• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.179-185
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• 2019

In this paper, we have studied narrow-band analog pre-distortion linearization technique using UHF 400 MHz band 20 W power amplifier. The analog pre-distorter used the SC1894 radio frequency power amplifier linearizer(RFPAL) provided by MAXIM Corp and through the look-up table technique confirmed the intermodulation distortion(IMD) performance and the adjusted channel leakage ratio(ACLR) improvement for bandwidth below 1 MHz which does not operate on existing chips. In the 400 MHz (400 ~ 500 MHz) band, IMD performance and the ACLR improvement of up to 17.46 dB based on 1-channel offset and up to 16.6 dB based on 2-channel offset were confirmed. In the system requiring the same linearity, we confirmed power efficiency improvement of 12.41% at output power of over 40 W.

• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.9-16
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• 2021

Due to the prolonged infectious disease of COVID-19 worldwide, there are various security threats due to network attacks on Internet of Things devices that are vulnerable to telecommuting. Initially, users of Internet of Things devices were exploited for vulnerabilities in Remote Desktop Protocol, spear phishing and APT attacks. Since then, the technology of network attacks has gradually evolved, exploiting the simple service discovery protocol of Internet of Things devices, and DRDoS attacks have continued to increase. Existing SSDPs are accessible to unauthorized devices on the network, resulting in problems with information disclosure and amplification attacks on SSDP servers. To compensate for the problem with the authentication procedure of existing SSDPs, we propose a hash-based SSDP that encrypts server-specific information with hash and adds authentication fields to both Notify and M-Search message packets to determine whether an authorized IoT device is present.

• Journal of the Korea Convergence Society
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• v.12 no.4
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• pp.51-60
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• 2021

Recent advances in network and hardware technologies have led to active research and multiple network technologies that fuse blockchain technologies with security. We propose a system model that analyzes technologies using existing blockchain and verifies the integrity of files using private blockchain in a limited environment. The proposed model can be written as a chain code of Hyperleisure Fabric, a private blockchain platform, and verified for integrity of files through Hyperleisure Explorer, a private blockchain integrated management platform. The system performance of the proposed model was analyzed from a developer perspective and from a user perspective. As a result of the analysis, there are compatibility problems according to the version of various modules to run the blockchain platform, and only limited elements such as chain code status and groups can be checked.

• Journal of Convergence for Information Technology
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• v.10 no.12
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• pp.22-30
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• 2020

With the development of information and communication technology, DDoS and DRDoS continue to become security issues, and gradually develop into advanced techniques. Recently, IT companies have been threatened with DRDoS technology, which uses protocols from normal servers to exploit as reflective servers. Reflective traffic is traffic from normal servers, making it difficult to distinguish from security equipment and amplified to a maximum of Tbps in real-life cases. In this paper, after comparing and analyzing the DNS amplification and Memcached amplification used in DRDoS attacks, a countermeasure that can reduce the effectiveness of the attack is proposed. Protocols used as reflective traffic include TCP and UDP, and NTP, DNS, and Memcached. Comparing and analyzing DNS protocols and Memcached protocols with higher response sizes of reflective traffic among the protocols used as reflective traffic, Memcached protocols amplify ±21% more than DNS protocols. The countermeasure can reduce the effectiveness of an attack by using the Memcached Protocol's memory initialization command. In future studies, various security-prone servers can be shared over security networks to predict the fundamental blocking effect.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.29 no.1
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• pp.38-49
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• 2011

This study is foundation study to understand the Location and the composition of Joseon Royal Tombs, the purpose is to bring light on the types of Sinro Eoro in Joseon Royal Tombs. The type was grouped into Regular type and Irregular type by relations with the approach way, Hongsalmun and Jeongjagak, and the Irregular type was grouped into Curved type and Divided type. The making pattern of Sinro Eoro was divided into three period, the former period, the transition period and the latter period, by the length and the Irregular type. The Regular type was affected by the length of Geonwonreung's Sinro Eoro as the minimum standard in the former period. The result of examining the Irregular type's present condition in Jeongreung, Hyeonreung, Mokreung, Jangreung and Yeongreung, narrow topograph and the waterway were important factors to decide the type. In other words, the type of Irregular Sinro Eoro was constructed by a topography and a waterway in the length of Geonwonreung's Sinro Eoro as the minimum standard.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.1
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• pp.67-71
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• 2021

In this study, graphene layer was grown on metal microwire using chemical vapor deposition. The difference of carbon solubility between copper and nickel resulted in the formation of mono-layer and multi-layer graphene were formed on the surfaces of copper and nickel microwires, respectively. During the growth of graphene at high temperature, copper and nickel were recrytallized and the grain size increased. The ampacity of graphene/copper microwire was improved by approximately 27%, 1.91×105 A/㎠, compared to pristine copper microwire. Similar to this behavior, the ampacity of multilayer graphene/nickel microwire was 4.41×104 A/㎠ which is about about 36% improved compared to the pure nickel microwire. The excellent electrical properties of graphene/metal composites are beneficial for supplying the electrical energy to the high-power electronic devices and equipment.

• KIPS Transactions on Computer and Communication Systems
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• v.12 no.8
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• pp.243-252
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• 2023

Satellite imageries are at a greatest importance for land cover examining. Numerous studies have been conducted with satellite images and uses semantic segmentation techniques to extract information which has higher altitude viewpoint. The device which is taking these images must employee wireless communication links to send them to receiving ground stations. Wireless communications from a satellite are inevitably affected due to transmission errors. Evidently images which are being transmitted are distorted because of the information loss. Current semantic segmentation techniques are not made for segmenting distorted images. Traditional image enhancement methods have their own limitations when they are used for satellite images enhancement. This paper proposes an auto-encoder based image pre-enhancing method for satellite images. As a distorted satellite images dataset, images received from a real radio transmitter were used. Training process of the proposed auto-encoder was done by letting it learn to produce a proper approximation of the source image which was sent by the image transmitter. Unlike traditional image enhancing methods, the proposed method was able to provide more applicable image to a segmentation model. Results showed that by using the proposed pre-enhancing technique, segmentation results have been greatly improved. Enhancements made to the aerial images are contributed the correct assessment of land resources.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.3
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• pp.99-104
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• 2022

Convolutional neural network (CNN) generally uses two-stream architecture RGB and optical flow stream for its action recognition function. RGB frames stream display appearance and optical flow stream interprets its action. However, the standard method of using optical flow is costly in its computational time and latency associated with increased action recognition. The purpose of the study was to evaluate a novel way to create a two sub-networks in neural networks. The optical flow sub-network was assigned as a teacher and the RGB frames as a student. In the training stage, the optical flow sub-network extracts features through the teacher sub-network and transmits the information to student sub-network for baseline training. In the test stage, only student sub-network was operational with decreased in latency without computing optical flow. Experimental results shows that our network fed only by RGB stream gets a competitive accuracy of 54.5% on HMDB51, which is 1.5 times better than that on R3D-18.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.108-110
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• 2021

Since 2015, attacks using the IoT protocol have been continuously reported. Among various IoT protocols, attackers attempt DDoS attacks using SSDP(Simple Service Discovery Protocol), and as statistics of cyber shelters, Korea has about 1 million open SSDP servers. Vulnerable SSDP servers connected to the Internet can generate more than 50Gb of traffic and the risk of attack increases gradually. Until recently, distributed denial of service attacks and distributed reflective denial of service attacks have been a security issue. Accordingly, the purpose of this study is to analyze the request packet of the existing SSDP protocol to identify an amplification attack and to avoid a response when an amplification attack is suspected, thereby preventing network load due to the occurrence of a large number of response packets due to the role of traffic reflection amplification.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.105-107
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• 2021

With the prolonged COVID-19 worldwide, it is essential to create a list of visitors when using various facilities to prevent the spread of COVID-19 and to investigate epidemiology in the event of confirmed cases. In the beginning, there were many problems due to the leakage of personal information and false preparation by making a list of visitors with a handwritten list. To compensate for the problems of handwritten lists, the KI-Pass system based on QR codes is mainly managed. However, KI-Pass systems have the disadvantages of issuing QR codes and abusing personal information. In this paper, we propose an access management system using beacon. Beacon is an close-range wireless communication device and visitors when they are near the facility and automatically registers their personal information on the cloud server for access management. It is expected that this will be effective in preventing and responding to the spread of new infectious diseases in the future.