• Title/Summary/Keyword: T-N

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Suppression of superconductivity in superconductor/ferromagnet multilayers

  • Hwang, T.J.;Kim, D.H.
    • Progress in Superconductivity and Cryogenics
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    • v.18 no.1
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    • pp.33-36
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    • 2016
  • Suppression of the superconducting transition temperature ($T_c$) of NbN thin films in superconductor/ferromagnet multilayers has been investigated. Both superconducting NbN and ferromagnetic FeN layers were deposited on thermally oxidized Si substrate at room temperature by using reactive magnetron sputtering in an $Ar-N_2$ gas mixture. The thickness of FeN films was fixed at 20 nm, while the thickness of NbN films was varied from 3 nm to 90 nm. $T_c$ suppression was clearly observed in NbN layers up to 70 nm thickness when NbN layer was in proximity with FeN layer. For a given thickness of NbN layer, the magnitude of $T_c$ suppression was increased in the order of Si/FeN/NbN, Si/NbN/FeN, and Si/FeN/NbN/FeN structure. This result can be used to design a spin switch whose operation is based on the proximity effect between superconducting and ferromagnetic layers.

Thermotropic Liquid Crystalline Behavior of [4-{4'-(Nitrophenylazo)phenoxycarbonyl}]alkanoated Celluloses ([4-{4'-(니트로페닐아조)펜옥시카보닐}]알카노화 셀룰로오스들의 열방성 액정 거동)

  • Jeong, Seung-Yong;Ma, Yung-Dae
    • Polymer(Korea)
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    • v.33 no.1
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    • pp.58-66
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    • 2009
  • The thermotropic liquid crystalline behavior of the homologous series of cellulose tri[4-{4'-(nitrophenylazo) phenoxycarbonyl}] alkanoates (NACEn, n=2$\sim$8, 10, the number of methylene units in the spacer) have been investigated. All of the homologoues formed monotropic nematic phases. The isotropic-nematic transition temperature ($T_{iN}$) decreased when n is increased up to 7, but it became almost constant when n is more than 7. The plot of transition entropy at $T_{iN}$ against n had a sharp negative inflection at n=7. The sharp change at n=7 may be attributed to the difference in arrangement of the side groups. The melting temperature ($T_m$) and associated entropy change at $T_m$, in contrast with $T_{iN}$ and associated entropy change at $T_{iN}$, exhibited a distinct odd-even effect, suggesting that the average shape of the side chains in the crystalline phase is different from that in the nematic phase. The thermal stability and degree of order of the nematic phase observed for NACEn were significantly different from those reported for the homologous series of side-chain and combined type liquid crystal polymers bearing azobenzene or biphenyl units in the side chains. The results were discussed in terms of the differences in the chemical structure, the flexibility of the main chain, the mode of chemical linkage of the side group with the main chain, and the number of the mesogenic units per repeating unit.

AN EXTENSION OF SCHNEIDER'S CHARACTERIZATION THEOREM FOR ELLIPSOIDS

  • Dong-Soo Kim;Young Ho Kim
    • Bulletin of the Korean Mathematical Society
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    • v.60 no.4
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    • pp.905-913
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    • 2023
  • Suppose that M is a strictly convex hypersurface in the (n + 1)-dimensional Euclidean space 𝔼n+1 with the origin o in its convex side and with the outward unit normal N. For a fixed point p ∈ M and a positive constant t, we put 𝚽t the hyperplane parallel to the tangent hyperplane 𝚽 at p and passing through the point q = p - tN(p). We consider the region cut from M by the parallel hyperplane 𝚽t, and denote by Ip(t) the (n + 1)-dimensional volume of the convex hull of the region and the origin o. Then Schneider's characterization theorem for ellipsoids states that among centrally symmetric, strictly convex and closed surfaces in the 3-dimensional Euclidean space 𝔼3, the ellipsoids are the only ones satisfying Ip(t) = 𝜙(p)t, where 𝜙 is a function defined on M. Recently, the characterization theorem was extended to centrally symmetric, strictly convex and closed hypersurfaces in 𝔼n+1 satisfying for a constant 𝛽, Ip(t) = 𝜙(p)t𝛽. In this paper, we study the volume Ip(t) of a strictly convex and complete hypersurface in 𝔼n+1 with the origin o in its convex side. As a result, first of all we extend the characterization theorem to strictly convex and closed (not necessarily centrally symmetric) hypersurfaces in 𝔼n+1 satisfying Ip(t) = 𝜙(p)t𝛽. After that we generalize the characterization theorem to strictly convex and complete (not necessarily closed) hypersurfaces in 𝔼n+1 satisfying Ip(t) = 𝜙(p)t𝛽.

WEYL'S THEOREM, TENSOR PRODUCT, FUGLEDE-PUTNAM THEOREM AND CONTINUITY SPECTRUM FOR k-QUASI CLASS An* OPERATO

  • Hoxha, Ilmi;Braha, Naim Latif
    • Journal of the Korean Mathematical Society
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    • v.51 no.5
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    • pp.1089-1104
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    • 2014
  • An operator $T{\in}L(H)$, is said to belong to k-quasi class $A_n^*$ operator if $$T^{*k}({\mid}T^{n+1}{\mid}^{\frac{2}{n+1}}-{\mid}T^*{\mid}^2)T^k{\geq}O$$ for some positive integer n and some positive integer k. First, we will see some properties of this class of operators and prove Weyl's theorem for algebraically k-quasi class $A_n^*$. Second, we consider the tensor product for k-quasi class $A_n^*$, giving a necessary and sufficient condition for $T{\otimes}S$ to be a k-quasi class $A_n^*$, when T and S are both non-zero operators. Then, the existence of a nontrivial hyperinvariant subspace of k-quasi class $A_n^*$ operator will be shown, and it will also be shown that if X is a Hilbert-Schmidt operator, A and $(B^*)^{-1}$ are k-quasi class $A_n^*$ operators such that AX = XB, then $A^*X=XB^*$. Finally, we will prove the spectrum continuity of this class of operators.

Effects on n-Alcohols on the Amino-Proton Chemical Shifts and on the Hindered Rotation about the N-C(O) Bond of Acetamide (아세트아미드의 아미노 양성자의 화학적 이동과 N-C(O) 결합주위의 부자유회전에 미치는 n-알코올 용매 효과)

  • Gwon, Sun Gi;Choe, Jong Ho;Choe, Yeong Sang;Yun, Chang Ju;Gwon, Dae Geun
    • Journal of the Korean Chemical Society
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    • v.34 no.6
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    • pp.509-516
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    • 1990
  • 1H-nmr chemical shifts and lineshapes of amino-protons of acetamide (AA) in n-alcohols were determined. The chemical shifts are discussed by the Reichardt's solvent polarity parameter, E$_{T}$(30). The following relationship between $\delta$obs and E$_{T}$(30) was obtained. ${\delta}_{obs}$ = ${\delta}_{o}$ + aE$_{T}$ (30) + b[E$_{T}$(30)]$^2$ where ${\delta}_{o}$ is the chemical shift of the solute in gaseous state or at $E_{T}$(30) = 0, a is a characteristic constant for the protons of AA in n-alcohol solutions and b is a constant for the solute (AA)-solvent (n-alcohols) interaction. The barrier of the hindered rotation about the N-C(O) bond in AA was obtained by analysis of the lineshapes of the amino-protons in AA. The behavior of the internal rotation as well as chemical shifts of the amino-protons in AA has been found to be closely related to the $E_{T}$(30) of n-alcohols.

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A Study on the Application of Machine Learning for River T-N Prediction (하천 T-N 예측을 위한 머신러닝 적용 연구)

  • Gwang Min Ok;Su Han Nam;Young Do Kim
    • Proceedings of the Korea Water Resources Association Conference
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    • 2023.05a
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    • pp.201-201
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    • 2023
  • 일반적으로 하천의 수질은 산업화, 인구증가 등으로 인해 여러 종류의 오염물질이 유입되어 악화된다. 수질 악화의 대표적인 현상은 부영양화이며 이를 일으키는 주요 원인 물질은 통상 영양염류라고 말하는 질소와 인으로 알려져 있다. T-N이 다량 수계로 유입되면 식물성 플랑크톤 등이 대량 번식하여 녹조 현상등 수질 악화를 발생시켜 관리가 필요하다. 현재 많은 수자원 관리 부서에서 모니터링 포인트를 설정하여 수질 변화를 관찰하고 있다. 기존의 T-N 분석방법은 (1) 자외선 흡광광도법 (2) 카드뮴 환원법 (3) 환원증류-킬달법등이 있다. 그러나 이러한 방법들은 실험실 기반의 정량적 분석으로 시간과 비용이 크게 소요되어 발생하는 문제에 대해 초기대응을 하기 힘들다. 따라서 T-N을 효과적으로 측정할 수 있는 방법이 필요하다. 국내에서는 수질자료를 통한 연관된 수질 인자를 찾아내어 머신러닝 알고리즘을 활용해 Chl-a 농도를 추정한 연구사례가 있다. 국외에서는 TN과 센서 측정 지표 간의 물리적, 화학적 관계를 기반으로 센서 감지의 적시성과 지능형 알고리즘의 정확도를 결합하여 실시간 총질소(TN) 측정 방법 연구 사례가 있다. 따라서 본 연구에서는 머신러닝을 활용하여 국내에 적합한 T-N 예측 모델을 만들고자한다. 본 연구에서는 센서기반으로 측정가능한 수질항목들과 T-N의 상관성 분석을 통해 주요 수질인자를 도출하였다. 도출된 인자와 Python 기반의 머신러닝을 활용하여 T-N을 추정하였다. 그 후, T-N 추정값과 실측값을 비교하여 머신러닝 성능을 평가하고 실제 적용 가능성에 대해서 검증하였다. 본 연구는 기존 T-N 측정에 소모되는 시간과 비용의 감소에 기여하고 이를 통해 앞으로 더 정확한 수질 예측이 가능해질 것으로 기대된다.

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Derivations of Upper and Lower Bounds of the Expected Busy Periods for a Controllable M/G/1 Queueing Model Operating Under the Triadic Max(N, T, D) Policy (삼변수 Max(N, T, D) 운용방침이 적용되는 조정가능한 M/G/1 대기모형의 busy period 기대값의 상한과 하한 유도)

  • Rhee, Hahn-Kyou
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.34 no.1
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    • pp.67-73
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    • 2011
  • Using the known result of the expected busy period for a controllable M/G/1 queueing model operating under the triadic Max (N, T, D) policy, its upper and lower bounds are derived to approximate its corresponding actual value. Both bounds are represented in terms of the expected busy periods for the dyadic Min (N, T), Min (N, D) and Min (T, D) and simple N, T and D operating policies. All three input variables N, T and D are equally contributed to construct such bounds for better estimation.

The Cumulants of the Non-normal t Distribution

  • Hwang, Hark
    • Journal of the Korean Statistical Society
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    • v.5 no.2
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    • pp.91-100
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    • 1976
  • The use of the statistic $t = \sqrt{n} (x-\mu)/S$, where $\bar{X) = \sum X_i/n, \mu = E(X_i), S^2 = \sum(X_i-\bar{X})^2/(n-1)$ in statistical inference is usually done under the assumption of normality of the population. If the population is not normally distributed the tabulated values of student t are no longer valid. The moments of t are obtained as a power series in $1/\sqar{n}$ whose coefficients are functions of the cumulants of X. The cumulants are obtained from the moments in the usual manner. The first eight cumulants of t are given up to terms of order $1/n^3$. The first eight cumulants of t are given up to terms of order $1/n^3$. These results extend those of Geary who gave the first six cumulants of t to order $1/n^2$.

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The Moment Problem and Cn-Scalar Operators

  • de Laubenfels, Ralph
    • Honam Mathematical Journal
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    • v.7 no.1
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    • pp.7-13
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    • 1985
  • We show that a bounded linear qperator, T, on a Banach space, X, is $C^{n}$-scalar if the sepuence {$\frac{k!}{(k+n)!}{\phi}(T^{k+n}x)$}$_{k=0}^{\infty}$ is positive-definite, for sufficiently many $\phi$ in $X^{\ast}$, x in X. We use this to show that $(T_{n}f)(t){\equiv}tf(t)+nJf(t)$, where $If(t)=\int_{0}^{1}f(s)ds$, is $C^{n}$-scalar on $L^{p}([0,1],v)$, for $1{\leq}p{\leq}\infty$, for a large class of measures, v. Other corollaries include the spectral theorem for bounded symmetric operators on a Hilbert space.

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Derivations of Upper and Lower Bounds of the Expected Busy Periods for the Triadic Min(N, T, D) Operating Policy applied to a Controllable M/G/1 Queueing Model (조정가능한 M/G/1 대기모형에 삼변수 Min(N, T, D) 운용방침이 적용될 때 busy period 기댓값의 상한과 하한 유도)

  • Rhee, Hahn-Kyou
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.33 no.2
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    • pp.97-104
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    • 2010
  • Using the known result of the expected busy period for the triadic Min (N, T, D) operating policy applied to a controllable M/G/1 queueing model, its upper and lower bounds are derived to approximate its corresponding actual value. Both bounds are represented in terms of the expected busy periods for the dyadic Min (N, T), Min (N, D) and Min (T, D) and simple N, T and D operating policies. All three input variables N, T and D are equally contributed to construct such bounds for better approximations.