• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.273-280
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• 2012

The numerical simulation using the Lattice Boltzmann Method in the field of computational fluid dynamics becomes wider in the engineering applications because of its simplicity of update rules compared to the conventional Navier-Stokes solvers. Here, a two-dimensional D2Q9 LB model is numerically tested with a few new computational treatment on the free surface. The single relaxation time is applied under the gravitational field where applied only in the higher density fluid because of its big density difference. At the free surface, the reconstruction techniques in combination with boundary conditions is adopted in order to get some distribution function coming into the fluid site from the air one, and surface tension, early stable test for the gravitional field is considered in it. With the implementation of the gravitational profile, conserving the overall mass and grid dependency are observed during the calculations and freesurface advance track is well captured with an experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.367-375
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• 2013

In this study, the characteristics of the heat transfer coefficient and pressure drop were numerically analyzed according to the axis ratio (AR), pitch, location of vortex generator, and bump phase of the tube surface about an elliptical fin-tube heat exchanger. The boundary condition for CFD analysis was decided as a tube surface temperature of 348 K and inlet air velocity of 1-5 m/s. RSM 7th turbulent model was chosen as the numerical analysis for the sensitivity level. The analysis results indicated that the AR and transverse pitch decreased whereas the heat transfer coefficient increased. On the other hand, there was little difference in the longitudinal pitch. Furthermore, the heat transfer rate was more favorable when the vortex generator was located in front of the tube. Also, the bump phase of the tube surface indicated that the pressure drop and heat transfer were more favorable with the circle type than with the serrated type.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.133-138
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• 2005

Automotive pulleys play a key role in driving the cooling pump, oil pump, air-conditioner and so on by using an engine power. Researches on design processes and technologies of the pulleys can be found in many literatures. On the other hand, the areas related to manufacturing processes of the pulleys have been treated negligently. Vast data extracted from various information systems are transformed, integrated, and summarized to become a special database for helping users make a decision. The database, namely the data warehouse has been popularly used in the marketing and customer management of enterprises and recently applied to improve the design and manufacturing processes. In this study the manufacturing process of pulleys were analyzed through the intensive investigation of shop-floors and the interviews with workers and managers. The defects generated during a manufacturing process were categorized in a few types and the causes of defects examined for extracting the dominant parameters in the setup process for producing pulleys. As the first step to construct the data warehouse for the manufacturing processes of pulleys, authors proposed its architecture focused on the reduction of defect rate during the setup process.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.765-771
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• 2012

$SF_6$ gas has been used as arc quenching and insulating medium for high and extra high voltage switching devices due to its high dielectric strength, its excellent arc-quenching capabilities, its high chemical stability and non toxicity. Despite of its significant contributions, the gas was classified as one of the greenhouse gas in the Kyoto Protocol. Thus, many researches are conducted to find out the replacement materials and to develop the $SF_6$ gas useless electrical equipment. This paper describes experiments on the temperature change-related breakdown characteristics of $SF_6$ gas ($SF_6$) and $SF_6$ liquid ($LSF_6$) in a model GIS(Gas-Insulated Switchgear) chamber in order to show the possibility of more stable and safe usages of $SF_6$ gas. The breakdown characteristics are classified into three stages, namely the gas stage of $SF_6$ according to Paschen's law, the coexisting stage of $SF_6$ gas with liquid in considerable deviation at lower temperature, and the stage of $LSF_6$ and remaining air. The result shows that the ability of the $LSF_6$ insulation is higher than the high-pressurized $SF_6$. Moreover, it reveals that the breakdown characteristics of $LSF_6$ are produced by bubble-formed $LSF_6$ evaporation and bubbles caused by high electric emission and the corona. In addition, the property of dielectric breakdown of $LSF_6$ is determined by electrode form, electrode arrangement, bubble formation and movement, arc extinguishing capacity of the media, difficulty in corona formation, and the distance between electrodes. The bubble formation and flow separation phenomena were identified for $LSF_6$. It provides fundamental data not only for $SF_6$ gas useless equipment but also for electric insulation design of high-temperature superconductor and cryogenic equipment machinery, which will be developed in future studies.

• Journal of the Korean Association of Geographic Information Studies
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• v.2 no.3
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• pp.46-59
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• 1999

Remote sensing provides informations on the changes of the hydrological states and variables over with the temporal and spatial distribution to monitor hydrological conditions and changes for large area. Especially, it can extract a spatial distribution of hydrological parameters such as surface albedo, vegetation informations, and surface temperature to effectively manage water resources of the watershed. In this study, we analyzed the characteristic of temporal and spatial changes in surface hydrological parameters which is necessary to identify the spatial distribution of water resources. 5 Landsat TM data of 1995 which is collected for Bochong-chon watershed, located in the upper stream of Keum River, were used to estimate characteristics on the change of hydrological parameters and atmospheric correction was carried out using COST model. The study showed that the difference of the albedo by the land cover was very sensitive depending upon the change of sun elevation and the amount of water in the soil. The difference between the surface temperature analysis and the measured air temperature was from $2.5^{\circ}C$ to $3.86^{\circ}C$.

• Atmosphere
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• v.22 no.2
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• pp.209-219
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• 2012

Extreme heavy snowfall episodes have been investigated in case of accumulated snowfall amount larger than 50 cm during the past ten years, in order to understand the association of low-level stability with heavy snowfall in the Yeongdong region. In general, the selected 4 events have similar synoptic setting such as the Siberian High extended to East Sea along with the Low passing by the southern Korean Peninsula, eventually inducing easterly in the Yeongdong region. Specifically moist-adiabatically neutral layer has been observed during the heavy snowfall period, which was easily identified using vertical profiles of equivalent potential temperature observed at Sokcho, whereas convective unstable layer has been formed over the East sea due to relatively warm sea surface temperature (SST) about $8{\sim}10^{\circ}C$ and lower temperature around 1~2 km above the surface, obtained from RDAPS. Difference of equivalent potential temperature between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually increased before the snowfall period. Instability-induced moisture supply to the atmosphere from the East sea, being cooled and saturated by the upper cold surge, would make low-level ice cloud, and eventually move inland by the easterly flow. Heavy snowfall will be enhanced in association with low-level convergence by surface friction and upslope wind against Taebaek mountains. This study emphasizes the importance of low level stability in the Yeongdong region using the radiosonde sounding and RDAPS data, which should quantitatively be examined through numerical model as well as heat and moisture supply from the ocean.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.621-629
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• 2020

LRU layout is a complex problem that requires consideration of various criteria such as airworthiness, performance, maintainability and environmental requirements. As aircraft functions become more complex, the necessary equipment is increasing, and unmanned aerial vehicles are equipped with more equipment as a substitute for pilots. Due to the complexity of the problem, the increase in the number of equipment, and the limited development period, the placement of equipment is largely dependent on the engineer's insight and experience. For optimization, quantitative criteria are required for evaluation, but criteria such as safety, performance, and maintainability are difficult to quantitatively compare or have limitations. In this study, we consider the installation and maintenance of the equipment, simplify the deployment model to the traveling salesman problem, Optimization was performed using a genetic algorithm to minimize the weight of the connecting cable between the equipment. When the optimization results were compared with the global calculations, the same results were obtained with less time required, and the improvement was compared with the heuristic.

• Journal of Environmental Impact Assessment
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• v.20 no.2
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• pp.107-121
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• 2011

To assess the impact of climate change on water quality in an impounded river basin, this study estimated future air temperature and rainfall in the years of 2020, 2050 and 2080 by statistically downscaling the simulation results from two GCM models combined with two emission scenarios (A2 and B1). Both scenarios were selected from the Special Report on Emission Scenarios (SRES) suggested by IPCC. The A2 scenario represents an extreme condition whereas the B1 scenario represents a clean and energy efficient condition which is similar to that of study basin. With the results of estimated climate factors and land use data, the discharge and the concentrations of BOD, TN and TP in the Andong dam basins were simulated using the SWAT model. The change in BOD concentration for the B1 emission scenario was greater than the A2 scenario in the annual increase range and the pollution level. The concentration of TN was decreased during March? June which is drought period and increased again afterward. In contrast to TN, the concentration of TP was generally decreased. The change in TP concentration was greater for the B1 scenario than the A2 scenario.

• Korean Journal of Human Ecology
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• v.17 no.5
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• pp.963-973
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• 2008

Clothing pressure is closely connected with the degree of comfort of an athlete's tight-fitting garments. Therefore, the construction of sports garments is very important to the wearer's athletic performance. In this study, the fundamental relationship between the reduction rates of stretch fabrics and clothing pressure was explored with the aim of improving clothing comfort and obtaining a systematic pattern reduction for women's tight-fitting bodysuits. A women's bodysuit pattern was obtained by the draping method using a dressform. The basic pattern was divided into four parts and changed into reduced pattems according to the amount of fabric stretch determined by ASTM D2594. Clothing pressure was measured using an air-pack-type pressure sensor (model AMI 3037-2) at 20 locations (shoulder, 9 locations; bust, 5; and armhole, 6). Among the 15 garments tested, the mean pressure of the A1 bodysuit was 4.60 $gf/cm^2$, and that of the C5 bodysuit was 22.98 $gf/cm^2$. The mean pressures of the bodysuits with reduction rates of 10% and 20% were below 10 $gf/cm^2$, while those of suits with reduction rates of 30%,40%, and 50% (except C5) were below 20 $gf/cm^2$. The pressure at the shoulder was 9.50$\sim$32.24 $gf/cm^2$, which was higher than that at the bust (3.34$\sim$24.56 $gf/cm^2$) and the armhole (0.95$\sim$12.15 $gf/cm^2$). The mean pressures of the 15 bodysuits were divided into five groups using analysis of variance (ANOVA), and were found to be significantly different (p<0.001). Regression analysis afforded the following expression: mean pressure ($gf/cm^2$) = 1.607 + 0.369[reduction rate (%)].

• Journal of the Korean Society of Clothing and Textiles
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• v.37 no.8
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• pp.1060-1074
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• 2013

This study measured and analyzed pressure at each measurement part of imported compression stockings sold in Korea to provide basic information to establish a pressure standard and grade ranking. This study used 40 medical compression stockings imported from 6 countries. Pressure measurements were taken at 11 points: front side and back side of ankle, end-point of the gastrocnemius muscle, front, inner side, back, and outer side of calf, back side of below knew girth, inner side, and outer side of mid-thigh girth, and inner side of thigh girth. AMI 3037-10 and AMI 3037-2 were used for measurements taken inside an environmental chamber at a temperature of $21^{\circ}C$ and a relative humidity (RH) of 65%. For the measurements, 11 air pack sensors were attached to a wooden model leg (Hohenstein) and three measurements were taken at each measurement point in three minutes. The average of these measurements was used for analysis. The findings of this study were as follows. As for the front side of the ankle, of the 40 products, 14 products (6 USA, 2 Swiss, 3 Italian, and 2 Taiwanese) were within the pressure range indicated on the product label; however, no German products fell within the pressure range. A total of 8 products (5 USA, 1 Swiss, 1 Italian, and 1 German) were gradient compression type; however, no Japanese or Taiwanese product were of this type. The majority of products had the highest pressure at the end-point of the gastrocnemius muscle. Only 3 products, 1 USA (Jobst Opaque 30-40mmHg), 1 Swiss (Sigvaris Cotton 34-46mmHg) and 1 Italian (Jobstocking 25-32mmHg), had measurements that met the indicated standard pressure, were a gradient compression type, and met the overall standard for compression stockings.