• 자연과학논문집
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• 제17권1호
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• pp.31-37
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• 2006

We have found that the polarization mode coupling between the orthogonally linearly polarized dual mode laser results from the anisotropy of dipole moments. Rate equation analysis demonstrated that high anisotropy in dipole moment components can give rise to law intrinsic mode coupling constants while isotropic dipole moment components give high intrinsic mode coupling constant. The populations at active ion sites are shown to self-organize the populations such that laser mode gain is constant adove threshold while the gain contributions from the each site adjust themselves with pump power.

• ETRI Journal
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• 제31권5호
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• pp.610-612
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• 2009

We present intra-mixture prediction (IMP) mode for intra prediction and an enhanced estimation method for most probable mode (MPM). IMP mode supports more flexibility in intra prediction by mixing $4{\times}4$ blocks and $8{\times}8$ blocks in one macroblock, while the enhanced MPM estimation extends the number of referenced neighboring blocks and efficiently uses their prediction modes depending on their positions. Simulation results show that the combination of both proposed methods provides a bit reduction in the Bj${\phi}$ntegaard delta bitrate by an average of 2.56% compared to H.264/AVC.

• 한국연소학회지
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• 제12권4호
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• pp.31-38
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• 2007

An numerical study was conducted on superdetonative mode ram accelerator with length extended combustor. The computation condition was based on ISL's RAMAC30 II S225 experiment. For 50% length increased combustor, flame is not sustained. For the case of 60% and 70% increase, flame is successfully sustaind. But detonation wave is oscillating and acceleration is fluctuating. Extention of combustor is helpful for sustaing detonation wave but it may cause unstart.

• 환경위생공학
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• 제9권2호
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• pp.24-31
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• 1994

Aerosol size distribution were determined in Seoul by Anderson sampler from October 1989 to September 1991 for the major ionic species(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, Cl$^{-}$, Na$^{+}$, Na$^{+}$, K$^{+}$, Ca$^{2+}$ and Mg$^{2+}$) and TSP( Total Suspended Particles ). The seasonal variations in concentrations and size distribution have been investigated. The size distributions of TSP and each of ionic species were bimodal throughout the year. The size distribution of these ions were divided as follows; (1) fine- mode dominant for SO$_{4}$$^{2-}$ and N%'. (2) coarse- mode dominant for NO$_{3}$$^{-}$, Cl$^{-}$, Ca$^{2+}$ and Mg$^{2+}$. (3) both- mode dominant for TSP.

• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1374-1378
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• 2008

Using DFT B3LYP/6-31+G(d,p)//B3LYP/6-31G(d,p) calculation method, stable molecular structures were optimized for the p-tert-butylcalix[4]arene functionalized at lower rim by cage-annulated crown ether (1) in two different conformers and their potassium-ion complexes. Cone conformer of free host 1 was slightly more stable than partial-cone conformer. For two different kinds of complexation mode, the potassium ion in benzene-rings (bz) pocket showed comparable complexation efficiency with the cation in cage-annulated crown-ether (cr) for the cone and partial-cone conformers of 1. The complex (1${\bullet}K^+$) in the cr-binding mode for the partial-cone conformer was more stable than the cone conformer for B3LYP/6-31G(d,p) geometry optimization. However, $1_{(cone)}{\bullet}K^+$(cr) showed lower single-point energy than the $1_{(pc)}{\bullet}K^+$(cr) for B3LYP/6- 31+G(d,p) calculation method.

• 한국항공우주학회지
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• 제31권3호
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• pp.85-94
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• 2003

대부분의 위성들이 휠을이용한 자세제어를 수행하면서 축적된 휠모멘텀을 안정 영역으로 변동하기 위해 덤핑모드를 고려하고 있으며, 정지궤도위성의 경우에는 궤도위치유지를 위해 주기적으로 궤도조정 추력기를 동작시키면서 발생되는 자세오차를 휠 또는 자세제어 추력기를 이용하는 위치유지모드를 고려한다. 본 연구에서는 이와 같은 정지궤도위성의 임무특성을 이용하여 휠모멘텀 관리 로직을 개발하고 무궁화위성 3호 자세제어계에 적용하여 그 성능을 검증하였다.

• 전력전자학회논문지
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• 제19권1호
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• pp.31-40
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• 2014

This paper describes an optimal configuration for multi-central inverters in a medium-voltage (MV) grid, which is suitable for large-scale photovoltaic (PV) power plants. We theoretically analyze a proposed common-mode equivalent model for problems associated with multi-central transformerless-type three-phase full bridge(3-FB) PV inverters employing two-winding MV transformers. We propose a synchronized PWM control strategy to effectively reduce the common-mode voltages that may simultaneously occur. In addition, we propose that the existing 3-FB topology may also have the configuration of a multi-central inverter with a two-winding MV transformer by making a simple circuit modification. Simulation and experimental results of three 350kW PV inverters in a multi-central configuration verify the effectiveness of the proposed synchronization control strategy. The modified transformerless-type 3-FB topology for a multi-central PV inverter configuration is verified using an experimental prototype of a 100kW PV inverter.

• Steel and Composite Structures
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• 제31권2호
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• pp.113-123
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• 2019

In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of $8.5g/m^2$ to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites.

• 정보보호학회논문지
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• 제31권6호
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• pp.1237-1246
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• 2021

본 논문은 AES 블록 암호에 OFB(Output Feedback) 모드를 적용한 ATM(Asynchronous Transfer Mode) 셀 보안에 관한 것이다. ATM 셀은 사용자 데이터 셀과 유지 보수 셀로 구분되며 각 셀의 크기는 53 옥텟이며 5 옥텟의 헤더와 48 옥텟의 페이로드로 구성되어 있다. ATM 셀의 암호화/복호화를 위해서는 셀의 경계를 감지해야 하는 데 이는 헤더 내의 HEC(Header Error Control)필드를 이용하여 가능하다. 셀의 경계를 감지한 후에는 사용자 셀만 암호화하기 위하여 PT(Payload Type)코드를 이용하여 페이로드의 종류를 감지한다. 본 논문에서는 ISO 9160의 요구사항을 만족하는 ATM 셀의 보안 방법을 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.280-282
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• 1994

This paper proposes sliding mode state for robust speed control of induction motor. Sliding mode state observer is robust for measurement noise, modeling-error and load disturbance. The pole of sliding mode state observer can be placed at (0,0) in Z-plane for fast response. This method is, namely, deadbeat control. Sliding mode state observer output is discontinuous on a switching hyperplance, that causes harmful effects such as current harmonics and speed oscillation. In this paper, also the reducing method of the chattering of sliding mode state observer output is proposed. The proposed system is digitally implemented with TMS320C31.