• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.4
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• pp.283-291
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• 2012

The present work reviews some mechanism explaining how thin layer can develop in the near coastal zone. The existence of thin layer was observed by physical research methods later than classical biological approaches. The Richardson number, which is a ratio between the stratification and shear stress is crucial factor determining the occurrence of thin layer. Micro-structure turbulence seems to affect the plankton behavior, in particular the encountering rate. Encountering rate affects significantly feeding, reproduction etc. and this fact was proved by the mechanical simulation methods. Recently the Gyrotaxis was introduced to explain how thin layer occurs in the mixing layer. Such physical approaches to explain ecological problem will be prominent methods for marine ecological research area.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.823-833
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• 1997

To clarify the annual reproductive cycle of the banded catfish, Pseudobagrus fulvidraco (Richardson), the seasonal changes in histological aspect of gonad and liver were examined. The adult fish was raptured from the upper stream of Young-San river, Chunnam in each month from May 1992 to June 1993. Based on the annual changes in GSI (gonadosomatic index), HSI (hepatosomatic index), CF (condition factor) and histological aspects of the gonads, the annual reproductive cycle were classified into 5 periods as follows: 1) Growing phase (from April to early May): The value of GSI increased and the size of oocytes in perinucleolus stage in oocytes increased gradually. Spermatogonia were developed actively from the epithelial tissues of seminiferous tubules. 2) Maturing phase (from Hay to early June): GSI levels increased rapidly in both sex. Oocytes at various developmental stages were observed. Appearance of active spermatogenesis were observed. 3) Mature and spawning phase (from June to August): High values of GSI remained static and oocytes accumulated significant quantitis of yolk globules. 4) Degenerating phase (from September to November): GSI levels decreased and ovaries were filled mostly with oocytes at the perinucleolus stage. Hepatic cells accumulated significant amounts of lipid droplets. 5) Resting period (from December to March) : Low values of GSI were kept and the size of oocytes at the perinucleolus stage did not increase. Spermatogenesis was not observed.

• Korean Journal of Ichthyology
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• v.7 no.2
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• pp.109-113
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• 1995

A ghost flatheads, Hoplichthys gilberti Jordan et Richardson of the family Hoplichthyidae was studied for the first time in Korea. Five specimens were collected from Pusan in March 28, 1995. The Hoplichthys gilberti is similar to H. langsdorfii in morphological characters, but differs in having 1 rows of spinous processes on scute of both side of body, nearly same size between snout length and eye diameter and 13+3 pectoral fin rays. A new Korean name "Oegasiyangtae" is proposed for the H. gilberti.

• Journal of Radiation Protection and Research
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• v.31 no.1
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• pp.9-15
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• 2006

A long-range atmospheric dispersion model named LADAS has been developed to understand the characteristics of the transport and diffusion of radioactive materials released into atmosphere. The developed numerical model for validation was compared with the results of the ETEX which is the long-range field tracer experiment. As a comparative study, the calculated concentration distributions agreed well in the case of the usage of the mixing heights calculated by the Richardson number than the usage of the constant mixing heights in LADAS model. Also, the calculated concentrations agreed with the time series of the measured ones at some sampling points.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.797-806
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• 2008

The geometric properties of the drainage structures are analyzed through depicting the drainage network which is composed of the whole drainage paths in the natural basin defined at the specific scale. The theoretical consideration is performed on the general structures of networks organized by ramification process based on Fractal tree and Horton's law. The drainage network is generated via ArcGIS, ordered by Strahler's ordering scheme and investigated with Strahler's order. As a results of the Richardson's method it is shown that there may exist the distinct behavioral characteristics between overland-flow and channel flow and the natural stream networks would be space-filling Fractals. As a result, it is shown that the values estimated by considering the overland-flow on being applied to the field data give the different results from the empirical method applied until now. As expected, therefore the results obtained from this study are sure to be devoted further researches on the channel networks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.601-606
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• 2014

The IPO(Iterative Physical Optics) method repeatedly applies the well-known PO(Physical Optics) approximation to calculate the scattered field by a large object. Thus, the IPO method can consider the multiple scattering in the object, which is ignored for the PO approximation. This kind of iteration can improve the final accuracy of the induced current on the scatterer, which can result in the enhancement of the accuracy of the RCS(Radar Cross Section) of the scatterer. Since the IPO method can not exactly but approximately solve the required integral equation, however, the convergence of the IPO solution can not be guaranteed. Hence, we apply the famous techniques used in the inversion of a matrix to the IPO method, which include Jacobi, Gauss-Seidel, SOR(Successive Over Relaxation) and Richardson methods. The proposed IPO methods can efficiently calculate the RCS of a large scatterer, and are numerically verified.

• Water for future
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• v.28 no.5
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• pp.117-127
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• 1995

The application and analysis for the scale considering GIUH model proposed by the authors in this issue have been performed for the leemokjung sub-basin in the Pyungchang basin one of IHP representative basin in Korea. Scales of topographic maps for model application and fractal analysis are 1:25,000, 1:50,000 and 1:100,000. The ratio between successive scales is therefore constant. Link lengths were measured using a curvimeter with the resolution of 1 mm. Richardson's method was employed to have fractal dimension of streams. Apparent alternations of parameters were found in accordance with variations of map scale. And this tendency could mislead physical meanings of parameters because model parameters had to preserve their own value in spite of map scale change. It was found that uses of fractal transform and Melton's law could help to control the scale problem effectively. This methodlogy also could emphasize the relationship between network and basin to the model. To verify the applicability of GIUH proposed in this research, the model was compared with the exponential GIUH model. It is proven that proposed 2-parameter gamma GIUH model can better simulate the corresponding runoff from any given flood events than exponential GIUH model. The result showed that 2-parameter gamma GIUH model and fractal theory could be used for deriving scale considered IUH of the basin.

• Journal of Korea Water Resources Association
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• v.50 no.9
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• pp.637-646
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• 2017

This study presents a numerical model for simulating dense interflows. The governing equations are provided and the finite difference method is used with the $k-{\varepsilon}$ turbulence model. The model is used to simulate a dense interflow established in a deep ambient water, resulting velocity and excess density profiles. It is observed that velocity decreases in the longitudinal direction due to water entrainment in the vicinity of the outlet and rarely changes for increased Richardson number. Similarity collapses of velocity and excess density are obtained, but those of turbulent kinetic energy and dissipation rate are not. A shape factor for the dense interflow is obtained from the simulated profiles. The value of this shape factor can be used in the layer-averaged modeling of dense interflows. In addition, a buoyancy-related parameter ($c_{3{\varepsilon}}$) for the $k-{\varepsilon}$ model and the volume expansion coefficient (${\beta}_0$) are obtained from the simulated results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.5
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• pp.257-264
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• 2016

In this study, experiments for measurements of entrainment rate of fluid mud were carried out using annular flume domestically for the first time. Six entrainment tests using kaolinite sediments were conducted with different initial concentrations of fluid mud. It is shown that sediment settling counteracts the otherwise buoyancy dependent entrainment of fluid mud, and that the settling effect leads to a measurably decreased entrainment rate at higher Richardson numbers in comparison with entrainment of salt water, due to additional dissipation of turbulent kinetic energy in the interfacial layer. Through the comparison with previous other studies, the overall performance of the annular flume, the experimental procedure and the test results in simulating the entrainment of fluid mud are shown to be good enough to verify.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.317-325
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• 2012

In this paper, we consider the encoding scheme of Low Density Parity Check codes. In particular, using the Jacket Pattern and circulant permutation matrices, we propose the simple encoding scheme of Richardson's lower triangular matrix. These encoding scheme can be extended to a flexible code rate. Based on the simple matrix process, also we can design low complex and simple encoders for the flexible code rates.