• Progress in Medical Physics
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• v.15 no.4
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• pp.179-185
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• 2004

To deal with tumor motion from respiration is one of the important issues for the advanced treatment techniques, such as the intensity modulated radiation therapy (IMRT), the image guided radiation therapy (IGRT), the three dimensional conformal therapy (3D-CRT) and the Cyber Knife. Studies including the active breath control (ABC) and the gated radiation therapy have been reported. Authors have developed the device for reducing the respiration effects and the diaphragm motions with this device were observed to determined the effectiveness of the device. The device consists of four belts to immobilize diaphragm motion and the vacuum cushion. Diaphragm motions without and with device were monitored fluoroscopically. Diaphragm motion ranges were found to be 1.14 ～ 3.14 cm (average 2.14 cm) without the device and 0.72～1.95 cm (average 1.16 cm) with the device. The motion ranges were decreased 20 ～ 68.4% (average 44.9%.) However, the respiration cycle was increased from 4.4 seconds to 3.7 seconds. The CTV-PTV margin could be decreased significantly with the device developed in this study, which may be applied to the treatments of the tumor sited diaphragm region.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.11-18
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• 2019

This paper explores desirable status of block chain electronic government in relation to the prevention of cybercrimes and corruption. After the research, we suggest four measures to establish desirable status of block chain electronic government. Eventually, transparency is ensured thanks to the core concept of block chain technology, sharing, not only allowing all of the participants to share information and but also preventing them from forging or falsifying information. Furthermore, a wide variety of participants can play a role as monitors in the horizontal structure of governance system, which also assures credibility and reliability on electronic government through trust on block chain itself. Electronic government aims at virtue of expanded electronic democracy which strengthens information democracy. Also, establishment of electronic governance, that emphasizes networking and guarantees, is a desirable image of the future of the fourth industrial revolution. Therefore, the establishment of future electronic government according to the four principles drawn from this paper can be the most suitable model.

• Convergence Security Journal
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• v.18 no.1
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• pp.19-31
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• 2018

As the ICT technologies advance, the unprecedently large amount of digital data is created, transferred, stored, and utilized in every industry. With the data scale extension and the applying technologies advancement, the new services emerging from the use of large scale data make our living more convenient and useful. But the cybercrimes such as data forgery and/or change of data generation time are also increasing. For the data security against the cybercrimes, the technology for data integrity and the time verification are necessary. Today, public key based signature technology is the most commonly used. But a lot of costly system resources and the additional infra to manage the certificates and keys for using it make it impractical to use in the large-scale data environment. In this research, a new and far less system resources consuming signature technology for large scale data, based on the Hash Function and Merkle tree, is introduced. An improved method for processing the distributed hash trees is also suggested to mitigate the disruptions by server failures. The prototype system was implemented, and its performance was evaluated. The results show that the technology can be effectively used in a variety of areas like cloud computing, IoT, big data, fin-tech, etc., which produce a large-scale data.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.122-130
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• 2013

This work proposes a 12b 100MS/s 45nm CMOS four-step pipeline ADC for high-speed digital communication systems requiring high resolution, low power, and small size. The input SHA employs a gate-bootstrapping circuit to sample wide-band input signals with an accuracy of 12 bits or more. The input SHA and MDACs adopt two-stage op-amps with a gain-boosting technique to achieve the required DC gain and high signal swing range. In addition, cascode and Miller frequency-compensation techniques are selectively used for wide bandwidth and stable signal settling. The cascode current mirror minimizes current mismatch by channel length modulation and supply variation. The finger width of current mirrors and amplifiers is laid out in the same size to reduce device mismatch. The proposed supply- and temperature-insensitive current and voltage references are implemented on chip with optional off-chip reference voltages for various system applications. The prototype ADC in a 45nm CMOS demonstrates the measured DNL and INL within 0.88LSB and 1.46LSB, respectively. The ADC shows a maximum SNDR of 61.0dB and a maximum SFDR of 74.9dB at 100MS/s, respectively. The ADC with an active die area of $0.43mm^2$ consumes 29.8mW at 100MS/s and a 1.1V supply.

• Progress in Medical Physics
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• v.19 no.1
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• pp.63-72
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• 2008

With recent advancement of the medical imaging systems and picture archiving and communication system (PACS), installation of digital radiography has been accelerated over past few years. Moreover, Computed Radiography (CR) which was well established for the foundation of digital x-ray imaging systems at low cost was widely used for clinical applications. This study analyzes imaging characteristics for two systems with different pixel sizes through the Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE). In addition, influence of radiation dose to the imaging characteristics was also measured by quantitative assessment. A standard beam quality RQA5 based on an international electro-technical commission (IEC) standard was used to perform the x-ray imaging studies. For the results, the spatial resolution based on MTF at 10% for Agfa CR system with I.P size of $8{\times}10$ inches and $14{\times}17$ inches was measured as 3.9 cycles/mm and 2.8 cycles/mm, respectively. The spatial resolution based on MTF at 10% for Fuji CR system with I.P size of $8{\times}10$ inches and $14{\times}17$ inches was measured as 3.4 cycles/mm and 3.2 cycles/mm, respectively. There was difference in the spatial resolution for $14{\times}17$ inches, although radiation dose does not effect to the MTF. The NPS of the Agfa CR system shows similar results for different pixel size between $100{\mu}m$ for $8{\times}10$ inch I.P and $150{\mu}m$ for $14{\times}17$ inch I.P. For both systems, the results show better NPS for increased radiation dose due to increasing number of photons. DQE of the Agfa CR system for $8{\times}10$ inch I.P and $14{\times}17$ inch I.P resulted in 11% and 8.8% at 1.5 cycles/mm, respectively. Both systems show that the higher level of radiation dose would lead to the worse DQE efficiency. Measuring DQE for multiple factors of imaging characteristics plays very important role in determining efficiency of equipment and reducing radiation dose for the patients. In conclusion, the results of this study could be used as a baseline to optimize imaging systems and their imaging characteristics by measuring MTF, NPS, and DQE for different level of radiation dose.