• 한국정밀공학회지
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• 제29권9호
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• pp.938-945
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• 2012

To design and estimate material failures of Type III pressure vessels, which have excellent stability and performance, various modeling techniques have been introduced. This paper provided a hybrid modeling technique composed of ply-based modeling for a cylinder part and laminate-base modeling technique for a dome part for enhancing modeling efficiency. The ply-based modeling technique provided accurate ply stresses directly for predicting material failure, on the other hand, additional manipulations in stress calculations, which may cause some errors, were needed for the case of the laminate-based modeling technique. The ply stresses in fiber, transverse and in-plane shear directions were compared with the corresponding material strengths to predict material failure.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.311-320
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• 2009

Most advanced countries are researching to apply light weight materials far rolling stock because weight reduction for railway body derives cost-saving, energy-saving, and high-speed. Likewise, current Korea rolling stock field makes arduous effects of weight-reduction, miniaturization, and high-efficiency to achieve a high-speed railway. Aluminum becomes suitable material for these projects because it is much lighter than steel or stainless. Manufacturing the railway car body by using the Aluminum is increasing because Aluminum is not bringing the corrosion by unique oxidation-passivate. Aluminum extrusion profile far railway body requires a high mechanical property, accurate shape dimension, and stable quality because the railway body is composed with many different kinds of extruded profiles. Therefore, it is necessary to research about Aluminum precision-extrusion technology to maintain exit temperature and die load. The goal of this project is applying the Aluminum extrusion profile to next-generation railway car body by developing the Aluminum extrusion profile according to precision-extrusion technology which may maintain isothermal exit temperature.

• 유통과학연구
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• 제18권9호
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• pp.67-75
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• 2020

Purpose: The purpose of this study is to enhance sales promotion efficiency for using solid refuse fuel facilities. Renewable energy technology using Solid Refuse Fuel (SRF) is an economic efficiency technology that recovers waste by burning various wastes. A survey on the pollutants discharged from the solid fuels facilities was investigated so that the SRF facilities could be expanded, distributed and reflected in the policy. Research design, data, and methodology: In this study, 9 business sites using SRF and Bio-SRF as main raw materials were investigated for 2 years. The characteristics of target business sites such as the type of fuel used, combustion method, combustion temperature, daily fuel consumption and environmental prevention facilities were studied. Results: The average pollution & ammonia concentration of Bio-SRF facilities was found to be 88.15% higher than that of SRF facilities. But the average acetaldehyde concentration of SRF facilities was found to be 88.15% higher than that of Bio-SRF facilities. Conclusions: The main issue is how much electric power generation using combustible materials affects air pollution. The waste recycling law provides the standard value according to the fuel property, but there is a considerable gap with the mixed fuel. Therefore, for efficient utilization of facilities using solid fuel products, additional research is needed to improve the distribution structure of exhaust pollutants is needed.

• 전력전자학회논문지
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• 제22권4호
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• pp.297-304
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• 2017

The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

• Journal of Microbiology and Biotechnology
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• 제22권6호
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• pp.866-871
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• 2012

A novel cholesterol-based cationic lipid containing a tri-2-hydroxyethylamine head group and ether linker (Chol-THEA) was synthesized and examined as a potent gene delivery vehicle. In the preparation of cationic liposome, the addition of DOPE as helper lipid significantly increased the transfection efficiency. To find the optimum transfection efficiency, we screened various weight ratios of DOPE and liposome/DNA (N/P). The best transfection efficiency was found at the Chol-THEA:DOPE weight ratio of 1:1 and N/P weight ratio of 10~15. Most of the plasmid DNA was retarded by this liposome at the optimum N/P weight ratio of 10. The transfection efficiency of Chol-THEA liposome was compared with DOTAP, Lipofectamine, and DMRIE-C using the luciferase assay and GFP expression. Chol-THEA liposome with low toxicity had better or similar potency of gene delivery compared with commercial liposomes in COS-7, Huh-7, and MCF-7 cells. Therefore, Chol-THEA could be a useful non-viral vector for gene delivery.

• 한국안전학회지
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• 제17권4호
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• pp.25-30
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• 2002

This paper demonstrates the effects of dust electrical resistivity on electrostatic precipitability. The effects of gas temperature, velocity and humidity on the collection efficency were considered by used of coal fly ashes from fluidized bed combustion boiler. The experiments for collection efficiency were carried out in the pilot plant. The ashes which have non-spherical geometry and high electrical resistivity were used. Electrical resistivity is an important property for the collection efficiency in the electrostatic precipitators. Fly ash resistivity as a function of temperature up $350{\circ}C$ and water concentration(up to 15%) has been experimentally investigated using the resistivity test equipment consisted of the movable electrode, dust cup, and furnace. As the resistivity of fly ash in the operating temperature($150{\circ}C$) of an electrostatic precipitator was measured higher than $1010{\Omega}{\cdot}$cm, flue gas conditioning in the electrostatic precipitator to reduce the resistivity of fly ash is required.

• 한국분말재료학회지
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• 제17권6호
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• pp.449-455
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• 2010

The hybrid structured photo-electrode for dye-sensitized solar cells was fabricated based on the composites of $TiO_2$ nanoparticles and nanowires. Three samples with different hybrid structures were prepared with 17 vol%, 43 vol%, and 100 vol% nanowires. The energy conversion efficiency was enhanced from 5.54% for pure nanoparticle cells to 6.01% for the hybrid structure with 17 vol% nanowires. For the hybrid structured layers with high nanowires concentration (43 vol% and 100 vol%), the efficiency decreased with the nanowire concentration, because of the decrease of specific surface area, and of thus decreased current density. The random orientations of $TiO_2$ nanowires can be preserved by the doctor blade process, resulted in the enhanced efficiency. The hybrid structured $TiO_2$ layer can possess the advantages of the high surface area of nanoparticles and the rapid electron transport rate and the light scattering effect of nanowires.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.78-88
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• 2007

In the present study a detailed examination of various porous media models for predicting filtration efficiency and pressure drop of diesel particulate filter (DPF), such as sphere-in-cell and constricted tube models, are attempted. In order for demonstrating their validities of correct estimation on permeability, geometry of property configurations common in commercial cordierite DPFs are correlated to the porous media flow models, and validations of predicted filtration efficiencies due to the use of different unit collectors are made with experiments. The result shows that the porosity, pore size and permeability of cordierite DPF can be successfully correlated by Kuwabara flow field with correction factor of 0.6. The unit collector efficiency predicted by sphere-in-cell model agrees very well with measurements in accumulation mode, whereas that by constricted tube model with significant prediction error.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.675-685
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• 2020

As the classical response surface method (RSM), the polynomial RSM is so easy-to-apply that it is widely used in reliability analysis. However, the trade-off of accuracy and efficiency is still a challenge and the "curse of dimension" usually confines RSM to low dimension systems. In this paper, based on the univariate decomposition, the polynomial RSM is executed in a new mode, called as DPRSM. The general form of DPRSM is given and its implementation is designed referring to the classical RSM firstly. Then, in order to balance the accuracy and efficiency of DPRSM, its adaptive order revision around the most probable point (MPP) is proposed by introducing the univariate polynomial order analysis, noted as RDPRSM, which can analyze the exact nonlinearity of the limit state surface in the region around MPP. For testing the proposed techniques, several numerical examples are studied in detail, and the results indicate that DPRSM with low order can obtain similar results to the classical RSM, DPRSM with high order can obtain more precision with a large efficiency loss; RDPRSM can perform a good balance between accuracy and efficiency and preserve the good robustness property meanwhile, especially for those problems with high nonlinearity and complex problems; the proposed methods can also give a good performance in the high-dimensional cases.

• 대한토목학회논문집
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• 제34권3호
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• pp.885-893
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• 2014

중금속과 총 석유 탄화수소(TPH)로 동시 오염된 복합오염 토양을 정화하기 위해 펜톤 산화와 토양 세정법에 활용되고 있는 $H_2O_2$와 sodium dodecyl surfate (SDS)를 활용하여 강화된 동전기를 연구하였다. 또한, 토양 고유의 특성 차이 및 전극액 농도에 따른 정화 효율의 영향을 확인하기 위해 토양과 농도를 달리하여 실험하였다. 인공적으로 오염시킨 토양에서 10% $H_2O_2$와 20mM SDS를 활용한 실험에서 중금속 정화 효율이 가장 높게 나타났으며, 반면에 같은 농도의 용산 토양 실험에서 토양 고유의 높은 산 완충능력으로 중금속 정화 효율이 떨어졌다. 20% $H_2O_2$와 20mM SDS으로 전극액 농도를 높인 실험을 통해 높은 전류는 토양의 pH에 영향을 주었으며, 이로 인해 중금속 정화에 영향을 미쳤다. TPH의 정화 효율의 경우 용산토양의 높은 산 완충능력과 유기물 함량으로 인해 인공적으로 오염시킨 토양에 비해 산화 효율이 저하되었다. 게다가 40mM의 sodium dodecyl surfate (SDS)의 농도가 주입될 경우, SDS의 scavenger 영향 때문에 TPH 정화에 악영향을 주었다. 토양 고유의 구성성분 및 전극액 농도가 동전기-펜톤 공정의 전기화학적 현상 및 전기삼투유량, 오염물질 정화에 매우 큰 영향을 주는 인자로 판명되었다.