• 전자공학회논문지CI
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• 제46권4호
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• pp.94-101
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• 2009

본 논문은 냉각형 적외선(infrared focal plane array; IRFPA) 영상시스템에서 하드웨어 뉴럴 네트워크를 이용한 실시간 고정패턴잡음 제어를 위해 고속 DSP & FPGA 기반의 H/W 설계 방법을 제안한다. 고정패턴잡음은 검출기의 불균일 보정처리후에도 관측영상의 온도분포 변화에 의해 발생한다. 이것은 열상 화질의 저하뿐만 아니라 다른 응용에도 문제되는 중요한 요소이다. 냉각형 적외선 영상시스템의 신호처리구조는 저온, 상온, 고온의 3개 테이블을 기준으로 이득(gain) 값과 편차(offset) 값을 연산한다. 제안된 방법은 3개 편차 테이블에서 각각 교차되는 영역을 세분화하여 가상의 테이블을 만들고, 입력 영상의 구분된 3개 영역에서 영상의 평균값으로 하드웨어 뉴럴 네트워크의 가중치 값을 조정하여 최적의 온도구간을 선정한다. 이와 같은 방법은 영상의 평균값으로부터 저온, 상온, 혹은 고온의 이득, 편차 테이블을 연산하고, 운용 중에 지속적으로 편차 보상을 적용하지 않아도 된다. 따라서 제안된 방법은 실시간 처리로 관측영상의 온도분포 변화에 의해 발생하는 고정패턴잡음을 제어하여 영상화질의 개선된 결과를 보였다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2006년도 학술대회
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• pp.175-177
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• 2006

This letter deals with non-pilot-aided symbol timing estimation methods in an orthogonal frequency division multiplexing (OFDM) system. To do this, OFDM system uses a frequency diversity scheme over two consecutive data symbols. Our approach can be viewed as an expansion of Schmidl's and Minn's correlation methods. Using the OFDM signal equipped with frequency diversity, however, symbol timing is accurately estimated without additional training symbol and a second-order diversity gain is achieved.

• 대한전자공학회논문지SP
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• 제47권4호
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• pp.97-104
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• 2010

본 논문에서는 비접촉식 도플러 바이오 레이더의 신호처리 시스템을 임베디드 하드웨어를 구현하였다. 실시간 처리를 빠르고 정확하게 수행할 수 있도록 DSP에 적합한 고속 알고리즘을 사용하여 구현하고 그 성능을 PC에서와 비교하였다. 영점에서 발생하는 데이터 손실 문제를 피하기 위하여 quardrature combining을 적용하였으며, 여러 가지 quardrature combining 방법 중에 DSP 실시간 연산에 적합한 알고리즘으로 arctangent combining을 선정하였다. IQ 신호의 원하는 DC 성분을 획득하면서 ADC에 다이나믹 레인지를 넘지 않도록 DC offset compensation 기법을 제안하였다. Texas Instrument 사의 C6711 DSP와 외장 12bit ADC를 사용하였고 최적화된 elliptic 필터를 설계하였으며 다양한 형태의 수신파형에서 심박수의 검출을 위하여 rate finding 블록에는 자기상관을 적용하는 알고리즘을 적용하였다. ECG와 측정값을 비교함으로 전체 시스템의 성능을 검증 하였고, 이를 통해 상용 가능한 휴대기기로 제작할 수 있도록 측정 거리의 변화에 상관없이 신뢰할 수 있는 시스템을 구축하였다.

• Structural Engineering and Mechanics
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• 제34권4호
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• pp.399-416
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• 2010

The purpose of this paper is to utilize the numerical assembly method (NAM) to determine the exact natural frequencies and mode shapes of a multi-step beam carrying multiple rigid bars, with each of the rigid bars possessing its own mass and rotary inertia, fixed to the beam at one point and supported by a translational spring and/or a rotational spring at another point. Where the fixed point of each rigid bar with the beam does not coincide with the center of gravity the rigid bar or the supporting point of the springs. The effects of the distance between the "fixed point" of each rigid bar and its center of gravity (i.e., eccentricity), and the distance between the "fixed point" and each linear spring (i.e., offset) are studied. For a beam carrying multiple various concentrated elements, the magnitude of each lumped mass and stiffness of each linear spring are the well-known key parameters affecting the free vibration characteristics of the (loaded) beam in the existing literature, however, the numerical results of this paper reveal that the eccentricity of each rigid bar and the offset of each linear spring are also the predominant parameters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.104-106
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• 2018

The harmonics and the DC offset in the grid can cause serious synchronization problems for grid connected inverters (GCIs) which leads not able to satisfy the IEEE 519 and p1547 standards in terms of phase and frequency variations. In order to guarantee the smooth and reliable synchronization of GCIs with the grid, Phase Locked Loop (PLL) is the crucial element. Typically, the performance of the PLL is assessed to limit the grid disturbances e.g. grid harmonics, DC Offset and voltage sag etc. To ensure the quality of GCI, the PLL should be precise in estimating the grid amplitude, frequency and phase. Therefore, in this paper a novel Robust PLL technique called Digital Lock-in Amplifier (DLA) PLL is proposed. The proposed PLL estimate the frequency variations and phase errors accurately even in the highly distorted grid voltage conditions like grid voltage harmonics, DC offsets and grid voltage sag. To verify the performance of proposed method, it is compared with other six conventional used PLLs (CCF PLL, SOGI PLL, SOGI LPF PLL, APF PLL, dqDSC PLL, MAF PLL). The comparison is done by simulations on MATLAB Simulink. Finally, the experimental results are verified with Single Phase GCI Prototype.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.545-548
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• 2002

Turbines have been known to be particularly susceptible to flow-induced self-excited vibration. In such vibrations, direct damping and cross stiffness effects of aerodynamic forces determine rotordynamic stability. In axial turbines with eccentric shrouded rotors, the non-uniform sealing gap causes azimuthal non-uniformities in the seal gland pressure and the turbine torque which destabilize the rotor system. Previously, research efforts focused solely on either the seal flow or the unshrouded turbine passge flow. Recently, a model for flow in a turbine with a statically offset shrouded rotor has been developed and some stiffness predictions have been obtained. The model couples the seal flow to the passage flow and uses a small perturbation approach to determine nonaxiymmetric flow conditions. The model uses basic conservation laws. Input parameters include aerodynamic parameters (e.g. flow coefficient, reaction, and work coefficient); geometric parameters (e.g. sealing gap, depth of seal gland, seal pitch, annulus height); and a prescribed rotor offset. Thus, aerodynamic stiffness predictions have been obtained. However, aerodynamic damping (i.e. unsteady aerodynamic) effects caused by a whirling turbine has not yet been examined. Therefore, this paper presents a new unsteady model to predict the unsteady flow field due to a whirling shrouded rotor in turbines. From unsteady perturbations in velocity and pressure at various whirling frequencies, not only stiffness but also damping effects of aerodynamic forces can be obtained. Furthermore, relative contributions of seal gland pressure asymmetry and turbine torque asymmetry are presented.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.471-474
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• 2004

Not all CCD pixels generate uniform value for the uniform radiance due to the different process of manufacture and each pixel characteristics. And the image data compression is essential in the real time image transmission because of the high line rate and the limited RF bandwidth. This pixel's nonuniformity and the loss compression make CCD pixel correction necessary in on-orbit condition. In the MSC system, the NUC unit, which is a part of MSC PMU, is charge of the correction for CCD each pixel. The correction is performed with the gain and the offset table for the each pixel and the each TDI mode. These correction tables are generated and programmed in the PMU Flash memory through the various image data tests at the ground test. Besides, they can be uploaded from ground station after onorbit calibration. This paper describes the principle of the table generation and the test way of the non-uniformity after NUC

• 자동차안전학회지
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• 제7권2호
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• pp.39-43
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• 2015

NDIR (Non-dispersive infrared Rays) alcohol sensor has been prototyped and its temperature characteristics were measured. In order to design novel optical alcohol sensor, elliptical structures with one common foci were modeled and analyzed their optical properties. After analyzing elliptic optical structures, a prototype alcohol sensor module was tested according to the temperature variations from $-20^{\circ}C$ to $35^{\circ}C$. The offset voltages of alcohol sensor decreased from 1.1056 V at the temperature $-20^{\circ}C$ to 0.7339 V at $35^{\circ}C$. However, the highest sensitivity of alcohol sensor showed about $303{\mu}V/ppm$ at room temperature.

• 한국CDE학회논문집
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• 제9권1호
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• pp.1-10
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• 2004

In the process of finite element analysis, mesh generation is tedious job which consumes tremendous time. Therefore, the automation of well shaped mesh generation from the minimal boundary input data is desirable to improve reliability and accuracy of the analysis and also to reduce the process time of the entire design process. The automation of triangular mesh generation has been relatively well treated due to its robustness and ease of handling when compared to rectangular element mesh generation. In this study, the offset method developed previously for generating plane rectangular element mesh has been corrected and modified to generate triangular element mesh on the B-spline surface having arbitrary holes. The result shows that the generated triangular mesh has the average aspect ratio over 0.9. The designed arbitrary surface shape has been interactively constructed by non-uniform B-spline theory for triangular mesh generation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.995-996
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• 2006

This paper presents a design of the PMOLED(Passive Matrix Organic light emitting diodes) driver IC improving the terminal current offset. The proposed methods are improving the design of the usual data output circuit. This methods can be avoidance brightness non-uniformity problem.