• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.9
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• pp.85-91
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• 2022

The demand for electric vehicles has increased because of environmental regulations. The lithium-ion battery, the most widely used type of battery in electric vehicles, is composed of a cathode, an anode, and an electrolyte. It is manufactured according to the pole plate, assembly, and formation processes. To improve battery performance and increase manufacturing efficiency, the manufacturing process must be optimized. To do so, simulation can be used to reduce wasted resources and time, and a finite-element method can be utilized. For high simulation quality, it is essential to reflect the material properties of the electrode by considering the pores. However, the material properties of electrodes are difficult to derive through measurement. In this study, the representative volume element method, which is a homogenization method, was applied to estimate the representative material properties of the electrode considering the pores. The representative volume element method assumes that the strain energy before and after the conversion into a representative volume is conserved. The method can be converted into one representative property, even when nonhomogeneous materials are mixed in a unit volume. In this study, the material properties of the electrode considering the pores were derived. The results should be helpful in optimizing the electrode manufacturing process and related element technologies.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.181-183
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• 2002

The accurate permeability for preform is critical to model and design the impregnation of fluid resin in the composite manufacturing process. In this study, the in-plane and transverse permeability for a woven fabric are predicted numerically through the coupled flow model which combines microscopic with macroscopic flow. The microscopic and macroscopic flow which are flows within the micro-unit and macro-unit cell, respectively, are calculated by using 3-D CVFEM(control volume finite element method). To avoid checker-board pressure field and improve the efficiency on numerical computation, A new interpolation function for velocity is proposed on the basis of analytic solutions. The permeability of plain woven fabric is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Based on the good agreement of the results, the relationships between the permeability and the structures of preform such as the fiber volume fraction and stacking effect can be understood. The reverse and the simple stacking are taken in account. Unlike past literatures, this study is based on more realistic unit cell and the improved prediction of permeability can be achieved. It is observed that in-plane flow is more dominant than transverse flow in the real flow through preform and the stacking effect of multi-layered preform is negligible. Consequently, the proposed coupled flow model can be applied to modeling of real composite materials processing.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.399-407
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• 2014

Due to the increase of container terminals, as the volume of terminals become distributed, the competition of preserving existing volume and inviting new volume are becoming fierce, and various ways for processing terminal volume and inviting volume are being sought. Container terminal efforts to maximize efficiency in order to improve the volume handling capability and productivity by both expansion of the latest equipment and development of the latest terminal system. There are a variety of factors that influence the improvement of productivity at container terminals. Among them, in the case of yard transfer equipment, if it were to convert from the method of a Yard Tractor(YT) being fixed allocated to a certain Gantry Cranes(GC) to a Pooling System that processes in a method that properly distributes and allocates a Yard Tractor(YT) to multiple Gantry Cranes(GC), the terminal productivity and the fusibility of YT may be increased. The KPI which is an indicator for the productivity at container terminals is GC productivity and since GC productivity cannot exceed the speed of physical GC operations, a Pooling System is applied to increase productivity which its meaning and effect is massive. Here in the Report, we produce the Pooling Algorithm system to improve the efficiency of the transported equipments in container terminal which is actually applying for this method and have compared Non pooling system with Pooling system in the fields. By introducing a transfer equipment pooling system and enhancing the productivity compared to other terminals, it may become an essential factor for increasing the continuous service quality and profitability in terms of terminal business.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.4
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• pp.492-500
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• 2014

Objectives: The purpose of this study is to estimate the applicability of regional sample collection of environmental samples. The concentration of asbestos fibers were analyzed with two devices. One was an existing commercial air sampling pump that has been proved to be accurate and exact, and the other is a remodeled pump for sample collection which was made from an electric bubble generator originally designed for aquarium fish. Samples were collected with the two devices under the same environmental conditions and collection equipment. A comparative analysis of the concentration of ambient asbestos fiber was then performed. Methods: Based on previous research, six farmhouses with asbestos fiber slate roofs known to have high concentrations of asbestos fiber were selected. Using the existing commercial air sampling pump and the remodeled electric bubble generator, four to seven samples were collected each day one meter downwind from the edge of the slate roof at high volume (about 4 L/min) and low volume (about 1.4 L/min). The analyzer responsible for sample quality control of asbestos fibers counted the number of asbestos fibers with a phase microscope. Results: The rates of flow change of the existed sampler and the remodeled pump at high volume were 0.82% and 0.17%, respectively. The rates of flow change at low volume were 3.83% and 1.09%, but there was not significant difference. The rates of flow change are within the error range (${\pm}5%$) of OSHA analyzing methods. For the high volume sampler, the average asbestos fiber concentration in the air collected by the existed sampler is 6.270 fibers/L and for the remodeled one 5.527 fibers/L, not a significant difference. For the low volume sampler, the average asbestos fiber concentration in the air collected by the existed sampler is 7.755 fibers/L and for the remodeled one 7.706 fibers/L, not a significant difference. The total area of the slate roof of the targeted farmhouse has an effect on the concentration of asbestos fibers in the air from the existing pump and the remodeled one (p<0.01). Conclusions: The sampling function between the existing commercial pump and the remodeled one shows little difference. Therefore, the remodeled pump is considered a pump with a good availability for collecting ambient air asbestos samples.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.1
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• pp.47-54
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• 2021

Calculation of quantity at construction sites is a factor that has a great influence on construction costs, and it is important to calculate accurate values. In this study, topographic model was created by using drone photogrammetry and drone LiDAR to estimate earthwork volume. ortho image and DSM (Digital Surface Model) were constructed for the study area by drone photogrammetry, and DEM (Digital Elevation Model) of the target area was established using drone LiDAR. And through accuracy evaluation, accuracy of each method are 0.034m, 0.35m in horizontal direction, 0.054m, 0.25m in vertical direction. Through the research, the usability of drone photogrammetry and drone LiDAR for constructing geospatial information was presented. As a result of calculating the volume of the study site, the UAV photogrammetry showed a difference of 1528.1㎥ from the GNSS (Global Navigation Satellite System) survey performance, and the 3D Laser Scanner showed difference of 160.28㎥. The difference in the volume of earthwork is due to the difference in the topographic model, and the efficiency of volume calculation by drone LiDAR could be suggested. In the future, if additional research is conducted using GNSS surveying and drone LiDAR to establish topographic model in the forest area and evaluate its usability, the efficiency of terrain model construction using drone LiDAR can be suggested.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.161-167
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• 2017

This paper measured and evaluated the technical efficiency, pure technical efficiency and scale efficiency of port labor via three inputs and three outputs using Data Envelopment Analysis (DEA). First, the average overall technical efficiency measured about 94.18 %, with 100 % pure technical efficiency being larger than 94.18% scale efficiency. As a result, 7 ports were identified as efficient, and 4 ports were identified as inefficient. Among the 4 ineffiecient ports, Donghae had the highest Increasing Return to Scale (IRS). However, the inefficient ports were all found to be less efficient in terms of resource operation than production scale. On the other hand, the efficient ports established priorities using the super efficiency method. As a result, port efficiency was highest for Incheon, Mokpo, Pyeongtaek-Dangjin, Masan, Yeosu Gwangyang, Jeju, and Gunsan-Daesan Ports, in order. In particular, Busan Port, found to be inefficient, would benefit from using Mokpo Port and Incheon Port as benchmarks to increase trade volume and modernize equipment for full-scale commercialization to improve labor efficiency.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.08a
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• pp.203-207
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• 2004

Yangtze River channel is in natural condition for a long time. There are more to be done in grade of navigation and transport. Since 1980's the rate of vessel in JiangSu channel is going up every year, especially for ocean vessels. Meanwhile, the serious factors such as no sailing at night have become a battlement causing the long period for vessels, high cost for shipowners, lower competitiveness for JiangSu ports along the Yangtze River. It also can not meet the port logistic development. After the Ships' Routeing in JiangSu has been carried out. It has improved the safety of navigation in JiangSu area and reduced the risk of pollution or other damage to the marine environment caused by ships colliding or anchoring in or near JiangSu channel. By analyzing, compareing, calculating and model forecasting. The main focus of the paper is put on the study the development of port, channel in JiangSu and efficiency in many fields. Navigation efficiency of the sailing at night; Safety efficiency of reducing the risk by ships; More efficiency of the higher cargo volumes of the other ports in Yangtze River with the increase cargo volume of JiangSu ports along Yangtze River. The purpose of this study is: To get the social and economical efficiency after the Ships' Routeing in JiangSu has been carried out. Also the role of the Ships' Routeing of JiangSu in the development of Port and Channel.

• Journal of Power Electronics
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• v.17 no.1
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• pp.200-211
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• 2017

Conventional boost-full-bridge and boost-hybrid-bridge two-stage inverters are widely applied in order to adapt to the wide dc input voltage range of photovoltaic arrays. However, the efficiency of the conventional topology is not fully optimized because additional switching losses are generated in the voltage conversion so that the input voltage rises and then falls. Moreover, the electrolytic capacitors in a dc-link lead to a larger volume combined with increases in both weight and cost. This paper proposes a higher efficiency inverter with time-sharing synchronous modulation. The energy transmission paths, wheeling branches and switching losses for the high-frequency switches are optimized so that the overall efficiency is greatly improved. In this paper, a contrastive analysis of the component losses for the conventional and proposed inverter topologies is carried out in MATLAB. Finally, the high-efficiency under different switching frequencies and different input voltages is verified by a 3 kW prototype.

• Journal of Environmental Impact Assessment
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• v.14 no.3
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• pp.109-115
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• 2005

This study was conducted to evaluate the efficiency of indoor air cleaners and to inform how to select them correctly to the users. The efficiencies of removing suspended bacteria per hour were $64.3{\pm}13.1%$ for filter, wet, and complex type, respectively, which showed the complex type was the most efficient. The removal efficiencies of formaldehyde (HCHO) after two hours operation of air cleaners showed 88.3% and 81.1% for filter and wet type, respectively. The efficiency of complex type, with removal rate of 55.5~58.4%, was decreased after 30 minutes operation. Therefore, it is recommended to perform over 60 minutes when doing air cleaner certification test for HCHO removal efficiency. Generally, air cleaners having low wind volume showed higher efficiency. All tested air cleaners had no potential for removing of volatile organic compounds (VOCs), which is toxic substances, and it is desirable to develop a device which can control these substances. The results also confirmed that there was no ozone production from all tested air cleaners. And it is recommended to ventilate for 20 minutes every four hours to maintain 50% ventilation status.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.9-14
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• 2000

In this study, the removal efficiencies of organics, nitrogens and phosphorus from municipal wastewater using $A^2$/O process were investigated. BO $D_{5}$ removal efficiencies were indicated 95% and 94% with HRT of 12 hr and 10 hr, respectively. CO $D_{Cr}$ average removal efficiency and concentration of effluent were indicated 87% and 34mg/$\ell$. SS average removal efficiency and concentration of effluent were indicated 93% and 4~17mg/$\ell$. T-N removal efficiency and concentration of effluent were shown as 60~80% and below 15mg/$\ell$. In aerobic basin, removal efficiency of N $H_4$-N was shown over 97% with N $H_4$-N volume load 0.16kg N $H_4$-N/㎥.d and in anoxic basin, denitrification efficiency was indicated over 80% with return sludge rate 0.5Q and internal recirculation rate 2.5Q. Removal efficiency and effluent concentration of phosphorus were shown over 80% and below 2 mg/$\ell$ with return sludge rate 0.5Q.Q.