• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.4
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• pp.301-308
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• 2016

In this study, a novel method referred as non-marker vision-based displacement measuring system(NVDMS) was introduced in order to measure the displacement of structure. There are two distinct differences between proposed NVDMS and existing vision-based displacement measuring system(VDMS). First, the NVDMS extracts the pixel coordinates of the structure using a feature point not a marker. Second, in the NVDMS, the scaling factor in order to convert the coordinates of a feature points from pixel value to physical value can be calculated by using the external conditions between the camera and the structure, which are distance, angle, and focal length, while the scaling factor for VDMS can be calculated by using the geometry of marker. The free vibration test using the three-stories scale model was conducted in order to analyze the reliability of the displacement data obtained from the NVDMS by comparing the reference data obtained from laser displacement sensor(LDS), and the measurement of dynamic characteristics was proceed using the displacement data. The NVDMS can accurately measure the dynamic displacement of the structure without the marker, and the high reliability of the dynamic characteristics obtained from the NVDMS are secured.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.32-38
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• 2005

FBG sensors have been studied more actively than any other fiber optic sensor because of good multiplexing capabilities among many fiber optic sensors. The demodulation method of FBG sensors is based on the detection of wavelength shift of their sensor peaks and properties such as strain and temperature can be measured by detecting them. However, the signal stability of FBG sensors can be influenced by the strain gradient induced by structural geometry or cracks on the surface when FBG sensors are embedded into or attached on the structure. In this study, the signal characteristics of reflected spectra of FBG sensors under strain gradient were verified and the relations between the grating length of FBG sensors and the amount of strain gradient were investigated. From the experimental results, the recommended working range of FBG sensors under strain gradients was shown quantitatively with respect to grating lengths of them.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.381-382
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• 2002

The Fluid film between the valve plate and the cylinder block was measured by use of a gap sensor and the mercury-cell slip ring unit under real working conditions. During the operating periods, experiments with discharge pressure, revolution speed, and valve geometry was carried out for the fluid film on the valve plate. To investigate the effect of the valve shape, we designed two valve plates each having a different shape; the first valve plate was a plane valve plate. while the second valve plate was a spherical valve plate. It was noted that these two valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rate and the shan torque were also investigated in order to clarify the difference between these two types of valve plates. From the results of this study. we found that the spherical valve plate estimated good fluid film patterns and performance more than the other valve plate in oil hydraulic axial piston pumps.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.33-33
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• 2009

Silicon nano-structures have great potential in bionic sensor applications. Atomic force microscopy (AFM) anodic oxidation have many advantages for the nanostructure fabrication, such as simple process in atmosphere at room temperature, compatibility with conventional Si process. In this work, we fabricated simple FET structures with channel width W~ 10nm (nanowire) and $1{\mu}m$ (nano-ribbon) on ~10, 20 and 100nm-thinned silicon-on-insulator (SOI) wafers in order to investigate the surface effect on the transport characteristics of nano-channel. For further quantitative analysis, we carried out the 2D numerical simulations to investigate the effect of channel surface states on the carrier distribution behavior inside the channel. The simulated 2D cross-sectional structures of fabricated devices had channel heights of H ~ 10, 20, and 100nm, widths of L ~ $1{\mu}m$ and 10nm respectively, where we simultaneously varied the channel surface charge density from $1{\times}10^{-9}$ to $1{\times}10^{-7}C/cm2$. It has been shown that the side-wall charge of nanowire channel mainly affect the I-V characteristics and this was confirmed by the 2D numerical simulations.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.275-278
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• 2000

In this study, the acoustic transducer of a thin circular disc-type with PZT/Metal was designed. The dielectric and piezoelectric properties of $0.5wt\%$ $MnO_2$ and NiO doped 0.1Pb($Mg_{1/3}$$Nb_{2/3}$)$O_3$-$0.45PbTiO_3$-$0.45PbZrO_3$ ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. The acoustic characteristics which is radiated from the acoustic transducer within the finite space was simulated using the finite element method. It has been observed that the characteristics of the sound pressure ard impedance response calculated for the various models of the size and geometry of acoustic transducer.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.415-418
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• 2006

다양한 데이터에 대해 정확한 분석이 요구되는 분야가 증가하면서, 데이터를 효율적으로 가시화하는 방법에 대한 요구도 증가하고 있다. 분석에 효율적인 가시화란 데이터의 특성을 잘 표현함으로써 분석가가 데이터를 직관적으로 이해할 수 있도록 도와주는 것을 말한다. 이를 통해 데이터를 분석하는 시간을 줄이고 정확한 결과를 얻는데 도움을 준다. 본 논문에서는 가스 배관을 검사하기 위한 Geometry 피그（PIG:Pipeline Inspection Gauge)와 MFL 피그로부터 얻어지는 데이터를 다양한 방법으로 가시화하고 분석에 효과적인 가시화와 시스템의 구현에 대해 다룬다. 각 피그의 다중 센서를 통해 얻어온 데이터를 Line graph, Pseudo Color Image, 3D Surface, Polar View, 3D Pipeline View와 같은 다양한 방법으로 가시화하고 view들 간의 동기화 및 사용자 지정 view 배치를 통해 빠르고 정확한 분석을 가능하게 하는 여러 가지 방법에 대해 설명한다.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.205-210
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• 2006

With the development of recent technology such as telematics, LBS, and ubiquitous, the applications of 3D GIS are rapidly increased. As 3D GIS is mainly based on urban models consisting of the realistic digital models of the objects existing in an urban area, demands for urban models and its continuous update is expected to be drastically increased. The purpose of this study is thus to propose more efficient and precise methods to construct urban models with its experimental verification. Applying the proposed methods, the terrain and sophisticated building models are constructed for the area of $270,600m^2$ with 23 buildings in the University of Seoul. For the terrain models, airborne imagery and LIDAR data is used, while the ground imagery is mainly used for the building models. It is found that the generated models reflect the correct geometry of the buildings and terrain surface. The textures of building surfaces, generated automatically using the projective transformation however, are not well-constructed because of being blotted out and shaded by objects such as trees, near buildings, and other obstacles. Consequently, the algorithms on the texture extraction should be improved to construct more realistic 3D models. Furthermore, the inside of buildings should be modeled for various potential applications in the future.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.308-316
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• 2008

For the measurement of liquid level in ship's cargo tank, ballast tank, fuel oil tank and fresh water tank, several types of gauge meter are used such as tubular type, magnetic float type, reflex type transparent type and welding pad type. Among them, magnetic float type gauge meter is environmental friendly device because it is free of power source and maintenance. The main obstacle of the device is relatively large error bound. In this paper, finite element method is used to design and analysis of the magnetic float type gauge meter. The operation of reed switch according to the magnetic field has been successfully described and agreed well with experimental measurement. The optimum geometry with combination of permanent magnet and reed switches are designed to achieve 98 % accuracy of fluid level.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.28.2-28.2
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• 2008

Recently, star sensors have been successfully used as main attitude sensors for attitude control in many satellites. This research presents the star visibility analysis for star trackers and the goal of this analysis is to make sure that the star tracker implementation is suitable to the mission profile and scenario and satisfies the requirement of attitude orbit control system. As a main optical attitude sensor imaging stars, accomodations of a star tracker should be optimized in order to improve the probability of the usage by avoiding the blinding (the unavailability) by the Sun and the Earth. For the analysis, a statistical approach and a time simulation approach are used. The statistical approach is based on the generation of numerous cases, to derive relevant statistics about Earth and Sun proximity probabilites for different lines of sight. The time simulation approach is performed for one orbit to check the statistical result and to refine the statistical result and accomodations of star trackers. In order to perform simulations first of all, an orbit and specific mission profiles of a satellite are set, next the earth proximity probability and the sun proximity probability are calculated by considering the attitude maneuvers and the geometry of the orbit, and then finally the unavailability positions are estimated. As a result, the optimized accomodations of two star trackers are suggested for the low earth orbit satellite.

• Journal of Sensor Science and Technology
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• v.25 no.3
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• pp.229-234
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• 2016

Self-powered neutron detector (SPND) is being widely used to monitor the reactor core of the nuclear power plants. The SPND contains a neutron-sensitive metallic emitter surrounded by a ceramic insulator. Currently, the vanadium (V) SPND has been being developed to be used in OPR1000 nuclear power plants. Some Monte Carlo simulations were accomplished to calculate the initial sensitivity of vanadium emitter material and alumina insulator with a cylindrical geometry. An MCNP code was used to simulate some factors (neutron self-shielding factor and beta escape probability from the emitter) and space charge effect of an insulator necessary to calculate the sensitivity of vanadium detector. The simulation results were compared with some theoretical and experimental values. The method presented here can be used to analyze the optimum design of the vanadium SPND and contribute to the development of TMI (Top-mount In-core Instrumentation) which might be used in the SMART and SMR.