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Mode-Matching Model for Electromagnetically Coupled Coaxial Dipole Array Antenna
EOM, Hyo Joon,KIM, Mi Jeong,OCK, Jang Soo The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.4
<P>A mode-matching model for an electromagnetically coupled coaxial dipole array antenna is presented. The Fourier transfor m/series technique is used to represent the continuous and discrete modes of scattered fields. The mode-matching is utilized to constitute a set of simultaneous equations for discrete modal coefficients. Numerical computation is performed to show its radiation behavior in terms of various antenna parameters.</P>
Integral Transforms in Electromagnetic Formulation
Hyo Joon Eom 한국전자파학회JEES 2014 Journal of Electromagnetic Engineering and Science Vol.14 No.3
In this research, integral transform technique for electromagnetic scattering formulation is reviewed. Electromagnetic boundary-value problems are presented to demonstrate how the integral transforms are utilized in electromagnetic propagation, antennas, and electromagnetic interference/compatibility. Various canonical structures of slotted conductors are used for illustration; moreover, Fourier transform, Hankel transform, Mellin transform, Kontorovich-Lebedev transform, and Weber transform are presented. Starting from each integral transform definition, the general procedures for solving Helmholtz’s equation or Laplace’s equation for the potentials in the unbounded region are reviewed. The boundary conditions of field continuity are incorporated into particular formulations. Salient features of each integral transform technique are discussed.
( Hyo Sun Kim ),( Chang Seok Bang ),( Yeon Soo Kim ),( Oh Kyung Kwon ),( Min Sun Park ),( Jeong Ho Eom ),( Gwang Ho Baik ),( Dong Joon Kim ) 대한장연구학회 2014 Intestinal Research Vol.12 No.3
Gastrocolocutaneous fistula is a rare complication of the percutaneous endoscopic gastrostomy (PEG) procedure. Typical symptoms usually occur in the first few months. We recently encountered 2 patients with 8- and 33-month asymptomatic periods. A 74-year-old man presented with watery diarrhea for 1 month. He had undergone PEG 9 months earlier. During workup, an upper endoscopy and abdominal CT scan revealed the migration of the feeding tube into the transverse colon. He was discharged with a nasogastric tube after treatment. A 77-year-old man presented with sudden loosening of his PEG tube with a duration over 3 days. He had undergone PEG procedure three times until that time. During workup, a gastrocolocutaneous fistula was diagnosed. However, when previous studies were reviewed, an abdominal CT scan, which was done 6 months ago before the third PEG, showed the fistula already existed at that time, suggesting that it was created about 33 months earlier when he underwent the second PEG procedure. The patient died of pneumonia aggravation despite conservative treatment. Both a high index of suspicion and the careful inspection of the upper endoscopy are very important for early diagnosis regardless of symptoms. (Intest Res 2014;12:251-255)
Radiation of Hertzian Dipole in Cylindrical Cavity with Narrow Slots
PAEK, Joon Ki,EOM, Hyo Joon The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.4
<P>Radiation of a Hertzian dipole placed within a cylindrical cavity with narrow slots is investigated. Narrow axial and transverse slots are considered. Scattered fields are expanded in terms of eigenfunctions and boundary conditions are enforced to obtain a set of simultaneous equations. Computations are performed to check the validity of the formulation.</P>
High-toughness natural polymer nonwoven preforms inspired by silkworm cocoon structure
Kwak, Hyo Won,Eom, Jungju,Cho, Se Youn,Lee, Min Eui,Jin, Hyoung-Joon Elsevier 2019 INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES Vol.127 No.-
<P><B>Abstract</B></P> <P>As the interest in environmentally friendly materials and concerns regarding depletion of petroleum resources has increased, the research on natural polymers is being actively pursued. Among the various materials based on natural polymeric resources, the interest in using natural fibers in bio-composites has grown due to their lightweight, non-toxicity, low cost, and abundance. However, the lack of interfacial adhesion between filaments and poor water resistance make the use of natural fiber-based polymer composites less attractive. To overcome these drawbacks, formaldehyde-based synthetic binders have been used. However, this requires an additional synthesis of the binder, and potential toxicity problems exist. In this work, robust and rigid natural polymer nonwoven preforms were prepared by mixing jute fibers with silk sericin (SS). SS was employed as a natural facile binder and the strong binding between jute fibers and SS resulted in remarkable enhancements in tensile strength, elongation, and toughness, which increased up to 539.1, 385.7, and 1943.8%, respectively, compared with the pristine jute nonwoven. In addition, the dense and rigid structure obtained through SS coating ensured the structural stability of the nonwoven preforms in moisture environments. Silkworm cocoon-structured natural polymer nonwoven preforms with excellent mechanical strength and higher physical stability may have more potential utilization in the composite material fields.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Silkworm cocoon-like natural fiber-based nonwoven preforms were fabricated. </LI> <LI> Sericin strongly bonded interface between each jute filament. </LI> <LI> Sericin dramatically improves the mechanical properties of jute nonwoven preforms. </LI> <LI> The water resistance of nonwoven preforms was obtained by sericin binder. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
미니 유화 중합을 통한 프탈로시아닌 안료의 캡슐화에 분산제가 미치는 영향
곽효원(Hyo Won Kwak),한재훈(Jae-Hun Han),홍연경(Yeonkyung Hong),엄정주(Jungju Eom),이진균(Jin-Kyun Lee),진형준(Hyoung-Joon Jin) 한국고분자학회 2019 폴리머 Vol.43 No.5
본 연구에서는 미니 유화 중합법을 통하여 프탈로시아닌 그린 안료를 캡슐화한 고분자 입자를 제조하였으며, 안료 및 분산제의 비율에 따른 입자 크기 및 색상 변화를 알아보았다. 프탈로시아닌 그린 안료를 안정하게 분산시키기위해 Triton X-100 분산제를 사용하였고, 안료분산액에서 분산제의 농도를 0, 0.2, 0.4, 0.8%(w/v)으로 조절하면서 입자의 특성을 평가하였다. Triton X-100의 농도와 안료의 분산성은 비례관계를 보였지만, 일정 수준이상의 분산제의 증가는 분산 안정성의 큰 변화가 없었다. 분산제가 첨가되지 않고 캡슐화를 진행할 경우 3-4 μm 이상 및 200-300 nm 크기의 구형 입자가 동시에 중합되었다. 한편, 분산제가 첨가됨으로써 안료의 분산성이 증가하고 이와 관련한 미니 유화 상태가 안정적으로 유지되어 200-300 nm 직경의 구형 입자가 균일하게 중합되었다. 분산제 농도의 영향은 입자 중합에 직결되었을 뿐만 아니라 안료 캡슐화의 효율에 큰 영향을 미쳤다. 중합한 입자의 모폴로지와 입경분포도에 대한 특성 평가를 위해 주사전자현미경(field emission scanning electron microscopy), 투과전자현미경(transmission electron microscopy) 및 동적 광산란법(dynamic light scattering) 분석을 실시하였고, 안료 캡슐화 효율을 푸리에 변환 적외선 분광법(Fourier-transform infrared spectroscopy), 열중량분석법(thermo-gravimetric analysis), 자외선 및 가시광선 분광법(ultraviolet-visible spectroscopy)을 이용하여 분석한 결과, 0.4%(w/v)의 Triton X-100을 첨가하였을 경우 가장 높은 캡슐화 효율을 보이는 것으로 확인하였다. In this study, phthalocyanine green pigment encapsulated polymer particles were prepared by mini-emulsion polymerization method and the particle size and color change according to the ratio of pigment and dispersant were examined. Triton X-100 dispersant was used to disperse the phthalocyanine green pigment, and the characteristics of the dispersibility and stability were evaluated while adjusting the concentration of the dispersant to 0, 0.2, 0.4, and 0.8% (w/ v) in the pigment dispersion. As the concentration of Triton X-100 increased, the dispersibility of the pigment was clearly improved. Without Triton X-100 dispersant, the spherical particles with diameters of 3-4 μm and 200-300 nm were polymerized at the same time due to the mini-emulsion instability. However, when dispersant was added, pigments were successfully dispersed and the mini-emulsion was well stabilized. As a result, phthalocyanine green encapsulated polymer particles which had the spherical shape with diameter of 200-300 nm were uniformly polymerized. The effect of the dispersant concentration was directly related to the mini emulsion stability and the pigment encapsulation efficiency. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize the morphology and particle size distribution of the polymerized particles, and Fouriertransform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA) and ultraviolet-visible spectroscopy (UVVis) were used to evaluate the characteristics of encapsulation efficiency. As a result, it was confirmed that the highest encapsulation efficiency was obtained when 0.4% (w/v) of Triton X-100 was used.
An Infinitely Long Monopole Antenna Driven by a Coaxial Cable: Revisited
LEE, Young Seung,EOM, Hyo Joon The Institute of Electronics, Information and Comm 2011 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.eb94 No.11
<P>An infinitely long monopole antenna driven by a coaxial cable is revisited. The associated Weber transform and the mode-matching method are used to obtain simple simultaneous equations for the modal coefficients. Computations are performed to illustrate the behavior of current distribution and antenna admittance in terms of antenna geometries.</P>