• Atmosphere
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• v.18 no.4
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• pp.317-338
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• 2008

Analyses of observational data and numerical simulations were performed to understand the mechanism of MCSs (Mesoscale Convective Systems) occurred on 13-14 July 2004 over Jindo area of the Korean Peninsula. Observations indicated that synoptic environment was favorable for the occurrence of heavy rainfall. This heavy rainfall appeared to have been enhanced by convergence around the Changma front and synoptic scale lifting. From the analyses of storm environment using Haenam upper-air observation data, it was confirmed that strong convective instability was present around the Jindo area. Instability indices such as K-index, SSI-index showed favorable condition for strong convection. In addition, warm advection in the lower troposphere and cold advection in the middle troposphere were detected from wind profiler data. The size of storm, that produced heavy rainfall over Jindo area, was smaller than $50{\times}50km^2$ according to radar observation. The storm developed more than 10 km in height, but high reflectivity (rain rate 30 mm/hr) was limited under 6 km. It can be judged that convection cells, which form cloud clusters, occurred on the inflow area of the Changma front. In numerical simulation, high CAPE (Convective Available Potential Energy) was found in the southwest of the Korean Peninsula. However, heavy rainfall was restricted to the Jindo area with high CIN (Convective INhibition) and high CAPE. From the observations of vertical drop size distribution from MRR (Micro Rain Radar) and the analyses of numerically simulated hydrometeors such as graupel etc., it can be inferred that melted graupels enhanced collision and coalescence process of heavy precipitation systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.285-293
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• 2016

Soil-foundation-structure interaction (SFSI) is one of the important issues in the seismic design for evaluating the exact behavior of the system. A seismic design of a structure can be more precise and economical, provided that the effect of SFSI is properly taken into account. In this study, a series of the dynamic centrifuge tests were performed to compare the seismic response of the single degree of freedom(SDOF) structure on the various types of the foundation. The shallow and pile foundations were made up of diverse mass and different conjunctive condition, respectively. The test specimen consisted of dry sand deposit, foundation, and SDOF structure in a centrifuge box. Several types of earthquake motions were sequentially applied to the test specimen from weak to strong intensity of them, which is known as a stage test. Results from the centrifuge tests showed that the seismic responses of the SDOF structure on the shallow foundation and disconnected pile foundation decreased by the foundation rocking. On the other hand, those on the connected pile foundation gradually increased with intensity of input motion. The allowable displacement of the foundation under the strong earthquake, the shallow and the disconnected pile foundation, have an advantage in dissipating the earthquake energy for the seismic design.

• Magazine of the Korea Concrete Institute
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• v.8 no.5
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• pp.163-170
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• 1996

Cellulose fibers, being fairly strong and stiff as well as cheap and plentiful with low energy demand during manufacture, are strong contenders for the reinforcement of cement-based materials. Cellulose fiber-cement composites, generally manufactured by slurry-dewatering procedure, can find applications in the production of flat and corrugated cement sheets and many other thin-sheet cement products. This paper presents the results of an experimental study concerned with the effects of fiber content and moisture conditions on the flexural performance of these composites. An effort was also made to study the effect of pozzolanic admixtures on the flexural performance in different moisture conditions. The test results obtained were analyzed statistically using the analysis of variance in order to derive reliable conclusions. The results generated in this study were indicative of significant effects of fiber content and moisture condition of flexural performance. There is a tendency in flexural strength to increase in increase in fiber content up to 8%: flexural toughness values continue to increase even at higher fiber contents. Moisture content has a significant effect on the flexural performance. There is a tendency in flexural strength to decrease and flexural toughness to increase with increasing moisture content Composites incorporating pozzolans showed an increase in the flexural strength while slightly reducing the flexural toughness and were sensitive to variations in moisture content.

• Transactions on Electrical and Electronic Materials
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• v.13 no.5
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• pp.245-247
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• 2012

In this study, ZnO films have been grown on PES (polyethersulfone) of flexible polymer substrate by PLD (pulsed laser deposition) and characterized for crystalline and optical properties. Growing conditions were changed with substrate temperatures ranging from 50 to $200^{\circ}C$ and laser power density ranging from 0.2 to $0.4J/cm^2$. When ZnO thin films are deposited at low temperature with a small laser power density, the (002) peaks of XRD to signify the crystal quality of ZnO thin films appear to be very weak and the (101) peaks to signify the chemical composition of oxygen and zinc are strong. The (002) peaks increase with the substrate temperature and laser power density because the energy needed for the supply of the combination regarding zinc and oxygen has increased. In this study, the best condition for growing ZnO thin film on PES is at a substrate temperature of $200^{\circ}C$ and with a laser density of $0.3J/cm^2$. The characteristics of PL were measured by UV and green luminescence.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.1
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• pp.56-63
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• 1991

This paper aims to describe the relation between the weather condition, especially typhoon and a shipwreck in Korean waters. For this study, it was investigated the statistical characteristics of a shipwreck due to the weather, pressure patterns governing the shipwreck in Korean waters. and the relation between the intensity of typhoon and the amount of a disaster. The results are summarized as follows: 1) The monthly occurrence frequency of a shipwreck was the heighest in July followed by February, March in descending order. 2) The pressure patterns governing the shipwreck were classified broadly into six types and pressure pattern which had most occurrence frequency of a shipwreck was Type V and then cames Type I, Type III and type IV in that order. 3) Occurence frequency of a shipwreck and the amount of a kinetic energy of typhoon have nothing to do with each other. In case of Wind-Typhoon that brought more a strong wind than a heavy rainfall, there were seriously affected ships and buildings by the wind.

• Ocean and Polar Research
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• v.26 no.2
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• pp.207-218
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• 2004

Lomilik Seamount in the west Pacific was seismically surveyed and photographed to illuminate the bottom topography, the condition of manganese crust, and the characteristics of sedimentary environment. Lomilik Seamount has a NW-SE elongated bottom topography with steep slopes in the NESW direction part. Even though the steep slopes of the seamount are devoid of deposits, the summit area and gentle slope of the seamount are covered with thick deposits. The seismic data indicate that Lomilik Seamount is a flat-topped and step-faulted guyot of volcanic origin. Deep-sea camera photographs show that much of the seafloor is rippled in symmetrical and asymmetrical patterns. The traces of biological activity were distinct on gentle seafloor suggesting the low-energy bottom conditions. Some photographs also show outcrops encrusted with manganese crusts. Sedimentary environments in the Lomilik Seamount appear have been governed by regional morphology and strong bottom current.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.772-774
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• 2005

Interstate electric power system, as an alternative for energy cooperation under regional economic bloc, has been hotly debated before progressing the restructure in electric power industry and rapidly expanded in many regions after 1990s. Especially, since northeast asia has strong supplementation in resource, load shape, fuel mix etc., electric power system interconnection in this region may bring considerable economic benefits. Moreover, since Korean electric power system has a great difficulty in a geographical condition to interrupt electricity transaction with other countries, it has been expanded as an independent system to supply all demand domestically. As a result, Korean electric power system makes considerable payment for maintaining system security and reliability and expands costly facilities to supply a temporary summer peak demand. Under this inefficiency, if there are electricity transactions with Russia via the North Korea route then economic electric power system operation may be achieved using seasonal and hourly differences in electricity price and/or load pattern among these countries. In this paper, we estimate price cap of transacted electricity via interstate electric power system in northeast asia. For this study, we perform quantitative economic analysis on various system interconnection scenarios.

• Journal of the Korea Society of Computer and Information
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• v.3 no.2
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• pp.85-97
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• 1998

The existing edge detection methods can not represent the real edge of object at fitting point or detect the edge which has unsufficient connecting trait. Especially, the two-fold thick edge detected by these methods cannot coincide real boundary of subject and it's location. To overcome these problems, we introduce the Genetic Algorithm(GA) in edge detection. The energy function is the value of fixel's satisfaction degree to edge condition. And it consists of the fitness value to image formation type, fitness value to connecting trait to it's neighboring edge and evalulation function which can represents the edge at fitting point as one fixel. This method is superior to remove the noise in edge detection than the existing methods. And it also detects the clear and exact edge because it can find the one fixel which is located at fitting point and has strong connecting trait.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1091-1096
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• 2003

Ion implantation in polymeric materials can induce dramatic chemical modifications, such as bond breaking, cross linking, formation of new chemical products, which have strong influences on the macroscopic properties of the materials. In this study ion implantation was performed onto polymer, PC(polycarbonate), in order to investigate change of the optical transmittance property focusing ultraviolet ray range(200-400nm). PC was irradiated with N, Ar, Kr, Xe ions at the ion energy of 50keV and the dose range of 5 ${\times}$ 10$\^$15/, 1 ${\times}$ 10$\^$16/, 7${\times}$10$\^$16/ ions/$\textrm{cm}^2$. FT-IR, XPS, UV/Vis transmittance spectroscopy measurement technologies were employed to obtain chemical. structural properties and optical transmittance of irradiated polymer. The original PC(unimplanted) is quite transparent that it has more than 88% transmittance in the range UV-A(320∼400nm), but after ion implantation, surface colors were changed to the dark brown and the transmittance of UV ray decreased for all implantation condition, and the absorption edge was shift to visible range with increasing mass of implanted ion species and dose.

• Journal of Environmental Science International
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• v.19 no.2
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• pp.137-148
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• 2010

This paper investigates the characteristics of turbulence schemes. Turbulence closures are fundamental for modeling the atmospheric diffusion, transport and dispersion in the boundary layer. In particular, in non-homogeneous conditions, a proper description of turbulent transport in planetary boundary layer is fundamental aspect. This study is based on the Regional Atmospheric Modeling System (RAMS) and combines four different turbulence schemes to assess if the different schemes have a impact on simulation results of vertical profiles. Two of these schemes are Isotropc Deformation scheme (I.Def) and Anisotropic deformation scheme (A.Def) that are simple local scheme based on Smagorinsky scheme. The other two are Mellor-Yamada scheme (MY2.5) and Deardorff TKE scheme (D.TKE) that are more complex non-local schemes that include a prognostic equation for turbulence kinetic energy. The simulated potential temperature, wind speed and mixing ratio are compared against radiosonde observations from the study region. MY2.5 shows consistently reasonable vertical profile and closet to observation. D.TKE shows good results under relatively strong synoptic condition especially, mixing ratio simulation. Validation results show that all schemes consistently underestimated wind speed and mixing ratio but, potential temperature was somewhat overestimated.