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When there exist certain kinds of matching in an electric system between the nonlinear input and noise, amplifying the input noise may dramatically increase the output SNR other than decrease it. And stochastic resonance is a phenomenon that when noise is input at certain amplitude the output SNR reaches its peak. Generalized stochastic resonance is the kind of nonlinear phenomena that the output (output SNR, output mean value, etc.) is a non-monotonic function of some parameter of noise (amplitude, correlation time) or input (amplitude, frequency). We studied the phenomenon of stochastic resonance in linear models with random parameters. And we discovered that the output amplitude is a non-monotonic function of the noise amplitude, the noise correlation time and the system parameters. The result will be a helpful complement to both the traditional linear system theory and the analysis of RL circuit.

Stochastic resonance is a non-linear phenomenon where the output response of the dynamic system reaches the maximum value under the joint action of a certain intensity of noises and external incentives. In this paper, the phenomenon of stochastic resonance in a FitzHugh-Nagumo neural (FHN) model is studied. For the case that the frequency of the HF signal is much higher than that of the LF signal, under the adiabatic approximation condition, the expression of the signal-to-noise ratio (SNR) with respect to the LF signal is obtained. It is shown that, the SNR is a non-monotonous function of the amplitude and frequency of the HF signal. In addition, the SNR varies non-monotonically with increasing the intensities of the multiplicative and additive noise, with increasing the delayed-time as well as increasing the system parameters of the FHN model. The influence of the correlation time of the colored multiplicative noise and the influence of the coupling strength between the multiplicative and additive noise on the SNR is discussed.

this paper introduces an output method of arbitrary waveform signal on the FPGA by uses DDS principle. Arbitrary waveform dates produced by the upper machine are downloaded to the waveform RAM of the DDS through the serial port, and realize the control of frequency and phase by using single-chip microcomputer. The upper machine with using LabWindows/CVI software design, realizes arbitrary waveform output.

The basic approach of generating arbitrary waveform is the digital synthesis method. Appling this method, one first samples and quantifies a period of the signal waveform to be generized, memorizes the obtained binary waveform data in a memory, and then reads it via hardware circuit in certain sequence, converts the data via digital-to-analog (DA) circuit, finally output the analog waveform through a filter. In this work, an arbitrary waveform generator (AWG) is designed based on the theory of direct digital synthesis (DDS)[1-7]and on the analysis of the performance of the output signal. The design uses a field programmable-gate-array (FPGA)[3]chip to utilize the AWG. The preset and display of the output frequency and phase are controlled by a micro computer unit (MCU). The artribary waveform data can be downloaded and updated from a communication interface. The AWG can produce a high-resolution arbitrary waveform. The dissertation focuses on hardware circuit design, which has been accomplished, including power supply module, MCU system, high-speed DA converter, and filter, etc. The experimental prototype of the AWG has been made and tested systemly.At the end of the dissertation, the measurement result of the system is given and its error is analyzed. It is shown the AWG can output a sine wave, a triangle wave, a sawteeth wave, or a square wave within the frequency range from 0.01Hz to 15MHz with the step of 10mHz, or output an arbitrary waveform within the range from 0.01Hz to 20kHz.

Based on the analysis and the induction of electronic control fuel injection engine common failure which can't start, and according to the engine’s working principle and failure mechanism, established the electronic control fuel injection engine’s fault tree, and having made qualitative analysis about the working reliability of the engine by using the fault tree analysis method. This paper offered the electronic control fuel injection engine’s failure form which can’t start in classification, discussed the process of establishing the fault tree at length, even built and mapped the engine’s fault tree which can’t start; According to the natural gas compressor’s fault tree diagram, and applying the descending method to get the fault’s minimal cut sets. By making qualitative analysis, finding out the main influence factors of failure, and putting forward quite perfect methods of removing fault, which providing electronic fuel injection engine maintenance with the beneficial reference.