• 한국환경과학회지
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• 제25권6호
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• pp.829-837
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• 2016

The mechanism of micro-bubble generation with a pump is not clarified yet, so the design of water treatment systems with a micro-bubble generating pump is based on trial and error methods. This study tried to explain clearly quantitative relationships of experimental micro-bubble concentration ($C_{air}$) of continuous operation tests with a micro-bubble generating pump and theoretical air solubility. Operation parameters for the tests were discharge pressure ($P_g$), water ($Q_{w0}$) and air ($q_0$) flow rates, orifice diameter ($D_o$), and retention time (t). The experimental micro-bubble concentrations ($C_{air}$) at 4.8 atm of discharge pressure ($P_g$) were in the range of 21.04 to 25.29 mL/L. When the retention time (t) by changing the pipe line length ($L_p$) increased from 1.22 to 6.77s, the experimental micro-bubble concentrations ($C_{air}$) increased from 25.86 to 30.78 mL air/L water linearly. The dissolved and dispersed micro-bubble concentrations ($C_{air}$) are approximately 4 times more than the theoretical air solubility.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.776-781
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1MW organic Rankine cycle system was designed and developed. The exhaust gases of $175^{\circ}C$ at two 100MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1MW as designed but only 670kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.947-952
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• 1997

The magnetic polishing is the useful method to finish using magnetic power of a magnet. The time hasn't been that long since the magnetic polishing method was introduced to korea as one of precision polishing techniques. However, the reasons for not being spreaded widely are the magnetic polishing method don't have mediocrity for machine, the efficiency of magnet-abrasive is confined as a bad polishing, and there are not many researchers in this field. The mechanism of this R&D is dealing with the dynamic state of magnet-abrasive. This paper deals with mediocritizing magnetic polishing device into regular lathe and this experiment was conducted in order to get a best surface roughness with low cost. Beside the subsidiary experiment was performed using the mixed magnet-abrasive with general alumina, barium. This paper introduced the main reason for difficulty using this method in industrial field. It needs more continues research on it. This paper contains the result of experiment to acquire the best surface roughness, not using the high-cost polishing material in processing. The average diameters of magnet-abrasive are the particles of 150 $\mu\textrm{m}$, 250 $\mu\textrm{m}$.

• 대한기계학회논문집
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• 제17권6호
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• pp.1596-1608
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• 1993

본 연구에서는 좀더 정량적인 이론에 바탕하여 제레이놀즈수 2차모멘트 난류모형을 유도하려 한다.

• 대한조선학회 특별논문집
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• 대한조선학회 2011년도 특별논문집
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• pp.55-62
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• 2011

Although the performance of the commercial vessel has been dramatically improved through innovations, there has been no big changes on the traditional anchoring method of commercial vessels, both on design and operation until now. In this paper, two cases of design modifications were introduced for optimized design of pocket type anchor handling, which resulted in improved performance of the vessel's anchoring. From the first time fully balanced type anchors were applied on vessels in Korean shipyard, main design problem on this application was that the anchor doesn't normally slide into the pocket when the anchor fluke is not in line with pocket, as the anchor freely rotates by the swivel on forerunner. In order to prevent the problem, swivel has been deleted on the forerunner to prevent anchor rotation until now, but this solution caused problems such as twist lock of anchor chain, restriction of windlass direction, etc. On this paper, one of the solution is introduced to overcome the design problem by tilting the hawse pipe to some extent, which makes anchor turned at the time anchor ring touches the pocket skirt and that it properly slides into the pocket. Secondly, one of the solution is introduced to overcome misalignment problem between anchor chain cable and roller of chain compressor, which has been frequently occurred, by modification of roller design.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.407-413
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• 2006

Railways are very important to get stability of railway structure as transportation system carrying a lot of passengers and freight. These days the construction of underground railway crossing such as expansion of new roads, construction of subway and gas pipe is increasing because of economic and social development. But these kinds of construction didn't take into account Cost-benefit analysis of railway which has the most important aspects of railway safety, so the results of construction didn't get a good evaluation. This study adapt Cost-benefit analysis to evaluate the economic validity of underground railway crossing. This study adjust about Cost-benefit analysis of railway part, and analyze the new method and technology of underground railway crossing constructed by Korean National Railroad and Railway Network Authority. Also this study divide between high frequency line and low frequency lineusing B/C, NPV, and IRR analysis. After analysis, B/C ratio method is the most suitable method among B/C, NPV, and IRR analysis method. Therefore this study can express economic benefit quantitatively and decrease the cost by adapting Cost-benefit analysis, and can clearly express the construction feasibility and investment effects of construction of underground railway crossing method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.144-146
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• 1995

A superconducting 2 tesla MRI magnet for the animal magnetic resonance imaging has been developed as a basic model for the application of the precise supercoducting magnet technology. MRI cryostat with 210mm room temperature bore was designed and manufactured for this magnet. The cryostat was designed basically not only to extract the principal design parameters at the performance test but also for the convenience of the manufacturing. The most extinct feacture of the cryostat is that it does not have $LN_{2}$ tank and the 77K thermal shield is cooled by circuling $LN_{2}$ through copper pipe which is welded around the shield plate. It results in reduction of the total cryostat size(about 30%).

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권2호
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• pp.109-115
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• 2004

This paper deals with the behaviors of magnetic flux density near down-conductors by lightning currents. The background on the principle of magnetic flux density measurements using the RL self-integrating magnetic field sensor was described. The magnetic flux density measuring device consisting of RL self-integrating magnetic field sensor and differential amplifier was designed and fabricated. The frequency bandwidth of the magnetic flux density measuring system ranges from 200 Hz to 300 KHz and the response sensitivity was 0.126 $\mu$T/㎷ The distributions of the magnetic flux density near down-conductors due to impulse currents with various rise times were analyzed as a parameter of the bonding conditions and materials of conductor and wiring conduits. The magnetic flux density due to impulse currents was inversely proportional to the distance between the down-conductor and measuring point. The amplitude of the magnetic flux density for PVC Pipe with down-conductor was 72 $\mu$T/㎷ at the distance of 1m and was higher than for steel conduits and coaxial cable. Finally the magnetic flux density is increased with increasing the di/dt it and oscillation frequency of lightning currents in this experimental ranges.

• 자원환경지질
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• 제31권3호
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• pp.223-233
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• 1998

The environments in the vicinity of the Dalseong mine has been much contaminated by heavy metals related to CuW ore deposit, which is of hydrothermal pipe type mineralized by quartz monzonite in the andesitic rocks. Chalcopyrite and wolframite are major ore minerals and sphalerite, galena and others are associated. To investigate the contamination of heavy metals in plants, samples of plants and soils were analysed by ICP for Fe, Mn, Cu, Pb, Zn, Ni, Co, Cd and Cr. Most of ore-related heavy metals are anomalously high in plants and soils, which were contaminated by the development of Taehan Tungsten Mining Company. The mine produced 48,704 tons (M/T) of 4 wt.% Cu and 1,620 tons (S/T) of 70 wt.% of $WO_3$ during active mining activity from 1961 to 1971 but was closed in 1975. Wild plants growing at the mine area may be used to remove heavy metals form soils, which cause contaminations of plants, stream waters and groundwaters in the vicinity of the mine.

• 대한조선학회 특별논문집
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• 대한조선학회 2013년도 특별논문집
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• pp.30-34
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• 2013

Prevention of exhaust gas back flow becomes a great interest to shipyards and shipowners in large container carriers because exhaust gas pollutes cargoes, flows back into the deck house and the engine room area through fresh air intakes and fan rooms, gives harmful damages to the crew's health and also gives thermal damages to electric equipments on the navigation deck. The phenomena of exhaust gas back flow has been studied with the analysis of sea trial records and wind tunnel tests and the height of the exhaust gas pipe, the front area of the deck house, the inflow speed and the position of the radar mast platform has been confirmed as the principal factors of exhaust gas back flow phenomena. The simple empirical formula to estimate exhaust gas back flow phenomena and the design guidances of exhaust gas related structures on deck has been introduced. In future, parametric studies for the exhaust gas back flow factors will be carried out with the CFD analysis. The results of this study will be the guide for development of the prevention method of exhaust gas back flow phenomena for large container carriers.