• Journal of Aerospace System Engineering
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• v.13 no.5
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• pp.87-93
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• 2019

This study suggests the development of the ALE (Automatic Link Establishment) system for the long-range communication with a helicopter at the lands or marines by HF (High Frequency) radios. In the condition of LOS or more than 35 NM, the communication success rate is significantly lowered when the frequency is manually selected because of the reduced transmission power and various strong RF environment noise signals. In this paper, we make an effort to overcome the difficulties of choosing the optimal frequency when the operating frequency selection is manually operated in long-distance communication or LOS uncertain environment. The ALE system is designed based on the frequency analysis propagation software and is verified that the communication success rate is increased by applying the proposed system. The ALE system was applied to the helicopter system and the ground/flight test was conducted. As a result, the superiority and efficiency of the proposed system were verified.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.468-479
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• 2016

In order to supply power to online monitoring systems that are attached to high voltage catenary or overhead wires, a wireless power transfer system is required that is able to transmit power over the insulation gap. Such wireless power transfer systems have transmitter and receiver coils that have diameters of over 10cm. This paper focused on an investigation of the sources of loss in the coils when the coils are fabricated using printed circuit board technology. Using finite element simulation results, it has been shown that the dielectric loss in the substrate was the dominant source of the total loss. It has been demonstrated that the selection of a proper dielectric material was the most critical factor in reducing the loss. For further reduction of the loss, the distributed tuning capacitor method and the slotting of the inter-turn spaces have been proposed. For the evaluation of the proposed methods, four coils have been fabricated and their equivalent series resistances and quality factors were measured. Measured quality factors were greater than 300, which means that these devices will be helpful in achieving high coil-to-coil efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.10
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• pp.3815-3833
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• 2021

MILP-based automatic search is the most common method in analyzing the security of cryptographic algorithms. However, this method brings many issues such as low efficiency due to the large size of the model, and the difficulty in finding the contradiction of the impossible differential distinguisher. To analyze the security of ESF algorithm, this paper introduces a simplified MILP-based search model of the differential distinguisher by reducing constrains of XOR and S-box operations, and variables by combining cyclic shift with its adjacent operations. Also, a new method to find contradictions of the impossible differential distinguisher is proposed by introducing temporary variables, which can avoid wrong and miss selection of contradictions. Based on a 9-round impossible differential distinguisher, 15-round attack of ESF can be achieved by extending forward and backward 3-round in single-key setting. Compared with existing results, the exact lower bound of differential active S-boxes in single-key setting for 10-round ESF are improved. Also, 2108 9-round impossible differential distinguishers in single-key setting and 14 12-round impossible differential distinguishers in related-key setting are obtained. Especially, the round of the discovered impossible differential distinguisher in related-key setting is the highest, and compared with the previous results, this attack achieves the highest round number in single-key setting.

• Journal of the Korea Fashion and Costume Design Association
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• v.20 no.4
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• pp.105-115
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• 2018

This paper presents an investigation into Cheollik based on 288 records about it at the homepage of The Annals of the Joseon Dynasty on the Internet. Cheollik was called in diverse names and worn by various social classes from kings to common people, but it was solidified as clothes for military officers toward the latter half of Joseon. Not only did it serve the purpose of clothes, but it also was used for a royal grant, diplomacy, shrouding a corpse, and royal coffin. It served the diplomatic purposes a lot especially during the reign of King Sejo and King Seongjong. Cheollik was usually made of cotton, hemp, silk, and mixed fabric with silk used most. Its major colors include white, green, red, blue, black, purple, grey, and yellow with white used most. The fabrics and colors of Cheollik became simplified toward the latter half of Joseon. Silk was most used in Cheollik for a royal grant, shrouding a corpse, and royal coffin. White was most used in Cheollik for kings' visit to royal tombs or their participation in ancestral rites. There were limitations with the selection of materials according to the social status and situations. It was stipulated that only Sa and Ju were used to make Cheollik for Dangsangguan and Danghaguan. Cheollik made of silk was banned for country residents and merchants. The color of Cheollik for Danghaguan was changed to blue and then red. Of military officers, only those who had a Gonsu title or higher were allowed to wear Cheollik made of silk in various colors. In the end, Cheollik was abolished for its low convenience and efficiency during the rule of King Gojong.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.729-738
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• 2019

In this paper, we propose two-way authentication protocol between unmanned systems in tactical wireless networks in which long distance communications are not guaranteed due to a poor channel conditions. It is assumed that every unmanned systems have same random data set before they put into combat. The proposed protocol generates authentication code(AC) using random data that causes hash collision. The requester for authentication encrypts the materials such as their identifier, time-stamp, authentication code with the secret key. After then the requester transmits the encrypted message to the receiver. The receiver authenticates the requester by verifying the authentication code included in the request message. The performance analysis of the proposed protocol shows that it guarantees the security for various attack scenarios and efficiency in terms of communication overhead and computational cost. Furthermore, we analyzed the effect of the parameter values of the proposed protocol on the performance and suggest appropriate parameter value selection guide according to the level of security requirement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2277-2298
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• 2019

Adaptive learning in e-learning has garnered researchers' interest. In it, learning resources could be recommended automatically to achieve a personalized learning experience. There are various ways to realize it. One of the realistic ways is adaptive learning path recommendation, in which learning resources are provided according to learners' requirements. This paper summarizes existing works and proposes an innovative approach. Firstly, a learner-centred concept map is created using graph theory based on the features of the learners and concepts. Then, the approach generates a linear concept sequence from the concept map using the proposed traversal algorithm. Finally, Learning Objects (LOs), which are the smallest concrete units that make up a learning path, are organized based on the concept sequences. In order to realize this step, we model it as a multi-objective combinatorial optimization problem, and an improved immune algorithm (IIA) is proposed to solve it. In the experimental stage, a series of simulated experiments are conducted on nine datasets with different levels of complexity. The results show that the proposed algorithm increases the computational efficiency and effectiveness. Moreover, an empirical study is carried out to validate the proposed approach from a pedagogical view. Compared with a self-selection based approach and the other evolutionary algorithm based approaches, the proposed approach produces better outcomes in terms of learners' homework, final exam grades and satisfaction.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.1
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• pp.79-86
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• 2019

In order to measure the filtration characteristics of a cotton ball shape filter, the experiments of suspended solids(SS) surrogate material selection and filtration performance have been carried out in this study. Between the two materials of powdered activated carbon(PAC) and powdered red-clay, PAC is more suitable surrogate material in terms of experimental criteria and particle size distribution in the non-point source pollutants removal system. As a result of the filtration experiments with the cotton ball shape filter, the initial headloss was about 8 cm, and the headloss slightly increased over filtration time. The Kozeny-Carman equation was used to analyze the changes of pressure and porosity during the filtration. The initial porosity was calculated as 0.945 and it decreased to 0.936 at the end of design filtration time. As the filtration continued, the SS concentration of the filtered water gradually increased and the SS removal rate gradually decreased. When the SS target removal efficiency is assumed to be 80%, the cumulative SS removal capacity is expected as $28.8kg/m^2$. This means the volume loading rate of the cotton ball shape filter can be $115m^3/m^2$ when the typical SS concentration of non-point source water pollution is assumed as 250 mg/L.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.430-446
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• 2018

In this paper, we conducted a comparative study on the methodology for impact analysis as the economic grounds for formulating policy and investment plan concerned with utilizing spectrum resource. In order to provide numerical results for objective comparison and selection among policy and investment planning, methods to be analyzed are focused on quantitative methodology based on mathematical models, consequently the utility and limits of econometric model, input-output analysis, computable general equilibrium and system dynamics are compared from various viewpoints including analysis cost. Besides, we compared the methodologies in the standpoint of utilizing spectrum and discussed the recent findings of mixed models combining multiple methodologies to exploit the advantages of each methodology and to offset the limit. Results of the research can be used as reference indicators to select the method that conforms to the purpose and priority of analysis verifying the efficiency of execution of policies and investment plans.

• Journal of Embryo Transfer
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• v.33 no.4
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• pp.245-254
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• 2018

Pigs are considered as optimal donor animal for the successful xenotransplantation. To increase the possibility of clinical application, genetic modification to increase compatibility with human is an important and essential process. Genetic modification technique has been developed and improved to produce genetically modified pigs rapidly. CRISPR/Cas9 system is widely used in various fields including the production of transgenic animals and also can be enable multiple gene modifications. In this study, we developed new gene targeting vector and enrichment system for the rapid and efficient selection of genetically modified cells. We conducted co-transfection with two targeting vectors for simultaneous inactivation of two genes and enrichment of the genetically modified cells using MACS. After this efficient enrichment, genotypic analysis of each colony showed that colonies which have genetic modifications on both genes were confirmed with high efficiency. Somatic cell nuclear transfer was conducted with established donor cells and genetically modified pigs were successfully produced. Genotypic and phenotypic analysis of generated pigs showed identical genotypes with donor cells and no surface expression of ${\alpha}$-Gal and HD antigens. Furthermore, functional analysis using pooled human serum revealed dramatically reduction of human natural antibody (IgG and IgM) binding level and natural antibody-mediated cytotoxicity. In conclusion, the constructed vector and enrichment system using MACS used in this study is efficient and useful to generate genetically modified donor cells with multiple genetic alterations and lead to an efficient production of genetically modified pigs.

• Journal of Practical Engineering Education
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• v.11 no.1
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• pp.117-123
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• 2019

The aim of this study was to investigate the priority partner countries for technical vocational education and training (TVET), using the cluster analysis. The partner countries were prioritized for finance supports and knowledge sharing. We had also redesigned the TVET assistance process as well as reflected the needs of recipient countries for TVET. Especially, by redesigning the methodological support process, we also increased the effectiveness and efficiency of TVET official development assistance. In research method, potential 24 priority partner countries have been designated by the international development cooperation committee and selection criteria of international cooperation agencies and banks. Then, we conducted the cluster analysis, using three main variables: economic factor, labor market factor, education factor. In results, we clustered four and three types of the priority partner countries for TVET. In future, we suggested the new approach for selecting the priority partner countries in terms of employment and labor as well as non-designated partner countries, which will need to cooperate for TVET.