• Journal of Astronomy and Space Sciences
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• 제39권4호
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• pp.159-167
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• 2022

Because of the small number of spacecraft available in the Earth's magnetosphere at any given time, it is not possible to obtain direct measurements of the fundamental quantities, such as the magnetic field and plasma density, with a spatial coverage necessary for studying, global magnetospheric phenomena. In such cases, empirical as well as physics-based models are proven to be extremely valuable. This requires not only having high fidelity and high accuracy models, but also knowing the weakness and strength of such models. In this study, we assess the accuracy of the widely used Tsyganenko magnetic field models, T96, T01, and T04, by comparing the calculated magnetic field with the ones measured in-situ by the GOES satellites during geomagnetically disturbed times. We first set the baseline accuracy of the models from a data-model comparison during the intervals of geomagnetically quiet times. During quiet times, we find that all three models exhibit a systematic error of about 10% in the magnetic field magnitude, while the error in the field vector direction is on average less than 1%. We then assess the model accuracy by a data-model comparison during twelve geomagnetic storm events. We find that the errors in both the magnitude and the direction are well maintained at the quiet-time level throughout the storm phase, except during the main phase of the storms in which the largest error can reach 15% on average, and exceed well over 70% in the worst case. Interestingly, the largest error occurs not at the Dst minimum but 2-3 hours before the minimum. Finally, the T96 model has consistently underperformed compared to the other models, likely due to the lack of computation for the effects of ring current. However, the T96 and T01 models are accurate enough for most of the time except for highly disturbed periods.

• 천문학회지
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• 제36권spc1호
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• pp.1-5
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• 2003

In an early paper Skumanich suggested the existence of a scaling law relating the mean sunspot magnetic field with the square-root of the photospheric pressure. This was derived from an analysis of a variety of theoretical spot models including those by Yun (1968). These were based on the Schliiter-Temesvary (S- T) similarity assumption. To answer criticisms that such modeling may have unphysical (non-axial maxima) solutions, the S-T model was revisited, Moon et al. (1998), with an improved vector potential function. We consider here the consequences of this work for the scaling relation. We show that by dimensionalizing the lateral force balance equation for the S- T model one finds that a single parameter enters as a characteristic value of the solution. This parameter yields Skumanich's scaling directly. Using an observed universal flux-radius relation for dark solar magnetic features (spots and pores) for comparison, we find good to fair agreement with Yun's characteristic value, however the Moon et al. values deviate significantly.

• Journal of Biosystems Engineering
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• 제17권3호
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• pp.247-259
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• 1992

This study intended to measure the desorption and adsorption EMC of four years old Peeled ginseng, Unpeeled ginseng and Taegeuk ginseng under various conditions$20^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$, $50^{\circ}C$) and five levels of relative humidity from 31% to 88%) by the static method. Four widely used EMC models were selected and evaluated. Also the empirical model was evaluated. The results are summarized as follows ; 1) EMC difference between ginseng size was not found but found between ginseng species. EMC difference between Peeled ginseng and Unpeeled ginseng was not found. EMC of Peeled ginseng and Unpeeled ginseng was higher than that of Taegeuk ginseng. 2) The hysteresis, which is difference between desorption and adsorption EMC, was found. Desorption EMC was higher than adsorption EMC. The hysteresis at the same temperature decreased as relative humidity increase. The difference of hysteresis between Peeled ginseng and Unpeeled ginseng was not large and the hysteresis of Taegeuk ginseng was smaller than those of other species. 3) Among the selected models, Henderson model was the best to predict the adsorption EMC of White ginseng(Peeled and Unpeeled ginseng), and Oswin model was the best to predict the desorption EMC of White ginseng and the desorption and adsorption EMC of Taegeuk ginseng. The models are as follows ; (a) White ginseng(Peeled and Unpeeled ginseng) ${\circ}$ Desorption EMC(Oswin model) : $$M=(0.1272-0.0007420T){\cdot}[RH/(1-RH)]^{(0.4164+0.001368T)}$$ ${\circ}$ Adsorption(Henderson model) : $$1-RH={\exp}[-0.0003480T_k\;{M_o}^{0.9231}]$$ (b) Taegeuk ginseng ${\circ}$ Desorption EMC(Oswin model) : $$M=(0.1051-0.0008439T)[RH/(1-RH)]^{(0.4553+0.003425T)}$$ ${\circ}$ Adsorption EMC(Oswin model) : $$M=(0.08247-0.0007559T){\cdot}[RH/(1-RH)]^{(0.5760+0.005540T)}$$ 4) The developed empirical models could predict the desorption and adsorption EMC for White and Taegeuk ginseng more precisely than selected models. The empirical models are as follows ; (a) White ginseng(Peeled and Unpeeled ginseng) ${\circ}$ Desorption EMC : $$M=0.124-0.000647T-0.216RH+0.373RH^2$$ ${\circ}$ Adsorption EMC : $$M=0.0879-0.000663T-0.197RH+0.399RH^2$$. (b) Taegeuk ginseng ${\circ}$ Desorption EMC : $$M=0.159-0.000728T-0.429RH+0.565RH^2$$ ${\circ}$ Adsorption EMC : $$M=0.123-0.000662T-0.384RH+0.555RH^2$$.

• Journal of the Korean Data and Information Science Society
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• 제21권6호
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• pp.1041-1049
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• 2010

한국프로야구에서 관중수는 프로야구 발전을 위한 가장 큰 수입원이며 프로야구팀의 관심사이므로 수요예측 모형이 있다면 프로야구구단들은 관중유치 전략을 세우는데 도움이 될 것이다. 이러한 이유로 본 연구에서는 한국프로야구 관중수를 예측하는 모형을 제안하고자 하며 제한된 여건 속에서 관중수에 영향을 미치는 이용 가능한 대부분의 변수들을 고려하였다. 종속변수는 로그관중수로 두고 다양한 독립변수와 오차항의 분산을 등분산, 조건부 이분산을 가정한 여러 가지 일반화 자기회귀 모형, 오차항의 분포가 t분포를 따른다는 가정을 이용한 일반화 자기회귀 조건부 이분산 모형들을 서로 비교하였는데, 그 결과 고려된 모형 중에서는 t분포를 가정한 일반화 자기회귀 조건부 이분산 모형이 가장 예측력이 뛰어났다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1327-1331
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• 2004

In this paper constant power models for electric trains have been used to analyze the steady states of the AT feeding systems. There are some previous studies utilizing constant impedance models or constant current models. These mentioned models are easy to use, but even so they don't yield exact results because of the innate restraints of the models since linear models cannot represent the characteristic of constant power in inverter-driven trains. It is reasonable that the train be considered as a constant load model when it drives or as a constant source model when it applies regenerative brake. Nonlinear equations which reflect constant power model for train have been developed by considering mutual impedances between wires and AT's turn-ratio of 1:1, then these equations have been solved by N-R iterative method. The proposed method doesn't need any specific assumptions through either the process of developing equations or the process of acquiring solutions, so it can be said to be stricter than other conventional methods.

• 대한기계학회논문집A
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• 제34권4호
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• pp.457-465
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• 2010

본 연구에서는 McVetty 와 Monkman-Grant 의 모델에 기초하여 만들어진 새로운 크리프 수명예측 모델인 Taylor 급수(T-S) 모델을 제안하였다. 본 모델은 회귀분석에서 발생하는 오차를 줄이기 위하여 McVetty 모델에서 sinh 함수를 Taylor 급수에 의해 변환한 후 첫 3 개항을 취한 것으로서 모델중의 상수 값은 통계학적 방법인 최대가능성 기법을 이용하여 결정되었다. T-S 모델을 이용하여 Alloy 617 의 크리프 수명을 예측한 결과 Eno, 지수함수 및 Larson-Miller(L-M) 방법에 비해 더 정확한 예측을 하는 것으로 나타났다. 또한 T-S 모델은 특정 온도에서 크리프 수명 예측을 할 수 있는 등온 T-S(IT-S) 모델로 표현될 수 있었으며, IT-S 모델은 Alloy 617 의 장시간 크리프 수명예측에서 가장 좋은 예측을 하는 것으로 나타났다.

• Natural Product Sciences
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• 제4권4호
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• pp.234-237
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• 1998

To evaluate the anti-diarrheal potential of the leaves of Bauhinia purpurea Linn., investigations were performed on different animal models e.g. castor oil induced diarrhea in rats and gastrointestinal motility test by using charcoal meal. In both the models the ethanolic extract of the leaves showed significant activity when compared to control group. The group treated with standard anti-diarrheal agent also showed significant activity comparing with control. Thus this study establishes the efficacy of Bauhinia purpurea Linn. Leaves as an anti-diarrheal as claimed in folklore.

• 한국경영과학회지
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• 제18권2호
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• pp.175-182
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• 1993

The probabilistic order level inventory model is developed when a supplier allows some credit period T for settling the accounts for purchase quantity. The credit period T is known constant. Mathematical models are derived for both the cases i) T'.leq. T and ii) T'>T. Expressions are derived for average expected total cost of the system, the optimum cycle time and for obtaining optimum order level S = S$_{0}$ in each case. The exmaples are given to illustrate the model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1846-1847
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• 2011

In this paper, for the trajectory tracking control of mobile robot, firstly, we obtained the T-S fuzzy models from the tracking-error models, one of which has nonlinear form and the other is linearized around the reference trajectory. Then the tracking control inputs are designed using the proposed fuzzy linearization method and the existed PDC method. Lastly, the tracking performance is tested and compared for each model through simulation.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권1호
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• pp.28-39
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• 2006

Two-phase flow through a T-junction has been studied by numerous researchers so far. The dividing characteristics of the gas and liquid phases at the T-junction are very complicated due to a lot of related variables. The prediction models have been suggested by using experimental data for a specific condition or working fluid. But, they showed the application limitation for the most of the other conditions or fluids. Since most of them are applicable for their own experimental range, the generalized model for the wide range of conditions and fluids is needed. Even though it's not available now, some of the models developed for air-water flow at a T-junction might be applicable for the part of refrigerants with some modifications. Especially, for the two-phase flow of refrigerants at the T-junction, very few studies have been performed. Further experimental study is required to be performed for the wide range of test conditions and fluids to predict properly the two-phase flow distribution and phase separation through the T-junction.