• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.16-25
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• 2015

Visual census and hydro-acoustic survey was carried out at Ulju small scale marine ranching area (MRA) to estimate demersal fish aggregations on September and November 2013. In this hydro-acoustic survey, the authors combined an image sonar with a scientific echo sounder to monitor an underwater situation and compare two acoustic data. Consequently, visual census survey was useful to estimate fish species composition for hydro-acoustic survey, because it is easy to identify aggregated fish species and overcome limits on a fishing depth and ability of an conventional fishing gear like a bottom gill-net or a fish trap at marine ranching area. Mean fish density was estimated as $0.757g/m^2$ on September and $0.219g/m^2$ on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV=13.1%) on September and 0.44ton (CV=47.7%) on November, respectively. Hydro-acoustic survey combined with the image sonar was useful to monitor fish aggregations and estimate fish stocks around artificial reefs at shallow coastal MRA. We were able to easily identify the underwater structures like an artificial reef and a fishing rope as well as fish aggregations from image sonar data. Therefore, the method was effective to separate unwanted echo signals in acoustic data of scientific echo sounder.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.363-367
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• 2009

The ship maneuverability is changed by the effects of the bank cushion and the squat in the restricted water area. It is difficult to test the ship maneuverability by the real ship in the restricted water area because of ship's safety. In this study, a numerical model ship was used to simulate the ship's motion and to get information about the bank cushion and the squat in the restricted water area. The less apart from the quay the ship ran, the more ship's heading changed. The greatest change of ship's heading was $22.37^{\circ}$ when a ratio of the length between ship and quay to ship's breadh(=D/B) was 0.2. The squat of the ship was greater in shallower water and at faster speed. The greatest squat was 0.29m when a ratio of water depth to ship's draft(H/d) was 1.25 and ship's speed was 8 knots, the reduced speed was found to be the most important factor in the shallow water area for safety of the ship.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.27-33
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• 1999

We have investigated the ultra-low energy B, P, and As ion implantation using upgraded MDRANGE code to study formation of nanometer junction depths. Even at the ultra-low energies simulated in this paper, it was revealed that ion channeling should be carefully considered. It was estimated that ion channelings have much effect on dopant profiles when B ion implant energies were more than 500 eV, P more than 2 keV and As approximately more than 4 keV. When we compared 2-dimensional dopant profiles of 1 keV B with that of tilted one, 2 keV P with tilt, and 5 keV As with tilt, we could find that most channeling cases occurred not lateral directions but depth directions.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.70-82
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• 1995

A multi-layer simulation program is developed to estimate the ocean current considering sea bottom geometry. The so-called $\sigma$ coordinate system is introduced in vertical direction to describe sea bottom topography more accurately and effectively. Leapfrog scheme combined with Euler backward scheme is used to reduce computation error which may be possibly accumulated in time evolution by Leapfrog scheme alone. In this paper, very simple examples of rectangular basins with various bottom geometries were taken and the effect of sea bottom geometry on vertical structure of the ocean tidal current and its direction were investigated. Through comparisons between the present three dimensional calculation in which bottom topography is directly taken into consideration and the two dimensional calculation in which depth average concept is employed, it was found that magnitude of surface current and its direction could be largely affected by the sea bottom topography, particularly in shallow region with complex bottom shape.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.13-22
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• 2016

An optimized spudcan was designed for the Southwestern Sea, an area mostly comprised of sand and soft clay layers. The spudcan was designed using guidelines by SNAME, ISO, and InSafeJIP, as well as the yield surface for combined loads. The probe test method was applied to define a yield surface used in estimating spudcan stability. Numerical analyses that considered vertical, horizontal, and moment loads in Southwestern Sea resulted in a design of 8 m diameter spudcan. Additionally, the empirical equations suggested by previous studies can estimate a reasonable spudcan bearing capacity at shallow depth. Each yield surface calculated from Mohr Coulomb and Hardening soil model showed different shapes, however the yield surface also grew with increasing spudcan diameter. This yield surface is a useful reference, along with site investigation results and published guidelines, to estimate the stability of a spudcan in the Southwestern Sea.

• The Journal of Engineering Geology
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• v.4 no.1
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• pp.29-42
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• 1994

Discrimination studies between microearthquakes and underground explosions are carried out in the pure-continental path of north-south within the Korean Peninsula. The characteristic waveforms for explosions and microearthquakes are investigated in the light of observation and synthetic seismograms. The characteristic waveform generation is minnly a function of source mechanism and ray-path and former influences more strongly than the latter.A double-couple source mechanism for microeatthquakes and a single-couple(force) mechanism for explosions are presented in this study. It is found for very shallow events to have outstanding of $L_g$ waves in the transverse components that pass through the upper crust with period of 1 - 6 seconds and fundamental modes of Rayleigh waves, $R_g$ in the vertical component with period 8-12 seconds. Furthermore it is pointed out that the first arrival amplitudes of SH waves for explosions are always srnall regardless of azimuth of stations since there is non-existence of nodal lines for the explosion mechanism. Theoretical seismograms for explosions show the first motions of compression with short wavelengths as well as mostly fundamental modes of Rayleight waves, $R_g$ waves and $L_g$ waves, whereas those of micro-earthquakes give either compression or dilatation according to the ack azimuth epicenter to stations and poor or non $R_g$ waves and complicated $L_g$ waves, depending on the focal depth.

• Journal of the Society of Disaster Information
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• v.14 no.2
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• pp.165-173
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• 2018

Purpose: The area such as historic sites where distributed in the hills surrounded by the mountains in the past, if heavy rains occur, soil that distributed in the substructure of a sedimentary layer's permeability decreases therefore, water do not smoothly drainage and increases surface structures' moisture content. Therefore, many phenomena occur such as the muddy ground. This experiment tried to figure out the cause of poor drainage, predicting poor drainage system when rainfall occur. So not only the base of cultural properties distributed in the historic site, but also have big influences on the upper structure. Method: We are going to propose an improvement plan through the various sites exploration and the field permeability test. In addition, analyze interrelationship to figure out the cause of the poor drainage through monitoring under ground water. Conclusion: As the result of the experiment, the cause of the poor drainage system formed on shallow depth of ground level inside of a land. We can see that soil of surface and fill deposit permeability was in poor condition. Therefore, it was in very inappropriate hydrogeological condition when surface water permeate into the underground when rainfall occurs.

• The Journal of Korean Medical History
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• v.24 no.1
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• pp.111-117
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• 2011

"Classified Assemblage of Medical Prescriptions(醫方類聚)" is a valuable material which can explain about historical records of East Asian medicine till 15th century. We can also konw what were regarded as important idea by contemporary doctors of Korean in 'Chosun' dynasty. And, Epilepsy is the one of the olddest diseases with a humankind history for a long time. All the concetps of disease including epilepsy in East Asia has been developed and specilized. So, we can find out some valuable facts from Epilepsy section in "Classified Assemblage of Medical Prescriptions". First, 'Epilepsy' was mixed with 'Mad', 'Spasm' before 7th century but after than, it had been divided into in detail. Since 14th century, we can find out that it was separated with 'Spasm' completely. In conclusion, 'Epilepsy' concept in "Classified Assemblage of Medical Prescriptions" at 15th century is similar with mordern 'Epilepsy' concept. Second, We can find out that 'Epilepsy disease' was divided into 'Five epilepsy' before 7th century, and divided into 'external cause', 'internal cause', 'external & internal cause' in 12th century. And, it also was divided into 'yin' or 'yang' epilepsy. So, 'Epilepsy' concept in " Classified Assemblage of Medical Prescriptions" at 15th century can be divided into 'yin' or 'yang' generally, and also it is similar with 'Acute and slow shock'. Especially, 'yinyang' of epilepsy is related to organs & bouls, depth & shallow, interior & exterior, not cold & heat definitely. From now on, the researches about how it had been understood in East Asia can help to find out modern significance of Korean medicine. and, it would be helpful for comprehensive study about "Classified Assemblage of Medical Prescriptions" from these researches in each section.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.476-486
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• 2014

This study is aimed to understand the vertical distribution of fish in the daytime and nighttime using an acoustic survey in Yondam reservoir of Jeollabuk-do, and an acoustical backscattering strength of dominant species, bass (Micropterus salmoides) and a bluegill (Lepomis macrochirus), which are classified as the ecosystem disturbing species. The results showed that the fish school was distributed in the shallow areas of less than 10 m depth during the period of Aug. and Oct. where it had a strong thermocline, otherwise, it was distributed over 10-times density under stable water temperatures as $13^{\circ}C$ in Nov. There was no vertical patchiness difference between daytime and nighttime unlike the typical marine ecosystem. The dominant species were crucian carp, bluegill, bass. The hydroacoustic method can provide the spatial distribution and effective removal ways of the ecosystem disturbing species in inland fisheries.

• Korean Journal of Environmental Agriculture
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• v.8 no.1
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• pp.37-46
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• 1989

A 2-dimensional pollutant transport phenomenon in shallow reservoirs was analyzed by using a finite element method. The Galerkin's weighted residual method, based on linear interpolation, was used and a triangle was adopted as an element. The two dimensional Stock's equation and the advection-diffusion equation integrated over depth were used as governing equations. Also the Newton-Raphson method was introduced to solve the non-linear terms of the equation. The results calculated by the model are in good agreement with the analytical solution for a simplified channel where a known solution is avaiable. An actual application of the model is attempted for Sapkyo Lake with a consideration of the influx of the Sapkyo Chun, the Muhan Chun and kogkyo Chun. Further refined research is needed to evaluate the water quality in the other reservoirs.