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Search Results: 1 - 10 of 314585 matches for " J. Kim "
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Developing an Integrated Complementary Relationship for Estimating Evapotranspiration  [PDF]
Homin Kim, Jagath J. Kaluarachchi
Natural Resources (NR) , 2018, DOI: 10.4236/nr.2018.94007
Abstract:
The complementary relationship for estimating evapotranspiration (ET) is a simple approach requiring only commonly available meteorological data; however, most complementary relationship models decrease in predictive power with increasing aridity. In this study, a previously developed Granger and Gray (GG) model by using Budyko framework is further improved to estimate ET under a variety of climatic conditions. This updated GG model, GG-NDVI, includes Normalized Difference Vegetation Index (NDVI), precipitation, and potential evapotranspiration based on the Budyko framework. The Budyko framework is consistent with the complementary relationship and performs well under dry conditions. We validated the GG-NDVI model under operational conditions with the commonly used remote sensing-based Operational Simplified Surface Energy Balance (SSEBop) model at 60 Eddy Covariance AmeriFlux sites located in the USA. Results showed that the Root Mean Square Error (RMSE) for GG-NDVI ranged between 15 and 20 mm/month, which is lower than for SSEBop every year. Although the magnitude of agreement seems to vary from site to site and from season to season, the occurrences of RMSE less than 20 mm/month with the proposed model are more frequent than with SSEBop in both dry and wet sites. Another finding is that the assumption of symmetric complementary relationship is a deficiency in GG-NDVI that may introduce an inherent limitation under certain conditions. We proposed a nonlinear correction function that was incorporated into GG-NDVI to overcome this limitation. As a result, the proposed model produced much lower RMSE values, along with lower RMSE across more sites, as compared to SSEBop.
Organic carbon efflux from a deciduous forest catchment in Korea
S. J. Kim, J. Kim,K. Kim
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: Soil infiltration and surface discharge of precipitation are critical processes that affect the efflux of Dissolved Organic Carbon (DOC) and Particulate Organic Carbon (POC) in forested catchments. Concentrations of DOC and POC can be very high in the soil surface in most forest ecosystems and their efflux may not be negligible particularly under the monsoon climate. In East Asia, however, there are little data available to evaluate the role of such processes in forest carbon budget. In this paper, we address two basic questions: (1) how does stream discharge respond to storm events in a forest catchment? and (2) how much DOC and POC are exported from the catchment particularly during the summer monsoon period? To answer these questions, we collected hydrological data (e.g., precipitation, soil moisture, runoff discharge, groundwater level) and conducted hydrochemical analyses (including DOC, POC, and six tracers) in a deciduous forest catchment in Gwangneung National Arboretum in west-central Korea. Based on the end-member mixing analysis of the six storm events during the summer monsoon in 2005, the surface discharge was estimated as 30 to 80% of the total runoff discharge. The stream discharge responded to precipitation within 12 h during these storm events. The annual efflux of DOC and POC from the catchment was estimated as 0.04 and 0.05 t C ha 1 yr 1, respectively. Approximately 70% of the annual organic carbon efflux occurred during the summer monsoon period. Overall, the annual efflux of organic carbon was estimated to be about 10% of the Net Ecosystem carbon Exchange (NEE) obtained by eddy covariance measurement at the same site. Considering the current trends of increasing intensity and amount of summer rainfall and the large interannual variability in NEE, ignoring the organic carbon efflux from forest catchments would result in an inaccurate estimation of the carbon sink strength of forest ecosystems in the monsoon East Asia.
Organic carbon sequestration and discharge from a deciduous forest catchment in Korea
S. J. Kim,J. Kim,K. Kim
Biogeosciences Discussions , 2009,
Abstract: Soil infiltration and surface discharge of precipitation are critical processes that affect the sequestration and discharge of dissolved organic carbon (DOC) and particulate organic carbon (POC) in forested catchments. Both DOC and POC are highly concentrated in the soil surface in most forest ecosystems and their discharge may not be negligible particularly under the monsoon climate. In East Asia, however, there are little data available to evaluate the role of such processes in forest carbon budget. In this paper, we address two basic questions: 1) how does stream discharge respond to storm events in a forest catchment? and 2) how much DOC and POC are discharged from the catchment particularly during the summer monsoon period? To answer these questions, we collected hydrological data (e.g., precipitation, soil moisture, runoff discharge, groundwater level) and conducted hydrochemical analyses (including DOC, POC, and six tracers) for a deciduous forest catchment in Gwangneung National Arboretum in west-central Korea. Based on the end-member mixing analysis of the six storm events during the summer monsoon in 2005, the surface discharge was estimated as 30 to 80% of the total runoff discharge. The stream discharge responded to precipitation within 12 h during these storm events. The annual discharge of DOC and POC from the catchment was estimated as 0.04 and 0.05 t C ha 1 yr 1, respectively. Approximately 70% of the annual organic carbon efflux occurred during the summer monsoon period. Overall, the annual discharge of organic carbon was estimated to be 4 to 14% of the net ecosystem carbon exchange (NEE) obtained by eddy covariance technique at the same site. Considering the current trends of increasing intensity and amount of summer rainfall and the large interannual variability in NEE, ignoring the organic carbon discharge from forest ecosystems would result in an overestimation (underestimation) of the strength of forests as a carbon sink (source) in the monsoon East Asia.
Adaptive Parallel Computation for Blind Source Separation with Systolic Architecture  [PDF]
H. JEONG, Y. KIM, H. J. JANG
Intelligent Information Management (IIM) , 2010, DOI: 10.4236/iim.2010.21006
Abstract: The purpose of Blind Source Separation (BSS) is to obtain separated sources from convolutive mixture inputs. Among the various available BSS methods, Independent Component Analysis (ICA) is one of the representative methods. Its key idea is to repetitively update and calculate the measures. However, dealing with the measures obtained from multi-array sensors causes obstacles for real-time use. In order to solve this problem, it is necessary to convert the software implementation of BSS algorithm into the hardware architecture. Through the use of hardware architecture, the BSS algorithm can efficiently work within a relatively short time. In this study, we investigate a practical method using a parallel algorithm and architecture for hardware use in a blind source separation. We design a feedback network for real-time speech signal processing. The network is composed of forward and updates algorithms. The architecture of the network is systolic and therefore it is suitable for parallel processing. We only have to add and connect modules for scaling. This paper covers the process from the systolic design of BSS to the hardware implementation using Xilinx FPGAs. The simulation results of our proposed implementation are also represented in the experimental section. In that section, our architecture returns satisfying results with robust qualities.
The Effect of Ethanol on the Transport of a Neutral Amino Acid in the Perfused Whole Human Placenta  [PDF]
Tai J. Kim, Philip A. Rice
Journal of Biomedical Science and Engineering (JBiSE) , 2019, DOI: 10.4236/jbise.2019.122010
Abstract: The effect of ethanol on the transport of amino acids across the human placenta was studied in the dual perfusion apparatus using a non-metabolizable α-amino isobutyric acid (AIB). Results were obtained for thirty intact whole human placentas in the absence (control group) and presence (ethanol group) of ethanol (500 - 1000 mg/dL). Experimental determinations of AIB transport at AIB concentrations of 5 - 100 mg/l, measured radioactively using (114 C-) AIB, were compared with a dual-active transport model. The diffusion coefficients of AIB were found to be (3.7 × 109 cm2/s) in the absence of ethanol and (2.3 × 109 cm2/s) in the presence of ethanol with no statistical difference (P = 0.25). The ratio of the fetal to maternal perfusate concentrations in the absence of ethanol (1.44) was statistically significant (P = 0.016) from the ratio in the presence of ethanol (1.20), which may indicate that active transport in the human placenta is inhibited by the presence of ethanol. The placental uptake from the maternal circulation was 2.6 (control) and 2.5 (ethanol) times greater than the uptake from the total circulation. The relative contribution of the diffusive transport to the net placental uptake of AIB from both the maternal and fetal circulations was less than that of active transport regardless of the presence of ethanol: control (38%) and ethanol (35%). It appears that the placental tissue plays the role of a mediator to maintain a fetal concentration higher than the maternal one by either enhancing the transfer from the maternal to the placental tissue or impairing the transfer in the opposite direction.
Numerical study of surface energy partitioning on the Tibetan plateau: comparative analysis of two biosphere models
J. Hong ,J. Kim
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: The Tibetan Plateau is a critical region in the research of biosphere-atmosphere interactions on both regional and global scales due to its relation to Asian summer monsoon and El Ni o. The unique environment on the Plateau provides valuable information for the evaluation of the models' surface energy partitioning associated with the summer monsoon. In this study, we investigated the surface energy partitioning on this important area through comparative analysis of two biosphere models constrained by the in-situ observation data. Indeed, the characteristics of the Plateau provide a unique opportunity to clarify the structural deficiencies of biosphere models as well as new insight into the surface energy partitioning on the Plateau. Our analysis showed that the observed inconsistency between the two biosphere models was mainly related to: 1) the parameterization for soil evaporation; 2) the way to deal with roughness lengths of momentum and scalars; and 3) the parameterization of subgrid velocity scale for aerodynamic conductance. Our study demonstrates that one should carefully interpret the modeling results on the Plateau especially during the pre-monsoon period.
Numerical study of surface energy partitioning on the Tibetan Plateau: comparative analysis of two biosphere models
J. Hong,J. Kim
Biogeosciences Discussions , 2009,
Abstract: The Tibetan Plateau is a critical region in the research of biosphere-atmosphere interactions on both regional and global scales due to its relation to Asian summer monsoon and El Ni o. The unique environment on the Plateau provides valuable information for the evaluation of the models' surface energy partitioning associated with the summer monsoon. In this study, we investigated the surface energy partitioning on this important area through comparative analysis of two biosphere models constrained by the in-situ observation data. Indeed, the characteristics of the Plateau provide a unique opportunity to clarify the structural deficiencies of biosphere models as well as new insight into the surface energy partitioning on the Plateau. Our analysis showed that the observed inconsistency between the two biosphere models was mainly related to: 1) the parameterization for soil evaporation; 2) the way to deal with roughness lengths of momentum and scalars; and 3) the parameterization of subgrid velocity scale for aerodynamic conductance. Our study demonstrates that one should carefully interpret the modeling results on the Plateau especially during the pre-monsoon period.
Evaluation of Accuracy and Precision of IRMS by Using Standard Materials and Applications  [PDF]
J. Y. Hwang, B. K. Kim, M. S. Kim, J. W. Choi, T. S. Kim, W. S. Lee
Journal of Agricultural Chemistry and Environment (JACEN) , 2016, DOI: 10.4236/jacen.2016.54022
Abstract: The isotope ratio mass spectrometer (IRMS) is an instrument that measures both of the elemental contents and isotope ratios of hydrogen, oxygen, carbon, nitrogen and sulfur in environmental samples at the same time. In this study, we want to try to get two main goals; first, to make up for setting the analytical conditions such as accuracy and precision, second, to apply for comparing of the carbon and nitrogen isotope ratio of sediments in the abandoned mine located in middle province of Korea. For the first goal, a recently introduced IRMS was used to analyze CRM (certified reference materials), which helped to make up the analytical conditions of carbon and nitrogen isotope ratios. So, the accuracy and precision of isotope ratios and elemental contents were also assessed simultaneously, and also the results were very satisfactory. The analytical results of carbon reference materials (EMA-P2) showed an accuracy of -2.801 × 10‰ ± 0.01‰ (2σ) and a precision of 0.009‰ in the mass range from 0.008 μg - 0.162 μg. For nitrogen reference materials (EMA-P2), an accuracy of -1.632‰ ± 0.72‰ (2σ) was obtained in the mass range from 0.082 - 0.162 mg. These values of accuracy and precision are higher than those reported by other studies. For the second goal, carbon and nitrogen isotopes in river sediment near abandoned mines were analyzed based on the established analytical conditions. The result suggested that carbon isotope ratios ranged from -22.5‰ - -7.5‰ and nitrogen isotope ratios from -1.9‰ - 7.9‰. By comparing the isotope ratios and sampling sites of sediment, we know that the nitrogen isotope values in samples of entrance area of mine are greater than those of the farm house area, which is indicating the effects of organic materials. So, we could guess that the newly accumulated organic materials were much more in the farm house area than mine entrance area. And a result of this study, the accuracy and precision tests of IRMS using certified reference materials were very satisfactory and optimum analytical conditions were established well. And also, it was found that the applications of isotopic analysis for environmental samples by using the IRMS could be very useful for the studies on tracing pollution sources.
Analysis of food components of freeze-dried Alaska Pollack (Hwangtae)
J-S Kim, KS Kim, M-J Kim
African Journal of Biotechnology , 2010,
Abstract: Physiochemical properties of freeze-dried Alaska Pollack (Hwangtae) were investigated. The moisture, crude ash and crude fat content of Hwangtae were 12.53, 5.91 and 0.94%, respectively. Contents of saccharides were found to be 3.69 mg/100 g in dried weight of glucose and 5.71 mg/100 g in dried weight of sucrose. Minerals in 100 g dry weight of Hwangtae include phosphorus (806.5 mg), calcium (612.7 mg), potassium (442.2 mg), sodium (283.5 mg), magnesium (89.9 mg), zinc (1.9 mg), iron (0.8 mg), manganese (0.3 mg) and aluminum (0.2 mg), respectively. Glutamic acid and aspartic acid were the major amino acids, containing 925.4 and 644.7 mol/g in dried weight, respectively. Fatty acids in Hwangtae were composed of monounsaturated fatty acids, polyunsaturated fatty acids and saturated fatty acids, containing 16.3, 41.2 and 42.5%, respectively. Our results suggested that this Hwangtae, a freeze-dried fish, can be used as a good nutrition source for human health.
On the -Euler Numbers and Polynomials with Weight
T. Kim,J. Choi
Abstract and Applied Analysis , 2012, DOI: 10.1155/2012/795304
Abstract: The purpose of this paper is to investigate some properties of -Euler numbers and polynomials with weight 0. From those -Euler numbers with weight 0, we derive some identities on the -Euler numbers and polynomials with weight 0.
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