• 한국정보과학회논문지:소프트웨어및응용
• /
• 제37권5호
• /
• pp.378-385
• /
• 2010

이메일 사용의 증가로 수신 메일을 효율적이면서 정확하게 분류할 필요성이 점차 늘고 있다. 현재의 이메일 분류는 SVM, 베이지안 분류자, 규칙 기반 분류자 등을 이용하여 스팸 메일을 필터링하기 위한 이원 분류가 주를 이루고 있다. 그러나 이러한 지도 학습 방법들은 적합한 이메일을 인식하기 위하여서 사용자가 규칙이나 색인어 목록을 작성해야 한다. 비지도 학습 방법으로 군집을 이용한 다원 분류 방법은 메일의 분류 주제를 설정해주어야 한다. 본 논문에서는 비음수 행렬 분해(NMF, Non-negative Matrix Factorization)를 기반으로 한 자동 분류 주제 생성 방법과, 동적 분류 체계(DCH, Dynamic Category Hierarchy) 방법을 이용한 분류 주제 내에 이메일을 재구성하는 방법을 결합한 새로운 이메일 다원 분류 방법을 제안한다. 이 방법은 수신되는 이메일을 자동으로 다원 분류하여 대량의 메일을 효율적으로 관리할 수 있으며, 사용자가 분류 결과를 만족하지 못하면 분류 주제 내의 이메일을 동적으로 재구성하여 분류의 정확률을 높인다.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제9권6호
• /
• pp.428-434
• /
• 2004

Coarse clumping of solid materials within diseased biological cells can have a marked influence on the light scattering pattern. Perturbations in refractive index lead to distinct varia­tions in the cytometric signature, especially apparent over wide scattering angles. The large dynamic range of scattering intensities restricts collection of data to narrow angular intervals be­lieved to have the highest potential for medical diagnosis. We propose the use of an interfer­ence filter to reduce the dynamic range. Selective attenuation of scattering intensity levels is expected to allow simultaneous data collection over a wide angular interval. The calculated angu­lar transmittance of a commercial shortwave-pass filter of cut-off wavelength 580 nm indicates significant attenuation of scattering peaks below ${\~}\;10^{circ}$, and reasonable peak equalization at higher angles. For the three-dimensional calculation of laser light scattered by cells we use a spectral method code that models cells as spatially varying dielectrics, stationary in time. How­ever, we perform preliminary experimental testing with the interference filter on polystyrene microspheres instead of biological cells. A microfluidic toolkit is used for the manipulation of the microspheres. The paper intends to illustrate the principle of a light scattering detection system incorporating an interference filter for selective attenuation of scattering peaks.

• 한국항행학회논문지
• /
• 제16권6호
• /
• pp.900-909
• /
• 2012

저궤도 위성에 탑재하는 위성항법 수신기는 관측된 신호를 필터링하고 신호중단 시 궤도예측을 수행하는 항법필터를 장착하는데, 사용하는 위성동역학 모델이 필터성능을 주로 결정하게 된다. 본 연구에서는 항법필터에 필요한 정밀위성동역학 알고리듬을 연구하고 이를 계산하는 프로그램을 개발하였다. 정밀 중력가속도, 정밀좌표변환, 3체 중력, 대기저항, 태양복사압 모델을 결합하였으며, 해외 정밀궤도결정 프로그램을 이용하여 정확도를 검증하였다. 시뮬레이션과 실제 궤도 데이터를 사용하여 초기위치 정확도에 따른 궤도예측정확도를 분석 하였다. 개발된 모델은 위성탑재용 실시간 항법필터에 적용되는 동역학모델로는 충분한 정확도를 가지는 것을 확인하였다.

• 항공우주기술
• /
• 제7권2호
• /
• pp.162-169
• /
• 2008

추력제어를 목적으로 제작된 제어밸브를 AMESim 시뮬레이터를 통해 모델링을 수행했다. 제어밸브와 유사하게 모델링하여 여러 물리적인 동특성을 시뮬레이션을 통해 예측했다. BLDC 모터를 이용하는 제어밸브 제어를 위하여 속도제어기법을 제안했으며, 시뮬레이션 및 시험을 통해 그 성능을 증명했다. 제어밸브에 대한 2차 필터(Pre-Filters)를 사용하여 적절한 안정성 이득을 확보했다. BLDC 모터의 속도제어 기법을 이용하는 제어밸브는 PI 게인 스케줄링 기법 보다 시스템 활용 시 용이하고, 유량제어 시험결과를 통해 시스템에 적용 가능성을 시사했다.

• 전기학회논문지P
• /
• 제59권2호
• /
• pp.206-211
• /
• 2010

Since high-speed train is a dynamic load in which electric power is externally supplied, contact loss between the catenary and pantograph occurs. This phenomena including vibrations generates frequently irregular arcs, which, in turn causes EMI. Thus it is very important to develop the approach to reduce arc phenomenon by contact loss, as speed of electric railway vehicle increases. In case of an electric railway vehicle using electrical power, compared with diesel rolling stock, Power Line Disturbance(PLD) such as harmonics, transient voltage and current, Electromagnetic Interference(EMI), and dummy signal injection etc usually occur. In this study, the dynamic characteristics of a contact wire and a pantograph suppling electrical power to high-speed train are investigated with an electrical response point. To implement power line disturbance induced by contact loss phenomenon for high speed train operation, a hardware simulator which considers contact loss between contact wire and pantograph as well as contact wire deviation is developed. It is confirmed by the experiments that contact loss effect is largely dependent on voltage conditions when the contact loss occurs. Also, a passive filter is designed to reduce power disturbance and the designed system is verified by experiment.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 D
• /
• pp.660-662
• /
• 2000

The most important problem in traget tracking can be said to be modeling the tracking system correctly. Although the simple linear dynamic equation for this model has used until now, the satisfactory performance could not be obtained owing to uncertainties of the real systems in the case of designing the filters based on the dynamic equations. In this paper, we propose the extended robust Kalman filter(ERKF) which can be applied to the real target tracking system with the parameter uncertainties. To solve the robust nonlinear fettering problem, we derive the extended robust Kalman filter equation using the Krein space approach and sum quadratic constraint. We show the proposed filter has better performance than the existing extended Kalman filter(EKF) via 3-dimensional target example.

• International Journal of Aeronautical and Space Sciences
• /
• 제15권2호
• /
• pp.163-172
• /
• 2014

This paper proposes a novel guidance law based on the block backstepping sliding mode control and extended state observer (ESO), which also takes into account the autopilot dynamic characteristics of the near space interceptor (NSI), and the impact angle constraint of attacking the maneuvering target. Based on the backstepping control approach, the target maneuvers and the parameter uncertainties of the autopilot are regarded as disturbances of the outer loop and inner loop, respectively. Then, the ESO is constructed to estimate the target acceleration and the inner loop disturbance, and the block backstepping sliding model guidance law is employed, based on the estimated disturbance value. Furthermore, in order to avoid the "explosion of complexity" problem, first-order low-pass filters are also introduced, to obtain differentiations of the virtual control variables. The stability of the closed-loop guidance system is also proven, based on the Lyapunov theory. Finally, simulation results demonstrate that the proposed guidance law can not only overcome the influence of the autopilot dynamic delay and target maneuvers, but also obtain a small miss distance.

• 한국정밀공학회지
• /
• 제30권12호
• /
• pp.1321-1325
• /
• 2013

In this paper, we proposed an air bearing stage with active magnetic preloads in vertical directions compensating motion errors and attenuating vibrations to improve dynamic characteristics. This preloaded design gives simpler configuration of the stage, and active control of preload can be used for compensating motion errors by feedforward method. To improve dynamic characteristics, vibration of the table is monitored by an accelerometer, and controlled by a DSP based digital controller with integrator and band pass filters for suppressing roll and pitch vibration modes. The modes were evaluated by measuring frequency response functions, and compared with compensated responses. This showed effective results for suppressing poorly damped regenerative vibration of air bearings.

• 소음진동
• /
• 제6권2호
• /
• pp.215-224
• /
• 1996

Active vibration control is generally used to reduce vibration level by the actuators based on measured signal. Dynamic properties of a structure can be easily modified by the active vibration control, so that the vibration level may be effectively reduced to the magnitude below the allowable limit over a wide frequency rangs. In this paper, an instantaneous optimal control algorithm including acceleration feedback is presented for the active vibration control of large structures considering facts that the acceleration response can be easily measured, but the displacement and velocity response are obtained by numerically integrating the measured acceleration response with some errors. The adverse effect of the time delay is overcomed by taking into account the dynamic characteristics of an actuator and filters in the design of controller. Performance test is carried out using a hydraulic active mass driver on a test structure$(L{\times}W{\times}H;=;1200mm{\times}800mm{\times}1600mm, about;500kg)$ supported by four columns under base excitations. It is confirmed that the vibration level of the test structure are reduced to about 1/6 near resonance.

• 제어로봇시스템학회논문지
• /
• 제8권3호
• /
• pp.199-207
• /
• 2002

In this paper, a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype is discussed. Experimental results using a 1/4-ear simulator are discussed. Also, a suspension ECU prototype targeting real implementation is provided.