• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.194-198
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• 2012

Crystalline silicon solar cell remains the major player in the photovoltaic marketplace with 80% of the market, despite the development of various thin film technologies. Silicon's excellent efficiency, stability, material abundance and low toxicity have helped to maintain its position of dominance. However, the cost of silicon materials remains a major barrier to reducing the cost of silicon photovoltaics. Using the crystalline silicon wafer with thinner thickness is the promising way for cost and material reduction in the solar cell production. However, the thinner the silicon wafer is, the worse bow phenomenon is induced. The bow phenomenon is observed when two or more layers of materials with different temperature expansion coefficiencies are in contact, in this case silicon and aluminum. In this paper, the solar cells were fabricated with different thicknesses of Al layer in order to reduce the bow phenomenon. With less amount of paste applications, we observed that the bow could be reduced by up to 40% of the largest value with 120 micron thickness of the wafer even though the conversion efficiency decrease by 0.5% occurred. Since the bowed wafers lead to unacceptable yield losses during the module construction, the reduction of bow is indispensable on thin crystalline silicon solar cell. In this work, we have studied on the counterbalance between the bow and conversion efficiency and also suggest the formation of enough back surface field (BSF) with thinner Al layer application.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1487-1501
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• 2011

Recently, fast-growing up railway transportations. Because, regional traffic congestion problem solving and a period of rapid expansion to meet the demand of industries. In addition the government also suggest to new paradigm for the future 'Low Carbon, Green Growth' is presented as a new national vision. To meet the social needs and the time demands, Last of the railway increase very long tunnels and huge deep tunnels. Especially this trend accelerated high speed up in the tunnel, the revision of design criteria and research challenges are being actively improved. Mainly in the tunnel cross-section was under the control of the vehicle train speed 150km/hr by the construction of the vehicle cross-section of the tunnel. More than 200km/hr rail tunnel depending on the vehicle's speed caused the tunnel to the pressure fluctuations will be governed by the aerodynamic changes. Considering the economy to ensure the optimum cross-section of the railway tunnel to the description scheme is selected cross-section of the railway tunnel to determine the size domestic or international railway tunnel for the elements((based on fast Algorithm design criteria, the center line spacing, streetcar line, cross-sectional shape, sectoral issues, such as interface and aerodynamics) based on design practices and to review results. In this study, to propose guidelines depending on the size of a railway tunnel cross section for the size of the determining reasonable factors when designing the railway tunnel and cost-effective standards guidelines.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.356-362
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• 2011

Usually urban railways are built under ground thus the necessary condition of urban railroad, a linear-shaped track, causes a difficulty in enhancement of speed limits of urban rail. Also the underground construction of city railroad produces speed limit values reduced according to a speed code array, in case of speed decision according to the conventional block section division, thus onventionally it could not but apply speed limit values lower than actual safety speeds. In this study, The above two facts induced the author to study on a method to enhance speed limit values for CBTC within existing urban railroad sectors. Since it is possible to exchange data continuously and to control speeds in case of railroads based on CBTC, the author applied result values of speed limits, which were gained based on a railroad condition, a linear track, to the CBTC system without correction of the result values and then the author compared and analyzed, through simulation, the running times and the efficiencies of running energies between railway stations, between the existing fixed-block system and the CBTC system. As a result simulation, the improvement of speed and the deceleration distance of reduction confirmed that it was effective to reduce the time to travel between stations. A fixed block the set of constraints on the speed limit, he way the operation is optimized based CBTC speed limit by suggesting ways to reset the scheduled speed measures to improve were extracted.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.374-374
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• 2011

Recently the construction of railway sections passing the central area of cities and stations under railway lines are increasing, and then it is urgently required to take the countermeasures against the railway vibration and the second-phase noise radiated from it. The most efficient countermeasure, out of technologies developed up to now, is the floating slab track which is the track system isolated from the sub-structure by springs. In other countries, the source technologies for anti-vibration design and vibration isolator - one of key components - have been developed and many installation experiences have been accumulated. However, in Korea, since the system design technology and technologies for key components are not yet developed, the foreign system are being introduced without any adjustment, and the key component, vibration isolator, depends on imports. In this study, based on the results of previous studies of the dust-control device installation using the slab and go through time after lifting impressive when stepped on power generated by the cross-section of the slab and shear connection re-examined the structural stability.

• Fire Science and Engineering
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• v.27 no.2
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• pp.46-53
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• 2013

The architecture environment has changed. The corresponding design criteria should be changed. From July 27th, 2005 the Korea Standard of the fire door changed concerning the smoke resistance test which made the door gap structure more elaborate. However the National Fire Safety Codes are applied by the old data's of England. Which in case differs in the actual construction to the blue print, making the safety standard too excessive. Analyze the results and the phenomenon that occurs due to the difference between design and reality. The National Fire Safety Codes should be revised to leakage crack calculation is presented. Difference of the air flow for the smoke protection due to the stack effect analyzed. Living patterns and evacuation patterns of the apartment reflect and reasonable air flow measurement method are presented.

• Plant Journal
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• v.11 no.2
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• pp.45-51
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• 2015

In this paper, studied condenser operating management which is affecting power plants efficiency considering the cost of poor quality. Sea water temperature and condenser pressure have clear correlation in S power plants. As the sea water temperature changes, condenser pressure changed -1.7~+20 mmHg from design condenser pressure(38.1 mmHg). Use the heat rate correction curve from manufactory company, realized that efficiency and cost of poor quality changed 0.0201%, 12,830 won/h at Unit #1,2 but 0.0155%, 9,832 won/h when condenser pressure 1 mmHg rise. Also, checked that it is changed depend on seasonal corresponding operation, plant ageing and the point of preventive maintenance like overhaul maintenance. This study said if we considered complying with management range and planning overhaul maintenance, then it could help reducing operating maintenance losses minimum 2.5 billion won per 1 year (case : Unit #1, forty days maintenance).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4595-4600
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• 2014

A geoid has great meaning as a vertical reference plane, and at this point when GPS measurement is vitalized, it is an important factor that makes level measurements with GPS possible. This study carried out GPS and leveling of newly created complex control points targeting Daejeon. The geoid for the precise area was built by calculating the plane location, elevation and the geoid of each reference point using GPS/Leveling. In addition, this study evaluated the potential of GPS leveling throughout the site calibration. The geoid for the precise area intervals of approximately 1.5km throughout the study was determined. The results highlight the possibility of leveling by estimating direct leveling performance and mean altitude deviation by less than 2cm. Based on the results, if a geoid model for the precise and wide area can be developed throughout ongoing research, survey tasks that require elevation can be streamlined and the efficiency maximized.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.10 no.1
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• pp.179-207
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• 2000

Hazardous organic solvents management as prescribed by presidential decree in Korea is reviewed. The status of import, manufacture, and circulation of organic solvents was investigated. Problems inherent in the management of organic solvents in the electroplating, metal degreasing, and dry cleaning industries were discussed. The chemical substance management system in Korea was compared to those of foreign organizations. A walk-through check list was developed and then used to assess the actual conditions and potential hazards of chemical substances in these industries. The questionnaire could be used to develop a chemical management system and protect workers from hazardous substances. Based on the results of the site survey, MSDSs were not integrated appropriately into the workers education and were not readily accessible to employees. In the case of the dry cleaning industry, the new dry cleaning solvent used as a substitute includes a lot of potentially hazardous organic solvents. This research is preliminary. It is recommended that a national survey be performed to better identify the current situation. Because chemical substances are regulated by thirteen laws in seven executive branches, management systems often overlap, resulting in ineffective control. Using the above results, a model for managing chemical substances was developed. This will more efficiently provide MSDS information to workers covered by the presidential decree and allow the construction of a management system database for better cooperation with the executive branches in Korea.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.69-79
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• 2012

This pre-supported nail method is able to decrease ground displacements more than NATM because this method reinforces ground with grouted steels before tunnel excavation. Therefore this method has advantage of being able to increase the stability and workability. This study presents applicability of pre-supported nail method with case of site measurement for shallow tunnel composed with high groundwater level and unconsolidated soil, performs this research the mechanism of new supporting system is compared with the conventional existing supporting system in terms of soil reinforcement. NATM has characteristics that construction stage displacement of the apparent height difference is observed in the step of divided excavation processing. Otherwise it is analyzed that pre-supported nail method is not sensitive in the displacement problem of excavation processing in comparison to NATM. It is found that this method is very applicable in shallow depth tunnel such as portal area, tunnel in soil and weak zone without arching effect.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.1
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• pp.44-56
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• 2007

The flora was summarized as 195 taxa; 73 families, 138 genera, 168 species, 23 varieties and 4 forms in Jangsoo-ri windbreak forest and 151 taxa; 63 families, 118 genera, 131 species, 18 varieties and 2 forms in Pyeongsa-ri windbreak forest. Based on the list of the rare plants by the Forest Research Institute, 3 taxa and based on the list of Korean endemic plant 4 taxa were recorded in the studied areas; Puccinellia coreensis (Gramineae), Asarum maculatum (Aristolochiaceae), Prunus yedoensis (Rosaceae), Koelreuteria paniculata (Sapindaceae), Adenophora triphylla var. hirsuta (Campanulaceae). The Specific Plant Species which is categorized by the Ministry of Environment, Korea, was summarized as 23 taxa for the 1 degree of 17 taxa, 3 degree of 5 taxa, 5 degree of 1 taxa in Jangsoo-ri windbreak forest and 22 taxa for the 1 degree of 18 taxa, 3 degree of 3 taxa, 5 degree of 1 taxa in Pyeongsa-ri windbreak forest. From the enlisted the flora surveyed, the naturalized plants were 17 taxa in Jangsoo-ri windbreak forest and 19 taxa in Pyeongsa-ri windbreak forests with the Naturalization rate was 8.7 percent and 12.6 percent, respectively. In Jangsoo-ri windbreak forest, there has been occurred many man-made impair and development without legal institution and control. So, it needs in haste institutional conservation measures and systemic database construction about function and necessity of windbreak forest. In Pyeongsa-ri windbreak forest, recently many people visited here. So, if we make eco-tour place connecting nearby coast and windbreak forest, it will contribute resident's economic profit and opportunity, concerns about windbreak forest, and necessity of conservation measures. Recently, the windbreak forests in Jangsoo-ri and Pyeongsa-ri should be bereaved windbreak forest of function by the human activities.