• Journal of Korea Multimedia Society
• /
• v.7 no.9
• /
• pp.1282-1293
• /
• 2004

This paper proposes an asymmetric watermarking system using Public Key Infrastructure. The distinguishing characteristic of the proposed method connects between the two different techniques, cryptography technique and watermarking technique, by using the authentication technique. The connection between the two techniques are established based on the special qualities of each technique. Watermarks that are inserted into the digital contents consist of a digital signature described as an encrypted copyright information with the private key of a distributor or a copyright holder, and an authentication code. In the situation where the ownership of the digital contents has to be decided, authentication technique examines the data integrity of the digital contents based on an authentication and decides the ownership of the digital contents by examining whether it satisfies or not satisfies the integrity test. The formal case uses decryption method which compares the user defined copyright information, and the decrypted copyright information extracted from the watermark in the digital contents that are decrypted by distributors' public key The latter case determines the ownership by comparing the similarity between encrypted copyright information separated from the watermark that are extracted from the digital contents, and the user defined encrypted copyright information that are separated from the watermark The proposed method provides protection from the assault which attempts to identify or erase the encoding key.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.9
• /
• pp.661-667
• /
• 2018

Tactical communication radio systems that employ software defined radios(SDRs) have been developed for achieving high-speed data transmissions and voice communications. Such systems possess multiband and multichannel features, and can potentially replace several existing radio systems. This paper proposes a design for wideband antennas by incorporating a diplexer matching network for tactical vehicles. The proposed antenna design includes two radiators(upper and lower) and a diplexer matching network connected to the end of the feed line such that the LC matching networks are interleaved in the lower radiator and spring mount. By employing the diplexer matching network, the designed antenna can perform wideband impedance matching for the fifty ohm feed line. The designed LC networks aid in varying the effective electrical length of the antenna according to the operation frequency. The primary objective behind adjusting the electrical length is to vary the current distribution above and below the LC networks. The proposed antenna was fabricated and tested in an open site. The obtained evaluation results show that the designed antenna can achieve a relative bandwidth of 190% with a VSWR value of 3.5:1, and can attain good antenna gains over VHF and UHF bands.

• Journal of the Korea Society for Simulation
• /
• v.16 no.2
• /
• pp.27-35
• /
• 2007

When sensor networks are deployed in open environments, all the sensor nodes are vulnerable to physical threat. An attacker can physically capture a sensor node and obtain the security information including the keys used for data authentication. An attacker can easily inject false reports into the sensor network through the compromised node. False report can lead to not only false alarms but also the depletion of limited energy resource in battery powered sensor networks. To overcome this threat, Fan Ye et al. proposed that statistical on-route filtering scheme(SEF) can do verify the false report during the forwarding process. In this scheme, the choice of a security threshold value is important since it trades off detection power and energy, where security threshold value is the number of message authentication code for verification of false report. In this paper, we propose a fuzzy rule-based system for security threshold determination that can conserve energy, while it provides sufficient detection power in the SEF based sensor networks. The fuzzy logic determines a security threshold by considering the probability of a node having non-compromised keys, the number of compromised partitions, and the remaining energy of nodes. The fuzzy based threshold value can conserve energy, while it provides sufficient detection power.

• Journal of radiological science and technology
• /
• v.40 no.4
• /
• pp.533-542
• /
• 2017

In diagnostic radiology, the imaging system has been changed from film/screen to digital system. However, the method for removing scatter radiation such as anti-scatter grid has not kept pace with this change. Therefore, authors have devised the indirect flat panel detector (FPD) system with net-like lead in substrate layer which can remove the scattered radiation. In clinical context, there are many radiographic examinations with angulated incident X-ray. However, our proposed FPD has net-like lead foil so the vertical lead foil to the angulate incident X-ray would have bad effect on its performance. In this study, we identified the effect of vertical/horizontal lead foil component on the novel system's performance and improved the structure of novel system for clinical usage with angulated incident X-ray. Grid exposure factor and image contrast were calculated to investigate various structure of novel system using Monte Carlo simulation software when the incident X-ray was tilted ($0^{\circ}$, $15^{\circ}$, and $30^{\circ}$ from the detector plane). More photons were needed to obtain same image quality in the novel system with vertical lead foil only then the system with horizontal lead foil only. An optimal structure of novel system having different heights of its vertical and horizontal lead foil component showed improved performance compared with the novel system in a previous study. Therefore, the novel system will be useful in a clinical context with the angulated incident X-ray if the height and direction of lead foil in the substrate layer are optimized as the condition of conventional radiography.

• KIPS Transactions on Software and Data Engineering
• /
• v.8 no.11
• /
• pp.441-448
• /
• 2019

Previous researches on automatic spacing of Korean sentences has been researched to correct spacing errors by using n-gram based statistical techniques or morpheme analyzer to insert blanks in the word boundary. In this paper, we propose an end-to-end automatic word spacing by using deep neural network. Automatic word spacing problem could be defined as a tag classification problem in unit of syllable other than word. For contextual representation between syllables, Bi-LSTM encodes the dependency relationship between syllables into a fixed-length vector of continuous vector space using forward and backward LSTM cell. In order to conduct automatic word spacing of Korean sentences, after a fixed-length contextual vector by Bi-LSTM is classified into auto-spacing tag(B or I), the blank is inserted in the front of B tag. For tag classification method, we compose three types of classification neural networks. One is feedforward neural network, another is neural network language model and the other is linear-chain CRF. To compare our models, we measure the performance of automatic word spacing depending on the three of classification networks. linear-chain CRF of them used as classification neural network shows better performance than other models. We used KCC150 corpus as a training and testing data.

• Journal of the Korea Convergence Society
• /
• v.12 no.12
• /
• pp.1-18
• /
• 2021

ICT is the main driving force of Korea's economic growth. Korea has the world's best ICT competitiveness, and several policies are being implemented to maintain it. However, for successful policy implementation, it is crucial to understand ICT trends accurately. Therefore, this study analyzes the trends of 18 core technologies in the ICT field. In particular, the degree of scientific development and commercialization by technology are investigated through research paper analysis and patent analysis, respectively. Then, the trends shown by document type are compared based on the two analysis results. As a result, artificial intelligence and virtual reality are at the stage where commercialization is actively taking place after scientific development, and at the same time, since research is being conducted, it is expected to develop continuously. On the other hand, quantum computer and implantable device are in the basic research stage. It is necessary to understand the current research status and determine the direction of future support. The results of the ICT trend analysis conducted in this study can be used as a criterion for determining the future direction of Korean policy.

• Journal of Advanced Navigation Technology
• /
• v.22 no.6
• /
• pp.642-647
• /
• 2018

In this paper, an unequal power divider based on adjusting electrical length of uniform transmission line is presented. This divider consists of three uniform transmission lines and one isolation resistor and have the different port impedances of input and output. The feature of proposed divider can changed the power dividing ratio to adjust only electrical length of uniform transmission lines. To verify the feasibility of proposed power divider, two divider circuits are designed, one is 1:2 power dividing ratio divider with $60{\Omega}$ uniform transmission line and $40{\Omega}$ input port impedances and $45{\Omega}$ output port impedances, the performance data were measured the insertion losses of 1.7 dB/ 5.0 dB, return losses of more than -30 dB and isolation of more than -35 dB. The other is 1:4 power dividing ratio divider with $40{\Omega}$ uniform transmission line and $50{\Omega}$ input port impedances and $75{\Omega}$ output port impedances, the performance data were measured the insertion losses of 1.3 dB/ 6.8 dB, return losses of more than -12 dB and isolation of more than -19 dB. The measured performance data agreed well with the simulated results.

• Journal of the Korean Society for information Management
• /
• v.35 no.4
• /
• pp.37-50
• /
• 2018

The purpose of this study is to analyze the first edition of Brown's Subject Classification and to understand the implications of today's library classification. For this purpose, the first edition of the Subject Classification published in 1906 was analyzed. The analysis results are divided into three main areas. First, SC is divided into eleven main classes and each class is subdivided into enumerated subdivisions from 000 to 999. Second, As a method of synthesizing the classification numbers, there were three methods of synthesis. There was a flexibility to insert a new classification number at the appropriate location when a new topic that does not appear in the main table appeared. Implications for classification studies can be divided into four main categories. First, SC proposed a method of classification number synthesis for composite topics, which is an innovative method that was not available in previous library classification. Second, the subject matter was explained in various aspects through the operation of auxiliary tables supporting the facets. Third, it is possible to easily insert a new topic into the classification system by using the SC that can have a flexible classification system for each library, or to use a short classification number according to the size of the library collection. Fourth, it provided a directory that can be considered as access points for digital materials.

• Journal of the Korean Society of Radiology
• /
• v.17 no.1
• /
• pp.31-36
• /
• 2023

Among imaging and treatment devices for small animals, positron emission tomography(PET) causes a change in spatial resolution within a field of view. This is a phenomenon caused by using a small gantry and a thin and long scintillation pixel, and detectors that measure the interaction depth are being developed and researched to solve this problem. In this study, a detector that measures the interaction depth was designed using several scintillator blocks and light guides with different reflector patterns. The scintillator block composed of 4 × 4 arrays of 3 mm × 3 mm × 5 mm scintillation pixels formed four layers, and a light guide was inserted in each layer to configure the entire detector. In order to check whether the interaction depth was measured, a gamma ray interaction was generated at the center of all scintillation pixels to acquire data and then reconstructed into a flood image. The reflector patterns of the light guides inserted between the layers were all different, so the positions of the scintillation pixels for each layer were formed in different locations. It is considered that even spatial resolution can be achieved over all regions of the field of view if all positions of the scintillation pixels thus formed are separated and used for image reconstruction.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.18 no.2
• /
• pp.28-32
• /
• 2014

Purpose Patient motion during myocardial perfusion SPECT can produce images that show visual artifacts and perfusion defects. This artifacts and defects remain a significant source of unsatisfactory myocardial perfusion SPECT. Motion correction has been developed as a way to correct and detect the patient motion for reducing artifacts and defects, and each motion correction uses different algorithm. We corrected simulated motion patterns with several motion correction methods and compared those images. Materials and Methods Phantom study was performed. The anthropomorphic torso phantom was made with equal counts from patient's body and simulated defect was added in myocardium phantom for to observe the change in defect. Vertical motion was intentionally generated by moving phantom downward in a returning pattern and in a non-returning pattern throughout the acquisition. In addition, Lateral motion was generated by moving phantom upward in a returning pattern and in a non-returning pattern. The simulated motion patterns were detected and corrected similarly to no-motion pattern image and QPS score, after Motion Detection and Correction Method (MDC), stasis, Hopkins method were applied. Results In phantom study, Changes of perfusion defect were shown in the anterior wall by the simulated phantom motions, and inferior wall's defect was found in some situations. The changes derived from motion were corrected by motion correction methods, but Hopkins and Stasis method showed visual artifact, and this visual artifact did not affect to perfusion score. Conclusion It was confirmed that motion correction method is possible to reduce the motion artifact and artifactual perfusion defect, through the apply on the phantom tests. Motion Detection and Correction Method (MDC) performed better than other method with polar map image and perfusion score result.