• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.4 s.310
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• pp.35-44
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• 2006

The network induced transmission delay deteriorates the performance and stability of the real-time distributed control system on LonWorks over IP (LonWorks/IP) virtual device network (VDN). LonWorks/IP virtual device network is an integrated form of LonWorks device network and IP data network. The time delay in servo control on the LonWorks/IP-based VDN has highly stochastic nature. In the real-time distributed servo applications for predictive maintenance on the factory floor, timely response is essential.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.359-365
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• 2011

A mobile surveillance robot is defined as a surveillance robot system that is mounted on a mobile platform and is used to protect public areas such as airports or harbors from invaders. The mobile surveillance robot that is mounted on a mobile platform consists of a gun module, a camera system module, an embedded control system, and AHRS (Attitude and Heading Reference System). It has two axis control systems for controlling its elevation and azimuth. In order to obtain stable images for targeting invaders, this system requires a stabilizer to compensate any disturbance due to vehicle motion. In this study, a virtual model of a mobile surveillance robot has been created and ADAMS/Matlab simulations have been performed to verify the suitability of the proposed stabilization algorithm. Further, the suitability of the stabilization algorithm has also been verified using a mock-up of the mobile surveillance robot and a 6-DOF (Degree Of Freedom) motion simulator.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.139-139
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• 2010

Ionic Transition Metal Complex based (iTMC) Light-emitting electrochemical cells (LEECs) have been drawn attention for cheap and easy-to-fabricate light-emitting device. LEEC is one of the promising candidate for next generation display and solid-state lighting applications which can cover the defects of current commercial OLEDs like complicated fabrication process and strong work-function dependent sturucture. We have investigated the performance characteristics of LEECs based on poly (3, 4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-incorporated transition metal complex, which is tris(2, 2'-bipyridyl)ruthenium(II) hexafluorophosphate in this study. There are advantages using conductive polymer-incorporated luminous layer to prevent light disturbance and absorbance while light-emitting process between light-emitting layer and transparent electrode like ITO. The devices were fabricated as sandwiched structure and light-emitting layer was deposited approximately 40nm thickness by spin coating and aluminum electrode was deposited using thermal evaporation process under the vacuum condition (10-3Pa). Current density and light intensity were measured using optical spectrometer, and surface morphology changes of the luminous layer were observed using XRD and AFM varying contents of PEDOT:PSS in the Ruthenium(II) complex solution. To observe enhanced ionic conductivity of PEDOT:PSS and luminous layer, space-charge-limited-currents model was introduced and it showed that the performances and stability of LEECs were improved. Main discussions are the followings. First, relationship between film thickness and performance characteristics of device was considered. Secondly, light-emitting behavior when PEDOT:PSS layer on the ITO, as a buffer, was introduced to iTMC LEECs. Finally, electrical properties including carrier mobility, current density-voltage, light intensity-voltage, response time and turn-on voltages were investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1128-1138
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• 2010

One of the typical problems in the precise vibration is resonance characteristics at low frequency disturbance due to a heavy mass. An electro-magnetic(EM) air spring is a kind of vibration control unit and active isolator. The EM air spring in this study aims at removing the low frequency resonance for semiconductor manufacturing. The mechanical and electronic parts in the active isolator are designed to operate under a weight of 2.5 tons. The EM spring is floated using air pressure in a pneumatic elastic chamber and actuated by EM levitation force. The actuator consists of a EM coil and a permanent magnetic plate which are installed inside of the chamber. An air mount was constructed for the experiment with a stone surface plate, 4 active air springs, 4 gap sensors, a DSP controller, and a multi-channel power amp. A PD control method and operating logic was applied to the DSP. Simulation using 1/4 model was carried out and compared with the experiments. The time duration and maximum peak at resonance frequency can be reduced sharply by the proposed system. The results show that the active system can avoid the resonance caused by the natural frequency of the passive system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.183-191
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• 2006

The accuracy of the upward continuation is assessed through the gravity modeling using an ultra-high degree spherical harmonic expansion. The difficulties in the numerical calculation of Legendre function with ultra-high degree, underflow and/or overflow, is successfully resolved in 128 bit calculation scheme. Using the generated Legendre function, the gravity anomaly with spatial resolution of $1'{\times}1'$ on the geoid is calculated. The generated gravity anomaly is degraded and extracted with various noise levels and data intervals, then upward continuation is applied to each data sets. The comparison between the upward continued gravity disturbances and the directly calculated from the spherical harmonics showed that the accuracy on the direct method was significantly better than that of Poisson method. In addition, it is verified that the denser and less noised gravity data on the geoid generates better gravity disturbance vectors at an altitude. Especially, it is found that the gravity noise level less than 5mGal, and the data interval less than 2arcmin is necessary for next generation precision INS navigation which requires the accuracy of 5mGal or better at an altitude.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.92-100
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• 2002

In this study, transonic/supersonic nonlinear flutter analysis system of a complete aircraft including forced harmonic motion pf control surfaces has been effectively developed using the modified transonic small disturbance (TSD) equation. To consider the nonlinear effects, the coupled time marching method (CTM) combining computational structural dynamics (CFD) has been directly applied for aeroelastic computations. The grid system for a complex full aircraft configuration is effectively generated by the developed inhouse code. Intransonic and supersonic flight regimes, the characteristics of static and dynamic aeroelastic effect has been investigated for a complete aircraft model. Also, nonlinear flutter flight simulations for the forced harmonic motion of control surfaces are practically presented in detail.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.79-88
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• 2015

In any production and construction of geospatial information covering surveying, survey control point is a vital geospatial information. Survey control points in South Korea are currently classified as following: national control points, public control points, and cadastral control points. Each of these different categories of survey control points act as a basis and sets perimeters for the production, management and operation of subjects within the category. Universal standard, the unified format between different survey control points, also, are not yet defined, causing difference in basic information provided by altering categories and disturbance in connecting, managing, utilizing and operating survey control points. Establishment of a standard regarding survey control points, is therefore required for the efficacy of their utilization. This study, to solve such inadequacies, selects management items for creation of standardized survey control point, by investigating domestically and internationally the status of operating survey control points, determining data model for management, establishing TTA and agency standards, and establishing of activation methodology for survey control point standards.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.21-27
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• 2012

Estimating the thermal conductivity of clayey soils is important for enhancing the performance of geoengineering structures in cold regions and clay barriers for nuclear waste repositories, but specimen disturbance, saturation, and heat boundary conditions of the test apparatus hinder reliable measurements of the thermal conductivity of saturated clayey soils. This paper presents the results of an experimental study carried out using modified consolidation tests with the needle probe method to measure thermal conductivity. Experimental consolidation tests with saturated kaolinite were performed to investigate the effect of effective stress and dry density on thermal conductivity for saturated kaolinite. In addition, thermal conductivity of soil particles were thoroughly investigated and experimental results were used to evaluate the accuracy of the models to predict thermal conductivity.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.48-59
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• 1992

In this paper, the effects of a skirt deformation on the responses of an Air Cushion Vehicle in waves are investigated. The air in the bag and in the plenum chamber is assumed to be compressible and to have a uniform instantaneous pressure distribution in each volume. The free surface deformation is determined in the framework of linear potential theory by replacing the cushion pressure with the pressure patch moving uniformly with an oscillating strength. And the bag-finger skirt is assumed to be deformed due to the pressure disturbance while its surface area remained constant. The restoring force and moment due to the deformation of bag-finger skirt from the equilibrium shape is included in the equations of hearse and pitch motions. The numerical results of motion responses due to various ratios of the bag and cushion pressure or bag-to-finger depth ratios are shown.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.337-346
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• 1996

The patency of small size vascular grafts is poor, and the blood flow characteristics in the artery graft anastomosis are suspected as one of the important factors influencing intimal hyperplasia. Disturbed flow patterns caused by sixte and compliance mismatch generate unfavorable flow environment which promotes intimal thickening. Tapered vascular yuts are suggested in order to reduce sudden expansion near the anastomosis. The photochromic flow visualization method is used to measure the flout fields in the end-to-end anastomosis model under the carotid and femoral artery flow wave form. The results show that flow disturbance near the anastomosis is diminished in the tapered grafts comparing to the tubular graft. As the divergent ang1e decreases, we can reduce the low and oscillatory wall shear stress zone which is prone to intimal hyperplasia. The flow wave form effects the wall shear rate dis- tribution significantly. The steep deceleration and back flow in the femoral flow wAve form cause low mean wall shear rate and high oscillatory shear index.