• 한국진공학회지
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• 제8권4A호
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• pp.482-489
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• 1999

AC PDP(P1asma Display Pane1)s use the mixture of inert gases to generate a discharge inside the display pixels. Impurities such as CO, $CO_2$ and OH inside discharge region may deteriorate the characteristics of PDP operation during long life time of PDP. Electro-negative gas such as CO can cause the sustain pulse amplitude to rise by attaching electrons which will play an important role in the earlier stage of the discharge. MgO film is used to protect the dielectric layer in AC PDP, and is in contact with the free space of display pixel where it is filled with the inert gas mixture. So, MgO film can be a main source of impurities. In this experiment, we observed the change of impurity generation of various MgO films which were deposited by different methods, by using QMS. (quadropole mass spectrometer) The main impurites were $H_2$, CO and $CO_2$. And with the comparison of the TPD (temperature programmed desorption) result, it can be understood that impurity gases are generated by sputtering of MgO surface not by outgassing. Deposition method had effects on the characteristics of the impurity generation. The MgO film manufactured by e-beam evaporation generated more amount of impurity gases than the MgO films manufactured by sputtering or ion-plating. And also heat treatment of MgO film after deposition decreased the magnitude of impurity gas generation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1441-1443
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• 1998

In this work, the effects of space charge was analyzed in removal efficiency of pollutant using dielectric barrier discharges. In order to investigate effects of space charge, two dielectrics(XLPE and TR-XLPE) was chosen which are different in space charge distribution. The simultaneously measurement of space charge and discharge current was carried out in XLPE and TR-XLPE with air gap by Pulsed-Electro-Acoustic Method in ac. Also, the removal efficiency is measured by classical ozone generator(von Siemens 1875). From the experimental results, we knew that the space charge distribution affects the discharge patterns. The more space charge is in surface, the quickly discharge initiates and the magnitude of discharge is increased when polarity changes. And these affect the removal efficiency of pollutant.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.292-300
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• 2006

In order to improve energy efficiency in the dilute trichloroethylene removal using the nonthermal plasma process, the barrier discharge treatment combined with manganese dioxide was experimentally studied. Reaction kinetics in this process was studied on the basis of final byproducts distribution. Decomposition efficiency was improved to about $99\;\%$ at the specific energy of 40 J/L with passing through manganese dioxide. C=C ${\pi}$ bond cleavage of TCE substances gave DCAC, which has the single bond of C-C through oxidation reaction during the barrier discharge plasma treatment. Those DCAC were broken easily in the subsequent catalytic reaction due to the weak bonding energy about $3{\sim}4\;eV$ compared with the double bonding energy in TCE molecules. Oxidation byproducts of DCAC and TCAA from TCE decomposition are generated from the barrier discharge plasma treatment and catalytic surface chemical reaction, respectively. Complete oxidation of TCE into COx is required to about 400 J/L, but $CO_2$ selectivity remains about $60\;\%$.

• Progress in Superconductivity
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• 제14권1호
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• pp.60-65
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• 2012

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 35 kWh class SFES module was designed and constructed as part of a 100kWh/1MW class SFES composed of three 35 kWh class SFES modules. The 35 kWh class SFES is composed of a main frame, superconductor bearings, a composite flywheel, a motor/generator, electro-magnetic bearings, and a permanent magnet bearing. The high energy density composite flywheel is levitated by the permanent magnet bearing and superconductor bearings, while being spun by the motor/generator, and the electro-magnetic bearings are activated while passing through the critical speeds. Each of the main components was designed to provide maximum performance within a space-limited compact frame. The 35 kWh class SFES is designed to store 35 kWh, with a 350 kW charge/discharge capacity, in the 8,000 ~ 12,000 rpm operational speed range.

• 한국초전도ㆍ저온공학회논문지
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• 제10권1호
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• pp.15-18
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• 2008

To achieve high transport current without degradation under magnetic field, it is essential to artificially generate the pinning sites at which moving magnetic flux can be pinned. In this work, $ZrO_2$ nanodots were formed on the substrate surface using electro-spray deposition method. On top of the nanodots, the extended and effective pinning centers can be created. The positively charged Zr precursor solution was sprayed out from the needle using the corona discharge phenomena. Then, the sprayed precursor was deposited onto the negatively charged substrate surface followed by the heat treatment under the controlled atmosphere. Using the electrostatic force among the charged particles of precursor, evenly distributed and nano-sized dots were formed on the substrate surface. The size and density of the nanodots were studied by Atomic Force Microscopy. Also discussed are the effect of the deposition time and solution concentration on the size and density of the nanodot and processing variables in electro-spray method for the effective flux pinning centers in the superconducting films.

• 한국기계가공학회지
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• 제10권1호
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• pp.1-7
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• 2011

Micromachining is gaining popularity due to recent advancements in MEMS(Micro Electro Mechanical Systems). Using conventional micromachining, it is relatively difficult to produce moving components in the order of microns. Photolithography for silicon material has high accuracy machining, but it has low aspect ratio. X-ray lithography has ultra high accuracy machining, but it has expensive cost. Micro-EDM(electro discharge machining) has been gaining popularity as a new alternative method to fabricate micro-structures. In this study, Micro-EDM machine is developed available for fabricate micro-structures and two processes such as side cut EDM and milling EDM is proposed. Several sets of experiment results have been performed to study the characteristics of the machining process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.189-192
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• 2003

The Electro-thermal Explosion Coating (EEC) technique is a new surface treatment technology emerged in recent years. It uses an electrical discharge (with very high voltage from 5 to 30 kV or more) to produce a pulse current with large density inside the material to be deposited, the metal wire undergo the heating, melting, vaporization, ionization and explosion processes in a very short time (from tens ns to several hundreds ${\mu}s$), and the melted droplets shoot at the substrate with a very high velocity (3000 - 4500 m/s), so that the coating materials can be deposited on the surface of the substrate. Coatings with nano-size grains or ultra- fine grains can be formed because of rapid solidification (cooling rate up to $10^6-10^9\;k/s$). Surface of the substrate (about $1-5{\mu}m$ in depth) can be melted rapidly and coatings with very high bonding strength can be obtained.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.768-770
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• 2003

In AC PDP, since charges generated by gas discharge are accumulated on the dielectric. The dielectric is a major factor to determine cell capacitance and its memory effect is a play an important role in PDP driving. In this experiment, we have investigated the electro-optical characteristics with dielectric thickness and we have analyzed wall charge and wall voltage by Q-V energy diagram. The dielectric thickness was varied from 20 um to 50 um. As results, according to the dielectric thickness increase,cell capacitance and power consumption is reduced.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.8-13
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• 1996

A relatively new non-traditional finishing process called Abrasive Flow Machining(AFM) is being used to deburr, polish and radius workpiece or produce compressive residual stresses by flowing an abrasive-laden viscoelastic compound across the surface to be machined. This paper presents the effects of AFM on surfaces of tool steel produced by EDM and W-EDM. Using AFM, white layer produced by EDM is erased almost equally and the amount of metal removal is significantly affected the initally machined surface condition of workpiece. The dimension of workiece is enlarged and its surface roughness is improved as AFM time is increased. The optimal AFM time can be established from the experimental results. It is considered that the grinding method lide AFM is useful to grind complex or slim geometry of workpiece even. Scanning Electron Microscopy(SEM) was used to study the surface characteristics of the workpiece before and after AFM.

• 한국수소및신에너지학회논문집
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• 제14권3호
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• pp.195-206
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• 2003

Polymer electrolyte membrane fuel cells(PEMFC) are very interesting power source due to high power density, simple construction and operation at low temperature. But they have problems such as high cost, improvement of performance and effect of temperature. This problems can be approached using mathematical models which are useful tools for analysis and optimization of fuel cell performance and for heat and water management, in this paper, transient model consists of various energy terms associated with fuel cell operation using the mass and energy balance equation. And water transfer in the membrane is composed of back diffusion and electro-osmotic drag. The temperature calculated by transient model approximately agreed with the temperature measured by experiment in constant current condition.