• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.317-332
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• 1998

The adiabatic nuclear demagnetization cooling technique has reduced the lowest accessible temperature to the regime of microkelvin, and consequently led to a large expansion in microkelvin physics such as solid and liquid $^{3}He$, superconductivity of noble metals, spin glass transition, and nuclear magnetism. Our ability to reach temperature in microkelvin regime has greatly facilitated by the developments of dilution refrigerator and superconductivity magnet. It is appropriate to divide nuclear demagnetization cooling into two categories; those in which only the nuclear spin system is cooled down and those in which the lattice and conduction electrons in the refrigerant or the specimen are also cooled by the cooling power of nuclear spin system. The former cooling technique has utilized to investigate the nuclear magnetism at temperature in nanokelvin regime. The latter is widely used in studying the phenomena occurring in microkelvin regime. In this review paper, we will discuss the basic principles of nuclear demagnetization cooling and its applications. This work is supported by the Basic Science Research Institute Program under contract number BSRI-97-2404.

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.107-112
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• 1994

The phase transition and the surface and interface morphologies of $TiSi_2$ formed on atomically clean Si substrates are investigated. 200$\AA$ Ti and 400$\AA$ Si films on Si(ll1) have been codeposited at elevated temperatures (400~$800^{\circ}C$) in ultrahigh vacuum. The phase transition of TiSiL is characterized with using XRD. The results distinguish the formation of the C49 and C54 crystalline titanium silicides. The surface and interface morphologies of titanium silicides have been examined with SEM and TEM. A relatively smootb surface is observed for the C49 phase while a rough surface and interface are observed for C54 phase. The islanding of the C54 phase becomes severe at high temperature ($800^{\circ}C$). Islands of TiSiL have been observed at temperatures above $700^{\circ}C$ but no islands are observed at temperatures below $600^{\circ}C$. For films deposited at $400^{\circ}C$ and 500%. weak XRD peaks corresponding to TiSi were observed and TEM micrographs exhibited small crystalline regions of titanium silicide at the interface.

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.9-23
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• 1994

Epitaxial $CoSi_2$ layer has been grown on NaCl(100) substrate at low deposition temperature($200^{\circ}C$) by multitarget bias cosputter deposition(MBCD). The phase sequence and crystallinity of deposited silicide as a function of deposition temperature and substrate bias voltage were studied by X-ray diffraction(XRD) and transmission electron microscopy(TEM) analysis. Crystalline Si was grown at $200^{\circ}C$ by metal induced crystallization(M1C) and self bias effect. In addition to, the MIC was analyzed both theoretically and experimentally. The observed phase sequence was $Co_2Si \to CoSi \to Cosi_2$ and was in good agreement with that predicted by effective heat of formation rule. The phase sequence, the CoSi(l11) preferred orientation, and the crystallinity had stronger dependence on the substrate bias voltage than the deposition temperature due to the collisional cascade mixing, the in-situ cleaning, and the increase in the number of nucleation sites by ion bombardment of growing surface. Grain growth induced by ion bombardment was observed with increasing substrate bias voltage at $200^{\circ}C$ and was interpreted with ion bombardment dissociation model. The parameters of $E_{Ar}\;and \alpha(V_s)$ were chosen to properly quantify the ion bombardment effect on the variation in crystallinty at $200^{\circ}C$ with increasing substrate bias voltage using Langmuir probe.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.11a
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• pp.469-472
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• 2006

BI 및 ETABr의 농도변화에 따른 속도상수의 변화는 이 반응이 단순한 1차 및 2차 반응 속도식에 맞지 않는다. 이와 같은 현상은 용액 속에서 두 반응 시약인 p-NPDPIN 및 BI와 상전이촉매인 ETABr 사이에 많은 수의 작은 응집된 입자(aggregates)을 형성함을 의미한다. 수용액 속에서는 불용성인 p-NPDPIN과 수용성인 BI가 충돌하여 반응할 기회가 적은데 반하여 ETABr은 이 두 시약을 함께 수용하여 세 분자 사이에 응집현상이 일어남으로 p-NPDPIN과 BI가 반응하기에 충분한 거리 내에 있게 된다. 바꾸어 말하면, 이 두 반응물질이 1:1 adducts로 반응하기보다는 여러 ETABr과 함께 많은 수의 반응분자들이 회합(응집) 되어 있음을 뜻한다.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.324-328
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• 2009

The internal short-circuit between cathodes and anodes has been known to be a critical concern for the safety failures of lithium-ion batteries, which is strongly influenced by the thermal stability of separators. In this study, to effectively suppress the internal short-circuit failures, we developed a new composite separator with the improved thermal stability compared to conventional polyolefin-based separators. The composite separators were prepared by introducing a ceramic coating layer ($Al_2O_3$/PVdF-HFP) onto both sides of a polyethylene (PE) separator. The microporous structure of ceramic coating layers is determined by controlling the phase inversion of coating solutions and becomes more developed with the increase of nonsolvent (water) content. This structural change of ceramic coating layers was observed to greatly affect the thermal stability as well as the electrochemical performance of composite separators, which was systematically discussed in terms of phase inversion.

• The Korean Journal of Zoology
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• v.5 no.1
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• pp.13-20
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• 1962

1. 1957년 8월 7일부터 18일까지 계룡산에서 고도차분포를 조사하기 위하여 고도별 4 지점에서 과물 (복숭아, 도마도) trap를 사용하여 오전 6시와 오후 6시에 동시에 초파리를 채집하였다. 그리고 sweeping 도 하여 총 33 종을 채집하였는데 다음종들은 높은 지점에서 발견되었다. Microdrosophila purpurata, Mycodrosophila basalis, Parascaptomyz disticha, Scaptomyza aplicalis , Drosophila histrioides, D.difasciata, D.histrio. 그리고 초파리의 성비가 고도에 따라 변동하였음을 관찰하였는데 특히. D. suzukii 는 저지에서 충이 현저히 많았던 것이 700미 고지에서는 거의 1 : 1의 성비를 보여주었다. 300 미높이의 (B) 지점에서 D.lacertosa 와D. Coracina 의 일주기활동은 반대적이었는데 D.lacertosa 는 습도가 높은 아침에 주로 활동하고, D.coracina는 이와 반대로 주로 오후에 활동하고 있음을 알았다. 2. 초파리 집단의 계절적 변동을 조사하기 위하여 1958년 4월부터 11월까지 매일 중순삼일씩 공주잠업시험소구내 상전에서 그리고 동년 5월 터 11월까지는 매일 초순삼일식 계룡산에서 각각 5개의 과물 trap를 설치하고 비교관찰하엿따. 매월 초파리종들의 계절적 변동은 3 표와 4 표에 기재된 바와같다. 특히 D.auraria는 두장소에서 우점종이었는데 공주잠업시험소구내 상전에서는 9월에 최고에 달했고, 계룡산에서는 8월에 최고에 달하는 unimodality를 표시하였다. 3 . 초파리의 일주기활동을 조사하기 위하여1959년 6월부터 10월까지 공주잠업시험소구내 상전에서 매월 2일간씩 2시간마다 채집을 하였다. 이 지방에서 우점종인 D.auraria 는 매월 일주기활동에 있어서 bimodality를 형성하였는데 9, 10월에는 두 peak는 서로 근접되었다. 그리고 6월 26일 2시간마다 sweeping 법으로 채집한 D.auraria의 일주기활동도 비교연구하였는데 거의 같은 현상을 나타냈다.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.256-262
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• 1998

The torque of SRM depends on phase current and the derivative of inductance. But the inductance of SRM is nonlinearly changed according to rotor position angle and phase current because of saturation in magnetic circuit, and it is difficult to control the desired torque. This paper proposes inductance modeling method using ANN(Artificial Neural Network) that is used to simulate the inductance which is nonlinearly varied with rotor position and current. The torque ripple is analyzed and input voltage and current condition to reduce torque ripple is simulated by inductance model.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.171-174
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• 1997

It was experimentally identified, for the first time, that oxygen phonons play an important role in the low temperature degradation(tetragonallongrightarrowmonoclinic phase transformation) of yttria stabilized tetragonal zir-conia polycrystals (Y-TZP). The degradation accompanied by immersing the samples in the boiling water were markedly reduced by substituting of 18O for 16O in Y-TZP. This was attributed to the heavier mass of 18O which leads to the smaller probability to find oxygen atoms beyond certain critical displacements.

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.157-161
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• 2001

The observe relaxation phenomena and freezing behavior in Pb(Mg/sub ⅓/Nb/sub ⅔/O₃, relaxor ferroelectrics, weak electric-field properties as well as strong electric-field properties were investigated. The temperature dependence of the dielectric properties obtained using the low electric-field of 1 V/w was investigated. The dielectric properties obtained from the slope of the dielectric hysteresis loop and the temperature dependence of the pyroelectric properties were also investigated. When fitting all the experimental data with the Vogel-Filcher relation, a close agreement between the experimental data and equation was observed. The freezing temperature could be consistently calculated by the various methods.

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.122-127
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• 2001

수열법으로 합성한 헥토라이트 점토(SHC), 아크릴 라텍스 및 코팅첨가제들을 배합하여 성분이 다른 수성코팅제(WBC-0, WBC-1, WBC-2) 3종류를 제조하였다. 제조한 수성코팅제(WBC)의 pH, 용액점도 및 고형분을 조사하였고, 전단력에 따른 유동성을 레오메타로 측정하였다. 또한 WBC로부터 주조된 필름의 열안정성과 투명성을 각각 TGA와 UV-VIS 분광광도계로 조사하였다. SHC가 8 phr 포함된 WBC-2는 전단력에 따라 졸과 겔의 상전이 현상, 즉 요변성을 나타내었으며 이로 인해 저장안정성이 우수하였다. 주조한 WBC-1과 WBC-2 필름의 초기분해온도와 투명성은 시판 WBC(OP-55W)의 필름보다 각각 99.6~110.2$^{\circ}C$와 20.9~21.7%의 범위로 증가하였다. 결과적으로, SHC가 함유된 WBC는 수팽윤성 점토에 의해 내열성과 용액점도의 증대효과가 나타났다.