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조정기;이경호 순천향대학교 기초과학연구소 2010 순천향자연과학연구 논문집 Vol.16 No.2
In this article, we prove that Dual-Mesh Characteristic (DMC) ODE solver is exact for linear fluxes.
Design of an ultrawide-band TEM horn antenna with a microstrip-type balun
Chung, Kyungho,Pyun, S.,Choi, Jaehoon IEEE 2005 IEEE transactions on antennas and propagation Vol.53 No.10
An exponentially tapered ultrawide-band transverse electromagnetic (TEM) horn antenna having a microstrip-type balun is designed. The balun is used to improve the impedance characteristic of a TEM horn antenna. The measured bandwidth for VSWR less than 2.0 ranges from 67.94 to 1573.9 MHz. The bandwidth of the proposed TEM horn is three times wider than that of the linearly tapered TEM horn. The designed antenna can be used not only for electromagnetic compatibility measurement but also for broad-band communication system.
Reconfigurable microstrip-patch antenna with frequency and polarization-diversity functions
Chung, Kyungho,Nam, Yongsik,Yun, Taeyeoul,Choi, Jaehoon Wiley Subscription Services, Inc., A Wiley Company 2005 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.47 No.6
<P>The design of a novel reconfigurable microstrip-patch antenna with frequency- and polarization-diversity functions is presented. A U-slot inserted into the square patch and a PIN diode are utilized to realize frequency-diversity operation. Polarization diversity between linear polarization (LP) and right-hand circular polarization (RHCP) is also provided by switching the two PIN diodes on the truncating corners of a square patch on and off. The designed antenna is implemented and the antenna characteristics are measured. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 605–607, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21242</P>
Wideband microstrip-fed monopole antenna with a narrow slit
Chung, Kyungho,Park, Hoon,Choi, Jaehoon Wiley Subscription Services, Inc., A Wiley Company 2005 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS - Vol.47 No.4
<P>A novel compact and wideband microstrip-fed monopole antenna is proposed. The impedance bandwidth of the proposed antenna is increased by inserting a narrow slit near the lower right corner of the printed monopole. The designed antenna satisfies the 10-dB return-loss requirement over the frequency band of 3.1 to 11 GHz. The antenna also shows omnidirectional radiation patterns and good gain flatness. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 400–402, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21181</P>
Reconfigurable microstrip patch antenna with switchable polarization
Kyungho Chung,Yongsik Nam,Taeyeoul Yun,최재훈 한국전자통신연구원 2006 ETRI Journal Vol.28 No.3
A novel reconfigurable microstrip patch antenna with frequency and polarization diversities is proposed. A U-slot is incorporated into a square patch, and a PIN diode is utilized to switch the slot on and off, which realizes the frequency diversity characteristic. The polarization diversities among linear polarization (LP), right-hand circular polarization (RHCP), and left-hand circular polarization (LHCP) are also obtained by switching three PIN diodes on the slot and the truncating corners of a square patch on and off. The antenna design and experimental results are presented.
Elastomers and Composites : Study on the Functionalization of Waste EPDM and PP Blend
( Kyungho Chung ),( Jinhee Kim ) 한국고무학회 2015 엘라스토머 및 콤포지트 Vol.50 No.4
Recycling of ethylene-propylene-diene terpolymer (EPDM) scrap was tried by blending with polypropylene (PP). EPDM scrap powder was prepared by shear pulverization process at high temperature, which may lead to selective chain scission induced by difference in the critical elastic coefficient. On the other hand, EPDM scrap powder was prepared by adding a selected reclaiming agent during shear pulverization process at high temperature. Terpene as a bonding agent was then introduced to improve adhesion property. PP, used as a matrix for manufacturing thermoplastic elastomer, was modified by the incorporation of dicumyl peroxide and maleic anhydride. The functionalized EPDM and modified PP were blended and cured dynamically at 190℃. The blend materials prepared in this study showed the comparable results to those of conventional TPE in terms of tensile and flow properties. Also, the odor component of recycled EPDM was analyzed using GC-MS.
Chung, Kyungho,Choi, Jaehoon Wiley Subscription Services, Inc., A Wiley Company 2008 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.50 No.1
<P>A compact microstrip band-selective filter for ultra-wideband (3.1–10.6 GHz) radio system is proposed. The filter combines an optimum pseudo-bandpass filter and a coupled resonator bandstop filter on both sides of the meandered 50-Ω microstrip line. Three coupled resonators are modified to have S-shape to miniaturize the filter. The measured results show that the filter has wide passband of 146.7% (2.1–10.15 GHz) with low insertion loss and the stop-band of 7.42% (5.29–5.85 GHz) for 3-dB bandwidth. The measured group delay variation is less than 0.7 ns within the passband except the stop band. Finally, the filter is combined with band-notched antennas and then received power levels of the antennas with and without the filter are also examined at the notch frequency. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 98–101, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23019</P>
Study on the Characteristic of Elastomer Composite Containing Tungsten Powder
( Kyungho Chung ) 한국고무학회 2021 엘라스토머 및 콤포지트 Vol.56 No.1
In order to develop an ultra-high-density elastomeric material for substitution of steel dynamic dampers, a new curing system and technique for high-loading of the filler were examined in this study. Mechanochemical modification of chloroprene rubber (MAH-g-CR) using an internal mixer was carried out with maleic anhydride (MAH) as a reactive monomer. The optimum amount of MAH was 10 phr and the efficient grafting of MAH on CR could be achieved at a mixing temperature of 100℃. After preparing MAH-g-CR, 50 mol% epoxidized natural rubber (ENR 50) was blended with MAHg- CR to develop a “self-curable rubber blend system” via reaction between the functional groups of the elastomeric matrices without the curing agent and additives. The content of ENR 50 was fixed at 30 wt.% throughout evaluation of the curing behavior of the MAH-g-CR/ENR blend. Tungsten powder was added to the MAH-g-CR/ENR matrix up to 60 vol.% to obtain ultra-high-density, and the maximum density obtained was 7.57 g/㎤. Stable t<sub>s2</sub> (scorch time) and t<sub>90</sub> (90% cure time) could be obtained even when tungsten powder was incorporated up to 60 vol.%. In addition, the tensile strength and damping properties of MAH-g-CR/ENR containing 60 vol.% of tungsten were better than those of CR containing 60 vol.% of tungsten.
Long-Term Structural Integrity Evaluation for Wolsong Silo Storage Systems
Kyungho Roh,Sunghwan Chung,Taehyung Na 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
On-site storage facility using concrete silo dry storage systems for spent nuclear fuel at Wolsong NPP site came into operation in 1992 and was expanded four times, and a total of 300 silo dry storage systems are currently in operation. The design lifetime of silo dry storage systems has been licensed for 50 years. As the dry storage systems are subject to time constraints for a limited lifetime, countries operating the dry storage systems are working to ensure the long-term integrity of dry storage systems and IAEA also recommends that the dry storage systems be assessed for long-term storage. To demonstrate the long-term integrity due to material degradation during the licensed design lifetime, the structural integrity of silo dry storage systems was evaluated by considering the material degradation characteristics of concrete. The concrete compressive strength results measured so far by the rebound hammer method, which is an internationally standardized nondestructive test method for converting hardness into compressive strength using the correlation between rebound number and strength at the time of a Schmidt hammer strike, were analyzed in accordance with Wolsong NPP’s procedure to quantify the degradation characteristics, and the prediction of concrete strengths for 20 years and 50 years after construction of the silo dry storage systems was determined, respectively. Based on these residual compressive strengths, structural analyses of the silo dry storage systems were carried out under normal, off-normal and accident conditions of the related regulations, and the structural integrity of silo dry storage systems was reevaluated. It was confirmed the silo dry storage systems are able to maintain structural integrity up to the design lifetime of 50 years even if the concrete is deteriorated.