• Journal of the Institute of Convergence Signal Processing
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• v.9 no.2
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• pp.146-153
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• 2008

Integrated humidity sensor system with two stages operational amplifier has been designed and fabricated by $0.8{\mu}m$ analog mixed CMOS technology. The system (28 pin and $2mm{\times}4mm$) consisted of Wheatstone-bridge type humidity sensor, resistive type humidity sensor, temperature sensors and operational amplifier for signal amplification and process in one chip. The poly-nitride etch stop process has been tried to form the sensing area as well as trench in a standard CMOS process. This modified technique did not affect the CMOS devices in their essential characteristics and gave an allowance to fabricate the system on same chip by standard process. The operational amplifier showed the stable operation so that unity gain bandwidth was more than 5.46 MHz and slew rate was more than 10 V/uS, respectively. The drain current of n-channel humidity sensitive field effect transistor (HUSFET) increased from 0.54 mA to 0.68 mA as the relative humidity increased from 10 to 70 %RH.

• Journal of Conservation Science
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• v.27 no.4
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• pp.415-420
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• 2011

Urethane coating agent was made up in order to prevent corrosion on metal relics. This urethane coating agent was designed to solve problems linked to gloss and discoloration caused by existing acrylic coating agent which is mainly applied to metal relics. For the purpose, the urethane coating agent was made up which has lower gloss and slight color change. This coating agent formed thinner coating layer with excellent adhesion compared to the existing agent and has outstanding resistance to the surface oxidization of metal relics and water repellent on the surface. In addition, the agent is considered a stable coating agent replacing current acrylic coating agent with showing easy dissolution in organic solvents such as acetone, toluene and xylene with excellent result in reversible reaction.

• Economic and Environmental Geology
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• v.41 no.3
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• pp.345-357
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• 2008

Korea has been one of the top ranked countries in the per capita and total consumption of Cu, Zn, Pb, and Ni since economic development based on manufacturing industries. The current instability of mineral demand and supply in Korea is likely to continue or exacerbate in accordance with economic growth in developing countries such as BRICs. Korea needs to increase the self-development portion of strategic mineral resources including Cu, Zn, Pb, and Ni. Our analysis of mineral demand and supply data predicts a long-run instability of supply and demand for main minerals used in the Korean manufacturing industries, and suggests a long range government policy for stable supply of core mineral resources.

• Archives of design research
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• v.21
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• pp.139-147
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• 1997

The concept of package in these day is getting changing with fluctuation of living and management circumstance. The is due to society trancefiguration and change of economic structure and induced to appear small paxkage. These package trend to covert from the class management to total management system and these system made a promotion to development current industry. In these day, with the development of industry and the progress of the life , the package is performing the first faculty such as perservation of manufacture, convenience of keeping and loading in , expedition of sale and additionally the role of package in modern economy is significant for the essen tial element of enterprise prosperity by improving its shape color and materials. It is readilly appearent to anyone in the recycling field that stable markets for collected materials are vitals to any successful program. The recycling movement has increased in popularity throughout the any country: however, it has brought with it a market for them. This attitute also prevails in the political arena where atates or municipalities who are committed to recycling major portion of the solid waste stream are asking these same question regarding the disposition of thte recycled material.

• The Korean Journal of Applied Statistics
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• v.16 no.1
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• pp.1-14
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• 2003

In this study, we suggest the method of small area estimation based on the Economically Active Population Survey (EAPS) data in producing unemployment statistics for the local self-government areas (LSGAs) within large areas. The small area estimators considered are design-based indirect estimators such as the synthetic and composite estimators. The jackknife mean square error was used as a measure of accuracy of such small area estimators. The total unemployed and jackknife mean square errors of the 10 LSGAs within the large area of ChoongBuk region are derived from the estimation procedure suggested in this study, using EAPS data of December 2000. The reliability of small area estimators was assessed using the relative bias values and relative root mean square errors of these estimators. We find that under the current Korean EAPS system, the composite estimator turns out to be much more stable than other estimators.

• The Korean Journal of Applied Statistics
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• v.22 no.3
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• pp.489-498
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• 2009

Underwriting is the first step for the administration of an insurance contract, which may result in stable profitability or unexpected loss for insurance company. Adequacy of underwriting criteria determines underwriting result. Generally, quantitative scoring system is used for underwriting. Method of evaluating risk for the scoring system is summing up scores for risk factors of a potential policyholder in consideration. Scores for each risk factor is predetermined. Current business environment for insurance companies makes underwriting profit more important, which means that insurance companies need more efficient underwriting method. This study suggests a reasonable approach to estimate risk relativities based on generalized linear model. Real data were used to quantify risk levels of groups of insureds for the design of underwriting model. Finally, effects in business volume and profitability of reflecting estimated underwriting scoring system are explained.

• Tribology and Lubricants
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• v.33 no.2
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• pp.59-64
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• 2017

This study investigates friction and wear characteristics of anodized aluminum (Al) alloy 6061 by using a reciprocating tribotester. The diameter and height of the specimen are 30 mm and 10 mm, respectively. The surface roughness of the mirrored-surface is approximately $0.01{\sim}0.02{\mu}m$, and it is used throughout the current study. As a result of anodizing, the depth and diameter of the nanopore are approximately $25{\mu}m$ and 30-40 nm, respectively. The testing conditions are as follows: loads of 1, 3, and 5 N; a frequency of 1 Hz; a stoke of 3 mm; and a duration of 1800 s. We use deionized water with a volume of approximately $25{\mu}l$, as the lubricant. Micro Vickers hardness measurements show that mirrored-surface specimens had lower hardness values than anodized specimens. Further, their coefficients of friction are lower than those of the anodized samples, and the width of their wear track increases with load, as expected. The anodized specimens' coefficients of friction increase with stable frictional behavior and exhibit insignificant load dependence. Further, we observe that the width of the wear track is less than that of the mirrored-surface specimens, and micro cracks are present near it. Moreover, the anodizing process increases the hardness of the samples, improving their wear resistance. These results indicate that nanoporous structures are not effective in lowering friction under the water-lubricated condition.

• Korean Journal of Materials Research
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• v.27 no.3
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• pp.137-143
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• 2017

Boron-doped diamond (BDD) electrode has an extremely wide potential window in aqueous and non-aqueous electrolytes, very low and stable background current and high resistance to surface fouling due to weak adsorption. These features endow the BDD electrode with potentially wide electrochemical applications, in such areas as wastewater treatment, electrosynthesis and electrochemical sensors. In this study, the characteristics of the BDD electrode were examined by scanning electron microscopy (SEM) and evaluated by accelerated life test. The effects of manufacturing conditions on the BDD electrode were determined and remedies for negative effects were noted in order to improve the electrode lifetime in wastewater treatment. The lifetime of the BDD electrode was influenced by manufacturing conditions, such as surface roughness, seeding method and rate of introduction of gases into the reaction chamber. The results of this study showed that BDD electrodes manufactured using sanding media of different sizes resulted in the most effective electrode lifetime when the particle size of alumina used was from $75{\sim}106{\mu}m$ (#150). Ultrasonic treatment was found to be more effective than polishing treatment in the test of seeding processes. In addition to this, BDD electrodes manufactured by introducing gases at different rates resulted in the most effective electrode lifetime when the introduced gas had a composition of hydrogen gas 94.5 vol.% carbon source gas 1.6 vol.% and boron source gas 3.9 vol.%.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.87.2-87.2
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• 2011

Many type of fuel cell stacks have been developed to improve the efficiency of reactants usage. The cascade type fuel cell stack using dead end operation is able to attain above 99% usage of hydrogen and oxygen. It is sectionalized to several parts and the residual reactants which are used previous parts would be supplied again to next parts which have less number of cells in dead end operation stack. The oversupply of reactants which is usually 120%~150% of the theoretical amount to generate current for preventing the flooding effect could be provided to each part except the last one. The final section which is called monitoring cells is supposed to be supplied insufficient the fuel or oxidant that would have some accumulated inert gas from former parts. It makes some voltage drop in the part and the fresh reactants must be supplied to the part for recovering it by venting the residual gas. So the usage of fuel and oxidant is depend on the time and frequency of opening valves for venting of residual gas and it is important to optimize the vent logic for achieving higher usage of hydrogen and oxygen. In this research, many experiments are performed to find optimal condition by evaluating the effect of time and frequency under several power conditions using over 100kW class fuel cell module. And the characteristics of the monitoring cells are studied to know the proper cell voltage which decide the condition of opening the vent valve for stable performance of the cascade type fuel cell module.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.3
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• pp.272-280
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• 2014

Objectives: The purpose of this study was to evaluate the characteristics of worker exposure to hazardous chemical substances and propose the direction of work environment management for protecting worker's health in the semiconductor assembly process. Methods: Four assembly lines at two semiconductor manufacturing companies were selected for this study. We investigated the types of chemicals that were used and generated during the assembly process, and evaluated the workers' exposure levels to hazardous chemicals such as benzene and formaldehyde and the current work environment management in the semiconductor assembly process. Results: Most of the chemicals used at the assembly process are complex mixtures with high molecular weight such as adhesives and epoxy molding compounds(EMCs). These complex mixtures are stable when they are used at room temperature. However workers can be exposed to volatile organic compounds(VOCs) such as benzene and formaldehyde when they are used at high temperature over $100^{\circ}C$. The concentration levels of benzene and formaldehyde in chip molding process were higher than other processes. The reason was that by-products were generated during the mold process due to thermal decomposition of EMC and machine cleaner at the process temperature($180^{\circ}C$). Conclusions: Most of the employees working at semiconductor assembly process are exposed directly or indirectly to various chemicals. Although the concentration levels are very lower than occupational exposure limits, workers can be exposed to carcinogens such as benzene and formaldehyde. Therefore, workers employed in the semiconductor assembly process should be informed of these exposure characteristics.