• Journal of Korean Society for Quality Management
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• v.46 no.3
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• pp.411-424
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• 2018

Purpose: The purpose of this study is to improve submarine TACM launcher system safety device performance. Methods: In this study, EPLD(Electrically Programmable Logic Device) control and time sharing method to the safety device actuator motor and discrete signal processor in launch control panel were used to resolve unusual performance of safety system. Results: The result of this study are as follows; First, sporadic stopping of safety device actuator motor due to insufficient In-Rush current was resolved. Second, repeat of safety device condition as lock & release due to chattering for motor activating was resolved. Third, simultaneous release function for safety device actuator was available. Conclusion: The unusual performance of function for submarine TACM launcher system was overcame by applying EPLD control and time sharing method. The suggestions were proved by performance test in the pressure chamber. The results of this study enhanced survivability of ${\bigcirc}{\bigcirc}{\bigcirc}$ class submarine from enemy torpedo.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.2
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• pp.128-137
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• 2012

This paper deals with the local scour around a pipeline exposed to combined waves and current in the shallow water zone. To investigate the characteristics of the scour around a pipeline on the sea bed, experiments were performed according to the various pipe diameters, wave periods, wave heights, and current velocities. Wave generator and current generator were used for the experiments. Two current directions were used ; co-direction and counter direction to the waves. With the experimental results, the correlations between the scour depths and non-dimensional parameters such as Keulegan-Carpenter number(KC), Froude number(Fr), Ursell number(Ur) and velocity ratio were analysed. The relative scour depths were found obviously to be dominated by the wave component when the velocity ratio function approaches zero and those are gorverned by the current component when the velocity ratio approaches unity. Velocity ratio function was approved to be a proper parameter which is able to express the change of the scour in the combined wave and current zone. Also considering the orbital velocity and the current velocity into Fr numer and KC number respectively, scour depths show more favorable correlationship with the parameters.

• Plant Journal
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• v.12 no.2
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• pp.24-30
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• 2016

The membrane separation processes have received attention due to advantages such as compactness, modularity, ease of installation, flexibility of operation, lower capital cost and lower energy consumption. In this study, we evaluated accuracy of cross-flow, co-current and counter-current models. With the most accurate model, we identified the operating conditions of the two-stage membrane separation and examined the effects of permeance and selectivity of the membrane by simulation. Futhermore, power requirements and operating cost savings due to the introduction of the heat exchanger were investigated by applying heat exchanger network synthesis technique in the two-stage membrane separation using vapor sweep.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.5
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• pp.368-377
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• 2011

A package type of SCR (selective catalytic reduction) system that was proposed for removing the $NO_x$ found in flue gas from the small scale of air pollution sources was evaluated. The efficiency of the SCR system is determined by the proper utilization of catalytic media installed inside of the system, and the proper distribution of flow velocity and $NH_3$ concentration in the flue gas is a crucial factor for using the catalytic media. In this study, the distributions of $NH_3$ concentration were estimated under the various arrays and shapes of AIG at the given gas flow condition. The value of RMS (%) in $NH_3$ concentration is 95.3% at co-current flow (at $0^{\circ}$) injection but it is 90.1% at the condition of counter-current flow (at $120^{\circ}$) condition, which implies the counter-current injection is more favorable. By rearranging the $NH_3$ injection flow rates based on the distribution of velocity and $NH_3$ distribution in basic calculation, the value of RMS (%) in $NH_3$ concentration was reduced to 62.8%. The enhanced effect of $NH_3$ mixing by the combined effect of arrays and shapes are complied in the study.

• Macromolecular Research
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• v.17 no.12
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• pp.963-968
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• 2009

Liquid crystal (LC; E7 and/or ML-0249)-embedded, poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based, polymer electrolytes were prepared for use in dye-sensitized solar cells (DSSCs). The electrolytes contained 1-methyl-3-propylimidazolium iodide (PMII), tetrabutylammonium iodide (TBAI), and iodine ($I_2$), which participate in the $I_3^-/I^-$ redox couple. The incorporation of photochemically stable PVdF-co-HFP in the DSSCs created a stable polymer electrolyte that resisted leakage and volatilization. DSSCs, with liquid crystal(LC)-embedded PVdF-co-HFP-based polymer electrolytes between the amphiphilic ruthenium dye N719 absorbed to the nanocrystalline $TiO_2$ photoanode and the Pt counter electrode, were fabricated. These DSSCs displayed enhanced redox couple reduction and reduced charge recombination in comparison to that fabricated from the conventional PVdF-co-HFP-based polymer electrolyte. The behavior of the polymer electrolyte was improved by the addition of optimized amounts of plasticizers, such as ethylene carbonate (EC) and propylene carbonate (PC). The significantly increased short-circuit current density ($J_{sc}$, $14.60\;mA/cm^2$) and open-circuit voltage ($V_{oc}$, 0.68 V) of these DSSCs led to a high power conversion efficiency (PCE) of 6.42% and a fill factor of 0.65 under a standard light intensity of $100\;mW/cm^2$ irradiation of AM 1.5 sunlight. A DSSC fabricated by using E7-embedded PVdF-co-HFP-based polymer electrolyte exhibited a maximum incident photon-to-current conversion efficiency (IPCE) of 50%.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.214-216
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• 2001

In this paper, we developed the on-line Diagnostic & Monitoring system of distribution transformers using wireless communication. The Diagnostic system consists of the top oil temperature sensing, ambient temperature sensing. load current sensing, acoustic emission peak-value sensing, acoustic emission pulse counter and wireless communication part. The Monitoring system consists of the communication setting, online monitoring and database construction part. The Diagnostic system send the date acquired from the some sensors of the distribution transformers to the host PC. The Monitoring program of the host PC store the data to database. And the Monitoring system estimates the loss of life from the DB. Thus it could be managed the career and the functional lifetime of the transformer more efficiently than existing methodologies.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.5
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• pp.401-412
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• 2013

The paper is to study on the simulation of the micro/macroscale thermo-electrochemical model of a single cell of anode-supported SOFC with direct internal reforming. The coupled heat and mass transport, electrochemical and reforming reactions, and fluid flow were simultaneously simulated based on mass, energy, charge conservation. The micro/macroscale model first calculates the detailed electrochemical and direct internal reforming processes in porous electrodes based on the comprehensive microscale model and then solve the macroscale processes such as heat and mass transport, and fluid flow in SOFCs with assumption of fully-developed flow in gas channel. The simulation results evaluate the overall performance by analyzing distributions of mole fraction, current density, temperature and microstructural design in co/counter flow configurations.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.69.1-69.1
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• 2019

A series of numerical MHD simulations are performed to investigate the evolution of coronal magnetic fields consisting of two flux ropes and an overlying field. Depending on the directions of the axial current and the axial field, two co-helicity cases and two counter-helicity cases are addressed. In Case 1, in which both the axial currents and the axial fields are parallel, flux rope merging bears a huge flux rope with a large winding number. This flux rope naturally erupts, but the whole evolutionary process is rather slow. In Case 2, in which the axial currents are parallel while the axial fields are antiparallel, a self-closed structure is formed and it drives eruption. In Case 3, in which the axial currents are antiparallel and the axial fields are parallel, each flux rope erupts independently and the presence of the other flux rope does not affect the eruption of one flux rope. In Case 4, in which both the axial currents and the axial fields are antiparallel, interaction of the flux ropes and the overlying field effects a breakout reconnection creating an apple-like CME configuration. Our study tells what kind of eruption mechanisms are involved for different eruption features observed.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.34-38
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• 2014

In Display such as LCD, LED, and AMOLED or semiconductor related industries are required to have static ionizer in order to produce reliable goods since the ionizer can create balanced ion that is delivered to producing goods to minimize electrical damages when manufacturing. However, the most general type of ionization is called, "Corona Discharge" that has a slight chances to generate unequal and unstable amount of each +/- ion to the target object. Then, the ionization performance will drastically decrease and end up with quality deterioration problem. In this research, our objective to resolve the current issue via applying "Coupling Condenser" on each counter electrodes of Corona discharging type ionizer. The result is that the ion balance was maintained the satisfied range that is within +/-100V when we changed the duty ratio of the High Voltage of Pulse AC about 40 ~ 70%. In addition, when levelling the High Voltage of Pulse AC, the ion balance holds the range within +20 ~ 0V. Even though we have tested the same experiment for a year, we have seen the range changes roughly ${\pm}50V$.

• Membrane Journal
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• v.30 no.6
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• pp.443-449
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• 2020

In this study, CO2 separation experiment was performed on a CH4/CO2 mixed gas using a ceramic hollow fiber membrane contactor module (HFMC). In order to fabricate high-durability HFMC, a high-durability hollow fiber membrane was prepared and evaluated. HFMC was fabricated using the prepared hollow fiber membrane, and the experiment used a mixture of CH4/CO2 (30% CO2, CH4 balance) and monoethanolamine (MEA). During HFMC operation, the effect of gas and absorbent pressure on the CO2 removal efficiency was evaluated. The CO2 removal efficiency increased as the gas pressure increased, and the CO2 absorption flux also showed a tendency to increase with the liquid flow rate. In addition, when the CO2 absorption rate was less than 40%, LTS-1, a counter-current form where the absorbent enters from the bottom, has higher CO2 removal performance than LTS-2, a countercurrent form in which the absorbent enters from the top. and when the absorption rate was 40% or higher, LTS-2 had higher performance than LTS-1.