• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.230-234
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• 2006

One of the methods currently being investigated as a possible non-intrusive diagnostic tool for condition monitoring of power transformer and cable is the recovery voltage measurement, which will be improving the ability to detect the content of water concentration and the ageing process in the insulation system and may thus be an indicator of insulation quality and its ageing status. The polarization phenomenon was studied using RVM with oil-paper samples. In order to interpret its mechanism, the Extended Debye model was introduced. With different circuit parameters, various simulation results were gotten. Furthermore, with the test samples of different ageing condition, measurements are accomplished in the lab. On the basis of this experiment as well as theoretical analysis, correlations between polarizations and ageing were analyzed.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.2
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• pp.225-230
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• 2006

This study investigates drying condition when a small fan is added to a operating the free-breathing proton exchange membrane fuel cells (PEMFCs) with dry $H_2$ and Air. Polarization tests were conducted on PEMFCs at cell temperatures between 30 and $50^{\circ}C$ under dry operation. In the results, the cell performance strongly depended on the cell temperature and the cathode gas stoichiometric flow rates. The cell performance increases as cell temperature decreases from 50 to $30^{\circ}C$. In the domain where the stoichiometry of air is quite large, reduction of the concentration overpotential compensated the increased internal resistance due to drying. The maximum performance was obtained at the small air flow rate beyond which flooding occurs. This indicates that the fan should be operated in the stoichiometry domain with a well designed cell structure to avoid flooding.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.806-813
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• 1999

The effect of Post-Weld Heat Treatment(PWHT) of SS400 Steel was investigated with parameters such as micro vickers hardness corrosion potential polarization behaviors galvanic current Al anode generating current Al anode weight loss etc. Hardness of each parts(HAZ, BM, WM)by PWHT is lower than that of each parts by Non Post-Weld Heat Treatment(NPWHT) However hardness of WM of HAZ part was the highest among those three parts and HAZ area were also acted as cathode without any case of heat treatment. Potential difference between each three parts by PWHT was also smaller compared to NPWHT. Therefore it is suggested that Corrosion resistance property is increased by PWHT. However both Al anode generating current and anode weight loss was also decreased by PWHT compared to NPWHT when SS400 steel is cathodically protected by Al anode.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.404-410
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• 1994

The contrast and the brightness of a liquid crystal display panel are expressed in terms of the characteristic parameters of the rotational transformation on the Poincare sphere of the liquid crystal (LC) cell, which is the geometric representation of the electro-optic polarization transmission characteristics of the cell. From these, we show that the contrast and the brightness of the displayed images can be maximized when the rotation angle becomes $180^{\circ}$ for the rotational transformation corresponding to the change of the state of the LC cell from non-select to select state. state.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.1-6
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• 2000

This paper was studied on the crevice corrosion behavior of SS 400 in marine environment. In 0%, 2%, 3.5%, 5% NaCl solution, the aspect of the crevice corrosion and polarization behavior under the crevice corrosion was investigated. And Weight loss rate of SS 400 with crevice and non-crevice was measured according to the NaCl concentration. The main results obtained are as follows : 1) Under crevice corrosion, the corrosion potential become less noble as the concentration of NaCl solution increased. 2) The current density under open circuit potential was high drained as concentration of NaCl solution increased by 3.5% but the concentration increased over 3.5%, the current density was low drained. 3) The weight loss rate of SS400 was increased as concentration of NaCl solution increased by 3.5% but the concentration increased over 3.5%, that of SS400 was decreased.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.3
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• pp.124-131
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• 2015

Hyperpolarization methods are the most emerging techniques in the field of magnetic resonance (MR) researches since they make a contribution to overcoming sensitivity limitation of MR spectroscopy and imaging, leading to new fields of researches, real-time in vivo metabolic/molecular imaging and MR analysis of chemical/biological reactions in non-equilibrium conditions. Make use of enormous signal enrichments, it becomes feasible to investigate various chemical and biochemical systems with low ${\gamma}$ nuclei in real-time. This review deals with the theoretical principals of common hyperpolarization methods and their experimental features. In addition, more detailed theories, mechanisms, and applications of dissolution dynamic nuclear polarization (D-DNP) are discussed.

• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.25-32
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• 2014

The effects of shot peening pressure on electrochemical and surface morphological characteristics of ALBC3 alloy were investigated in this work. The surface hardness of ALBC3 alloy was improved by shot peening process under all shot peening pressures between 2 and 5 bar, and the hight value of surface hardness was observed to be about 420 Hv at 4 bar of the shot peening pressure. The shot peened surface presented very rough surface due to shot ball collision. The result of anodic potentiodynamic polarization in seawater revealed that there is no significant difference between the shot peened and non-shot peened specimen in terms of corrosion characteristics. Therefore, the optimum projection pressure is determined to be 4 bar.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.330-337
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• 1993

Figure '8' type, passively-mode-locked erbium-doped-fiber ring laser was developed, incorporating a nonlinear loop mirror. Transmittance of the loop mirror was found to be dependent on the incident light intensity due to the non-reciprocal nonlinear phase shift, which enables the passive mode locking of the laser. Self-starting of stable mode locking was possible with only controlling the polarization controllers inside the cavity without any help of external perturbation or modulation. The mode-locked output pulse shape was discussed in relation with the transmission characteristics of nonlinear loop mirror.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.484-488
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• 2017

In the present study, domain evolution processes of a near-morphotropic PZT ceramic during poling was studied using vertical piezoresponse force microscopy (PFM). To perform macroscopic poling in bulk polycrystalline PZT, poling was carried out in a stepwise fashion, and PFM scan was performed after unloading the electric field. To identify the crystallographic orientation and planes for the observed non-$180^{\circ}$ domain walls in the PFM images, compatibility theory and electron backscatter diffraction (EBSD) were used in conjunction with PFM. Accurate registration between PFM and the EBSD image quality map was carried out by mapping several grains on the sample surface. A herringbone-like domain pattern consisting of two sets of lamellae was observed; this structure evolved into a single set of lamellae during the stepwise poling process. The mechanism underlying the observed domain evolution process was interpreted as showing that the growth of lamellae is determined by the potential energy associated with polarization and an externally applied electric field.

• Journal of the Korean institute of surface engineering
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• v.36 no.2
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• pp.168-175
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• 2003

The purpose of solder plating on chip external electrode is to provide a proper solderability to chips on PCB's. The quantitative or qualitative analysis of solderability has been performed by destructive methods, reflow or flow. Evidently, the solderability tends to depend on the grain structure which is varied with additives. Research on the feasibility of employing electrochemical techniques to characterize the solderability of electroplated tin - lead, with respect to the additives, was non destructively performed. The deposit morphology and the polarization behavior of electrolytes containing proprietary additives were evaluated to investigate the soldering degradation. The plated panels from synthetic electrolyte were analyzed according to % Sn, plating thickness, deposit appearance, grain structure, solderability and cyclic voltammetry.