• Journal of The Korean Astronomical Society
• /
• v.52 no.1
• /
• pp.1-9
• /
• 2019

We present the results of the spectral and temporal analysis of eight X-ray point sources in five nearby (distance < 20 Mpc) galaxies observed with Chandra. For spectral analysis, an absorbed powerlaw and an absorbed diskblackbody were used as empirical models. Six sources were found to be equally fitted by both the models while two sources were better fitted by the powerlaw model. Based on model parameters, we estimate the X-ray luminosity of these sources in the energy range 0.3 - 10.0 keV, to be of the order of ${\sim}10^{39}ergs\;s^{-1}$ except for one source (X-8) with $L_X>10^{40}ergs\;s^{-1}$. Five of these maybe classified as Ultraluminous X-ray sources (ULXs) with powerlaw photon index within the range, ${\Gamma}{\sim}1.63-2.63$ while the inner disk temperature, kT ~ 0.68 - 1.93 keV, when fitted with the disk blackbody model. The black hole masses harboured by the X-ray point sources were estimated using the disk blackbody model to be in the stellar mass range, however, the black hole mass of one source (X-6) lies within the range $68.37M_{\odot}{\leq}M_{BH}{\leq}176.32M_{\odot}$, which at the upper limit comes under the Intermediate mass black hole range. But if the emission is considered to be beamed by a factor ~ 5, the black hole mass reduces to ${\sim}75M_{\odot}$. The timing analysis of these sources does not show the presence of any short term variations in the kiloseconds timescales.

• Journal of Korean Association for Spatial Structures
• /
• v.20 no.4
• /
• pp.83-91
• /
• 2020

In this study, a tuned mass damper(TMD) was installed to control the displacement response to earthquakes by generalizing to six analysis models according to the shape of the upper structure based on the case of various large spatial structures around the world. The six analysis models are ribbed type, latticed type, elliptical type, gable type, barrel type, and stadium type composed of 3D arch trusses. In this paper, ribbed type, latticed type and elliptical type were analyzed. The mass of each TMD was set to 1% of the total structural mass. Result of analyzing the optimal number and position of the analysis model, the displacement response control was the most excellent in the model with 6 and 8 TMDs, and the displacement response decreased in most cases. The displacement response control was better with installing the TMD at the edge point than focusing the TMD at the center of the analysis model. However, when 10 or more TMDs are installed or concentrated in the center, large loads intensively act on the structure, resulting in increased displacement. Therefore, although it is slightly different depending on the shape, it is judged that the displacement response control is the best to install 6 and 8 TMDs at the close to the edge point.

• Journal of Korean Association for Spatial Structures
• /
• v.20 no.4
• /
• pp.73-81
• /
• 2020

In this study, a tuned mass damper(TMD) was installed to control the displacement response to earthquakes by generalizing to six analysis models according to the shape of the upper structure based on the case of various large spatial structures around the world. The six analysis models are ribbed type, latticed type, elliptical type, gable type, barrel type, and stadium type composed of 3D arch trusses. In this paper, ribbed type, latticed type and elliptical type were analyzed. The mass of each TMD was set to 1% of the total structural mass. Result of analyzing the optimal number and position of the analysis model, the displacement response control was the most excellent in the model with 6 and 8 TMDs, and the displacement response decreased in most cases. The displacement response control was better with installing the TMD at the edge point than focusing the TMD at the center of the analysis model. However, when 10 or more TMDs are installed or concentrated in the center, large loads intensively act on the structure, resulting in increased displacement. Therefore, although it is slightly different depending on the shape, it is judged that the displacement response control is the best to install 6 and 8 TMDs at the close to the edge point.

• Geomechanics and Engineering
• /
• v.30 no.6
• /
• pp.503-515
• /
• 2022

The permeability coefficient is an essential parameter for the study of seepage flow in fractured rock mass. This paper discusses the feasibility and application value of using readily available RQD (rock quality index) data to estimate mine water inflow and grouting quantity. Firstly, the influence of different fracture frequencies on permeability in a unit area was explored by combining numerical simulation and experiment, and the relationship between fracture frequencies and pressure and flow velocity at the monitoring point in fractured rock mass was obtained. Then, the stochastic function generation program was used to establish the flow analysis model in fractured rock mass to explore the relationship between flow velocity, pressure and analyze the universal law between fracture frequency and permeability. The concepts of fracture width and connectivity are introduced to modify the permeability calculation formula and grouting formula. Finally, based on the on-site grouting water control example, the rock mass quality index is used to estimate the mine water inflow and the grouting quantity. The results show that it is feasible to estimate the fracture frequency and then calculate the permeability coefficient by RQD. The relationship between fracture frequency and RQD is in accordance with exponential function, and the relationship between structure surface frequency and permeability is also in accordance with exponential function. The calculation results are in good agreement with the field monitoring results, which verifies the rationality of the calculation method. The relationship between the rock mass RQD index and the rock mass permeability established in this paper can be used to invert the mechanical parameters of the rock mass or to judge the permeability and safety of the rock mass by using the mechanical parameters of the rock mass, which is of great significance to the prediction of mine water inflow and the safety evaluation of water inrush disaster management.

• Korean Journal of Community Nutrition
• /
• v.19 no.5
• /
• pp.490-498
• /
• 2014

Objectives: This study was conducted to propose the need of re-establishing the criteria of the body weight classification in the elderly. We compared the Asia-Pacific Region Criteria (APR-C) with Entropy Model Criteria (ENT-C) using Morbidity rate of chronic diseases which correlates significantly with Body Mass Index (BMI). Methods: Subjects were 886 elderly female participating in the 2007-2009 Korea National Health and Nutrition Examination Survey (KNHANES). We compared APR-C with those of ENT-C using Receiver Operating Characteristics (ROC) curve and logistic regression analysis. Results: In the case of the morbidity of hypertension, the results were as follows: Where it was in the T-off point of APR-C, sensitivity was 67.5%, specificity was 43.1%, and Youden's index was 10.6. While in the cut-off point of ENT-C, it was 56.7%, 56.6%, and 13.3 respectively. In the case of the morbidity of diabetes, the results were as follows: In the cut-off point of APR-C, Youden's index was 14.2. While in the cut-off point of ENT-C, it was 17.2 respectively. The Area Under the ROC Curve (AUC) of the subjects who had more than 2 diseases among hypertension, diabetes, and dyslipidemia was 0.615 (95% CI: 0.578-0.652). Compared to the normal group, the odds ratio of the hypertension group which will belong to the overweight or obesity was 1.79 (95% CI: 1.30-2.47) in the APR-C, and 2.04 (95% CI: 1.49-2.80) in the ENT-C (p < 0.001). Conclusions: We conclude that the optimal cut-off point of BMI to distinguish between normal weight and overweight was $24kg/m^2$ (ENT-C) rather than $23kg/m^2$ (APR-C).

• Journal of Chest Surgery
• /
• v.14 no.1
• /
• pp.67-70
• /
• 1981

Aneurysms of the extracranial carotid artery are rare. This is a case report of the rapidly expanding false carotid aneurysm at left common carotid artery, which was repaired surgically with internal shunt This 20 year old male patient had a large pulsatile mass on left lateral aspect of neck at the time of admission. About 1 month before admission, he had received a trauma on left neck by glass piece and noted massive blood loss. And its skin of lesion was sutured simply at local clinic and well healed. 10 days before the admission, he had the sudden onset of the adult thumb sized and pulsatile mass and the mass had been enlarged more and more to the adult first-sized one. The cervical film showed a egg-sized and soft tissue mass. There was systolic bruit on the mass. The diagnosis was confirmed with the angiogram of left carotid artery and this showed the man`s thumb tip-sized extravasation at the point 2 Cm below the bifurcation of Internal and external carotid arteries. The emergency operation was performed by the internal shunt with carotid artery. The aneurysm was enclosed with the adventitia and carotid sheath, and the intima and media were Intact and had the opening of 0.5 cm in diameter. The opening was sutured by the one-hand mattress suture method and firmed with the Aron Alpha-A "Sankyo." The postoperative course was uneventful and the patient was discharged with good general condition.

• Journal of KSNVE
• /
• v.4 no.1
• /
• pp.83-88
• /
• 1994

In many circumstances, it is desired to move a mass from one position to another without inducing and vibration in the mass being moved. Two such problems are considered here : the motion of a mass initiated by another mass, nd the motion of a pendulum initiated by the specified motion of its support. In each case, it is dosired that the system start at rest and come to rest in the second position. A simple strategy for the specified motion is given here. The method is motivated by engine cam-follower design. The force required to move the system in question is determined as well as the maximum value of the force required(and the times at which these forces take place).

• Journal of Astronomy and Space Sciences
• /
• v.12 no.2
• /
• pp.179-195
• /
• 1995

RT Per has been known as a close binary of which the orbital period has unpredictably varied so far. Although there are no agreements with the working mechanism for the changes of the period, two interpretations have been suggested and waiting for to be tested: 1) light-time effects due to the unseen 3rd and 4rd bodies (Panchatsaram 1981), 2) Abrupt period-changes, due to internal variations of the system (e.g. mass transfer or mass loss) superimposing to the light-time effect by a 3rd body (Frieboes-Conde & Herczeg 1973). In the point of view that the former interprepation models could predict the behavior of the changes of the orbital period theoretically, we checked whether the recent observed times of minimum lights follow the perdictions by the first model or not. We confirmed that the observed times of minimum lights have followed the variations calculated by the light-times effects due to the 3rd and 4rd bodies suggested by Panchatsatam. In this paper a total of 626 times of minimum lights were reanalyzed in terms of the light-time effects by the 3rd and 4rd bodies. We concluded that the eclipsing pair in SVCam system moves in an elliptic orbit about center of mass of the triple system with a period of about $42.^y2$, while the mass center of the triplet is in light-time orbit about the center of mass of the quadruple system with a period of $120^y$. The mean masses deduced for the 3rd and 4rd bodies were $0.89m_\odot$ and $0.82m_\odot$, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.10a
• /
• pp.197-200
• /
• 1995

Corrugation of railway track can be caused by the various dynamic behavior of travelling wheels and track. In this paper, the coupled vibrations of travelling wheel and railway track are analyzed as the cause of corrugations. To analyze the coupled vibrations, the track supported by the sleepers and the traveling wheel are identified to the elastically supported infinite beam and the spring-mass system which runs at constant speed. The Hertzian contact spring is considered betwen the infinite beam and spring-mass system. The dynamic responses of elastically supported infinite beam and spring-mass system are calculated. The cause and development of rail corrugation are discussed in the view point of contact force fluctuation affected by the elastic supports and the corrugated surface profile of the track. By the obtained results, the possibilities of resonance are checked between the excitation by the corrugated surface profile and the natural frequency of contact spring-moving mass system. It may be thought to a development of railway corrugation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.2
• /
• pp.245-251
• /
• 1997

The dynamic behavior of elastic columns under the action of the subtangential force is studied in this paper. The subtangential force is the combination of the tip mass dead load and pure follower thrust. In this study, the tip mass is assumed to be a rigid body rather than a point mass. The equations of motion are derived based on the extended Hamilton's principle and the finite element method. Then the equations of motion are trasformed into a dimensionless form, and several parameters are identified. It is found that the critical subtangential force can be changed subtangentially by considering the parameters related to tip mass. It is also shown that the nonconservativeness of the applied force has a significant effect on the type of instability. The influence of the self-weight of the column on the variation of the critical force is also investigated.