• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.808-820
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• 2014

In this paper, we fabricated two on-wafer type DUT(Device-Under-Test)s; a 10-dB attenuator and an amplifier using commercially available MMIC and we proposed the measurement method of the noise parameters for the two fabricated DUTs. Since the 10-dB attenuator DUT is a passive device, its noise parameters can be accurately determined when its S-parameters are measured. In the case of the amplifier DUT, its noise parameters are available in the datasheet. Hence, the measured noise parameters using the proposed method can be assessed by comparing with the known noise parameters. The noise parameter measurement method having been presented by the authors requires the S-parameters of the 8-port network used in the measurement and limited to coaxial type DUTs. When on-wafer probes are included in the 8-port network, the 8-port S-parameters requires the measurements with different kinds of connectors. In this paper, we obtained the 8-port S-parameters using the Smart-Cal function in the network analyzer. The measured noise parameters shows about ${\pm}0.2dB$ fluctuations for $NF_{min}$. Other noise parameters with the frequency change show good agreement with the expected results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2261-2269
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• 2017

The current LTE network system provides service by locally allocating eNodeB to the EPC(Evolved Packet Core). However, it is not suitable for inter-node communication based on the distributed network environment. In this paper, we propose an integrated system by configuring E-UTRAN and EPC as All-In-One type to enable service in each distributed node. M2M UE is mounted on a each node for wireless In-band backhaul link. The integrated node provides inter-node communication over the wireless in-band backhaul link. If a normal UE moves and an access node changes in the system all entities of LTE integrated into one, it is necessary to change the P-GW which is IP anchor. In order to support the inter-node mobility even if P-GW is changed, We defined UPFE(User Packet Forwarding Extension) scheme and implemented the handover procedure of EPC. Also, we analyze the cell range of the integrated LTE system with the addition of the node and compare the handover delay with the current system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.1-8
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• 2020

The Ministry of Land, Infrastructure and Transport of Korea has been trying to spread integrated railway communication network technologies based on a major railway policy since 2012. As a result, the world's first commercial Long-Term Evolution - Railway (LTE-R) network was established on the Gangneung line (Manjong station - Gangneung station) and has been commercially operating as a railway communication system since 2017. Special function and performance requirements are needed for safe and efficient railway operations, such as group calls, emergency calls, functional addressing, and train control based on wireless communications. In this paper, we present functional and performance railway communications requirements that are based on European wireless railway communications systems. In addition, we measured communications characteristics and performance using a KTX field test on the Gangneung line to analyze the validity and reliability of the LTE-R network. Although the average Radio Frequency (RF) conditions were satisfied in the requirements, we found sudden communications quality degradation, such as Radio Link Failure (RLF) in some railway sections. We propose a way to improve performance and network installations based on in-depth analysis of LTE-R communications field-test results.

• Archives of design research
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• v.12 no.4
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• pp.61-68
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• 1999

Most of the time, developers spend their energy to analyze the main function of the system or make source codes. As a result, they can not consider user interface on their own system and this is true in most programmer's world. But we want to consider the design concept in developing mechanism. In this case we have to upgrade the legacy system which maintaining the transmission system using the copper cables, and add the transmission system using the optical fiber cables. Therefore we design the user interface make easy for end users who are using the maintaining system on copper cables not to confuse the new system which include optical fibers. Especially, we are consider the developing model of design policy and real user to make easy to use new system. In this paper we will describe the instance to adapt the design concept on Broadband Access Network Operation Support System.

• Management & Information Systems Review
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• v.38 no.3
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• pp.55-80
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• 2019

Recently, many companies improving their management performance by building a powerful brand value which is recognized for trademark rights. However, as growing up the size of online commerce market, the infringement of trademark rights is increasing. According to various studies and reports, cases of foreign and domestic companies infringing on their trademark rights are increased. As the manpower and the cost required for the protection of trademark are enormous, small and medium enterprises(SMEs) could not conduct preliminary investigations to protect their trademark rights. Besides, due to the trademark image search service does not exist, many domestic companies have a problem that investigating huge amounts of trademarks manually when conducting preliminary investigations to protect their rights of trademark. Therefore, we develop an intelligent similar trademark search model to reduce the manpower and cost for preliminary investigation. To measure the performance of the model which is developed in this study, test data selected by intellectual property experts was used, and the performance of ResNet V1 101 was the highest. The significance of this study is as follows. The experimental results empirically demonstrate that the image classification algorithm shows high performance not only object recognition but also image retrieval. Since the model that developed in this study was learned through actual trademark image data, it is expected that it can be applied in the real industrial environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1115-1123
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• 2000

Most of the existing web caches are used in huge organizations. But many internet users belong to small organizations such as a venture company or a PC room. Users are in general in multiple window environments, and use several programs concurrently with rapid preference change within a relatively short period of time. We develop a network-path based algorithm. It organizes a cache according to the network paths of the requested URLs and builds a network cache farm where caches are logically connected with each other and each cache has its own preference over certain network paths. The algorithm has been implemented and tested in a real site. The performance results show that the new algorithm outperforms the existing algorithms in the hit ratio and response time dramatically with low cost.

• The KIPS Transactions:PartC
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• v.10C no.2
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• pp.241-252
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• 2003

IMT-2000 appeared in order to satisfy the desires of the uses who wish to supply through wireless most of the services being provided through wire, such as Internet services and multimedia high-speed data information. However, during global roaming, the signal data and the user data get transmitted through the networks of other users. Also, it is judged that with the provision of high speed data communication the amount of data communication necessary for confidentiality protection will increase. It is planned that the recent IMT-2000 Project will begin its commercial service in 2002. From this viewpoint, wireless contents, due to their special characteristics, are greatly exposed to illegal actions by third persons. As a result, it can be said that security and certification issues in the mobile telecommunication environment are indispensable matters. For this purpose, it is intended that in this thesis through an analysis of the existent IMT-2000 certification method, a more safe and efficient authentication method is presented and, at the same time, a security protocol necessary in the provision of wireless contents is designed.

• Journal of Korea Multimedia Society
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• v.11 no.2
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• pp.214-227
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• 2008

As cellular network technologies continue to evolve, various network standards coexist in most CDMA-based cellular networks. This means that mobile device users access mobile services over different network bandwidths according to the users' positions or the mobile devices' network access capabilities. Such differences of network bandwidths cause big differences in service response times. To address this problem, we present a framework called CANS (Context-Aware framework for mobile Navigation Services), which takes into account the user's network profile to adapt the contents for CDRG(Centrally Determined Route Guidance) navigation services for cellular phones. To the best of the authors' knowledge, CANS is the first context-aware framework to make mobile navigation services more feasible. The experimental results under commercial CDMA network show that CANS is able to provide similar service response times regardless of type of wireless network to which users connect by adapting the contents to network bandwidths.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.201-208
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• 2016

Recently, extensive research on crack analysis using extended finite element method(XFEM) which has main advantages in element re-meshing and visualization of cracks has been conducted. However, its application was restricted to the members of a single material. In this study, the applicability and feasibility of the XFEM to the multiple crack analysis of reinforced concrete beams were demonstrated. ABAQUS which has implemented XFEM was used for the crack analysis and its results were compared with test results. Enriched degree-of-freedom locking phenomenon was discovered and its causes and the ways to prevent it were suggested. The locking occurs when cracks in the adjacent elements simultaneously develop. A modelling technique for multiple cracking similar to test results was also proposed. The analysis with XFEM showed similar results to the tests in terms of crack patterns, spacing of cracks, and load-deflection relationship.

• The Korean Journal of Nuclear Medicine
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• v.22 no.2
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• pp.157-161
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• 1988

Cerebral rete mirabile는 잘 알려진 뇌혈관 질환으로 뇌혈관촬영상 내경동맥이 심한 협착 혹은 폐색, 뇌저부의 이상혈관망 형성 및 다수의 연수막동맥간문합과 경경수막 외내경동맥간문합의 특징적 소견을 나타낸다. 최근 방사성의약품의 발전과 함께, Tc-99m-HMPAO를 이용한 뇌SPECT는 뇌혈류역학의 평가, 병소의 조기발견 및 병소의 정확한 위치를 알기위한 상용진단 방법이 되었다. 저자들은 뇌 혈관촬영으로 확진된 10명 의 Cerebral rete mirabile 환자에서 뇌 전산화단층촬영과 Tc-99m-HMPAO를 이용한 국소뇌혈류 SPECT를 검토하였다. 대상환자중 남자는 3명, 여자는 7명이었으며, 연령분포는 6세에서 38세이었다. 1) Tc-99m-HMPAO를 이응한 국소 뇌혈류 SPECT는 뇌의 경색부위 뿐만 아니라 허혈부위까지 나타냈으며, cerebral rete mirabile에서의 뇌의 침습된 부위를 나타내는데 있어서 뇌전산화단층촬영보다 우월하였다. 또한 모든 예에서 뇌전산화반층촬영보다 더 넓은 허혈부위를 보여주었다. 2) 다른 허혈성 뇌혈관질환과 비교하여 cerebral rete mirabile는 비균질성 방사능을 나타냈고, 이는 측부순환로에 의한 것으로 추측된다. 3) Tc-99m-HMPAO를 이용한 국소뇌혈류 SPECT는 뇌의 허혈부위의 범위를 평가, 문합수술의 계획 및 cerebral rete mirabile의 경과를 추적하는데 유용한 검사이다.