• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.118-122
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• 1993

The 77 K luminescence and excitation spectra, room-temperature FT-infrared and visible absorption spectra of a newly prepared complex cis-[Cr(cyclam)(pn)]$(ClO_4)_3$, where cyclam and pn represent 1,4,8,11-tetraazacyclotetradecane and 1,2-propanediamine respectively, have been measured. Absorption maximum of the first spin-allowed transition in the electronic absorption spectra of cis-[Cr(cyclam)(pn)]$^{3+}$ and cis-[Cr(cyclam)(en)]$^{3+}$ appears at nearly the same position. The two spin-allowed and six spin-forbidden electronic transitions are assigned from the visible absorption and excitation spectra. It is also shown that the zero phonon line in the excitation spectrum splits into two components by 50 cm$^{-1}$.

• Structural Engineering and Mechanics
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• 제87권4호
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• pp.363-373
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• 2023

Since the first family of structure-dependent methods can simultaneously integrate unconditional stability and explicit formulation in addition to second order accuracy, it is very computationally efficient for solving inertial problems except for adopting auto time-stepping techniques due to no nonlinear iterations. However, an unusual stability property is first found herein since its unconditional stability interval is drastically different for zero and nonzero damping. In fact, instability might occur for solving a damped stiffness hardening system while an accurate result can be obtained for the corresponding undamped stiffness hardening system. A technique of using a stability factor is applied to overcome this difficulty. It can be applied to magnify an unconditional stability interval. After introducing this stability factor, the formulation of this family of structure-dependent methods is changed accordingly and thus its numerical properties must be re-evaluated. In summary, a large stability factor can result in a large unconditional stability interval but also lead to a large relative period error. As a consequence, a stability factor must be appropriately chosen to have a desired unconditional stability interval in addition to an acceptable period distortion.

• 한국세라믹학회지
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• 제29권7호
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• pp.505-510
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• 1992

The influence of excess iron content (x) and reaction atmosphere on permittivity, permeability and microwave absorbing properties has been investigated in composite specimens embeded with (Ni0.4Zn0.6O)1-x(Fe2O3)1+x powders. A nitrogen atmosphere used for the reaction of the ferrite with excess iron composition (x>0) enhances spinel formation, and thereby increases both the magnetic and the dielectric loss of the ferrite composite. We also investigated the relation between the electromagnetic constants and the absorbing properites using impedance-matching solution maps for zero reflection. It is suggested that a superior microwave absorber can be fabricated through atmosphere and excess iron control during the powder process.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.57-63
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• 2004

A two-dimensional direct numerical simulation was performed to investigate the flame behaviors of $CH_4/N_2$-Air counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed reaction mechanism are adopted in this calculation. The results showed that an initially flat stagnation plane, on which an axial velocity was zero, was deformed into a complex-shaped plane, and an initial stagnation point was moved far away from a vortex head when the counterflow field was perturbed by the vortex. It was noted that the movement of stagnation point could alter the species transport mechanism to the flame surface. It was also identified that the altered species transport mechanism affected the distributions of the mixture fraction and the scalar dissipation rate.

• Korean Journal of Mathematics
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• 제23권3호
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• pp.439-446
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• 2015

In this paper we consider the meromorphic function G(z) with a pole of order 1 at -a and analytic function F(z) with a zero -a of order 2 in $\mathbb{D}=\{z :{\mid}z{\mid}<1\}$, where -1 < a < 1. From these functions we obtain the regular simply-connected minimal surface $S=\{(u(z),\;{\nu}(z),\;H(z)):z{\in}\mathbb{D}\}$ in $E^3$ and the harmonic function $f=u+i{\nu}$ defined on $\mathbb{D}$, and then we investigate properties of the minimal surface S and the harmonic function f.

• Structural Engineering and Mechanics
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• 제18권5호
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• pp.671-690
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• 2004

An assumed strain finite strip method(FSM) using the non-periodic B-spline for a shell is presented. In the present method, the shape function based on the non-periodic B-splines satisfies the Kronecker delta properties at the boundaries and allows to introduce interior supports in much the same way as in a conventional finite element formulation. In the formulation for a shell, the geometry of the shell is defined by non-periodic B3-splines without any tangential vectors at the ends and the penalty function method is used to incorporate the drilling degrees of freedom. In this study, new assumed strain fields using the non-periodic B-spline function are proposed to overcome the locking problems. The strip formulated in this way does not posses any spurious zero energy modes. The versatility and accuracy of the new approach are demonstrated through a series of numerical examples.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1690-1696
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• 2003

A two-dimensional direct numerical simulation is performed to investigate the flame structure of $CH_4/N_2$-Air counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman's detailed chemistry are adopted in this calculation. The results show that an initially flat stagnation plane, where an axial velocity is zero, is deformed into a complex-shaped plane, and an initial stagnation point is moved far away from vortex head when the counterflow field is perturbed by the vortex. It is noted that the movement of stagnation point can alter the mechanism of reactants (fuel and oxidizer) fluxes into the flame surface, and then can alter the flame structure.

• Tribology and Lubricants
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• 제10권4호
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• pp.69-74
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• 1994

The space world under zero gravity and super vacuum where the space machine works has only friction and inertia. Inertia of acceleration and diceleration is accurately obtained by computing while friction is always in contact surface and unsteady. The sur soundings under super vacuum make surface friction more complicate. [1,2]. Therefore, method to lubricate stably the contact surface for long term in space machine is very important and friction for space machine proves to be true by several accident of space projects. In spite of that accident, method of lubrication and lubricants to keep stablity for long term in space machine have not been established so far. Lubrication for space machine is very important and under developings over the world. In this study we suggest a new lubricating technology, which improves powerful for space machine.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.15-15
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• 2012

Mg(1-4)Zn 이원계 압출재 및 Mg5Sn(1-4)Zn 삼원계 압출재의 부식거동을 3.5 % NaCl 용액에서 다양한 전기화학기법을 이용하여 평가하였다. 이원계 합금에 대한 연구결과, Zn 함량 증가에 따라 Mg 모재의 부동태화가 촉진되었고 동시에 수소발생속도가 증가하였으며 그 결과 부식전위의 상승이 관찰되었다. 그러나 Zn 함량 증가에 따른 부동태화 효과보다 수소발생 증가 효과가 우세하므로 결과적으로 Zn 함량 증가에 따라 부식속도는 증가하였다. Mg5Sn(1-4)Zn 삼원계 합금에 대한 부식시험 결과, Mg5Sn2Zn 합금이 가장 낮은 부식속도 및 우수한 부동태화를 나타내었으며 이는 합금원소 Sn의 수소발생속도 감소효과와 합금원소 Zn의 부동태화 효과의 상호작용에 의한 것으로 사료된다.

• 대한수학회논문집
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• 제31권4호
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• pp.695-701
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• 2016

Let I and J be two ideals of a commutative Noetherian ring R and M, N be two non-zero finitely generated R-modules. Let t be a non-negative integer such that $H^i_{I,J}(N)$ is (I, J)-minimax for all i < t. It is shown that the generalized local cohomology module $H^i_{I,J}(M,N)$ is (I, J)-Cofinite minimax for all i < t. Also, we prove that the R-module $Ext^j_R(R/I,H^i_{I,J}(N))$ is finitely generated for all $i{\leq}t$ and j = 0, 1.