• 한국통신학회논문지
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• 제19권3호
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• pp.425-433
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• 1994

종래부터 CATV 및 MATV 시스템에서 신호전송용으로 널리 사용되고 있는 Tap-off는 단지 경험직+실험적으로 제작되러 왔으며, 이론적인 해석이나 엄밀한 설계법이 확립되어 있지 않았기 때문에 그 성능에 있어서도 대역폭이 좁거나 분기특성이 나쁜 문제점이 있었다. 따라서, 본 논문에서는 원형의 약결합형 신호분기기에 보조변성기가 부가된 변형된 약결합형 신호분기기들 제안하여 설계의 자유도를 높임으로써 대단히 조밀한 결합간격의 회로구성이 가능함을 밝히고, 또한 이들에 대한 이론적 주파수특성을 계산하여 신험치와 비교함으로써 제안한 설계법의 타당성을 확인하였다.

• Journal of electromagnetic engineering and science
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• 제16권4호
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• pp.219-224
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• 2016

In this paper, coupled-mode theory (CMT) is used to obtain a transient solution analytically for a wireless power transfer system (WPTS) when unit energy is applied to one of two resonators. The solutions are compared with those obtained using equivalent circuit-based analysis. The time-domain CMT is accurate only when resonant coils are weakly coupled and have large quality factors, and the reason for this inaccuracy is outlined. Even though the time-domain CMT solution does not describe the WPTS behavior precisely, it is accurate enough to allow for an understanding of the mechanism of energy exchange between two resonators qualitatively. Based on the time-domain CMT solution, the critical coupling coefficient is derived and a criterion is suggested for distinguishing inductive coupling and magnetic resonance coupling of the WPTS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.2109-2109
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• 2011

High power microwave sources operating in relativistic regions, high current reletivistic electron beams are obtained by using cold cathodes with the help of explosive emission. For these relativistic devices, the pulsed power and magnetic field systems are very large and heavy. The phase velocity of electromagnetic mode should be showed down close to the beam velocity, ensuring enough beam coupling with electromagnetic modes. By using the annular electron beam, a weakly relativistic oversized bwo consisting of rectangularly corrugated cylindrical waveguide is demonstrated.

• Bulletin of the Korean Chemical Society
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• 제3권1호
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• pp.1-4
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• 1982

A quantitative treatment of ${\pi}$-nonbonded and $n-{\sigma}^{\ast}$ interactions and through-bond coupling effect was attempted using n-butane, n-butyl radical, and tetramethylene diradical. Results of STO-3G level calculations showed that: (1) conformational preferences can be predicted quantitatively based solely on the additive effect of ${\pi}$-nonbonded and $n-{\sigma}^{\ast}$ interactions, the predominant effect being the ${\pi}$-nonbonded interactions, (2) $(n-{\sigma}^{\ast})_{anti}$ is destabilizing whereas $(n-{\sigma}^{\ast})_{syn}$ is weakly stabilizing, which are contrary to what we expect from the normal $n-{\sigma}^{\ast}$ interaction, (3) througb-bond coupling of the two radical lobes is destabilizing for the triplet but stabilizing for the singlet tetramethylene diradical.

• Ocean Systems Engineering
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• 제8권4호
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• pp.381-407
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• 2018

This paper presents a hybrid numerical approach, which combines a two-phase Navier-Stokes model (NS) and the fully nonlinear potential theory (FNPT), for modelling wave-structure interaction. The former governs the computational domain near the structure, where the viscous and turbulent effects are significant, and is solved by OpenFOAM/InterDyMFoam which utilising the finite volume method (FVM) with a Volume of Fluid (VOF) for the phase identification. The latter covers the rest of the domain, where the fluid may be considered as incompressible, inviscid and irrotational, and solved by using the Quasi Arbitrary Lagrangian-Eulerian finite element method (QALE-FEM). These two models are weakly coupled using a zonal (spatially hierarchical) approach. Considering the inconsistence of the solutions at the boundaries between two different sub-domains governed by two fundamentally different models, a relaxation (transitional) zone is introduced, where the velocity, pressure and surface elevations are taken as the weighted summation of the solutions by two models. In order to tackle the challenges associated and maximise the computational efficiency, further developments of the QALE-FEM have been made. These include the derivation of an arbitrary Lagrangian-Eulerian FNPT and application of a robust gradient calculation scheme for estimating the velocity. The present hybrid model is applied to the numerical simulation of a fixed horizontal cylinder subjected to a unidirectional wave with or without following current. The convergence property, the optimisation of the relaxation zone, the accuracy and the computational efficiency are discussed. Although the idea of the weakly coupling using the zonal approach is not new, the present hybrid model is the first one to couple the QALE-FEM with OpenFOAM solver and/or to be applied to numerical simulate the wave-structure interaction with presence of current.

• 대기
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• 제29권2호
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• pp.219-226
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• 2019

Generally, the weather forecast system has been run using prescribed ocean condition. As it is widely known that coupling between atmosphere and ocean process produces consistent initial condition at all-time scales to improve forecast skill, there are many trials on the application of data assimilation of coupled model. In this study, we implemented a weakly coupled data assimilation (short for WCDA) system in global NWP model with low horizontal resolution for coupled forecast with uncoupled initialization, following WCDA system at the Met Office. The experiment is carried out for a typhoon evolution forecast in 2017. Air-sea exchange process provides SST cooling and gives a substantial impact on tendency of central pressure changes in the decaying phase of the typhoon, except the underestimated central pressure. Coupled data assimilation is a challenging new area, requiring further work, but it would offer the potential for improving air-sea feedback process on NWP timescales and finally contributing forecast accuracy.

• 대한전자공학회논문지
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• 제24권1호
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• pp.115-122
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• 1987

In this paper, we proposed an improved weakly-coupled power divider(TAP UNIT) for CATV and/or MATV systems, by which the degree of freedom in design and density of coupling interval are signifcantly increased compared with the intrinsic one even though the turn ratios are still of discrete values. On the other hand, the new design theory of a generalized n-way power divider with arbitrary dividing ratios, for CATV and/or MATV systems, which consists of ideal multiwinding transformers and resistors only was presented. Since the circuit elements is not frequency dependent, the proposed power divider is to be of considerably broad bandwidth. Furthermore, the experimental verification has been achieved, and, hence, the validity of the design theory proposed here is confirmed.

• 대한조선학회논문집
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• 제56권1호
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• pp.94-101
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• 2019

Underwater acoustic power should be measured in a free field, but it is not easy to implement. In practice, the measurement could be performed in a reverberant field such as a water-filled steel tank and concrete tank. In this case, the structure and the acoustic field are strongly or weakly coupled according to material properties of the steel and water. So, characteristics of the water tank must be investigated in order to get the accurate underwater acoustic power. In detail, modal frequencies, mode shapes of the structure and frequency response functions of the acoustic field could represent the characteristics of the reverberant water tank. In this paper, the structure-acoustic coupling has been investigated on a reverberant water tank numerically and experimentally. The finite element analysis has been carried out to estimate the structural and acoustical modal parameters under the dry and water-filled conditions, respectively. In order to investigate the structure-acoustic coupling effect, the numerical analysis has been performed according to the structure stiffness change of the water tank. The acoustic frequency response functions were compared with the numerical analysis and acoustic exciting test. From the results, the structural modal frequencies of the water-filled condition have been decreased compared to those of the dry condition in the low frequency range. The acoustic frequency response functions under the coupled boundary conditions showed different patterns from those under the ideal boundary conditions such as the pressure release and rigid boundary condition, respectively.

• Environmental Engineering Research
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• 제11권4호
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• pp.217-231
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• 2006

The gas-phase formation of polychlorinated naphthalenes (PCNs) and dibenzofurans (PCDFs) was experimentally investigated by slow combustion of the three chlorophenols (CPs): 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP), in a laminar flow reactor over the range of 550 to $750^{\circ}C$ under oxidative condition. Contrary to the a priori hypothesis, different distributions of PCN isomers were produced from each CP. To explain the distributions of polychlorinated dibenzofuran (PCDF) and PCN congeners, a pathway is proposed that builds on published mechanisms of PCDF formation from chlorinated phenols and naphthalene formation from dihydrofulvalene. This pathway involves phenoxy radical coupling at unsubstituted ortho-carbon sites followed by CO elimination to produce dichloro-9, 10-dihydrofulvalene intermediates. Naphthalene products are formed by loss of H and/or Cl atoms and rearrangement. The degree of chlorination of naphthalene and dibenzofuran products decreased as temperature increased, and, on average, the naphthalene congeners were less chlorinated than the dibenzofuran congeners. PCDF isomers were found to be weakly dependent to temperature, suggesting that phenoxy radical coupling is a low activation energy process. Different PCN isomers, on the other hand, are formed by alternative fusion routes from the same phenoxy radical coupling intermediate. PCN isomer distributions were found to be more temperature sensitive, with selectivity to particular isomers decreasing with increasing temperature.

• 한국전기전자재료학회논문지
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• 제31권1호
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• pp.44-49
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• 2018

This study analyzed the Vulnerability of Network Communication devices when IEMI is coupled with the Network System. An Ultra Wide Band Generator (180 kV, 700 MHz) was used as the IEMI source. The EUTs are the Switch Hub and Workstation, which are used to configure the network system. The network system was monitored through the LAN system configuration, to confirm a malfunction of the network device. The results of the experiment indicate that a malfunction of the network occurs as the electric field increases. The data loss rate increases proportionally with increasing radiating time. In the case of the Switch Hub, the threshold electric field value was 10 kV/m for all conditions used in this experiment. The threshold point causing malfunction was influenced only by the electric field value. The correlation between the threshold point and pulse repetition rate was not found. However, in case of the Workstation, it was found that as the pulse repetition rate increases, the equipment responds weakly and the threshold value decreases. To verify the electrical coupling of the EUT by IEMI, current sensors were used to measure the PCB line inside the EUT and network line coupling current. As a result of the measurement, it can be inferred that when the coupling current due to IEMI exceeds the threshold value, it flows through the internal equipment line, causing a malfunction and subsequent failure. The results of this study can be applied to basic data for equipment protection, and effect analysis of intentional electromagnetic interference.