute positioning algorithm in both static and kinematic modes. For the static case, an IGS station was selected and the coordinates were estimated every 30 s. The estimated absolute position coordinates and the known values had a mean difference of up to 18 cm with standard deviation less than 2 cm. For the kinematic case, data obtained every second from a GPS buoy were tested and the result from the absolute positioning was compared to a differential GPS (DGPS) solution. The mean differences between the coordinates estimated by the two methods are less than 40 cm and the standard deviations are less than 25 cm. It was verified that this poorer standard deviation on 1-s position results is due to the clock error interpolation from 30-s estimates with Selective Availability (SA). After SA was turned off, higher-rate clock error estimates (such as 1 s) could be obtained by a simple interpolation with negligible corruption. Therefore, the proposed absolute positioning technique can be used to within a few centimeters' precision at any rate by estimating 30-s satellite clock errors and interpolating them. Received: 16 May 2000 / Accepted: 23 October 2000  相似文献   

Genesis and Age Constraints on Gold Deposits of the Daerae Mine, Sangju Area, Central-Northern Sobaegsan Massif, Korea     

Seong–Taek YUN  Seung–Jun YOUM  Chil–Sup SO  Seon–Gyu CHOI  De–Quan ZHANG  Yong–Kwon KOH 《Resource Geology》2001,51(3):205-215

Abstract: Gold mineralization of the Daerae mine represents the first recognized example of the Jurassic gold mineralization in the Sangju area, Korea. It occurs as a single stage of quartz veins that fill fault fractures in Precambrian gneiss of the central‐northern Sobaegsan Massif. The mineralogical characteristics of quartz veins, such as the simple mineralogy and relatively gold‐rich (65–72 atomic % Au) nature of electrum, as well as the CO₂–rich and low salinity nature of fluid inclusions, are consistent with the ‘mesothermal‐type’ gold deposits previously recognized in the Youngdong area (about 50 km southwest of the Sangju area). Ore fluids were evolved mainly through CO₂ immiscibility at temperatures between about 250 and 325 C. Vein sulfides characteristically have negative sulfur isotopic values (–1.9 to +0.2 %), which have been very rarely reported in South Korea, and possibly indicate the derivation of sulfur from an ilmenite‐series granite melt. The calculated O and H isotopic compositions of hydrothermal fluids at Daerae (δ¹⁸O_water = +5.2 to +5.9 %; δD_water = –59 to –67 %) are very similar to those from the Youngdong area, and indicate the important role of magmatic water in gold mineralization. The ⁴⁰Ar–³⁹Ar age dating of a pure alteration sericite sample yields a high‐temperature plateau age of 188.3 0.1 Ma, indicating an early Jurassic age for the gold mineralization at Daerae. The lower temperature Ar‐Ar plateau defines an age of 158.4 2.0 Ma (middle Jurassic), interpreted as reset by a subsequent thermal effect after quartz vein formation. The younger plateau age is the same as the previously reported K‐Ar ages (145–171 Ma) for the other ‘mesothermal–type’ gold deposits in the Youngdong and Jungwon areas, Korea, which are too young in view of the new Jurassic Ar‐Ar plateau age (around 188 Ma).  相似文献   

Review　of　the　Researches　on　Changma　and　Future　Observational　Study(KORMEX)   总被引：7，自引：2，他引：7  

Jai-Ho Oh  Won-Tae Kwon  Sang-Boom Ryoo 《大气科学进展》1997,14(2):207-222

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A Scalable High-Performance I/O System for a Numerical Weather Forecast Model on the Cubed-Sphere Grid     

Junghan Kim  Young Cheol Kwon  Tae-Hun Kim 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):403-412

The design and implementation of a high-performance Input/Output (I/O) library for the Korean Integrated Model (KIM, KIM-IO) is described in this paper. The KIM is a next-generation global operational model for the Korea Meteorological Administration (KMA). The horizontal discretization of KIM consists of the spectral-element method on the cubed-sphere grid. The KIM-IO is developed to be a consistent and efficient approach for input and output of essential data in this particular grid structure in a multiprocessing environment. The KIM-IO provides three main features, comprising the sequential I/O, parallel I/O, and I/O decomposition methods, and adopts user-friendly interfaces similar to the Network Common Data Form (NetCDF). The efficiency of the KIM-IO is verified using experiments to analyze the performance of its three features. The scalability is also verified by implementing the KIMIO in the KIM at a resolution of approximately 12 km using the 4th supercomputer of KMA. The experimental results show that both regular parallel I/O and sequential I/O undergo performance degradation with an increasing number of processes. However, the I/O decomposition method in the KIM-IO overcomes this degradation, leading to improvement in scalability. The results also indicate that with using the new I/O decomposition method, the KIM attains good parallel scalability up to Ο (100,000) cores.  相似文献   

The long-term variability of Changma in the East Asian summer monsoon system: A review and revisit     

June-Yi Lee  MinHo Kwon  Kyung-Sook Yun  Seung-Ki Min  In-Hong Park  Yoo-Geun Ham  Emilia Kyung Jin  Joo-Hong Kim  Kyong-Hwan Seo  WonMoo Kim  So-Young Yim  Jin-Ho Yoon 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(2):257-272

Changma, which is a vital part of East Asian summer monsoon (EASM) system, plays a critical role in modulating water and energy cycles in Korea. Better understanding of its long-term variability and change is therefore a matter of scientific and societal importance. It has been indicated that characteristics of Changma have undergone significant interdecadal changes in association with the mid-1970s global-scale climate shift and the mid-1990s EASM shift. This paper reviews and revisits the characteristics on the long-term changes of Changma focusing on the underlying mechanisms for the changes. The four important features are manifested mainly during the last few decades: 1) mean and extreme rainfalls during Changma period from June to September have been increased with the amplification of diurnal cycle of rainfall, 2) the dry spell between the first and second rainy periods has become shorter, 3) the rainfall amount as well as the number of rainy days during August have significantly increased, probably due to the increase in typhoon landfalls, and 4) the relationship between the Changma rainfall and Western Pacific Subtropical High on interannual time scale has been enhanced. The typhoon contribution to the increase in heavy rainfall is attributable to enhanced interaction between typhoons and midlatitude baroclinic environment. It is noted that the change in the relationship between Changma and the tropical sea surface temperature (SST) over the Indian, Pacific, and Atlantic Oceans is a key factor in the long-term changes of Changma and EASM. Possible sources for the recent mid-1990s change include 1) the tropical dipole-like SST pattern between the central Pacific and Indo-Pacific region (the global warming hiatus pattern), 2) the recent intensification of tropical SST gradients among the Indian Ocean, the western Pacific, and the eastern Pacific, and 3) the tropical Atlantic SST warming.  相似文献   

Methodology for Quantitative Estimation of One-Dimensional Consolidation Settlement Based on Hybrid Simulation Method     

Youngcheul Kwon 《Marine Georesources & Geotechnology》2016,34(3):199-209

A hybrid simulation system, HyCoS, was developed involving the control, measurement, and analysis process in order to realize the basic algorithm of hybrid consolidation simulation. The system was fully automated by the development of the program HyCoS. Furthermore, a computer program, CONPERM, was also developed to obtain soil constitutive relationships in compression and hydraulic conductivity from inputting the data from the HyCoS simulation. Two laboratory simulations were conducted in order to verify the system involving the basic algorithm of the system and two major components, the software and hardware operation. The objectives of this process are divided into two major aspects. The first was to confirm whether the experimental equipment, such as the consolidometer and control and data acquisition device, maintained a stable operation status during the whole period of the consolidation test. In addition, verification was also carried out to determine whether the target control can actually be maintained on the specimen. The second objective was to confirm the reliability of the data obtained from the system HyCoS.  相似文献   

Phylogenetic relationship between symbionts of tubeworm <Emphasis Type="Italic">Lamellibrachia satsuma</Emphasis> and the sediment microbial community in Kagoshima Bay     

Ajit Kumar Patra  Hyun Hee Cho  Yong Min Kwon  Kae Kyoung Kwon  Takako Sato  Chiaki Kato  Sung Gyun Kang  Sang-Jin Kim 《Ocean Science Journal》2016,51(3):317-332

Vestimentiferan tubeworms acquire their symbionts through horizontal transmission from the surrounding environment. In the present study, we constructed a 16S rRNA gene clone library to investigate the phylogenetic relationship between diverse microbes in the sediment and symbiotic bacteria in the trophosome of the tubeworm, Lamellibrachia satsuma, from Kagoshima Bay, Japan. Two symbiotic bacterial phylotypes belonging to the classes γ- and ε-Proteobacteria were found from this tubeworm trophosome. They were very closely related to the symbionts of several other marine invertebrates. The most predominant bacteria in the sediment were ε-Proteobacteria. A broad diversity of bacteria belonged to non-proteobacterial phyla such as Planctomycetes, Acidobacteria, and Chloroflexi was observed. The presence of sulfur oxidizers (i.e., ε-Proteobacteria and γ-Proteobacteria) and sulfur reducers (i.e., δ-Proteobacteria) may play a significant role in the sulfur cycle in these habitats and provide multiple sources of nutrition to the cold-seep communities. Closely related clones of ε-Proteobacteria symbiont in the species level and of γ-Proteobacteria symbiont in the genus level were found in the surrounding sediment. The similarity of symbiont clones of L. satsuma with other symbionts and free-living bacteria suggests the possibility of opportunistic symbiosis in ε-Proteobacteria and the co-evolution of γ-Proteobacteria having occurred after symbiosis with the tubeworms.  相似文献   

On the freezing precipitation in korea and the basic schemes for its potential prediction     

Sang-Hoon Kwon  Hi-Ryong Byun  Chang-Kyun Park  Hui-Nae Kwon 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(1):35-50

This study aims to improve the forecasting skill for freezing precipitation. A total of 102 freezing precipitation cases were collected in South and North Korea from 2001 onwards. Temperature fields on the ground and in the atmosphere, vertical temperature profiles, geopotential fields, thickness fields and their spatiotemporal variations, and their combinations using the predominant precipitation-type nomograms (P-type nomograms) were classified and investigated to determine whether or not these data could be used as predictors. Results show that 1) the combination of the thicknesses of 1000-850 hPa and 850-700 hPa is recommended for the P-type nomograms for Korea, which is different from that used in the United States in threshold values; 2) 35 out of 72 synoptic situations are possible conditions for freezing precipitation; and 3) 3 groups out of those 35 situations, i.e., the 1000 hPa warmfront group, the mid-level southerly category of 850 hPa, and the mid-layer warm type in the vertical temperature profile, show the greatest frequency. Freezing precipitation occurs only in a small part of a possible area. Therefore, despite the increasing observations in the year-on-year trend, only a few of the cases have been detected. The possibility of observation errors is also one of the biggest problems. Therefore, the need for new equipment, such as a freezing rain detector (FRAD), to detect the phenomenon automatically is required and proposed. A denser observing system of FRADs and an ultra-fine gridded numerical model are suggested as a solution for the prediction of freezing precipitation.  相似文献