• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.726-735
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• 2007

Inside the factory buildings of aprecision industry (which produces semiconductors or TFT-LCD), thousands of vibration-sensitive precision equipments operate in the clean rooms. Various utility equipments that are installed around them for proper operation cause various sources of noise and of vibration to exist inside the clean rooms and thus deteriorate the noise and the vibration environment within. In this study, we check if the existing transient vibration phenomenon is caused by the vibrations that arise from operating the utility installed near these equipments; compare and evaluate the vibration criteria of precision equipments regarding the transient vibration phenomenon; and check the efficiency of these criteria.

• Journal of the Semiconductor & Display Technology
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• v.2 no.2
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• pp.25-30
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• 2003

In the case of a vibration sensitive equipment, it require a vibration free environment to provide its proper function. Especially, lithography and inspection device, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved Giga Class semi conductor wafers. This high technology equipments require very strict environmental vibration criteria in proportion to the accuracy of the manufacturing. In this paper, the dynamic analysis and modal test were performed to evaluate the dynamic properties of the constructing clean room structure. Based on these results, a structural dynamic modification(SDM) were required to satisfiy the vibration allowable limit for pression machine. Therefore, in order to improve the dynamic stiffness of clean room structure, the VSD system which can control the force applied on structure, were adopted and its utility were proved from dynamic test results of the improved structure after a modification work.

• Journal of Labour Economics
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• v.31 no.3
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• pp.21-46
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• 2008

This paper estimates of the effect of Clean Workplace Program on industrial accident rates among firms with fewer than 50 workers. The program subsidizes selected firms for work environment improvement. After controling for selectivity and fixed effects in difference-in-difference model, we find that the program reduces the accident rates by 0.34%p, which amount to a decline of 15.8% in total accident rates.

• Ocean and Polar Research
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• v.24 no.4
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• pp.399-406
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• 2002

Trace metals were investigated for the surface seawaters and mussels collected in adjacent sea to the Dokdo during 1999-2000. This study reports the temporal and spatial distributions of trace metals in seawaters and mussels of the Dokdo coastal areas. Clean technique for trace metal analyses was employed in all manipulations including the sampling and pretreatment procedures. The concentrations of dissolved Cu, Cd and Pb in the surface seawaters were similar to those of the previous data in the East Sea. Contents of particulate Al, Fe, Mn and Co were influenced by input of detrital materials from the Dokdo. The average EFs of particulate metals were to the order of Cd > Zn > Pb > Cu > Ni > Mn > Co > Fe, and the high values in Cd and Zn may be closely related to the preferential uptake of biogenic particles. With the exception of Cd, all metal contents in the mussels were in the same ranges with those from other world coastal areas. The Cd accumulation factor of mussel/seawater in this study was abnormally much higher than previous data from the Korean coasts.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.5
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• pp.410-419
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• 2009

Generally, air pollutant emission at workplace is estimated by two methods: indirect methods using emission factors and direct methods based on CEMS (Continuous Emission Monitoring System). CAPSS (Clean Air Policy Support System) is a representative indirect method and the national air pollutant database of Korea. However, characteristics of some workplaces may create a gap between CAPSS and CEMS data. For improving of emission data accuracy, emission data of CEMS (named CleanSYS) equipped at 138 target workplaces were compared with those of CAPSS. As a result, $SO_x$ and $PM_{10}$ emission levels obtained by CAPSS were lower than those of CleanSYS. $SO_x$ and $PM_{10}$emission ratios were 61.5% and 71.2% lower respectively, showing the biggest gaps. On the other hand, $NO_x$ emission of CAPSS was higher by 10.4%. $SO_x$ showed the biggest difference in 'Energy industry combustion' and $NO_x$ did in 'Production Process' within the SCC category. $PM_{10}$ presented a large gap in 'Manufacturing industry combustion.' The differences in $SO_x$ between the two systems occurred because some large-size facilities lack pollution controllers or efficient pollution controllers. Based on this study, CAPSS emission database of Korea will improve accuracy through adopting CEMS emission system, which enables more efficient national atmospheric policies and workplace management.

• Korean Journal of Environment and Ecology
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• v.12 no.4
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• pp.389-397
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• 1999

The purpose of this study was to analyze visitors' behavior in Hallyo-Haesang National Park, Korea. To accomplish the purpose, questionnaire survey, using self-developed questions, was employed from August 21 to 23 in 1998. 303 samples for the survey were selected in 4 different zones(Koje, Tongyong, Namhae, and Odongdo) within park boundary. As the results, socioeconomic characteristics, such as gender, education and income level, age, and others, were showed similar trends with results from visitor surveys in other national parks. Most respondents were pointed out unintentional violation due to habit as a major reason of littering. And, majority of respondents didn't know the Clean-up-Time Movement Program in this park. In addition, ecosystem condition, natural landscape, trash problem, safety, and kindness of park rangers were recognized as the major influencing factors that can affect to visitors' recreation experience in this park but existing conditions for each influencing factor were evaluated lower than level of their expectation. Overall level of recreation satisfaction in Hanryohaesang national park were, however, perceived in the affirmative.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.191-197
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• 2023

The purpose of the study was to provide an educational environment for designing and producing virtual reality practice contents that can be used in semiconductor production lines and clean rooms. Through this process, the user can acquire practical knowledge through experiences close to reality, such as experiencing the main semiconductor solar cell manufacturing facilities as well as procedural knowledge before and after entering the clean room.. In particular, it provides users with an immersion experience close to reality by creating an environment for experiential content necessary for semiconductor and solar cell manufacturing processes and clean room entrance procedure experiential content, which is expected to improve education immersion, realism, cost, efficiency, and education satisfaction. Depending on the characteristics of Dangerous, Impossible, Counter-productive etc, immersive content makes learners immersed in the learning content, induces proactive/active learning, and embodies the learning content, resulting in positive results in the field of improving educational effectiveness.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.383-386
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• 1997

Electrostatic suspension is a method to levitate an object by using electrostatic forces. Its main advantage is to levitate objects without any mechanical contact which fulfills the requirement of an object handling in ultra clean environment. In this paper, the electrostatic suspension system for film-like thin plate such as aluminum sheet, is designed and controlled. In contrast with the conventional electrostatic suspension system which requires the costly and bulky high-voltage amplifiers, it is suggested to use the switching voltage control method in consideration of real industrial application for the handling of such flexible bodies. Some experimental results show that the developed electrostatic suspension system shows good performances to levitate flexible film-like thin plate.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.6
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• pp.621-630
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• 1998

The concentrations of organic carbon (OC) and elemental carbon (EC) in fine aerosols were determined from the samples collected at the two background sites of Kosan in Cheju Island and Kangwha. Samplings were carried out during the spring and winter of 1996 and the fall and winter of 1997. PM25 particles were collected on the prefired quartz filters for 24 hours and analyzed by the selective thermal oxidation method. The concentrations of OC at the sites were higher than those commonly observed from clean areas around the world, but those of EC at both sites were lower than, or comparable to, other clean areas in the world. Both the OC and EC levels at Kangwha were higher than those at Kosan. According to backward trajectory analysis, most air pollutants collected at the two sites were from China. It was found that the OC and EC concentrations in air masses from southern China were higher than those from northern China.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.48-51
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• 1998

This paper presents the transport and removal of organic substances from the contaminated soft soils and sludges such as marine dredging waste, marine sediments, mine tailing waste, and sewage sludge by electroosmosis. A series of laboratory experiments including variable conditions such as contamination levels, solid contents, and applied voltage rates were peformed with the contaminated soft clay specimen mixed with organic substance. Investigated are specimen density, dewatering rate, outflow rate, and outflow concentration. The test results showed that organic substances in the soils were removed by applied voltages. The results indicated that this process can be used efficiently to clean up the contaminated soil.