• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.107-112
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• 1990

In the vibration analysis of structure in fluid such as ships and offshore structures, the hydrodynamic added mass considerably affects the result of analysis. Therefore correct evaluation of the hydrodynamic added mass effect is required for an accurate analysis. But the correct evaluation of the effect is not simple because the added mass varies with the mode shape of vibration as well as the configuration of the structure. The universal method employed to evaluate added mass in ship hull vibration is Lewis's method via the introduction of 3 dimensional correction factor. But this conventional method is valid only for beam-like vibration.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.88.1-88.1
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• 2014

Helium mass in the envelope is one of the most important properties in progenitors of type Ib/c supernovae (SNe Ib/c), since SN Ib/c progenitors are distinguished by the presence of He I lines. However, previous progenitor models do not reproduce the required He mass limit($M_{He}$ < $0.14M_{\odot}$) suggested by a spectroscopic analysis of SN Ib/c. In this work, we investigated the effect of overshooting on the evolution of pure helium stars, focusing on the final He mass in the envelope, $M_{He,f}$. We used the MESA code to calculate single helium star models with the initial masses of $M_{init}=5{\sim}30M_{\odot}$, Z=0.02, 0.04 and overshooting parameters of $f_{ov}=0{\sim}0.4$. The final He mass $M_{He,f}$ decreases as $f_{ov}$ increases, due to larger burning core compared to weak overshooting models. Dependence of the final mass $M_{He,f}$ on overshooting is strongest for models with $M_{init}=7{\sim}10M_{\odot}$, and this effect originates from accelerated mass loss during transition between WNE and WC/O phase. However, $M_{He,f}$ exceeds $0.27M_{\odot}$ for all models, which still doesn't meet the criteria of $M_{He}$ < $0.14M_{\odot}$. This implies that mass loss during the post helium burning phase must be enhanced dramatically compared to what the standard models predict.

• Journal of Veterinary Clinics
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• v.17 no.1
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• pp.52-56
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• 2000

The objective of this study was to compare occurrence of the shipping fever associated with vaccination and mass medication in Korean Native Cow. Lack of vaccination (Pasteurella haemolytica, infectious bovine rhinotracheitis, bovine viral diarrhea, parainfluenza 3, and bovine respiratory syncytial virus) and mass medication before and after transportation, 67% of gram-negative cocci were detected. However, with vaccination and mass medication, only 33% of Gram-negative cocci were detected. When antimicrobial susceptibility for the detected bacterium was tested, apramycin, ampicillin, amilacin, clindamycin, gentamycin, kanamycin, penicillin, and streptomycin were resistant, whereas tylocin, amoxicillin, linocospetin, nalidixic acid, norfloxacin, oxalinic acid, and cefotaxime were susceptible. Morbidity and average therapeutic effect were 33% and 1.0time with vaccination and mass medication and were 78% and 5.3 times without vaccination and mass medication, respectively. Therefore, the results suggest that shipping fever would be considerably decreased with vaccination including mass medication before and after transportation.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.81.2-81.2
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• 2014

To figure out the effect of rotation on the final mass of Pop III stars, 1D stellar evolution simulations of the evolution of mass-accreting protostars are performed, with zero metalicity and high constant mass accretion rates. The protostar reaches the Keplerian rotation very soon after the onset of mass accretion, but it may continue mass accretion via angular momentum transport induced by viscous stress or magnetic field. However, as the accreting star evolves, the envelope expands rapidly when the total mass reaches $5{\sim}6M_{\odot}$ and the corresponding Eddington factor sharply increases. Strong radiative pressure with rotation imposes different criteria for breakup at the stellar surface, and the so-called 'critical rotation (${\Omega}{\Gamma}$-limit)' is reached. As a result mass accretion rate has to be significantly lowered. This implies that characteristic masses of Pop III stars would be significantly lowered than the previous expectation.

• Korean Journal of Applied Biomechanics
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• v.31 no.4
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• pp.308-313
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• 2021

Objective: The purpose of this study was to investigate the effect of different kettlebell mass (30%, 40%, and 50% of the body mass) on kinematics and kinetic variables of kettlebell swing. Method: Total of 16 healthy male who had at least 1 year of kettlebell training experience were participated in this study (age: 31.69 ± 3.46 yrd., height: 173.38 ± 4.84 cm, body mass: 74.53 ± 6.45 kg). In this study, a 13-segments whole-body model (upper trunk, lower trunk, pelvis, both side of forearm, upperarm, thigh, and shank) was used and 26 reflective markers were attached to the body to identify the segments during the movement. A 3-dimensional motion analysis with 8 infrared cameras and 4 channeled EMG was performed to find the effect of kettlebell mass on its swing. To verify the kettlebell mass effect, a one-way ANOVA with a repeated measure was used and the statistical significance level was set at 𝛼=.05. Results: Firstly, in all lower extremity joints and thoracic vertebrae, a statistically significant change in angle was shown according to an increase in kettlebell mass during kettlebell swing (p<.05). Secondly, in both the up-swing and down-swing phases, the knee joint and ankle joint ROM showed a statistically significant increase as the kettlebell mass increased (p<.05) but no statistically significant difference was found in the hip joint and thoracic spine (p>.05). Lastly, the hamstrings muscle activity was statistically significantly increased as the kettlebell mass increased during up-swing phases (p<.05). Also, as the kettlebell mass increased in P4 of the down swing phase, the gluteus maximus showed a statistically significantly increased muscle activation, whereas the rectus femoris showed a statistically significantly decreased muscle activation (p <.05). Conclusion: As a result of this study, hip extension decreased and knee extension increased at 40% and 50% of body mass, and the spine also failed to maintain neutrality and increased flexion. Also, when kettlebell swings are performed with 50% of body mass, synergistic muscle dominance appears over 30% and 40% of body mass, which is judged to have a risk of potential injury. Therefore, it is thought that for beginners who start kettlebell exercise, swing practice should be performed with 30% of body mass. In addition, even in the case of experienced seniors, as the weight increases, the potential injury risk may increase, so it is thought that caution should be exercised when performing swings with 40% and 50% of body mass. In conclusion, it is thought that increasing the weight after sufficiently training with 30% of the weight of all subjects performing kettlebell swing is a way to maximize the exercise effect as well as prevent injury.

• Structural Engineering and Mechanics
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• v.65 no.4
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• pp.389-400
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• 2018

An exact solution for the title problem was obtained in closed-form fashion considering general boundary conditions. The expressions of moment, shear and shear coefficient (or shear factor) of cross section under the effect of arbitrary temperature distribution were first derived. In view of these relationships, the differential equations of Timoshenko beam under the effect of temperature were obtained and solved. Second, the characteristic equations of Timoshenko beam carrying several spring-mass systems under the effect of temperature were derived based on the continuity and force equilibrium conditions at attaching points. Then, the correctness of proposed method was demonstrated by a Timoshenko laboratory beam and several finite element models. Finally, the influence law of different temperature distribution modes and parameters of spring-mass system on the modal characteristics of Timoshenko beam had been studied, respectively.

• Coupled systems mechanics
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• v.7 no.3
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• pp.321-331
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• 2018

When a cantilever beam with a lumped mass at its free end undergoes free transverse vibration, internal axial forces are produced in the beam. Such internal axial forces have an effect on free transverse vibration of the beam. This effect is studied in this paper. The equations of motion for the beam in terms of the generalized coordinates including the effect are derived. The method for determining free transverse vibration of the beam including the effect is presented. In numerical simulations, the results of free transverse vibration of the free end of the beam including and not including the effect are obtained. Based on comparison between the results obtained, the conclusions concerning the effect are given.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.264-270
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• 2008

Most of burning rate models used in hybrid combustion depend solely on oxidizer flux. But this empirical relation can not represent well the important effect of the thermo-chemical properties of solid fuel and thereby requires different value of empirical exponent and constant for each fuel considered. In this study, a new burning rate correlation was proposed using the mass transfer number(B number) which encompasses the thermochemistry effect of solid fuel and the aerodynamic effect caused by the combustion on the solid fuel surface where the effect of aerodynamic property in the mass transfer number was studied. The PMMA, PP, and PE were chosen as fuel, and gas oxygen as oxidizer. The new empirical burning rate expression depending on both the oxidizer flux and the mass transfer number was able to predict the burning rate of each fuel with just a single exponent value and constant, and it was found that the aerodynamic effect on the blowing effect did show a minor effect on the burning rate correlation.

• Geomechanics and Engineering
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• v.37 no.3
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• pp.213-222
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• 2024

Determination of jointed rock mass properties plays a significant role in the design and construction of underground structures such as tunneling and mining. Rock mass classification systems such as Rock Mass Rating (RMR), Rock Mass Index (RMi), Rock Mass Quality (Q), and deformation modulus (Em) are determined from the jointed rock masses. However, parameters of jointed rock masses can be affected by the tunnel depth below the surface due to the effect of the in situ stresses. In addition, the geomechanical properties of rocks change due to the effect of metamorphism. Therefore, the main objective of this study is to apply correlation analysis to investigate the relationships between rock mass properties and some parameters related to the depth of the tunnel studied. For this purpose, the field work consisted of determining rock mass parameters in a tunnel alignment (~7.1 km) at varying depths from 21 m to 431 m below ground surface. At the same excavation depths, thirty-seven rock types were also sampled and tested in the laboratory. Correlations were made between vertical stress and depth, horizontal/vertical stress ratio (k) and depth, k and Em, k and RMi, k and point load index (PLI), k and Brazilian tensile strength (BTS), Em and uniaxial compressive strength (UCS), UCS and PLI, UCS and BTS. Relationships were significant (significance level=0.000) at the confidence interval of 95% (r = 0.77-0.88) between the data pairs for the rocks taken from depths greater than 166 m where the ratio of horizontal to vertical stress is between 0.6 and 1.2. The in-situ stress parameters affected rock mass properties as well as metamorphism which affected the geomechanical properties of rock materials by affecting the behavior of minerals and textures within rocks. This study revealed that in-situ stress parameters and metamorphism should be reviewed when tunnel studies are carried out.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.24-31
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• 2011

Rectangular box type structures are used in many fields of civil, mechanical and marine engineering. Especially, Most ship structures are often in contact with inner or outer fluid, like ballast, fuel and stem tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine and propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tanks. Many authors have studied vibration of rectangular tanks containing fluid. Few research on dynamic interaction among tank walls filled with fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass of water have to be considered. In the previous report, a numerical analysis is performed for the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region, and mode characteristics in accordance with changing breadth of the plates by using finite element method for plates and boundary element method for fluid region. In this paper, the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region, and mode characteristics in accordance with changing length, thickness, and boundary condition of the plates are investigated numerically and discussed.