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Cardiomyocytes are critically responsible for heart contraction and the pumping of blood through the circulatory system. In adult mice and humans, the rate of cardiomyocyte division is extremely low. In addition, dedicated cardiac stem cells that support myocardial renewal do not exist. Therefore, cardiomyocytes that are lost upon heart damage cannot be replenished. The inability to recover from cardiac injury, such as a myocardial infarction, is a leading cause of morbidity and mortality worldwide. Obviously, it is of great biomedical interest to find ways for enabling heart regeneration by restoration of lost cardiomyocytes. Previous reports have suggested that dedifferentiation of adult cardiomyocytes, which concurs with reactivation of fetal gene expression programs, is a prerequisite to enable adult cardiomyocytes to reenter the cell-cycle. Continuous forced expression of reprogramming factors known as OSKM (Oct4, Sox2, Klf4 and c-Myc) causes stepwise dedifferentiation of somatic cells and acquisition of pluripotency. More recently, it was shown that short-term OSKM-expression allows partial reprogramming of cells without the loss of cellular identity, improving the regenerative potential of tissues. The aim of this thesis was to investigate whether OSKM-expression in cardiomyocytes enforces cardiomyocyte dedifferentiation and proliferation, and to establish a cardiomyocyte-specific partial reprogramming strategy that might enable heart regeneration. To this end, two transgenic mouse lines designated i4FHeart and i4FHeart/mCherry were generated and analyzed in this study. These animal models allow control of OSKM expression specifically in fluorescently labelled cardiomyocytes. Here, it was found that OSKM-expression facilitates division of both neonatal and adult cardiomyocytes in vitro. Furthermore, cardiomyocyte-specific OSKM-expression results in dedifferentiation and enhanced proliferation of cardiomyocytes in neonatal, juvenile and adult hearts in vivo. Sustained OSKM-expression leads to complete cardiomyocyte reprogramming and heart tumor formation. Transient OSKM-expression in the adult heart dedifferentiates adult cardiomyocytes to fetal-like cardiomyocytes and allows subsequent reversion to the previous differentiated state. Transient OSKM-expression in juvenile mice enables heart regeneration after resection of the heart apex. In adult mice, transient OSKM-expression before and during myocardial infarction facilitates heart regeneration and ameliorates heart failure.

The theory of sampling method for measuring the mean parameters of quasi-periodic signal is analyzed, and the condition without introducing measurement errors is given. The reason of measuring error caused by non-synchronous sampling and the mechanism of window weighted method to suppress measurement error are analyzed. In particular, the analytical formulas of rectangular convolution window and measurement errors are given. Aiming at the DC component in the input signal of the practical analog-to-digital conversion (ADC) circuit, a series of formulas for parameter measurement of quasi-periodic signal in engineering implementation are derived.

In order to analyze soybean stalk using mechanics index, five kinds of soybean stalks were selected as experimental materials. The shear test and bending test were did by means of 1000N electronic universal testing machine. Loading position, loading velocity and moisture content were selected as experimental factor and the maximum loading force, stress and other mechanics indexs of the 5 kinds of soybean stalks in the shear test and bending test were measured. The relationship between mechanical properties of stalk and experimental factors were analyzed by statistical software and the function relationship were also be fitted using the software of matlab. The research results showed that the maximum shear force and bending force of stalk increased with the hight increase. The maximum shear force decreased with the increased of loading speed and moisture content. And the maximum bending force increased with the loading speed increased. But with the moisture content of the stalk increased, the maximum bending force increased first and then decreased. The research results can be used as theoretical fundation and reference to improve the soybean threshing and transport machine. It can also be used to confirm the best mechanical harvest time of soybean and other technological parameters.

In order to improve the screening effect of grain combine harvester, it is necessary to study the influence of different screening parameters on screening performance.In this paper, discrete element method was used to simulate the screening process of soybean and short stems by selecting different screening parameters, and dynamic screening efficiency and the number of short stems under screening were introduced as evaluation criteria.The results show that under certain other conditions, the vibration frequency, amplitude and direction angle have significant influence on the screening performance, while the inclination angle of the upper screen has little influence on the screening performance. With the increase of vibration frequency, amplitude and direction angle, screening efficiency increased first and then decreased, while the number of short stalks under screening increased first and then decreased. Considering the screening efficiency and the number of short stalks under the screening, it is concluded that the screening performance is better when the amplitude is 25 mm, the vibration frequency is 4 Hz, the vibration direction angle is 25 degrees and the upper screening angle is 3 degrees. The simulation results are verified by field experiments, and the simulation results meet the requirements of field experiments.

Successful operation of the Synchronous Overlap and Add (SOLA) algorithm for Time Scale Modification (TSM) of speech is closely tied to the proper choice of parameters. This paper investigates the quality of time scale modified speech under different values of primary parameters. Based on Mean Opinion Score (MOS) tests and Bark Spectral Distortion (BSD) measure, the proper choices of synthesis shift (Ss) and the duration of the shift search interval (Kmax ) are given experimentally. The conclusions can be helpful for operating the SOLA algorithm for time scale modification of speech.

Through traditional AMDF algorithm is easy to realize, it can easily make the estimated pitch doubled. Moreover, because of the pretreatments of making frames, the algorithm’s operation speed is limited. For higher accuracy and better real-time characteristics, based on the analysis of the dynamic change law of adjacent pitch periods, this paper proposes an adaptive pitch estimation algorithm based on AMDF. By calculating the average magnitude difference function based on adaptive search range, the new approach can easily estimate the continuous speech signals without flames. So the process of pitch detection is well simplified and the precision of estimated values is improved. Our simulation results verify that the algorithm presented outperforms three well-known pitch detection methods including the AMDF algorithm, the C-AMDF algorithm and the adaptive LV-AMDF algorithm in different SNR environments.

This paper examines the efficient quantization of LSP parameters for very low bit rate vocoder below 300 bps, a new quantization scheme called variable dimension matrix quantization (VDMQ) is presented. In the VDMQ scheme, the extracted LSP parameters matrix with variable dimension is quantized directly without dimension conversion. Based on the distance measure definition between tow LSP matrices with different dimension, the optimal codeword is deduced. Theoretical analysis and experiment results show that the VDMQ scheme performs better than the segment quantization and matrix quantization scheme at very low bit rate. Also, the codebook storage is almost reduced by 90%. The VDMQ scheme provides a new effective approach for efficient LSP parameters quantization at very low bit rate.

This paper analyzes the distortion of enhanced speech based on auditory perceptual properties. A speech enhancement criteria in the sense of minimum perceptual distortion called audible distortion criteria (ADC) is proposed, the gain function of short-time spectral amplitude is deduced then. Through rough estimation for the short-time power spectra and calculation of ADC gain function, a novel speech enhancement method is given. The proposed method can make a good compromise between reinforcing the noise suppression and reducing the speech distortion. It has lower computation complexity and is simple in implementation.

After analyzing the direct sampling algorithm for measuring a periodic signal's RMS value, a triangular window weighted algorithm is proposed for effectively reducing the synchronous error. Analytic formulas of measured RMS value as a function of the relative frequency deviation and initial sampling phase (or time) is derived. Both theory and numerical simulations show that the measurement error of the RMS value is proportional to the relative frequency deviation using the direct sampling algorithm, while it is proportional to the square of the relative frequency deviation using the proposed algorithm. Furthermore, the proposed algorithm is quite suitable for on-line implementation and the measured value responds rapidly to signal's variation. If the frequency deviation is far less than one, very high accurate measuring results can be achieved even if no synchronous sampling technique is introduced.

On the basis of the actions of a signal upon an ideal oscillator and an oscillator-array, the instantaneous energy density spectrum of a signal is defined. Furthermore, definitions of the instantaneous energy, the power density spectrum, the power, the total energy density spectrum and the total energy of a signal are introduced. Properties of power density spectrum and the relations between the power density spectrum and other physical quantities are presented. To meet the needs of real applications, an improvement method to the power density spectrum has also been mentioned.

Most algorithms for speech enhancement in the spectral domain focus on the acquisition of an estimator of the clean speech parameter, such as spectrum or amplitude. Enhanced speech quality with these methods mainly depends upon the accuracy of the estimator. When the signal-to-noise ratio (SNR) becomes lower, e.g., less than 3 dB, the enhanced speech often shows unsatisfactory quality. Here, we propose a new method for speech enhancement in the spectral domain. It is based on our view that speech characteristics are perceived mainly by part of the spectral components which have higher local (or instantaneous) SNRs. These components have a special importance on speech SNR enhancement and speech understanding. Identifying these components in the noisy spectrum with a decision system and constructing enhanced speech just by the same noisy amplitude and phase, the result is similar to those popular algorithms. All that is needed is a local SNR decision for each spectral component. The threshold for the decision is derived and two popular methods for local SNR (LSNR) estimation are suggested. It shows better performance under lower SNR signals. Though the number of these kind of spectral components varies with different signal SNR, any algorithms which can pick up more than 90% of it is sufficient to match any existing methods. Primary considerations and results are shown.