• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.553-560
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• 2004

In this experiment, a three dimensional structure analysis was carried out to examine the surface defects of semiconductor made artificially on known scale. It was investigated the three dimensional imaging according to the sample depth and the thermal diffusivity as well as the carrier transport properties. The thermal diffusivity measurement of the intrinsic GaAs semiconductor was also analyzed by the difference of frequency-dependence photoacoustic signals from the sample surface of different conditions. Thermal properties such as thermal diffusion length or thermal diffusivity of the Si wafer with and without defects on the surface were obtained by interpreting the frequency dependence of the PA signals. As a result, the photoacoustic signal is found to have the dependency on the shape and depth of the defects so that their structure of the defects can be analyzed. This method demonstrates the possibility of the application to the detection of the defects, cracks, and shortage of circuits on surface or sub-surface of the semiconductors and ceramic materials as a nondestructive testing(NDT) and a nondestructive evaluation(NDE) technique.

• 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.

• Progress in Medical Physics
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• v.25 no.4
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• pp.242-247
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• 2014

To see the discrepancies between the calculated and the delivered dose distribution of IMRT fields for respiratory-induced moving target according to the motion ranges. Four IMRT plans in which there are five fields, for lung and liver patients were selected. The gantry angles were set to $0^{\circ}$ for every field and recalculated using TPS (Eclipse Ver 8.1, Varian Medical Systems, Inc., USA). The ion-chamber array detector (MatriXX, IBA Dosimetry, Germany) was placed on the respiratory simulating platform and made it to move with ranges of 1, 2, and 3 cm, respectively. The IMRT fields were delivered to the detector with 30~70% gating windows. The comparison was performed by gamma index with tolerance of 3 mm and 3%. The average pass rate was 98.63% when there's no motion. When 1.0, 2.0, 3.0 cm motion ranges were simulated, the average pass rate were 98.59%, 97.82%, and 95.84%, respectively. Therefore, ITV margin should be increased or gating windows should be decreased for targets with large motion ranges.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.6
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• pp.149-158
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• 2005

This paper proposed a blind watermarking method for video contents which satisfies both the invisibility and the robustness to attacks to prohibit counterfeiting, modification, illegal usage and illegal re-production of video contents. This watermarking algorithm targets MPEG compression system and was designed to control the amount of watermarking to be inserted according to the adaptive quantization scale code to follow the adaptive quantization of the compression system. The inserting positions of the watermark were chosen by considering the frequency property of an image and horizontal, vertical and diagonal property of a $8{\times}8$ image block. Also the amount of watermarking for each watermark bit was decided by considering the quantization step. This algorithm was implemented by C++ and experimented for invisibility and robustness with MPEG-2 system. The experiment results showed that the method satisfied enough the invisibility of the inserted watermark and robustness against attacks. For the general attacks, the error rate of the extracted watermark was less than $10\%$, which is enough in robustness against the attacks. Therefore, this algorithm is expected to be used effectively as a part in many MPEG systems for real-time watermarking, especially in the sensitive applications to the network environments.

• Convergence Security Journal
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• v.2 no.1
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• pp.87-97
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• 2002

Many firms are utilizing the Internet and various information technologies to effectively manage their business operations with a goal of gaining a competitive advantage in the rapidly changing business environments. Today, the business is characterized as digital economy where information freely flows and business processes are improved with the use of information technologies. Internet technology is playing a key role in transforming the organization and creating new business models. It has become the infrastructure of choice for electronic commerce because it provides process efficiency, cost reduction, and open standards that can easily be adopted by different organizations. Here, the vast amount of data and information slow among the related parties and security issues are very critical matter of research interests by academicians and practitioners. In this research, we address the importance of security framework in managing the data shared among the related parties in the e-business and suggest the security architecture for effectively supporting the needs of e-business in an organization. This research provides valuable contributions both in academics and industry in terms of how security framework and architecture should be set in order to provide the necessary e-business.

• Journal of the Korea Convergence Society
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• v.8 no.9
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• pp.1-7
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• 2017

As the network environment develops and speeds up, a lot of smart devices is developed, and a high-speed smart society can be realized while allowing people to interact with objects. As the number of things Internet has surged, a wide range of new security risks and problems have emerged for devices, platforms and operating systems, communications, and connected systems. Due to the physical characteristics of IoT devices, they are smaller in size than conventional systems, and operate with low power, low cost, and relatively low specifications. Therefore, it is difficult to apply the existing security solution used in the existing system. In addition, IoT devices are connected to the network at all times, it is important to ensure that personal privacy exposure, such as eavesdropping, data tampering, privacy breach, information leakage, unauthorized access, Significant security issues can arise, including confidentiality and threats to facilities. In this paper, we investigate cases of security threats and cases of network of IoT, analyze vulnerabilities, and suggest ways to minimize property damage by Internet of things.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.4
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• pp.779-787
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• 2018

As security problems of the paper ballot have been emerged on and on, electronic voting with enhanced security and convenience has been introduced in several countries. However, it has not been adopted most of countries because of the problems that come from interdependence and security flaws. Meanwhile, the blockchain technology has high reliability due to the mechanism of mining that miners verify and preserve blocks independently by using P2P formation which does not have a central authority. Furthermore, because each block refers to the hash of the previous block. if any one block is changed, it is very difficult to forge and modify the blockchain because all blocks must be changed. If this technology is applied to the E-voting, integrity, and transparency about the result of the ballot is guaranteed. In this paper, we propose and implement an electronic voting system based on blockchain that improves interdependence, the reliability of excessive TTP and single point of failure come from original electronic voting. Also, we analyze the security and advantage of the proposal system compared with the existing bitcoin-based electronic voting system.

• The KIPS Transactions:PartB
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• v.17B no.3
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• pp.197-206
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• 2010

High-quality and low-price digital printing devices are nowadays abused to print or forge official documents and bills. Identifying color laser printers will be a step for media forensics. This paper presents a new method to identify color laser printers with printed color images. Since different printer companies use different manufactural systems, printed documents from different printers have little difference in visual. Analyzing this artifact, we can identify the color laser printers. First, high-frequency components of images are extracted from original images with discrete wavelet transform. After calculating the gray-level co-occurrence matrix of the components, we extract some statistical features. Then, these features are applied to train and classify the support vector machine for identifying the color laser printer. In the experiment, total 2,597 images of 7 printers (HP, Canon, Xerox DCC400, Xerox DCC450, Xerox DCC5560, Xerox DCC6540, Konica), are tested to classify the color laser printer. The results prove that the presented identification method performs well with 96.9% accuracy.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.4
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• pp.731-751
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• 2021

The Internet of Things is a huge group of devices communicating each other and the interconnection of objects in the network is a basic requirement. Choosing a reliable device is critical because malicious devices can compromise networks and services. However, it is difficult to create a trust management model due to the mobility and resource constraints of IoT devices. For the centralized approach, there are issues of single point of failure and resource expansion and for the distributed approach, it allows to expand network without additional equipment by interconnecting each other, but it has limitations in data exchange and storage with limited resources and is difficult to ensure consistency. Recently, trust management models using fog nodes and blockchain have been proposed. However, blockchain has problems of low throughput and delay. Therefore, in this paper, a trust management model for selecting reliable devices in a fog-based IoT environment is proposed by applying IOTA, a blockchain technology for the Internet of Things. In this model, Directed Acyclic Graph-based ledger structure manages trust data without falsification and improves the low throughput and scalability problems of blockchain.

• 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.