• 한국연소학회지
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• 제22권4호
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• pp.9-18
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• 2017

This paper is to suggest a simple flame model for the analysis of an internal flame of rotary kilns and to present the application cases. Reaction rates in the multi combustion stages of the selected solid fuel were calculated considering the reaction rates with the Arrhenius type equations. In addition, primary and secondary air flow arrangement were considered. As a simple application case, the combustion trends according to the different solid fuels were described. Improved operating conditions as related with the fuel characteristics were shown to be important for the stable combustion characteristics and the performance of the reactors as defined by the exit temperature of the solid materials.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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• pp.181-188
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• 2006

Operation parameters for large scale industrial facility such as iron making plant are carefully selected through elaborate tests and monitoring rather than through a mathematical modeling. One of the recent progresses for better energy utilization in iron ore sintering process is the distribution pattern of fuel inside a macro particle which is formed with fines of iron ore, coke and limestone. Results of model tests which have been used as a basis for the improved operation in the field are introduced and a theoretical modeling study is presented to supplement the experiment-based approach with fundamental arguments of physical modeling, which enables predictive computation beyond the limited region of tests and adjustment. A single fuel particle model along with one-dimensional bed combustion model of solid particles are utilized, and thermal processes of combustion and heat transfer are found to be dominant consideration in the discussions of productivity and energy utilization in the sintering process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.490-496
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• 1995

A four-legged mobile robot can move on the plain terrain with mobility and stability, but if there exist any obstacles on the terrain of the motion direction, it takes extra times for a mobile robot to cross those obstacles and the stability should be considered during motion. The main objevtive is the study of a quadruped which can cross obstacles with better mobility, stability and fuel economy than any other wheeled or tracked vehicles. Vertical step, isolated wall and ditch are the basic obstacles and by understanding those three cases perfectly, a quadruped can move on any mixed rough terrain as 4-legged animal moves. Each leg of a determine the crossing capability in a static analysis. A quadruped can be simplified with links and joints. By applying the research method, a quadruped can determine the control procedures as soon as it receives the terrain informations from scanner and finally can be moved as animals move with mobility and stability.

• 한국항공운항학회지
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• 제23권4호
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• pp.1-5
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• 2015

In this work, a study was conducted to investigate the effect of diaphragm thickness on the regression rate of the hybrid rocket motor. To observe the flow pattern and the recirculation zone, visualizations of combustion chambers with different diaphragm thickness (5mm, 10mm) were performed. It was found that the case with 5 mm thickness had a larger recirculation zone and therefore, had a higher regression rate than the case with 10mm thickness due to the increased residence time and heat transfer toward the fuel surface. Finally, it was concluded that the thickness of diaphragm can be a critical parameter for the enhancement of the regression rate.

• Journal of Welding and Joining
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• 제17권6호
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• pp.38-45
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• 1999

Shielding gas has significant effects on arc stability, metal transfer and weld quality in the gas metal arc welding (GMAW) process. The double gas-shielded MAG(DMAG) and auxiliary gas-shielded MAG (AMAG) torches are investigated for their capability to provide argon-rich gas mixture using small amount of argon gas through the inner and auxiliary nozzles, respectively. Argon composition with the DMAG torch is calculated numerically, and compared with the measured data using the gas chromatogrphy. Gas flow pattern of the DMAG torch is calculated to change from the laminar to turbulent flow when total gas flow rate becomes larger than 4.5 liter/min at room temperature. While argon-rich shielding gas was obtained using both the AMAG and DMAG torches, the AMAG torch provides higher argon composition than the DMAG torch, which demonstrates that argon gas can be utilized more efficiently with the AMAG torch.

• 한국가시화정보학회지
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• 제16권1호
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• pp.61-69
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• 2018

Ion exchange membrane can transfer only cation or anion in electrically conductive fluids. Recent studies have revealed that such selective ion transport can initiate electroconvective instability, resulting vortical fluid motions on the membrane. This so-called electroconvective vortex (a.k.a. electroconvection (EC)) has been in the spotlight for enhancing an ion flux in electrochemical systems. However, EC under shear flow has not been investigated yet, although most related systems operate under pressure-driven flows. In this study, we present the direct visualization platform of EC under shear flow. On the transparent silicone rubber, microscale channels were fabricated between ion exchange membranes, while allowing microscopic visualization of fluid flow and ion concentration changes on the membranes. By using this platform, not only we visualize the existence of EC under shear flow, its unique characteristics are also identified: i) unidirectional vortex pattern, ii) its advection along the shear flow, and iii) shear-sheltering of EC vortices.

• 한국인쇄학회지
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• 제19권1호
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• pp.42-54
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• 2001

The combination of a silicone surfaced plate and high viscosity ink produced a waterless printing system that worked well, but had limitation. The limitation was that this system was restricted to relatively short run lengths. In the waterless printing process, the press tended to heat up rapidly. Heat in turn, broke down the resins in the inks, causing them to become more fluid. When the ink is heated, the viscosity will drop, the ink will become too liquid and the plate will no longer be able to resist it. The ink will adhere to the non-print portions of the plate, and will print as a very fine mist or speckle pattern in the non-image area. On the other hand, when the ink gets too cold, viscosity will increase until ink transfer is impeded. This study carried otu to investigate the effect of temperature variations of the inks on the print quality in waterless lithography and to examine the adaptability of waterless lithography to conventional offset press without cooling system.

• 한국시스템다이내믹스연구
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• 제1권1호
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• pp.29-56
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• 2000

During the past few years, cyberspace and electronic commerce has been expanding throughout the world rapidly. The purpose of this paper is to find out policy leverages for boosting up cyberspace and electronic commerce using system dynamics simulation modeling approach. The system dynamics simulation model developed in this paper allows analysis of both the effect of factors on dynamic growth pattern of cyberspace as well as the effect of time delay in information processing, money transfer and delivery on model behavior. Finding of this study is that capacity of information infrastructure and size of cyberspace population are key factors of cyberspace growth. Also, reducing time delay in information flow, money flow, and delivery flow is an important policy leverages for growth of electronic commerce.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.14-23
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• 2008

Today the Seoul metro has become the most important public transportation since opening in 1974. However, planning and design of stations, transfer systems and facilities are discorded by different companies and subway lines. Therefore, there is lack of objective design guidelines to secure legibility and safety in subway space. In this context, we aim to investigate the objective design and planing guidelines in terms of people's cognition and space use pattern. Space syntax method which enables scientific analysis is utilized to examine spatial layout considering passenger's spatial behavior. The research resulted in providing objective design and planning standards.

• Corrosion Science and Technology
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• 제11권3호
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• pp.71-76
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• 2012

Computational fluid dynamics (CFD) is nowadays a powerful and reliable tool for simulating different flow processes and temperature. CFD is used to analyze the various pot geometries and operative variables in 55% Al-Zn pot of CGL. In this research, different strip velocities were assumed and then shown the flow pattern in the pot that was similar in the different strip velocities. Temperature distribution in the pot depended on inductors and inlet strip temperature at the steady condition. Generation of dross particles and transport models were considered to describe dross particles evolution inside the pot. In order to observe dross influence by scrap location, dross particles were generated upon the sink roll. Floating time of dross particles is different by scraper locations above the sink roll.