• Spatial Information Research
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• v.18 no.4
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• pp.1-11
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• 2010

Unlike the previous studies which have focused on 2-dimensional urban characteristics, this paper presents statistical models explaining urban heat island(UHI) effect by 3-dimensional urban morphologic information and addresses its policy implications. 3~dimensional informations of Columbus, Ohio arc captured from LiDAR data and building boundary informations are extracted from a building digital map, Finally NDV[ and temperature data are calculated by manipulating band 3, band 4, and thermal hand of LandSat images. Through complicated data processing, 6 independent variables(building surface area, building volume, height to width ratio, porosity, plan surface area) are introduced in simple and multiple linear regression models. The regression models are specified by Box-Tidwell method, finding the power to which the independent variable needs to raised to be in a linearity. Porosity, NDVI, and building surface area are carefully chosen as explanatory variables in the final multiple regression model, which explaining about 57% of the variability in temperatures. On reducing UHI, various implications of the results give guidelines to policy-making in open space, roof garden, and vertical garden management.

• Spatial Information Research
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• v.16 no.3
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• pp.331-342
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• 2008

The countries are trying to expand the sea limit such as the territorial sea, fishing zone or the exclusive economic zone as far as the Law of the Sea permit to do for the benefit of their national interest. Especially, they are eager to claim the base point where it locates far from the coastline even if it is uninhabited island or reef under the sea. The baseline has been claimed to maximize the territorial sea. Another way to expand the sea limit is to lower the vertical datum to change the land limit. China claimed Dongdo which is located about 79 miles far from the coast as the base point. Japan also claimed many uninhabited island or the reef which is located very far from the coast such as Okino Dorishima. As Korea is the party who negotiate the maritime limit with Japan and China, we should be keen and sensitive on the issues claimed by neighboring countries in terms of base point and the baseline. This paper is to review the characteristics of the base points or baselines of neighboring countries and to suggest the views how to maintain and to relocate our base points. As western coast of Korean peninsula is one of the largest tide fluctuation zone in the world, with long tidal record to prove the vertical datum adjustment, Korea can find the way to lower the vertical datum especially in Yellow Sea. So, major and critical tidal station has to be set up along the western coast to verify tide fluctuation record which can be met with international standard.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.124-132
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• 2016

In order to estimate the effect of flow distributors connected to an upper nozzle of CMT(Core Makeup Tank) on the thermal-hydraulic characteristics in the tank, a simplified 2 inch Small Break Loss of Coolant Accident(SBLOCA) was simulated by skipping the decay power and Passive Residual Heat Removal System(PRHRS) actuation. The CMT is a part of safety injection systems in the SMART (System Integrated Modular Advanced Reactor). Each test was performed with reliable boundary conditions. It means that the pressure distribution is provided with repeatable and reproducible behavior during SBLOCA simulations. The maximum flow rates were achieved at around 350 seconds after the initial opening of the isolation valve installed in CMT. After a short period of decreased flow rate, it attained a steady injection flow rate after about 1,250 seconds. This unstable injection period of the CMT coolant is due to the condensation of steam injected into the upper part of CMT. The steady injection flow rate was about 8.4% higher with B-type distributor than that with A-type distributor. The gravity injection during hot condition tests were in good agreement with that during cold condition tests except for the early stages.

• 한국해양학회지
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• v.19 no.2
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• pp.141-152
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• 1984

In order to investigate the circulation dynamics of the Keum River estuary, 300velocity fields obtained at six sites over two tidal cycles by using instantaneous profiling technique were analyzed in detail. In this investigation, the variability of shear velocity, bottom shear stress, drag coefficient, and roughness length scale were confirmed. The measured values of the bottom boundary drag coefficient show wide range of variations, i.e., C$\_$100/=6.78${\times}$10$\^$-5/∼1.15${\times}$10$\^$-1/, and the mean of 300 measurements is 1.6${\times}$10$\^$-2/. The relationship between U* and C$\_$100/ also show the scatter in values. However, overall mean values over two tidal cycles at 6 stations show that if U* 1cm/s, C$\_$100/ is unpredictable, if U* 1cm/s, C$\_$100/ increase with U*. The values of Re$\_$100/ and C$\_$100/ have scatter. But the overall mean values over two tidal cycles show that if Re$\_$100/ 3.6${\times}$10$\^$5/, C$\_$100/ is unpredictable, if Re$\_$100/ 3.6${\times}$10$\^$5/, C$\_$100/=1.4${\times}$10$\^$-2/. Finally the flow regime of the Keum River estuary was classified as "subcritical fully turbulent" flow.

• Toxicological Research
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• v.22 no.1
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• pp.23-30
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• 2006

Among poly aromatic hydrocarbons, dioxin and PCBs are the most controversial environmental pollutants in our modern life. These pollutants are known as human carcinogens, and liver is the most sensitive target in animal cancer models. Specific aims of the study were focused on the mechanism of carcinogenesis in hepatocytes and the structure-activity relation among these diverse environmental chemicals. Because key mechanisms of dioxin-induced carcinogenesis in human epithelial cell model are the alteration of signal transduction pathway and PKC isoforms, the alteration of the signal transduction pathways and other factors associated with carcinogenesis were studied. Rat hepatocytes cultured under the sandwich protocols were exposed with the various concentration of dioxins and PCBs, and signal transduction pathway, protein kinase C isoforms, oxidant stress, and apoptotic nuclei were evaluated. Since it is important to understand the structure-activity relation among these chemicals to properly assess the carcinogenic potentials, the study analyzed the parameters associated with carcinogenic processes, based on their structural characteristics. In addition, signal transduction pathways and PKC isoforms involved in inhibition of UV-induced apoptosis were also analyzed to elaborate the tumor promotion mechanism of these chemicals. Induction of apoptosis by UV irradiation was optimal at $60\;J/m^2$ in primary hepatocyte in culture. Compared to non coplanar PCBs such as PCB 114 and PCB 153, coplanar PCBs such as PCB 77 and PCB126 showed a stronger inhibition of apoptosis induced by UV irradiation. Production of reactive oxygen species (ROS) was more stimulated by non-coplanar PCBs than coplanar PCBs with the most potent induction of ROS by chlorinated non-coplanar PCB. As compared to the level of induction by PCB126, non-coplanar PCB153 showed a higher increase of intracellular concentrations. Besides the alteration of intracellular calcium concentration, translocation of PKC from cytosolic fraction to membrane fraction was clearly observed upon the exposure of non-coplanar PCB. Taken together, the present study demonstrated that there is a potent structure-activity relationship among PCB congeners and the mechanism of PAH-induced carcinogenesis is structure-specific. The study suggested that more diverse pathways of PAH-induced carcinogenesis should be taken into account beyond the boundary of Ah receptor dogma to assess the health impact of PAH with more accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.817-822
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• 2017

The braking system is one of the most important components in vehicles and machines. It must exert a reliable braking force when they are brought to a halt. Generally, frictional heat is generated by converting kinetic energy into heat energy through friction. As the kinetic energy is converted into heat energy, high temperature heat is generated which affects the mechanical behavior of the braking system. Frictional heat affects the thermal expansion and friction coefficient of the brake system. If the temperature is not controlled, the brake performance will be decreased. Therefore, it is important to predict and control the heat generation of the brake. Various numerical analysis studies have been carried out to predict the frictional heat, but they assumed the existence of boundary conditions in the numerical analysis to simulate the frictional heat, because the simulation of frictional heat is difficult and time consuming. The results were based on the assumption that the frictional heat is different from the actual temperature distribution in a rotating brake system. Therefore, the reliability of the cooling effect or thermal stress using the results of these studies is insufficient. In order to overcome these limitations and establish a simulation procedure to predict the frictional heat, this study directly simulates the frictional heat generation by using a thermal-structure coupling element. In this study, we analyzed the thermo-mechanical behavior of a brake model, in order to investigate the thermal characteristics of brake systems by using the Finite Element method (FEM). This study suggests the necessity to directly simulate the frictional heating and it is hoped that it can provide the necessary information for simulations.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.1011-1019
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• 1998

This work designed Sn-5%Pb-1.5%Ag-x%In solder alloy to develop the solder alloy with low Pb content. This solder alloy doesn't cause environmental pollution. and this study reviewed the probability of replacement of Sn-37%Pb solder as evaluation of melting range, wettability. microstructure, microhardne'ss, tensile strength, drossability of this new solder alloys. The level of international regulation in dissolution amount of Pb ion was 3ppm. But dissolution amount of Pb ion in Sn-5%Pb solder alloy confirmed not to threat the global environmental is 0.46ppm. The melting range of this solder alloy was $183-192^{\circ}C$. Also the range of solidification was very narrow within $5^{\circ}C$. The wettability was similar to Sn-37%Pb solder, and the effect of amount of In addition of wettability couldn't be founded. The probability of replacement in the melting range and wettability is very high. And microhardness of this solder alloy was 1.5 times of conventional type solder. Tensile strength of new solder alloys was a little high than that of conventional type solder. With increasing amount of In% addition, tensile strength was increased, but elongation was decreased. The solder alloy of l%In addition revealed AgSn and Pb on dendrite microstructure boundary, and $Ag_3Sn$, $Ag_3In$ and Pb were revealed on it at the solder alloy of 3% In addition. The drossability was superior to Sn-37%Pb solder alloy and the solder alloys of 2% In addition was not generated for 3hrs.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.813-818
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• 1998

Ultrafine powders of $\textrm{In}_{2}\textrm{O}_{3}$-doped $\textrm{SnO}_{2}$ were synthesized by a coprecipitation method and the effects of pH value and the amount of In2Q addition on particle size were investigated. The influence of pH value on particle size could be negligible, whereas the amount of $\textrm{In}_{2}\textrm{O}_{3}$ has influenced on particle size and specific surface area. The gas sensitivity to hydrocarbOn($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) increased with $\textrm{In}_{2}\textrm{O}_{3}$ addition and reached a maximum at 3wt.% addition. From the results of impedance analysis and I-V characteristics. it was showed that the agglomeration structure of particles and the boundaries between agglomerates were the important factors to determine the gas sensing mechanism.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.513-518
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• 2019

Friction Stir Welding is a welding technique for metal materials that utilizes the heat generated by friction between the material to be welded and the welding tool that rotates at high speed. In this study, a numerical analysis method was used to analyze the change in the internal temperature of the welded material during friction stir welding. As the welding target material, AZ31 magnesium alloy was applied and the welding phenomenon was considered a flow characteristic, in which a melting-pool was formed. FLUENT was used as the numerical tool to perform the flow analysis. For flow analysis of the welding process, the welding material was assumed to be a high viscosity Newtonian fluid, and the boundary condition of the welding tool and the material was considered to be the condition that friction and slippage occur simultaneously. Analyses were carried out for various rotational speeds and the translational moving speed of the welding tool as variables. The analysis results showed that the higher the rotational speed of the welding tool and the slower the welding tool movement speed, the higher the maximum temperature in the material increases. Moreover, the difference in the rotational speed of the welding tool has a greater effect on the temperature change.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.69-76
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• 2018

The present study analyzed the effect of film hole position of 45 degree ribbed cooling channel on film cooling performance of gas turbine blades. We also investigated the influence of the ribs under the fixed blowing ratio. Three-dimensional numerical model was constructed and extensive simulation was conducted using the commercial code (Fluent ver. 17.0) under steady-state condition. Base on the simulation results, We investigated the cooling effectiveness, flow velocity, streamline, and pressure coefficient. Moreover, We analyzed the effect of cooling hole position on ejection of the secondary flow caused by the rib structure. From the results, It was found that internal flow of the cooling channel forms a vortex pair in the counterclockwise from the top side, and clockwise from the bottom side. For the channels with ribs, the vortex flow generated by the ribs caused a higher pressure difference near the hole outlet, resulting in at least 12% higher cooling effectiveness than the channel without ribs. Additionally, when the hole is located on the left side of the ribbed channel (Rib-Left), it can be found that the secondary flow generated by the ribs hits against wall surface near the hole to form a flow in the direction of the hole inclination angle. Therefore, It is considered that the region where the cooling gas discharged to the blade surface stays in the main flow boundary layer is wider than the other cases. In this case, The largest pressure coefficient difference was observed near the outlet of the hole, and as a result, the discharge of the cooling gas was accelerated and the cooling efficiency was slightly increased.