• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.10
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• pp.1031-1037
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• 2010

This paper proposed lightweight aluminum bipolar plates as an alternative for conventional graphite bipolar plates in fuel cell systems used as a power source for small reconnaissance UAVs. Since bipolar plates occupy more than 80% of the total weight of the fuel cell system, lightweight aluminum bipolar plates can improve the overall payload and flight time of the fuel cell UAV. The aluminum and graphite bipolar plates were fabricated to compare the performance of each of them. A 15% higher performance per weight was obtained from aluminum bipolar plates than the graphite bipolar plates. Also, the performance of a single cell using aluminum bipolar plates was evaluated under various operating conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1314-1321
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• 2010

The west express way which links south west area of the central city of Seoul has been notorious for extremely heavy traffics since its first opening in 1991(i.e. the average vehicle speed is less than 25km/h, a daily traffic is 112,000 and among them, more than 94% of the vehicles are the light vehicles). The city government recently initiated a new BTO(Build-Transfer-Operate) project as an alternative in releasing heavy traffic and a high construction cost. The proposed underground express road is the first double-level tunnel (i.e. a total length of road is 10,91km and the tunnel is 9.308km long) ever built in South Korea, while such tunnel system is not new worldwide as such A86 East tunnel in France, SMART tunnel in Malaysia, and Fuxing tunnel in China. This paper discusses major design issues regarding the internal structures such as deck slab, and secondary liner.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.826-831
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• 2004

Recently, studies have been carried out to develop unmanned Micro Air Vehicles(MAVs) that can search and monitor inside buildings during urban warfare or rescue operations in hazardous environments. However, existing fixed-wing and rotary-wing MAVs cannot travel at extremely low or high speeds, hover in place, or change directions instantly. This has lead researches to search for other flight methods that could overcome those drawbacks. Insect flight principles and its applications to MAVs are being studied as an alternative flight method. To take flight, insects flap and rotate their wings. These wing motions allow for high maneuverability flight such as hovering, vertical take off and landing, and quick acceleration and deceleration. This paper proposes a method for designing a mechanism that reproduces hovering insect flight, the basis for all other forms of insect flight. The design of a mechanism that can reproduce the motion that causes maximum lift is proposed, the required specifications are calculated, and a method for reproducing hovering insect flight with a single motor is presented. Also, feasibility of the design was confirmed by simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.231-236
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• 2004

The area of flat glass panel displays such as LCD (Liquid crystal display) and PDP (Plasma display panel) has been increased more than 2 $\times$ 2 m$^2$ for productivity improvement. However, such a large panel area incurs large panel deflection during panel transfer using robots or AGV (Automated guided vehicle) systems. Therefore, electronic industries are making an effort to find an alternative transfer system for the large glass panels with small deflection. The air conveyor with porous pads is one plausible solution, but it becomes expensive because the large porous pads cost much and air consumption increases as the panel area increases. In this work, a simple air slit levitating conveyor was devised to lower the equipment cost and to reduce the air consumption of system. The air flow model between the LCD glass panel and conveyor was constructed and its validity was verified by experiments. To minimize the air consumption, the conveyor dimensions were optimized, and the air consumptions between the air conveyors with the air slit and that with the porous pad were compared.

• Korean Journal of Computational Design and Engineering
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• v.13 no.1
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• pp.45-57
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• 2008

A submarine good military weapon because of its confidentiality and intimidating power. Therefore, training warfighters how to maneuver submarine is very important. Because submarine is very expensive and has regional and temporal limitations, M&S(Modeling and Simulation) can be a good alternative. However, as the existing M&S systems of submarine generally use expensive commercial software and dedicated hardware, which cause the warfighters to take troubles to visit the secured places, and then to train themselves during limited time slots. Also, many M&S systems have only one-channel display system which reduces the sense of immersiveness. Another problem is that many heterogeneous simulators can hardly be used as an integrated system. To solve these problems, X3D, a platform-independent and open standard graphic file format, is used with the general-purpose PCs. To increase immersiveness, multi-channel display system and a motion chair are used. Finally, HLA/RTI is used to integrate individual components of the simulator. All of these are verified through experiments.

• International Journal of Highway Engineering
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• v.19 no.4
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• pp.1-7
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• 2017

PURPOSES : This study aims to improve complex modeling of multivariable, nonlinear, and overdispersion data with an artificial neural network that has been a problem in the civil and transport sectors. METHODS: Deep learning, which is a technique employing artificial neural networks, was applied for developing a large bus fuel consumption model as a case study. Estimation characteristics and accuracy were compared with the results of conventional multiple regression modeling. RESULTS : The deep learning model remarkably improved estimation accuracy of regression modeling, from R-sq. 18.76% to 72.22%. In addition, it was very flexible in reflecting large variance and complex relationships between dependent and independent variables. CONCLUSIONS : Deep learning could be a new alternative that solves general problems inherent in conventional statistical methods and it is highly promising in planning and optimizing issues in the civil and transport sectors. Extended applications to other fields, such as pavement management, structure safety, operation of intelligent transport systems, and traffic noise estimation are highly recommended.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.431-436
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• 2014

In this paper, temperature change properties on the 210kW-class Interior Permanent Magnet Synchronous Motor (IPMSM) are performed with the cooling performance of a water cooling device through the thermal characteristic analysis of the IPMSM considering a real driving pattern of urban railway vehicles. First, the thermal analysis modeling of 210kW-class IPMSM, which is an alternative to the conventional induction motor, and its water cooling device is conducted. Next, the thermal characteristic analysis of the IPMSM considering a real driving pattern of urban railway vehicles is performed using 2-Dimensional FEM tool. Finally, the calculated characteristic results are analyzed. Consequently, it is confirmed that the internal temperature of the 210kW-class IPMSM may be lowered to about 42~52% by maintaining the coolant flow rate of the water cooling device (Cross sectional shape of the pipe has 220mm width and 10mm height) for 0.2kg/s level.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.3
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• pp.351-359
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• 2010

Bi-fuel system in a spark ignition engine (SIE) is a rising phenomena in today's automobile technology. In a gasoline driven vehicle, alternatively adoption of compressed natural gas (CNG) could be used as a potential substitute to meet the energy requirement and this is possible by some minor changes in the hardware of the existing engine. Gasoline engine is widely used in the passenger cars, light, medium and heavy duty vehicles but the consumption status of the petroleum is decreasing worldwide and at the same time environmental pollution from automobiles is seriously establishes as a threat for every nation in respect to global warming and climate changes. Now-a-days most vehicles operate using CNG for its popularity stems, clean burning properties and cost effective solution compared to other alternative fuels. It refers as a good gaseous fuel because of its high octane number and self ignition temperature. Though the power output is slightly lesser than the gasoline fuel; its thermal efficiency is better than the gasoline for the same SIE. The research paper highlights the reduction of CO, reasonable outcomes of HC emissions with minor increase in $NO_x$ emissions compared with the gasoline fuel to bi-fuel mode in the SIE that meets the emission challenges.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.23-31
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• 1999

The concept models are used for the analysis of joints because they are simple to use and accurate. The modeling parameters of concept models are estimated using the results of experiments performed on the joints. The concept joint models accurately describe the behavior of joints under the loads which are used in the experiments for the estimation of parameters. However, they may not be accurate under the loads which are not used in the experiments. The accuracy can be dependent on the loads which are used in the evaluation of accuracy. In this study, antioptimization is presented to find the worst possible loads, under which the accuracy of concept joint models can be evaluated. The procedure was applied to the accuracy evaluation of concept joint models in an isolated 3-D joint and 2-D joints of a vehicle structure.

• Journal of Microbiology and Biotechnology
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• v.26 no.5
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• pp.953-958
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• 2016

Chitosan-based film-forming gel is regarded as a promising vehicle for topical delivery of antimicrobial agents to skin wounds, since it protects from microbial infection and the cationic polymer itself possesses antibacterial activity. In this study, possible synergistic interaction against common skin pathogens between the cationic polymer and tyrothricin (TRC), a cyclic polypeptide antibiotic, was investigated, by determining the concentration to inhibit 90% of bacterial isolates (MIC). The addition of the polysaccharide to TRC dramatically reduced the MIC values of TRC by 1/33 and 1/4 against both methicillin-resistant and methicillin-susceptible Staphylococcus aureus, respectively. The synergism of TRC and chitosan combination against both strains was demonstrated by the checkerboard method, with a fractional inhibitory concentration index below 0.5. Moreover, co-treatment of TRC and chitosan exhibited antibacterial activity against Pseudomonas aeruginosa, due to the antibacterial activity of chitosan, whereas TRC itself did not inhibit the gram-negative bacterial growth. These findings suggested that the use of chitosan-based film for topical delivery of TRC could be an alternative to improve TRC antimicrobial activity against strains that are abundant in skin wounds.