• Bulletin of the Korean Chemical Society
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• 제10권5호
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• pp.430-433
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• 1989

Molecular reorientation of oblate symmetric top molecules in the presence of internal rotation is investigated and an analytic expression for the spin-rotational relaxation rate of a nucleus attached to the internal rotor is obtained as a function of the internal angular momentum correlation time. The overall reorientation of the symmetric top is treated by the anisotropic rotational diffusion and the internal rotation is assumed to undergo modified extended rotational diffusion. The result is compared with the previous work for the prolate symmetric top molecule and it is shown that both results reduce to the same expression in the spherical top limit.

• 한국광학회:학술대회논문집
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• 한국광학회 1989년도 제4회 파동 및 레이저 학술발표회 4th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.55-58
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• 1989

The methods of recording transient phenomena with picosecond or better resolution fall into two basic categories: those in which the detector itself prossesses adequate time resolution for the task at hand, and those in which the response of the system is sampled by examining the characteristics of a second pulse ("the probe") delayed in time from the initiating pulse ("the pump") as a function of time delay between pump and probe cases. In this case the time resolution is only limited by the pump-and probe-pulse durations. As an application of this time-resolved spectroscopic technique, the ultrafast orientational relaxation phenomena of the dye molecules are currently under investigation in our laboratory. In this presentation the status of our experiment is summarized.iment is summarized.

• ETRI Journal
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• 제41권5호
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• pp.619-625
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• 2019

In this paper, we propose an array pattern synthesis scheme using semidefinite programming (SDP) under array excitation power constraints. When an array pattern synthesis problem is formulated as an SDP problem, it is known that an additional rank-one constraint is generated inevitably and relaxed via semidefinite relaxation. If the solution to the relaxed SDP problem is not of rank one, then conventional SDP-based array pattern synthesis approaches fail to obtain optimal solutions because the additional rank-one constraint is not handled appropriately. To overcome this drawback, we adopted a bisection technique combined with a penalty function method. Numerical applications are presented to demonstrate the validity of the proposed scheme.

• 경영과정보연구
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• 제29권4호
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• pp.109-121
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• 2010

본 연구는 전형적인 차량경로 문제에서 각 노드간의 이동 시간이 일정하지 않은 특수한 경우의 상황에 대한 해법 절차를 제공한다. 본 연구는 상황에 따라 변화하는 이동시간을 갖는 외판원 문제의 특별한 경우인 '한 노드까지 도달한 경로가 다음 노드로 이동하는 데 걸리는 시간에 영향을 주는 외판원 문제'(경로의존 이동비용을 갖는 외판원 문제(RDTSP: Route Dependent Travelling Salesman Problem))의 해법을 제시한다. RDTSP 문제의 해결을 위해 먼저 문제 상황을 묘사하는 정수 계획 모형을 개발하였다. 본 연구에서 제시한 정수계획 모형에서는, 모든 가능한 경로에 대하여 각각의 경로를 하나의 변수로 정의하고 이 변수들 중에서 하나를 선택하는 형태로 개발되었다. 이 모형에서는 변수에 해당하는 가능한 경로의 수가 노드수에 지수적(exponentially)으로 증가하기 때문에, 처음부터 모든 변수를 문제에 포함시켜 풀 수 없게 된다. 그러나, 개발된 정수계획 모형의 변수를 실수로 완하시킨 선형완화(LP relaxation) 문제에 대해서는 열 생성(column generation) 기법을 통해 그 해를 구할 수 있다. 또한 본 연구의 결과가 PCB 조립 공정의 작업시간 최적화 문제에 어떻게 적용될 수 있는가를 제시한다.

• Korea-Australia Rheology Journal
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• 제21권4호
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• pp.203-211
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• 2009

In flows with deformation rates larger than the inverse Rouse time of the polymer chain, chains are stretched and their confining tubes become increasingly anisotropic. The pressures exerted by a polymer chain on the walls of an anisotropic confinement are anisotropic and limit chain stretch. In the Molecular Stress Function (MSF) model, chain stretch is balanced by an interchain pressure term, which is inverse proportional to the $3^{rd}$ power of the tube diameter and is characterized by a tube diameter relaxation time. We show that the tube diameter relaxation time is equal to 3 times the Rouse time in the limit of small chain stretch. At larger deformations, we argue that chain stretch is balanced by two restoring tensions with weights of 1/3 in the longitudinal direction of the tube (due to a linear spring force) and 2/3 in the lateral direction (due to the nonlinear interchain pressure), both of which are characterized by the Rouse time. This approach is shown to be in quantitative agreement with transient and steady-state elongational viscosity data of two monodisperse polystyrene melts without using any nonlinear parameter, i.e. solely based on the linear-viscoelastic characterization of the melts. The same approach is extended to model experimental data of four styrene-butadiene random copolymer melts in shear flow. Thus for monodisperse linear polymer melts, for the first time a constitutive equation is presented which allows quantitative modeling of nonlinear extension and shear rheology on the basis of linear-viscoelastic data alone.

• The Korean Journal of Physiology and Pharmacology
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• 제20권5호
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• pp.539-545
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• 2016

Nafamostat mesilate (NM), a synthetic serine protease inhibitor, has anticoagulant and anti-inflammatory properties. The intracellular mediator and external anti-inflammatory external signal in the vascular wall have been reported to protect endothelial cells, in part due to nitric oxide (NO) production. This study was designed to examine whether NM exhibit endothelium dependent vascular relaxation through Akt/endothelial nitric oxide synthase (eNOS) activation and generation of NO. NM enhanced Akt/eNOS phosphorylation and NO production in a dose- and time-dependent manner in human umbilical vein endothelial cells (HUVECs) and aorta tissues obtained from rats treated with various concentrations of NM. NM concomitantly decreased arginase activity, which could increase the available arginine substrate for NO production. Moreover, we investigated whether NM increased NO bioavailability and decreased aortic relaxation response to an eNOS inhibitor in the aorta. These results suggest that NM increases NO generation via the Akt/eNOS signaling pathway, leading to endothelium-dependent vascular relaxation. Therefore, the vasorelaxing action of NM may contribute to the regulation of cardiovascular function.

• 한국광학회지
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• 제1권2호
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• pp.149-154
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• 1990

$Tb^{3+}$이온을 첨가한 borosilicate 유리속에서 일어나는 에너지전달을 연구하기 위하여 $Tb^{3+}$이온의 농도에 따른 형광방출의 세기 및 $^5D_3$과 $^5D_4$ 준위의 형광수명시간을 측정.분석하였다. $Tb^{3+}$이온농도가 증가하면 cross-relaxation에 의해 $^5D_3$ 준위의 상태밀도가 줄어드는 대신에 $^5D_4$ 준위의 상태밀도가 증가했다. 그리고 이 상호작용은 전기 쌍극자-전기쌍극자 상호작용이며 임계작용거리는 13$\AA$이었다. 또 5D4 형광방출을 소광시키는 원인이 되는 $^5D_4$$\longrightarrow$$^5D_4$형의 에너지전달은 그 임계작용거리가 3.5$\AA$으로 나타났다.

• 한국자기공명학회논문지
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• 제22권4호
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• pp.107-114
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• 2018

In this exploration, the nuclear magnetic resonance of the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ Single Crystals using FT-NMR spectrometer is investigated. The line width of the resonance line for the $^{207}Pb$ nucleus decreases as temperature increases due to motional narrowing. The chemical shift of $^{207}Pb$ NMR spectra also increases as temperature decreases for both crystals. The spinlattice relaxation times $T_1$ of $^{39}K$ nucleus were calculated as a function of temperature (180 K~400 K). The $T_1$ of $^{207}Pb$ nucleus decreases as temperature increases. The dominant relaxation mechanism at the studied temperature range can be deduced as the Raman process, which is the coupling between lattice vibrations and the nuclear spins. This deduction is substantiated by the fact that the nuclear spin-lattice relaxation rate $1/T_1$ of the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ single crystal is proportional to $T^2$, or temperature squared. The activation energies for the $^{207}Pb$ nucleus in $PbWO_4:Mn^{2+}$ and $PbWO_4:Dy^{3+}$ single crystals are $E_a=49{\pm}1meV$ and $E_a=47{\pm}2meV$, respectively.

• 한국식품영양과학회지
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• 제35권7호
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• pp.847-852
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• 2006

KH204가 음경해면체 이완과 생식기능에 미치는 영향을 규명하기 위해 효능을 실험한 결과 토끼의 음경해면체를 $1{\times}10^{-6}M$ pheylephrine으로 수축시킨 후 KH204를 61, 183 및 549 mg/L의 축적용량으로 처리하여 각각 6.8, 10.1 및 16%의 용량의존적인 이완효과를 관찰하였다. 흰쥐를 이용한 생식기능 실험은 KH204를 61, 183 및 549 mg/kg으로 10주간 장기투여에서 생식장기인 고환조직의 중량 및 정자수 증가에 유의한 효과를 나타내었다. 정자 형태검사는 대조군과 비슷한 수치로 나타내어 고농도로 장기투여에도 정자군과 비슷한 수치로 나타내어 고농도로 장기투여에도 정자 기형에 문제가 없음을 확인하였다. 이상의 결과로 KH204가 특별한 부작용이 없이 음경해면체를 농도의존적으로 이완시키는 효과가 있어, 음경발기를 개선시키는 효과뿐만 아니라 고환성 원인 또는 정자생산 기능부전으로 보이는 남성불임에서 또한 효능이 있음을 시사하였다.

• 천문학회지
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• 제49권2호
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• pp.53-57
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• 2016

We present an optical UBVRI photometric analysis of the poorly studied open star cluster IC 2156 using Sloan Digital Sky Survey data in order to estimate its astrophysical properties. We compare these with results from our previous studies that relied on the 2MASS JHK near-infrared photometry. The stellar density distributions and color-magnitude diagrams of the cluster are used to determine its geometrical structure, real radius, core and tidal radii, and its distance from the Sun, the Galactic plane, and the Galactic center. We also estimate, the age, color excesses, reddening-free distance modulus, membership, total mass, luminosity function, mass function, and relaxation time of the cluster.