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Monostatic RCS Reduction by Gap-Fill with Epoxy/MWCNT in Groove Pattern
Won-Ho Choi,Hong-Kyu Jang,Jae-Hwan Shin,Tae-Hoon Song,Jin-Kyu Kim,Chun-Gon Kim 한국전자파학회JEES 2012 Journal of Electromagnetic Engineering and Science Vol.12 No.1
In this study, we investigated the effect of groove pattern and gap-fill with lossy materials at 15 GHz frequency of Ku-band. We used Epoxy/MWCNT composite materials as gap-fill materials. Although epoxy does not have an absorbance capability, epoxy added conductive fillers, which are multi-walled carbon nanotubes (MWCNT), can function as radar absorbing material. Specimens were fabricated with different MWCNT mass fractions (0, 0.5, 1.0, 2.0 wt%) and their permittivity in the Ku-band was measured using the waveguide technique. We investigated the effect of gap-fill on monostatic RCS by calculating RCS with and without gap-fill. For arbitrarily chosen thickness and experimentally obtained relative permittivity, we chose the relative permittivity of MWCNT at 2 wt% (εr =8.8?j2.4), which was the lowest reflection coefficient for given thickness of 3.3 ㎜ at V-pol. and 80° incident angle. We also checked the monostatic RCS and the field intensity inside the groove channel. In the case of H-pol, gap-fill was not affected by the monostatic RCS and magnitude was similar with or without gap-fill. However, in the case of V-pol, gap-fill effectively reduced the monostatic RCS. The field intensity inside the groove channel reveals that different RCS behaviors depend on the wave polarizations.
Algorithm for Reducing the Effect of Network Delay of Sensor Data in Network-Based AC Motor Drives
Chun, Tae-Won,Ahn, Jung-Ryol,Lee, Hong-Hee,Kim, Heung-Geun,Nho, Eui-Cheol The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3
Network-based controls for ac motor drive systems are becoming increasingly important. In this paper, an ac motor control system is implemented by a motor control module and three sensor modules such as a voltage sensor module, a current sensor module, and an encoder module. There will inevitably be network time delays from the sensor modules to the motor control system, which often degrades and even destabilizes the motor drive system. As a result, it becomes very difficult to estimate the network delayed ac sensor data. An algorithm to reduce the effects of network time delays on sensor data is proposed, using both a synchronization signal and a simple method for estimating the sensor data. The algorithm is applied to a vector controlled induction motor drive system, and the performance of the proposed algorithm is verified with experiments.
ON MATHEMATICAL TO NONLINEAR(曲線) KINETICS WITH INTRAMASS DIFFUSION UNIMOLECULAR REACTION
Won, You-Sung,Yoon, Ryong-Soo,Jeong, Il-Hyun,Kang, Shin-Choon,Ham, Young-Min,Kang, Doo-Whan,Lee, Chul-Tae,Ma, Young-Dai,Choi, Nak-Mann,Moon, Sei-Ki,Kim, Hyung-Jin,Park, Kyung-Ai,Lee, Chang-Ou,Chun, Bu 단국대학교 대학원 1989 學術論叢 Vol.13 No.-
Equations to mass transfer with nonlinear kinetics from Langmuir-Hinshelwood model or so were thought in this article. We used the perturbation method with simplified Taylor expansion method to attain the solution semianalytically. We even carried out the comparison in effectiveness factor by both. For numerical solution, we introduced Gauss-Siedel method, for the method had been rarely used. Unimolecular recation having Langmuir-Hinshelwood model wass a sample. We perceived the perturbation method to be useful for the q<10 or q>5 in the mode d^2Θ/dN^2 = Ø^2Θ/1+qΘ We, on the other hand, attained the solution without difficulty from the simplified method.