• Title/Summary/Keyword: C-flux

Search Result 1,783, Processing Time 0.027 seconds

MOGABA: Monitoring of Gamma-ray Bright AGN with KVN 21-m radio telescopes at 22 and 43GHz

  • Lee, Sang-Sung;Yang, Ji-Hae;Byun, Do-Young;Sohn, Bong-Won
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.36 no.2
    • /
    • pp.59.2-59.2
    • /
    • 2011
  • We introduce an ongoing project for monitoring total flux density at 22 and 43GHz, linearly polarized flux, and polarization angle at 22GHz of Gamma-ray bright AGN (Active Galactic Nuclei) with KVN (Korean VLBI Network) 21-m radio telescopes. The project started in May, 2011 with an effective monitoring cycle of 4 days, observing four main objects (3C 454.3, BL Lac, 3C 273, and 3C 279). More objects were included in the source list when they had flared in Gamma-ray. In this paper, we report the current status of the project and preliminary results for the monitoring observations.

  • PDF

Performance Test for Membrane Module Using Dean Vortices (Dean Vortices를 이용한 막모듈의 성능시험)

  • Chung, Kun Yong;Belfort, Georges
    • Membrane Journal
    • /
    • v.2 no.2
    • /
    • pp.104-111
    • /
    • 1992
  • A curved channel duct is designed, built and used specifically to produce Dean vortices as a result of flow around a $180^{\circ}C$ curve. We present evidence using optical reflection of the existmace of the vortices in the curved section and following flat section. Also, three different feed soludons(DI water, a monodispersed styrene-divinyl-benzene latex particle suspension and a yeast suspension) were used to determine the effectiveness of Dean instabilities to destabilize polarization layers. For each suspension, the flux data were compared as a function of time for flow conditions with and without Dean vortices, for a $0.2{\mu}m$ microfiltration membrane. Any permeation flux improvement was not sustained for $2.0De_c$ due to the vortex-decay in the flat section after the curved channel, but a 15~30% permeation improvement was obtained for $3.8De_c$.

  • PDF

Multifrequency monitoring of a flaring gamma-ray blazar 3C454.3 at 22 and 43GHz

  • Lee, Sang-Sung;Byun, Do-Young;Sohn, Bong-Won
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.36 no.1
    • /
    • pp.50.1-50.1
    • /
    • 2011
  • We report the results of the monitoring of a flaring gamma-ray blazar, 3C454.3 in total flux density at 22 and 43GHz and in polarization at 22GHz with KVN Ulsan 21-m radio telescope every 3-4 days from 19 November 2010 to 31 January 2011. After an extraordinary 5-day gamma-ray outburst in November 2010, the radio total flux density at 22/43GHz and the linear polarization at 22GHz has been decreased with a variation of a short time scale. In this paper, we also discuss a spectral change of 3C454.3 at 22 and 43GHz after the extraordinary gamma-ray outburst.

  • PDF

Investigation of the Jets of the Blazar 3C 279 with Korean VLBI Network (KVN) 22-129 GHz Observations

  • Yoo, Sungmin;Lee, Sang-Sung;Kim, Sang-Hyun;An, Hongjun
    • Journal of Astronomy and Space Sciences
    • /
    • v.38 no.4
    • /
    • pp.193-202
    • /
    • 2021
  • We present analysis results of Korean VLBI Network (KVN) four-band data for the highly variable blazar 3C 279. We measured the 22, 43, 86, and 129 GHz flux densities and spectral indices of the source using contemporaneous data taken over 5.6 years. We used the discrete correlation function to investigate correlations between the radio emission properties and those measured in the optical (2 × 1014 - 1.5 × 1015 Hz), X-ray (0.3-10 keV), and gamma-ray (0.1-300 GeV) bands. We found a significant correlation between the radio spectral index and gamma-ray flux without a time delay and interpreted the correlation using an extended jet scenario for blazar emission.

Ion Conductivity of Membrane in Proton Exchange Membrane Fuel Cell (고분자전해질 연료전지에서 고분자 막의 이온 전도도)

  • Hwang, Byungchan;Chung, Hoi-Bum;Lee, Moo-Seok;Lee, Dong-Hoon;Park, Kwonpil
    • Korean Chemical Engineering Research
    • /
    • v.54 no.5
    • /
    • pp.593-597
    • /
    • 2016
  • The effects of relative humidity, current density and temperature on the ionic conductivity were studied in PEMFC (Proton Exchange Membrane Fuel Cell). Water contents and water flux in the electrolyte membrane largely affected ion conductivity. The water flux was modelled and simulated by only electro-osmotic drag and back-diffusion of water. Ion conductivities were measured at membrane state out of cell and measured at MEA (Membrane and Electrode Assembly) state in condition of operation. The water contents in membrane increase as relative humidity increased in PEMFC, as a results of which ion conductivity increased. Current enhanced electro-osmotic drag and back diffusion and then water contents linearly increased. Enhancement of current density results in ion conductivity. Ion conductivity of about 40% increased as the temperature increased from $50^{\circ}C$ to $80^{\circ}C$.

A Study on the Heat Transfer Characteristics of Single Bead Deposition of Inconel 718 Superalloy on S45C Structural Steel Using a DMT Process (DMT 공정을 이용한 S45C 구조용강 위 Inconel 718 초합금 단일 비드 적층시 열전달 특성 분석에 관한 연구)

  • Lee, Kwang-Kyu;Ahn, Dong-Gyu;Kim, Woo-Sung;Lee, Ho-Jin
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.19 no.8
    • /
    • pp.56-63
    • /
    • 2020
  • The heat transfer phenomenon in the vicinity of the irradiated region of a focused laser beam of a DMT process greatly affects both the deposition characteristics of powders on a substrate and the properties of the deposited region. The goal of this paper is to investigate the heat transfer characteristics of a single bead deposition of Inconel 718 powders on S45C structural steel using a laser-aided direct metal tooling (DMT) process. The finite element analysis (FEA) model with a Gaussian volumetric heat flux is developed to simulate a three-dimensional transient heat transfer phenomenon. The cross-section of the bead for the FEA is estimated with an equivalent area method using experimental results. Through the comparison of the results of the experiments and those of the analysis, the effective beam radius of the bottom region of the volumetric heat flux and the efficiency of the heat flux model for different powers and travel speeds of the laser are predicted. From the results of the FEA, the influence of the power and the travel speed of the laser on the creation of a steady-state heat transfer region and the formation of the heat-affected zone (HAZ) in the substrate are investigated.

Synthesis of Nano Size $BaCeO_3$ as an Effective Flux Pining Center for YBCO Superconductor (YBCO 초전도체의 효과적인 플럭스 피닝 센터로서의 나노 크기 $BaCeO_3$ 합성)

  • Youn, J.S.;No, K.S.;Kim, Y.H.;Jun, B.H.;Lee, J.P.;Jung, S.Y.;Kim, C.J.
    • Progress in Superconductivity
    • /
    • v.10 no.1
    • /
    • pp.12-16
    • /
    • 2008
  • In this work, nano size $BaCeO_3$, which is a possible flux pinning medium of melt processed $YBa_{2}Cu_{3}O_x$ superconductor, was synthesized by the conventional solid state reaction method using powders. $BaCeO_3$ and $CeO_2$ were mixed thoroughly using a ball milling for 24 hours and calcined at $1200^{\circ}C$ for 5 hours for the formation $BaCeO_3$ powder. The obtained $BaCeO_3$ powder was attrition milled at various milling times of 60 min, 120 min and 240 min. The $BaCeO_3$ powders of various milling times were mixed with $YBa_{2}Cu_{3}O_x$ powder. Seed melt processed $YBa_{2}Cu_{3}O_x$-$BaCeO_3$ (15wt.%) superconductors were prepared and the superconducting properties were investigated. It was found that $T_c$ of $Y_{1.5}Ba_{2}Cu_{3}O_x$ samples was not significantly affected by $BaCeO_3$ addition, but $J_c$ of samples was increased by $BaCeO_3$ addition. The $J_c$ improvement by fine $BaCeO_3$ powder (120 min attrition-milled) was effective at low magnetic fields less than 2 T.

  • PDF

Evaporation Heat Transfer Characteristics of $CO_2$ in a Horizontal Tube

  • Lee Dong-Geon;Son Chang-Hyo;Oh Hoo-Kyu
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.29 no.3
    • /
    • pp.297-305
    • /
    • 2005
  • The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter. a pre-heater and evaporator (test section). The test section consists of a smooth. horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$. saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greatly effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality. heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In making a comparison between test results and existing correlations. the present experimental data are the best fit for the correlation of Jung et al. But it was failed to predict the evaporation heat transfer coefficient of $CO_2$ using by the existing correlation. Therefore. it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

Analysis of Sea Surface Temperature Simulation in the Northwestern Pacific and the East Asian Marginal Seas using HadGEM2-AO (HadGEM2-AO를 이용한 북서태평양-동아시아 해역의 표층 수온 모의 특성 분석)

  • Kim, Haejin;Kim, Cheol-Ho;Shin, Hong-Ryeol
    • Ocean and Polar Research
    • /
    • v.38 no.2
    • /
    • pp.89-102
    • /
    • 2016
  • In this study, we evaluated the model performance with respect to Sea Surface Temperature (SST) and Net Heat Flux (NHF) by considering the characteristics of seasonal temperature variation and contributing factors and by analyzing heat budget terms in the Northwestern Pacific and East Asian Marginal Seas ($110^{\circ}E-160^{\circ}E$, $15^{\circ}N-60^{\circ}N$) using the HadGEM2-AO historical run. Annual mean SST of the HadGEM2-AO is about $0.065^{\circ}C$ higher than observations (EN3_v2a) from 1950 to 2000. Since 1960, the model has simulated well the long-term variation of SST and the increasing rate of SST in the model ($0.014^{\circ}C/year$) is comparable with observations ($0.013^{\circ}C/year$). Heat loss from the ocean to the atmosphere was simulated slightly higher in the HadGEM2-AO than that in the reanalysis data on the East Asian Marginal Seas and the Kuroshio region. We investigated the causes of temperature variation by calculating the heat budget equation in the two representative regions. In the central part of the Kuroshio axis ($125^{\circ}E-130^{\circ}E$, $25^{\circ}N-30^{\circ}N$: Region A), both heat loss in the upper mixed layer by surface heat flux and vertical heat advection mainly cause the decrease of heat storage in autumn and winter. Release of latent heat flux through the heat convergence brought about by the Kuroshio contributes to the large surface net heat flux. Positive heat storage rate is mainly determined by horizontal heat advection from March to April and surface net heat flux from May to July. In the central part of the subtropical gyre ($155^{\circ}E-160^{\circ}E$, $22^{\circ}N-27^{\circ}N$: Region B), unlike Region A, vertical heat advection predominantly causes the decrease of heat storage in autumn and winter. In spring and summer, surface heat flux contributes to the increase of heat storage in Region B and the period is two times longer than the period for Region A. In this season, shoaling of the mixed layer depth plays an important role in the increase of SST.

Evaluation of High Flux Combined with Pretreatment Process for Application of Decentralized Water Supply System with Ceramic Membrane (세라믹 분리막의 분산형 용수공급 시스템 적용을 위한 전처리 연계공정의 고플럭스 평가)

  • Kang, Joon-Seok;Park, Seo Gyeong;Lee, Jeong Eun;Kang, So Yeon;Lee, Jeong Jun;Quyen, Vo Thi Kim;Kim, Seongsu;Kim, Han-Seung
    • Journal of Korean Society of Water Science and Technology
    • /
    • v.26 no.6
    • /
    • pp.61-72
    • /
    • 2018
  • In this study, applicability of the decentralized water supply system were investigated by the high flux evaluation using ceramic membrane with combined pretreatment process. A) filtration process increased the transmembrane pressure of 1.4 kPa and 89.5 kPa on 2 and $5m^3/m^2{\cdot}d$ of filtration flux, respectively, the physical backwashing recovery rate were less than 28.6%. The (B) Coag./Floc. - Sedi. combined process with 4 mg / L of A-PAC showed that the transmembrane pressure increased to within 6 kPa, the physical backwashing recovery rate was over 37.9 % higher than (A) Filtration process. (C) Coag./Floc. combined process showed an increase of transmembrane pressure compared with (B) Coag./Floc. - Sedi. combined process, physical backwashing recovery rate was over 84%. As a result of the membrane fouling analysis using the resistance in series model, the combined pretreatment process showed that the cake resistance (Rc) was more than 92% at membrane filtration flux of $2m^3/m^2{\cdot}d$. In the (C) Coag./Floc. combined process, cake resistance(Rc) was over 86% on high flux conditions. The coagulation floc contained in influent was removed by the membrane, and the cake layer formed with the removed floc was identified as reversible fouling resistance which could be recovered by physical backwashing. The decentralized water supply system, which has the limitation of site area and installation space, is considered to could be operation of high flux of ceramic membrane by applying (C) Coag./Floc. combined process without sedimentation process.