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Conventional double differential phase-shift keying modulation amplifies the phase noise and performs poorly under the time-varying direct-sequence spread-spectrum (DSSS) communication system. Therefore, the authors propose an iterative reception for DSSS communication in time-varying underwater acoustic channels. First, bit-interleaved coded modulation with iterative decoding integrated with multi-symbol differential detection is used. Second, this paper uses cross correlation method to estimate and track the Doppler shift of each symbol. Based on Doppler estimates, a dynamic linear prediction model is proposed to estimate and track the channel phase variation. Third, an algorithm for adaptive selection of reference signals is utilized to recover the magnitude attenuation of correlation peaks. Numerical simulation results demonstrate that the proposed reception achieves around 9 dB gain compared to conventional differential decision reception under constant acceleration of 0.14 [Formula: see text]. During the acoustic communication experiment in Songhua Lake, the proposed reception was tested by using a moving source at a speed of 1–6 knots at 2-m depth and the farthest distance between the transceivers is 2.8 km. The proposed reception achieves only one frame error from a total of 205 frames collected in the lake experiment, and it also achieves error-free communications over 96 frames during a 10 km depth deep-sea experiment.

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The difficulties in teaching and experiment of medical electronics lie in the abstract and difficult understanding of the teaching contents, the lack of a good single-chip microcomputer software teaching platform support, we must innovate experimental means, combined with the actual needs of medical instruments and a large number of qualified application-oriented talents. Aiming at the problems in the experimental teaching and scientific research of medical electronic circuits, this paper puts forward the design and simulation methods of electronic circuits for medical instruments by using Proteus as a tool, and finally forms a series of schemes which can be applied to experimental teaching and scientific research.

In this paper, an automatic assessment system has been developed for Putonghua articulation and pronunciation assessment. The framework of developing the system consists of designing the vocabularies respectively for the two assessment parts with standard scoring regulations, constructing the speech recognition module which makes use of a HMM based acoustic model with 39 parameters including logarithmic energy, the previous 12 MFCCs and their first and second difference extracted from the records of speech and the Speech SDK which is a developing kit from Microsoft to improve the accuracy, and building disorder diagnosis module according to the clinical requirement. In order to measure accuracy of this objective method, a comparative experiment is carried out with the subjective one, the results show that the two methods are almost the same and have a extremely correlation in both the articulation and pronunciation assessments.