• 전자공학회논문지CI
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• 제45권1호
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• pp.37-47
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• 2008

DSP에서 제공되는 주소 생성 유닛은 데이터 패스와 병렬적으로 주소 연산을 수행할 수 있게 해 줌으로써, DSP 코드 생성에 중요한 역할을 한다. 프로그램 변수들의 메모리 레이아웃을 결정하는 문제는 주소 생성 유닛의 기능을 이용하여 주소 연산용 명령어를 줄이는 최적화이다. 메모리 레이아웃 생성 단계와 주소 포인터 할당 단계로 구분 되는 이 최적화에서 본 논문은 주소 연산 코드의 수가 최소가 되도록 DSP용 코드 생성의 효과적인 주소 포인터 할당 문제를 다룬다. 제안하는 알고리즘은 고정된 메모리 레이아웃을 가질 때 주소 포인터 할당을 수행하는 기존의 알고리즘의 시간 복잡도를 줄이는 기법이다. 메모리 크기와 수행 시간을 줄이기 위해 알고리즘을 수행할 때 핵심적인 요소들만을 고려하도록 강한 가지치기 방법을 사용하였다. 또한 주소 포인터 할당 문제는 메모리 레이아웃에 영향을 크게 받는 문제이기 때문에 본 논문은 주어진 메모리 레이아웃을 갱신하여 반복적으로 성능을 개선하는 방법을 제안한다. 약 3,000여개의 실제 프로그램으로부터 얻은 변수 접근 시퀀스를 제공하는 OffsetStone 벤치마크를 이용한 실험결과를 통해 본 논문에서 제안한 기법과 알고리즘을 테스트 했다. 제안한 방법은 전통적인 방법보다 평균 25.9%의 적은 주소 코드를 생성해 냄을 보인다.

• 대한조선학회논문집
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• 제43권4호
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• pp.512-520
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• 2006

The effects of flexibilities of supporting structures on shaft alignment are growing as ship sizes are Increasing mainly for container carrier and LNG carrier. But, most of classification societies not only do not suggest any quantitative guidelines about the flexibilities but also do not have shaft alignment design program considering the flexibility of supporting structures. A newly developed program, which is based on innovative shaft alignment technologies including nonlinear elastic multi-support bearing concept and hull deflection database approach, has S basic modules : 1)fully automated finite element generation module, 2) hull deflection database and it's mapping module on bearings, 3) squeezing and oil film pressure calculation module, 4) optimization module and 5) gap & sag calculation module. First module can generate finite element model including shafts, bearings, bearing seats, hull and engine housing without any misalignment of nodes. Hull deflection database module has built-in absolute deflection data for various ship types, sizes and loading conditions and imposes the transformed relative deflection data on shafting system. The squeezing of lining material and oil film pressures, which are relatively solved by Hertz contact theory and built-in hydrodynamic engine, can be calculated and visualized by pressure calculation module. One of the most representative capabilities is an optimization module based on both DOE and Hooke-Jeeves algorithm.

• Journal of Astronomy and Space Sciences
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• 제38권3호
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• pp.157-164
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• 2021

We describe a method for the in-orbit calibration of body-mounted magnetometers based on the CHAOS-7 geomagnetic field model. The code is designed to find the true calibration parameters autonomously by using only the onboard magnetometer data and the corresponding CHAOS outputs. As the model output and satellite data have different coordinate systems, they are first transformed to a Star Tracker Coordinate (STC). Then, non-linear optimization processes are run to minimize the differences between the CHAOS-7 model and satellite data in the STC. The process finally searches out a suite of calibration parameters that can maximize the model-data agreement. These parameters include the instrument gain, offset, axis orthogonality, and Euler rotation matrices between the magnetometer frame and the STC. To validate the performance of the Python code, we first produce pseudo satellite data by convoluting CHAOS-7 model outputs with a prescribed set of the 'true' calibration parameters. Then, we let the code autonomously undistort the pseudo satellite data through optimization processes, which ultimately track down the initially prescribed calibration parameters. The reconstructed parameters are in good agreement with the prescribed (true) ones, which demonstrates that the code can be used for actual instrument data calibration. This study is performed using Python 3.8.5, NumPy 1.19.2, SciPy 1.6, AstroPy 4.2, SpacePy 0.2.1, and ChaosmagPy 0.5 including the CHAOS-7.6 geomagnetic field model. This code will be utilized for processing NextSat-1 and Small scale magNetospheric and Ionospheric Plasma Experiment (SNIPE) data in the future.

• 한국인쇄학회지
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• 제18권1호
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• pp.83-94
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• 2000

The mottling in coated paper is one of the most difficult problems to solve in the area of offset printing. The prevention of mottling requires optimization of coating color formation, especially the minimum of binder migration. In this paper, we studied a mottling. Kaolin clay and CaCO3 as pigment, starch and latex as binder of coating color were used in this study. We have measured surface property of 24 coated samples through k value, mottle value and transferred ink. In the equation of Walker and Fesko, the value of k was the highest and that of mottle and the mount of transferred ink were the lowest in kaolin 60 part. And it is more easy to analyze the various surface of coated paper when sample was exposed on IR.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.413-414
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• 2008

A 2.4 GHz low phase noise fully integrated LC voltage-controlled oscillator (VCO) in $0.18\;{\mu}m$ CMOS technology is presented in this paper. The VCO is optimized based on phase noise reduction. The design of the VCO uses differential varactors which are adopted for symmetry of the circuit, and consider AM-PM conversion due to a cross-coupled pair. The VCO is designed to draw 3 mA from 1.8 V supply voltage. Simulated phase noise is -137.3 dBc/Hz at 3 MHz offset. The tuning range is found to be 300 MHz range from 2.3 GHz to 2.6 GHz.

• 전력전자학회논문지
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• 제19권6호
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• pp.538-548
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• 2014

This study provides a robust control of a grid-connected three-phase two-level photo voltaic inverter. The introduced control method uses the cascade control strategy to regulate AC-side current and DC-link voltage. A robust controller with integration action is used for the inner-loop AC-side current control, which maximizes the convergence rate using a linear matrix inequality-based optimization design method and eliminates the offset error. The robust controller design method considers the parameter uncertainty set to accommodate parameter mismatch and un-modeled components in the inverter model. An outer-loop proportional-integral controller is used to regulate DC-link voltage with linearization of DC/AC relation. The proposed control strategy is applied to a grid-connected 100 kW photo voltaic inverter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3842-3855
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• 2018

A novel image completion method is proposed that uses the advantage of planar structural information to fill corrupted portions of an image. First, in estimating parameters of the projection plane, the image is divided into several planes, and their planar structural information is analyzed. Second, in calculating the a priori probability of patch and patch offset regularity, this information is converted into a constraint condition to guide the process of filling the hole. Experimental results show that the proposed algorithm is fast and effective, and ensures the structure continuity of the damaged region and smoothness of the texture.

• 대한의용생체공학회:의공학회지
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• 제13권3호
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• pp.217-224
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• 1992

A new three-channel surface gradient coil obtained by using numerical optimization and its application to MR computerized nomography are presented. The new surface gradient coil pro aided linear field gradient region more than twice wider compared with the t'irst surface gradi encl coil, removed torque and field offset, and reduced coupling between the surface gradient coil and combined surface rf coil. We realized the new surface gradient coil set with $30{\times}60{cm^2}$2 size, which generated more tharl 4G/cm with 100 amperes over a $4{\times}4{\times}4{cm^3}$ region with good linearity. The optimal geometries of the three-channel surface gradient coil and volun teer's high-resolution in wiuo spinal cord Images obtained by using the optimized surface gradi ent coil set are presented.

• 한국통신학회논문지
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• 제31권7C호
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• pp.735-742
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• 2006

본 논문에서는 IEEE 802.16e OFDMA(Orthogonal Frequency Division Multiplexing-FDMA) TDD(Time Division Duplexing) 시스템 단말 수신기의 입력 신호에 대하여 DC 오프셋 보상, 자동 주파수 조정, 자동 이득 조정을 수행하는 DFE(Digital Front End)의 동작 원리와 Fixed-point 설계 방법에 대하여 설명하고, DFE의 성능을 ITU-R M. 1225 Veh-A 60km/h 채널 환경에서 시뮬레이션 결과를 통해 분석한다. DFE의 Fixed-point 설계시, 시스템의 성능에 영향을 주지 않는 범위 내에서 연산을 통해 출력되는 bit의 크기를 줄임으로서때 H/W 동작의 복잡도를 줄이고, Acquisition time과 안정도 간의 Trade-off를 고려하여 Loop Filter를 설계함으로서 DFE 의 Fixed-point 설계를 최적화 한다.

• 디지털콘텐츠학회 논문지
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• 제6권1호
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• pp.41-48
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• 2005

잡음환경이 열악하고 대역폭이 부족한 HFC 망 상향채널에서 보다 나은 대칭형 멀티미디어 서비스를 제공할 수 있는 S-DMT 방식의 상향 채널 케이블모뎀을 위한 심볼 타이밍 복원 알고리즘을 제안하고 그에 대한 성능을 평가하였다. 타이밍 복원 알고리즘은 시간 영역에 PN 시퀀스를 삽입하는 방식을 제안하였으며 AWGN, ISI, 및 임펄스 잡음 환경에서 시뮬레이션을 통해 성능을 평가 하였다. 성능 평가 결과, PN 시퀀스 삽입 알고리즘에 의한 타이밍 복원방식은 잡음 환경에 따라 타이밍 추정 성능이 매우 달라지며, 동일한 샘플링 클럭 오프셋에서 AWGN, ISI, 및 임펄스 잡음이 함께 존재하는 채널일 경우가 임펄스 잡음 채널 경우보다 타이밍 실패 확률이 $10^3$일 때의 Eb/No가 10dB 이상 열화되나 초기부터 샘플링 클럭 오프셋을 보정하여 최적화한 경우 잡음환경에 의한 성능차이가 있으나 비교적 양호한 타이밍 추정 성능을 보임을 확인 하였다.