Error Estimation of Linear Polarization Data from Coronagraphs – Application to STEREO-A/SECCHI-COR1 Observations

We attempt to quantitatively study the uncertainties of the polarized brightness and for the polarization angle which are to be expected for measurements from noisy image detectors in classical coronagraphs. We derive the probability density functions (PDF) which apply to polarization observations with polarization filters at 0∘, 60∘ and 120∘. The noise in the directly observed image intensities is assumed to be normally distributed. We find that for low and medium signal-to-noise ratios the polarized brightness obeys a distribution with a strongly biased mean which, if not taken account of, leads to an overestimation of the polarized brightness and degree of polarization. The PDFs are compared with data from the SECCHI-COR1 coronagraph onboard STEREO-A in order to detect systematic or random perturbations of the polarized brightness and the polarization angle beyond the unavoidable photon and detector hardware noise. This noise is estimated from two successive filter sequences taken in-flight during calm coronal conditions on 18 May 2008 and is expressed in the form of an intensity–variance relation. Two small deviations between the measured distributions and the predicted PDF for the polarization angle were found. The standard deviation of the polarization angle error decreases with increasing signal-to-noise ratio of the polarized brightness. For ratios larger than about 8 this decrease was found not as steep anymore as predicted which could hint to a small additional noise source. Next, we found a systematic constant deviation of the polarization angle by $-1^{\circ }$ − 1 ∘ for all signal-to-noise ratios of the polarized brightness. Besides these small discrepancies, our theoretically derived PDFs agree quite well with the distributions of measured brightnesses in test regions of the images. The PDFs we present here can equally be applied to similarly measured data from other coronagraphs and may help to quantify uncertainty limits of the derived polarization. They can be used for in-flight health checks of an instrument, are useful when separating unpolarized stray light from the polarized K-corona and when comparing the observed polarization data with results from model simulations.

The Influence of Group and Individual Physiotherapy on Balance of Children with Impaired Language and Communication

Communication disorder is a relatively constant deviation from the agreed standards of speech, language and communication. It is observed that communication disorders such as alalia, dysarthria, often go with disorders of gross and small motor functions, movements which lack of rhythm, impaired balance. The aim of the study was to test the efficiency of group and individual physiotherapy on balance for children with impaired language and communication. The study included 75 children aged 3–6 years. The target was divided into two groups: the exploratory group consisted of children who had impaired language and communication and the disorder is not due to other disorders; the control group consisted of children of the same age whose development was normal and they did not have language or other problems. The tested group children were divided into two groups at random: the first and the second. The first group underwent individual physiotherapy, while the second one participated in group physiotherapy. Procedures of physiotherapy lasted for 2 months, 2 times per week. Their duration was 30 minutes. The physiotherapy program consisted of various balance exercises standing or moving, using smaller base of support or soft balance platforms. Various games were also used during the group physiotherapy sessions. Conclusions. Balance of the three–six year old children with language and communication disorders was significantly worse than that of their healthy peers. Children balance depends on the degree of language impairment: children with an average degree of undeveloped language disorder demonstrated balance significantly better than that of children with significant language undevelopment. Balance of pre-school children with language and communication disorders statistically significantly improved in both individual and group physiotherapy procedures. Balance of children with language and communication disorders who had individual therapy improved a little more than those in the group therapy but the difference was not statistically significant.Keyword: language and communication disorders, physical therapy, postural control.

A New Wavelet Threshold Function and Denoising Application

In order to improve the effects of denoising, this paper introduces the basic principles of wavelet threshold denoising and traditional structures threshold functions. Meanwhile, it proposes wavelet threshold function and fixed threshold formula which are both improved here. First, this paper studies the problems existing in the traditional wavelet threshold functions and introduces the adjustment factors to construct the new threshold function basis on soft threshold function. Then, it studies the fixed threshold and introduces the logarithmic function of layer number of wavelet decomposition to design the new fixed threshold formula. Finally, this paper uses hard threshold, soft threshold, Garrote threshold, and improved threshold function to denoise different signals. And the paper also calculates signal-to-noise (SNR) and mean square errors (MSE) of the hard threshold functions, soft thresholding functions, Garrote threshold functions, and the improved threshold function after denoising. Theoretical analysis and experimental results showed that the proposed approach could improve soft threshold functions with constant deviation and hard threshold with discontinuous function problems. The proposed approach could improve the different decomposition scales that adopt the same threshold value to deal with the noise problems, also effectively filter the noise in the signals, and improve the SNR and reduce the MSE of output signals.

The Research of Maglev Gyroscope Data Characteristics Based on Two Positioning

Through the analysis of two-position sampling data based on the maglev gyroscope north seeking theoretical model and the verification of north seeking experiments results via several aspects, it was found that there were systematic deviations between the maglev gyroscope north seeking process and the theoretical model. It’s mainly reflected in the deviation of the trend term deviation and constant deviation related to the north seeking erection orientation. They don’t impact the stability of north seeking according to our analysis. The constant deviation impact the absolute north seeking accuracy, but it can be offset by data differential. Finally, the author believe that the maglev gyroscope north seeking data characteristics can be used as priori conditions of data filtering and elimination of gross error. It can also be used in the assessing precision of the gyroscope orientation.

The Application of the Improved Threshold Method in Wavelet Image De-Noising

The key of wavelet image threshold de-noising is the choice of the threshold function and the threshold value. To overcome the shortcomings of constant deviation existing between estimated wavelet coefficients and decomposition coefficients in the soft threshold function and discontinuity of the hard threshold function, a new threshold function based on wavelet shrinkage in image de-noising is presented in this paper. Threshold values of images with different edges and texture degrees are fine-tuned when the threshold value is set. Furthermore, a self-adaption optimal threshold which is fit to all scale levels is designed based on features of multiscale and multiresolution of wavelet transform. Simulation results show that the proposed methods are efficient to reduce the noise while preserving the detail information of the image.

An Improvement Based on Wavelet Transform Speech Denoising Threshold Function

The wavelet threshold denoising method is widely researched and used, the hard threshold and soft threshold which exist different advantages and disadvantages are two kinds commonly used threshold function; the threshold function was improved between hard threshold and soft threshold by using the exponential function. The smooth curve is monotonically increasing, no discontinuity and thus will not produce oscillation. Overcoming shortcomings that the hard threshold function and soft threshold function to be zero in wavelet coefficient is small and soft threshold exist constant deviation, and when the absolute value is greater than the threshold coefficient, soft threshold function is disposed with the same contraction method. After the simulation results prove that compared with traditional speech enhancement algorithms, the new threshold function has been improved to a certain extent.

Wavelet De-Noising Method Based on a New Kind of Threshold Function

Based on wavelet threshold de-noising method which put forward by Donoho, we analyze and compare the advantages and disadvantages of hard threshold, soft threshold and some improved threshold methods. Based on polynomial interpolation method, a new threshold function is proposed, which is continuous in the whole threshold area, with little constant deviation between the estimated wavelet coefficients and original signal wavelet coefficient, and high-order derivative and easy processing. The simulation results show that this method can give better optical effect, SNR gains and MSE performance.