The lenses are important elements in optical imaging systems. However, lenses are liable to defects such as dusts and thus deteriorate their imaging quality. These kinds of imaging systems are investigated in this thesis .The polluted lens can be verified equivalent to a polluted random screen set against a clean lens .In our model ,the defects on random screen are assumed poisson-distribution ,overlapped and the transmittance effect of each defect is multiplicative .The autocorrelation function of screen is obtained by defects' density ,radius ,and transmittance. The evaluation of the optical transfer function for this imaging system can be achieved by the autocorrelation of the above random screen. This thesis includes computer simulation, experiments and comparison with other model and restoration method. The experiments are set up by the instruments including the video camera , capture card ,and personal computer. We may estimate the key parameters of our theoretical autocorrelation function by the real optical transfer function obtained from experiment. Accordingly, two methods are applied to image restoration in this thesis. One is to use the theoretical autocorrelation, the other is to use a second-order statistics of optical transfer function. The computation of second-order statistics involves a fourfold integration .By the help of changing variables and geometric analysis, we simplify the fourfold integration to double integration. Both of our methods are better for image restoration in RMS value than the method proposed by Tamas Daboczi

Noise variance estimator is very important in communication system which could control the transmission power and help system to reach the maximum capacity. But almost every kind of noise variance estimators assume that channel status is perfectly. Unfortunately the estimation error is always existence. This paper discuss that the maximum likelihood noise variance estimator (ML-NVE) in orthogonal frequency division multiplexing (OFDM) system with estimated channel. We take two kinds of the most popular channel estimation (CE) schemes Least Square (LS) and Modified-Least Square (MLS) as our consideration. And we investigate the situation that the ML-NVE suffered by carrier frequency offset (CFO) due to imperfect synchronization. As result we will show off the mean and variance of ML-NVE in those situations.

Thesis (M.S.M.E.)--University of Washington, 2009. / Includes bibliographical references (p.75-77). Also available on the World Wide Web.

Thesis (M.S.M.E.)--University of Washington, 2009. / Title from Web page (viewed on Feb. 3, 2010). Includes bibliographical references (p.75-77).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Speech; noise reduction; spectral subtraction; hands-free; beamforming. Includes bibliographical references (p. 171-189).

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2004. / Includes bibliographical references (p. 70-72).

Thesis (Ph. D.)--School of Physics, Georgia Institute of Technology, 2004. Directed by Kurt Wiesenfeld. / Includes bibliographical references (leaves 122-128).

Thesis--Ph. D., University of Hong Kong.

The motion of tissues within the human body can be investigated by a number of techniques, including ultrasonic echography. The ultrasonic echo patterns from regions of relatively homogeneous tissue bear an ambiguous relationship to their spatial structure, preventing the use of an lmaging system to study the motion of such tissue. This work describes the development and use of a method of analysing the ultrasonic echoes from tissue to investigate their motion. The properties of the echoes from tissue are studied using a theoretical model, and a number of methods of analysing the echoes are suggested. The theoretical model can also be used to simulate the ultrasonic imaging of such tissues. The apparatus for obtaining and analysing the echoes from tissues is described, with an investigation of the errors involved in the digitisation of analogue signals. The methods of echo analysis proposed for the study of tissue motion are evaluated experimentally, using specimens of fixed liver, and the results show that a correlation method of analysis provides the most consistent measure of tissue motion. This method is applied to the analysis of the in vivo motion of soft tissue. The majority of measurements are taken on the livers of normal subjects, with a simultaneous recording of the electrocardiograph. The amplitude, frequency and phase of the motion are measured and the results correlated with the electrocardiograph. The conclusions from this work are that the stochastic properties of the ultrasonic echoes from soft tissues require the use of statistical methods of analysis to study successfully tissue motion. Estimates are made of the extent to which the phenomenon of tissue motion can be used in the characterisation of the pathological state of tissue.

Walking models have been used to explore concepts such as energy, step variability, control strategies and redundancy in walking. A 2-D dynamic walking model was used to determine the levels of variability in gait while being perturbed. The perturbations were added in the form of randomly added noise applied at different magnitudes. The model was comprised of two equal length legs and masses at the feet and hips. The model walked on a flat surface and each step was initialed by an impulse at the swing leg. The magnitude of the impulse determined the size of the model's steps. In this study, the walker took steps with lengths that were than were analogous to humans. An attempt to offset the effect of the noise was made by adding a proportional controller to correct the errors of the applied impulse. The control equation was comprised of gain, A, and noise, [xi], term. The step length, time and speed were calculated to analyze how the model walks. It was hypothesized that the model would use a strategy similar to humans on a treadmill and follow a goal equivalent manifold. The manifold was all possible solutions of step length and step time for maintaining constant speed. Any fluctuations in step length and time would still result in constant speed. The results showed that the model's gait became more variable as noise was added. When the control was added through the gain being increased, the model steps became more variable. The model did not follow the same control strategy as humans and coordinate steps along the GEM. As the model began taking longer step lengths the step time decreased. / text