The composite structure of a microperforated panel and porous metal is a promising sound absorber for industrial noise reduction, sound absorption performance of which can be improved through parameter optimization. A theoretical model is constructed for the composite structure of a microperforated panel and porous metal based on Maa’s theory and the Johnson–Champoux–Allard model. When the limited total thickness is 30 mm, 50 mm, and 100 mm respectively, dimensional optimization of structural parameters of the proposed composite structure is conducted for the optimal average sound absorption coefficient in the frequency range (2000 Hz, 6000 Hz) through a cuckoo search algorithm. Simulation models of the composite structures with optimal structural parameters are constructed based on the finite element method. Validations of the optimal composite structures are conducted based on the standing wave tube method. Comparative analysis of the theoretical data, simulation data, and experimental data validates feasibility and effectiveness of the parameter optimization. The optimal sandwich structure with an actual total thickness of 36.8 mm can obtain the average sound absorption coefficient of 97.65% in the frequency range (2000 Hz, 6000 Hz), which is favorable to promote practical application of the composite structures in the fields of sound absorption and noise reduction.

By the full use of the reconfigurability of SOPC, this paper constructed the hardware system of communication gateway, designed the logic of custom HDLC processor and SLIP processor. The application software systems are developed, which implemented efficiently the functions of communications gateway protocol parsing and conversion, data packet distribution and packaging etc.

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Digital wireless communications between a certain type of command vehicle and reconnaissance vehicle is an important communication way in such equipment, which includes digital cable mode, digital wireless mode and network communication, etc. It is known that digital cable and network communication have to be carried out by a covered wire connection in the process of communication, so it is perhaps feasible if two vehicles are close enough in relative static condition. However, it is impractical to pull and construct so long a covered wire for communication in real combat when the two vehicles maintains a far distance from each other, because if length of the wire is too long, the communication would break off once malfunction occurred in a whatever local part of wire. Moreover, it is very difficult for troubleshooting. At this time digital wireless communication is vital for battlefield communication between the two vehicles, and as long as we well define the default parameters before combat, then you can communicate directly during combat. Undoubtedly, the digital wireless communication has become the most important means of communication between such equipment. So we here provide an example of malfunction diagnosis and troubleshooting in such type of digital wireless communication equipment for basic technical officers.[1] 1 MALFUNCTIONPHENOMENON Open the command vehicle and the reconnaissance vehicle, operate a digital wireless communications network operation from initial step to final step to ensure that the process is definitely correct, and then get through the digital transmission and voice communication, but it comes out to find that both of communication ways fail and do not work at all. 2 MALFUNCTIONDIAGNOSIS The main connection structure for wireless communication between command vehicle and reconnaissance vehicle is shown in Fig.1. Fig. 1 schematic graph for connection between a certain type of command vehicle and reconnaissance vehicle