• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.85-90
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• 2012

A 40-MS/sec 10-bit pipelined analog to digital converter (ADC) with a 1.2 Vpp differential input signal is proposed. The implemented pipelined ADC consists of eight stages of 1.5 bit/stage, one stage of 2 bit/stage, a digital error correction block, band-gap reference circuit & reference driver, and clock generator. The 1.5 bit/stage consists of a sub-ADC, digital to analog (DAC), and gain stage, and the 2.0 bit/stage consists of only a 2-bit sub-ADC. A bootstrapped switch with a constant resistance is proposed to improve the linearity of the input switch. It reduces the maximum VGS variation of the conventional bootstrapped switch by 67%. The proposed bootstrapped switch is used in the first 1.5 bit/stage instead of a sample-hold amplifier (SHA). This results in the reduction of the hardware and power consumption. It also increases the input bandwidth and dynamic performance. A reference voltage for the ADC is driven by using an on-chip reference driver without an external reference. A digital error correction with a redundancy is also used to compensate for analog noise such as an input offset voltage of a comparator and a gain error of a gain stage. The proposed pipelined ADC is implemented by using a 0.18-${\mu}m$ 1- poly 5-metal CMOS process with a 1.8 V supply. The total area including a power decoupling capacitor and the power consumption are 0.95 $mm^2$ and 51.5 mW, respectively. The signal-to-noise and distortion ratio (SNDR) is 56.15 dB at the Nyquist frequency, resulting in an effective number of bits (ENOB) of 9.03 bits.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.8
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• pp.1169-1175
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• 1993

Plasma spraying method was used to fabricated the microwave absorbing ferrite-silicon carbide on the aluminum-alloy of the fuselage of an aircraft to protect it from RADAR detection. In this paper 15[rm] instead of 34[rm], the mean size of SIC-powder for ferrite-silicon carbide surface films(I) was used. 50(Kg/h) Instead of 70(Kg/h), the powder feed and 100[mm] Instead of 80(mm), spray distance of spray parameters was used. This M/W absorbers were designed experimentally and fabricated trially, as a result of which the relative frequency bandwidth of 2.8% were obtained under the tolerance limits of the reflection coefficients lower than-10[dB], and the maximum absorption thickness becomes 0.5[mm], which is much thinner than that of the conventional ones.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.66.2-66.2
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• 2017

The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administrative (NASA) and install it on the International Space Station (ISS). The coronagraph is an externally occulted one stage coronagraph with a field of view from 2.5 to 15 solar radii. The observation wavelength is approximately 400 nm where strong Fraunhofer absorption lines from the photosphere are scattered by coronal electrons. Photometric filter observation around this band enables the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with the high time cadence (< 12 min) of corona images to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in 2017 August for the filter system and to perform a stratospheric balloon experiment in 2019 for the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g. coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.420-423
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• 2003

[ $TiO_2$ ] thin films were fabricated by DC magnetron sputtering system at by controlling deposition times, ratios of $Ar:O_2$ partial presser ratio and substrate conditions. And the surface, cross-section morphology, microstructure, and composition ratio of the films were analyzed by FE-SEM, TEM and XPS. Besides, the optical absorption and transmittance of the $TiO_2$ films were measured by a UV-VIS-NIR Spectrophotometer, and photocatalytic properties were studied by G C Analyzer & Data Analysis system. As the result, when $TiO_2$ thin film was made at deposition time of 120[min] and $Ar:O_2$ ratio of 60:40, the best structural and optical properties among many thin films could be accepted. The best results of properties were as follows: thickness; $360{\sim}370[nm]$, grain size; 40[m], gap between two peak binding energy, $5.8{\pm}0.05[eV]$ ($2p_{3/2}$ peak and $2p_{1/2}$ peak of Ti was show at $458.3{\pm}0.05[eV]$ and $464.1{\pm}0.05[eV]$ respectively), binding energy; $530{\pm}0.05\;[eV]$, opticalenergy band gap; 3.4[eV].

• Journal of The Korean Astronomical Society
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• v.50 no.5
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• pp.139-149
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• 2017

The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400 nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence (<12 min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.

• Advances in nano research
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• v.12 no.2
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• pp.213-221
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• 2022

Silicon carbide (SiC) is a binary carbon-silicon compound. In its two-dimensional form, monolayer SiC is composed of a monolayer carbon and silicon atoms constructed as a honeycomb lattice. SiC has recently been receiving increasing attention from researchers owing to its intriguing electronic properties. In this present work, SiC nanoribbons (SiCNRs) are modelled and simulated to obtain accurate electronic properties, which can further guide fabrication processes, through bandgap engineering. The primary objective of this work is to obtain the electronic properties of monolayer SiCNRs by applying numerical computation methods using nearest-neighbour tight-binding models. Hamiltonian operator discretization and approximation of plane wave are assumed for the models and simulation by applying the basis function. The computed electronic properties include the band structures and density of states of monolayer SiCNRs of varying width. Furthermore, the properties are compared with those of graphene nanoribbons. The bandgap of ASiCNR as a function of width are also benchmarked with published DFT-GW and DFT-GGA data. Our nearest neighbour tight-binding (NNTB) model predicted data closer to the calculations based on the standard DFT-GGA and underestimated the bandgap values projected from DFT-GW, which takes in account the exchange-correlation energy of many-body effects.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.50.3-51
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• 2021

The progenitor of Type Ia supernovae is largely expected as a close binary system of a carbon/oxygen white dwarf (WD) primary and its secondary non-degenerate (single degenerate; SD) or degenerate companion (double degenerate; DD). Here we present a high-cadence monitoring observation of SN 2021hpr in a spiral galaxy, NGC 3147. SN 2021hpr shows typical characteristics as a normal type Ia supernova from its photometric (Δm₁₅(B)=1.01±0.03, dust free M_B,max=-19.45±0.02) and spectroscopic data. To investigate its progenitor system, we fit the early part of BVRI-band light curve simultaneously with a combined version of ejecta-companion and simple power-law model. As a result, we found a significant feature of an early excess possibly from a 7.63±0.52R_⊙-sized companion at the optimal viewing angle while the fit is not successful at the common viewing angle. No possible red sources brighter than F555W=-7.01 AB mag is detected at the SN location in Hubble Space Telescope (HST) pre-explosion images, excluding massive stars with initial mass of >16M_⊙ as companions. We suggest the progenitor system of SN 2021hpr can be a fairly large companion such as a main sequence, a low mass subgiant, and a helium giant star. In addition, a possibility of the ejecta-Disk Originated Matter (DOM) interaction for the DD scenario considering linearly-rising early flux still remains.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.149-152
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• 2012

$Cu(In,Ga)Se_2$ (CIGS) is one of the most promising photovoltaic materials because of large conversion efficiency which has been achieved with an optimum Ga/(In+Ga) composition in $CuIn_{1-x}Ga_xSe_2$ (X~0.3). The Ga/(In+Ga) content is important to determine band gap, solar cell performances and carrier behaviors at grain boundary (GB). Effects of Ga/(In+Ga) content on physical properties of the CIGS layers have been extensively studied. In previous research, it is reported that GB is not recombination center of CIGS thin-film solar cells. However, GB recombination and electron-hole pair behavior studies are still lacking, especially influence of with different X on CIGS thin-films. We obtained the GB surface potential, local current and I-V characteristic of different X (00.7 while X~0.3 showed higher potential than 100 mV on GBs. Higher potential on GBs appears positive band bending. It can decrease recombination loss because of carrier separation. Therefore, we suggest recombination and electron-hole behaviors at GBs depending on composition of X.

• KSBB Journal
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• v.11 no.5
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• pp.606-612
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• 1996

A specific ammino auid in a mixture can be crystallized inside an ion exchange column when displacer concentration is high enough to concentrate the amino acid in a pure band beyond its solubility limit. Glutamic acid formpd a discrete crystal layer in a cation exchanger column by operating displacement development mode and using a high concentration of displacer NaOH. The glutamic acid crystal formed was eluded from the column with the effluent stream and collected in a fraction collector. When 1.0 M of NaOH was used as a displacer, more than 60% of the loaded glutamic acid was recovered as crystal. The continuous crystallization and dissolution of crystal occurred, resulting in apparent movement of the crystal along the column without clogging or pressure increase. NaOH was proved a better displacer than NaCl because hydroxide ions neutralized hydrogen ions released from the resin and thus reduced the number of hydrogen ion competing with sodium ion for re-adsorption. The displacement development process coupled with crystallization provided higher concentration and recovery of glutamic acrid than conventional chromatography.

• Korean Journal of Weed Science
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• v.14 no.1
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• pp.56-61
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• 1994

The cationic isoperoxidases were isolated from oat root tips which had been grown in treatment with $1{\times}10^{-4}$ M alachlor and purified about 30-fold by treatment with ethylalchol and ion exchange chromatography on DEAF-celluose and CM-sephadex medium. The oat root was found to contain three isoperoxidase. The major activity peak (B) represented 65% of the total isoperoxidase activity. After purification, the major peak of isoperoxidase was purified about 37-fold from the oat root. Analysis of the major peroxidase peak(column fraction 58-78) by SDS revealed a single band which corresponed to a molecular mass of 42.5 kD. In vitro, isoperoxidase activies were inhibited by IAA. Isoperoxidase(50 unit) significantly inhibited 70.2% of cell division in oat root and 54.2% of cell elongation in oat coleoptile as compared with control.