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- 저자 : Lee Kyungjun (검색결과 129 건)
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Kyungjun Lee,성원진,장주욱 한국통신학회 2008 Journal of communications and networks Vol.10 No.4
We observe simultaneous transmission of relay stations (RSs) allowed in current IEEE 802.16j draft standard for multihop relay networksmay involve severe interference among the RSs, hence leading to throughput degradation. Allowing only 1/3 of the RSs to simultaneously transmit instead of 1/2 RSs as in the current draft standard reduces the interference but results in reduced throughput. To remedy this problem, we devise schemes to incorporate network coding at link-layer level (decode-and-forward) into the simultaneous transmission of RSs. Data movement is rearranged to maximize coding gain. Formula is derived to dictate exact movement of packets traveling between base station (BS) and mobile stations (MSs) via intermediate RSs. The frame structure in the current IEEE 802.16j draft standard does not allow broadcast needed for network coding. We devise a new frame structure which supports the broadcast. A new R-MAP (pointers to the burst data) is introduced to implement the broadcast. Since our new frame structure is used only for BS to RS or RS to RS communication, our schemes retain backward compatibility with legacy MSs based on IEEE 802.16e standard. Simulation based on simple configuration of RSs shows considerable improvement in terms of system throughput and round trip delay. For a 4-hop relay network with 1 BS and 4 RSs with symmetric traffic in uplink (UL) and downlink (DL), throughput is improved by 49% in DL and by 84% in UL traffic compared with IEEE 802.16j draft standard under the assumption that omni-directional antennae are used in BS and RSs.
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Lee, Woocheol,Jang, Jingon,Song, Younggul,Cho, Kyungjune,Yoo, Daekyoung,Kim, Youngrok,Chung, Seungjun,Lee, Takhee IOP Pub 2017 Nanotechnology Vol.28 No.13
<P>We fabricated 8?×?8 arrays of non-volatile resistive memory devices on commercially available Scotch<SUP>®</SUP> Magic<SUP>™</SUP> tape as a flexible substrate. The memory devices consist of double active layers of Al<SUB>2</SUB>O<SUB>3</SUB> with a structure of Au/Al<SUB>2</SUB>O<SUB>3</SUB>/Au/Al<SUB>2</SUB>O<SUB>3</SUB>/Al (50 nm/20 nm/20 nm/20 nm/50 nm) on attachable tape substrates. Because the memory devices were fabricated using only dry and low temperature processes, the tape substrate did not suffer from any physical or chemical damage during the fabrication. The fabricated memory devices were turned to the low resistance state at ∼3.5 V and turned to the high resistance state at ∼10 V with a negative differential resistance region after ∼5 V, showing typical unipolar non-volatile resistive memory behavior. The memory devices on the tape substrates exhibited reasonable electrical performances including a high ON/OFF ratio of 10<SUP>4</SUP>, endurance over 200 cycles of reading/writing processes, and retention times of over 10<SUP>4</SUP> s in both the flat and bent configurations.</P>
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New anti-wear alloy development & Biomass-caused equipment wear issues & mitigation strategy
Kyungjun Lee,Peter Blau,Jeffrey A. Lacey,George R. Fenske,Jun Qu 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.5
Quasicrystals have been used in various applications to improve wear resistance as well as friction. It is known that quasicrystal (i-phase) content and microstructure in alloys have a decisive effect on the mechanical properties, tribological performance, and corrosion behavior. In this research, four (β+i)-dual-phased quasicrystal alloys with different i-phase content and grain size were developed to alleviate the brittleness of the i-phase with the help of the soft β-phase. The influences of the i-phase content and grain size were investigated through impact test, wear test, and corrosion analysis. Through the annealing process, the amount of the i-phase was increased by about 38% (59.24% → 81.75%), and, besides, the grain size of the i-phase was simultaneously increased from 3.47 ㎛ up to 9.98 ㎛. As the amount of i-phase increased, it was possible to increase the hardness from 712 HV to 763HV. Meanwhile, the increased grain size (i-phase) reduced the contact stress of the grain during wear testing; thus, the specific wear rate could be decreased from 2.21×10<sup>-4</sup>mm³/Nm to 0.5×10<sup>-4</sup>mm³/Nm. Not only that, but an experimental wear equation was obtained using empirical data to predict the wear behavior of the dual phased alloys. As the second topic, the cutting tools’ material and working conditions are one of the most critical factors that directly affect the economic efficiency of the biomass size reduction process. Various biomass and accompanying extrinsic inorganic compounds like sand particles cause severe wear on the cutting tools. The generated wear modes varied, such as abrasive, erosive, and impact wear. In particular, the degree of wear of the blade cutting edge determines the cutting efficiency. Thus, by investigating the worn blades, we revealed the wear mechanism and measured the cutting edge’s rounding radius. Based on the results, candidate materials were selected, and a two-body and three-body abrasion test (ORNL) was conducted to compare and evaluate with the conventional blade. This study will provide a great indicator of the wear mechanism analysis and the material selection for diverse biomass comminution equipment.
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The Meaning of P50 Suppression : Interaction of Gamma and Alpha Waves
Lee, Kyungjun,Kang, Ung Gu The Korean Society of Biological Psychiatry 2014 생물정신의학 Vol.21 No.4
Objectives Sensory gating dysfunctions in patients with schizophrenia and bipolar disorder have been investigated through two similar methods ; P50 suppression and prepulse inhibition paradigms. However, recent studies have demonstrated that the two measures are not correlated but rather constitute as distinct neural processes. Recent studies adopting spectral frequency analysis suggest that P50 suppression reflects the interaction between gamma and other frequency bands. The aim of the present study is to investigate which frequency component shows more significant interaction with gamma band. Methods A total of 108 mood disorder patients and 36 normal subjects were included in the study. The P50 responses to conditioning and test stimuli with an intra-pair interval of 500 msec were measured in the study population. According to P50 ratio (amplitude to the test stimulus/amplitude to the conditioning stimulus), the subjects with P50 ratio less than 0.2 were defined as suppressed group (SG) ; non-suppressed group (NSG) consisted of P50 ratio more than 0.8. Thirty-five and 25 subjects were included in SG and NSG, respectively. Point-to-point correlation coefficients (PPCCs) of both groups were calculated between two time-windows : the first window (S1) was defined as the time-window of one hundred millisecond after the conditioning auditory stimulus and the second window (S2) was defined as the time-window of 100 msec after the test auditory stimulus. Spectral frequency analysis was performed to investigate which frequency band results in the difference of PPCC between SG and NSG. Results Significant reduction of PPCC between S1 and S2 was observed in the SG (Pearson's r = 0.24), compared to PPCC of the NSG (r = 0.58, p < 0.05). In spectral frequency analysis, gamma band showed "phase-reset" and similar responses after the two auditory stimuli in suppressed and non-suppressed group. However in the case of alpha band, comparison showed significantly low PPCC in SG (r = -0.14) compared to NSG (r = 0.36, p < 0.05). This may be reflecting "phase-out" of alpha band against gamma band at approximately 50 msecs after the test stimulus in the SG. Conclusions Our study suggests that normal P50 suppression is caused by phase-out of alpha band against gamma band after the second auditory stimulus. Thus it is demonstrated that normal sensory gating process is constituted with attenuated alpha power, superimposed on consistent gamma response. Implications of preserved gamma and decreased alpha band in sensory gating function are discussed.
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Lee, Seongsoo,Park, Junyong,Cho, Kyungjun,Lee, Hyunsuk,Seo, Chulhun,Ahn, Seungyoung,Kim, Joungho,Kim, Dong-Hyun,Cho, Yeonje,Kim, Hongseok,Song, Chiuk,Jeong, Seungtaek,Song, Jinwook,Park, Gyeyoung,Hong Institute of Electrical and Electronics Engineers 2019 IEEE transactions on industrial electronics Vol.66 No.6
<P>In this paper, we first proposed a novel hybrid loop array (HLA) for low leakage electromagnetic field (EMF) level and high efficiency in a wireless high power transfer system. The proposed HLA effectively enhances the system efficiency and shields leakage EMF in a wireless power transfer (WPT) system using kHz range resonant frequency. The key originality of the proposed HLA is the combination of two types of loop coil; shielding loop coil (SLC) and amplifying loop coil (ALC). SLCs reduce leakage EMF, and ALCs significantly enhance the magnetic field from a Tx coil. The simulation and experiment results show that the proposed solution successfully overcomes the limitations of the existing solutions. Analytical modeling and design procedure are introduced and discussed. In addition, the experimental verification of the simulation result is included. We first designed and modeled an HLA considering the coupling effect of neighboring loop coils to evaluate its efficiency and leakage EMF. With the proposed HLA, we demonstrated a 9.36% improvement in the efficiency and 3 dBm reduction in the leakage EMF near the WPT system.</P>
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Track-to-Track 센서 퓨전 방법을 이용한 고장 검출 알고리즘
김경준(Kyungjun Kim),이주인(Jooin Lee),이형철(Hyeongcheol Lee) 한국자동차공학회 2018 한국자동차공학회 부문종합 학술대회 Vol.2018 No.6
Recently, in the automotive industry, one of the most important mainstream is the intelligent vehicle. The intelligent vehicle acquires the information of the vehicle and its environments such as lane and a preceding vehicle. Then it provides convenience to the driver by using ADAS (Advanced Driver Assistance System) controller, for instance, LKA (Lane Keeping Assist), SCC (Smart Cruise Control), and FCA (Forward Collision-Avoidance Assist). It is important to get accurate sensing data of the vehicle and the environment. ISO26262 (“Road Vehicles- Functional safety”) is defined to address possible hazards of S/W and H/W for Automotive Electric/Electronic Systems. This paper deals with the FDI (Fault Detection and Isolation) algorithm to figure out the sensor faults of ADAS sensors and In-Vehicle Sensors such as IMU and Wheel Speed Sensors. Since it is hard to secure hardware redundancies of ADAS sensors, it creates underlying states of ADAS sensors and compares it with the outputs of the EKF composed of In-vehicle sensors. As the ADAS sensors, Front Camera, Left Camera, and Right Camera were selected.
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