• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.31-34
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• 2006

The characteristic of carbon nano fiber (CNF) as electron emitters was described. Carbon nano fiber (CNF) of herringbone was prepared by thermal chemical vapor deposition(CVD), mixed with binders and conductive materials, and then were formed by screen-printing process. In order to increase effectively field emissions, the surface treatment of rubbing & peel-off was applied to the printed CNF emitters on cathode electrode. The measurements of field emission properties were carried out by using a diode structure inline vacuum chamber. CNF of herringbone type showed good emission properties that a turn on field was as low as $2.5V/{\mu}m$ and current density was as large as $0.15mA/cm^2$ of $4.5V/{\mu}m$ with electric field. After the vacuum packaged panel of 5-inch in diagonal, the measured white brightness was as high as $7000cd/m^2$ at 1900V of anode and 700V of gate voltage.

• KIEE International Transactions on Power Engineering
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• v.3A no.3
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• pp.148-154
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• 2003

This paper describes the development of KEPCO's 80MVA UPFC electromagnetic transient model and the analysis of its performance in the actual Korean power system. KEPCO's 80MVA UPFC is currently undergoing installation and will be ready for commercial operation from the year 2003. In order to apply a new FACTS device such as the UPFC to the actual power system, the utility needs, in advance, both load flow stability studies and transient studies. Therefore, KEPRI, the research institute of KEPCO, developed a detailed transient analysis model that is based on the actual UPFC S/W algorithm and H/W specifications. This simulation model is implemented by an EMTDC/PSCAD package. The results of the simulation show the effectiveness of UPFC operation in the KEPCO power system.

• Journal of Power Electronics
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• v.13 no.4
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• pp.592-599
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• 2013

This paper investigates a new isolated single-phase AC-DC converter, which integrates a modified AC-DC buck-boost converter with a DC-DC forward converter. The front semi-stage is operated in discontinuous conduction mode (DCM) to achieve an almost unity power factor and a low total harmonic distortion of the input current. The rear semi-stage is used for step-down voltage conversion and electrical isolation. The front semi-stage uses a coupled inductor with the same winding-turn in the primary and secondary sides, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. The discharging time can be shortened. In other words, the duty ratio can be extended. This semi-stage can be operated in a larger duty-ratio range than the conventional AC-DC buck-boost converter for DCM operation. Therefore, the proposed converter is suitable for universal input voltage (90~264 $V_{rms}$) and a wide output-power range. Moreover, the voltage stress on the DC-link capacitor is low. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.4
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• pp.19-27
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• 1997

This paper has described about principle and form of proposed circuit made use of soft switching technology ZVS(Zero Voltage Switching) to reduce turn on and off loss at switching. Also, the analysis of the proposed circuit has described generally by using normalized parameter and operating characteristics have been evaluated as to switching frequency and parameters. Based on the characteristics value, a method of the circuit design is proposed. In addition, this paper proves the propriety of theoretical analysis in terms of the experimental waveforms. In the future, this proposed inverter shows that it can be practically used as power source system for induction cooker etc.

• Korean Institute of Interior Design Journal
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• v.24 no.5
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• pp.99-107
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• 2015

The purpose of this study is to analyze the change of visual stimulus of users to the space through the experiment of EEG and the satisfaction of users depends on the lighting. To do that, the results measured with EEG experiment focusing on Beta ${\beta}$ were compared to each other to figure out difference in the changes of the activation of human brain on lighting's situation as the lighting off and on in the same space. The difference in the results was verified according to the characteristic of users which classified with 4 types of the spatial sensitivities. The results of this study are as following. Firstly, the spacial sensitivity of user is to communicate well with the different senses with stimulus through interaction among the elements. At this time, the brain plays a major role in build the spacial sensitivity of users as the place to make form. Secondly, there are the differences in the activation of brain depends on lighting situation even in the same space. The stimulus into the brain became generally stronger in images with lighting on than off. Especially, the response in the occipital lobe which connected with the visual center turn out strongly in the image of 'modern natural'. Because the visual stimulus interact well with the bright color, the reflectional texture and the rough texture painted the dark color. Thirdly, the satisfaction of users changed with lighting in the space. But we could know that the satisfaction of users isn't be related to the visual stimulus through the results of this study. Finally, there isn't the difference in the activation degree of brain according to the characteristic which are preference of users into 4 types of the spatial sensitivity through the results came from ANCOVA(analysis of covariance) with SPSS Program 22.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.5
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• pp.477-486
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• 2005

In this study, indoor thermal environment, resident behavior of operating cooling device, and thermal comfort vote are investigated at the living room of apartment during summertime in Seoul. Based on the results of the investigation, indoor air temperatures that residents turn air conditioners (especially for cooling load in this research) on and off were found out. The relationships between outdoor weather condition and the number of days using air conditioner, and whether operating patterns of the devices were also found out. The acceptable thermal comfort zone is figured out from these results, and this research is expected to contribute to the development of household air conditioner. The results can be summarized as the followings; Residents turned the air conditioner on at $29.76^{\circ}C$ of indoor air temperature, and $28.89^{\circ}C$ of $SET^\ast$. And turned the air conditioner off at $27.31^{\circ}C$ of indoor air temperature, and $23.70^{\circ}C$ $SET^\ast$. Therefore, acceptable thermal comfort zone could be lied between these temperatures. If comfortable indoor thermal environment can be obtained with various architectural passive cooling techniques based on the results, energy consumption of cooling devices will be reduced.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.263-266
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• 2002

In this paper, It is indicating that an issues of the conventional boost converter for high frequency induction heating. To improve those issues, it is proposed, simulated and analyzed that the current resonant circuit, simulated. As the result, we knew that the proposed circuit has a good point to improve the waveform of input current and to make high efficiency. On the other side, in the inverter for the high current power supply, it is proposed that the high frequency inverter of the half bridge topology, be done the circuit analysis to extract the optimal circuit parameter. It is making sure of the soft switching operating by the inductor to reverse parallel connected on the inverter main switch, decreasing the surge voltage when the switch is turn-off by compulsion, and repressing the switch current and bringing the high current amplitude operation by the multi resonance.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.77-83
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• 2010

In this paper, the noise of HEV(hybrid electric vehicle)-relay module during the turn-on and turnoff switching is experimentally analyzed and an effective method is proposed to reduce the impact noise. First, enclosure methods of 100A relay part with urethane and silicon are tested to find out a better material to isolate the noise. This result shows that the urethane is a better for the noise isolation of relay, so the relays enclosed by urethane are installed in the relay module. Second, the noise of HEV-relay module is analyzed experimentally to identify the noise generation mechanism. From this result, it is found that the vibration transmitted to battery pack through bolt generates the structural borne noise with the frequency band of 200~2000 Hz, which is more serious when the switch is turned off. Finally, the direction of switching and the joint structure are modified in order to isolate the vibration transmitted to battery back. Both methods are very effective to reduce the switching noise.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.2
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• pp.69-74
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• 1999

This paper presents about a example of circuit design and characteristics of proposed circuit in the case of adopted the high frequency resonant Inverter of SEPP type using ZVS(Zero-Voltage-Switching) to the Induction heating load. The soft switching technology known as ZVS is used to reduce turn on and off loss at switching. Also, this paper realizes quantitative circuit analysis which has change the equivalent of Induction heating load to the electric circuit. According to the calculated characteristics value, a method of the circuit designs and operation characteristics of the Inverter is proposed. In addition, this paper proves the propriety of theoretical analysis through the experiment. The proposed inverter shows it can be practically used as power source system for induction heating Jar etc.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.500-505
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• 1997

Experimental amorphous photodiode is fabricated on CMOS IC using a-Si:H p-i-n structure. Amorphous photodiode is scuccessfully integrated on CMOS IC using amorphous Si produced by PECVD system. The PECVD system can deposit a-Si:H at low temperature so that photodiode can be integrated with CMOS IC structure without any process incompatibility. The fabricated amorphous photodiode has a breakdown voltage of below -20 V, a leakage current of about 1 $\mu\textrm{A}$, and turn-on voltage of 0.6~0.8 V. It is demonstrated that the photocurrent of optical signal can be turned on and off by a small voltage and the fabricated amorphous p-i-n photodiode can be used as an optical switch.