• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.45-53
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• 2013

Fuel cell power system is one of the most promising energy source for the alternative energy because it has unique advantages such as high energy density, no power drop during operation, and feasible to make compact size. However, due to very low response time, fuel cell is difficult to correspond to drastic load changes and start-up operation. For solving these problem, fuel cell power system must include energy storage device such as Li-Poly battery or super capacitor. Therefore, bi-directional DC-DC converter must be required for this storage device and fuel cell-PCS control. This paper presents a design and modeling of the bi-directional DC/DC converter. Firstly, we present modeling the boost and buck mode of the bi-directional converter through both PWM switch model and state space averaging technique. Secondly, in order to minimize output ripple and transient response overshoot, we have two identical DC-DC converters interleaved and adopt two-loop voltage-current controller. The proposed bi-directional DC-DC converter's modeling method and control design have been verified with computer simulation and experimentation.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.1
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• pp.129-136
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• 2016

This study was performed to investigate whether an intra-articular injection of transient receptor potential vanilloid 1 (TRPV1) receptor agonist, resiniferatoxin (RTX) would alleviate behavioral signs of arthritic pain in a rat model of osteoarthritis (OA). We also sought to determine the effect of RTX treatment on calcitonin gene-related peptide (CGRP) expression in the spinal cord. Knee joint inflammation was induced by intra-articular injection of monosodium iodoacetate (MIA, $8mg/50{\mu}l$) and weight bearing percentage on right and left hindpaws during walking, paw withdrawal threshold to mechanical stimulation, and paw withdrawal latency to heat were measured to evaluate pain behavior. Intra-articular administration of RTX (0.03, 0.003 and 0.0003%) at 2 weeks after the induction of knee joint inflammation significantly improved reduction of weight bearing on the ipsilateral hindlimb and increased paw withdrawal sensitivity to mechanical and heat stimuli. The reduction of pain behavior persisted for 3~10 days according to each behavioral test. The MIA-induced increase in CGRP immunoreactivity in the spinal cord was decreased by RTX treatment in a dose-dependent manner. The present study demonstrated that a single intra-articular administration of RTX reduced pain behaviors for a relatively long time in an experimental model of OA and could normalize OA-associated changes in peptide expression in the spinal cord.

• Tunnel and Underground Space
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• v.14 no.1
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• pp.16-25
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• 2004

As underground caverns have many advantages such as safety and operation, they can also be used for gas storage purpose. When liquefied gas is stored underground, the cryogenic temperature of the gas affects the stability of the storage cavern. In order to store the liquefied gas successfully, it is essential to estimate the exact temperature distribution of the rock mass around the caverns. The main purpose of this study is the development of theoretical solution to be able to estimate the temperature distribution around storage caverns and the assessment of the solution. In this study, a theoretical solution and a conceptual model for estimating two and three dimensional temperature distribution around the storage caverns are suggested. Based on the multi-dimensional transient heat transfer theory, the theoretical solution is successfully derived by assuming the caverns shape as simplified geometry. In order to assess the theoretical solution, by performing numerical experiments with this multi-dimensional model, the temperature distribution of the theoretical solution is compared with that of numerical analysis. Furthermore, the effects of the caverns size are investigated.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.467-476
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• 1999

This paper analyzed the behavior of fixed-bed catalytic reactor (FBCR) which synthesizing maleic anhydride(MA) from the selective oxidation of n-butane. The behavior of FBCR describing convection-diffusion-reaction mechanism is examined by using two-dimensional pseudohomogeneous plug-flow transient model, with the kinetics of Langmuir-Hinshelwood type. Prediction model is composed by optimum parameter estimation from temperature profile, yield and conversion of single FBCR on operating condition variations of Sharma's pilot-plant experiment. A double FBCR with same yield and conversion for single FBCR generated a $8.96^{\circ}C$ lower hot spot temperature than a single FBCR. We could predict parametric sensitivity according to the variation of possible operating condition (temperature, concentration, volumetric flow of feed reactant and coolant flow rate) of single and double FBCR. Double FBCR showed the behavior of more operating range than single FBCR. Double FBCR with nonuniform activities could assure safety operation condition for the possible variation of operating condition. Also, double FBCR had slightly higher than the single FBCR in conversion and yield.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2007.04a
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• pp.147-153
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• 2007

Central to developing new treatment strategies for late onset sporadic Parkinson's disease (PD) and early onset familial PD is resolving the enigma of the specific vulnerability exhibited by substantia nigra dopamine (DA) neurons despite multiple risk factors. Neuropathological evidence from both human and experimental models of PD firmly supports a significant role for oxidative stress (OS) and mitochondrial dysfunction in the death of nigral DA neurons. Largely unknown are the genes underlying selective susceptibility of nigral DA neuron to OS and mitochondrial dysfunction and how they effect nigral DA cell death. To overcome the paucity of nigral DA neurons as well as the dilution effect of non-DA cells in brain tissues, we have developed wild type DA cell line model, SN4741 and mutant DJ-1 (-/-) DA cells, appropriate for microarray analysis and differential mitochondrial proteomics. Mutations in the DJ-1 gene (PARK7), localized in cytoplasm and mitochondria, cause autosomal recessive early onset PD. Through microarray analysis using SN4741 cells followed by validation tests, we have identified a novel phylogenically conserved neuroprotective gene, Oxi-a, which is specifically expressed in DA neurons. The knockdown of the gene dramatically increased vulnerability to as. Importantly as down-regulated the expression level of the gene and recovery of its expression via transient transfection exerted significant neuroprotection against as insult. We also have identified altered expression of mitochondrial proteins and other familial PD genes in DJ-1 (-/-) mutant cells by differential mitochondrial proteomics. In DJ-1 (-/-) cells the knockdown of the other familial PD genes (Parkin and PINK1) dramatically increased susceptibility to as. Thus, further functional characterization of the Oxi-$\alpha$ gene family and the mitochondrial alteration in the DJ-1 (-/-) cell model will provide the rationale for the neuroprotective therapy against both sporadic and familial PD.

• Journal of Pharmaceutical Investigation
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• v.36 no.4
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• pp.223-229
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• 2006

[ $PGE_1$ ]-ethyl ester intraurethral solutions were prepared in ethanol/propylene glycol mixture with penetration enhancer and viscosity-enhancing agent. The stability of $PGE_1$-ethyl ester in intraurethral solution was investigated at various temperature. Simultaneous determination of $PGE_1$-ethyl ester and $PGE_1$ was performed using a validated HPLC technique. In pentobarbital anesthetized cats, increase in intracavernous pressure(ICP), increase in penile length and duration of erectile response were determined after intraurethral application of $PGE_1$-ethyl ester solutions. $PGE_1$-ethyl ester solutions, when instilled into the eyes of rabbits, produces no noticeable irritation, or slight transient conjunctival irritation. From these results, ocular irritation of this solutions was judged as practically non-irritating. The stability study indicates that the therapeutically effective content in solution is well maintained for 46 weeks or longer when they are stored at $4^{\circ}C$. After intraurethral application of $PGE_1$-ethyl ester, ICP was increased and penile erection was induced. $PGE_1$-ethyl ester intraurethral solutions for erectile dysfunction could be developed and evaluated by employing feline erection model.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.218-226
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• 2008

A component-scale two-phase analysis code has been developed for a realistic simulation of two-phase flow transients in a light water nuclear reactor component. In the code, a two-fluid three-field model is adopted and the governing equations are solved on an unstructured mesh. For the numerical solution scheme, the semi-implicit method used in the RELAP5 code was selected, which has been proved to be very stable and accurate for most of practical applications. However, some modifications were needed for its application to an unstructured non-staggered grid. This paper presents the modified semi-implicit numerical method for unstructured grid and the preliminary results of the calculations.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.137-145
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• 2009

The steady-state kinetics of the selective catalytic reduction (SCR) of $NO_X$ with $NH_3$ has been investigated over a commercial ${V_2}{O_5}/TiO_2$ catalyst. In order to account for the influence of transport effects the kinetics are coupled with a fully transient two-phase 1D+1D monolith channel model. The Langmuir-Hinshelwood (L-H) mechanism is adopted to describe the steady-state kinetic behavior of the ${V_2}{O_5}/TiO_2$ catalyst. The reaction rate expressions are based on previously reported papers and are modified to fit the experimental data. The steady-state chemical reaction scheme used in the present mathematical model has been validated extensively with experimental data of selective $NO_X$ reduction efficiency for a wide range of inlet conditions such as space velocity, oxygen concentrations, water concentration, and $NO_2/NO$ ratio. The parametric investigations are performed to examine how the $NH_3$ slip from a SCR $DeNO_X$ catalyst and the conversion of $NO_X$ are affected by the reaction temperature, $NH_3/NO_X$ feed ratio, and space velocity for feed gas compositions with $NO_2/NO_X$ ratios of 0 and 0.5.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.139-147
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• 1999

In this paper, we present the new angular velocity pick-off method for DTG (dynamically tuned gyroscope) which is widely used in various inertial navigation systems and motion control systems. In case of the external angular velocity input, the proposed scheme can make a smaller tilt-angle rather than that of conventional PI method in the transient and steady state because it has an additional inner rebalance loop with a mathematical model of the real gyroscope. So, without any mechanical redesign of the DTG, its dynamic range can be enlarged by the proposed method. The theoretical analysis and simulation model of DTG with the proposed scheme are given. Finally, the proposed scheme is verified.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.100-105
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• 2014

To design a submerged floating railway that is safe against underwater explosions, railway behavior must be investigated and clarified. In this paper, shock waves and impulse pressures generated by a charge away from the submerged floating railway are expressed using experimental formulas. The submerged floating railway tethered by mooring lines is modeled as a simply supported beam with elastic springs. Finite element analysis for the beam model subjected to impulse loading is conducted so that the response of the submerged floating railway can be investigated. For design purposes, a simplified analysis method combined with dynamic load factor is proposed for the same model. Maximum deformation and internal forces are calculated and compared with the time dependent analysis results. It is shown that the simplified analysis results show good agreement.