• 대한기계학회논문집B
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• 제36권1호
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• pp.1-8
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• 2012

본 연구에서는 주름높이가 고려된 판형열교환기의 완전발달유동 및 열전달특성을 수치적으로 해석하였다. 여러 개의 단위셀(5개 또는 7개)을 연결한 다중셀에 입구부와 출구부가 부착된 모델을 기본으로 P/H비 변화($2.0{\leq}P/H{\leq}4.0$)에 따른 모델에 대하여 수치해석을 수행하였다. 작동유체는 물이며, 수치조건은 쉐브론각 $20^{\circ}$, $300{\leq}Re{\leq}1,500$이다. 그리고 마찰인자는 $f=CRe^m$의 형태로, Colburn 계수는 $j=CRe^m$의 형태로 상관관계식을 제시하였다. 수치해석 결과 완전발달유동은 세 번째 셀부터 시작되었으며, 누셀트수는 P/H비가 작을수록 큰 값을 나타냈다.

• Korean Chemical Engineering Research
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• 제54권6호
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• pp.734-745
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• 2016

This review article described the electrochemical Frumkin, Langmuir, and Temkin adsorption isotherms of over-potentially deposited hydrogen (OPD H) and deuterium (OPD D) for the cathodic $H_2$ and $D_2$ evolution reactions (HER, DER) at Pt, Ir, Pt-Ir alloy, Pd, Au, and Re/normal ($H_2O$) and heavy water ($D_2O$) solution interfaces. The Frumkin, Langmuir, and Temkin adsorption isotherms of intermediates (OPD H, OPD D, etc.) for sequential reactions (HER, DER, etc.) at electrode/solution interfaces are determined using the phase-shift method and correlation constants, which have been suggested and developed by Chun et al. The basic procedure of the phase-shift method, the Frumkin, Langmuir, and Temkin adsorption isotherms of OPD H and OPD D and related electrode kinetic and thermodynamic parameters, i.e., the fractional surface coverage ($0{\leq}{\theta}{\leq}1$) vs. potential (E) behavior (${\theta}$ vs. E), equilibrium constant (K), interaction parameter (g), standard Gibbs energy (${\Delta}G_{\theta}{^{\circ}}$) of adsorption, and rate (r) of change of ${\Delta}G_{\theta}{^{\circ}}$ with ${\theta}$ ($0{\leq}{\theta}{\leq}1$), at the interfaces are briefly interpreted and summarized. The phase-shift method and correlation constants are useful and effective techniques to determine the Frumkin, Langmuir, and Temkin adsorption isotherms and related electrode kinetic and thermodynamic parameters (${\theta}$ vs. E, K, g, ${\Delta}G_{\theta}{^{\circ}}$, r) at electrode/solution interfaces.

• E2M - 전기 전자와 첨단 소재
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• 제4권2호
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• pp.123-131
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• 1991

SiH$_{4}$환원에 의한 selective CVD-W 공정에서 SiH$_{4}$ 유속의 W막 특성에 대한 효과를 조사하였다. 0.7$_{4}$/SW$_{2}$(=R)<0.9에서 .betha.-W이 나타나기 시작하여 SiH$_{4}$ 유속의 증가에 따라 .betha.-W의 함량은 게속 증가한다. W막의 표면 형태도 SiH$_{4}$유속의 증가에 따라 나뭇잎 모양(R<0.5), 흐릿하고 불안정한 모양(0.70.9에서는 주상의 결정립을 나타낸다. R.leq.0.7에서는 .alpha.-W만 존재하다가 0.7$_{4}$유속의 증가에 따라 증착속도와 W막의 정기저항이 증가한다. 특히, R.geq.0.9에서 전기저항이 급증한다. SiH$_{4}$유속의 증가에 따라 선택성이 악화되며 특히 1.1

• Journal of applied mathematics & informatics
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• 제10권1_2호
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• pp.27-40
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• 2002

For two integers m, n with m $\leq$ n, an [m,n]-factor F in a graph G is a spanning subgraph of G with m $\leq$ d$\_$F/(v) $\leq$ n for all v ∈ V(F). In 1996, H. Enomoto et al. proved that every 3-connected Planar graph G with d$\_$G/(v) $\geq$ 4 for all v ∈ V(G) contains a [2,3]-factor. In this paper. we extend their result to all 3-connected locally finite infinite planar graphs containing no unbounded faces.

• 대한수학회보
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• 제45권1호
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• pp.59-66
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• 2008

Keskin and Harmanci defined the family B(M,X) = ${A{\leq}M|{\exists}Y{\leq}X,{\exists}f{\in}Hom_R(M,X/Y),\;Ker\;f/A{\ll}M/A}$. And Orhan and Keskin generalized projective modules via the class B(M, X). In this note we introduce X-local summands and X-hollow modules via the class B(M, X). Let R be a right perfect ring and let M be an X-lifting module. We prove that if every co-closed submodule of any projective module P contains Rad(P), then M has an indecomposable decomposition. This result is a generalization of Kuratomi and Chang's result [9, Theorem 3.4]. Let X be an R-module. We also prove that for an X-hollow module H such that every non-zero direct summand K of H with $K{\in}B$(H, X), if $H{\oplus}H$ has the internal exchange property, then H has a local endomorphism ring.

• 한국토양비료학회지
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• 제43권5호
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• pp.584-589
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• 2010

경남지역 단감 재배지 31개소의 토양 미량성분 변화를 조사하여 기초자료로 활용하고 농가현장에서 pH 분석 값을 적용하여 석회소요량을 신속하게 산출할 수 있는 계산식을 구하였다. 가용성 미량성분 함량의 변화는 4월이 표토에서 Fe 76.5 mg $kg^{-1}$, Mn 46.1 mg $kg^{-1}$, Zn 16.9 mg $kg^{-1}$ 이었고 심토는 Fe 55.5 mg $kg^{-1}$, Mn 35.9 mg $kg^{-1}$, Zn 12.3 mg $kg^{-1}$으로 가장 높았으며 Mn 함량은 4월 이후 지속적으로 감소되었다. 표토의 pH가 높아짐에 따라 Fe 함량은 y=-18.8x+162(r=0.374, $p{\leq}0.001$), Mn 함량은 y=-11.5x+98 (r=0.407, $p{\leq}0.001$)의 고도로 유의적인 부의상관을 나타냈다. 단위면적당 석회소요량 (kg $10a^{-1}$)은 표토의 pH와 y=-171x+1,148 (r=0.881, $p{\leq}0.001$), 심토의 pH는 y=-190x+1,247(r=0.855, $p{\leq}0.001$)의 고도로 유의적인 부의상관을 보였다. 따라서 이러한 산술식을 이용할 경우 농가현장에서 석회소요량을 신속하게 산출하여 토양개량제를 시용할 수 있으며 pH로 인한 양분 불균형을 해소할 수 있을 것으로 기대된다.

• 한국재료학회지
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• 제29권11호
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• pp.690-696
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• 2019

Geopolymer is an alumina silicate-based ceramic material that has good heat-resistance and fire-resistance; it can be cured at room temperature, and thus its manufacturing process is simple. Geopolymer can be used as a reinforcement or floor finish for high-speed curing applications. In this manuscript, we investigate a high-speed curing geopolymer achieved by adding calcium to augment the curing rate. Metakaolin is used as the main raw material, and aqueous solutions of KOH and $K_2SiO_3$ are used as the activators. As a result of optimizing the high bending strength as a target factor for geopolymers with $SiO_2/Al_2O_3$ ratio of 4.1 ~ 4.8, the optimum ranges of the active agent are found to be $0.1{\leq}K_2O/SiO_2{\leq}0.4$ and $10{\leq}H_2O/K_2O{\leq}32.5$, and the optimum range of the curing accelerator is found to be $$0.82{\leq_-}Ca(OH)_2/Al_2O_3{\leq_-}2.87$$. The maximum flexural strength is found to be 1.35 MPa at $Ca(OH)_2/Al_2O_3=2.82$, $K_2O/SiO_2=0.3$, and $H_2O/K_2O=11.3$. The physical and thermal properties are analyzed to validate the applicability of these materials as industrial insulating parts or repairing finishing materials in construction.

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1157-1163
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• 2009

Let G be a graph with vertex set V(G) and let f be a nonnegative integer-valued function defined on V(G). A spanning subgraph F of G is called a fractional f-factor if $d^h_G$(x)=f(x) for all x $\in$ for all x $\in$ V (G), where $d^h_G$ (x) = ${\Sigma}_{e{\in}E_x}$ h(e) is the fractional degree of x $\in$ V(F) with $E_x$ = {e : e = xy $\in$ E|G|}. In this paper it is proved that if ${\delta}(G){\geq}{\frac{b^2(k-1)}{a}},\;n>\frac{(a+b)(k(a+b)-2)}{a}$ and $|N_G(x_1){\cup}N_G(x_2){\cup}{\cdots}{\cup}N_G(x_k)|{\geq}\frac{bn}{a+b}$ for any independent subset ${x_1,x_2,...,x_k}$ of V(G), then G has a fractional f-factor. Where k $\geq$ 2 be a positive integer not larger than the independence number of G, a and b are integers such that 1 $\leq$ a $\leq$ f(x) $\leq$ b for every x $\in$ V(G). Furthermore, we show that the result is best possible in some sense.

• 호남수학학술지
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• 제45권1호
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• pp.123-129
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• 2023

In this paper, we introduce the reverse of the operator Davis-Choi-Jensen's inequality. Our results are employed to establish a new bound for the Furuta inequality. More precisely, we prove that, if $A,\;B{\in}{\mathcal{B}}({\mathcal{H}})$ are self-adjoint operators with the spectra contained in the interval [m, M] with m < M and A ≤ B, then for any $r{\geq}{\frac{1}{t}}>1,\,t{\in}(0,\,1)$ $A^r{\leq}({\frac{M1_{\mathcal{H}}-A}{M-m}}m^{rt}+{\frac{A-m1_{\mathcal{H}}}{M-m}}M^{rt}){^{\frac{1}{t}}}{\leq}K(m,\;M,\;r)B^r,$ where K (m, M, r) is the generalized Kantorovich constant.

• 대한수학회지
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• 제32권4호
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• pp.761-773
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• 1995

The nonlinear boundary value problem $$ y" = f(x, y, y') = -\frac{x}{3}y' - \frac{y^2}{g(x)}, 0 < x < 1, $$ $$ (1.1) y'(0) = 0, and either (H) : y(1) = \lambda > 0 $$ $$ or (S) : y'(1) + (1 - \upsilon)y(1) = 0, 1 - \upsilon > 0, $$ $$g \in C[0, 1], k \leq g(x) \leq K on [0, 1] for some k, K > 0 $$ arises in the nonlinear circular membrane under normal pressure [2, 3]., 3].