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Analytic approaches for solving nonlinear fractional differential equations
Bongsoo Jang 한국산업응용수학회 2012 한국산업응용수학회 학술대회 논문집 Vol.7 No.1
In this paper, we propose a new analytical approach for solving fractional differential equations, which is called the enhanced multistage generalized differential transform method (EMs-GDTM). In the standard multistage generalized differential transform method (MsGDTM) it is a key to obtain a new initial condition in each sub-domain. The MsGDTM gives a new initial condition by using the approximate solution obtained in the previous sub-domain. We describe that this approach has difficulties to present the effect of memory arising in the fractional problems. To overcome this difficulty, we propose the EMsGDTM which presents well the effect of memory and gives more accurate solutions. Several illustrative examples are demonstrated and it is shown that the proposed technique is robust and efficient for solving fractional differential equations.
ALGEBRAIC CALCULATION FOR EFFECTIVE COEFFICIENTS IN PERIODIC MULTI-SCALE MEDIA
Bongsoo Jang,Hae-Soo Oh 한국산업응용수학회 2008 한국산업응용수학회 학술대회 논문집 Vol.4 No.3
In order to reduce the computational work in multi-scale media, the homogenization theory has been applied in many fields. The key step for the homogenization is to calculate effective coefficients. In this work, we demonstrate how to approximate an unknown effective coefficient from the known effective coefficients. In other words, suppose that [a<SUP>*</SUP><SUP>ij</SUP>] and [b<SUP>*</SUP><SUP>ij</SUP>] are the effective coefficients corresponding to the material properties [a<SUP>ij</SUP>], [b<SUP>ij</SUP>], respectively. Appropriate calculation for the effective coefficient associated with the material property [a<SUP>ij</SUP> + b<SUP>ij</SUP>] is presented by using the effective coefficients a<SUP>*</SUP><SUP>ij</SUP> and <SUP>*</SUP>b<SUP>ij</SUP>.
Laser generated elastic waves in a semi-infinite domain
Bongsoo Jang,Harish P. Cherukuri 한국산업응용수학회 2007 한국산업응용수학회 학술대회 논문집 Vol.3 No.2
Thermo-elastic waves generated by a pulsed laser in solid is of great interest due to the extensive applications of pulsed laser technologies in material processing and non-destructive detecting(NDT) and characterization. Since wavelength of ultrasonic waves is smaller than the usual size of defect, the method using ultrasonic waves generated by a laser can detect the presence of small defects. Lasers are capable of producing ultrasonic waves very accurately and have an advantage of producing high intensity power and directionality. Thus, the method of a pulsed laser is being commonly used to generate ultrasonic waves for NDT. In this study, one dimensional analytical and numerical investigation of laser generate elastic waves in a semi-infinite solid strap is presented. Assuming uncoupled thermo-elasticity theory, analytic solutions for the thermal and the mechanical equations are obtained by the Laplace transform techniques. Laser interaction with a solid specimen is studied when the optical absorption coefficient varies. A weaker displacement is observed for a large absorption coefficient. Numerical approximated solutions are compared with the analytical solutions.
OTDR을 이용한 실리콘 오일 기반의 광섬유 온도 센서
장재석(Jae Seok Jang),유욱재(Wook Jae Yoo),신상훈(Sang Hun Shin),이동은(Dong Eun Lee),김민건(Mingeon Kim),김혜진(Hye Jin Kim),송영범(Young Beom Song),장경원(Kyoung Won Jang),조승현(Seunghyun Cho),이봉수(Bongsoo Lee) 대한전기학회 2015 전기학회논문지 Vol.64 No.11
In this study, we developed a fiber-optic temperature sensor (FOTS) based on a silicone oil and an optical time domain reflectometer (OTDR) to apply the measurement of a coolant leakage in the nuclear power plant. The sensing probe of the FOTS consists of a silicone oil, a stainless steel cap, a FC terminator, and a single mode optical fiber. Fresnel reflection arising at the interface between the silicone oil and the single mode optical fiber in the sensing probe is changed by varying the refractive index of the silicone oil according to the temperature. Therefore, we measured the optical power of the light signals reflected from the sensing probe. The measurable temperature range of the FOTS using a Cu-coated silica fiber is from 70℃ to 340℃ and the maximum operation temperature of the FOTS is sufficient for usage at the secondary system in the nuclear power plant.
Bongsoo Lee,Kyoung Won Jang,Dong Hyun Cho,Wook Jae Yoo,Sang Hun Shin,Gye-Rae Tack,Soon-Cheol Chung,Sin Kim,Hyosung Cho,Byung Gi Park,Joo Hyun Moon,Siyong Kim IEEE 2008 IEEE transactions on nuclear science Vol.55 No.5
<P>In this study, a one-dimensional fiber-optic scintillating detector was developed for electron-beam therapy dosimetry. Each fiber-optic detector contains an organic scintillator as a sensitive volume and it is embedded and arrayed in a plastic phantom to measure one-dimensional high-energy electron-beam profiles of clinical linear accelerators. Plastic optical fibers guide the scintillating light which each detector probe generates to a photodiode array. The one-dimensional electron-beam profiles in the plastic phantom were measured in two different field sizes and for two electron-beam energies. Also, isodose and two-dimensional dose distributions in the plastic phantom were obtained using the one-dimensional scintillating detector array with two different electron beam energies.</P>
Measurements of Cerenkov Lights Using Optical Fibers
Bongsoo Lee,Kyoung Won Jang,Wook Jae Yoo,Sang Hun Shin,Jinsoo Moon,Ki-Tek Han,Dayeong Jeon IEEE 2013 IEEE transactions on nuclear science Vol.60 No.2
<P>Optical fibers can be a medium to produce Cerenkov light due to their dielectric components, and radiation-induced light signals can be obtained using optical fibers without any scintillating material. In this study, we measured and characterized gamma-ray induced Cerenkov light in silica optical fibers, a plastic optical fiber, and a plastic wavelength shifting fiber in order to select the adequate optical fiber for producing Cerenkov light. Also, we measured the intensity of Cerenkov light as functions of irradiated length, irradiation angle, and thickness of various scatterers using the chosen optical fiber.</P>
Jang, So Young,Song, Yun Mi,Kim, Han Sung,Cho, Yong Jae,Seo, Young Suk,Jung, Gyeong Bok,Lee, Chi-Woo,Park, Jeunghee,Jung, Minkyung,Kim, Jinhee,Kim, Bongsoo,Kim, Jin-Gyu,Kim, Youn-Joong American Chemical Society 2010 ACS NANO Vol.4 No.4
<P>Single-crystalline rock-salt PbS nanowires (NWs) were synthesized using three different routes; the solvothermal, chemical vapor transport, and gas-phase substitution reaction of pregrown CdS NWs. They were uniformly grown with the [100] or [110], [112] direction in a controlled manner. In the solvothermal growth, the oriented attachment of the octylamine (OA) ligands enables the NWs to be produced with a controlled morphology and growth direction. As the concentration of OA increases, the growth direction evolves from the [100] to the higher surface-energy [110] and [112] directions under the more thermodynamically controlled growth conditions. In the synthesis involving chemical vapor transport and the substitution reaction, the use of a lower growth temperature causes the higher surface-energy growth direction to change from [100] to [110]. The high-resolution X-ray diffraction pattern and X-ray photoelectron spectroscopy results revealed that a thinner oxide-layer was produced on the surface of the PbS NWs by the substitution reaction. We fabricated field effect transistors using single PbS NW, which showed intrinsic <I>p-</I>type semiconductor characteristics for all three routes. For the PbS NW with a thinner oxide layer, the carrier mobility was measured to be as high as 10 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-4/nn100163k/production/images/medium/nn-2010-00163k_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn100163k'>ACS Electronic Supporting Info</A></P>