• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.34-34
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• 2009

The electrical characteristics of tunnel barrier engineered charge trap flash (TBE-CTF) memory with $SiO_2/Si_3N_4/SiO_2/Si$ engineered tunnel barrier, $HfO_2$ charge trap layer and $Al_2O_3$ blocking oxide layer (MAHONOS) were investigated. The energy bad diagram was designed by using the quantum-mechanical tunnel model (QM) and then the CTF memory devices were fabricated. As a result, the best thickness combination of MAHONOS is confirmed. Moreover, not enhanced P/E speed (Program: about $10^6$ times) (Erase: about $10^4$ times) but also enhanced retention and endurance characteristics are represented.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.115-125
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• 2014

We investigate dissociation of diatomic molecules and anions using density functional theory (DFT) and density-corrected density functional theory (DC-DFT). We scan the potential energy curve of CH, NH and NO neutral molecule and its anion with both DFT and DC-DFT (in form of Hartree-Fock DFT, HF-DFT) using various functionals. Using CCSD(T) results as reference, we perform the error decomposition scheme recently proposed by Kim et al. The results show while most neutrals are $functio{\acute{n}}al$ error $domi{\bar{n}}ating$ normal calculations, $CH^-$ and $NO^-$ anions are density-driven error dominating abnormal calculations. In case of $NH^-$, traditional DFT goes to a wrong dissociation limit indicating abnormality, but both HF-DFT and CCSD(T) results need further investigation due to the kinks on the curve.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1247-1251
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• 2016

This study aims to investigate the effect of sampling frequency to the time domain and frequency domain analysis of pulse rate variability (PRV). Typical time domain variables - AVNN, SDNN, SDSD, RMSSD, NN50 count and pNN50 - and frequency domain variables - VLF, LF, HF, LF/HF, Total Power, nLF and nHF - were derived from 7 down-sampled (250 Hz, 100 Hz, 50 Hz, 25 Hz, 20 Hz, 15 Hz, 10 Hz) PRVs and compared with the result of heart rate variability of 10 kHz-sampled electrocardiogram. Result showed that every variable of time domain analysis of PRV was significant at 25 Hz or higher sampling frequency. Also, in frequency domain analysis, every variable of PRV was significant at 15 Hz or higher sampling frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.80-80
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• 2009

Recently, multiferroics have attracted much attention due to their numorous potentials. In this work, we attemped to utilize the multiferroics as an alternative material for ferroelectrics. Ferroelectric materials have been stadied to ferroelectric random access memories, however, some inevitable problems prevent it from inplementation. multiferroics shows a ferroelectricity and has low process temperature $BiFeO_3$(BFO) films have good ferroelectric properties but poor leakage characterization. Thus we tried, in this work, to adopt $HfO_2$ insulating layer for metal-ferroelectric-insulator-semiconductor(MFMIS) structure to surpress to leakage current. $BiFeO_3$(BFO) thin films were fabricared by using a sol-gel method on $HfO_2/Si$ structure. Ferroelectric BFO films on a p-type Si(100)wafer with a $HfO_2$ buffer layer have been fabricated to form a metal-ferroelectric-insulator-semiconductor (MFIS) structure. The $HfO_2$ insulator were deposited by using a sol-gel method. Then, they were carried out a rapid thermal annealing(RTA) furnace at $750\;^{\circ}C$ for 10 min in $N_2$. BFO films on the $HfO_2/Si$ structures were deposited by sol-gel method and they were crystallized rapid thermal annealing in $N_2$ atomsphere at $550\;^{\circ}C$ for 5 min. They were characterized by atomic force microscopy(AFM) and Capacitance-voltage(C-V) curve.

• The Journal of Internal Korean Medicine
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• v.33 no.3
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• pp.284-297
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• 2012

Objectives : This study was performed to investigate characteristic indice of heart rate variability (HRV) according to presence of metabolic syndrome (MS), pattern identification. Methods : We analyzed 167 subjects who participated in a stroke check-up. We classified the subjects into two groups as MS (n=48) and non-MS (n=119) based on NCEP ATP III. First, we investigated pattern identification of all subjects based on Korean Standard Pattern Identifications for Stroke-III. Second, we surveyed significance of HRV indices between MS and non-MS groups. Third, we investigated significance of HRV indices between classified DP of MS and classified DP of non-MS. Fourth, we investigated significance of HRV indices between classified DP of MS and non-MS. Fifth, we investigated significance between components of MS and HRV indices. Results : 1. SDNN, RMS-SD, HF, Ln(HF), and HF (NORM) were significantly lower in the MS than non-MS group. LN (TP), LF/HF were significantly higher in the MS than non-MS. 2. Ln (HF), Ln (TP), and LF/HF were statistically significant in the classified DP of MS group. 3. RMS-SD, and Ln (HF) were significantly lower in the abdominal obesity group than in the non-abdominal obesity group. SDNN, RMS-SD, TP, Ln (TP), VLF, Ln (VLF), and Ln (LF) were significantly lower in the hypertension group than in the non-hypertension group. RMS-SD was significantly lower in the diabetes group than in the non-diabetes group. Mean HRT,LF/HF were significantly higher in the hypertriglyceridemia than non-hypertriglyceridemia group, but Ln (HF), RMS-SD, and HF (NORM) were significantly lower in the hypertriglyceridemia than non-hypertriglyceridemia group. Conclusions : We found a few significant relationships between classified DP of MS and HRV indices. The resluts demonstrate that MS has potentially negative effects on the cardiovascular system, and these effects could be detected by HRV.

• Journal of The Korean Society of Grassland and Forage Science
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• v.33 no.4
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• pp.319-326
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• 2013

In the present study, we investigated the effects of high forage diets on the volume of udder, hormone level in blood, and lactation characteristics in the Holstein dairy cow. We divided into two groups; high forage diet [HF, concentrate: forage=4:6 n=41] and low forage diet [LF, 6:4 n=21]. Five cows were selected from each group based on their age for measuring the udder volume and the serum levels of estradiol and progesterone. Lactation characteristics were compared between HF and LF. The udder volume was 2.5 fold larger in HF at early gestation (p<0.01), but no difference was noted afterward. For the hormone levels, no significant difference was found between the groups. In HF, milk yield was significantly increased and maintained high longer, while somatic cell count was approximately 50% lower. Meanwhile, the milk fat content was significantly lower in HF during early lactating phase (p<0.001), but there was no difference thereafter. For milk protein and solid content, and MUN, no differences were found between the groups during lactation. Our results indicated that feeding high forage diets to dairy cows can increase milk yield and quality without notable changes in the udder volume and hormone level.

• Journal of the Korean institute of surface engineering
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• v.36 no.6
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• pp.480-490
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• 2003

Effects of plasma-nitriding on the pitting corrosion of Fe-30at%Al-5at%Cr alloy containing Ti, Hf, and Zr were investigated using potentiostat in 0.1M HCl. The specimen was casted by the vacuum arc melting. The subsequent homogenization was carried out in Ar gas atmosphere at $1000^{\circ}C$ for 7days and phase stabilizing heat treatment was carried out in Ar gas atmosphere at $500^{\circ}C$ for 5 days. The specimen was nitrided in the $N_2$, and $H_2$, (1:1) mixed gas of $10^{-4}$ torr at $480^{\circ}C$ for 10 hrs. After the corrosion tests, the surface of the tested specimens were observed by the optical microscopy and scanning electron microscopy(SEM). For Fe-30at%Al-5Cr alloy, the addition of Hf has equi-axied structure and addition of Zr showed dendritic structure. For Fe-30at%Al-5Cr alloy containing Ti, plasma nitriding proved beneficial to decrease the pitting corrosion attack by increasing pitting potential due to formation of TiN film. Addition of Hf and Zr resulted in a higher activation current density and also a lower pitting potential. These results indicated the role of dendritic structure in decreasing the pitting corrosion resistance of Fe-30Al-5Cr alloy. Ti addition to Fe-30Al-5Cr decreased the number and size of pits. In the case of Zr and Hf addition, the pits nucleated remarkably at dendritic branches.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.519-523
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• 1995

The Fe-TM-C-N nanocrystalline films (TM : Hf, Zr and Nb) are investigated to examine the relation between microstructure and soft magnetic properties. In these films, as the atomic radius of TM element increases, $P_{N2}$ which was added to get good soft magnetic properties was decreased and the maximum value of the permeability shifted to the high Fe range in the composition diagram. The best soft magnetic properties achieved in these films are : Hc of 0.15 Oe, $\mu_{eff}$ of 7800 (1MHz) and $4{\pi}M_{s}$ of 17.5 kG in Fe-Hf-C-N film ; Hc of 0.06 Oe, $\mu_{eff}$ of 2750 (1MHz) and $4{\pi}M_{s}$ of 16.8 kG in Fe-Zr-C-N film and Hc of 0.31 Oe; $\mu_{eff}$ of 2100 (1MHz) and $4{\pi}M_{s}$ of 15.5 kG in Fe-Nb-C-N film. It was considered that the stronger the bonding force between TM and C(N), the finer TM(C,N) phase is precipitated and therefore, the finer $\alpha$-Fe grains are formed. The effective permeability of the Fe-Zr-C-N films and Fe-Nb-C-N films remains nearly constant up to 10 MHz.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.313-319
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• 2022

AlGaN/GaN based HfO₂ MOSHEMT (metal oxide semiconductor high electron transistor) with different gate recess depth was simulate to demonstrate a successful normally-off operation of the transistor. Three types of the HEMT structures including a conventional HEMT, a gate-recessed HEMT with 3 nm thick AlGaN layer, and MIS-HEMT without AlGaN layer in the gate region. The conventional HEMT showed a normally-on characteristics with a drain current of 0.35 A at V_G = 0 V and V_DS = 15 V. The recessed HEMT with 3 nm AlGaN layer exhibited a decreased drain current of 0.15 A under the same bias condition due to the decrease of electron concentration in 2DEG (2-dimensional electron gas) channel. For the last HEMT structure, distinctive normally- off behavior of the transistor was observed, and the turn-on voltage was shifted to 0 V.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.05a
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• pp.136-140
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• 2001

본 연구는 절전기능과 인체순응을 고려하여 개발된 에어컨의 쾌적기류를 평가하기 위해 기존 에어컨에 활용되어지고 있는 정속풍, 변동풍과 새롭게 적용되고 잇는 개발풍을 비교하고자 수행하였다. 20명의 남녀 피험자를 대상으로 심전도를 측정하고 HRV 분석을 실시하여 남녀별로 비교한 결과 남녀 모두 개발풍, 변동풍, 정속풍의 순서로 HF/LF 값이 높게 나타났으며, 여성의 경우 정속풍은 무자극 조건에서보다 낮은 HF/LF 값을 나타내었다. 그리고 무자극에 대해서는 여성의 경우보다 남성의 경우가 변동풍과 개발풍의 기류제어 조건에서 크게 반응하였다. 남녀모두를 평균한 기류자극별 비교분석에서는 개발풍에서 가장 높은 HF/LF 값을 보였으며, 개발풍과 변동풍이 정속풍에 대하여 유의미한 차이를 나타내었다. 개인별로 각 자극에 대한 HF/LF 값을 계산하열 각 조건들에 대한 선호도를 조사한 결과, 14명이 개발풍에서 가장 높은 HF/LF 값을 나타내었고, 6명의 피험자는 변동풍에서 가장 높은 HF/LF 값을 보였다. 본 연구의 결과 새롭게 제시된 개발풍이 기존의 정속풍이나 변동풍에 대하여 더욱 쾌적한 기류임을 알 수 있었다.