• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.491-497
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• 2010

The magnetic polishing is the useful method to finish some machinery fabrications by using magnetic power. This method is one of the precision techniques and has an aim for clean technology in the clean pipes. The magnetic abrasive polishing method is not so common in the field of machine that it is not known to widely. There are rarely researcher in this field because of non-effectiveness of magnetic abrasive. This paper deals with mediocritizing magnetic polishing device into regular lathe and this experiment was conducted in order to get the best surface roughness at low cost. This paper contains the result of experiment to acquire the best surface roughness, not using the high-cost polishing material in processing. In this paper, We could have investigated into the changes of the movement of magnetic abrasive grain. In reference to this result, we could have made the experiment which is set under the condition of the magnetic flux density, polishing velocity according to the form of magnetic brush.

• Clean Technology
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• v.30 no.3
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• pp.211-219
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• 2024

3D printing technology has created a paradigm shift in industries by achieving breakthrough innovations and enabling the fabrication of complex products. However, 3D printed parts are inferior in terms of their strength and surface quality compared to parts fabricated by conventional manufacturing methods. This study aims to improve the surface roughness of stereolithographic parts by experimental analysis of the generated area error. A photocurable polymer material was used for fabrication, and the effect of important parameters, such as the material viscosity, printing speed, pneumatic pressure, UV intensity, and pattern spacing, on the surface roughness were analyzed. The results showed that a high-viscosity (12,000 cP) thixotropic material formed a constant pattern with an aspect ratio of 1:1, and the pattern shape was maintained after printing. A pattern with a minimum thickness of 145 ㎛ was formed at a printing speed of 70 mm/s and a pneumatic pressure of 20 kPa. These parameters were found to be suitable for low surface roughness. A UV laser at an intensity of 10 ~ 30 mW/cm² was used to form a smooth surface at low curing intensities. Moreover, it was seen that with a pattern spacing of 110 ~ 130 ㎛, a stereolithographic part with a low surface roughness of Ra 1.29 ㎛ could be fabricated.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.2
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• pp.128-135
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• 1991

To obtain the basic information of environmental working status in mercury industries in Korea, 26 mercury industries were investigated with mercury concentration in air and various factors affecting on workplace environment. The results were as follows : 1. The mean air concentration of mercury was $0.046{\pm}0.035mg/m^3$ in 26 mercury industries. 2. The highest mean air concentration of mercury among 26 mercury industries classified by type of product was found in sodium hydroxide manufacturing industries ($0.054{\pm}0.020mg/m^3$) and the lowest mean was found in mercury battery manufacturing industries ($0.003{\pm}0.002mg/m^3$). 3. While the highest' mean air concentration of mercury was found in manual method ($0.061{\pm}0.041mg/m^3$) among the types of operation method, lowest one was found in automatic method ($0.035{\pm}0.025mg/m^3$). 4. While the mean air concentration of mercury was $0.023{\pm}0.018mg/m^3$ in good clean status of workshop, the mean air concentration of mercury in bad clean status was $0.06{\pm}0.033mg/m^3$. Among various factors affecting on th e air concentration of mercury, clean Iiness of workshop showed statistically significant difference with air concentration of mercury, and automation of workshop and local exhaust ventitlation also played important role in control the air concentration of mercury in the working environment.

• Corrosion Science and Technology
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• v.17 no.6
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• pp.279-286
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• 2018

Austenitic stainless steels used in nuclear power plants mainly use pipes made of seamless pipes, which depend on imports. The manufacturing process and high cost are some of the problems associated with seamless pipes. Therefore, in this study, the corrosion characteristics of the seamless pipe and the SAW pipe were assessed to determine the safety and reliability of the SAW pipe in a bid to replace the seamless pipe. Microstructure was analyzed using an optical microscope and the degree of hardness was measured using a Rockwell B scale. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. Anodic polarization test was performed in deaerated 1% NaCl solution at $30^{\circ}C$ and the U-bend method was used to evaluate the SCC resistance in 0.01 M $Na_2S_4O_6$ at $340^{\circ}C$ and 40% NaOH solution at $290^{\circ}C$. Weld metal of the SAW pipe specimen showed relatively high degree of sensitization and intergranular corrosion rate. However, annealing to SAW pipes improved the corrosion properties in comparison to that of the seamless pipe.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1249-1255
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• 2011

In modern large-scale semiconductor manufacturing clean rooms, the energy consumed by the outdoor air-conditioning system during heating, humidification, cooling, and dehumidification of the incoming outdoor air represents about 45% of the total air-conditioning load required to maintain a clean-room environment. In particular, the energy required for humidification of the outdoor air in winter is very high. Therefore, evaluation and comparison of the energy consumption in key humidification systems, viz., steam-humidification and water-spray-humidification systems, used in outdoor air-conditioning systems would be useful to reduce the outdoor air-conditioning load in clean rooms. In the present study, an experiment with an outdoor air flow of 1000 $m^3$/h was conducted to compare the air-conditioning process and energy consumption in outdoor air-conditioning systems with electrodeboiler steam humidifiers and air-washer water spray humidification systems. The experimental results showed that the water-spray-humidification-type outdoor air-conditioning system consumed less electrical power than did the steam-humidification-type system and was more energy efficient during winter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.1
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• pp.7-13
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• 2013

Bio Clean Room(BCR) and pharmaceutical product manufacturing facilities require careful assessment of many factors, including HVAC, controls, room finishes, process equipment, room operations, and utilities. Flow of equipment, personnel, and product must also be considered along with system flexibility, redundancy, and maintenance shutdown strategies. It is important to involve designers, operators, commissioning staff, quality control, maintenance, constructors, validation personnel, and the production representative during the conceptual stage of design. Critical variables for room environment and types of controls vary greatly with the clean space's intended purpose. It is particularly important to determine critical parameters with quality assurance to set limits and safety factors for temperature, humidity, room pressure, and other control requirements. In this paper, oxygen cluster ion equipment was utilized in order to enhance the indoor air quality and to prevent the airborne infection of ward in hospital. Moreover, the performance test of the equipment was also performed in order to develop the optimal sterilization system of BCR using the equipment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.122-128
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• 2021

Machining operations require removal of chips to keep the coolant clean and fresh throughout the operation time. In this study, microchip removal equipment was developed using AutoCAD and CATIA programs for 3D modeling and 2D draft. In addition, the flow analysis and electromagnetic field analysis of the equipment were performed using the COMSOL Multiphysics program. The flow design of the coolant oil tank was realized on the basis of fluid analysis results. Further, on the basis of magnetic density analysis, a conveyer was designed for effectively removing metal microchips in the tank by using arrays of neodymium permanent magnets.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.36 no.2
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• pp.1-7
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• 2013

Cleanroom could be largely classified into industrial cleanroom that can be contaminated by particles and bio-cleanroom that can be contaminated by biological particles. Electrical manufacturing companies producing precision machines and electrical parts essentially have industrial cloom facilities and clean technologies to produce defects free products due to particles. Industrial cleanroom should be controlled in respect of 4M1E to prevent from foreign materials of sub-micro unit and to keep out contamination sources from outside. In this paper, a concept for a quantitative methodology to measure the particles from running components was suggested by combining both newly making clean booth such as wear tester and laser particle counter.

• Clean Technology
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• v.2 no.2
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• pp.201-213
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• 1996

Environmental regulation has traditionally focused on specific phenomena and adopted the so-called end-of-pipe approach. Recently, however, the new environmental paradigm is more concerned with minimization of waste generation, efficient material and energy use, pollution prevention, etc. The basis of above concept is that one must consider the environmental impacts of a product not only during its manufacturing stage, but during all life stages. In the present study, the current status of LCA and its importance to environmental impacts have been reviewed. In the usual approach to LCA, screening LCA method has been used to promote international competition and define environmental concerns during semiconductor manufacturing. In the present study, a review of semiconductor manufacturing process and its environmental implication has been conducted to quantify the material and energy requirements, minimize the waste generation, and evaluate production cost. Recommended activities are also specified for process modification to improve the process efficiency.

• Clean Technology
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• v.15 no.4
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• pp.253-257
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• 2009

The waste solution discharged form the LCD(Liquid Crystal Display) manufacturing process contains phosphoric acid, nitric acid, acetic acid and metal ions such Al and other impurities. In this study, vacuum evaporation and diffusion dialysis was developed to commercialize an efficient system for recovering the high-purity phosphoric acid and manufacturing monoammonium phosphate. By vacuum evaporation, almost 99% of nitric and acetic acid was removed. Also, by diffusion dialysis, about 97.5% of Al was removed. Monoammonium phosphate was manufactured from purified phosphoric acid and ammonium hydroxide. In order to get the optimum manufacturing condition, the molar ratio of ammonium hydroxide and phosphoric acid, pH and temperature was controlled. Using this optimum condition, we obtained the recovery rate of monoammonium phosphate of about 90%.