• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.143-144
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• 1996

Two-component models (normal star and degenerate star components) are the simplest realization of clusters with a mass spectrum because the high mass stars quickly evolve off leaving degenerate stars behind, while low mass stars survive for a long time as main-sequence stars. In the present study we examine the post-collapse evolution of globular clusters using two-component Fokker-Planck models that include three-body binary heating. We confirm that a simple parameter ${\epsilon}{\equiv} (E_{tot}/t_{rh})/(E_c/t_{rc})$ well describes the occurrence of gravothermal oscillations of two-component clusters. Also, we find that the degree of instability depends on the steepness of the mass function such that clusters with a steeper mass function are less exposed to instability.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.95-98
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• 2007

A general purpose program NUFLEX has been extended for two-phase flows with topologically complex interface and cavitation flows with liquid-vapor phase change caused by large pressure drop. In analysis of two-phase flow, the phase interfaces are tracked by employing a LS(Level Set) method. Compared with the VOF(Volume-of-Fluid} method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. Also, the cavitation process is computed by including the effects of evaporation and condensation for bubble formation and collapse as well as turbulence in flows. The volume-faction and continuity equations are adapted for cavitation models with phase change. The LS and cavitation formulation are implemented into a general purpose program for 3-D flows and verified through several test problems.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.457-466
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• 1996

The Voltage stability problem has recently been dealt with in the literature from various points of view. The diverse theories have been established in voltage stability analysis because of the complicates of power systems and diverse phenomena of voltage collapse. Through rigorous mathematical operations, this paper shows that all the major methods used in static voltage stability, i.e - Jacobian method, voltage sensitivity method, real and reactive power loss sensitivity method and energy function method - have an identical background in theory. The results from the test in sample systems have shown the validity of this verification. (author). refs., figs., tabs.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.569-575
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• 2018

The stability of shallow cavities with an arbitrary profile is a difficult issue in geotechnical engineering. This paper investigates this problem on the basis of the upper bound theorem of limit analysis and the Hoek-Brown failure criterion. The influence of pore pressure is taken into consideration by regarding it as an external force acting on rock skeleton. An objective function is constructed by equating the internal energy dissipation to the external force work. Then the Lagrange variation approach is used to solve this function. The validity of the proposed method is demonstrated by comparing the analytical solutions with the published research. The relations between shallow and deep cavity are revealed as well. The detaching curve of cavity roof with elliptical profile is obtained. In order to facilitate the application of engineering practice, the numerical results are tabulated, which play an important role in tunnel design and stability analysis of roof. The influential factors on potential collapse are taken into consideration. From the results, the impact of various factors on the extent of detaching is seen intuitively.

• International Journal of Computer Science & Network Security
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• v.21 no.11
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• pp.241-247
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• 2021

In the article, an analysis of the factors was carried out, which injected into the efficiency of the function of navigation systems in the minds of unimportance. Carrying out analyzes allowing for the visibility of relevant direct adjustments to the effectiveness of the function Inertial navigation systems in the minds of non-value. The designation of the navigation system was assigned to a complex of navigation systems on ships processing of the vector of navigation parameters, so that they can be victorious in the control systems of the ship's collapse, and the safety of floating is safe.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.501-510
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• 2014

Volcanic eruptions alone may lead to serious natural disasters, but the associated release of water from a caldera lake may be equally damaging. There is both historical and geological evidence of the past eruptions of Mt. Baekdusan, and the volcano, which has not erupted for over 100 years, has recently shown signs of reawakening. Action is required if we are to limit the social, political, cultural, and economic damage of any future eruption. This study aims to identify the area that would be inundated following a volcanic flood from the Cheon-Ji caldera lake that lies within Mt. Baekdusan. A scenario-based numerical analysis was performed to generate a flood hydrograph, and the parameters required were selected following a consideration of historical records from other volcanoes. The amount of water at the outer rim as a function of time was used as an upper boundary condition for the downstream routing process for a period of 10 days. Data from the USGS were used to generate a DEM with a resolution of 100 m, and remotely sensed satellite data from the moderate-resolution imaging spectroradiometer (MODIS) were used to show land cover and use. The simulation was generated using the software FLO-2D and was superposed on the remotely sensed map. The results show that the inundation area would cover about 80% of the urban area near Erdaobaihezhen assuming a 10 m/hr collapse rate, and 98% of the area would be flooded assuming a 100 m/hr collapse rate.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.81-87
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• 2014

Flow characteristics and the operating range of gas velocity was investigated for a two-stage bubbling fluidized-bed (0.1 m-i.d., 1.2 m-high) that had continuous solids feed and discharge. Solids were fed in to the upper fluidized-bed and overflowed into the bed section of the lower fluidized-bed through a standpipe (0.025 m-i.d.). The standpipe was simply a dense solids bed with no mechanical or non-mechanical valves. The solids overflowed the lower bed for discharge. The fluidizing gas was fed to the lower fluidized-bed and the exit gas was also used to fluidize the upper bed. Air was used as fluidizing gas and mixture of coarse (< $1000{\mu}m$ in diameter and $3090kg/m^3$ in apparent density) and fine (< $100{\mu}m$ in diameter and $4400kg/m^3$ in apparent density) particles were used as bed materials. The proportion of fine particles was employed as the experimental variable. The gas velocity of the lower fluidized-bed was defined as collapse velocity in the condition that the standpipe was emptied by upflow gas bypassing from the lower fluidized-bed. It could be used as the maximum operating velocity of the present process. The collapse velocity decreased after an initial increase as the proportion of fine particles increased. The maximum took place at the proportion of fine particles 30%. The trend of the collapse velocity was similar with that of standpipe pressure drop. The collapse velocity was expressed as a function of bulk density of particles and voidage of static bed. It increased with an increase of bulk density, however, decreased with an increase of voidage of static bed.

• Composites Research
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• v.20 no.3
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• pp.8-16
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• 2007

Bending collapse of light-weight square tubes used for vehicle structure components is a dominant failure mode in oblique collision and rollover of vehicles. In this paper bending performances of aluminum-GFRP hybrid tube beams were evaluated in relation with bending deformation behavior and energy absorption characteristics. Aluminum/GFRP hybrid tube beams fabricated by inserting adhesive film between prepreg and metal layer were used in the bending test. Failure mechanisms of hybrid tubes under a bending load were experimentally investigated to analyze the bending performance as a function of ply orientation and composite layer thickness. Ultimate bending moments and energy absorption capacity of hybrid tube beams were obtained from the measured load-displacement corves. It was found that aluminum/GFRP hybrid tubes could be converted to rather stable collapse mode showing excellent energy absorption capacity in comparison to the pure aluminum tube beams. In particular, the hybrid tube beam with $[0^{\circ}/90^{\circ}]s$ composite layer showed a large improvement by about 78% in energy absorption capacity and by 29% in specific energy absorption.

• Korea-Australia Rheology Journal
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• v.20 no.1
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• pp.27-34
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• 2008

Clay suspensions in liquid polymers exhibit a time-dependent behaviour that includes viscoelastic as well as thixotropic features. Because of the presence of interacting clay platelets, particulate networks can develop, which are broken down during flow and rebuild upon cessation of the flow. Here, the use of thixotropic techniques in probing flow-induced structures in nanocomposites is explored with data on a hectorite-poly(isobutylene) model system. By means of fast stress jump measurements the hydrodynamic contributions to the steady state stresses are determined as well as those caused by the stretching of the clay floes. Flow reversal measurements do not provide a clear indication of flow-induced anisotropy in the present case. The recovery of the clay microstructure upon cessation of flow is followed by means of overshoot and dynamic measurements. The development of a particulate network is detected by the appearance and growth of a low frequency plateau of the storage moduli. The modulus-frequency curves after various rest times collapse onto universal master curves, regardless of the pre-shear history or temperature. The scaling factors for this master curve are the crossover parameters. The crossover moduli are nearly a linear function of the crossover frequency, the relation being identical for recovery after shearing at different shear rates. This function depends, however, on temperature.

• Archives of Plastic Surgery
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• v.50 no.5
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• pp.496-500
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• 2023

Fournier's gangrene is a life-threatening infection which requires prompt recognition, early surgical debridement of unhealthy tissue, and initiation of broad-spectrum antibiotics. Relook debridement are usually performed until all the devitalized tissue has been removed. Involvement of the anal sphincter may result in significant morbidity such as permanent incontinence. Dynamic reconstruction of the anal sphincter has always been one of the holy grails in the field of pelvic reconstruction. We demonstrate a new method of camera shutter style double-opposing gracilis muscle flaps that allows dynamic sphincteric function without the need for electrostimulation. The bilateral gracilis muscles are inset in a fashion that allows orthograde contraction of the muscle to narrow and collapse the neoanal opening. With biofeedback training, the patient is able to regain dynamic continence and return to function without a stoma. There was also no need for neurotization or microsurgery techniques to restore sphincteric function to the anus. The patient was able to reverse his stoma 14 months after the initial insult and reconstruction with biofeedback training without the use of electrostimulation.