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Deep-Fading Hole Avoidance for Secure Region Detection using Channel State Information
Suh, Jihwan,YOO, YONGJAE,Paek, Jeongyeup,박세웅 한국통신학회 2022 Journal of communications and networks Vol.24 No.6
One of the critical challenges in many wirelesssystems is the deep fading hole problem where signals interferedestructively to create an abrupt change in signal amplitude dueto multipath fading. In this work, we tackle this challenge in thecontext of secure region detection (SRD) problem. Specifically, wepropose SHARD, a novel hole avoidance technique that analyzeschannel state information (CSI) to significantly improve theaccuracy of CSI-based SRD. SHARD identifies potential fadingholes in CSI amplitude, and removes an unreliable portion of datawhile utilizing the remaining unaffected part. To compensate forthe loss of information, we define phase-distance for reliable useof time-varying CSI phase, and neighboring reference points areutilized for accurate matching. Our real-world experiments showthat SHARD can achieve a near-perfect 99.96% true-negativeratio (successfully rejecting devices not in the secure region)and an excellent true-positive of 98.01% for practical usage,significantly better than state-of-the-art prior work. We believeour ideas can be generalized to many RF-based localizationsystems to mitigate the deep fading hole problem and improvetheir accuracy.
내열변형 저감을 위한 A-Pillar Trim의 마운트 위치 최적설계
전지환(Jihwan Chun),이정환(Junghwan Lee),김종만(Jongman Kim),류승수(Seungsoo Ryu),김해룡(Haeryong Kim),김헌수(Hunsoo Kim),서명원(Myungwon Suh) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Interior parts composed of plastic usually deform under the various temperature conditions. It is necessary to obtain the material properties for thermal deformation analysis under the heat cycle test. Specially, creep data of plastic material was introduced to study the time-dependent deformation behavior of the pillar trim in heat cycle test. The time-hardening version of the power-law creep model was applied to account for the permanent deformation after heat cycle test, verified through the comparison of test result with FEA result for simple model. In this study, a methodology was developed for the optimum design of the A-pillar trim with mount position. The analyzed results were used to approximate a function which was constructed using response surface method. Design procedures were repeated to minimize the thermal deformation at the areas of interest.
내열변형을 고려한 프런트 필라 트림의 리브패턴 설계에 관한 연구
이정환(Junghwan Lee),전지환(Jihwan Chun),김종만(Jongman Kim),김영삼(Youngsam Kim),류승수(Seungsoo Ryu),김해룡(Haeryong Kim),서명원(Myungwon Suh) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In the development period of interior plastic parts of vehicle, the heat cycle test is an essential procedure to be confirmed. It is important to obtain the material properties for thermal deformation analysis under the various temperature conditions. Especially, creep data of plastic material was introduced to study the time-dependent deformation behavior of the pillar trim in heat cycle test. The time-hardening version of the power-law creep model was applied to account for the permanent deformation after heat cycle test, verified through the comparison of test result with FEA result for simple model. In this study, we also developed a methodology to design the rib pattern of A-pillar trim. Nonlinear finite element analysis has been implemented and integrated with sensitivity analysis method to minimize the thermal deformation at the areas of interest.
FMS-AMS: Secure Proximity-based Authentication for Wireless Access in Internet of Things
Jeongyoon Heo,Yongjae Yoo,Jihwan Suh,Woojin Park,Jeongyeup Paek,Saewoong Bahk 한국통신학회 2020 Journal of communications and networks Vol.22 No.4
Proximity-based authentication enables wireless accesspoints (AP) to allow connection only to devices within a certain authentication range. This would be very convenient for allowing network access only to those within a physical boundary. However, anattacker not within the authentication range may deceive the APinto authenticating its proximity by eavesdropping with higher receiver gain and increasing its transmit power. This can be doneeasily using an amplifier or a directional antenna. To address thischallenge, we propose ‘Fixed MCS SNR (FMS)’ filtering schemebased on the intuition that high MCS requires high SNR, and amplifying the received signal strength does not necessarily improveSNR. We experimentally show that this is true in reality, and ourreal-world evaluation in various environments (14 locations) showsthat FMS scheme prevents ‘amplifier attacks’ in all cases. To further counter the false positives of FMS against ‘directional antennaattacks’ (avg. 35.7%), we also propose ‘Authentication Motionwith Signal strength gap (AMS)’ filtering scheme which defendsagainst both attacks in all cases at the cost of requiring the user tomake a simple motion. FMS or AMS scheme can be selected according to the application requirement to enhance the security ofproximity-based authentication in upcoming IoT.
Kim, Minjin,Kim, Jihwan,Lee, In-Ho,Han, Woo Hyun,Park, Yun Chang,Kim, Woo Youn,Kim, Bongsoo,Suh, Junho Royal Society of Chemistry 2019 Nanoscale Vol.11 No.12
<P>We report a ternary silver chalcogenide, Ag2Se0.5Te0.5, as a new topological material with improved quantum transport properties. Single-crystalline nanostructures of ternary silver chalcogenides Ag2SexTe1−x are synthesized with a tunable chemical composition <I>via</I> the chemical vapor transport method. Quantum transport studies reveal that Ag2Se0.5Te0.5 nanowires present topological surface states with higher electron mobility and longer mean free path compared to binary Ag-chalcogenides. First-principles calculations also indicate that Ag2Se0.5Te0.5 is a topological insulator, and the observed enhancement in transport properties could imply reduced bulk carrier contribution in the new ternary silver chalcogenide.</P>
Fabrication and characterization of superconducting coplanar waveguide resonators
Kim, Bongkeon,Jung, Minkyung,Kim, Jihwan,Suh, Junho,Doh, Yong-Joo 한국초전도저온공학회 2020 한국초전도저온공학회논문지 Vol.22 No.4
High-quality superconducting coplanar waveguide (SCPW) resonators are crucial for developing superconducting quantum information devices and sensors. We designed quarter-wavelength SCPW resonators and fabricated the SCPW resonators using Nb thin film. The resonant characteristics were measured at T = 4.2 K, revealing the intrinsic quality factor and the coupling quality factor to be Qi = 4,784 and Qc = 17, 980, respectively. Our design and fabrication techniques would be very useful to develop a gate-tunable superconducting qubit based on the semiconductor nanostructures.