• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.37-47
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• 2009

For the inspection of wood, machine vision is the most common automated inspection method used at present. It is required to sort wood products by grade and to locate surface defects prior to cut-up. Many different sensing methods have been applied to inspection of wood including optical, ultrasonic, X-ray sensing in the wood industry. Nowadays the scanning system mainly employs CCD line-scan camera to meet the needs of accurate detection of lumber defects and real-time image processing. But this system needs exact feeding system and low deviation of lumber thickness. In this study low cost CCD area sensor was used for the development of image processing system for lumber being fed. When domestic red pine being fed on the conveyer belt, lumber images of irregular term of captured area were acquired because belt conveyor slipped between belt and roller. To overcome incorrect image merging by the unstable feeding speed of belt conveyor, it was applied template matching algorithm which was a measure of the similarity between the pattern of current image and the next one. Feeding the lumber over 13.8 m/min, general area sensor generates unreadable image pattern by the motion blur. The red channel of RGB filter showed a good performance for removing background of the green conveyor belt from merged image. Threshold value reduction method that was a image-based thresholding algorithm performed well for knot detection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.33-43
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• 2010

Recently, users want to use real-time multimedia services, such as internet, VoIP, etc., using their IEEE 802.11 wireless lan mobile stations. In order to provide such services, a handoff among access points is essential to support the mobility of a node, in such an wide area. However, the legacy handoff methods of IEEE 802.11 technology are easy to lose connections. Also, the recognition of a disconnection and channel re-searching time make the major delay of the next AP to connect. In addition, because IEEE 802.11 decides the selection of an AP depending only on received signal strength, regardless of a node direction, position, etc., it cannot guarantee a stable bandwidth for communication. Therefore, in order to provide a real-time multimedia service, a node must reduce the disconnection time and needs an appropriate algorithm to support a sufficient communication bandwidth. In this paper, we suggest an algorithm which predicts a handoff point of a moving node by using GPS location information, and guarantees a high transmission bandwidth according to the signal strength and the distance. We implemented the suggested algorithm, and confirmed the superiority of our algorithm by reducing around 3.7ms of the layer-2 disconnection time, and guaranteed 24.8% of the communication bandwidth.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.6
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• pp.467-478
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• 2019

This paper describes the development and measurement results of a wide-band planar active phase array antenna system for an electronic warfare jamming transmitter. The system is designed as an $8{\times}8$ triangular lattice array using a $45^{\circ}$ slant wide-band antenna. The 64-element transmission channel is composed of a wide-band gallium nitride(GaN) solid state power amplifier and a gallium arsenide(GaAs) multi-function core chip(MFC). Each GaAs MFC includes a true-time delay circuit to avoid a wide-band beam squint, a digital attenuator, and a GaAs drive amplifier to electronically steer the transmitted beam over a ${\pm}45^{\circ}$ azimuth angle and ${\pm}25^{\circ}$ elevation angle scan. Measurement of the transmitted beam pattern is conducted using a near-field measurement facility. The EIRP of the designed system, which is 9.8 dB more than the target EIRP performance(P), and the ${\pm}45^{\circ}$ azimuth and ${\pm}25^{\circ}$ elevation beam steering fulfill the desired specifications.

• Advances in nano research
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• v.13 no.6
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• pp.575-585
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• 2022

Due to its biofilm formation and colonization of the osteocyte-lacuno canalicular network (OLCN), Staphylococcus aureus (S.aureus) implant-associated bone infection (SIABI) is difficult to cure thoroughly, and may occur recurrently subsequently after a long period dormant. It is essential to explore an alternative therapeutic strategy that can eradicate the pathogens in the infected foci. To address this, the polymethylmethacrylate (PMMA) bone cement and Fe3O4 nanoparticles compound cylinder were developed as implants based on their size and mechanical properties for the alternative magnetic field (AMF) induced thermal ablation, The PMMA mixed with optimized 2% Fe₃O₄ nanoparticles showed an excellent antibacterial efficacy in vitro. It was evaluated by the CFU, CT scan and histopathological staining on a rabbit 1-stage transtibial screw model. The results showed that on week 7, the CFU of infected soft tissue and implants, and the white blood cells (WBCs) of the PMMA+2% Fe₃O₄+AMF group decreased significantly from their controls (p<0.05). PMMA+2% Fe₃O₄+AMF group did not observe bone resorption, periosteal reaction, and infectious reactive bone formation by CT images. Further histopathological H&E and Gram Staining confirmed there was no obvious inflammatory cell infiltration, neither pathogens residue nor noticeably burn damage around the infected screw channel in the PMMA+2% Fe₃O₄+AMF group. Further investigation of nanoparticle distributions in bone marrow medullary and vital organs of heart, liver, spleen, lung, and kidney. There were no significantly extra Fe₃O₄ nanoparticles were observed in the medullary cavity and all vital organs either. In the current study, PMMA+2% Fe₃O₄+AMF shows promising therapeutic potential for SIABI by providing excellent mechanical support, and promising efficacy of eradicating the residual pathogenic bacteria in bone infected lesions.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.161-170
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• 2009

Purpose : A parallel imaging method provides us to improve temporal resolution to obtain three-dimensional (3D) MR images. The objective of this study was to optimize three 3D MRI techniques by adjusting 2D SESNE factors of the parallel imaging method in phantom and human brain. Materials and Methods : With a 3 Tesla MRI system and an 8-channel phase-array sensitivity-encoding (SENSE) coil, three 3D MRI techniques of 3D T1-weighted imaging (3D T1WI), 3D T2-weighted imaging (3D T2WI) and 3D fluid attenuated inversion recovery (3D FLAIR) imaging were optimized with adjusting SESNE factors in a water phantom and three human brains. The 2D SENSE factor was applied on the phase-encoding and the slice-encoding directions. Signal-to-noise ratio(SNR), percent signal reduction rate(%R), and contrast-to-noise ratio(CNR) were calculated by using signal intensities obtained in specific regions-of-interest (ROI). Results : In the phantom study, SENSE factor = 3 was provided in 0.2% reduction of signals against without using SENSE with imaging within 5 minutes for 3D T1WI. SENSE factor = 2 was provided in 0.98% signal reduction against without using SENSE with imaging within 5 minutes for 3D T2WI. SENSE factor = 4 was provided in 0.2% signal reduction against without using SENSE with imaging around 6 minutes for 3D FLAIR. In the human brain study, SNR and CNR were higher with SENSE factors = 3 than 4 for all three imaging techniques. Conclusion : This study was performed to optimize 2D SENSE factors in the three 3D MRI techniques that can be scanned in clinical time limitations with minimizing SNR reductions. Without compromising SNR and CNR, the optimum 2D SENSE factors were 3 and 4, yielding the scan time of about 5 to 6 minutes. Further studies are necessary to optimize 3D MRI techniques in other areas in human body.

• Atmosphere
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• v.12 no.4
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• pp.20-42
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• 2002

Based on the "Mid to Long Term Plan for Space Development", a project to launch COMeS (Communication, Oceanography, and Meteorological Satellite) into the geostationary orbit is undergoing. Accordingly, KMA (Korea Meteorological Administration) has defined the meteorological missions and prepared the user requirements to fulfill the missions. To make a realistic user requirements, we prepared a first draft based on the ideal meteorological products derivable from a geostationary platform and sent the RFI (request for information) to the sensor manufacturers. Based on the responses to the RFI and other considerations, we revised the user requirement to be a realistic plan for the 2008 launch of the satellite. This manuscript introduces the revised user requirements briefly. The major mission defined in the revised user requirement is the augmentation of the detection and prediction ability of the severe weather phenomena, especially around the Korean Peninsula. The required payload is an enhanced Imager, which includes the major observation channels of the current geostationary sounder. To derive the required meteorological products from the Imager, at least 12 channels are required with the optimum of 16 channels. The minimum 12 channels are 6 wavelength bands used for current geostationary satellite, and additional channels in two visible bands, a near infrared band, two water vapor bands and one ozone absorption band. From these enhanced channel observation, we are going to derive and utilize the information of water vapor, stability index, wind field, and analysis of special weather phenomena such as the yellow sand event in addition to the standard derived products from the current geostationary Imager data. For a better temporal coverage, the Imager is required to acquire the full disk data within 15 minutes and to have the rapid scan mode for the limited area coverage. The required thresholds of spatial resolutions are 1 km and 2 km for visible and infrared channels, respectively, while the target resolutions are 0.5 km and 1 km.