• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.16 no.6
• /
• pp.454-464
• /
• 2023

This paper proposes a low-power 8-bit asynchronous SAR ADC with a sampling rate of 1 MS/s for sensor node applications. The ADC uses bootstrapped switches to improve linearity and applies a VCM-based CDAC switching technique to reduce the power consumption and area of the DAC. Conventional synchronous SAR ADCs that operate in synchronization with an external clock suffer from high power consumption due to the use of a clock faster than the sampling rate, which can be overcome by using an asynchronous SAR ADC structure that handles internal comparisons in an asynchronous manner. In addition, the SAR logic is designed using dynamic logic circuits to reduce the large digital power consumption that occurs in low resolution ADC designs. The proposed ADC was simulated in a 180-nm CMOS process, and at a 1.8 V supply voltage and a sampling rate of 1 MS/s, it consumed 46.06 𝜇W of power, achieved an SNDR of 49.76 dB and an ENOB of 7.9738 bits, and obtained a FoM of 183.2 fJ/conv-step. The simulated DNL and INL are +0.186/-0.157 LSB and +0.111/-0.169 LSB.

• Korean Chemical Engineering Research
• /
• v.49 no.5
• /
• pp.664-668
• /
• 2011

Spherical alumina precursors represented by $AlO_xCl_y(OH)_z$, 30~200 nm in particle diameter, were prepared by partial hydrolysis of $AlCl_3$ vapor in a 500 ml reactor. Investigated on the particle morphology and size were the effects of the reaction time, the stirring speed and the reaction temperature. The particle morphology and size was insensitive to the reaction time in the range 20 to 300 s. The variation of the stirring speed from 0 to 300 and 800 rpm showed that the particle size was the largest at 0 rpm. As the temperature was varied from 180 to 190, 200, $140^{\circ}C$, the particle size showed a maximum at $190^{\circ}C$. By calcination of the as-produced particles at $1,200^{\circ}C$ for 6h with a heating rate of $10^{\circ}C$/min, ${\alpha}$-alumina particles 45 nm in surface area equivalent diameter were obtained. The particle shape after calcination turned wormlike due to sintering between neighboring particles. A rapid calcination at $1400^{\circ}C$ for 0.5 h with a higher heating rate of $50^{\circ}C$/min reduced the sintering considerably. An addition of $SiCl_4$ or TMCTS(2,4,6,8-tetramethylcyclosiloxane) to the $AlCl_3$ reduced the sintering effectively in the calcination step; however, peaks of ${\gamma}$ or mullite phase appeared. An addition of $AlF_3$ to the particles obtained from the hydrolysis resulted in a hexagonal disc shaped alumina particles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.179-179
• /
• 2009

This is for the electrical characterization by IDC pattern using BST$(Ba_{0.5}Sr_{0.5}TiO_3)$ thin film. BST materials had been chosen for high frequency applications due to it's high permitivity and tunability. The BST thin films have been deposited on $Al_2O_3$ Substrates by Nd-YAG pulsed laser deposition with a 355nm wavelength at $700\;^{\circ}C$. The post deposition annealing at $750^{\circ}C$ in flowing $O_2$ atmosphere for 1 hours. The capacitance of IDC patterns have been measured from 1 to 10 GHz as a function of electric field ($\pm40$ KV/cm) at room temperature using inter-digital Au electrodes deposited on top of BST. The IDC patterns have three type of fingers number. For the 10 pairs finger was the best capacitance onto $Al_2O_3$ substrate. The capacitance was 0.9pF. Also Dielectric constant was been 351 at 100 mTorr and annealing temperature $750^{\circ}C$ for 1 hour. The loss tangent was been 0.00531.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.2
• /
• pp.173-180
• /
• 2003

Effects of the electric conductivity of particles were studied for the aggregation process of charged particles with a Brownian dynamic simulation in the free molecular regime. A periodic boundary condition was used for the calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered two extreme cases, a perfect conductor and a perfect nonconductor. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. The fractal dimension for the uncharged aggregate was D$_{f}$= 1.761. However, the fractal dimension decreased from 1.694 to 1.360 for the case of the perfect conductor, and from 1.610 to 1.476 for the case of the perfect nonconductor, with the increase of the average number of charges on the primary particle from 0.2 to 0.3. These values were smaller than that of the centered charge case.e.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.86-86
• /
• 1999

본 연구에서는 마이크로파 유전체 소자로서의 응용 및 절연 산화막으로의 응용을 위해 마이크로파 유전체 세라믹으로 사용되어 온 MgTiO3 물질을 펄스 레이저로 박막을 제조하였다. MgTiO3 는 주로 고주파에서 높은 유전율을 갖고 높은 품질계수 (22.000 at 5 GHz) 혹은 낮은 유전손실을 갖으며 유전특성의 온도 안정성이 우수하여 유전체 세라믹 재료로 응용된다. MgTiO3 박막의 성장은 KrF(파장:248nm) 엑시머 레이저를 이용했으며 공정조건으로 박막의 성장온도는 500-75$0^{\circ}C$, 산소 압력은 10-5-200mTorr, 성장 후 냉각시 산소분위기는 200Torr, 레이저 에너지 밀도는 1.5-5J/cm2 등의 조건으로 박막을 성장하였다. MgTiO3 박막을 여러 가지 기판, 즉 Al2O3(r-plane), Si, Pt 위에 성장시켰으며 기판에 따라 에픽텍셜 혹은 다결정 상태를 갖는 ilmenite 구조로 성장되었다. PLD(Pulsed laser deposition)법에 의해 형성된 MgTiO3 박막을 보면, 우선 Al2O3(r-plane) 기판위에 성장된 경우 $700^{\circ}C$에서 에픽텍셜하게 성장하였으며, Si 기판 위에 성장된 경우 $650^{\circ}C$에서부터 (003)면으로 우선 배향된 단일상의 ilmenite 구조가 형성된다. Ptdnl에 성장된 경우 $600^{\circ}C$에서부터 (003)면으로 우선배향성을 가지며 $650^{\circ}C$에서 결정의 안정화를 이루었으나, MgTiO3 박막은 전기적 특성으로 유전특성 및 유전분산 특성 등이 측정 분석되어 MgTiO3 박막의 고주파 유전체로의 응용에 관한 가능성을 토의하였다.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.2
• /
• pp.353-356
• /
• 2014

We fabricated organic photovoltaic (OPV) based on ZnO ripple structure on indium tin oxide as electron-collecting layers and PTB7-F20 as donor polymer. In addition, atomic layer deposition (ALD) was used for preparing additional ZnO layers on rippled ZnO. Addition of 2 nm-thick ALD-ZnO resulted in enhanced initial OPV performance and stability. Based on photoluminescence results, we suggest that ALD-ZnO layers reduced number of surface defect sites on ZnO, which can act as electron-hole recombination center of OPV, and increased resistance of ZnO towards surface defect formation.

• Advances in nano research
• /
• v.8 no.2
• /
• pp.95-102
• /
• 2020

In this work the properties of iron oxide magnetic nanoparticles (MNPs) synthesized by electrochemical method using different water-alcohol proportions and alcohols have been investigated. The syntheses were carried out using 99% iron foils acting electrodes in a 0.04 M NaCl solutions at room temperature applying 22 mAcm^-2 on the working electrode, mostly obtaining magnetite nanoparticles. The impact of the electrolyte in the size of the synthesized MNPs has been evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD), chronopotentiometric studies, and magnetic characterization. The results have shown that nanoparticles can be obtained in the range of 6 to 26 nm depending on the type of alcohol and the proportions in the mixture of water-alcohol. The same trend has been observed for all alcohols. As the proportion of these in the medium increases, the nanoparticles obtained are smaller in size. This trend is maintained until a certain proportion of alcohol: 50% for methanol, and 60% for the rest of alcohols, proportions where obtaining a single phase of magnetite is not favored.

• Proceedings of the Ginseng society Conference
• /
• 1980.09a
• /
• pp.59-69
• /
• 1980

A new HPLC-method for separation and quantitative determination of ginsenosides in Panax ginseng, Panax quinquefolium and in pharmaceutical drug preparations is elaborated. A reversed-phase-system with ${\mu}Bondapak\;C_{18}$ column (3.9 mm $I.D.{\times}30\;cm$) using acetonitrile-water (30:70) 2 ml/min and acetonitrile-water (18:82) 4 ml/min is suitable for the base-line separation of $Rb_1,\;Rb_2,\;Rc,\;Rd,\;Rf,\;Rg_2,\;respectively\;Re,\;Rg_1$ in 30 minutes. The ginsenosides are directly detected at 203 nm (without derivatization) with the LC-55 or LC-75 spectrophotometer (Perkin-Elmer) at $100\%$ transmission. Detection limit is 300 ng at a signal-to-noise ratio of 10:1. The ginsenosides-peak identification is carried out with HPTLC (high performance thin layer chromatography), with MIR-IR (multiple internal reflection-IR-spectros-copy) and with FD-MS (field desorption mass spectrometry). The calibration curve of each ginsenoside has a correlation coefficient very near to 1. Relative standard deviation for quantitative determinations depends upon the amount of ginsenosides and is approximately 1\%$ for ginsenoside contents of 1\%$. This method is adaptable for routine analysis in quality control laboratories.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.183-187
• /
• 2009

The structure of nano-crystalline $MnFe_2O_4$ was determined and refined with electron powder diffraction data employing the Rietveld refinement technique. A nano-crystalline sample (with average crystal size of about 10.9 nm) was characterized by selected area electron diffraction in an energy-filtering transmission electron microscope operated at 120 kV. All reflection intensities were extracted from a digitized image plate using the program ELD and then used in the course of structure refinements employing the program FULLPROF for the Rietveld analysis. The final structure was refined in space group Fd-3m (# 227) with lattice parameters a=8.3413(7) $\AA$. The reliability factors of the refinement are $R_F$=7.98% and $R_B$=3.55%. Comparison of crystallographic data between electron powder diffraction data and reference data resulted in better agreement with ICSD-56121 rather than with ICSD-28517 which assumes an initial structure model.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.223-224
• /
• 2015

We present the results of visual double stars speckle observations from 2013 using a Zeiss Double Refractor 60 cm with visual focal length f = 1,078 cm, and CCD SBIG ST-402 MEA. A Bessel V filter with ${\lambda}=550nm$ was placed in front of the CCD camera to reduce the chromatic aberration of the objective lens. The objects selected for this observation were calibration candidates and program stars with separations ranging from 0.9-6 arc second, and were located in both the northern and southern hemispheres. Seeing at Bosscha Observatory is generally 1-2 arc second, imposing a limit on visual double star separation below which the system cannot be resolved by long exposure imaging (longer than ~50 ms). Speckle interferometry methods are used to resolve double stars with separations below the typical size of seeing effects. A series of images were captured in fast short-time exposures (~50 ms) using a CCD camera. The result of our experiment shows that our system can be used to measure separations of 0.9 arc second (for systems with small ${\Delta}m$) and ${\Delta}m{\approx}3.7$ (for wide systems).