• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.83-97
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• 1995

The aim of this study is to derive a simple formula for predicting ultimate strength of hull girders under vertical bending moment. The existing formulas have been reviewed and classified into analytical approach, empirical approach and linear approximate approach. It is known that the ship hull will reach the ultimate limit state if both collapse of the compression flange and yielding of the tension flange occur. Side shells in the vicinity of the compression and tension flanges will often fail also, but the material around the final neutral axis will remain in the elastic state. Based on this observation, a credible distribution of longitudinal stresses around the hull section at the overall collapse state is assumed, and an explicit analytical formula is derived. The accuracy of the formula has been verified by a comparison of the experimental and the numerical results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.167-175
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• 2014

If volumetric flaws such as bearing pad fretting flaws and debris fretting flaws are detected in the pressure tubes of pressurized heavy water reactors during in-service inspection, the initiation of fatigue cracks and delayed hydrogen cracking from the detected volumetric flaws shall be assessed by using elastic stress concentration factors in accordance with CSA N285.8-05. The CSA N285.8-05 presents only an approximate formula based on linear elastic fracture mechanics for the debris fretting flaw. In this study, an engineering formula considering the geometric characteristics of the debris fretting flaw in detail was derived using two-dimensional finite element analysis and Kinectrics, Inc.'s engineering procedure with slight modifications. Comparing the application results obtained using the derived formula with the three-dimensional finite element analysis results, it is found that the results obtained using the derived formula agree well with the results of the finite element analysis.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.876-888
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• 2001

For a large scaled optimization based on response surface methods, an efficient quadratic approximation method is presented in the context of the trust region model management strategy. If the number of design variables is η, the proposed method requires only 2η+1 design points for one approximation, which are a center point and tow additional axial points within a systematically adjusted trust region. These design points are used to uniquely determine the main effect terms such as the linear and quadratic regression coefficients. A quasi-Newton formula then uses these linear and quadratic coefficients to progressively update the two-factor interaction effect terms as the sequential approximate optimization progresses. In order to show the numerical performance of the proposed method, a typical unconstrained optimization problem and two dynamic response optimization problems with multiple objective are solved. Finally, their optimization results compared with those of the central composite designs (CCD) or the over-determined D-optimality criterion show that the proposed method gives more efficient results than others.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.426-441
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• 2018

Recently, the generalized Hoek-Brown (GHB) failure criterion has been actively employed in various rock engineering calculations, but the analytical form of the corresponding Mohr failure envelope is not available, making it difficult to extend the application of the GHB criterion. In order to overcome this disadvantage, this study proposes a new method to express the tangential friction angle as an explicit function of normal stress by invoking the polynomial best-fitting to the relationship between normal stress and tangent friction angle implied in the GHB failure function. If this normal stress - tangential friction angle relationship is best-fitted with linear or quadratic polynomial function, it is possible to find the analytical root for tangential friction angle. Subsequently, incorporating the root into the relationship between shear stress and tangential friction angle accomplishes the derivation of the approximate Mohr envelope for the GHB criterion. It is demonstrated that the derived approximate Mohr failure envelopes are very accurate in the entire range of GSI value.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.187-191
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• 2003

The motion and time-mean drift force of a 2-D floating BBDB in waves are studied with and without taking account of fluctuating air pressure in the air chamber. It has been found numerically that the drift for a of the BBDB is in the reverse direction of propagation of the incident waves over specific frequency ranges as found by McCormick through his experiment work. The drift force is calculated by Pinkster's near-field method. Since Maruo's formula method for the drift force is always positive, Maruo's formula is only approximate and should be replaced by the correct near-field method.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.42-48
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• 1998

Numerical study is presented for the analysis of three-dimensional incompressible turbulent flows in multiblade centrifugal fan. Reynolds-averaged Navier-Stokes equations with standard k - $\epsilon$ turbulence model are transformed to non-orthogonal curvilinear coordinates, and are discretized with finite volume approximations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational area is divided into three blocks; core, impeller and scroll, which are linked by multi-block method. The flow inside of the fan is regarded as steady flow, and mathematical formula established from the cascade theory and empirical coefficient are employed to simulate tile flow through the impeller. From comparisons between the computational results and the experimental data, the validity of the mathematical formula for the blade forces was examined and good results were obtained qualitatively. Hence, we can get the flow characteristics of multi-blade centrifugal fan and it will be a corner stone of the development of the multiblade centrifugal fan.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.1
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• pp.122-131
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• 2011

The object of this study was to evaluate the single dose toxicity of Yukmijihwangtanggamibang (YMJHTGMB), a polyherbal formula have been traditionally used as prevention or treatment agent for various lung diseases including chronic obstructive pulmonary disease (COPD), in male and female mice. Aqueous extracts of YMJHTGMB (Yield = 16.33%) wasadministered to female and male ICR mice as an oral dose of 2,000, 1,000 and 500 mg/kg (body weight) according to the recommendation of Korea Food and Drug Administration (KFDA) Guidelines. Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation during 14 days after dosing, upon necropsy; organ weight and histopathology of 12 principle organs were examined. As results, we could not find any mortality, clinical signs, and changesin the body and organ weight except for soft feces restricted to YMJHTGMB 2,000 mg/kg treated two male mice (2/5; 40%) at 1 day after administration. In addition, no YMJHTGMB-treatment related abnormal gross findings and changes in histopathology of principle organs were detected except for some sporadic accidental findings. The results obtained in this study suggest that the 50% lethal dose and approximate lethal dose of YMJHTGMB aqueous extracts in both female and male mice were considered as over 2,000 mg/kg, the limited highest dosage recommended by KFDA Guidelines.

• Biomolecules & Therapeutics
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• v.15 no.4
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• pp.245-251
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• 2007

The object of this study was to evaluate the single dose toxicity of Kong-Jin-Dan (KJD), a polyherbal formula in male and female mice. KJD was administered to female and male ICR mice as an oral dose of 2000, 1000 and 500 mg/kg (body wt.) according to the recommendation of KFDA Guidelines. Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation during 14 days after dosing, upon necropsy, organ weight and histopathology of 12 principle organs were examined. As results, we could not find any mortality, clinical signs, and changes in the body and organ weight except for increases of lymphoid organ weights in KJD-dosing groups. These increases of lymphoid organ weights considered that related to the immune modulate effect of KJD not toxicological signs. In addition, no KJD-treatment related abnormal gross findings and changes in histopathology of principle organs were detected except for some sporadic accidental findings. The results obtained in this study suggest that the KJD does not cause any toxicological signs. The $LD_{50}$ and approximate LD of KJD extracts in both female and male mice were considered as over 2000 mg/kg.

• Journal of Physiology & Pathology in Korean Medicine
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• v.28 no.1
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• pp.53-58
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• 2014

The object of this study was to evaluate the single dose toxicity of Choweseuncheng-tang (CWS), a polyherbal formula have been traditionally used as prevention or treatment agent for various diseases as Tae-eumin prescription on Korean medicinal theory, Sasang-euihak, in male and female mice. Aqueous extracts of CWS (yield = 11.00%) was administered to female and male mice as an oral dose of 2,000, 1,000 and 500 mg/kg (body weight) according to the recommendation of Korea Food and Drug Administration (KFDA) Guidelines. Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation during 14 days after dosing, upon necropsy; organ weight and histopathology of 14 principle organs were also examined. As results, we could not find any CWS treatment related mortality and clinical signs, changes in the body and organ weights, gross findings and changes in histopathology of principle organs, except for some dose-independent accidental findings. The results obtained in this study suggest that the 50% lethal dose and approximate lethal dose of CWS aqueous extracts in both female and male mice were considered as over 2,000 mg/kg, the limited highest dosage recommended by KFDA Guidelines, and can be safety used in clinics.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.6
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• pp.1019-1026
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• 2010

The object of this study was to evaluate the single dose toxicity of Iijintanggami-bang (IJTGMB), a polyherbal formula have been traditionally used as prevention or treatment agent for various digestive disorders including reflux esophagitis, in male and female mice. Aqueous extracts of IJTGMB (Yield = 8.45%) was administered to female and male ICR mice as an oral dose of 2,000, 1,000 and 500 mg/kg (body weight) according to the recommendation of Korea Food and Drug Administration (KFDA) Guidelines. Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation during 14 days after dosing, upon necropsy; organ weight and histopathology of 12 principal organs were examined. As results, we could not find any mortality, clinical signs, and changesin the body and organ weight except for soft feces restricted to IJTGMB 2,000 mg/kg treated two male mice (2/5; 40%) at 1 day after administration. In addition, no IJTGMB-treatment related abnormal gross findings and changes in histopathology of principle organs were detected except for some sporadic accidental findings. The results obtained in this study suggest that the 50% lethal dose and approximate lethal dose of IJTGMB aqueous extracts in both female and male mice were considered as over 2,000 mg/kg, the limited highest dosage recommended by KFDA Guidelines.