• Title/Summary/Keyword: Decay rate coefficient

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Distribution of BOD Decay Rate in Streams and Reservoirs (국내 수계에서의 BOD분해속도계수 분포)

  • Jang, Changwon;Kim, Donghwan;Lee, Jaeyong;Kim, Yeonju;Jung, Sungmin;Shin, Changmin;Kim, Bomchul
    • Journal of Korean Society on Water Environment
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    • v.28 no.2
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    • pp.178-184
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    • 2012
  • BOD decay rate is a key parameter of BOD-DO models in streams and lakes. In the calibration of water quality modeling appropriate range of coefficient is required for guidance of parameter selection. In this study BOD decay rate was measured at 48 stream sites and 10 reservoir sites in 8 different river systems. The decay rate ranged from 0.09 to 0.25 $day^{-1}$ with a mean of 0.16 $day^{-1}$. Among river systems the decay rates showed significantly different ranges, with the Han River system showing higher values than other river systems. In comparing different types of water bodies, the decay rate was slightly higher in tributaries than in reservoirs and mainstreams. Our results can provide guidance to the selection of proper coefficient for various water bodies in the calibration of water quality models.

Friction of a Brownian Particle in a Lennard-Jones Solvent: A Molecular Dynamics Simulation Study

  • Lee, Song-Hi
    • Bulletin of the Korean Chemical Society
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    • v.31 no.4
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    • pp.959-964
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    • 2010
  • In this work, equilibrium molecular dynamics (MD) simulations in a microcanonical ensemble are performed to evaluate the friction coefficient of a Brownian particle (BP) in a Lennard-Jones (LJ) solvent. The friction coefficients are determined from the time dependent friction coefficients and the momentum autocorrelation functions of the BP with its infinite mass at various ratios of LJ size parameters of the BP and solvent, ${\sigma}_B/{\sigma}_s$. The determination of the friction coefficients from the decay rates of the momentum autocorrelation functions and from the slopes of the time dependent friction coefficients is difficult due to the fast decay rates of the correlation functions in the momentum-conserved MD simulation and due to the scaling of the slope as 1/N (N: the number of the solvent particle), respectively. On the other hand, the friction coefficient can be determined correctly from the time dependent friction coefficient by measuring the extrapolation of its long time decay to t=0 and also from the decay rate of the momentum autocorrelation function, which is obtained by time integration of the time dependent friction coefficient. It is found that while the friction coefficient increases quadratically with the ratio of ${\sigma}_B/{\sigma}_s$ for all ${\sigma}_B$, for a given ${\sigma}_s$ the friction coefficient increases linearly with ${\sigma}_B$.

EXPONENTIAL DECAY FOR THE SOLUTION OF THE VISCOELASTIC KIRCHHOFF TYPE EQUATION WITH MEMORY CONDITION AT THE BOUNDARY

  • Kim, Daewook
    • East Asian mathematical journal
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    • v.34 no.1
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    • pp.69-84
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    • 2018
  • In this paper, we study the viscoelastic Kirchhoff type equation with a nonlinear source for each independent kernels h and g with respect to Volterra terms. 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.

A Study on Kinetics in One-Phase Anaerobic Digestion (단상 혐기성 소화공정에서의 동력학적 연구)

  • 조관형;조영태
    • Journal of Environmental Science International
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    • v.9 no.1
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    • pp.75-80
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    • 2000
  • Kinetic data for the acid phase anaerobic digestion were presented in this study and the constants were determined with acid production rate and gas production rate. Process models based on continuous culture theory were used to describe the characteristics of the acid forming microorganisms and to enable further development toward utilization of the process in a more rational manner. Acid phase digestion can be separated with appropriate manipulation of hydraulic retention time in anaerobic digestion. Kinetic analysis of data from the various hydraulic retention times using a phase specific model obtained form the acid phase indicated maximum specific growth rate of 0.40/h, saturation constant of 2,000mgCOD.$\ell$, yield coefficient of 0.35 mgVSS/msCOD utilized and decay constant of 0.04/h for the acid production rate. Similar analysis of data for the gas production rate indicated maximum specific growth rate of 0.003/h, saturation constant of 2,200mgCOD/$\ell$, yield coefficient of 0.035 mgVSS/mgCOD utilized and decay constant of 0.06/h.

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STABILIZATION FOR THE VISCOELASTIC KIRCHHOFF TYPE EQUATION WITH A NONLINEAR SOURCE

  • Kim, Daewook
    • East Asian mathematical journal
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    • v.32 no.1
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    • pp.117-128
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    • 2016
  • In this paper, we study the viscoelastic Kirchhoff type equation with a nonlinear source $$u^{{\prime}{\prime}}-M(x,t,{\parallel}{\bigtriangledown}u(t){\parallel}^2){\bigtriangleup}u+{\int}_0^th(t-{\tau})div[a(x){\bigtriangledown}u({\tau})]d{\tau}+{\mid}u{\mid}^{\gamma}u=0$$. 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.

On the Decay Rate of Soil Organic Matter and Changes of Soil Microbial populaiton (토양유기물의 분해속도와 Microbial populaiton의 소장에 관한 연구)

  • 김춘민
    • Journal of Plant Biology
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    • v.10 no.1_2
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    • pp.21-30
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    • 1967
  • The aim of present study is to elucidate the relationship between decay rate of soil organic matter, and the change of soil microbial population under the oak and pine forest soils in Kwang-nung plantation stand. The results obtained are as follows: 1) The correlation coefficient between decay rate and the soil bacteria is 0.84 and fungi 0.93. 2) The distribution of soil microbial population is higher in both F horizon of the oak forest soil, and F and H horizon of the pine forest soil. However, the number of soil microorganisms decreases with the depth in each forest soil. 3) The population of soil microbes is related to moisture content, total nitrogen, available phosphorus, and exchangeable calcium, except organic carbon in fungi. 4) The soil organic matter has been mainly decomposed by fungi, and the size of its population are governed by the factors such as moisture content, organic carbon, total nitrogen, available phosphorus, and exchangeable calcium.

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Estimation of CBOD Decay Rate for the Execution of Water Quality Model in the Nakdong-River Basin (낙동강에서 수질모델 실행을 위한 탈산소계수의 평가)

  • Yu, Jae-Jeong;Yoon, Young-Sam;Lee, Hae-Jin;Kim, Moon-Soo;Yang, Sang-yong;Lee, Young Joon
    • Journal of Korean Society on Water Environment
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    • v.21 no.5
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    • pp.511-515
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    • 2005
  • CBOD(carbonaceous BOD) decay rate was investigated for the execution of water quality model in Nakdong-Rive basin. Estimation of laboratory-derived CBOD decay rate, $k_l$ and CBOD decay rate in natural waters, $k_d$ were carried out. Hydraulic factors were applied for the calculation of $k_d$. Values of biochemical oxygen demand were investigated in Weagwan, Koreong, Jeokpo, Namgi and Mulgeom sites for the four times. The ranges of $k_l$ value were $0.04{\pm}0.01{\sim}0.14{\pm}0.03$. The values of $k_l$ in upstream sites were much larger than those in the downstream sites. The values of $k_d$ were 0.025, 0.036, 0.005 and 0.001 at Weagwan, Jeokpo, Namgi and Mulgeom, respectively, indicating that values of $k_d$ were generally larger than those of $k_l$.

Estimation of Kinetic Coefficient and Assimilated Nutrients Mass in SBR Process (연속회분식 반응 공정에서 동역학적 계수 및 미생물합성에 사용된 영양물질 산정)

  • Ji, Dae-Hyun;Shin, Sang-Woo;Lee, Kwang-Ho;Lee, Jae-Kune
    • Journal of Korean Society on Water Environment
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    • v.23 no.5
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    • pp.607-612
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    • 2007
  • In this study, we investigated the variations of the kinetic coefficients and Chemical Oxygen Demand (COD), N and P mass used for assimilation of a sequencing batch reactor (SBR) system with the variation of SRTs; SRTs of 7.5, 10.0, 12.5, 15.0 and 20.0 days were tested in one cycle of SBR operation to determine the optimum conditions for the operation of the SBR and estimate its COD, nitrogen and phosphorus removal efficiencies. The SBR system was operated under the conditions as follows: an operation time of 6 hours per cycle, a hydraulic retention time (HRT) of 12 hours, an influent COD loading of $0.4kg/m^3/day$, and an influent nitrogen loading of $0.068kgT-N/m^3/day$. The yield coefficient (Y) and decay rate coefficient ($k_d$) were estimated to be 0.4198 kgMLVSS/kgCOD and $0.0107day^{-1}$ by calculating the removal rate of substrate according to the variation of SRT. Considering total nitrogen amount removed by sludge waste process, eliminated by denitrification, and in clarified water effluent with reference to 150 mg/cycle of influent nitrogen amount, the percentage of nitrogen mass balance from the ratio of the nitrogen amount in effluent (N output) to that in influent (N input) for Runs 1~5 were 95.5, 97.0, 95.5, 99.5, and 95.5%, respectively, which is well accounted for, with mass balances close to 100%.

Analysis on the Impact of Space Environment on LEO Satellite Orbit (우주환경 변화에 따른 저궤도 위성의 궤도변화 분석)

  • Jung, Okchul;Yim, Hyeonjeong;Kim, Hwayeong;Ahn, Sangil
    • Journal of Aerospace System Engineering
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    • v.9 no.2
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    • pp.57-62
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    • 2015
  • The satellite orbit is continuously changing due to space environment. Especially for low earth orbit, atmospheric drag plays an important role in the orbit altitude decay. Recently, solar activities are expected to be high, and relevant events are occurring frequently. In this paper, analysis on the impact of geomagnetic storm on LEO satellite orbit is presented. For this, real flight data of KOMPSAT-2, KOMPSAT-3, and KOMPSAT-5 are analyzed by using the daily decay rate of mean altitude is calculated from the orbit determination. In addition, the relationship between the solar flux and geomagnetic index, which are the metrics for solar activities, is statistically analyzed with respect to the altitude decay. The accuracy of orbit prediction with both the fixed drag coefficient and estimated one is examined with the precise orbit data as a reference. The main results shows that the improved accuracy can be achieved in case of using estimated drag coefficient.

An Analytical Investigation on the Build-up of the Temperature Field due to a Point Heat Source in Shallow Coastal Water with Oscillatory Alongshore-flow

  • Jung, Kyung-Tae;Kim, Chong-Hak;Jang, Chan-Joo;Lee, Ho-Jin;Kang, Sok-Kuh;Yjm, Ki-Dai
    • Ocean and Polar Research
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    • v.25 no.1
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    • pp.63-74
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    • 2003
  • The build-up of the heat field in shallow coastal water due to a point source has been investigated using an analytical solution of a time-integral form derived by extending the solutions by Holley(1969) and also presented in Harleman (1971). The uniform water depth is assumed with non-isotropic turbulent dispersion. The alongshore-flow is assumed to be uni-directional, spatially uniform and oscillatory. Due to the presence of the oscillatory alongshore-flow, the heat build-up occurs in an oscillatory manner, and the excess temperature thereby fluctuates in that course and even in the quasi-steady state. A series of calculations reveal that proper choices of the decay coefficient as well as dispersion coefficients are critical to the reliable prediction of the excess temperature field. The dispersion coefficients determine the absolute values of the excess temperature and characterize the shoreline profile, particularly within the tidal excursion distance, while the decay coefficient determines the absolute value of the excess temperature and the convergence rate to that of the quasi-steady state. Within the e-folding time scale $1/k_d$ (where $k_d$ is the heat decay coefficient), heat build-up occurs more than 90% of the quasi-steady state values in a region within a tidal excursion distance (L), while occurs increasingly less the farther we go to the downstream direction (about 80% at 1.25L, and 70% at 1.5L). Calculations with onshore and offshore discharges indicate that thermal spreading in the direction of the shoreline is reduced as the shoreline constraint which controls the lateral mixing is reduced. The importance of collecting long-term records of in situ meteorological conditions and clarifying the definition of the heat loss coefficient is addressed. Interactive use of analytical and numerical modeling is recommended as a desirable way to obtain a reliable estimate of the far-field excess temperature along with extensive field measurements.