• Proceedings of the Korean Vacuum Society Conference
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• 1994.02a
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• pp.50-50
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• 1994

Half-metallic Heusler alloys (NiMnSb, ppdMnSb, pptMnSb) have attracted much attention due to their unique electronic and magnetic structures. Sppin-ppolarized band structure calculation ppredicts metallic behavior for the majority sppin states and semiconductor behavior for the minority sppin states. We have studied the electronic structures of these half-metallic Heusler alloys by core-level pphotoemission sppectroscoppy of Mn 2pp and 3s XppS sppectra. We found large intensities of Mn 2pp satellites and 3s exchange spplitting comppared with other metal Mn-alloys. These satellite structure can be understood by applying Anderson imppurity model. This fact supports the calculated sppin pprojected ppartial density of states which suggests that the valence electrons be highly sppin ppolarized near Fermi level and that the electrons involved with charge-transfer be mainly minority sppin ones which have semiconducting band structure. The trend of charge transfer energies Δ from ligands (Sb 5pp) to Mn 3d, obtained from our model fitting, is consistent with that calculated from sppin pprojected ppartial density of state. Also the trend of d-d electron correlation energies U calculated from Mn Auger line L3 VV by Mg $K\alpha$ source is comppatible with that resulted from our model fitting. We fitted the Mn 3s curve in the same way as for insulating Mn comppounds by using the same pparameters calculated from Mn 2pp curve fitting exceppt for the Coulomb interaction energy Q between core hole and d-electrons. The 3s sppectra were analyzed by combing the charge transfer model and a simpple model taking into account the configuration mixing effect due to the intra-shell correlation. We found that the exchange interaction between 3s hole and 3d electrons is mainly respponsible for the satellite of Mn 3s sppectra. This is consistent with the neutron scattering data, which suggests local 3d magnetic moment. We find that the XppS analysis results of Mn 2pp and 3s satellite structures of half-metallic Heusler alloys are very similar to those of insulating transition metal comppounds.

• Journal of the Korean GEO-environmental Society
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• v.10 no.2
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• pp.61-68
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• 2009

This paper presents the numerical investigation for the hydraulic behavior of a fractured rock mass with a hydromechanical interaction which may be considered during the in-situ hydraulic injection test. These experiments consist in a series of flow meter injection tests for fractures existing along an open hole section installed in a borehole, and experimental results are applied for testing a numerical model developed to the analysis and prediction of such hydromechanical interactions. Field experimental results show that conductive fractures form a dynamic and interdependent network, that individual fractures cannot be adequately modeled as independent systems, that new fluid intaking zones generate when pore pressure exceeds the minimum principal stress magnitude in that borehole, and that pore pressures much larger than this minimum stress can be further supported by the circulated fractures. In this study, these characteristics are investigated numerically how to influence the morphology of the natural fracture network in a rock mass by using a discrete fracture ntework model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.547-557
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• 2007

This study was conducted to investigate the flow and combustion characteristic of the experimental burner which was manufactured for the reflection of the oven and broil burner features. As slot shape, spacing between slots, and slot arrangement of the exit area which emits the mixing gas are different in case of oven burners and broil turners, the purpose of this study is to know the affection of the flame interaction and combustion characteristic according to the change of shape factors such as slot shape, slot arrangement, and slot-to-slot spacing. With no relation of the slot shape, as the spacing between slots became narrow, the occurrence of a lift-flame was delayed. So the combustion was possible in the leaner region, but the appearance of yellow-tip became a little fast. Slit slot port had the broadest operating range among the other slot shapes. Specially, from the side of lift-flame, as the jet that spreads downstream in the longitudinal slot was nearly circular just a few slot lengths away from the orifice, slot-to-slot spacing of the Slit port was closer than the other ports. These results could be expected through the computer numerical method and had a good agreement. As the spacing between slots increased, in case of Slit and Mix port, NOx emission rate was constant or decreased, but the NOx emission of Hole port was increased. CO emission rate of Slit and Hole port was increased as the slot-to-slot spacing was broadened.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.147-154
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• 2002

The dynamic load caused by sloshing of internal fluid severely affects the structural and control stabilities of cylindrical liquid containers accelerating vertically. If the sloshing frequency of fluid is near the frequency of control system or the tank structure, large dynamic force and moment act on launching vehicles. For the suppression of such dynamic effects, generally flexible ring-type baffles are employed. In this paper, we perform the numerical analysis to evaluate the dynamic suppression effects of baffle. The parametric analysis is performed with respect to the baffle inner-hole diameter and two different baffle spacing types : equal spacing with respect to the tank and one with respect to the fluid height. The ALE (arbitrary Lagrangin-Eulerian) numerical method is adopted for the accurate and effective simulation of the hydrodynamic interaction between fluid and elastic structure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.82-93
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• 2002

The effects of the interaction between the flow and temperature field and a boundary layer due to a variety of the height of a vortex generator are experimentally investigated. The test facility consists of a boundary-layer wind tunnel with the vortex generator protruding from the bottom surface. In order to control the strength of the longitudinal vortices, the angle of attack and the spacing distance of the vortex generator are 20 degree and 40 mm, respectively. The height of the vortex generator (H) is 15 mm, 20 mm and 30 mm and the cord length of it is 50 mm. Three-component mean velocity measurements are made using a 5-hole probe system and the surface temperature distribution is measured by the hue capturing method using thermochromatic liquid crystals. By using the method mentioned above, the following conclusions are obtained from the present experiment. The boundary layer is thinned in the downwash region where the strong downflow and the lateral outflow of the boundary layer fluid occur and thickened in the upwash re,3ion where the longitudinal vortex sweeps low momentum fluid away from the bottom surface. In case that the height of the vortex generator increases, the averaged circulation and the maximum vorticity of the vortex pair decrease. The contours of the non-dimensional temperature show the similar trends fur all the cases (H=15 mm, 20 mm and 30 mm). The peak augmentation of the distribution of the local non-dimensional temperature occurs in the downwash region near the point of minimum boundary-layer thickness.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.153-168
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• 2003

The objective of this present study is to understand long term(500 years) thermohydromechanical interaction behavior in the vicinity of a repository cavern on the joint location and repository depth variations. The model includes a saturated discontinuous granitic rock mass, PWR spent nuclear fuel in a disposal canister surrounded with compacted bentonite inside a deposition hole, and mixed bentonite backfilled in the rest of the space within a repository cavern. It is assumed that two joint sets exist within the model. Joint set 1 includes joints of 56$^{\circ}$ dip angle, spaced at 20 m, and joint set 2 is in the perpendicular direction to joint set 1 and includes joints of 34$^{\circ}$ dip angle, spaced at 20 m. In order to understand the behavior change on the joint location variations, 5 different models of 500m in depth are analyzed, and additional 3 different models of 1000 m in depth are analyzed to understand the effect of depth variation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.211-217
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• 2014

This study analyzes the nonlinear interaction between two different vortex shedding frequencies from a cylinder with two diameters. In particular, two different vortex shedding frequencies are generated by preparing a cylinder having two diameters artificially. Flow velocity fluctuations behind the cylinder are measured three-dimensionally. Additionally, we fabricated a hole and placed a pressure transducer for measuring the pressure on the cylinder surface. The pressure signal from the pressure transducer is used as basic signal. A TSC(Trans Spectrum Coherence) is used for checking the strength of the nonlinear interaction between two different vortex shedding frequencies. As a result, the following are clarified: i) frequency distribution behind the cylinder, ii) three-dimensional flow state behind the cylinder through calculation of ensemble average, and iii) close relationship between the vertical vortex and change of low frequency by nonlinear interaction between two different vortex shedding frequencies from the cylinder with two diameters.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.555-564
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• 1994

This study has been made to investigate the stress distribution around defects and inclusions that behave as stress concentrators. The stress distribution and interation effects around defects and inclusions was analyzed using Finite Element Method. The results are as follows;(1) Maximum stress point in case of $E_I/E_M>1$($E_I$:elasticity modulus forthe inclusion, $E_M$/:elasticity modulus for the base material)is the vertical point with respect to force direction and in case of $E_I/E_M<1$ it is the parallel point along the hole edge. (2) Interaction effects of ${\sigma}_y$ for the inclusion side is larger than the defect side when the interval between inclusion and defect is near. (3) stress interation effects is large if the difference of ${\sigma}_y$ is small and it is small if the difference of ${\sigma}_y$ is large for the case that the interval between inclusion and defect whose size and property are different is near.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.9
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• pp.843-852
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• 2000

The flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices were studied experimentally. The test facility consisted of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta winglet protruding from the surface. In order to control the strength of the longitudinal vortices, the angles of attack of the vortex generators were varied from $\pm20\;degree\;to\;\pm45$ degree, but spacings between the vortex generators were fixed to 4 cm. The 3-dimensional mean velocity measurements were made using a five-hole pressure probe. Heat transfer measurements were made using the thermochromatic liquid to provide the local distribution of the heat transfer coefficient. By using the method mentioned above, the following conclusions were obtained from the present experiment. The boundary layer was thinned in the regions where the secondary flow was directed toward the wall and thickened where it was directed away from the wall. The peak augmentation of the local heat transfer coefficient occurred in the downwash region near the point of minimum boundary-layer thickness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.170-175
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• 2005

The focus of this paper is to observe the aerodynamic and vibration characteristics of the NACA0012 blade(AR=16.6) fixed on the lower surface of the wind tunnel, by changing air speed and the blade's angle of attack. After fixing a slit-typed vortex generator on the front of the blade, it could be observed that the vibrational characteristics caused by interactions between vortex and blade through the 5-hole pilot tubes. And, also, two different blades in stiffness had been prepared for observing those characteristics above in this experiment. The results were compared with the given stiffness of blade, as well. According to the results, it is clear to recognize that the vibration spectrum increases while air speed and angle of attack increase, and, also, less stiffness means bigger vibration spectrum.