• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.439-443
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• 2011

Using the projection operator technique, a reduced density matrix theory for linear absorption spectrum of energy transfer systems is developed for the theoretical absorption line shape of the systems with non-Condon transitions. As an application, we considered a model system of OH vibrations of water. In the present model calculation, the OH vibration modes are coupled to each other via intra-molecular coupling mechanism while their intermolecular couplings are turned off. The time-correlation functions appearing in the formulation are calculated from a mixed quantum/classical mechanics method. The present theory is successful in reproducing the exact absorption line shape. Also the present theory was improved from an existing approximate theory, time-averaged approximation approach.

• 동력기계공학회지
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• 제5권4호
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• pp.44-52
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• 2001

This paper considers a modeling and identification for the MIMO magnetic bearing system. To obtain the nominal plant transfer functions, we have experimented on the frequency response by a closed-loop identification method because the system is unstable essentially. We suggest a method of curve-fitting for obtaining the transfer function from the frequency responses by using the system's modeling structure and two controllers which are different from each other. From the frequency response results, we found the effects of coupling by opposing controllers. And using this effects and the system's modeling structure, we could obtain the transfer functions of which have the same modularized denominators.

• 대한기계학회논문집
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• 제16권2호
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• pp.391-399
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• 1992

The analysis of the evaporative heat transfer in the inclined porous layer (0.deg.<.theta.<90.deg.) is made by using capillary model. The length of the evaporation zone is obtained numerically by integrating the differential equation using a Runge-Kutta algorithm. As a result, the length of the evaporation zone is inverse proportional to the dimensionless number, E(=Re*.phi./cos.theta.) representing the evaporation intensity, and the relationship of these parameters shows linear in the log graph.

• 한국응용과학기술학회지
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• 제14권1호
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• pp.89-93
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• 1997

In this research, ultra-thin films of organic charge transfer complex were deposited on to ordinary microscope slide-glass subtrates with a Langmuir-Blodgett technique. ${\pi}$-A isotherm characteristics of these complex were studied in order to find optimum conditions of deposition by varying temperature of subphase, compression speed, and spreading amount. Transfer ratio of these films were studied during the process of deposition. The UV-visible absorbance spectra of LB films were measured to find state of deposition by varing layer number. The observed optimum conditions of surface, pressure, spreading amount, and dipping speed for depositing LB films(Y-type) were 38m/Nm, $150{\mu}l$ and 5mm/min, respectively. Since the tansfer ratio is close to 100%, the monolayer on the subphase seems to be well transferred to the solid substrate. The thickness of the film was well-controlled as the UV-vis absorbance of films were changed linear according to the number of layers.

• 대한기계학회논문집B
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• 제26권1호
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• pp.141-149
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• 2002

A numerical simulation is performed for the cooling heat transfer of a heated cylindrical pedestal by an axisymmetric jet impingement. Based on the k- $\varepsilon$- f$\sub$${\mu}$/ model of Park et at., the linear and nonlinear stress-strain relations are extended. The Reynolds number based on the jet diameter(D) is fixed at Re$\sub$D/ = 23000. The local heat transfer coefficients are compared with available experimental data. The predictions by k- $\varepsilon$-f$\sub$${\mu}$/ model are in good agreement with the experiments, whereas the standard 7- f model does not properly resolve the flow structures.

• 전자공학회논문지B
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• 제30B권11호
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• pp.93-101
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• 1993

The transfer function of vector-controlled induction motor is represented along with both unstructured and structured uncertainty such as the error of rotor time constant and current ripple. The low-pass-filter behavior of a magnetizing inductance gets rid of unstructured uncertainty in the transfer function. The robust controller to compensate variation of the transfer function is designed using simple P-I linear controllers. The coefficients of speed PI controller are determined from an overshoot and a rising time of system and the coefficients of model-following PI controller are obtained using the solution of Riccati equation of LQR control in the state space equation of the error system. Experimental results with the DSP-based model-following robust controller are shown a good robustness against the structured uncertainty of the motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.911-914
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• 1998

This paper presents an algorithm that evaluates the transfer capability of composite power systems using probabilistic approaches. The reliability indices calculated by using probabilistic method are expected maximal flow, expected transfer capability margin, and expected power not supplied. In this paper, a successive linear programming technique is used to evaluate transfer capability named maximal flow. Physical constraints considered in the maximal flow problem are the limits of toad voltage, line overloading, and real & reactive power generation. Numerical results on IEEE RTS show that the proposed algorithm is effective and useful.

• Journal of Magnetics
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• 제14권3호
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• pp.101-103
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• 2009

The spin transfer torque efficiency was determined experimentally by observing the current-driven domainwall depinning of Pt/CoFe/Pt nanowires with perpendicular magnetic anisotropy. The depinning time was exponentially proportional to the applied magnetic field, and was well explained by the Neel-Brown formula. The depinning time and threshold magnetic field were varied considerably by injecting current into the nanowire. The spin transfer torque efficiency was estimated to be $(7.2{\pm}0.9){\times}10^{-15}Tm^2$/A from the linear dependence of the threshold current density with respect to the applied magnetic field.

• Macromolecular Research
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• 제12권1호
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• pp.32-37
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• 2004

The atom transfer radical polymerization (ATRP) of hexadecyl acrylate (HDA) was carried out in Ν,Ν-dimethylformamide (DMF) in the presence of CuSCN/Ν,Ν,Ν′,Ν"Ν"-pentamethyldiethylenetriamine (PMDETA). The results indicate that the polymerization is well-controlled: a linear increase of molecular weights occurs with respect to conversion and the polydispersities are relatively low. In particular, the use of CuSCN as the catalyst resulted in faster polymerization rates for hexadecyl acrylate than did those using either CuBr or CuCl; the polydis-persity, however, was larger than those obtained in the cases when CuBr and CuCl were used. In addition, we report the thermodynamic data and activation parameters for the solution ATRP of hexadecyl acrylate.

• 설비공학논문집
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• 제25권2호
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• pp.109-118
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• 2013

The absence of a simple and general analytical model has been a problem in the design and analysis of desiccant-assisted air-conditioning systems. In this study, such an analytical model has been developed based on the approximate integral solution of the coupled transient ordinary differential equations for the heat and mass transfer processes in a desiccant wheel. It turned out that the initial conditions should be determined by the solution of four linear algebraic equations including the heat and mass transfer equations for the air flow as well as the energy and mass conservation equations for the desiccant bed. It is also shown that time-averaged exit air temperature and humidity relations could be given in terms of the heat and mass transfer effectiveness.