• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.92-100
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• 2016

A comparative method is applied to evaluate well-known formulas for estimating the size of supercavities of axisymmetric cavitators for the supercavitating underwater vehicle. Basic functional forms of these formulas are derived first for the cavity diameter from a momentum integral estimate and second for the cavity length from an asymptotic analysis of inviscid supercavity flows. The length and the diameter of axisymmetric supercavities estimated by each formula are compared, with available experimental data for a disk and a 45° conical cavitators, and also with computational results obtained by a CFD code, ‘fluent’, for conical cavitators of wide range of cone angles. Results for estimating the length and the diameter of the supercavities show in general a good agreement, which confirms the size of the supercavities for disk and conical cavitators can be estimated accurately by these simple formulas of an elementary function of cavitation number and drag coefficient of the cavitator. These formulas will be useful for from conceptual design of the cavitator to real-time control of the supercavitating underwater vehicle.

• Journal of Korean Association for Spatial Structures
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• v.19 no.2
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• pp.73-81
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• 2019

The high-temperature properties of mild steels were studied by comparing the test results of Kwon and the yield strength, tangent modulus predicted by the design provisions of ASCE and Eurocode(EC3). The column strengths for steel members at high temperatures were determined by the elastic and inelastic buckling strengths according to elevated temperatures. The material properties at high temperatures should be used in the strength evaluations of high temperature members. The buckling strengths obtained from the AISC, EC3 and approximate formula proposed by Takagi et al. were compared with ones calculated by the material nonlinear analysis using the EC3 material model. The newly simplified formulas for yield stress, tangent modulus, proportional limit and buckling strength which were proposed through a comparative study of the material properties and buckling strengths. The buckling strengths of proposed formulas were approximately equivalent to ones obtained from the formulas of Takagi et al. within 4%. They were corresponded to the lower bound values among the buckling strengths calculated by the design formulas and inelastic buckling analysis.

• Wind and Structures
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• v.29 no.3
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• pp.209-223
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• 2019

The assessment of wind-induced vibration for tall reinforced concrete (RC) buildings requires the accurate estimation of their dynamic properties, e.g., the fundamental vibration periods and damping ratios. In this study, RC frame-shear wall systems designed under gravity and wind loadings have been evaluated by utilising 3D FE modelling incorporating eigen-analysis to obtain the elastic periods of vibration. The conducted parameters consist of the number of storeys, the plan aspect ratio (AR) of buildings, the core dimensions, the space efficiency (SE), and the leasing depth (LD) between the internal central core and outer frames. This analysis provides a reliable basis for further investigating the effects of these parameters and establishing new formulas for predicting the fundamental vibration periods by using regression analyses on the obtained results. The proposed constrained numerically based formula for vibration periods of tall RC frame-shear wall office buildings in terms of the height of buildings reasonably agrees with some cited formulas for vibration period from design codes and standards. However, the same proposed formula has a high discrepancy with other cited formulas from the rest of design codes and standards. Also, the proposed formula agrees well with some cited experimentally based formulas.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.2
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• pp.13-20
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• 2019

This study was conducted in order to validate the nose shape factors of projectile in existing impact formulas for high-strength concrete in the event of collision with high-speed projectiles. In order to conduct the high-speed impact experiment, specified concrete strengths of 35, 100, and 120 MPa were prepared and tested in collision with both conical and hemispherical projectiles. The results showed that the measured penetration depth did not decrease linearly as concrete strength increased. Comparing the ratio penetration depth to the kinetic energy of the conical and hemispherical projectiles, the difference in the ratios for high strength concrete was observed to decline as concrete strength increased. However, in the modified NDRC and the Hughes formulas, the difference in the predicted penetration depth of the conical and hemispherical projectiles was constant despite increasing concrete strength. The modified NDRC and Hughes formulas should be improved upon so as to be applied to high strength concrete.

• Steel and Composite Structures
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• v.38 no.4
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• pp.415-430
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• 2021

The effective flange width was usually introduced into elementary beam theory to consider the shear lag effect in steel-concrete composite beams. Previous studies have primarily focused on the effective width under positive moments and elastic loading, whereas it is still not clear for negative moment cases in the normal service stages. To account for this problem, this paper proposed simplified formulas for the effective flange width and reinforcement stress of composite beams under negative moments in service stages. First, a 10-degree-of-freedom (DOF) fiber beam element considering the shear lag effect and interfacial slip effect was proposed, and a computational procedure was developed in the OpenSees software. The accuracy and applicability of the proposed model were verified through comparisons with experimental results. Second, a method was proposed for determining the effective width of composite beams under negative moments based on reinforcement stress. Employing the proposed model, the simplified formulas were proposed via numerical fitting for cases under uniform loading and centralized loading at the mid-span. Finally, based on the proposed formulas, a simplified calculation method for the reinforcement stress in service stages was established. Comparisons were made between the proposed formulas and design code. The results showed that the design code method greatly underestimated the contribution of concrete under negative moments, leading to notable overestimations in the reinforcement stress and crack width.

• Journal of Korean Medical classics
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• v.35 no.4
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• pp.115-125
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• 2022

Objectives : This study reviews whether the traditional medical thought process reflected in the Traditional Chinese Medical Treatment Plan for COVID-19 is based on existing classical texts, and examine concerns over the quality of evidence that the plan is based on. Methods : First, terminology and basic formulas composing the compound formulas in the COVID-19 TCM Treatment Plan were collected. Next, their usage in existing classical texts were searched in the medical classics database. Results : Infectious diseases similar to COVID-19 were understood as external disease due to Six Qi in the texts. Basic formulas used for treatment were those applied in Shanghan and Wenbing, among which cases where such formulas were applied in infectious diseases could be found in the classics. Conclusions : The level of evidence of the Treatment Plan suggested by various specialists could be evaluated as insufficient if we consider the literature. However, if application of such a plan could be supported institutionally, it could become a starting point for evidence generation.

• Journal of the Chungcheong Mathematical Society
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• v.23 no.4
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• pp.679-689
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• 2010

By developing and using certain operators like those initiated by Burchnall-Chaundy, the authors aim at investigating several decomposition formulas associated with the $Kamp{\acute{e}}$ de $F{\acute{e}}riet$ function $F_{2:0;0}^{0:3;3}$ [x, y]. For this purpose, many operator identities involving inverse pairs of symbolic operators are constructed. By employing their decomposition formulas, they also present a new group of integral representations of Eulerian type for the $Kamp{\acute{e}}$ de $F{\acute{e}}riet$ function $F_{2:0;0}^{0:3;3}$ [x, y], some of which include several hypergeometric functions such as $_2F_1$, $_3F_2$, an Appell function $F_3$, and the $Kamp{\acute{e}}$ de $F{\acute{e}}riet$ functions $F_{2:0;0}^{0:3;3}$ and $F_{1:0;1}^{0:2;3}$.

• Journal of the Korean Data and Information Science Society
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• v.25 no.1
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• pp.1-10
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• 2014

In this paper, we study approximations of the ruin probability in a continuous time surplus process. First, we introduce the well-known approximation formulas of the ruin probability such as Cram$\acute{e}$r, Tijms' and De Vylder's methods. We, then, suggest new approximation formulas of two types, which improve the existing approximation formulas. One is Cram$\acute{e}$r and Tijms' type which makes use of the moment generating function of distribution of a claim size and the other is De Vylder's type which makes use of the surplus process with exponential claims. Finally, we compare, by illustrating numerical examples, the newly suggested approximation formulas with the existing approximation formulas of the ruin probability.

• Journal of Physiology & Pathology in Korean Medicine
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• v.28 no.4
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• pp.411-416
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• 2014

Simple formulas (單方) of muscle section in Donguibogam (東醫寶鑑) have long been prescribed for strengthening muscle and/or prevention of age-related muscle loss. However, biological activity and mechanisms by which they influence myoblast differentiation have not been studied. Therefore, in this study, we evaluated the effects of 14 simple formulas on myoblast differentiation in C2C12 myoblast cells under non-cytotoxic ($0.5mg/m{\ell}$) conditions. C2C12 cells were treated with water extracts of simple formulas for 72 h, and RT-PCR was performed to determine the gene expression levels of myogenic regulatory factors (MRFs), including myoD, myogenin, MRF4, myf5, and insulin like growth factor-1 (IGF-1). Treatment with Colocasiae Rhizoma (CR), Pini Semen (PS), and Sesami Semen (SS) resulted in a significant increase in expression of myogenin in C2C12 cells. Treatment with Allii Macrostemi Bulbus (AM), Colocasiae Rhizoma (CR), and Pini Semen (PS) also resulted in increased expression of MRF4 in C2C12 cells. In addition, enhanced expression of IGF-1 was observed in treatment with Eucommiae cortex (EC), Dioscoreae Rhizoma (DR), Colocasiae Rhizoma (CR), Pini Semen (PS), and Sesami Semen (SS) in C2C12 cells. These results indicate that simple formulas of muscle section in Donguibogam could potentially enhance myoblast differentiation at least in part via increasing expression of myogenin, and/or MRF4 and/or IGF-1.

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.263-276
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• 2000

This paper is to derive the probable rainfall depths and the probable rainfall intensity formulas for Inchon Metropolitan district. The annual maximum rainfall data from 10 min. to 6 hours have been collected from the Inchon weather station. Eleven types of probability distribution are considered to estimate probable rainfall depths for 12 different storm durations at the Inchon Metropolitan district. Three tests including Chi-square, Kolmogorov-Smimov and Cramer Von Mises with the graphical analysis are adopted to select the best probability distribution. The probable rainfall intensity formulas are then determined by the least squares method using the trial and error approach. Five types of Talbot type, Sherman type, Japanese type, Unified type I, and Unified type II are considered to determine the best type for the Inchon rainfall intensity. The root mean squared errors are computed to compare the accuracy from the derived formulas. It has been suggested that the probable rainfall intensities having Unified type I for the short term duration should be the most reliable formulas by considering the root mean squared errors and the difference between computed probable rainfall depth and estimated probable rainfall depth.