• Journal of the Korea Safety Management & Science
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• v.20 no.4
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• pp.7-13
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• 2018

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.

• Journal of Hydrogen and New Energy
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• v.26 no.2
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• pp.179-183
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• 2015

In this study, we propose a catalyst structure including enzyme and metal nano rod for glucose sensing. In the catalyst structure, glucose oxidase (GOx) and gold nano rod (GNR) are alternatingly immobilized on the surface of carbon nanotube (CNT), while poly(ethyleneimine) (PEI) is inserted in between the GOx and GNR to fortify their bonding and give them opposite polarization ($[GOx/GNR]_nPEI/CNT$). To investigate the impact of $[GOx/GNR]_nPEI/CNT$ on glucose sensing, some electrochemical measurements are carried out. Initially, their optimal layer is determined by using cyclic voltammogram and as a result of that, it is proved that $[GOx/GNR/PEI]_2/CNT$ is the best layer. Its glucose sensitivity is $13.315{\mu}AmM^{-1}cm^{-2}$. When it comes to the redox reaction mechanism of flavin adenine dinucleotide (FAD) within $[GOx/GNR/PEI]_2/CNT$, (i) oxygen plays a mediator role in moving electrons and protons generated by glucose oxidation reaction to those for the reduction reaction of FAD and (ii) glucose does not affect the redox reaction of FAD. It is also recognized that the $[GOx/GNR/PEI]_3/CNT$ is limited to the surface reaction and the reaction is quasi-reversible.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.666-669
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• 2008

Droplet in miniaturized microfluidic systems have received much focused attention recently. In this work, electrical charging phenomenon of a conducting water droplet on the electrode under the dc electric field is studied and using this phenomenon droplet actuation method for microreactor applications is experimentally demonstrated. To find effects of key factors, the effects of electric field, medium viscosity, and droplet size are investigated. A scaling law of charging for the conducting droplet is derived from the experimental results. Unlike the case of a perfect conductor, the estimated amount of electrical charge ($Q_{est}$) of a water droplet is proportional to the 1.59 power of the droplet radius (R) and the 1.33 power of the electric field strength (E). (For a spherical perfect conductor, Q is proportional to R2 and E.) It is thought that the differences are mainly due to incomplete charging of a water droplet resulted from the combined effect of electrochemical reaction at electrode and the relatively low conductivity of water. Using this phenomenon, we demonstrate the transport of the charged droplet and fusion of two oppositely-charged droplets. When electric field is subjected sequentially on the electrode, the charged droplet is transported on the electrode. For the visualization of fusion of charged droplets, the precipitation reaction is used. When subjected to a DC voltage, two droplets charged are moving and merging toward each other due to the Coulombic force and chemical reaction is simultaneously occurred by coalescence of droplets. It may be due to the interchange effect of charge. It is shown that the droplet can be used for microreactor where transporting, merging etc. of reagents constitute unit operation.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.1
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• pp.17-35
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• 2016

In this study, the dynamic behaviour of a rotating Timoshenko beam when under the actions of a variable magnitude load moving at non-uniform speed is carried out. The effect of cross-sectional dimension and damping on the flexural motions of the elastic beam was neglected. The coupled second order partial differential equations incorporating the effects of rotary and gyroscopic moment describing the motions of the beam was scrutinized in order to obtain the expression for the dynamic deflection and rotation of the vibrating system using an elegant technique called Galerkin's Method. Analyses of the solutions obtained were carried out and various results were displayed in plotted curve. It was found that the response amplitude of the simply supported beam increases with an increase in the value of the foundation reaction modulus. Effects of other vital structural parameters were also established.

• Steel and Composite Structures
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• v.15 no.1
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• pp.1-14
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• 2013

Predicting the fire resistance of structures has been significantly advanced by full scale fire tests in conjunction with improved understanding of compartmental fire. Despite the progress, application of insulation is still required to parts of structural steelwork to achieve over 60 minutes of fire rating. It is now recognised that uncertainties on insulation properties hinder adaptation of performance based designs for different types of structures. Intumescent coating has recently appeared to be one of most popular insulation types for steel structures, but its design method remains to be confirmed by empirical data, as technical difficulties on the determination of the material properties at elevated temperatures exist. These need to take into account of further physiochemical transitions such as moving boundary and endothermic reaction. The impetus for this research is to investigate the applicability of the conventional differential equation solution which examines the temperature rise on coated steel members by an inorganic intumescent coating, provided that the temperature-dependent thermal/mechanical insulation properties are experimentally defined in lab scale tests.

• International Journal of Control, Automation, and Systems
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• v.4 no.1
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• pp.42-52
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• 2006

In order to utilize hydrodynamic drag force on articulated robots moving in an underwater environment, an optimum motion planning procedure is proposed. The drag force acting on cylindrical underwater arms is modeled and a directional drag measure is defined as a quantitative measure of reaction force in a specific direction in a workspace. A repetitive trajectory planning method is formulated from the general point-to-point trajectory planning method. In order to globally optimize the parameters of repetitive trajectories under inequality constraints, a 2-level optimization scheme is proposed, which adopts the genetic algorithm (GA) as the 1st level optimization and sequential quadratic programming (SQP) as the 2nd level optimization. To verify the validity of the proposed method, optimization examples of periodic motion planning with the simple two-link planner robot are also presented in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.486-489
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• 2003

To reduce lateral force of traditional plunger type piston in the swash plate type hydraulic piston pumps and motors, we have proposed rod type piston with ball joint on both ends. We have studied the theoretical reaction force on two types of piston moving in the cylinder block bore. and made an experiment for the resistance force measurement on a reciprocating motion of plunger and rod type piston, changing the test condition such as swash plate angel and supply oil pressure and so on. As a result. a rod type piston has more smaller resistance force, about 29%. than a plunger type one.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.505-508
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• 2002

An emotionally modeled robot is dealt in this paper. The emotional model is required especially in the entertainment robot. Recently, the entertainment robots have been developed as the next generation of electronic toys. They require several capabilities such as perceiving, acting, communication, and surviving. The owner recognizes the communication with a entertainment robot by observing its expression and reaction. The expression is realized by emotion-based actions based on moving, dancing, sounding, speaking, and lighting. Therefore, we propose an emotional modeling algorithm, using the fuzzy logic system, in this paper. Good performance of the algorithm is confirmed by the result of a simulation.

• Coupled systems mechanics
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• v.1 no.1
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• pp.99-113
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• 2012

We present a monolithic semi-implicit algorithm for solving fluid-structure interaction problem at small structural displacements. The algorithm uses one global mesh for the fluid-structure domain obtained by gluing the fluid and structure meshes which are matching on the interface. The continuity of velocity at the interface is automatically satisfied and the continuity of stress does not appear explicitly in the global weak form due to the action and reaction principle. At each time step, we have to solve a monolithic system of unknowns velocity and pressure defined on the global fluid-structure domain. Numerical results are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.417-420
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• 2005

This paper presents an analytical method to evaluate the dynamic behavior of the scroll compressor. Unbalanced forces and moments act on the compressor body because of the reaction forces acting on rotating components like the orbiting scroll, Oldham coupling ring, and the crank shaft. The vibration of the compressor is induced by the forces and the moments. In this paper, through modeling of the leakage flow, solving the forces from the equations of motion of the moving parts, the analysis of vibration of the compressor was performed. According to the operating condition, the variation of acceleration of the compressor body were calculated and compared.