• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.333-339
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• 2012

The main objective of the present study is to investigate the roles of the micro-dimpled surface on the drag reduction. To investigate the effectiveness of the micro-dimpled surface, the flat plates are prepared. The micro-size dimples are directly carved on the metal surface by ultrasonic nano-crystal surface modification (UNSM) method. Momentum of the main flow is increased by the dimple patterns within the turbulent boundary layer (TBL), however, there is no significant change in the turbulence intensity in the TBL. The influence of dimple patterns is examined through the flow field survey near the flat plate trailing edge in terms of the profile drag. The wake flow velocities in the flat plate are measured by PIV technique. The maximum drag reduction rate is 4.6% at the Reynolds number of $10^6{\sim}10^7$. The dimples tend to increase the drag reduction rate consistently even at high Reynolds number range.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.161-171
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• 1997

The exact information on geological structures and characteristics of the subsurface must be acquired to secure quality and safety of constructions. GPR technique, one of the most updated geophysical methods, is known for its applicability to shallow-depth underground surveys. The purpose of this study is to examine the usefulness of GPR method in constructions for detailed subsurface investigations, especially detecting the boundary between basement rock and its overburden. To find appropriate depths of the geological boundaries, it is necessary to obtain velocity of electromagnetic wave propagating into the ground. Wave velocity 0.096 m/ns estimated from velocity analysis using CMP gathers is used for depth conversion from time section. The depths of geological boundaries from GPR profiles are very well correlated with boring data. In addition, GPR survey has found some undulations of the geological boundaries due to weathering, which cannot be provided by conventional coring approaches.

• Korean Journal of Remote Sensing
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• v.33 no.6_2
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• pp.1159-1169
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• 2017

Since 1970's, various satellite remote sensing technology has been developed and accumulation of observational data has been carried out, and coastal environment monitoring research is being conducted through analysis of relationship between satellite remote sensing data and coastal sedimentary environment. However, generation of coastal thematic maps by various national agencies are not included in the production of coastal themes using satellite imagery. In this study, we want to deduct the current problems through survey of marine spatial information provided by the government. The purpose of this study is to investigation the direction of the development of large scale coastal thematic maps by analyzing coastal boundary map, coastal topographic map and coastal sedimentary facies map.

• The Journal of Society for e-Business Studies
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• v.16 no.3
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• pp.47-66
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• 2011

This study empirically investigates the antecedents and outcomes of choice satisfaction in the context of choosing and using the broadband Internet network services. Hypotheses are tested with regression models analyzing a survey data of 481 consumers of the broadband Internet network services in Korea. Our results show that choice satisfaction is affected by choice contexts while service satisfaction is not. Choice satisfaction is as important as service satisfaction for formation of switching intentions whereas it is less important for formation of recommendation intentions. Also, consumers characteristics are reported for those whose service satisfaction and choice satisfaction are not consistent. Choice satisfaction is a distinctive concept different from service satisfaction. Marketers can make consumers more satisfied not only managing delivery of services but also by managing their choice contexts. That will increase the loyalty of their consumers. This study finds unique determinants of choice satisfaction. Further studies are needed to clarify boundary conditions regarding the effects of choice contexts on choice satisfaction.

• Korean Institute of Interior Design Journal
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• v.27 no.1
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• pp.68-79
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• 2018

The main purpose of this paper is to introduce 'Inframince' in modern and contemporary architecture. The Inframince(English: infra-thin) is a concept coined by Marcel Duchamp. The conceptual definition of the term "Inframince" by Marcel Duchamp replied that the notion is impossible to define, "one can only give examples of it:". It describes fine indirect perceptions of physical phenomena. Inframince is conductor of two dimensions into three, the essential dynamic in the practice of making space. Inframince is the interval between an inhabitant and their environment that both connects and separates. This study deals with the difficult situation how Contemporary Architecture represents itself over the 20th century modernity and asks the question how it presents its ornamentality. In order to analyse contradictory situation between self-referentiality and ornamentality in Modern/Contemporary Architecture we need to survey the historical process of changing position of ornaments and its meaning in time. The article also analyze the selected works of contemporary architects like Herzog & de Meuron, Jean Nouvel, to show that the trend reversal continues now more than ever. The Architectural surface must be a different kind of media that can communicate in different way with compared to conventional ornament. If we understand Duchmp's Inframince to be the provocation of the unuseful things, and if we interpret Contemporary fact that all specific Architectural Surfaces have been dissolved in timelines, it shows us post-trend of the Surfaces via conspicuous consumption or desire.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.5
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• pp.3-13
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• 2005

The present study examined the 3 dimensional space distribution characteristics of sea water intrusion using data available from previous observations. For this study, we used 3D FEMWATER, which is a 3 dimensional finite element model. The target area was around Daechang-ri, Gimje-si, Jeollabuk-do. The area is relatively easy to formulate a conceptual model and has observation wells in operation for surveying sea water intrusion. Considering the uncertainty of numerical simulation, we analyzed sensitivity to hydraulic conductivity, which has a relatively higher effect. According to the result of the analysis, the variation of TDS concentration had an error range of $-1,336{\~}+107 mg/{\iota}$. Taking note that the survey data from observation wells were collected when the boundary between fresh water and sea water in the aquifer was in equilibrium, we set the range of time for numerical simulation and estimated the spatial distribution of TDS concentration as the range of sea water intrusion. According to the result of estimation, the spatial distribution of TDS concentration calculated when 1,440 days were simulated was taken as the range of sea water intrusion. Using the result of calculation, we can draw not only vertical views for a certain section but also horizontal views of different depth. These views will be greatly helpful in understanding the spatial distribution of the range of sea water intrusion. In addition, the result of this study can be used rationally in proposing an optimal quantity of water pumping through investigating the moving route of sea water intrusion over time in order to prevent excessive water pumping and to maintain an optimal number of water pumping wells per interval.

• Ocean and Polar Research
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• v.25 no.1
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• pp.89-106
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• 2003

Analyses of tidal observations and a numerical model of the $M_2$ and $M_4$ tides in the Uldolmok waterway located at the southwestern tip of the Korean Peninsula are described. This waterway is well known fer its strong tidal flows of up to more than 10 knots at the narrowest part of the channel. Harmonic analysis of the observed water level at five tidal stations reveals dramatic changes in the amplitude and phase of the shallow water constituents at the station near the narrowest part, while survey results show a decreasing trend in local mean sea levels toward the narrow section. It was also observed that the amplitudes of semi-diurnal constituents, $M_2$ and $S_2$ are diminishing toward the narrowest part of the waterway. Two-dimensional numerical modeling shows that the $M_2$ energy flux is dominated by the component coming from the eastern boundary. The $M_2$ energy is inward from both open boundaries and is transported toward the narrow region of the channel, where it is frictionally dissipated or transferred to other constituents due to a strong non-linear advection effect. It is also shown that the $M_4$ generation is strong around the narrow region, and the abrupt decrease in the M4 amplitude in the region is due to a cancellation of the locally generated M4 with the component propagated from open boundaries. The superposition of both propagated and generated M4 contributions also explains the discontinuity of the M4 phase lag in the region. The tide-induced residual sea level change and the regeneration effect of the $M_2$ tide through interaction with $M_4$ are also examined.

• Journal of Fisheries and Marine Sciences Education
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• v.17 no.1
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• pp.58-66
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• 2005

Floating debris was observed using a training ship, KAYA, of Pukyong National University with cruising speed of about 10-12 knot during July 12~25, 2003. The area sampled was the East Sea enclosed by 3 nations, namely, Korea, Japan and Russia, and was divided into 68 unit segments on survey routes [Fig. 1]. Debris fabrication materials were categorized with 6 items, e.g., man-made or natural wood items, paper and cardboard, nylon rope, styrofoam, vinyl and plastic, floating metal and glass containers. All identified items within $100{\pm}10 m$ wide band were recorded but ignored if beyond this boundary. The results of this study are as follows: 1. The average numbers of debris per unit area, $1km^2$, were found as 16.3 pieces (items) in the sea. 2. The highest densities of numbers, $32.3pieces/km^2$, were discovered in vicinity of the Oki strait of Japan, area of 'NEK' in Fig. 1. 3. Especially, styrofoam item only was composed to 63.6% of all in the sea of 'SD', located in the southern part of Dokdo Island, Korea. The item seems to be derive from the Southern Sea of Korea. 4. Therefore, comparing the distribution of debris numbers (the results of above 2 and 3) with flow patterns of Kuroshio currents, it was shown that their relation was good agree each other. Further more surveys are being conducted and a much wider coverage can be achieved with other countries, then it can be obtained that the East Sea is polluted to some extent, where is the origin of debris, and the finding of floating routes and stationary sea.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.67-73
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• 2009

The changes of geomagnetic flux density distribution on the ground surface by underground empty spaces had been investigated through the variations of the soil density and measuring heights. The geomagnetic flux density distributions were monitored for the surfaces of different density, sink-hole and tunnel by fluxgate-type magnetometer. The underground empty space and low soil density decreased the geomagnetic flux densities, which were decreased from the boundary of raw and low-density (empty) grounds, and showed the lowest value at the center of low-density (empty) ground. The decreases of geomagnetic flux density by underground empty spaces could be found at the surface with the tunnel located at 80 m underground. And, the underground defects of empty spaces, low density zone, fracture zone and sink holes could be monitored by the phenomena of this decreasing flux density.

• Economic and Environmental Geology
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• v.11 no.4
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• pp.169-182
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• 1978

The Weolagsan area consists of four units; (1) Low grade meta-sediments of the upper members of Ogcheon age unknown group such as Changri (mainly black slate and phyllitic rock), Majeonri (mainly alternation of slate, limestone and chert) and Hwanggangri Formation (pebble bearing phyllitic sediments); (2) Samtaesan Formation of Chosun System of Ordovician; (3) So called meta-volcanics and (4) Weolagsan Granite and its associations which intruded above mentioned meta-sediments and meta-volcanics. This study was focused to know the Woelagsan granite and its metasomatic effects to the country rocks petrographically and petrochemically. According to the field survey, microscopic work and some chemical analysis, the granite is a "normal granite" based on the Streckeisen's classification and belongs to a mass of the Central-zone younger group in Ogcheon geosynclinal belt. The granite metasomatized the country rocks along its northern contact zone. Zone of calcareous and cherty rocks (Majeonri formation) was silicified partly and skarned locally at the contact with the granite. The chemical analysis of the zone show no difinite variations in contents of $SiO_2$ and CaO with the distance from the granite. It seems to be indicated that the silicification of this part was not so metasomatized by the granite body, but thermally affected as much as to be partially remelted in the specific parts of the formations. Meta-volcanic rock zone was slightly chloritized near contact with the granite. Limestone of Samtaesan Formation was silicified and skarned along the contact zone by the granite body. The chemical analysis of the zone show some noticiable changes in compositions of $SiO_2$ and CaO with distance from the granite boundary. It can be imagined that the silicification of this zone was metasomatically originated by Woelagsan Granite. According to chemical analysis on several trace elements, the ratio of Zn/Cr and Ni/Cr are relatively higher than that of Cu/Cr in the above mentioned silicified zones. Generally the variation of these metal elements in the zones tend to be regular with distance from the granite body.