• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.168-172
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• 2014

A new sustain driving method is proposed to improve luminous efficiency by the generation of the self-erasing discharge during a sustain period in AC plasma display panel. As one subfield time in the conventional AC PDP is divided into the reset, address, and sustain period. Among them, as the square sustain waveform is alternately applied to the X and Y electrodes on the front plate during the sustain period, the plasma discharge for displaying the image is continuously produced. Meanwhile, in the conventional driving method, the address waveform applied to the A electrode on the rear plate is only driving during an address period and grounded during a sustain period. In this experiment, the negative pulse is applied to the A electrode at the latter part of the sustain pulse for improving the luminous efficiency producing the self-erasing discharge during the sustain period. The negative pulse on the A electrode can change from the space to the wall charge and induce the additional discharge by the accumulated wall charge when the voltages of three electrodes are grounded. As a result, the luminous efficiency will be measured with changes in the voltage level of the A electrode and the new driving method can be improved to the luminous efficiency about 32 % compared with the conventional driving method.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.1
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• pp.35-42
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• 2022

Visible light communication (VLC) is a method of transmitting data through LED blinking and is vulnerable to eavesdropping because the illumination affects the wide range of area. IEEE standard 802.15.7 defines On-Off Keying (OOK), Variable Pulse Position Modulation (VPPM), and Color Shift Keying (CSK) as modulation. In this paper, we propose an encryption method in VPPM for secure communication. The VPPM uses an encoding method called 4B6B where 16 different outputs are represented with 6-bit. This paper extends the number of outputs to 20, to add complexity while not violating the 4B6B generation conditions. Then each entry in the extended 4B6B table is scrambled using vigenère cipher. The probability of decrypting each 6-bit data is $\frac{1}{20}$. Eavesdropper should perform $\sum\limits_{k=1}^{n}20^k$ number of different trials to decrypt the message if the number of keys is n. The proposed method can be applied to OOK of PHY II and CSK of PHY III. We further discuss the secure encoding that can be used in OOK and CSK without performance degradation.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.157-168
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• 2009

In this paper, a photovoltaic system is designed with a step up chopper and single phase PWM(Pulse Width Modulation) voltage source inverter. Where proposed Synchronous signal and control signal was processed by one-chip microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical voltage and current dropping character. The single phase PWM voltage source the inverter using inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power for ordinary use. It can cause the effect of saving electric power. from 10 to 20[%]. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. In order to enhance the efficiency of photovoltaic cells, photovoltaic positioning system using sensor and microprocessor was design so that the fixed type of photovoltaic cells and photovoltaic positioning system were compared. In result, photovoltaic positioning system can improved 5% than fixed type of photovoltaic cells. In addition, I connected extra power to the system through operating the system voltage and inverter power in a synchronized way by extracting the system voltage so that the phase of the system and the phase of single-phase inverter of PWM voltage type can be synchronized. And, It controlled in order to provide stable pier to the load and the system through maintaining high lurer factor and low output power of harmonics.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.264-272
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• 2012

In this paper, we report THz generation and detection characteristics investigated by InGaAs semiconductor epilayers, as results of a basic study obtained from the InGaAs-based THz transmitter/receiver (Tx/Rx). High-temperature and low-temperature (LT) grown InGaAs epilayers were prepared by the molecular beam epitaxy technique for the characterization of THz generation and detection, respectively, and the surface emission based on the photo-Dember effect was tried for THz generation. THz wave was generated by irradiation of a Ti:Sapphire fs pulse laser (60 ps/83 MHz), and a LT-GaAs Rx was used for the THz detection. The frequency band shown in the spectral amplitudes Fourier-transformed from the measured current signals was ranging in 0.5~2 THz, and the signal currents were exponentially increased with the Tx beam power. The THz detection characteristics of LT-InGaAs were investigated by using an Rx with dipole (5/20 ${\mu}m$) antenna, and the cutoff frequency was ~2 THz.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.556-563
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• 2007

We carried out a laboratory scale experiment about the characteristics of chemically active species produced in hybrid gas-liquid discharges. The electrode configuration which had high voltage electrode in the gas phase and ground electrode in the liquid was utilized while high voltage electrode has been typically positioned in the liquid in other studies. Our electrode was configured in such a way as to increase the energy efficiency of chemical reactions by creating a higher electrical field strength and a narrower pulse width than the typical electrode configuration. The highest ozone concentration was obtained at 45 kV which was the medium value in operating voltages. The decrease of solution conductivity increased the resistance of liquid phase and the electric field strength through the gas phase, so ozone gene-ration rate was enhanced. The increase of voltage promoted the production rate of hydrogen peroxide by increasing the electric field strength. In a lower voltage, the increase of solution conductivity increased the degradation rate of $H_2O_2$, so the $H_2O_2$ generation rate decreased. On the other hand, the effects of UV radiation, shock waves etc. increased the $H_2O_2$ generation rate as the solution conductivity increased. A higher rate of $H_2O_2$ generation can be achieved by mixing argon to oxygen which generates a stronger and more stable discharges.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.139-147
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• 2019

A MANPADS(Man Portable Air Defense System), which tracks infrared energy, is light enough for individuals to carry and can against to a variety of aircraft, making it widely deployed around the world, posing a major threat to aircraft. A flare has been developed as an IRCM(Infrared Countermeasures) that protects the life of friendly aircraft and combatants by deceiving such guided missiles. However, DIRCM, which can overcome the problems of existing IRCM, is being developed mainly in some developed countries, and the need for it has been increasing gradually. This paper modeled first generation IR seeker of AM modulation method, the second generation IR seeker of FM modulation method, and the third generation IR seeker of pulse modulation method among various MANPADS, and modeled the scattering light phenomenon in the seeker when laser beams are investigated in DIRCM. Using this, jamming simulations were performed in various engagement environments of the MANPADS and aircraft equipped with DIRCM, and the miss distance of the guided missiles and aircraft were analyzed. Simulation results show that DIRCM, which irradiates a modulated laser beam with one jamming code, deceives both first, second and third generation MANPADS at 1km and 2km of engagement distance. In particular, the survival rate of aircraft equipped with DIRCM increased when the distance of engagement increased from 1km to 2km, and the survival rate was at least 99% at 2km of engagement distance.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.121-121
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• 2003

The standard protocol for the production of transgenic mouse from ES-injected embryo has to process via chimera producing and several times breeding steps, In contrast, tetraploid-ES cell complementation method allows the immediate generation of targeted murine mutants from genetically modified ES cell clones. The advantage of this advanced technique is a simple and efficient without chimeric intermediates. Recently, this method has been significantly improved through the discovery that ES cells derived from hybrid strains support the development of viable ES mice more efficiently than inbred ES cells do. Therefore, the objective of this study was to generate transgenic mice overexpressing human resistin gene by using tetrapioid-ES cell complementation method. Human resistin gene was amplified from human fetal liver cDNA library by PCR and cloned into pCR 2.1 TOPO T-vector and constructed in pCMV-Tag4C vector. Human resistin mammalian expression plasmid was transfected into D3-GL ES cells by lipofectamine 2000, and then after 8~10 days of transfection, the human resistin-expressing cells were selected with G418. In order to produce tetraploid embryos, blastomeres of diploid embryos at the two-cell stage were fused with two times of electric pulse using 60 V 30 $\mu$sec. (fusion rate : 93.5%) and cultured upto the blastocyst stage (development rate : 94.6%). The 15~20 previously G418-selected ES cells were injected into tetraploid blastocysts, and then transferred into the uterus of E2.5d pseudopregnant recipient mice. To investigate the gestation progress, two El9.5d fetus were recovered by Casarean section and one fetus was confirmed to contain human resistin gene by genomic DNA-PCR. Therefore, this finding demonstrates that tetraploid-ES mouse technology can be considered as a useful tool to produce transgenic mouse for the rapid analysis of gene function in vivo.

• Reproductive and Developmental Biology
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• v.35 no.2
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• pp.191-195
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• 2011

The present study was conducted to examine the reactive oxygen species (ROS) generation levels in porcine parthenogenetic embryos. Porcine in vitro matured oocytes were activated by the combination of electric stimulus and 6-DMAP before in vitro culture. Porcine oocytes and parthenogenetic embryos were stained in 10 ${\mu}M$ dichlorohydrofluorescein diacetate (DCF) or 10 ${\mu}M$ hydroxyphenyl fluorescein (HPF) dye each for 30 min at $39^{\circ}C$. The fluorescent emissions from the samples were recoded as JPEG file and the intensity of fluorescence in oocytes and embryos were analyzed. $H_2O_2$ and $^{\cdot}OH$ radical levels of porcine oocytes were reduced immediately after electric stimulation. However, $H_2O_2$ and $^{\cdot}OH$ radical levels of parthenogenetic embryos were increased with time elapsed after electric stimulation from 0 h to 3 h and after DMAP culture. During in vitro culture, $H_2O_2$ and $^{\cdot}OH$ radical levels were gradually increased from the one-cell stage to the two- and four-cell stages. The result of the present study suggests that the ROS was not increased by electric pulse in porcine embryos. Rather than it seems to be associated with the stage of development and the culture condition.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.162-162
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• 2011

Nanometer-sized noble metals can trap and guide sunlight for enhanced absorption of light based on surface plasmon that is beneficial for generation of hot electron flows. A pulse of high kinetic energy electrons (1-3 eV), or hot electrons, in metals can be generated after surface exposure to external energy, such as in the absorption of light or in exothermic chemical processes. These energetic electrons are not at thermal equilibrium with the metal atoms. It is highly probable that the correlation between hot electron generation and surface plasmon can offer a new guide for energy conversion systems [1-3]. We show that hot electron flow is generated on the modified gold thin film (<10 nm) of metal-semiconductor (TiO2) Schottky diodes by photon absorption, which is amplified by localized surface plasmon resonance. The short-circuit photocurrent obtained with low energy photons (lower than bandgap of TiO2, ~3.1-3.2 eV) is consistent with Fowler's law, confirming the presence of hot electron flows. The morphology of the metal thin film was modified to a connected gold island structure after heating to 120, 160, 200, and 240$^{\circ}C$. These connected island structures exhibit both a significant increase in hot electron flow and a localized surface plasmon with the peak energy at 550-570 nm, which was separately characterized with UV-Vis [4]. The result indicates a strong correlation between the hot electron flow and localized surface plasmon resonance with possible application in hot electron based solar cells and photodetectors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11C
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• pp.1106-1112
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• 2009

The SC-FDMA(single carrier-frequency division multiple access) was recently adopted as the uplink multiple access scheme from 3GPP LTE(3rd Generation Partnership Project Long Tenn Evolution) due to its low PAPR (Peak-to-averaged power ratio). The bandwidth of IFDMA(interleaved FDMA), one of the sub-carrier mapping methods of SC-FDMA, gets narrower as the roll-off factor of RRC(root raised cosine) filter decreases from 1 to 0, whereas its PAPR can increase significantly. In practice, to increase the power efficiency of an amplifier, signals with high PAPR undergo the process of clipping. Clipping of signals may cause regeneration of high-frequency components as well as distortion of signals. The current paper deals with the effect of clipping on the spectrum and BER of IFDMA signals with RRC filters.