• The Journal of Korean Physical Therapy
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• v.23 no.6
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• pp.49-53
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• 2011

Purpose: The purpose of this study is to investigate whether dual-hemisphere transcranial direct current stimulation (tDCS) could induce more cortical activity, compared to single-hemisphere, using functional MRI (fMRI). Methods: One right-handed healthy subject was recruited. Three phases of dual-hemisphere tDCS (i.e. anodal tDCS over the left-dominant primary sensoriomotor cortex (SM1) and cathodal tDCS over the right-non dominant SM(1) were consecutively delivered on to a subject, during fMRI scanning. The voxel count and the intensity index in the averaged cortical map were analyzed among the three tDCS phases. Results: Our result showed that cortical activation was observed on all the three phases of the dual-hemisphere tDCS. Voxel count and intensity index were as following; 912 and 4.07 in the first phase, 1102 and 3.90 in the second phase, 1031 and 3.80 in the third phase. Conclusion: This study demonstrated that application of the dual-hemisphere tDCS could induce cortical activity and maintain to recruit cortical neurons. Our findings suggested that application of dual-hemisphere tDCS could produce efficiency of the ongoing tDCS effect to facilitate cortical excitability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.593-602
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• 2016

Numerical simulations on the close-coupled supersonic gas atomizer for metallic powder production were performed in this study. A proper turbulence model was chosen and then VOF(Volume of Fluid) and DPM(Discrete Phase Model) methods were sequentially applied for the simulations of primary and secondary break-up processes of liquid metal. Diameters of parent droplets were calculated by analyzing Level-Set function contour from the VOF result. Finally, the distribution of particle diameter was obtained from the DPM result at exit of the computational domain.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.563-571
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• 2003

In this paper, the control algorithm and control method for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3th harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts may directly influence its compensation characteristics. Hence, the advantage of this control algorithm is direct extraction of compensation voltage reference and the required rating of the series active filter is much smaller than that of a conventional shunt active filter. Some experiments were executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.56-66
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• 1998

The absorption process of water vapor in a liquid film is an important process in LiBr-Water absorption system. The composition of the gas phase, in which a non-absorbable gas is combined with the absorbate, influences the transport characteristics. In the present work, the absorption processes of water vapor into aqueous solutions of lithium bromide in the presence of non-absorbable gas are investigated. The continuity, momentum, energy and diffusion equations for the solution film and gas are formulated in integral forms and solved numerically. It is found that the mass transfer resistance in gas phase increases with the concentration of non-absorbable gas. However the primary resistance to mass transfer is in the liquid phase. As the concentration of non-absorbable gas in the absorbate increases, the interfacial temperature and concentration of absorbate in solution decrease, which results in the reduction of absorption rate. The reduction of mass transfer rate is found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of tube where the non-absorbable gas accumulates. At higher non-absorbable gas concentration, the decrease of absorption rate seems to be linear to the concentration of non-absorbable gas.

• Clean Technology
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• v.18 no.2
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• pp.221-225
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• 2012

In this study, simulation works for a carbon dioxide capture process using solvent absorption method have been performed for decrease of regeneration energy in applying phase transition of liquid solvent. When carbon dioxide is dissolved in 30 wt% MEA solvent, liquid mixture divided into two phase according to mole loading of dissolved carbon dioxide. Using this phenomenon, we can decrease regeneration energy about 61% than primary absorber column-stripper column process.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.210-211
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• 2004

The effect of oscillating on the unsteady laminar flow past a circular cylinder is numerically investigated in the present study. Our study is to analyze the vortex formation behind a circular cylinder for different rotary oscillation conditions. And then we are study to portray the unsteady dynamics of wake flows. We decide lock-on region by observing the phase switching phenomena We classify the vortex formation patterns in the primary lock-on region The present study is to identify the quasi-periodic state around lock-on region. At the boundary between lock-on and non-lock-on the shedding frequency is bifurcated. After the bifurcation, one frequency follow the forcing frequency ($S_f$) and the other returns to the natural shedding frequency ($St_0$). In the quasi-periodic state, the variation of magnitudes and relevant phase changes of $C_L$ with forcing phase are examined.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.53-55
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• 2003

This paper propose a transformer protective relaying algorithm based on the increment of flux linkages (RIFL) of the Primary and secondary windings. The RIFL is equal to the turn ratio for all operating conditions except an internal faults. For a single-phase transformer and three-phase Y-Y transformer, the increments of flux linkages are calculated and their ratios are compared with the turn ratio. For a three-phase Y-$\triangle$ transformer, the difference of the increments of flux linkages are calculated to use the line currents instead of the delta winding currents, which are practically unavailable. Their ratios are compared with the turn ratio. The results of various tests show that the algorithm successfully discriminates internal faults from normal operation conditions such as magnetic inrush and overexcitation. The algorithm can not only detect internal winding faults, but reduce the relay's operating time.

• Journal of Power Electronics
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• v.6 no.1
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• pp.45-51
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• 2006

A new high efficiency phase shifted full bridge (PSFB) converter for the power sustaining module of a plasma display panel (PDP) is proposed in this paper. The proposed converter employs a voltage doubler rectifier without an output inductor. Since it has no output inductor, the voltage stresses of the secondary rectifier diodes can be clamped at the output voltage level. No dissipative resistor-capacitor (RC) snubber for rectifier diodes is needed. Therefore, high efficiency, as well as, a low noise output voltage can be realized. Due to the elimination of the large output inductor, it features a simple structure, lower cost, smaller mass and lighter weight. Furthermore, the proposed converter has wide zero voltage switching (ZVS) ranges with low current stresses of the primary switches. Also the resonance between the leakage inductor of the transformer and the capacitor of the voltage doubler cell reduces the current stresses of the rectifier diodes. In this paper, operational principles, an analysis of the proposed converter and experimental results are presented.

• Journal of Power Electronics
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• v.16 no.3
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• pp.823-831
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• 2016

A high-efficiency method is proposed to suppress magnetic core imbalance in phase-shifted full-bridge (PSFB) converters. Compared with conventional solutions, such as controlling peak current mode (PCM) or adding DC blocking capacitance, the proposed method has several advantages, such as lower power loss and smaller size, because the additional current sensor or blocking capacitor is removed. A time domain model of the secondary side is built to analyze the relationship between transformer core imbalance and cathode voltage of secondary side rectifiers. An approximate control algorithm is designed to achieve asymmetric phase control, which reduces the effects of imbalance. A 60 V/15 A prototype is built to verify the proposed method. Experimental results show that the numerical difference of primary side peak currents between two adjacent cycles is suppressed from 2 A to approximately 0 A. Meanwhile, compared with the PCM solution, the efficiency of the PSFB converter is slightly improved from 93% to 93.2%.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.179-190
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• 2013

A station blackout experiment called SBO-01 was performed at the ATLAS facility. From the SBO-01 test, the station blackout scenario can be characterized into two typical phases: A first phase characterized by decay heat removal through secondary safety valves until the SG dryouts, and a second phase characterized by an energy release through a blowdown of the primary system after the SG dryouts. During the second phase, some physical phenomena of the change over a pressurizer function, i.e., the pressurizer being full before the POSRV $1^{st}$ opening and then its function being taken by the RV, and the termination of normal natural circulation flow were identified. Finally, a core heatup occurred at a low core water level, although under a significant amount of PZR inventory, whose drainage seemed to be hindered owing to the pressurizer function by the RV. The transient of SBO-01 is well reproduced in the calculation using the MARS code.