• Information and Communications Magazine
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• v.19 no.11
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• pp.85-108
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• 2002

향후 다양한 무선 통신 규격들의 통합 수용을 위한 SDR (Software Defined Radio) 기술이IMT-2000 이후의 4세대 이동 통신 시스템을 위한 핵심 기술로써 심각하게 고려되고 있다. 이에 부응하여 SDR기반의 멀티모드용 통신 시스템을 구성하기 위한 주요 기술로서 디지털 IF 기술에 대한 필요성이 급속도로 고조되고 있는 상황이다. 최근 ABC/DAC 및 범용 디지털 신호처리 소자들의 고속화 및 고성능화로 인해 If (Intermediate Frequency) 대역과 기저대역 신호들 간의 직접 디지털 변환의 구현이 현실화되고 있다. 사용자의 관점에서 국지적으로 상용화되고 있거나 장래에 출현할 다양한 이동 통신 시스템 규격들 및 이에 대해 사업자들에게 할당되는 주파수 대역들이 서로 다른 점을 고려할 때, 이종 시스템 혹은 사업자들에게 할당된 주파수 대역에 구애받지 않고 언제 어디서나 자유롭게 무선 채널을 엑세스하고 또한 특정 채널을 임의로 선택하기 위한 디지털 If기술의 실현이 필수적이다 이러한 SDR기반 디지털 If 기술은 소프트웨어적으로 재구성 가능한 하드웨어 구조를 요구하며, 특정 이동 통신 규격의 물리 계층만을 지원하는 무선 인터페이스가 아닌 다중이동 통신 모드를 지원할 수 있는 유연성이 가미된 채널화 알고리즘이 필요하게 된다. 따라서 디지털 If기술은 무선 인터페이스 처리 부분, 즉 주파수 상 하향 변환 및 채별 선택 조합을 용도에 맞게 단일의 하드웨어 플렛폼 상에서 고속 디지털 신호처리 알고리즘을 기반으로 동작하기 위한 기능을 필연적으로 요구한다. 본 논문에서는 향후 SDR 기반의 기지국 및 단말기 운영 및 구생 모델을 제시하며, 디지털 If에 대한 필요성 및 동작 원리, 그리고 요소 기능들에 대한 구체적인 동작 원리 및 디지털 If와 더불어 활용 가능한 기술에 대하여 논의한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.442-448
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• 2006

This paper considers a home gateway(HG) that processes VOD services and controls home appliances. This paper proposes a PID algorithm-based adaptive bandwidth control method used in the HG, which guarantees QoS of incoming traffic such as VOD and real-time control data via control of outgoing traffic and have little effects on the CPU computation time. The proposed method is validated via implementation of real test environment.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.512-513
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• 2023

CNN 기반 Deep Learning 분야에서 객체 탐지 정확도를 높이기 위해 모델의 많은 Parameter 가 사용된다. 많은 Parameter 를 사용하게 되면 최소 하드웨어 성능 요구치가 상승하고 처리속도도 감소한다는 문제가 있어, 최소한의 정확도 하락으로 Parameter 를 줄이기 위한 여러 Pruning 기법이 사용된다. 본 연구에서는 Neural Architecture Search(NAS) 기반 Channel Pruning 인 Artificial Bee Colony(ABC) 알고리즘을 사용하였고, 기존 NAS 기반 Channel Pruning 논문들이 Classification Task 에서만 실험한 것과 달리 Object Detection Task 에서도 NAS 기반 Channel Pruning 을 적용하여 기존 Uniform Pruning 과 비교할 때 파라미터 수 대비 정확도가 개선됨을 확인하였다.

• Journal of the Korean Society of Radiology
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• v.11 no.1
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• pp.9-17
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• 2017

A high degree of precision and accuracy in Gamma Knife Radiosurgery(GKRS) is a fundamental requirement for therapeutical success. Elaborate radiation delivery and dose gradients with the steep fall-off of radiation are clinically applied thus necessitating a dedicated Quality Assurance(QA) program in order to guarantee dosimetric and geometric accuracy and reduce all the risk factors that can occur in GKRS. In this study, as a part of QA we verified the accuracy of single-shot dose profiles used in the algorithm of Gamma Knife Perfexion(PFX) treatment planning system employing Variable Ellipsoid Modeling Technique(VEMT). We evaluated the dose distributions of single-shots in a spherical ABC phantom with diameter 160 mm on Gamma Knife PFX. The single-shots were directed to the center of ABC phantom. Collimating configurations of 4, 8, and 16 mm sizes along x, y, and z axes were studied. Gamma Knife PFX treatment planning system being used in GKRS is called Leksell GammaPlan(LGP) ver 10.1.1. From the verification like this, the accuracy of GKRS will be doubled. Then the clinical application must be finally performed based on precision and accuracy of GKRS. Specifically the width at the 50% isodose level, that is, Full-Width-of-Half-Maximum(FWHM) was verified under such conditions that a patient's head is simulated as a sphere with diameter 160mm. All the data about dose profiles along x, y, and z axes predicted through VEMT were excellently consistent with dose profiles from LGP within specifications(${\leq}1mm$ at 50% isodose level) except for a little difference of FWHM and PENUMBRA(isodose level: 20%~80%) along z axis for 4 mm and 8mm collimating configurations. The maximum discrepancy of FWHM was less than 2.3% at all collimating configurations. The maximum discrepancy of PENUMBRA was given for the 8 mm collimator along z axis. The difference of FWHM and PENUMBRA in the dose distributions obtained with VEMT and LGP is too small to give the clinical significance in GKRS. The results of this study are considered as a reference for medical physicists involved in GKRS in the whole world. Therefore we can work to confirm the validity of dose distributions for all collimating configurations determined through the regular preventative maintenance program using the independent verification method VEMT for the results of LGP and clinically assure the perfect treatment for patients of GKRS. Thus the use of VEMT is expected that it will be a part of QA that can verify and operate the system safely.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.601-608
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• 2015

The static aeroelastic analysis and optimization of flexible wings are conducted for steady state conditions while both aerodynamic and structural parameters can be used as optimization variables. The system of multidisciplinary design optimization as a robust methodology to couple commercial codes for a static aeroelastic optimization purpose to yield a convenient adaptation to engineering applications is developed. Aspect ratio, taper ratio, sweepback angle are chosen as optimization variables and the skin thickness of the wing. The real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was used to control the optimization process. The support vector regression(SVR) is applied for optimization, in order to reduce the time of computation. For this multi-objective design optimization problem, numerical results show that several useful Pareto optimal designs exist for the flexible wing.

• Journal of Korea Society of Industrial Information Systems
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• v.26 no.5
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• pp.11-19
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• 2021

In this paper, we proposed an asymmetric multi-core processor scheduling scheme which is based on the mileage of each core. We considered a big-LITTLE multi-core processor structure, which consists of low power consuming LITTLE cores with general performance and high power consuming big cores with high performance. If a task needs to be processed, the processor decides a core type (big or LITTLE) to handle the task, and then investigate the core with the shortest mileage among unoccupied cores. Then assigns the task to the core. We developed a mileage-based balancing algorithm for asymmetric multi-core assignment and showed that the proposed scheduling scheme is more cost-effective compared to the traditional scheme from a management perspective. Simulation is also conducted for the purpose of performance evaluation of our proposed algorithm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.3
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• pp.52-58
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• 2009

If a moving target has a linear characteristics, the Kalman filter can estimate relatively accurate the location of a target, but this performance depends on how the dynamic status characteristics of the target is accurately modeled. In many practical problems of tracking a maneuvering target, a simple kinematic model can fairly accurately describe the target dynamics for a wide class of maneuvers. However, since the target can exhibit a wide range of dynamic characteristics, no fixed SKF(Simple Kalman filter) can be matched to estimate, to the required accuracy, the states of the target for every specific maneuver. In this paper, a new AKF(Active Kalman filter) is proposed to solve this problem The process noise covariance level of the Kalman filter is adjusted at each time step according to the study result which uses the neural network algorithm. It is demonstrated by means of a computer simulation that the tracking capability of the proposed AKF(Active Kalman filter) is better than that of the SKF(Simple Kalman Filter).