• 대한전자공학회논문지TC
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• 제45권7호
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• pp.67-71
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• 2008

본 논문에서는 Ka 대역에서 동작하는 송수신기에 쉽게 집적화 할 수 있는 프로브 구조를 이용한 도파관-마이크로스트립 트랜지션을 설계 및 제작하였다. 도파관-마이크로스트립 트랜지션은 프로브, 인덕턴스 선로, ${\lambda}/4$ 임피던스 변환기, 그리고 $50{\Omega}$ 마이크로스트립 선로로 구성되어있으며, 각 구성 요소들의 특성 임피던스 및 길이를 시뮬레이션을 통해 최적화하였다. 제작된 트랜지션의 측정결과, $30{\sim}40GHz$ 대역 내에서 평균 1.3 dB의 삽입손실 특성, 14 dB이하의 입출력 반사 손실특성을 나타내었다. 마이크로스트립 선로 및 입출력 도파관의 손실을 고려하여 하나의 변환 구조 당 삽입 손실은 $0.5{\sim}0.6dB$ 정도이다.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.980-986
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• 2012

In this paper we develop a minimalist model of single molecule spectroscopy in a dynamic environment. Our model is based upon a lattice system consisting of a probe molecule embedded in an Ising-model like environment. We assume that the probe molecule interacts with the Ising spins via a dipole-dipole potential, and calculate free energy curves and lineshapes of the system. To investigate fluctuation behavior of the system we exploit the metadynamics sampling method. In particular, using the method, we calculate the free energy curve of magnetization of the lattice and that of the transition energy of the probe molecule. Furthermore, we compare efficiencies of three different sampling methods used; unbiased, umbrella, and metadynamics sampling methods. Finally, we explore the lineshape behavior of the probe molecule as the system undergoes a phase transition from a sub-critical and to a super-critical temperature. We show that the transition energy of a probe molecule is broadly distributed due to the heterogeneous, local environments.

• 한국산업정보학회논문지
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• 제20권1호
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• pp.43-47
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• 2015

본 논문에서는 밀리미터파 모듈 응용을 위하여 광대역 마이크로스트립-대-웨이브가이드 (WR12) 천이기가 제시된다. 대역폭의 개선을 위하여 radial 마이크로 스트립 electrical-probe가 저 손실 유기 유전체 기판 위에 설계되었다. 제안된 천이기의 삽입 및 반사손실에 대한 설계 및 측정된 특성을 나타내었다. 측정을 위한 케이블 아답터와 웨이브가이드 천이기의 손실을 고려하면, 제안된 천이기의 천이 손실이 70 및 80 GHz에서 각각 -1.88 및 -2.01 dB로 분석되었다. 제안된 천이기의 -10 dB 반사 손실 대역폭은 67GHz 에서 95 GHz로 약 26 GHz이다. 최신의 연구결과와 비교해서 대역폭에서 8.3 % 개선되었다.

• 비파괴검사학회지
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• 제30권3호
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• pp.225-235
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• 2010

There are many types of the geometric transitions such as dent, bulge, protrusion, expansion, etc, on the inner and outer surfaces of heat exchanger tubes, steam generator tubes, and condenser tubes of nuclear power plants. Such geometric transition causes a local residual stress in heat exchanger tubes and acts as a structural factor accelerating the evolution of defects, in particular stress corrosion cracks. In the conventional eddy current test methods, the bobbin coil profilometry can provide 2-dimensional geometric information on the variation of the average inner diameter along the tube length, but the 3-dimensional distribution and the quantitative size of a local geometric transition existing in the tube cannot be measured. In this paper, a new eddy current probe, developed for the 3-dimensional profile measurement, is introduced and its superior performance is compared with that from the conventional bobbin coil profilometry for the various types of geometric transition. Also, the accuracy of the probe for the quantitative profile measurement is verified by comparing the results with that from the laser profilometry. It is expected that the new eddy current probe and techniques can be effectively used for an optimization of the tube expansion process, and the management of tubes with geometric transitions in service.

• 대한기계학회논문집
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• 제10권6호
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• pp.814-822
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• 1986

본 연구에서는 이러한 점에 착안하여 비가열수직이상유동계에서 전도Probe 를 이용하여 시간평균보이드율을 측정하여 이들로부터 통계적으로 처리된 확률밀도함 수(PDF)분포와 이와 관련된 일련의 모우멘트계산을 시도 하므로써 유동양식과 천이특 성에 대하여 객관적이고 체계적인 해석을 하였다. 또한 학계 및 산업계에서는 측정 기구의 단순화가 요구되므로 전도Probe의 출력신호를 분석하여 유동양식에 따르는 특 성을 아울러 구명하였다.

• 대한전자공학회논문지TC
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• 제49권4호
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• pp.47-52
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• 2012

본 논문에서는 200 GHz 대역의 시스템에 응용이 가능한 구형도파관 전송선로와 평면 구조인 마이크로스트립 전송선로 구조의 부품들의 상호 신호전달을 위해 프로브 구조의 변환기를 설계하였다. 설계된 변환기는 프로브, 임피던스 변화를 위한 테이퍼구조와 마이크로스트립 구조의 전송선로로 구성된다. Ansoft사의 HFSS 시뮬레이션 툴을 이용하여 프로브의 크기 및 테이퍼의 길이를 변경하여 주파수 특성 변화를 확인하였으며 최적화하였다. 변환기는 특성 검증을 위해 back-to-back 구조로 설계되었으며, 시뮬레이션 결과 186 GHz ~ 210 GHz의 대역폭을 갖으며 전 대역에서 - 0.81 dB 이하의 삽입손실과 -10 dB 이상의 반사손실을 확인하였다.

• 한국표면공학회지
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• 제50권3호
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• pp.141-146
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• 2017

We investigated configuration of metallic and insulating domains in $VO_2$ thin films, while spanning metal-insulator phase transition. Kelvin probe force microscopy, of which spatial resolution is less than 100 nm, enables us to measure local work function (WF) at the sample surface. The WF of $VO_2$ thin films decreased (increased) as increasing (decreasing) the sample temperature, during the phase transition. The higher and lower WF regions corresponded to the insulating and metallic domains, respectively. The metallic fraction, estimated from the WF maps, well explained the temperature-dependent resistivity based on the percolation model. The WF mapping also showed us how the structural defects affected the phase transition behaviors.

• ETRI Journal
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• 제21권2호
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• pp.1-8
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• 1999

We analyze the characteristics of a coaxial-to-waveguide transition based on the finite difference time domain (FDTD) method with the cylindrical to rectangular cell interpolation scheme. The scheme presented in this paper is well suited for the analysis of a microwave device with a probe near waveguide discontinuity because perfect TEM mode can be generated inside the coaxial cable by using the cylindrical cell. The scattering parameters of a designed Ka-band transition are evaluated and compared with those of commercially available software, High Frequency Structure analysis Simulator (HFSS) and measured data. There exists good agreement between the measured and calculated data. In order to prove an accuracy of the interpolation scheme, a coaxial to waveguide transition with a disk-loaded probe is analyzed by the present approach and the results of this analysis are compared with measured data. Comparison shows that our results match very closely to those of measurement and other approaches. The method presented in this paper can be applied to analyze the characteristics of a probe excited cavity, coaxial waveguide T-Junctions, and so on.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1554-1560
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• 2008

The probe diffusion and friction constants of methyl yellow (MY) in liquid n-alkanes of increasing chain length were calculated by equilibrium molecular dynamics (MD) simulations at temperatures of 318, 418, 518 and 618 K. Lennard-Jones particles with masses of 225 and 114 g/mol are modeled for MY. We observed that the diffusion constant of the probe molecule follows a power law dependence on the molecular weight of nalkanes, DMY${\sim}M^{-\gamma}$ well. As the molecular weight of n-alkanes increases, the exponent $\gamma$ shows sharp transitions near n-dotriacontane ($C_{32}$) for the large probe molecule (MY2) at low temperatures of 318 and 418 K. For the small probe molecule (MY1) $D_{MY1}$ in $C_{12}$ to C80 at all the temperatures are always larger than Dself of n-alkanes and longer chain n-alkanes offer a reduced friction relative to the shorter chain n-alkanes, but this reduction in the microscopic friction for MY1 is not large enough to cause a transition in the power law exponent in the log-log plot of DMY1 vs M of n-alkane. For the large probe molecule (MY2) at high temperatures, the situation is very similar to that for MY1. At low temperatures and at low molecular weights of n-alkanes, $D_{MY2}$ are smaller than $D_{self}$ of n-alkanes due to the relatively large molecular size of MY2, and MY2 experiences the full shear viscosity of the medium. As the molecular weight of n-alkane increases, $D_{self}$ of n-alkanes decreases much faster than $D_{MY2}$ and at the higher molecular weights of n-alkane, MY2 diffuses faster than the solvent fluctuations. Therefore there is a large reduction of friction in longer chains compared to the shorter chains, which enhances the diffusion of MY2. The calculated friction constants of MY1 and MY2 in liquid n-alkanes supported these observations. We deem that this is the origin of the so-called“solventoligomer”transition.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.74.1-74.1
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• 2007