• Management Science and Financial Engineering
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• 제14권2호
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• pp.89-104
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• 2008

Growth curves including Bass, Logistic and Gompertz functions are widely used in forecasting the market demand. Nonlinear least square method is often adopted for estimating the model parameters but it is difficult to set up the starting value for each parameter. If a wrong starting point is selected, the result may lead to erroneous forecasts. This paper proposes a method of selecting starting values for model parameters in estimating some growth curves by nonlinear least square method through grid search and transformation into linear regression model. Resealing the market data using the national economic index makes it possible to figure out the range of parameters and to utilize the grid search method. Application to some real data is also included, where the performance of our method is demonstrated.

• 산업경영시스템학회지
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• 제33권4호
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• pp.167-177
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• 2010

Recent competitive and technological changes during the past decade have accelerated the need for better capital recovery methods. Competition and technology have together shortened the expected lives of property which could not have been forecasted several years ago. Since the usage of technological growth models has been prevalent in various technological forecasting environments, the various forms of growth models have become numerous. Of six such models studied, some models do significantly better than others, especially at low penetration levels in predicting future levels of growth. A set of criteria for choosing an appropriate model for technological growth models was developed. Two major characteristics of an S-shaped curve were elected which differentiate the various models; they are the skewness of the curve and underlying assumptions regarding the variance of error structure of the model.

• 한국기술혁신학회:학술대회논문집
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• 한국기술혁신학회 2006년도 추계학술대회
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• pp.371-396
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• 2006

To see the implication of trade policy in endogeneous growth model, we introduce trade protection that takes the form of an import tariff and represents one plus the rate of protection provided to industry sector. We showed that considering goodness of fit of regression model, we can see that the empirical evidence is strongly in favor of the character of trade policies as the instrument spurring economic growth. As for import tariff, we see that 1% increase in the rate of tariff that protect domestic market causes the rate of growth to increase by 0.87%. An import tariff to final product significantly spurs product development and faster growth come as a result. But, we should note that the effects of trade policy are muted by the induced changes in the output of intermediates in an economy that is relatively unproductive in the research lab.

• 산업경영시스템학회지
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• 제32권4호
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• pp.184-191
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• 2009

In a technological driven environment, a depreciation estimate which is based on traditional life analysis results in a decelerated rate of capital recovery. This time pattern of technological growths models needs to be incorporated into life analysis framework especially in those industries experiencing fast technological changes. The approximation technique for calculating the variance can be applied to the six growth models that were selected by the degree of skewness and the transformation of the functions. For the Pearl growth model, the Gompertz growth model, and the Weibull growth model, the errors have zero mean and a constant variance over time. However, transformed models like the linearized Fisher-Pry model, the linearized Gompertz growth model, and the linearized Weibull growth model have increasing variance from zero to that point at which inflection occurs. It can be recommended that if the variance of error over time is increasing, then a transformation of observed data is appropriate.

• Asian-Australasian Journal of Animal Sciences
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• 제10권3호
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• pp.284-288
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• 1997

Purified diets containing five graded levels of tryptophan were fed to growing chicks to evaluate tryptophan requirements for growth and maintenance. A model was developed to separate tryptophan requirement for maintenance from requirement for growth. From this model, the daily tryptophan requirement for growth was 2.16 mg/g gain, and the daily requirement for maintenance 0.029 times metabolic body size ($Wg^{0.75}$). Based on nitrogen gain response, the tryptophan requirement for growth was 0.078 mg/mg N gain, and the daily maintenance requirement was 0.029 times metabolic body size. The total tryptophan requirements were 71.56 mg/day or 0.173% of the diet, 69.48 mg/day or 0.168% of the diet based on the weight gain response and nitrogen gain response, respectively. Previous tryptophan requirements for growing chicks aging 1-28 days are in close agreement with these estimates. Based on the relationship of weight gain and N gain, about 1.25% of the retained CP was consisted of tryptophan; the previously reported value of tryptophan content of chick muscle CP was 1.03%.

• Asian-Australasian Journal of Animal Sciences
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• 제10권3호
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• pp.277-283
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• 1997

Purified diets containing five levels of methionine with 0.4% cystine were fed to growing chicks (8 days old male Arbor Acre strain) to evaluate methionine requirements for growth and maintenance. A model was developed to separate methionine requirement for maintenance from requirement for growth. From this model the daily methionine requirement for growth was 4.22 mg/g gain, and the daily methionine requirement for maintenance was 0.034 times metabolic body size ($W^{0.75}$). Based on nitrogen gain response, the methionine requirement for growth was 0.162 mg/mg N gain, and the daily maintenance requirement was 0.037 times metabolic body size. The plateau of plasma methionine concentration reached at 117.16 mg intake pre day. The total methionine requirement determined based on weight gain response was 138.29 mg/day or 0.33% of the diet and the one determined based on nitrogen gain response was 141.7 mg/day of 0.34% of the diet, respectively. As a percentage of protein, methionine was calculated to be 2.6%; the reported methionine content of carcass CP was 1.76%.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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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.

• 한국결정성장학회지
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• 제13권2호
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• pp.51-55
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• 2003

The interrelation into nucleation and thermodynamic parameters of solutions has been established by plotting of various dependencies: the enthalpy of dissolution, solubility product and super-solubility on ionic salt radii and also the extent of deviation from an ideal Debye -Huckel model of electrolyte solution on solubility product. The possible methods of perfect crystal growth from aqueous solution have been found a priori by separating of known set of pair values of solubility and super-solubility into no less than six-nine characteristic and distinctive sub-sets.

• 한국결정성장학회지
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• 제1권1호
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• pp.74-81
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• 1991

Czochralski 단결정 성장계에서 유체동의 표면 복사열전달을 고려하여 온도분포를 모사하였다. 복사열전달 고려시 표면요소들의 view factor를 고려하였다. 고-액의 2상은 고상에 가상적으로 매우 큰 점성을 부여하여 연속의 단상으로 처리하였으며 응고시 잠열은 반복열량 방출법을 개발하여 처리하였다. 본 연구에서 개발한 응고 모델을 증명하기 위하여 Ca 금속의 용융에 적용하여 실험결과와 비교한 결과 잘 맞는다는 것을 알아낸 후 본 모사 프로그램을 Cz계에서 Al금속의 단결정 성장에 적용하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제10권1호
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• pp.122-133
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• 1997

Purified diets containing 5 graded levels of threonine were fed to young, growing and finishing pigs to determine the threonine requirement for growth and maintenance. A model was developed to subdivide the threonine requirement for the maintenance from the requirement for growth. From this model, the threonine requirement for growth was 7.733, 10.968 and 11.235 g/kg live weight gain and the maintenance requirement was 0.118, 0.048 and 0.024 g per unit of metabolic body size at each stage of growth, respectively. In the young pigs, the threonine requirement for growth was 0.388 g/g N gain and the maintenance requirement was 0.122 g per unit of metabolic body size. The breakpoint of plasma threonine concentrations was 3.995, 7.933 and 7.738 g/d, respectively. Expected requirements obtained from these formulae were in general agreement with previous estimates. Based on the weight gain vs N gain equation, about 4.24% of the retained protein was comprised of threonine and compared to 3.81%, the mean threonine content of pig muscle CP.