• 한국해안해양공학회지
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• 제19권5호
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• pp.408-417
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• 2007

최근, 해수욕장으로서의 기능 창출 뿐만 아니라 해안공간의 이용 및 개발에 따른 자연해변의 소실을 대체할 수 있는 인공해변이 건설되고 있다. 그리고, 파랑작용에 의한 매립토사의 유출로부터 인공해변을 보호하기 위한 구조물이 필요하며, 일반적으로 호안이 주로 건설된다. 해저지반 상부에 건설되는 호안의 안정성을 위하여 필히 검토되어야 할 사항 중의 하나가 호안 배후의 지하수위 거동이다. 그러나, 비선형파랑과 지하수위의 거동특성이 인공해변의 토사유출 및 구조물의 안정성에 중요한 요소로 작용함에도 불구하고 이에 대한 연구는 거의 수행되지 않았다. 본 연구에서는 비선형파랑과 호안 및 지하수위로 인한 흐름간의 동적 상호작용을 살펴보기 위하여 정수위와 지하수위와의 차이를 고려할 수 있는 수치파동수로를 개발하였다. 개발된 수치파동수로를 이용하여, 지하수위 변화가 호안 주변 지반내의 수리학적 특성에 미치는 영향을 살펴보았고, 지하수위의 변화에 따른 파동장 및 간극수 흐름, 간극수압 및 와도를 수치적으로 재현하였다. 결과로부터 지하수위의 변화에 따른 호안 주변 지반내의 수리학적 특성들이 어떻게 영향을 받는지 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3099-3102
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• 2010

A label-free DNA detection method was developed for a simple electrochemical DNA sensor with a short assay time. Self-assembled monolayers of peptide nucleic acid were used as a probe on gold electrodes. The formation of the self-assembled monolayers on the gold electrodes was successfully checked by means of cyclic voltammetry. The target DNA, hybridized with peptide nucleic acid, can be detected by the anodic peak current of ferrocene dendrimers, which interact electrostatically with the target DNA. This anodic peak current was measured by square wave voltammetry at 0.3 V to decrease the detection limit on the order of the nanomolar concentrations. As a result, the label-free electrochemical DNA sensor can detect the target DNA in concentrations ranging from 1 nM to $1\;{\mu}M$ with a detection limit of 1 nM.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1321-1325
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• 2004

Sodium dodecyl sulfate (SDS), an anionic surfactant, can strongly adsorb at the surface of a carbon paste electrode (CPE) via the hydrophobic interaction. In pH 3.0 $Na_2HPO_4$-citric acid buffer (Mcllvaine buffer) and in the presence of SDS, the cationic indole-3-acetic acid (IAA, $pK_a$ = 4.75) was highly accumulated at the CPE surface through the electrostatic interaction between the negative-charged head group of SDS and cationic IAA, compared with that in the absence of SDS. Hence, the oxidation peak current of IAA increases greatly and the oxidation peak potential shifts towards more negative direction. The experimental parameters, such as pH, varieties of surfactants, concentration of SDS, and scan rate were optimized for IAA determination. The oxidation peak current is proportional to the concentration of IAA over the range from $5\;{\times}\;10^{-8}$ mol/L to $2\;{\times}\;10^{-6}$ mol/L. The detection limit is $2\;{\times}\;10^{-8}$ mol/L after 3 min of accumulation. This new voltammetric method was successfully used to detect IAA in some plant leaves.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.123-126
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• 2002

Very frequently the compressible flow in an extinction nozzle of gas circuit breaker is simulated under no arc assumption, which can be reasonable for both high and low current breakings. In the present study, computations are performed to investigate the major features of the compressible flows inside the arc extinction nozzle of gas circuit breaker. A fully implicit finite volume scheme is applied to solve the two-dimensional, steady, compressible, Wavier-Stokes equations. The computed results are validated with the previous experimental data available. Several types of turbulence models are explored to reasonably predict the complicated flows inside the arc extinction nozzle. The obtained results show that the shock wave boundary layer interaction inside the nozzle significantly influences the whole performance of the gas breaker.

• Ocean Systems Engineering
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• 제10권4호
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• pp.399-414
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• 2020

A floating bridge is an innovative solution for deep-water and long-distance crossing. This paper presents a curved floating bridge's dynamic behaviors under the wind, wave, and current loads. Since the present curved bridge need not have mooring lines, its deep-water application can be more straightforward than conventional straight floating bridges with mooring lines. We solve the coupled interaction among the bridge girders, pontoons, and columns in the time-domain and to consider various load combinations to evaluate each force's contribution to overall dynamic responses. Discrete pontoons are uniformly spaced, and the pontoon's hydrodynamic coefficients and excitation forces are computed in the frequency domain by using the potential-theory-based 3D diffraction/radiation program. In the successive time-domain simulation, the Cummins equation is used for solving the pontoon's dynamics, and the bridge girders and columns are modeled by the beam theory and finite element formulation. Then, all the components are fully coupled to solve the fully-coupled equation of motion. Subsequently, the wet natural frequencies for various bending modes are identified. Then, the time histories and spectra of the girder's dynamic responses are presented and systematically analyzed. The second-order difference-frequency wave force and slowly-varying wind force may significantly affect the girder's lateral responses through resonance if the bridge's lateral bending stiffness is not sufficient. On the other hand, the first-order wave-frequency forces play a crucial role in the vertical responses.

• 한국해안해양공학회지
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• 제4권2호
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• pp.63-71
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• 1992

연흔(ripple)이 발랄할 수 있는 이동상 해저면에서 파낭과 해류가 함께 작용할 때의 마찰력을 구하는 해법을 개발하였다. 본 해법에서 연흔의 형상에 대한 판별은 경험식을 이용하였다. 해법의 주요 골격은 프란틀의 혼합거리리논이며 해류의 감속률을 구하기 위한 확산계수비를 계산할 때 임의각의 합성영향을 고려하였으며, 모든 수치적분식의 解는 약산식으로 표현하여 계산효율을 증진시켰다. 또한 연흔을 고려하여 구한 마찰력을 기존 토사이동양 산정식에 적용하였으며 이를 발표된 실험자료와 비교하여 보았다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권11호
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• pp.538-543
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• 2006

A high-Power continuous-wave (CW) ten-vane double-strapped magnetron oscillator has been investigated using three-dimensional (3D) particle-in-cell (PIC) numerical simulation code, MAGIC3D. The resonant modes and their resonant frequencies of the ten-vane strapped magnetron resonator were obtained to show a large mode separation near the ${\pi}$-mode. An electron cloud formed in an anode-cathode gap, called an interaction space was confined well enough to result in no leakage current. Five spokes were clearly observed in the electron cloud, which definitely ensured the ${\pi}$-mode oscillation in the ten-vane magnetron. Numerical simulations predicted that the saturated microwave output power measured at the coaxial output port was 5.41 kW at the microwave frequency of 893 MHz, corresponding to a power conversion efficiency of 72.6% when the external axial magnetic field was 1150 gauss and the electron beam voltage and current were 6 kV and 1.25 A, respectively.

• 한국통신학회논문지
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• 제22권12호
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• pp.2736-2743
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• 1997

본 논문에서는 확장된 시간 영역 유한 차분 알고리듬을 적용해서 초고주파 증폭기를 전파 해석하였다. 증폭기에 포함된 능동 소자는 등가 전류원을 이용해서 모델링하였다. 등가 전류원은 전자기파와 능동 소자와의 상호 작용을 특정지어 주고 시간 영역 유한 차분 알고리듬에 적용할 수 있게 해준다. 이를 확인하기 위하여 실제로 증폭기를 제작하고, 측정한 결과와 시간 영역 유한 차분법으로 해석한 결과가 잘 일치함을 보였다.

• Current Optics and Photonics
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• 제1권3호
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• pp.203-206
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• 2017

We report a passive Q-switching of an all-fiber erbium-doped fiber laser delivering high pulse energy by using a high quality single-walled carbon nanotube saturable absorber (SWCNT-SA). A side-polished fiber coated with the SWCNT is employed as an in-line SA for evanescent wave interaction between the incident light and the SWCNT. This lateral interaction scheme enables a stable Q-switched fiber laser that generates high pulse energy. The central wavelength of the Q-switched pulse laser was measured as 1560 nm. A repetition rate frequency of the Q-switched laser is controlled from 78 kHz to 190 kHz by adjusting the applied pump power from 124 mW to 790 mW. The variation of pulse energy from 51 nJ to 270 nJ is also observed as increasing the pump power. The pulse energy of 270 nJ achieved at maximum pump power is 3 times larger than those reported in Q-switched all-fiber lasers using a SWCNT-SA. The tunable behaviors in pulse duration, pulse repetition rate, and pulse energy as a function of pump power are reported, and are well matched with theoretical expectation.

• Water Engineering Research
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• 제3권3호
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• pp.203-213
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• 2002

A wide-angle parabolic approximation equation model considering the interaction between wave and current is employed to simulate the deformation of irregular waves over a submerged shoal. It is found that the model gives qualitative agreements with experimental data for the cases of breaking waves around the shoal. Thus, the effect of breaking-induced current on the refraction-diffraction of waves is well understood.