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임수민,양연미,김재곤,백병주,이용훈,신정근 大韓小兒齒科學會 2008 大韓小兒齒科學會誌 Vol.35 No.2
Anchorage plays an important role in orthodontic treatment, Skeletal anchorage like the miniscrew is considered a more effective method in anchorage control than conventional anchorage which needs much patient s cooperation. The miniscrew offers many advantages. 1) It is easy to insert and to remove. 2) It can endure the force needed for moving teeth. 3) It can be immediately loaded and 4) Patient cooperation is not needed. 5) It is economic compared to other skeletal anchorage systems, In comparison to adult's bones, children s bones have comparatively poor bone quality and quantity. Therefore, it is hard to obtain primary stability in younger patients. However, if the miniscrew can be retained successfully, it will be effective in many orthodontic treatments. In these cases we used the miniscrew in correcting of diastema, in aligning dental midline, and in rendering a forced eruption of impacted tooth in mixed dentition patient. We obtained satisfactory results. 교정치료 시 고정원은 항상 염두에 두면서 치료를 진행해야 하는 중요한 요소이다. 전통적인 고정원을 이용한 치료는 환자의 적극적인 협조를 필요로 하고 원하는 치아이동에 대한 반작용이 나타날 수 있는 등의 부작용을 가지고 있다. 그러므로 보다 견고한 구강 내 고정원이 요구되어져 왔으며 이를 위해 miniscrew가 임상에서 흔히 이용되고 있다. Miniscrew를 통한 고정원의 확보는 구외력 의존도 감소,치료기간의 단축,식립 후 즉시 교정력 적용,환자의 협조도 불필요,식립의 간편성,저렴한 비용 등의 장점을 가지고 있다. 그러나 성장기 환자는 성인에 비해 골질이 좋지 않아 miniscrew의 성공률이 성인에 비해 낮다. 그러나 일단 고정에 성공하면 많은 교정치료 시 매우 유용하게 이용할 수 있다. 본 증례는 흔합치열기 환자를 miniscrew를 이용하여 정중이개 및 정중선 불일치,매복치에 대한 양호한 교정치료를 하였기에 보고하는 바이다.
Lim, Yeon-Geun,Cho, Yae Jee,Oh, Taeckkeun,Lee, Yongshik,Chae, Chan-Byoung IEEE 2018 IEEE wireless communications letters Vol.7 No.4
<P>In this letter, we provide a correlated channel model for a dual-polarization antenna in indoor small-cell multiple-input multiple-output (MIMO) systems. In an indoor environment, we confirm that the cross-polarization discrimination (XPD) in the direction of angle-of-departure can be represented as the spatial correlation of the MIMO channel. We also evaluate a dual-polarization antenna-based MIMO channel model and a spatially correlated channel model using a 3-D ray-tracing simulator. Furthermore, we provide the equivalent distance between adjacent antennas according to the XPD, providing insights into designing a dual-polarization antenna and its arrays.</P>
Waveform Multiplexing for New Radio: Numerology Management and 3D Evaluation
Lim, Yeon-Geun,Jung, Taehun,Kim, Kwang Soon,Chae, Chan-Byoung,Valenzuela, Reinaldo A. IEEE 2018 IEEE wireless communications Vol.25 No.5
<P>A 5G communication system includes massive machine-type communication, enhanced mobile broadband, and ultra-reliable low-latency communication. To meet the requirements of 5G applications, researchers have considered various scalable subcarrier spacings and transmission time intervals. In this article, we introduce the concept of waveform multiplexing, which is a resource management system for numerology multiplexing that employs appropriate waveforms to various numerologies. It also possesses both a dynamic cyclic prefix and a minimum guard band, which are the key features for achieving high spectral efficiency. We verify the significant gain produced by proposed waveform multiplexing by performing extensive 3D ray-tracing- based system-level evaluations in realistic 3D environments. Finally, we provide guidelines on waveform multiplexing design by considering the time-domain and frequency-domain characteristics of the new radio waveform candidates.</P>
Performance Analysis of Massive MIMO for Cell-Boundary Users
Yeon-Geun Lim,Chan-Byoung Chae,Caire, Giuseppe IEEE 2015 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.14 No.12
<P>In this paper, we consider massive multiple-input-multiple-output systems for both downlink and uplink scenarios, where three radio units connected via one digital unit support multiple user equipments at the cell-boundary through the same radio resource, i.e., the same time-frequency slot. For downlink transmitter options, the study considers zero forcing (ZF) and maximum ratio transmission (MRT), whereas for uplink receiver options, it considers ZF and maximum ratio combining (MRC). For the sum rate of each of these, we derive simple closed-form formulas. In the simple but practically relevant case where uniform power is allocated to all downlink data streams, we observe that, for the downlink, vector normalization is better for ZF whereas matrix normalization is better for MRT. For a given antenna and user configuration, we also analytically derive the signal-to-noise-ratio level below which MRC should be used instead of ZF. Numerical simulations confirm our analytical results.</P>
공간 상관도를 가지는 거대배열 다중안테나 시스템에서 압축채널 제한적 피드백 알고리즘
임연근(Yeon-Geun Lim),채찬병(Chan-Byoung Chae) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.7(통신이론)
본 논문에서는 높은 공간 상관도(spatial correlation)를 가지는 massive MIMO(multiple-input multiple-output) 시스템에서 Compressive Sensing 기반의 제한적 피드백 알고리즘을 제안한다. 현실적으로 많은 안테나를 설치하기 위해 기지국에서는 조밀한 uniform square array를 가정하였다. 또한 다중 사용자를 지원하기 위해 기지국에서는 영점강제(zero-forcing) 프리코더를 사용하였다. 시뮬레이션 결과, 제안한 피드백 알고리즘이 기존의 random vector quantization 코드북 보다 더 좋은 성능을 보이고 피드백 오버헤드와 코드북 인덱스를 찾는 계산량이 감소함을 보였다. In this paper, we propose a compressive sensing-based channel quantization feedback mechanism that is appropriate for practical massvie multiple-input multiple-output (MIMO) systems. We assume that the base station (BS) has a compact uniform square array that has a highly correlated channel. To serve multiple users, the BS uses a zero-forcing precoder. Our proposed channel feedback algorithm can reduce the feedback overhead as well as a codebook search complexity. Numerical simulations confirm our analytical results.