• 한국컴퓨터정보학회논문지
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• 제24권3호
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• pp.1-9
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• 2019

This paper presents three potential risks in an environment that simultaneously performs the garbage collection and wear leveling in NAND flash memory. These risks may not only disturb the lifespan improvement of NAND flash memory, but also impose an additional overhead of page migrations. In this paper, we analyze the interference of garbage collection and wear leveling and we also provide two theoretical considerations for lifespan prolongation of NAND flash memory. To prove two solutions of three risks, we construct a simulation, based on DiskSim 4.0 and confirm realistic impacts of three risks in NAND flash memory. In experimental results, we found negative impacts of three risks and confirmed the necessity for a coordinator module between garbage collection and wear leveling for reducing the overhead and prolonging the lifespan of NAND flash memory.

• 대한수학회논문집
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• 제34권2호
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• pp.451-464
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• 2019

In the present paper, we find the sharp bound for the fourth coefficient of starlike functions f which are normalized by f(0) = 0 = f'(0) - 1 and satisfy the following two-sided inequality: $$1+{\frac{{\gamma}-{\pi}}{2\;{\sin}\;{\gamma}}}\;<\;{\Re}\{{\frac{zf^{\prime}(z)}{f(z)}}\}\;<\;1+{\frac{{\gamma}}{2\;{\sin}\;{\gamma}}},\;z{\in}{\mathbb{D}}$$, where ${\mathbb{D}}:=\{z{\in}{\mathbb{C}}:{\left|z\right|}<1\}$ is the unit disk and ${\gamma}$ is a real number such that ${\pi}/2{\leq}{\gamma}<{\pi}$. Moreover, the sharp bound for the fifth coefficient of f defined above with ${\gamma}$ in a subset of [${\pi}/2,{\pi}$) also will be found.

• 천문학회보
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• 제46권2호
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• pp.52.1-52.1
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• 2021

Low mass X-ray binary(LMXB) 중 accretion disk가 존재하지 않으며 매우 작은 질량 (1 ≪ M_⊙)의 동반성을 가지는 pulsar binary system에서 중성자별과 동반성의 항성풍은 상호작용하여 intrabinary shock(IBS)을 형성한다. 이곳에서 입자들은 상대론적으로 가속되어 싱크로트론 복사를 방출한다고 생각된다. 이 복사는 X-선 영역으로 관측되며 이때 관측된 X-선 궤도 광도곡선은 IBS의 모양에 따라 달라진다. 우리는 IBS의 X-선 복사 과정을 모델화하여 shock의 모양과 내부의 전자 특성을 파악하고, 광학 관측을 통해 얻은 orbital parameter와 비교하며 binary의 geometry를 보다 정확히 이해하고자 한다. 이 발표에서는 다양한 pulsar binary system의 Chandra, XMM 그리고 NuSTAR의 X-선 관측 데이터에 IBS 모델을 적용해보고 IBS와 binary의 geomerty를 분석한 결과를 제시한다.

• 한국세라믹학회지
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• 제46권4호
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• pp.419-424
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• 2009

Congruent or stoichiometric $LiNbO_3$ fiber single crystals were grown by the $\mu$-PD method, and the grown fiber crystals have the several (2 or 3) ridges with a diameter of $1.35{\sim}1.5\;mm$ and a length of $40{\sim}100\;mm$. In this $\mu$-PD process, different growth rates ($10{\sim}60\;mm/h$) were applied. Pt wire or $LiNbO_3$ crystal was used as a seed. The properties of grown $LiNbO_3$ fiber single crystals having a-axis or c-axis according to seeds were effected by the grown conditions(Pt tube diameter, pulling speed, after heater etc.). Disk-type $LiNbO_3$ samples were poled in condition of DC 5 V/cm at 1050, 1075 or $1100^{\circ}C$. XRD, SEM, conoscope image through the polarized microscope, $T_C$ measuring apparatus, optical transmittance measuring instrument are used to identify the properties of $LiNbO_3$.

• 한국작물학회지
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• 제52권3호
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• pp.303-310
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• 2007

고구마 용도 다양화와 지상부의 채소적 가치를 구명키 위하여, 괴근에서 자라난 싹 중 부드러운 잎과 잎자루를 포함한 줄기끝 10 cm의 끝순을 수확하여, 끝순 추출물의 페놀화합물 함량, 식중독균인 Listeria monocytogenes, Salmonella Typhimurium에 대한 항균 활성, 식품안전성과 관련된 돌연변이원성 및 항돌연변이원성 등을 조사한 결과는 다음과 같다. 1. 고구마 끝순에는 6종의 페놀화합물이 함유되어 있었으며, 그 중 chlorogenic acid와 caffeic acid의 함량이 총페놀함량의 $89{\sim}93%$로 대부분을 차지하였다. 또한 용매분획별 페놀화합물 함량은 ethyl acetate 및 buthyl alcohol 추출물이 다른 용매추출물에 비하여 월등히 높았다. 2. 고구마 끝순의 80% ethanol 조추출물의 수율은 12.5 g이었고, 용매분획별로는 water 분획물이 8.9 g으로 가장 많았으며, 다음은 chloroform 분획물이 1.6 g이었고, 나머지 용매 분획물은 $0.7{\sim}1.1g$의 수율을 나타내었다. 3. 고구마 끝순에는 6종의 페놀화합물이 함유되어 있었으며, 그 중 chlorogenic acid와 caffeic acid의 함량이 총페놀 함량의 $89{\sim}93%$로 대부분을 차지하였다. 또한 용매분획별 페놀화합물 함량은 ethyl acetate 및 buthyl alcohol 추출물이 다른 용매추출물에 비하여 월등히 높았다. 4. Listeria monocytogenes에 ethyl acetate 및 buthyl alcohol 추출물을 첨가한 결과 16시간까지는 3 log 이상 균의 성장을 억제하였으며 특히 20 mg/ml butanol 추출물은 균의 성장을 억제시키다 12시간 이후에는 완전히 균을 사멸시키는 것으로 나타났다. Salmonella Typhimurium에 대해서도 고구마 끝순 추출물은 $0.5{\sim}1$ log 정도의 감소를 나타내었다. 5. 고구마 끝숱 추출물의 Salmonella Typhimurium TA98 및 TA100에 대한 돌연변이 활성을 조사한 결과 TA98은 $29{\sim}33$ CFU/plate이었고, TA100은 $159{\sim}188$ CFU/plate로 돌연변이 활성이 없었다. 6. 직접 돌연변이원 물질인 2-NF와 MMS를 처리하여 복귀돌연변이수를 측정한 결과 ethyl acetate 및 buthyl alcohol에서 돌연변이로 인한 복귀변이원성 집락수가 낮게 나타남으로써 고구마 끝순 추출물이 항돌연변이 활성이 있는 것으로 나타났다.

• 한국전기전자재료학회논문지
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• 제21권12호
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• pp.1077-1082
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• 2008

To fabricate a multi-layered piezoelectrics/electrodes structure, the piezoelectrics should be sintered at the temperature lower than $950^{\circ}C$ to use the silver electrode, which is cheaper than the electrodes containing noble metals such as Pd and Pt. Therefore, in this study, we modified the composition of $Pb(Zr,Ti)O_3$-based material as $(Pb_{0.98}Cd_{0.02})(Ni_{1/3}Nb_{2/3})_{0.25}Zr_{0.35}Ti_{0.4}O_3$ to lower the sintering temperature and to improve the piezoelectric properties. Small amount of $MnCO_3$, $SiO_2$, and $Pb_3O_4$ were also added to lower the sintering temperature of the ceramic. The prepared raw powders were mixed by using a ball mill for 24 hours. And then the mixed powders were calcinated for 2 hours at $800^{\circ}C$. The calcinated powders were again crushed with the ball mill for 72 hours. The final powders were pressed for making the shape of ${\emptyset}15\;mm$ disk. The disk-type samples were sintered at temperature range of $850{\sim}950^{\circ}C$. The crystal phases of the sintered specimens were perovskite structure without secondary phases. All of the measured electrical properties such as electromechanical coupling coefficients ($k_p$), mechanical quality factors ($Q_m$), and piezoelectric charge constants ($d_{33}$) were decreased with decreasing the sintering temperatures. The electrical properties measured at the sample sintered at $950^{\circ}C$ were 54% of $k_p$, 503 of $Q_m$, and 390 pC/N of $d_{33}$, respectively. These properties were considered to be fairly good for the application of multi-layered piezoelectric generators or actuators.

• 천문학회지
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• 제17권2호
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• pp.69-103
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• 1984

Five different calibrations of metal abundances of globular clusters are examined and these are compared with metallicity ranking parameters such as $(Sp)_c$, . Q39 and IR-indices. Except for the calibration $[Fe/H]_H$ by the high dispersion echelle analysis. the other calibration scales are correlated with the morphological parameters of red giant branch. In the $[Fe/H]_H$-scale. the clusters later than ${\sim}F8$ have nearly a constant metal abundance. $[Fe/H]_H{\simeq}-1.05$, regradless of morphological characteristics of horizontal branch and red giant branch. By the two fundamental calibration scales of $[Fe/H]_L$ (derived by the low dispersion analysis) and $[Fe/H]_{{\Delta}s}$ (derived by the spectral analysis of RR Lyrae stars). the globular clusters are divided into the halo clusters with [Fe/H]<-1.0 and the disk clusters confined within the galactocentric distance ${\tau}_G=10\;kpc$ and galactic plane distance |z|=3 kpc. In this case the abundance gradient is given by d[Fe/H]/$dr_G{\approx}-0.05\;kpc^{-1}$ and d[Fe/H]/$d|z|{\simeq}-0.08\;kpc^{-1}$ within ${\tau}_G=20\;kpc$ and |z|=10 kpc, respectively. According to these characteristics of the spatial distribution of globular clusters. the chemical evolution of the galactic globular clusters can be accounted for by the two-zone (disk-halo) slow collapse model when the $[Fe/H]_L$-or $[Fe/H]_{{\Delta}s}$-scale is applied. In the case of $[Fe/H]_H$-scale, the one-zone fast collapse model is preferred for the evolution of globular clusters.