• Water for future
• /
• v.35 no.5
• /
• pp.43-50
• /
• 2002

The Yellow River Basin located in the Northern part of China is well-known not only as the seriously limited water sources but the greatest sediment-carrying stream in the world. The observed annual average sediment concentration in this area is $37.6kg/\textrm{mm}^3$, and 3.1% of the water volume is occupied by sediments. Due to the reason, water development has been extremely limited and it has been appeared as one of the most difficult problems in reservoir development and management. The major obstacle to surface water uses is reservoir sedimentation so that it has been strongly requested to seek the method managing sediment by optimal fashion. To solve this problem, KOWACO (Korea Water Resources Corporation) has developed various methods on the optimal reservoir management schemes including sediment management for the Upper Fenhe Basin Reservoir System at the cooperation project with Chinese. Information Variable Dynamic Programming. which is one of them, was developed for the reservoir sediment management and a set of non-dominated solutions are generated to choose the best alternative in water supply and reservoir sediment objective problem.

• Journal of Preventive Medicine and Public Health
• /
• v.20 no.1 s.21
• /
• pp.158-164
• /
• 1987

The purpose of this study is to analyze occupational history of coal miners with pneumoconiosis. In this study, occupational characteristics of 49 coal miners with pneumoconiosis were compared with those of 45 coal miners without pneumoconiosis but in similar age category($43{\sim}52$ years of age) based on interview survey. Various indices on occupational characteristics were developed for the following areas: duration of employment, perception of working condition, working density, dust concentration, temperature, humidity, and experience of respirator wearings. Perception of working condition were measured in 5 points scales but experiences of respirator wearing was measured in 3 points scale. Each index was multiplied by duration of employment. From the analysis, only the experience of respirator wearing showed statistically significant difference between the two groups. Therefore, respirator wearing seemed to be effective in reducing occurrence of pneumoconiosis.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.68 no.1
• /
• pp.207-214
• /
• 2019

A large-capacity wireless power system is a technology that transmits electric power of kW or more in a noncontact type. Electric cars, electric buses, and electric railways. In order to increase the power transmission efficiency, a resonance method using a frequency of kHz is applied and the efficiency is 80 ~ 90%. In this case, the loss is 10 ~ 20% other than efficiency, and corresponds to several hundreds of W to several kW in kW class wireless power transmission. 35 kW wireless feed system environment, and induced current in the nearby conductive part was measured. As a result of analysis, it was confirmed that induction phenomenon is higher as the loop configuration of the conductive part per area is dense. The increase of the induced current in the mesh loop is characterized by the density of the nearby conductive part having a permeability per unit area. The concentration of the magnetic field by the permeability is increased and the induction phenomenon causing the induction current is increased. It was confirmed that induction phenomenon increases by about 2.7 times when 9 times dense structure is formed.

• KEPCO Journal on Electric Power and Energy
• /
• v.5 no.2
• /
• pp.83-92
• /
• 2019

Spontaneous combustion propensity of various coals of carbonization grade as a pulverized fuel of coal-fired power plant has been tested from an initial temperature of $25^{\circ}C$ to $600^{\circ}C$ by heating in an oven with air to analyze the self-oxidation starting temperature. These tests produce CPT (Cross Point Temperature), IT (Ignition temperature), and CPS (Cross Point Slope) calculated as the slope of time taken for a rapid exothermic oxidation reaction at CPT base. CPS shows a carbonization rank dependence whereby wood pellet has the highest propensity to spontaneous combustion of $20.995^{\circ}C/min$. A sub-bituminous KIDECO coal shows a CPS value of $15.370^{\circ}C/min$, whereas pet coke has the highest carbonization rank at $2.950^{\circ}C/min$. The nature of this trend is most likely attributable to a concentration of volatile matter and oxygen functional groups of coal surface that governs the available component for oxidation, as well as surface area of fuel char, and constant pressure molar heat.

• KEPCO Journal on Electric Power and Energy
• /
• v.8 no.1
• /
• pp.37-41
• /
• 2022

Because sulfur hexafluoride(SF₆) is classified as one of the six major greenhouse gases, SF₆ handling in power plant such as recovery, purification, and reuse is considered to be important. KEPCO has focused to develop the advanced recovery and purification technology of SF₆ reuse. SF₆ analysis includes the on-site analyses and on-line analyzer; i.e., (1) on-site analysis has an error rate of ±0.5% and (2) on-line analysis has an error rate of ±0.1%, which is possible to adjust operating conditions and to make the work more conveniently by analyzing SF₆ concentration before and after purification step. This paper presents an online analysis method in the SF₆ purification and reuse system. In addition, the analysis results and quality guarantees for each section of the analysis system were presented.

• New & Renewable Energy
• /
• v.19 no.4
• /
• pp.53-60
• /
• 2023

The Computational Fluid Dynamics (CFD) model is a method of studying the flow phenomenon of fluid using a computer and finding partial differential equations that dominate processes such as heat dispersion through numerical analysis. Through CFD, a lot of information about flow disorders such as speed, pressure, density, and concentration can be obtained, and it is used in various fields from energy and aircraft design to weather prediction and environmental modeling. The simulation used for fluid analysis in this study utilized Gexcon's (FLACS) CODE, such as Norway, through overseas journals, for the accuracy of the analysis results through many experiments. It was analyzed that a technology for treating two or more catalysts with physical properties under low-temperature atmospheric pressure conditions could not be found in the prior art. Therefore, it would be desirable to establish a continuous plan by reinforcing data that can prove the effectiveness of producing efficient synthetic oil (renewable oil) through the application that pyrolysis under low-temperature and atmospheric pressure conditions.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.34 no.4
• /
• pp.269-274
• /
• 2008

In this study we successfully altered the structural characteristics of the mica surface and were able to control oil-absorption by using the microwave enhanced etching (MEE) technique, which has originally been used in semiconductor industry. When microwave energy is applied to the mica, the surface of the mica is etched in a few minutes. As the result of etching, oil-absorption of the mica was enhanced and surface whiteness was improved by modifying the silicon dioxide layer. Additionally, the high whiteness was maintained even though the etched mica absorbed the sebum or sweat. The surface modification of mica was performed by microwave irradiation after the treatment of hydrofluoric acid. The degree of etching was regulated by acid concentration, irradiation time, the amount of energy and slurry concentration. The surface morphology of the etched mica appears to be the shape of the 'Moon'. The characteristics of surface area and roughness were examined by Brunauer-Emmett-Teller (BET) surface area analysis, atomic force microscopy (AFM), scanning electron microscopy (SEM), spectrophotometer and goniophotometer.

• Journal of the Korean Society for Railway
• /
• v.19 no.3
• /
• pp.280-287
• /
• 2016

In railway tunnels, dust is generated when trains run due to the contact between the wheels and the rails. The generated dust is suspended due to the train-induced airflow, with some of it deposited due to gravitational sedimentation. In this study, the diurnal variation of the dust concentration was investigated in a railway tunnel. A single lane of a tunnel was selected in which to observe more easily the dust concentration due to the passing of a train. Four particle-measuring instruments were utilized to detect dust ranging from 5nm to $20{\mu}m$. To synchronize the train passing time at the measuring location, a three-dimensional ultrasonic anemometer and a video camera were used. It was found that the dust concentration was significantly increased from $50{\mu}g/m^3$ to $150{\mu}g/m^3$ due to the train. Particularly, the dust concentration was greatly increased to more than $250{\mu}g/m^3$ during the morning rush-hour times.

• KEPCO Journal on Electric Power and Energy
• /
• v.3 no.1
• /
• pp.29-34
• /
• 2017

Leaching kinetics for extracting yttrium from the coal fly ash was investigated in the presence of sulfuric acid during extraction. The leaching kinetics of yttrium were conducted at reactant densities of 5~1,000 g coal fly ash per L of $1.0{\sim}10.0N\;H_2SO_4$, agitation speed of 250 rpm and temperature ranging from 30 to $90^{\circ}C$. As a result, the leaching kinetic model was determined in a two-step model based on the shrinking core model with spherical particles. The first step was proceeded by chemical reaction at ash surface, and the second step was proceeded by ash layer diffusion because the leaching conversion of yttrium by the first chemical reaction increases with increased the time irrelevant to the temperature whereas it increases with increased the leaching temperature. The activation energy of the first chemical leaching step was determined to be $1.163kJmol^{-1}$. After the first chemical reaction, the activation energy of ash layer diffusion leaching was derived to be $41.540kJmol^{-1}$. The optimum conditions for leaching the yttrium metal of 60 % were found to be the slurry density of 250 g fly ash per L of $H_2SO_4$, solvent concentration of $2.0N\;H_2SO_4$, second step leaching of temperatures of $30^{\circ}C$ for 3 hours and then $90^{\circ}C$ for 3 hours at agitation rate of 250 rpm.

• KEPCO Journal on Electric Power and Energy
• /
• v.3 no.1
• /
• pp.41-47
• /
• 2017

After $SF_6$, which is being used in power equipment as an insulating material, is classified as one of the 6 major greenhouse gases, the maintenance and the refinement of used $SF_6$ started to get attention. In regard to this, KEPCO Research Institute (KEPRI) is developing $SF_6$ recovery and refinement technology starting with establishing a comprehensive $SF_6$ analysis system. With the analysis system, qualitative and quantitative analyses of the purity and the impurities of $SF_6$ before and after recovery, and before and after refinement have been carried out. The analysis system is comprised of GC-DID (Gas Chromatograph -Discharge Ionization Detector) for trace impurities analysis, GC-TCD (Thermal Conductivity Detector) for analyses of $SF_6$ purity and major impurities concentration from several hundred ppm up to percent range, GC-MSD (Mass Selective Detector) for analyses of impurities not included in standard gas, FT-IR (Fourier Transform-Infrared) Spectrometer for analysis of HF and $SO_2$, and moisture analyzer for analysis of moisture below 100 ppm. With this analysis system, complete analysis method of $SF_6$ has been established. This analysis system is being used in the maintenance of power equipment and the development of $SF_6$ recovery and refinement technologies. In this paper, the analysis results of four samples - gas and liquid phase $SF_6$ samples from a $SF_6$ refinement system before and after refinement are presented.