• Title, Summary, Keyword: Decay Function

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Estimation of joint and index dissipation in HTS tape (고온초전도 선재의 접합 및 인덱스손실 평가)

  • 김정호;임준형;장석헌;김규태;주진호;최세용;나완수;강형구;고태국
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • pp.59-62
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    • 2003
  • We fabricated two HTS closed coils by using resistive-joint method and the joint resistance of the coil was estimated by field decay technique at 77 K. In addition, we used the Runge-kutta method for the numerical analysis to estimate the decay properties. The joint resistances were evaluated as a function of critical current of HTS closed coil and external field strength of excitation coil. It was observed that joint resistance was independent of critical current and external field strength. It was estimated that joint resistance was 8.0$\times$10$^{-9}$ $\Omega$ to 11.9$\times$10$^{-9}$ $\Omega$ for coils of contact length for 7 cm.

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SPATIAL BEHAVIOR OF SOLUTION FOR THE STOKES FLOW EQUATION

  • Liu, Yan;Liao, Wenhui;Lin, Changhao
    • Bulletin of the Korean Mathematical Society
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    • v.48 no.2
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    • pp.397-412
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    • 2011
  • In this paper, the equation of the transient Stokes flow of an incompressible viscous fluid is studied. Growth and decay estimates are established associating some appropriate cross sectional line and area integral measures. The method of the proof is based on a first-order differential inequality leading to an alternative of Phragm$\'{e}$n-Lindell$\"{o} $f type in terms of an area measure of the amplitude in question. In the case of decay, we also indicate how to bound the total energy.

NECESSARY CONDITION AND SUFFICIENT CONDITION FOR THE WAVELET FRAMES IN $L^2(R^n)$

  • Wu, Guochang;Zhang, Rui
    • Journal of applied mathematics & informatics
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    • v.28 no.5_6
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    • pp.1117-1130
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    • 2010
  • The main goal for this paper is consider the necessary conditions and sufficient conditions of wavelet frames in higher dimensions with an arbitrary expanding matrix dilation. At first, we give a necessary condition of wavelet frame in $L^2(R^n)$, which generalizes the univariate results of Shi from one dimension with an arbitrary real number a(a > 1) dilation to higher dimension with an arbitrary expansive matrix dilation. Secondly, we deduce a necessary condition for wavelet frames in $L^2(R^n)$ when the function $\psi$ satisfies some property of the decay. For the case n = 1, we obtain a corollary which has weaker condition comparing with existing result.

Combining Four Elements of Precipitation Loss in a Watershed (유역내 네가지 강수손실 성분들의 합성)

  • Yoo, Ju-Hwan
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.200-204
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    • 2012
  • In engineering hydrology, an estimation of precipitation loss is one of the most important issues for successful modeling to forecast flooding or evaluate water resources for both surface and subsurface flows in a watershed. An accurate estimation of precipitation loss is required for successful implementation of rainfall-runoff models. Precipitation loss or hydrological abstraction may be defined as the portion of the precipitation that does not contribute to the direct runoff. It may consist of several loss elements or abstractions of precipitation such as infiltration, depression storage, evaporation or evapotranspiration, and interception. A composite loss rate model that combines four loss rates over time is derived as a lumped form of a continuous time function for a storm event. The composite loss rate model developed is an exponential model similar to Horton's infiltration model, but its parameters have different meanings. In this model, the initial loss rate is related to antecedent precipitation amounts prior to a storm event, and the decay factor of the loss rate is a composite decay of four losses.

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The Characteristics of Hydraulic Valve for a Passive Reactor (피동형 원자로의 Hydraulic Valve 특성 실험)

  • Kim, Sang-Nyung;Kim, Yoong-Seock
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.8
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    • pp.1083-1090
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    • 1998
  • A kind of three-way check valve, so called hydraulic calve was proposed for the substitute of the density lock of passive reactor such as SPWR (System-Integrated Pressurized Water Reactor). The function of the valve are the separation of the borated water from main coolant loop for normal operation and the insurge of the water into the loop for shutdown and the removal of the decay power when the main coolant flow rate is not enough. To verify the operability and the characteristics of the valve, experimental works were executed with 1/3 scale model calve. Also a diffuser model was proposed for the theoretical analysis of the valve.

Carbonyl Emissions during Food Decay from Kimchi, Fish, and Salted Fish

  • Kabir, Ehsanul;Kim, Ki-Hyun
    • Asian Journal of Atmospheric Environment
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    • v.2 no.2
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    • pp.109-115
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    • 2008
  • In this study, the emissions of carbonyl compounds as offensive odorants were measured using three food types (Kimchi, fresh fish, and salted fish) as a function of time. Odor samples for each food type, collected at 0, 1, 3, 7, and 14 days, were analyzed by high performance liquid chromatography (HPLC). Only three kinds of carbonyl compounds were quantified above their respective detection limits: formaldehyde, acetaldehyde, and acetone. The emission patterns of these compounds were distinguishable from each other. Formaldehyde tends to peak at the beginning and decrease through time with unique patterns. Conversely, acetaldehyde and acetone seem to increase gradually through time. The results showed that relative patterns of carbonyl emissions were more distinguishable by compound type rather than food type.

New Bubble Size Distribution Model for Cryogenic High-speed Cavitating Flow

  • Ito, Yutaka;Tomitaka, Kazuhiro;Nagasaki, Takao
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.700-710
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    • 2008
  • A Bubble size distribution model has been developed for the numerical simulation of cryogenic high-speed cavitating flow of the turbo-pumps in the liquid fuel rocket engine. The new model is based on the previous one proposed by the authors, in which the bubble number density was solved as a function of bubble size at each grid point of the calculation domain by means of Eulerian framework with respect to the bubble size coordinate. In the previous model, the growth/decay of bubbles due to pressure difference between bubble and liquid was solved exactly based on Rayleigh-Plesset equation. However, the unsteady heat transfer between liquid and bubble, which controls the evaporation/condensation rate, was approximated by a theoretical solution of unsteady heat conduction under a constant temperature difference. In the present study, the unsteady temperature field in the liquid around a bubble is also solved exactly in order to establish an accurate and efficient numerical simulation code for cavitating flows. The growth/decay of a single bubble and growth of bubbles with nucleation were successfully simulated by the proposed model.

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Accumulated organic matter, litterfall production, and decomposition tell us the status of litter dynamics in forests

  • Kim, Jae-Geun
    • Journal of Ecology and Environment
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    • v.35 no.2
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    • pp.99-109
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    • 2012
  • Litterfall dynamics in forests are assessed by estimating biomass production and decomposition. However, there have been few studies on how litter dynamics impact the health and management of ecosystems. Here, a new approach to measure and assess ecosystem function is presented based on conventional methods using littertraps, litterbags, and the mass on the forest floor. To assess the status of litter dynamics, the decay rate (k) was estimated from a litterbag experiment, and removal rates ($k_i$) were determined from mass balance on the forest floor at 21 sites on three mountains in South Korea. The $k_3$ (organic mass ratio of $O_i$ and $O_e+O_a$ + A horizons in November) values in an equilibrium state in South Korea were within the range of $k{\pm}0.174$ when considering the annual variation of litterfall production. This study also suggests that sampling sites for these types of studies should be in the middle, not at the ends, of steady slopes on the forest floor.

EXPONENTIAL STABILITY FOR THE GENERALIZED KIRCHHOFF TYPE EQUATION IN THE PRESENCE OF PAST AND FINITE HISTORY

  • Kim, Daewook
    • East Asian mathematical journal
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    • v.32 no.5
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    • pp.659-675
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    • 2016
  • In this paper, we study the generalized Kirchhoff type equation in the presence of past and finite history $$\large u_{tt}-M(x,t,{\tau},\;{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^t}\;h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\\hspace{25}-{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_{-{\infty}}}^t}\;k(t-{\tau}){\Delta}u(x,t)d{\tau}+{\mid}u{\mid}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the expoential decay rate of the Kirchhoff type energy.

ASYMPTIOTIC BEHAVIOR FOR THE VISCOELASTIC KIRCHHOFF TYPE EQUATION WITH AN INTERNAL TIME-VARYING DELAY TERM

  • Kim, Daewook
    • East Asian mathematical journal
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    • v.32 no.3
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    • pp.399-412
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    • 2016
  • In this paper, we study the viscoelastic Kirchhoff type equation with the following nonlinear source and time-varying delay $$u_{tt}-M(x,t,{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\int_{0}^{t}}h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\+{\parallel}u{\parallel}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the uniform decay rate of the Kirchhoff type energy.