• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.4
• /
• pp.26-31
• /
• 2010

Finding sufficient supplies of clean energy for future is one of the society's most important challenges according to technologies. Alternative renewable energy source such as solar energy can be substituted for exceeding human energy need. The main factor affect to solar performance is a collective intensity. To enhance intensity, suitable equipment is a solar tracker. The solar tracker consists of sun point detector module, mechanical mechanism module with actuator and control system module. This paper presents sun point detector for solar tracker of daylight system. To evaluate the detecting accuracy, an experimental device is implemented. In experimental results, the accuracy of development system has under 0.11%/0.5deg.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.418-421
• /
• 2003

Today, much terminologies such as noise spectrum, Sharpness, contrast, MTF had been defined for Image quality revaluation of radiation Image. Since development of Xeroradiography In the 1970s, Digital radiation detector that use amorphous selenium was developed. The aim of this research is to analyze physical phenomenon of digital radiation detector that use amorphous selenium. Result of Monte Carlo simulations on amorphous selenium based on physical properties(creation of electron-hole pairs) by induced x-ray are described. From the simulation, intrinsic point spread function(PSF) was found and used to observe modulation transfer function(MTF). We investigated how PSF and MTF changed with various x-ray energy. This result can be used to design digital x-ray detector based on a-Se.

• Nuclear Engineering and Technology
• /
• v.52 no.11
• /
• pp.2601-2606
• /
• 2020

In this study, we expanded the performance of the existing EXVol code and performed empirical experiments and calculations. A high-resolution gamma spectroscopy system was constructed, and a standard point source and a standard volume source were measured with an HPGe detector with 43.1% relative efficiency. EXVol was verified by quantitative comparison of the detection efficiencies determined by measurements and calculations. To introduce the concept of the detector scanning that occurs in the actual measurement into the EXVol code, a collimator was placed between the source and detector. The detection efficiency was determined in the asymmetric arrangement of the source and detector with a collimator. A collimator made of lead with a diameter of 15 mm and a thickness of 50 mm was installed between the source and the detector to determine the detection efficiency at a specific location. The calculation result was contour plotted so that the distribution of detection efficiency could be visually confirmed. The relative deviation between the measurements and calculations for the coaxial and asymmetric structures was 10%, and that for the collimation structure was 20%. The results of this study can be applied to research using γ-ray measurements.

• The Journal of the Korea Contents Association
• /
• v.10 no.2
• /
• pp.72-80
• /
• 2010

The 1Gbps clock and data recovery (CDR) circuit using the proposed multi-point phase detector (PD) is presented. The proposed phase detector generates up/down signals comparing 3-point that is data transition point and clock rising/falling edge. The conventional PD uses the pulse width modulation (PWM) that controls the voltage controlled oscillator (VCO) using the width of a pulse period's multiple. However, the proposed PD uses the pulse number modulation (PNM) that regulates the VCO with the number of half clock cycle pulse. Therefore the proposed PD can controls VCO preciously and reduces the jitter. The CDR circuit is tested using 1Gbps $2^{31}-1$ pseudo random bit sequence (PRBS) input data. The designed CDR circuit shows that is capable of recovering clock and data at rates of 1Gbps. The recovered clock jitter is 7.36ps at 1GHz and the total power consumption is about 12mW. The proposed circuit is implemented using a 0.18um CMOS process under 1.8V supply.

• Journal of Multimedia Information System
• /
• v.4 no.4
• /
• pp.285-288
• /
• 2017

In this paper, we propose a vision-based object detection and tracking system using online learning. The proposed system adopts a feature point-based method for tracking a series of inter-frame movement of a newly detected object, to estimate rapidly and toughness. At the same time, it trains the detector for the object being tracked online. Temporarily using the result of the failure detector to the object, it initializes the tracker back tracks to enable the robust tracking. In particular, it reduced the processing time by improving the method of updating the appearance models of the objects to increase the tracking performance of the system. Using a data set obtained in a variety of settings, we evaluate the performance of the proposed system in terms of processing time.

• Proceedings of the KSRS Conference
• /
• 2007.10a
• /
• pp.540-543
• /
• 2007

The modulation transfer function (MTF) in a camera system is a measurement of how well the system will faithfully reproduce the original scene. The electro-optical camera system consists of optics, an array of pixels, and an electronics which is related to the image signal chain. The system MTF can be cascaded with each element's MTF in the frequency domain. That is to say, the electronics MTF including the detector MTF can be recalculated easily by the acquired system MTF if the well-known test optics is used in the measuring process. A Time-Delay and Integration (TDI) detector can make a signal increase by taking multiple exposures of the same object and adding them. It can be considered the various methods to measure the MTF of the TDI camera system. This paper shows the actual and practical MTF measuring methods for the detector and electronics in the TDI camera. The several methods are described according to the scan direction as well as the TDI stages such as the single line mode and the multiple-lines mode. The measuring is performed in the in the static condition or dynamic condition to get the point spread function (PSF) or the line spread function (LSF). Especially, the dynamic test bench is used to simulate on track velocity to synchronize with TDI read out frequency for the dynamic movement.

• Analytical Science and Technology
• /
• v.5 no.1
• /
• pp.57-61
• /
• 1992

For the neutron spectrum measurement, $^6Li$ neutron spectrometer system is installed. The characteristic of the $^6Li$ detector are investigated using a $^{137}Cs$ and $^{207}Bi$ point source, and the neutron capture peaks and the pulse height spectrum using an $^{214}Am-Be$ neutron source are measured. Furthermore, the pulse height spectrum for the irradiation time variation from the (214)^Am-Be neutron source, and for the distance variation between detector and source, and the threshold variation of discriminator are measured.

• Imaging Science in Dentistry
• /
• v.39 no.1
• /
• pp.27-33
• /
• 2009

Purpose: The purpose of this study was to evaluate the clinical usefulness of the recently developed multi-detector computed tomography and cone beam computed tomography in pre-operative implant evaluation, by comparing them with the single detector computed tomography, already confirmed for accuracy in this area. Materials and Methods: Five partially edentulous dry human mandibles, with $1{\times}1mm$ gutta percha cones, placed in 5mm intervals posterior to the mental foramen on each side of the buccal part of the mandible, were used in this study. They were scanned as follows: 1) Single detector computed tomography: slice thickness 1mm, 200mA, 120kV 2) Multi-detector computed tomography: slice thickness 0.75mm, 250mA, 120kV 3) Cone beam computed tomography: 15mAs, 120kV Axial images acquired from three computed tomographies were transferred to personal computer, and then reformatted cross-sectional images were generated using V-Implant $2.0^{(R)}$ (CyberMed Inc., Seoul, Korea) software. Among the cross-sectional images of the gutta perch a cone, placed in the buccal body of the mandible, the most precise cross section was selected as the measuring point and the distance from the most superior border of the mandibular canal to the alveolar crest was measured and analyzed 10 times by a dentist. Results: There were no significant intraobserver differences in the distance from the most superior border of the mandibular canal to the alveolar crest (p>0.05). There were no significant differences among single detector computed tomography, multi-detector computed tomography and cone beam computed tomography in the distance from the most superior border of the mandibular canal to the alveolar crest (p>0.05). Conclusion: Multi-detector computed tomography and cone beam computed tomography are clinically useful in the evaluation of pre-operative site for mandibular dental implants, with consideration for radiation exposure dose and scanning time.

• Nuclear Engineering and Technology
• /
• v.43 no.1
• /
• pp.13-18
• /
• 2011

In this study, simulations were done of a 661.6 keV line from a point source of $^{137}Cs$ housed in a lead shield. When increasing the scattering angle from 60 to 120 degrees with a 6061 aluminum alloy target placed at angles of 30 and 45 degrees to the incident beam, the spectra showed that the single scattering component increases and that the multiple scattering component decreases. The investigation of the single and multiple scattering components was carried out using a MCNP5 simulation code. The component of the single Compton scattering photons is proportional to the target electron density at the point where the scattering occurs. The single scattering peak increases according to the thickness of the target and saturates at a certain thickness. The signal-to-noise ratio was found to decrease according to the target thickness. The simulation was experimentally validated by measurements. These results will be used to determine the best conditions under which this method can be applied to testing electron densities or to assess the thickness of samples to locate defects in them.

• Proceedings of the KSRS Conference
• /
• 1999.11a
• /
• pp.349-354
• /
• 1999

Electro-Optical Camera (EOC) is the main payload of the KOMPSAT-1 satellite to perform the mission of cartography that builds up a digital map of Korean territory including a digital terrain elevation map. This paper discusses the issues of the digital image simulation of EOC for the generation of EOC simulated scene as taken by EOC at 685km altitude on orbit. For the purpose, simulation work has been performed with the sensor models of EOC and the satellite platform motions models through image chain analysis from the illumination source (Sun) to a simulated image output in digital number. MODTRAN fur radiance calculation, MTF models of optics, detector and motions of EOC for system point spread function (PSF), and signal chain equations for digital number output are described. Several noise models of EOC are also considered. The final output is the EOC simulated image in digital number. The simulation technique can be used in several phase of a spaceborne electro-optical system development project, feasibility study phase, design, manufacturing, test phases, ground image processing phases, and so on.