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Volume growth in the component of fibered twists
Kim, Joontae,Kwon, Myeonggi,Lee, Junyoung World Scientific Publishing 2018 Communications in Contemporary Mathematics Vol.20 No.8
<P>For a Liouville domain <TEX>$ W$</TEX> whose boundary admits a periodic Reeb flow, we can consider the connected component <TEX>$ [\tau ] \in \pi _{0}(\text{Symp}^{c}(Ŵ ))$</TEX> of fibered twists. In this paper, we investigate an entropy-type invariant, called the slow volume growth, in the component <TEX>$ [\tau ]$</TEX> and give a uniform lower bound of the growth using wrapped Floer homology. We also show that <TEX>$ [\tau ]$</TEX> has infinite order in <TEX>$ \pi _{0}(\text{Symp}^{c}(Ŵ ))$</TEX> if there is an admissible Lagrangian <TEX>$ L$</TEX> in <TEX>$ W$</TEX> whose wrapped Floer homology is infinite dimensional. We apply our results to fibered twists coming from the Milnor fibers of <TEX>$ A_{k}$</TEX>-type singularities and complements of a symplectic hypersurface in a real symplectic manifold. They admit so-called real Lagrangians, and we can explicitly compute wrapped Floer homology groups using a version of Morse-Bott spectral sequences.</P>
Longitudinal Impact of Depression on Quality of Life in Stroke Patients
EunSong Kim,JuWan Kim,HeeJu Kang,KyungYeol Bae,SungWan Kim,JoonTae Kim,ManSeok Park,KiHyun Cho,JaeMin Kim 대한신경정신의학회 2018 PSYCHIATRY INVESTIGATION Vol.15 No.2
Objective-Stroke is associated with significant long-term morbidity and poor quality of life (QOL). Depression is one of the most common complications after stroke and has been associated with QOL cross-sectionally. We investigated the longitudinal impact of depression in the acute phase of stroke on QOL 1 year after stroke. Methods-In total, 423 patients were evaluated 2 weeks after stroke, and 288 (68%) were followed 1 year later. QOL was assessed using the World Health Organization Quality of Life-Abbreviated form (WHOQOL-BREF) at baseline and follow-up. Depression was diagnosed according to Diagnostic and Statistical Manual of Mental Disorders-IV criteria; demographic and clinical characteristics data, including stroke severity, were obtained at baseline. The longitudinal associations of post-stroke depression (PSD) at baseline with QOL across two evaluation points were assessed using a repeated-measures analysis of variance. Results-The WHOQOL-BREF scores were significantly and persistently lower 1 year after stroke in patients with PSD at baseline compared with those without PSD at baseline independent of demographic and clinical characteristics, including stroke severity. Conclusion-PSD in the acute phase of stroke is an independent predictor of QOL in both the acute and chronic phases of stroke. Our findings underscore the importance of evaluating depression in the acute phase of stroke.
SSD상에서 해시조인 임시 파일의 효과적인 관리를 위한 블록 할당 방법
김준태 ( Joontae Kim ),이상원 ( Sangwon Lee ) 한국정보처리학회 2022 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.11 No.12
메모리보다 큰 대용량 테이블들에 대해 해시조인(Hash Join) 수행 시 임시 파일들을 생성해서 조인 과정에서 발생하는 임시 데이터 I/O를 수행하고 조인 종료 시에 그 파일들을 삭제한다. 본 논문에서는 해시조인용 임시 파일들을 하드디스크가 아닌 SSD상에서 관리할 때, 파일 생성 시 fallocate 시스템 콜 및 파일 삭제 관련 trim 옵션이 해시조인 성능에 큰 영향을 미치는 점을 밝힌다. 구체적으로 대표적인 오픈소스 데이터베이스인 PostgreSQL을 이용해서 다양한 상용 및 연구용 SSD 상에서 해시조인 수행 시, 임시 파일들에 대한 fallocate 및 trim 옵션 사용 여부에 따라 디폴트 조합에 비해 최대 약 3~5배 조인 성능 향상이 가능함을 보인다. 그리고, 임시 파일들에 대한 두 옵션의 조합여부에 따른 SSD내의 쓰기 증폭(Write Amplification)과 Trim 명령어 오버헤드가 조인 성능에 큰 영향을 미치는 점을 자세히 분석한다. Temporary files are generated when the Hash Join is performed on tables larger than the memory. During the join process, each temporary file is deleted sequentially after it completes the I/O operations. This paper reveals for that the fallocate system call and file deletion-related trim options significantly impact the hash join performance when temporary files are managed on SSDs rather than hard disks. The experiment was conducted on various commercial and research SSDs using PostgreSQL, a representative open-source database. We find that it is possible to improve the join performance up to 3 to 5 times compared to the default combination depending on whether fallocate and trim options are used for temporary files. In addition, we investigate the write amplification and trim command overhead in the SSD according to the combination of the two options for temporary files.
Downlink Beamforming with Imperfect Channel Information for a TDD-Based OFDMA System
YOON, Eunchul,KIM, Joontae The Institute of Electronics, Information and Comm 2009 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.92 No.9
<P>The beamforming weights which can suppress the interfering signal toward out-of-cell mobile stations in downlink are designed for a time division duplexing based OFDMA system when the channel information is not perfect. The derived beamforming weights do not improve the average SINR performance monotonously with the increased transmit SNR if the inverse of the transmit SNR is used as the regularization factor of the beamforming weights and the channel information obtained by the BS to design the BF weights is not perfect. Therefore, we suggest a simple scheme to select the regularization factor. The proposed beamforming weights improve the performance monotonously with the increased transmit SNR and achieve near-optimal performance. The performance achieved by applying the beamforming weights used in uplink to downlink beamforming is also investigated.</P>
전투기탑재 다기능 레이다의 공대공 및 공대지 동시 운용 모드를 위한 스케줄링 기법
김도운(Do-Un Kim),이우철(Woo-Cheol Lee),최한림(Han-Lim Choi),박준태(Joontae Park),박준현(Junehyune Park),서정직(JeongJik Seo) 한국항공우주학회 2021 韓國航空宇宙學會誌 Vol.49 No.7
본 논문은 전투기 레이다 공대공, 공대지 동시 운용 모드에서의 빔 스케줄링 방법을 다룬다. 양질의 전장 상황 인식을 위해 임무들의 우선순위와 더불어 공대공, 공대지 탐색 임무가 교차로 수행되어야 한다는 요구조건을 정립하였다. 그리고 이를 만족하기 위해 WMDD를 개선한 실시간 휴리스틱 빔 스케줄링 방법을 제안한다. 제안된 스케줄링 방법은 실제 레이다 임무 처리 메커니즘 및 측정 모델이 구현된 시뮬레이션 환경에서 비교 분석하였으며 임무 지연시간 관점에서의 성능향상을 확인하였다. This paper deals with a beam scheduling method in fighter interleaving mode. Not only the priority of tasks but also operational requirements that air-to-ground and air-to-air search tasks should be executed alternatively are established to maximize high-quality of situational awareness. We propose a real-time heuristic beam scheduling method that is advanced from WMDD to satisfies the requirements. The proposed scheduling method is implemented in a simulation environment resembling the task processing mechanism and measurement model of a radar. Performance improvement in terms of task delay time is observed.
SUV 차량용 전동식 능동 롤 제어 시스템의 성능 평가 기술 연구
전광기(Kwangki Jeon),최성진(Sungjin Choi),김준태(Joontae Kim),이경수(Kyongsu Yi) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.4
차량 선회 시 조종안정성과 주행 승차감을 향상시키기 위하여 능동적으로 차체의 롤(roll)을 줄이기 위한 연구가 진행되고 있다. 전동식 능동 롤 제어(ARC) 시스템은 전후 스테빌라이저바 중앙에 위치한 전동 모터 방식의 구동기에 의해 차량의 차체 롤을 제어한다. 본 연구에서는 이러한 전동식 ARC 시스템의 제어 성능 및 차량 동역학적 특성을 평가하고 검증하기 위한 해석, 벤치 시험, 실차 시험의 3단계 절차와 방법을 제안하였다. ARC 제어로직의 성능 및 타당성 평가를 위한 Matlab/Simulink와 CarSim 간의 연동-해석 방법을 제안하였고, ARC 구동기 및 시스템의 성능을 평가하기 위한 벤치 시험 방법과 실차 시험 방법을 제안하였다. Cornering maneuvers with reduced body roll and without comfort loss are important requirements for car manufacturers. An electric active roll control(ARC) system controls the body roll angle by using motor-driven actuators installed at the centers of the front and rear stabilizer bars. Co-simulation using the Matlab simulink controller model and the CarSim vehicle model were proposed to evaluate the performance of the ARC control algorithm. In order to validate the performance of the ARC actuator and system, bench tests and vehicle tests and vehicle method and procedure were proposed.