• ETRI Journal
• /
• 제33권1호
• /
• pp.27-31
• /
• 2011

This paper addresses estimating the frequency of a cisoid in the presence of white Gaussian noise, which has numerous applications in communications, radar, sonar, and instrumentation and measurement. Due to the nonlinear nature of the frequency estimation problem, there is threshold effect, that is, large error estimates or outliers will occur at sufficiently low signal-to-noise ratio (SNR) conditions. Utilizing the ideas of averaging to increase SNR and weighted linear prediction, an optimal frequency estimator with smaller threshold SNR is developed. Computer simulations are included to compare its mean square error performance with that of the maximum likelihood (ML) estimator, improved weighted phase averager, generalized weighted linear predictor, and single weighted sample correlator as well as Cramer-Rao lower bound. In particular, with smaller computational requirement, the proposed estimator can achieve the same threshold and estimation performance of the ML method.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2003년도 ICCAS
• /
• pp.366-370
• /
• 2003

This paper is on weighted model reduction using structurally balanced truncation. For a given weighted(single or double-sided) transfer function, a state space realization with the linear fractional transformation form is obtained. Then we prove that two block diagonal LMI(linear matrix inequality) solutions always exist, and it is possible to get a reduced order model with guaranteed stability and a priori error bound. Finally, two examples are used to show the validity of proposed weighted reduction method, and the method is compared with other existing methods.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1985년도 학술발표회 논문집
• /
• pp.87-94
• /
• 1985

In this paper, enhancement of speech corrupted by additive white or colored noise is stuided. The nuconstrained frequency-domain block least-mean-square (UFBLMS) adaptation algorithm and its frequency-weighted version are newly applied to speech enhancement. For enhancement of speech degraded by white noise, the performance of the UFBLMS algorithm is superior to the spectral subtraction method or Wiener filtering technique by more than 3 dB in segmented frequency-weighted signal-to-noise ratio(FWSNERSEG) when SNR of speech is in the range of 0 to 10 dB. As for enhancement of noisy speech corrupted by colored noise, the UFBLMS algorithm is superior to that of the spectral subtraction method by about 3 to 5 dB in FWSNRSEG. Also, it yields better performance by about 2 dB in FWSNR and FWSNRSEG than that of time-domain least-mean-square (TLMS) adaptive prediction filter(APF). In view of the computational complexity and performance improvement in speech quality and intelligibility, the frequency-weighted UFBLMS algorithm appears to yield the best performance among various algorithms in enhancing noisy speech corrupted by white or colored noise.

• 전자공학회논문지B
• /
• 제29B권11호
• /
• pp.93-101
• /
• 1992

HVS based transform coding techniques for still images take the lowest spatial frequency and luminance contrast sensitivity as the most crucial factors in determining the image quality perceived by human eye. Only the frequency weighting has been main issue. The proposed Weighted Discrete Cosine Transform (WDCT) has the lowest frequency of about 4 [cyc/deg] in 8$\times$8 subblock with the contrast-weighted DC coefficient. The error criteria have been rederived to adapt the contrast weighting for performance evaluation. The proposed scheme has produced higher quality images compared to the unweighted and other schemes.

• 한국정보통신학회논문지
• /
• 제5권3호
• /
• pp.443-449
• /
• 2001

잡음환경에서의 음성인식은 실제의 환경에서의 음성인식에서 매우 중요한 애로기술로써 이를 해결하기 위한 연구는 꾸준히 연구되고 있다. 따라서 본 연구는 음성인식분야에서 가장 많이 사용하고 있는 HMM처리 시잡음처리의 문제점을 주파수 가중치 부가 HMM으로 해결하는 방법을 제안하고 그 성능을 인식실험을 통하여 검토하였다. 그 결과 SS처리를 함께 사용하는 $MCE-\mu$, MCE-$\rho$가 가장 잡음에 강한 방식임을 알 수 있었다.

• 소음진동
• /
• 제5권1호
• /
• pp.29-35
• /
• 1995

This paper presents the simultaneous optimal design of structure and LQG control systems for the improvement of riding comforts of active vehicle suspension systems. The performance index of riding comforts is extended to include frequency-weighted acceleration in the quadratic cost functional. Janeway human response curve with respect to acceleration is used to verify the usefulness of the presented method. The method is applied to a half model of an active vehicle suspension systems with elastic body moving on randomly profiled road. The values of stiffness of suspensions are used for the structural design variables. The conjugate gradient method is used for optimization. The simulated results of simultaneous optimization with frequency-weighted cost functional are compared with those without frequency- weighted cost functional.

• 전자공학회논문지SC
• /
• 제39권1호
• /
• pp.33-41
• /
• 2002

본 논문에서는 기존의 주파수하중 균형절단 기법과 주파수하중 한켈노옴 근사화 기법에 비하여 더 작은 H∞ 하중 축소오차를 가지는 새로운 알고리듬을 제시한다. 제시한 알고리듬은 제한 실 보조정리로부터 반복적인 두 단계의 선형행렬부등식 형태로 유도한다. 또한 제안한 알고리듬을 성능보장을 위한 제어기 차수축소기법에 적용한다. 수치적 예를 통하여 제안한 알고리듬의 타당성을 보이고 기존의 모델 차수축소기법과 비교 분석하며 HIMAT(highly maneuverable aircraft technology) 시스템의 예를 통하여 성능보장을 위한 제어기 차수축소 기법에 적용할 수 있음을 보인다.

• 한국환경보건학회지
• /
• 제36권4호
• /
• pp.264-270
• /
• 2010

Agricultural workers are often exposed to high levels of dust during field operations. A systematic exposure assessment of annual task-weighted exposure has not been thoroughly examined. The occupational dust exposure in two wine grape vineyards was measured. Exposure levels to total and respirable dust were determined for a 1-year cycle of work. An operation profile including the frequency of tasks was established. The means of total and respirable dust exposure were $1.08\;mg/m^3$ and $0.07\;mg/m^3$, respectively. Based on the exposure for each task and the task frequency, task-weighted mean exposures to total and respirable dust were estimated as $1.115\;mg/m^3$ and $0.079\;mg/m^3$, respectively. The task-weighted exposure was significantly represented by three operations and could be attributed to the exposure frequency rather than the exposure intensity of operations. The measurement of a few of the most frequent tasks may be an alternative method of estimating task-weighted exposure. Agricultural dust exposure can be significantly reduced by targeting those tasks most important to task-weighted dust exposure.

• Smart Structures and Systems
• /
• 제25권2호
• /
• pp.255-264
• /
• 2020

This paper deals with a defect classification technique that considers the structural characteristics of a refrigerant compressor. First, the pressure pulsation of the refrigerant flowing in the suction pipe of a normal compressor was measured at the same time as the acceleration of the shell surface, and then the transfer function between the two signals was estimated. Next, the frequency-weighted acceleration signals of the defect classification target compressors were generated using the estimated transfer function. The estimation of the variance of the transfer function is presented to formulate the frequency-weighted acceleration signals. The estimated frequency-weighted accelerations were applied to defect classification using frequency-domain features. Experiments were performed using commercial compressors to verify the technique. The results confirmed that it is possible to perform an effective defect classification of the refrigerant compressor by the shell surface acceleration of the compressor. The proposed method could make it possible to improve the total inspection performance for compressors in a mass-production line.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1640-1641
• /
• 2007

In this paper, an experiment of weighted robust least squares frequency estimation for the Gaussian envelope chirp signal which is used in the time-frequency domain reflectometry system was carried out. By incorporating the forgetting factor to the frequency estimator, the weighted robust least squares filter achieved good enough frequency estimation performance for the chirp signal and it can be adopted to implement not only low cost time-frequency domain reflectometry but also real-time time-frequency domain reflectometry implementation.