• 생명과학회지
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• 제15권1호
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• pp.15-20
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• 2005

동충하초 Paecilomyces tenuipes C240의 균사체 배양과정에서 균사체 성장, 세포외 다당체 생산, 기질감소 속도를 표현할 수 있는 동력학적 모델을 제시하였다. 균사체 성장은 Logistic식을, 세포외 다당체 생산은 Luedeking-Piret 식을, 기질소모는 Luedeking-Piret 유사식을 각각 적용함으로써, 전체 균사체 배양과정을 예측할 수 있었다. 모델식에서 사용된 주요 kineti, constant들은 다음과 같다: 균사체의 최대 비성장속도${\mu}m,\;0.7281\;h^{-1};$; 다당체 생산에서의 growth-associated constant $(\alpha),\;0.1743g(g\;cells)^{-1}$; non-growth-associated constant $(\beta),\;0.0019g(g\;cells)^{-1}\;;$ maintenance coefficient ($(m_s),\;0.0572g\;(g\;cells)^{-1}$·5L 발효조에서 얻은 균사체 성장, 세포외 다당체 생산, 기질감소 속도자료들을 모델에서 예측한 결과와 비교한 결과 서로 잘 일치하는 것으로 보아, 본 연구에서 제안된 모델식은 이 동충하초 균사체 배양공정의 scale-up등의 프로세스 설계에 응용가능 할 것이며, 다른 종류의 동충하초 균사체 배양공정에도 적용가능 할 것으로 판단된다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제3권2호
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• pp.99-106
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• 1999

In this paper, the spline hazard rate model to the randomly censored data is introduced. The unknown hazard rate function is expressed as a linear combination of B-splines which is constrained to be linear(or constant) in tails. We determine the coefficients of the linear combination by maximizing the likelihood function. The number of knots are determined by Bayesian Information Criterion. Examples using simulated data are used to illustrate the performance of this method under presenting the random censoring.

• 한국안전학회지
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• 제23권4호
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• pp.30-35
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• 2008

The present study has been conducted to examine the effect of grid resolution on the predicted results for electric cable fire using pyrolysis model in FDS(Fire Dynamics Simulator, version 5). The grid independent test for different grid resolutions has been performed for a PE coating cable and the grid resolution is defined by the non-dimensional characteristic length of fire and mean grid size. The calculated maximum heat release rate and mean flame spread rate were almost constant for higher grid resolution of 20${\sim}$25 and the computing time for the grid resolution takes approximately 20hours to solve flame propagation with pyrolysis model. The geometrical simplification of a electric cable dose not greatly affect on the maximum heat release rate and flame spread rate and the rectangular approximation of cable shape gives acceptable result comparing with the round cable with stepwise grid.

• 전기학회논문지
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• 제58권12호
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• pp.2505-2510
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• 2009

Semiconductor processes need measurement to confirm where there are problems in quality after progresses manufacturing process. This paper suggests equipment and automatic measure sampling method that control monitoring ratio according to change point occurrence availability of process that is not measure method by the existent simple ratio rate. This paper defines measure section as ailment section, metastable section and stability section by change point standard and create statistical model of each section and developed suitable measure rate model by section. As a result, we have accomplished maximum throughput and minimum sampling number that needs to maintain constant level of quality. Proposed method minimizes load of measure process by brings production quality sophistication and decrease of process badness and lowers measure rate in stable section making perception about problem occurrence quick heightening measure rate at change point occurrence.

• Advances in materials Research
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• 제11권1호
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• pp.41-57
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• 2022

This paper is focused on delamination analysis of a multilayered inhomogeneous viscoelastic beam subjected to linear creep under constant applied stress. The viscoelastic model that is used to treat the creep consists of consecutively connected units. Each unit consists of one spring and two dashpots. The number of units in the model is arbitrary. The modulus of elasticity of the spring in each unit changes with time. Besides, the modulii of elasticity and the coefficients of viscosity change continuously along the thickness, width and length in each layer since the material is continuously inhomogeneous in each layer of the beam. A time-dependent solution to the strain energy release rate for the delamination is derived. A time-dependent solution to the J-integral is derived too. A parametric analysis of the strain energy release rate is carried-out by applying the solution derived. The influence of various factors such as creep, material inhomogeneity, the change of the modulii of elasticity with time and the number of units in the viscoelastic model on the strain energy release rate are clarified.

• Journal of Biosystems Engineering
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• 제19권2호
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• pp.112-123
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• 1994

At present, no appropriate drying conditions can be found for the heated-air drying of mushroom in Korea. Usually, mushroom is being dried at the temperature range of 40 to $50^{\circ}C$ until the moisture content reaches 10~13% (wb). However, drying characteristics of the mushroom should be investigated for quality improvement and efficient drying operation of the mushroom. The results of this study may be summarized as follows ; 1. The effect of air temperature on the rate of drying was greater than that of relative humidity for drying of mushroom, and the rate of drying was increased with increase in the air temperature. 2. Drying rate for Shiitake mushroom showed falling-rate period of drying without constant-rate period of drying. Drying rate for Oyster mushroom showed a short constant-rate period at the initial stage of drying process, and followed by falling-rate period of drying. 3. Exponential and App.-Diffusion models were found to describe well the drying process of Shiitake mushroom. Exponential and Thompson models for Oyster mushroom in which Thompson model was the most suitable for Oyster mushroom. 4. The equilibrium moisture content of the mushroom decreased with decrease in the air temperature and increase in the relative humidity. In room condition($20^{\circ}C$, 54% RH), the calculated values of the equilibrium moisture content showed 11.17% for Shiitake mushroom and 13.19% for Oyster mushroom, respectively.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1920-1926
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• 2010

Yoon et $al.^1$ presented an approximate mathmatical model to describe ammonia removal from an experimental batch reactor system with gaseous headspace. The development of the model was initially based on assuming instantaneous equilibrium between ammonia in the aqueous and gas phases. In the model, a "saturation factor, $\beta$" was defined as a constant and used to check whether the equilibrium assumption was appropriate. The authors used the trends established by the estimated $\beta$ values to conclude that the equilibrium assumption was not valid. The authors presented valuable experimental results obtained using a carefully designed system and the model used to analyze the results accounted for the following effects: speciation of ammonia between $NH_3$ and $NH^+_4$ as a function of pH; temperature dependence of the reactions constants; and air flow rate. In this article, an alternative model based on the exact solution of the governing mass-balance differential equations was developed and used to describe ammonia removal without relying on the use of the saturation factor. The modified model was also extended to mathematically describe the pH dependence of the ammonia removal rate, in addition to accounting for the speciation of ammonia, temperature dependence of reactions constants, and air flow rate. The modified model was used to extend the analysis of the original experimental data presented by Yoon et $al.^1$ and the results matched the theory in an excellent manner.

• 대한화학회지
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• 제52권3호
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• pp.217-222
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• 2008

본 논문에서는 반응 매질의 부피가 촉매 반응 속도에 미치는 영향을 조사하였다. 단순하지만 정확한 모델에 대한 연구로부터 촉매 반응의 반응 속도 계수는 매질의 부피가 줄어들 수록 증가함을 알게 되었다. 평균 반응속도 상수(average reaction rate constant)는 Collins-Kimball 속도 상수의 일반화 된 형태로 얻어졌는데, 속도 상수는 부피의 효과를 보정해주는 인자를 포함하고 있다. 조사한 모델의 반응물 농도는 전통적 화학 반응론에서 예측되는 지수함수적 감소와는 상당한 차이를 보이는데 이는 기존 화학 반응속도론에서는 무시되는 반응분자 공간 분포의 비평형 확산운동(non-equilibrium diffusive dynamics)의 효과 때문이다. 반응 매질의 부피 가 유한한 점을 고려하면, 반응 시간이 충분히 오래 지났을 때, 기존의 확산지배 반응에서는 예측 되는 않는 지수 함수적 농도 감소가 얻어지는데, 그 속도 상수 역시 반응매질 크기에 의존한다.

• Communications for Statistical Applications and Methods
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• 제25권1호
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• pp.91-97
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• 2018

In this paper, we show that there exists an optimal investment policy for the surplus in a risk model, in which the surplus is continuously invested to other business at a constant rate a > 0, whenever the level of the surplus exceeds a given threshold V > 0. We assign, to the risk model, two costs, the penalty per unit time while the level of the surplus being under V > 0 and the opportunity cost per unit time by keeping a unit amount of the surplus. After calculating the long-run average cost per unit time, we show that there exists an optimal investment rate $a^*$>0 which minimizes the long-run average cost per unit time, when the claim amount follows an exponential distribution.

• 약학회지
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• 제28권3호
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• pp.169-177
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• 1984

Release characteristics of salicylic acid from ethylcellulose(EC) films containing varying ratio of dieththylphthalate (DEP) were studied. Mathematical analysis of the release data showed that the release behavior actually conforms with the Higuchi's diffusion-controlled model. The release rate constants(k) were independent from the film thickness and the pH of release medium, but were proportional to the concentration of salicylic acid itself. The logarithm of the release rate constant (log k) increased as the concentration of DEP was increased. In conclusion, hydrophobic plastisizer DEP seemed to be very useful in controlling release rate constant of slightly soluble drugs as like salicylic acid without changing it's release characteristics.