• Journal of the Korean Chemical Society
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• v.63 no.3
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• pp.151-159
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• 2019

The TADF properties for carbazol-dicyanobenzene, carbazol-diphenyl sulfone, carbazol-benzonitrile derivatives as OLED candidate materials are theoretically investigated using density functional theory (DFT) with $6-31G^{**}$, cc-pVDZ, and cc-pVTZ basis sets. The optimized geometries, harmonic vibrational frequencies, and HOMO-LUMO energy separations are predicted at the B3LYP/$6-31G^{**}$ level of theory. The harmonic vibrational frequencies of the molecules considered in this study show all real numbers implying true minima. The time dependent density functional theory (TD-DFT) calculations have been also applied to investigate the absorption and emission wavelength (${\lambda}_{max}$), energy differences (${\Delta}E_{ST}$) between excited singlet ($S_1$) and triplet ($T_1$) states of candidate materials.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.8
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• pp.19-27
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• 2016

Nowadays the adaptive buffering techniques for burst stream packet configuration and its operation algorithm to save energy in IP core network have been studied. This paper explains the selection method of packet buffering interval for energy saving when configuring burst stream packet at the ingress router in IP core network. Especially the adaptive buffering interval and its implementation scheme are required to improve the energy saving efficiency at the input part of the ingress router. In this paper, we propose the best adaptive buffering scheme that a current buffering interval is adaptively buffering scheme based on the input traffic of the past buffering interval, and analyze its characteristics of energy saving and end-to-end delay by computer simulation. We show the improvement of energy saving effect and reduction of mean delay variation when using an appropriate inverse-function selecting the buffering interval for the configuration of burst stream packet in this paper. We confirm this method have superior properties compared to other method. The proposed method shows that it is less sensitive to the various input traffic type of ingress router and a practical method.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.29-34
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• 2014

We introduce a number of antenna optimization problem for the zero-forcing beamforming (ZFBF) scheme to enhance energy-efficiency (EE) of the multiple-input-multiple-output broadcast channel. For proposed optimization problem, we assume an instantaneous channel gain of the ZFBF scheme as an average channel gain, given by $N_a-K+1$, in order to reduce a computational complexity of finding the number of active antennas $N_a$. Then, we convert a fractional-form objective function into a subtractive-form, and find a solution of $N_a$ and the maximum EE by an iterative process. Simulation results show that the maximum EE value obtained by proposed algorithm is almost identical to the optimal EE value by the exhaustive search method.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.99-108
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• 2022

Among induced polarization (IP) methods, spectral IP (SIP) uses alternating current as a transmission source to measure amplitudes and phase of complex electrical resistivity at each source frequency, which disperse with respect to source frequencies. The frequency dependence, which can be explained by a relaxation model such as Cole-Cole model or equivalent models, is analyzed to estimate SIP parameters from dispersion curves of complex resistivity employing multi-objective optimization (MOO). The estimation uses a generic algorithm to optimize two objective functions minimizing data misfits of amplitude and phase based on Cole-Cole model, which is most widely used to explain IP relaxation effects. The MOO-based estimation properly recovered Cole-Cole model parameters for synthetic examples but hardly fitted for the real laboratory measures ones, which have relatively smaller values of phases (less than about 10 mrad). Discrepancies between scales for data misfits of amplitude and phase, used as parameters of MOO method, and it is in necessity to employ other methods such as machine learning, which can deal with the discrepancies, to estimate SIP parameters from dispersion curves of complex resistivity.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1927-1929
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• 2004

현재 널리 쓰이는 고밀도 플라즈마 장치의 식각 시뮬레이션은 식각 패턴으로는 level set method이며 바이어스가 인가된 sheath model로는 Riley sheath model 이 보편적으로 받아들여지고 있다. 이러한 식각 시뮬레이션은 RF(Radio Frequency) sheath로부터 가속된 이온이 단위 입체각당 특정 지점에 이온 플럭스 분포함수, 이온 에너지 분포함수와, 중성종의 수송모델로 etch rate을 결정하는 과정과 level set method을 이용하여 식각 형태를 계산하는 과정으로 구성되어있다. 본 연구는 식각 형태 계산 이전의 단계로서 $Ar^+,\;Cl_2{^+},\;Cl^+$이온의 유동속도와 밀도를 장치의 radial방향으로 불균일하게 가정하였고, 가정한 값으로 이온 플럭스와 에너지 플럭스에 대한 영향을 알아보았다.

• Journal of the Korean Chemical Society
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• v.23 no.2
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• pp.75-79
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• 1979

The frontier orbital energy, superdelocalizability and charge density of a series of benzologous pyridine ligands have been calculated by using HMO. According to ${\Delta}E_{\pi}$ of ligands on the basis of the above results, it is concluded that the stabilities are in the order of 1,10-Phen > 4,5-Phen > 1,5-Phen > 8-Hox > Hox-azoquinolinato. And also, the reactivities of electrophilic, nucleophilic and radical reaction, and bond strength have been respectively studied by superdelocalizabilities and charge densities.

• Computational Structural Engineering
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• v.6 no.3
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• pp.89-97
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• 1993

General formulation to analyse the rectangular thin plate on a soil medium by energy method is developed. In the problem, Boussinesque's formular needs to be integrated after assuming the contact stress distribution. Two different functions, i.e., power series and Chebychev polynomials are used to approximate the contact stress distribution. It was found that Chebychev polynomials are better function to describe the contact stress than power series. Chebychev polynomials considering stress singularity around plate boundary is recommended as the desirable shape function for future research.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.5-5
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• 1998

수정된 연소 반응 함수를 이용하여 복사 열속 교란에 대한 연소 반응 특성을 살펴보았다. Catalyzed DB N5 추진제의 연소 반응을 살펴보기 위하여 Son 등의 실험 결과와 비교하였다. Son 등의 연소 반응 함수는 물리적으로 타당하지 않은 활성화 에너지에서 실험 결과를 예측하였지만, 수정된 연소 반응 함수는 비슷한 추진제의 실제 활성화 에너지 범위에서 복사 열속에 대한 연소율의 반응을 비교적 잘 예측할 수 있었다. 이것은 Son 등에 의해 과소 평가된 복사 열속(f, J)의 영향이 고려되었기 때문인 것으로 판단된다. 민감 변수(sensitivity parameter)들을 구하기 위하여 Ibiricu 등이 제시한 정상 연소 관계식을 이용하였다. AP계 추진제의 표면 온도에 대한 정상 연소율 변화를 살펴본 결과 Zanotti의 AP2 추진제의 실험 결과와 정성적으로 비슷한 경향을 나타내었다.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.60-66
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• 1992

The electronic subband structure and the envelope wave function for three types of superlattices are calculated with a new method. Comparison of the results of this method with those of other methods has proved the validity of this method. In particullas, the results of saw-toothed superlattices show that the change of the effective mass with position must be considered. Therefore this method can be easily applied to arbitrily shaped superlattices and multiple quantum well structures.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.05a
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• pp.199-206
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• 1995

200kW급 가스엔진 열병합시스템에서 엔진 냉각수는 엔진을 냉각시키는 기능 뿐아니라 배열회수용 열원으로 사용된다. 전력부하나 냉·난방 부하가 변할 때 엔진 냉각수의 온도가 민감하게 변하므로 이를 일정하게 제어하기 위하여 PID 제어기를 사용하고 있다. 본 연구는 이 제어기의 적정 이득값(gain)을 설정하기 위하여 공정 전달함수를 실험적방법을 이용하여 일차시간지연함수(First Order Plus Dead Time)로 근사한 후 여러 조율방법을 사용하여 이득값을 구하였다. 이 이득값과 전달함수를 가지고 공정모사기인 “MATLAB”을 사용하여 시스템에 적합한 적정이득값을 선정 하였으며 실증실험 결과 시스템의 온도동특성이 안정됨을 보였다.