• 한국결정성장학회지
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• 제21권3호
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• pp.99-104
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• 2011

단결정 성장을 위한 $MgGa_2Se_4$ 다결정은 수평 전기로에서 합성하였으며, 결정구조는 rhombohedral이고 격자상수 $a_0$는 3.953 ${\AA}$, $c_0$는 38.890 ${\AA}$였다. $MgGa_2Se_4$ 단결정박막은 HWE(Hot Wall Epitaxy) 방법으로 반절연성 GaAs(100)기판에 성장시켰다. 단결정박막의 성장 조건은 증발원의 온도 $610^{\circ}C$, 기판의 온도 $400^{\circ}C$에서 진행되었으며 성장 속도는 0.5 ${\mu}m/h$였다. 단결정박막의 결정성은 이중 결정 x-선 회절곡선의 반폭치와 X-선 회절무늬의 ${\omega}-2{\theta}$로부터 구하여 최적 성장 조건을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293 K에서 각각 $6.21{\times}10^{18}/cm^3$, 248 $cm^2/v{\cdot}s$였다. $MgGa_2Se_4$/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수 스펙트럼을 10 K에서 293 K까지 측정하였다. 광흡수 스펙트럼으로부터 구한 에너지 갭 $E_g(T)$는 varshni 공식 $E_g(T)=E_g(0)=({\alpha}T^2/T+{\beta})$을 잘 만족함을 알 수 있었다. 여기서 $E_g(0)=2.34\;eV$, ${\alpha}=8.81{\times}10^{-4}\;eV/K$, ${\beta}=251\;K$였다.

• 한국결정성장학회지
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• 제18권5호
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• pp.217-224
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• 2008

수평 전기로에서 $ZnIn_2Se_4$ 단결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 $ZnIn_2Se_4$ 단결정 박막을 반절연성 GaAs(100) 기판에 성장시켰다. $ZnIn_2Se_4$ 단결정 박막의 성장 조건을 증발원의 온도 $630^{\circ}C$, 기판의 온도 $400^{\circ}C$였고 성장 속도는 0.5 $\mu m/hr$였다. $ZnIn_2Se_4$ 단결정 박막의 결정성의 조사에서 10K에서 광발광(photoluminescence) 스펙트럼이 682.7nm ($1.816{\underline{1}}eV$)에서 exciton emission 스펙트럼이 가장 강하게 나타났으며, 또한 이중결정 X-선 요통곡선(DCRC)의 반폭치(FWHM)도 128 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농노와 이동도는 293 K에서 각각 $9.41\times10^{16}/cm^{-3}$, $292cm^2/V{\cdot}s$였다. $ZnIn_2Se_4$/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수와 광전류 spectra를 293 K에서 10K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap $E_g(T)$는 varshni공식에 따라 계산한 결과 $E_g(T)=1.8622\;eV-(5.23\times10^{-4}eV/K)T^2/(T+775.5K)$ 이었으며 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting energy ${\Delta}cr$값이 182.7meV이며 spin-orbit energy ${\Delta} so$값은 42.6meV임을 확인하였다. 10 K일 때 광전류 봉우리들은 n= 1, 27일때 $A_{1}-$, $B_{1}-$와 $C_{27}-exciton$ 봉우리임을 알았다.

• 한국결정성장학회지
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• 제23권6호
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• pp.283-290
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• 2013

수평 전기로에서 $MgGa_2Se_4$ 다결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 $MgGa_2Se_4$ 단결정 박막을 반절연성 GaAs(100)기판에 성장시켰다. $MgGa_2Se_4$단결정 박막의 성장 조건은 증발원의 온도 $610^{\circ}C$, 기판의 온도 $400^{\circ}C$였고 성장 속도는 $0.5{\mu}m/hr$였다. 이때 이중결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)도 212 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. $MgGa_2Se_4$/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수와 광전류 spectra를 293 K에서 10 K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap Eg(T)는 varshni공식에 따라 계산한 결과 $E_g(T)=2.34 eV-(8.81{\times}10^{-4}eV/K)T^2/(T+251K)$이었으며 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting energy ${\Delta}cr$값이 190.6 meV이며 spin-orbit energy ${\Delta}so$값은 118.8 meV임을 확인하였다. 10 K일 때 광전류 봉우리들은 n = 1, 27일때 $A_{1^-}$, $B_{1^-}$와 $C_{27}-exciton$ 봉우리임을 알았다.

• Asian-Australasian Journal of Animal Sciences
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• 제19권11호
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• pp.1597-1602
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• 2006

The effects of different mineral supplementations on the milk yield of free-ranging Somali camels were investigated in two phases in a semi-arid region of northern Kenya during the dry and wet seasons in 2002 and 2003. In phase 1, twelve (12) lactating camels were selected at random to form four (4) groups each consisting of three camels. The first group served as the control and as a result received no mineral supplementation. In addition to the control diet the other groups received oral doses of minerals as follows over a 60-day period: T1 (P), T2 (High Cu low Co) and T3 (Low Cu high Co). The daily milk yield and blood mineral profiles were measured during the wet and dry seasons. The mean daily milk yield increased from 3.4 L/d to $4.3{\pm}0.3L/d$ and 5.2 L/d in the dry and wet seasons, respectively. Fifteen (15) lactating camels were selected at random to form five groups each consisting of three replicates. The control group did not receive any mineral supplement. The other four groups in addition to the control diet, received the following treatments: T4 (Common Salt), T5 (High Co), T6 (High Co+P) and T7 (Low Co+P). Mineral supplement T6 produced significantly higher milk yield ($5.4{\pm}0.5$ and $6.5{\pm}0.7L/d$) during the dry and wet seasons. Both T6 and T7 had significantly higher milk yield than T4 and T5. During both phases, the blood Ca and P level significantly increased in camels receiving T1, 6 and 7. Animals that received only the trace mineral supplements had lower blood P compared to the ones receiving supplementary P and also the control. Supplementation of lactating camels with Co and P significantly (p<0.05) increased milk yield). Effect of common salt, commonly given by farmers, on milk yield was insignificant. It was concluded that mineral supplementation to lactating camels was beneficial, and that mineral supplements should include P and Co. Further research is required to establish P and Co requirements of lactating camels.

• 센서학회지
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• 제11권5호
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• pp.309-318
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• 2002

수평 전기로에서 $CdIn_2S_4$ 다결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 $CdIn_2S_4$ 단결정 박막을 반절연성 GaAs (100)기판에 성장시켰다. $CdIn_2S_4$ 단결정 박막의 성장 조건은 증발원의 온도 $630^{\circ}C$, 기판의 온도 $420^{\circ}C$였고 성장 속도는 $0.5\;{\mu}m/hr$였다. $CdIn_2S_4$ 단결정 박막의 결정성의 조사에서 10 K에서 광발광(photoluminescence) 스펙트럼이 463.9 nm (2.6726 eV)에서 exciton emission 스펙트럼이 가장 강하게 나타났으며, 또한 이중 결정 X-선 요동 곡선(DCRC)의 반폭치(FWHM)도 127 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 $9.01{\times}10^{16}/cm^3$, $219\;cm^2/V{\cdot}s$였다. $CdIn_2S_4$/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수와 광전류 spectra를 293K에서 10K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap $E_g(T)$는 Varshni 공식에 따라 계산한 결과 $2.7116eV-(7.74{\times}10^{-4}eV/K)T^2$/(T+434K)이었으며 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting ${\Delta}cr$값이 0.1291 eV이며 spin-orbit ${\Delta}so$값은 0.0248 eV임을 확인하였다. 10K일 때 광전류 봉우리들은 n = 1일때 $A_1$-, $B_1$-와 $C_1$-exciton 봉우리임을 알았다.

• 천문학회보
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• 제41권1호
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• pp.41.3-42
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• 2016

New CCD photometric observations of GX Aur have been made between 2004 and 2015. Our light curves are the first ever compiled and display the variable O'Connell effect. The light variations are satisfactorily modeled by including time-varying cool-spots on the component stars. Our light curve synthesis indicates that the eclipsing pair is an A-type contact binary with parameters of i = 81.1 deg, ${\Delta}T=36K$, q = 0.950 and f = 46%. Including our 25 timing measurements, a total of 83 times of minimum light spanning about 66 yr were used for a period study. It was found that the orbital period of GX Aur has varied due to two periodic oscillations superposed on an upward-opening parabolic variation. The long-term period increase rate is deduced as $+9.636{\times}10^{-10}d\;yr^{-1}$, which can be produced as a mass transfer from the secondary star to the primary at a rate of $3.136{\times}10^{-6}M_{\odot}\;yr^{-1}$, among the largest rates for contact systems. The periods and semi-amplitudes of the two periodic variations are about $P_3=8.7yr$ and $P_4=21.2yr$, and $K_3=0.011d$ and $K_4=0.017d$, respectively. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of an unseen third and fourth components with projected masses of $M_3=0.91M_{\odot}$ and $M_4=1.09M_{\odot}$ in eccentric orbits of $e_3=0.13$ and $e_4=0.73$. Because no third light was detected in the light curve synthesis, each circumbinary object could be a compact star or a binary itself.

• 천문학회지
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• 제55권1호
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• pp.1-9
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• 2022

We present the photometric properties of V608 Cas from detailed studies of light curves and eclipse timings. The light curve synthesis indicates that the eclipsing pair is an overcontact binary with parameters of ∆T = 155 K, q = 0.328, and f = 26%. We detected the third light ℓ₃, which corresponds to about 8% and 5% of the total systemic light in V and R bands, respectively. Including our 6 timing measurements, a total of 38 times of minimum light were used for a period study. It was found that the orbital period of V608 Cas has varied in some combination of an upward parabola and two periodic variations. The continuous period increase with a rate of +3.99 × 10^-7 d yr^-1 can be interpreted as a mass transfer from the secondary component to the primary star at a rate of 1.51 × 10^-7 M_⊙ yr^-1. The periods and semi-amplitudes of the two periodic variations are about P₃ = 16.0 yr and P₄ = 26.3 yr, and K₃ = 0.0341 d and K₄ = 0.0305 d, respectively. The most likely explanation of both cycles is a pair of light-traveling time effects operated by the possible presence of third and fourth components with estimated masses of M₃ = 2.20 M_⊙ and M₄ = 1.27 M_⊙ in eccentric orbits of e₃ = 0.66 and e₄ = 0.52. Because the contribution of ℓ₃ is very low compared to the estimated masses of two circumbinary objects, they can be inferred as very faint compact objects.

• 천문학회보
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• 제39권2호
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• pp.75.2-75.2
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• 2014

CS molecule as an important tracer for studying inward motions in dense cores is known to be adsorbed onto dusts in cold (T~10K) dense cores, resulting in its significant depletion in the central region of the cores which may hamper a proper study of kinematics stage of star formation. In this study we choose five 'evolved' dense starless cores, L1544, L1552, L1689B, L694-2 and L1197, to investigate how depletion of CS molecule is significant and how the molecule differentiates depending on the evolutional status of the dense cores, by using a rare isotopomer C34S. We performed mapping observations in C34S (J=2-1) and N2H+ (J=1-0) with Nobeyama 45 m telescope, and compared $850{\mu}m$ continuum data as a reference of the density distribution of the dense cores. Our data confirm the claim that CS molecule generally depletes out in the central region in dense starless cores, while N2H+ keeps abundant as they get evolved. All of integrated intensity maps show 'semi-ring-like' depletion holes in CS, and all of abundance radial profiles show decrease toward center. The CS depletion and molecular chemical differentiation seems to depend on the evolutional status in dense cores. The evolved cores shows low abundance at both central and outer regions, implying that in the case of highly evolved cores CS freeze-out occurs over the most area of the cores.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.18-24
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• 2019

This study was carried out to investigate the effect of milling of boron (B), which is one of raw materials of $MgB_2$, on the critical current density ($J_c$) of $MgB_2$. B powder used in this study is semi-amorphous B (Pavezyum, Turkey, 97% purity, 1 micron). The size of B powder was reduced by planetary milling using $ZrO_2$ balls (a diameter of 2 mm). The B powder and balls with a ratio of 1:20 were charged in a ceramic jar and then the jar was filled with toluene. The milling time was varied from 0 to 8 h. The milled B powders were mixed with Mg powder in the composition of (Mg+2B), and the powder mixtures were uniaxially pressed at 3 tons. The powder compacts were heat-treated at $700^{\circ}C$ for 1 h in flowing argon gas. Powder X-ray diffraction and FWHM (Full width at half maximum) were used to analyze the phase formation and crystallinity of $MgB_2$. The superconducting transition temperature ($T_c$) and $J_c$ of $MgB_2$ were measured using a magnetic property measurement system (MPMS). It was found that $B_2O_3$ was formed by B milling and the subsequent drying process, and the volume fraction of $B_2O_3$ increased as milling time increased. The $T_c$ of $MgB_2$ decreased with increasing milling time, which was explained in terms of the decreased volume fraction of $MgB_2$, the line broadening of $MgB_2$ peaks and the formation of $B_2O_3$. The $J_c$ at 5 K increased with increasing milling time. The $J_c$ increase is more remarkable at the magnetic field higher than 3 T. The $J_c$ at 5 K and 4 T was the highest as $4.37{\times}10^4A/cm^2$ when milling time was 2 h. The $J_c$ at 20 K also increased with increasing milling time. However, The $J_c$ of the samples with the prolonged milling for 6 and 8 h were lower than that of the non-milled sample.

• 한국산학기술학회논문지
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• 제18권11호
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• pp.282-289
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• 2017

경제동물에 대한 동물복지에 대한 관심은 전세계적으로 고조되고 있는 추세이다. 그러나, 국내 양돈농가는 경제성 등을 이유로 고려하지 않거나 미비한 도입으로 돼지 본연의 행동이 제한되고 있다. 따라서, 본 연구의목적은 일반적인 사육환경에 환경보조물의 제공이 육성돈의 행동특성에 미치는 영향을 구명하고자 실시하였다. 실험동물은 45두의 3원 교잡육성돈(요크셔${\times}$랜드레이스${\times}$두록; 평균체중, $33.35{\pm}5.5kg$)을 준비하였고, 완전임의배치법(randomized complete block design)에 의해 3개 처리구(대조구; 현수형 환경보조물, T1; 바닥형 환경보조물, T2)에 처리구당 3반복, 반복당 5두씩 반슬러리 돈방에 배치하였다. 현수형 환경보조물은 돼지의 어깨 높이에 현수하였고, 바닥형은 돈방의 가운데에 고정시켰다. 시험기간은 14일간 수행하였으며 시험종료일에 스트레스호르몬인 코티졸(cortisol) 농도를 분석하였고 행동특성은 1과 8일차에 촬영하였고 베가스 프로(Vegas Pro) 13.0 프로그램을 활용하여 및 분석하였다. 체중 및 일당증체량은 대조구와 처리구들간 차이가 없었다. 코티졸호르몬은 T2(25.28 ng/mL)에서 대조구(46.75 ng/mL)보다 유의적으로 낮았다(p<0.05). 1일차 행동 유형별 지속시간은 움직임과 공격 항목에서 대조구에 비해 처리구에서 유의적으로 낮았다(p<0.01). 8일차 놀이행동 지속시간에서 처리구2는 925.12초로 T1의 323.91초 보다 유의적으로 높았다(p<0.01). 반면에 처리구들에 비해 대조구는 움직이지 않는 시간이 많았다(p<0.01). 이러한 결과는 환경보조물 제공이 돼지간 공격성을 감소시키고 돼지의 행동을 활동적으로 만들어 돼지 본연의 행동요구를 충족시킬 수 있음을 시사한다. 그러나, 국내에서 환경보조물에 대한 연구는 미흡하므로 본 연구결과는 보조물을 이용한 동물복지에 대한 기초자료로서 활용 가능할 것으로 사료된다.