• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.399-402
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• 2006

The purpose of this study is to propose a method for protecting injector face for prolonged combustion time and heat flux measurement technique at the injector face. To obtain basic design data and verify the performance of the proposed method, a regenerative cooling injector face was designed and manufactured for the hot firing test. Due to the safety reason, hot fire test were performed 3, 10, 30, 60 and 120 seconds time step. The discrepancy between analytical results adapting to combustion and nozzle and experimental results is believed due to the over estimation of the convection heat transfer calculation. for the injector face, flow velocity is almost negligible, therefore radiation is more important than convection. Consecutive hot firing test during 10, 30, 60 and 120 seconds combustion time shows good repeatability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.75-78
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• 2007

In this study, low velocity impact analysis on Turbo Fan Engine composite sandwich structure was performed. Sandwich structure configuration is made of carbon/epoxy face sheets and foam cores. For validating study, the results of an experimental and of a Finite Element Method analysis were compared previously. From the Finite Element Method analysis results of sandwich panel, it was confirmed that the result of analysis was reasonable. Impactor velocity to initiate damage was estimated, and in order to investigate the damage at the predicted velocity, impact analysis using Finite Element Method was performed. According to the impact analysis results of sandwich panel, it was confirmed that the damage was generated at the estimated impact velocity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1071-1076
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• 2006

In this paper, we develop face and hand tracking for sign language recognition system. The system is divided into two stages; the initial and tracking stages. In initial stage, we use the skin feature to localize face and hands of signer. The ellipse model on CbCr space is constructed and used to detect skin color. After the skin regions have been segmented, face and hand blobs are defined by using size and facial feature with the assumption that the movement of face is less than that of hands in this signing scenario. In tracking stage, the motion estimation is applied only hand blobs, in which first and second derivative are used to compute the position of prediction of hands. We observed that there are errors in the value of tracking position between two consecutive frames in which velocity has changed abruptly. To improve the tracking performance, our proposed algorithm compensates the error of tracking position by using adaptive search area to re-compute the hand blobs. The experimental results indicate that our proposed method is able to decrease the prediction error up to 96.87% with negligible increase in computational complexity of up to 4%.

• Journal of the Korea Society for Simulation
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• v.18 no.1
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• pp.17-25
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• 2009

This paper suggests fuzzy-based Segment-Boost method and an effective method for face recognition using the fuzzy-based Segment-Boost. Fuzzy-based Segment-Boost eliminates the limitations of Segment-Boost, and it guarantees improved learning performance and the stability of the performance. By using the fuzzy theory, fuzzy-based Segment-Boost optimizes the selection number of sub-vectors, and leads the optimized learning performance. The fuzzy controller designed in this paper measures learning performance of the fuzzy-based Segment-Boost, and it controls the selection number of sub-vectors by inferring the optimized selection number. The simulation results show that the fuzzy controller inferred the selection number which is very approximate to the true optimized value. As a result, fuzzy-based Segment-Boost showed higher face recognition rate than compared boosting methods and it preserves the velocity of feature selection as fast as that of Segment-Boost. From the experimental results, it was proved that fuzzy-based Segment-Boost has improved and stable performances of learning, feature selection and face recognition.

• Tribology and Lubricants
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• v.21 no.5
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• pp.201-208
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• 2005

This paper presents the FEM analysis on the contact behavior characteristics of mechanical face seals in a small hydro-power turbine. Especially, the axial displacement and contact normal stress between a seal ring and a seal seat of a primary sealing unit have been analyzed as functions of rotating speed of a hydro-turbine, sealing gap, water and cooling fluid temperature. Those are strongly related to a leakage of water and wear between a seal ring and a seal seat. The FEM computed results present that the rotating speed of a hydro-turbine may be kept less than 800 rpm, and the sealing gap in a primary sealing unit is restricted $0.5\~5$. The coolant temperature in which is most influential parameter to the contact behaviors of a sealing unit may be kept less than $15^{\circ}C$ for a safe operation of a sealing unit without a leakage and wear.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1492-1501
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• 2006

A transportation system of single wafer has been developed to be applied to semiconductor manufacturing process of the next generation. In this study, the experimental apparatus consists of two kinds of track, one is for propelling a wafer, so called control track, the other is for generating an air film to transfer a wafer, so called transfer track. The wafer transportation speed has been evaluated by the numerical and the experimental methods for three types of nozzle position a..ay (i.e., the front-, face- and rear-array) in an air levitation system. Test facility for 300mm wafer has been equipped with two control tracks and one transfer track of 1500mm length from the starting point to the stopping point. From the present results, it is found that the experimental values of the wafer transportation speed are well in agreement with the computed ones. Namely, the computed values of the maximum wafer transportation speed $V_{max}$ are slightly higher than the experimental ones by about $15{\times}20%$. The disparities in $V_{max}$ between the numerical and the experimental results become smaller as the air velocity increases. Also, at the same air flow rate, the order of wafer transportation speeds is : $V_{max}$ for the front-array > $V_{max}$ for the face-array > $V_{max}$ for the rear-array. However, the face-array is rather more stable than any other type of nozzle array to ensure safe transportation of a wafer.

• Journal of Korean Neurosurgical Society
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• v.53 no.3
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• pp.180-182
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• 2013

We describe a case of intracranial carotid artery occlusion due to penetrating craniofacial injury by high velocity foreign body that was relieved by decompressive surgery. A 46-year-old man presented with a penetrating wound to his face. A piece of an electric angular grinder disc became lodged in the anterior skull base. Computed tomography revealed that the disc had penetrated the unilateral paraclinoid and suprasellar areas without flow of the intracranial carotid artery on the lesion side. The cavernous sinus was also compromised. Removal of the anterior clinoid process reopened the carotid blood flow, and the injection of glue into the cavernous sinus restored complete hemostasis during extraction of the fragment from the face. Digital subtraction angiography revealed complete recanalization of the carotid artery without any evidence of dissection. Accurate diagnosis regarding the extent of the compromised structures and urgent decompressive surgery with adequate hemostasis minimized the severity of penetrating damage in our patient.

• Steel and Composite Structures
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• v.41 no.6
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• pp.821-829
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• 2021

Nonlinear dynamic response of a sandwich beam considering porous core and nano-composite face sheet on nonlinear viscoelastic foundation with temperature-variable material properties is investigated in this research. The Hamilton's principle and beam theory are used to drive the equations of motion. The nonlinear differential equations of sandwich beam respect to time are obtained to solve nonlinear differential equations by Homotopy perturbation method (HPM). The effects of various parameters such as linear and nonlinear damping coefficient, linear and nonlinear spring constant, shear constant of Pasternak type for elastic foundation, temperature variation, volume fraction of carbon nanotube, porosity distribution and porosity coefficient on nonlinear dynamic response of sandwich beam are presented. The results of this paper could be used to analysis of dynamic modeling for a flexible structure in many industries such as automobiles, Shipbuilding, aircrafts and spacecraft with solar easured at current time step and the velocity and displacement were estimated through linear integration.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.69-79
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• 2008

Prediction of ground condition ahead of tunnel face might be the most important factor to prevent collapse during tunnel excavation. In this study, a non-destructive method to evaluate the phase velocity in model rock mass using wavelet transform of surface wave was proposed aiming at ground condition assessment ahead of tunnel face. Model tests using gypsum as a rocklike material composed of two layers were performed. A Piezoelectric actuator with frequencies ranging from 150 Hz to 5 kHz was selected as a harmonic source. The acceleration history was measured with two accelerometers. Wavelet transform analysis was used to obtain the dispersion curves from the measured data. The experimental results showed that the near-field effects can be neglected if the distance between two receivers is chosen to be three times the wavelength. A simple inversion method using weighted factor based on the normal distribution was proposed. The inversion results showed that the predicted phase velocity agreed reasonably well with the measured one when the wavelength influence factor was 0.2. The depth of propagation of surface wave was from 0.42 to 0.63 times the wavelength. The range of wavelength varying with phase velocity in dispersion curve matched well with that estimated by inversion technique.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.3
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• pp.201-209
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• 2004

Important operation parameters and performance of a high temperature ceramic candle filter system were evaluated through a series of demonstration tests at a pilot-scale vitrification plant. At the initial period of each test, due to the growth of dust cake on the surface of ceramic candles, the pressure drop across the filter media increased sharply. After that it became stable to a certain range and varied continuously proportion to the face velocity of off-gas. On the contrary, at the initial period of each test, the permeability of filter element decreased rapidly and then it became stable. Back flushing of the filter system was effective under the back flushing air pressure range of 3∼5 bar. Based on the dust concentrations measured by iso-kinetic dust sampling at the inlet and outlet point of HTF, the dust collection efficiency of HTF evaluated. The result met the designed performance value of 99.9%. During the demonstration tests including a hundred hour long test, no specific failure or problem affecting the performance of HTF system were observed.