• Wind and Structures
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• 제35권5호
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• pp.323-336
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• 2022

This study investigates the applicability of the direct identification of flutter derivatives in the time domain using Rational Function Approximation (RFA), where the extraction procedure requires either a combination of at least two wind speeds or one wind speed. In the frequency domain, flutter derivatives are identified at every wind speed. The ease of identifying flutter derivatives in the time domain creates a paradox because flutter derivative patterns sometimes change in higher-order polynomials. The first step involves a numerical study of RFA extractions for different deck shapes from existing bridges to verify the accurate wind speed combination for the extraction. The second step involves validating numerical simulation results through a wind tunnel experiment using the forced vibration method in one degree of freedom. The findings of the RFA extraction are compared to those obtained using the analytical solution. The numerical study and the wind tunnel experiment results are in good agreement. The results show that the evolution pattern of flutter derivatives determines the accuracy of the direct identification of RFA.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.190-196
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• 1999

Continuation power flow has been developed to remove the ill-condition problem caused by singularity of power flow Jacobian at and near at steady-state voltage instability point in conventional power flow. Continuation power flow consists of predictor and corrector. In prddictor, the direction vector at the resent solution is caluculated and the initial guess of next solution is determined at the distance of step length. The selection of step length is a very important part, since computational speed and convergence performance are both greatly affected by the choice of the step length. This paper presents the practical step length selection algorithm using the reactive power generation sensitivith. In numulation, the proposed algorithm is compared with step length selection algorithm using TVI(tangent vector index).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1115-1119
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• 1996

The objective of this paper is to study on the idle speed control sing the fuzzy logic controller under load disturbance. The inputs of the fuzzy controller are error of rpm and rpm variation. The output of fuzzy controller is an ISC motor step. The airflow is controlled by the ISC motor movement and the idle speed is controlled by the airflow control. During the control, air to fuel ratio was checked by LAMBDA sensor. All experiments were carried in real vehicle.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 추계학술대회 논문집
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• pp.198-203
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• 1992

There are two important variables in machining process control, which are feed and cutting speed. It is possible to improve the machining accuracy and the productivity by maintaining the optimal feed and cutting speed. IN this work, a controller is designed to achieve on-line cutting force control based on the modeling of cutting process dynamics established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and the second is spindle speed control under the constant feed. Finally, both are proved to work properly through simulation and experimentation.

• 전자공학회논문지CI
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• 제47권5호
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• pp.1-9
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• 2010

일반적으로 동적 손동작 인식을 위해서는 전처리, 손 추적, 손 모양 검출의 단계가 필요하다. 본 논문에서는 전처리와 손 모양 검출 방법을 개선함으로써 성능을 향상시킨 동적 손동작 인식 방법을 제안한다. 전처리 단계에서는 동적테이블을 이용하여 노이즈제거 성능을 높이고, YCbCr 컬러공간을 이용한 기존의 피부색 검출 방식에서 피부색의 범위를 조절할 수 있도록 하여 피부색 검출 성능을 높인다. 특히 손 모양 검출 단계에서는 가이드라인을 이용하여 동적 손동작 인식의 요소인 시작이미지(Start Image)와 정지 이미지(Stop Image)를 검출하여 동적 손동작을 인식하기 때문에 학습예제를 사용한 손동작 인식 방법에 비해 인식 속도가 빠르다는 이점이 있다. 가이드라인이란 웹캠을 통해 입력되는 손의 모양과 비교하여 검출하기 위해 화면에 출력하는 손 모양의 라인이다. 가이드라인을 이용한 동적 손동작 인식 방법의 성능을 평가하기 위해 웹캠을 사용하여 복잡한 배경과 단순한 배경으로 구분된 9가지 동영상을 대상으로 실험하였다. 그 결과 CPU 점유율이 낮고, 메모리 사용량도 적기 때문에 시스템 부하가 높은 환경에 효과적임을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.2065-2069
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• 2004

This paper presents an adaptive equalizer using finite impulse response (FIR) filter and least-mean square (LMS) algorithm. Herein, the variable step-size technique (VSLMS) for compensating the amplitude of chrominance signal is utilized. The proposed equalizer can be enhanced and compressed the chrominance signal at color subcarrier. The LMS algorithm employed in simplicity structure but gives slow convergence speed. Thus, the variable step-size is very attractive algorithm due to its computational efficiencies and the speed of convergence is improved. In addition, experimental results are carried out by using the modulated 20T sine squared test signal. It is shown here that the adaptive equalizer can be equalized the amplitude chrominance distortion in color television transmission without relative delay distortion.

• 한국운동역학회지
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• 제12권1호
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• pp.47-61
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• 2002

The purpose of this study was to determined the force and moment of the ankle and the knee joint at different step length relative to the length of the lower extremity during a steady running. Six digital cameras(Qualisis) and a forceplatform(A.M.T.I) were used to obtain the kinematic data of the segments and kinetic data on the running at speed of 5.18m/s. The force and moment measured from six subjects participated in this study were limited to the support phase and their values were averaged at the moment of heel strike, mid stance, and toe off of a running for making a comparison between the condition 1(relative step length 1.1) and the condition 2(relative step length 1.4). It was concluded that internal forces except mediolateral force of the condition 2 were greater in the ankle and the knee joint than those of the condition 1, but all moments of condition 2 were greater from the descriptive statistic point of view. For the future study, it was needed to consider a number of subjects, a various running speed, and a individual step preference for applying generally results to the running strategy.

• 전기전자학회논문지
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• 제17권3호
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• pp.241-247
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• 2013

This paper presents the design of a System on Programmable Chip (SoPC) based on Field Programmable Gate Array (FPGA) for speech recognition in which Mel-Frequency Cepstral Coefficients (MFCC) for speech feature extraction and Vector Quantization for recognition are used. The implementing process of the speech recognition system undergoes the following steps: feature extraction, training codebook, recognition. In the first step of feature extraction, the input voice data will be transformed into spectral components and extracted to get the main features by using MFCC algorithm. In the recognition step, the obtained spectral features from the first step will be processed and compared with the trained components. The Vector Quantization (VQ) is applied in this step. In our experiment, Altera's DE2 board with Cyclone II FPGA is used to implement the recognition system which can recognize 64 words. The execution speed of the blocks in the speech recognition system is surveyed by calculating the number of clock cycles while executing each block. The recognition accuracies are also measured in different parameters of the system. These results in execution speed and recognition accuracy could help the designer to choose the best configurations in speech recognition on SoPC.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.166-177
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• 1998

Combustion characteristics of natural gas premixed flames is studied experimently and numerically by adopting a counterflow as a flamelet model in turbulent flames. Flame speeds are measured by employing LDV, and the results show that flame speed increases linearly with strain rate, which agrees well with numerical results. Parametric dependences of extinction strain rates are studied numerically with detailed kinetic mechanism to show that the addition of ethand to a methane premixed flame makes the flame more resistant to strain rate. The effect of pressure on the extinction strain rate is that the extinction strain rate increases up to 10 atm and them decreases, which is explained by competition of chain branching H+O2=OH+O and recombination reaction H+O2+M=HO2+M. Detailed mechanism having seventy-four step is systematically reduced to a nine-step and a five-step thermal NOx chemistry is reduced to two-step. Comparison between the results of the detailed and the reduced mechanisms demonstrates that the reduced mechanism successfully describes the essential features of natural gas premixed flames including extinction strain rate and NOx production.

• 한국산업정보학회논문지
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• 제21권3호
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• pp.1-6
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• 2016

LMS 알고리즘에서, 시간영역의 적응알고리즘은 입력신호의 고유치 분포 폭이 넓게 분포되면, 수렴속도가 느려지기 때문에 가변 스텝 사이즈가 많이 사용된다. 그러나 이 경우 많은 계산량이 필요하다. 본 논문에서는 시간영역의 적응 알고리즘을 변환영역에서 수행한다. 그리고 수렴성능 향상과 계산량을 줄이기 위하여 평균오차의 순시 절대 값을 exponential 함수에 적용한 새로운 알고리즘을 제안한다. 그리고 시스템 제너레이터를 이용하여 시뮬레이션 및 검증을 하였다. 그 결과 순시 절대 값에 비례하여 변화하는 가변스텝사이즈의 적응알고리즘이 기존의 알고리즘과 비교하여 보다 안정되고 성능이 우수함을 입증하였다.