• The Journal of the Korea Contents Association
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• v.15 no.7
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• pp.289-299
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• 2015

The purpose of this study is to evaluate and compare the quality of digital X-ray imaging system. The image quality evaluation was conducted By using Modulation transfer function indicating the quantitative resolution of the image and the noise power spectrum showing the noise characteristics. Using a IEC61267 radiation quality was applied to the geometry to be used in clinical and geometry presented in IEC62220-1 and Additional filter, grid, the clinical dose and the MTF value of edge phantom was measured. Result of the MTF corresponding to each item(Grid, Filter, SID, kVp, mAs), the clinical condition 100cm, 180cm, measurements of the spatial frequency of the MTF IEC62220-1Geometry 150cm became similarly apparent, rather spatial frequency was also the case high in clinical conditions 100cm. NPS results, as the dose(mAs) is increased, NPS showed that reduced. The image quality evaluation using IEC61267 the Radiation quality, Image quality of the video using the clinical conditions Geometry than image quality evaluation using IEC62220-1Geometry was better. It shows that MTF and NPC in IEC and clinical condition were not significantly different. In order to apply the evaluation method of image quality applied with clinical conditions rather than the future method, to be presented evaluation of IEC standard, based on the results of the image characterization studies in this paper, the methods that shows good quality of spatial resolution and decrease NPS value as the least dose, used suitable parameters for whether or not using added filter, grid, change SID and clinical quality(kVp), dose(mAs) etc should be found. then It is believed to be able to properly maintain the actual quality of the image of the digital radiographic imaging system in clinical.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.613-623
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• 2000

Digital TV tuner for 8-VSB modulation was developed with satisfying the requirements of ATSC. The double frequency conversion and the active tracking filter in the front-end were used to reduce interference of the adjacent channels and multi-channels, which suppress If beat and image band. However, it was impossible to get frequency mapping between tracking filter and first VCO(Voltage Controlled Oscillator) in the double conversion digital TV tuner differing from conventional NTSC tuner. This paper, therefore, suggests the available structure and a new method for automatic frequency selection by obtaining the mapping of frequency characteristic over tracking voltage and the combined hardware which compose of Micro-controller, EEPROM, D/A(Digital-to-Analog Converter), OP amp and switch driver to solve above problems.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.11-21
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• 1999

This paper has been proposed a structure composed of FIRs and IIR filters as digital interpolation filter to integrate the off-chip analog low-pass filter of audio DAC. The passband ripple (>$0.41{\times}fs$), passband attenuation(>at$0.41{\times}fs$) and stopband attenuation(<$0.59{\times}fs$) of the ${\Delta}{\Sigma}$ modulator output using the proposed digital interpolation filter had ${\pm}0.001[dB]$, -0.0025[dB] and -75[dB], respectively. Also the inband group delay was 30.07/fs[s] and the error of group delay was 0.1672%. Also, the attenuation of stopband has been increased -20[dB] approximately at 65[kHz], out-of-band. Therefore the RC products of analog low-pass filter on chip have been decreased compared with the conventional digital interpolation filter structure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1985-1992
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• 2011

PE(Passive Entry) is an automotive technology which allows a driver to lock and unlock door of vehicle without using smart key buttons personally. PG(Pssive Go) is an automotive technology which offers the ability to start and stop the engine when there is a driver in vehicle with smart key. When these two functions are unified, we call it PEG(Passive Entry/Go). LF(Low Frequency) antenna driver which is one of core technologies in PEG is composed of a digital part which processes commands and an analog part which generates sine waveform. The digital part of antenna driver receives commands from MCU(or ECU), and processes requested commands by MCU, and stores antenna-related driver commands and data on an internal FIFO block. The digital part takes corresponding actions for commands read from FIFO and then transfers modulated LF data to analog part. The analog part generates sine waveform and transmits outside through antenna. The designed digital part for LF antenna driver can acomplish faster LF data transmission than that of conventional product. LF antenna driver can be applicable to the areas such as PEG for automotive and gate opening and closing of building.

• Korean Journal of Digital Imaging in Medicine
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• v.8 no.1
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• pp.51-55
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• 2006

The effects of Asaddition in amorphous selenium(a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating(MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, j$_{sc}$ in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic(As) additions have been obtained. We have found an Increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1696-1703
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• 2010

Increased demand for military satellite communications system and due to the depletion of resources of existing satellite communications frequencies, Ka-band and EHF-band satellite communication systems is growing demand for development. As a result, the study of rain attenuation mitigation for Ka/EHF-band frequencies has been achieved. The method to compensate rain attenuation on Ka-band(20/30) using the signal power measurement function in Digital Transponder of Next Military Satellite has been proposed in this paper. This method is more effective than generally used method by Beacon and UPC(uplink power control) in giving the precise rain attenuation measurement and correction.

• Journal of Broadcast Engineering
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• v.9 no.4 s.25
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• pp.357-370
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• 2004

In this paper we propose Digital Signal Processing (DSP) techniques for the Equalization Digital On-Channel Repeater(EDOCR) in the ATSC digital TV (DTV) System. DSP techniques consist of demodulation. baseband equalization, and remodulation. Since the time delay caused by signal processing in the EDOCR can seriously affect the performance of ATSC legacy receivers, it is required that the processing time should be minimized as much as possible. To achieve this goal, we focus on the reduction of the EDOCR's time delay with the minimization of its performance degradation. In addition, we present recommended proper parameters for hardware implementation based on extensive simulation result.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.1
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• pp.49-66
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• 2022

The COVID-19 pandemic has led many countries around the world to introduce and employ a digital certificate system to prevent infectious diseases, however, there are difficulties in using the compatible digital certificate between countries in that the international standards of the system have not been developed. Accordingly, we propose an improved system, comparing two methods of presenting a certificate, existing QR code-based and a short-range wireless communication-based certificates. The proposed system is a digital certificate system against the spread of infectious disease by storing verification information of the certificate using decentralized identity-based technology on the blockchain. Blockchain-based trust anchor improves security by solving the problem of forgery and alteration of certificates and guaranteeing the identity of certificate issuers and presenters. This system is also expected to enhance usability providing concurrent verification of a number of certificates(vaccination certificates, recovery certificates, test results, identity certificates, etc.) in a single certificate presentation.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.768-773
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• 2009

This paper demonstrates the digital communication in air using the parametric array. The stepped-plate transducer which is suitable for high-power and high-efficient radiation is used to generate the difference frequency wave with the parametric array. The primary frequencies are selected to 83 kHz and 122 kHz and the resulting difference frequency wave at the frequency of 39 kHz is used for the communication. The modulation method is selected to On-Off Keying method. The waveform and signal-to-noise ratio (SNR) is measured and analyzed to see the characteristics of the digital communication using the parametric array. The proper distance for the communication using parametric array is about 3 m. The measured beam width of the 3dB SNR reduction was $14^{\circ}$. The possibility of the communication in air using the parametric array is confirmed and the high directional characteristic of the communication using the parametric array is expected to have the advantages for the multi path and the security problems.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.122-132
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• 2010

AT-DMB system has been developed to increase data rate up to double of conventional T-DMB in the same bandwidth while maintaining backward compatibility. The AT-DMB system adopted hierarchical modulation which adds BPSK or QPSK signal as enhancement layer to existing DQPSK signal. The enhancement layer signal should be small enough to maintain backward compatibility and to minimize the coverage loss of conventional T-DMB service coverage. But this causes the enhancement layer signal of AT-DMB susceptible to fading effect in transmission channel. A turbo code which has improved error correction capability than convolutional code, is applied to the enhancement layer signal of the AT-DMB system for compensating channel distortion. However there is a need for other solutions for better reception of AT-DMB signal in receiver side without increasing transmitting power. In this paper, we propose adaptive array antenna system with Eigen-space beamforming algorithm which benefits beamforming gain along with diversity gain. We analyzed the reception performances of AT-DMB system in indoor and mobile environments when this new smart antenna system and algorithm is introduced. The computer simulation results are presented along with analysis comments.