Phase change materials (PCMs) are widely used in solar energy utilization, industrial waste heat recovery and building temperature regulation. However, there are few studies on the application of PCMs in...

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In this paper, a designated interleaved structure of constructing optimal frequency-hopping sequence (FHS) sets with low hit zone (LHZ) is presented based on the Cartesian product. By the general structure, we obtain infinitely many optimal LHZ FHS sets with new and flexible parameters by combining the optimal LHZ FHS sets with one-coincidence sequence sets. Moreover, our constructions remove the constraint requiring that the extension factor is co-prime with the length of the original FHSs. In this paper, most of the extension constructions suffer from this constraint. As a result, our constructions allow great flexibility of choosing parameters of the LHZ FHS sets for a given quasi-synchronization frequency-hopping spread spectrum system.INDEX TERMS Frequency hopping sequences, low hit zone, optimal Hamming correlation, extension construction. I. INTRODUCTIONIn frequency-hopping multiple access (FHMA) communication systems, the signal of each user hop over the entire transmission bandwidth in a pseudo random fashion. FHMA communication systems are widely adopted in practice [1], [2]. For example, many popular systems, such as military communications [3], ultra wideband communications [4], 5G communication systems [5], HetNets [6], and Bluetooth [7], use FHMA methods. In such systems each user is represented by a sequence of hopping frequencies [8]. Simultaneous transmission by any two users over the same frequency band results in collisions of signals, and hence, it is very desirable that such collisions over the same frequency band are minimized. Thus, the design of a frequency hopping sequence (FHS) set with good property is an important problem.Different from conventional FHS design, the design of FHSs with low hit zone (LHZ) aims at making Hamming correlation equal to a very low value within a correlation zone [9]. The significance of LHZ FHS set is that, even there The associate editor coordinating the review of this manuscript and approving it for publication was Zilong Liu.XIAN-HUA NIU received the B.S. degree in communication engineering and the Ph.D. degree in information security from

Test configuration is an important part in the process of testability design. Most of the existing test configuration methods are based on multi-signal flow diagram model and adopt genetic algorithm or particle swarm optimization (pso). However, there are many problems in this solution. First of all, the multi-signal flow diagram model has poor ability to express uncertain information, low model accuracy, large deviation in the calculation of testability indicators, and the model does not have the ability to learn and update. Secondly, the efficiency of genetic algorithm is low and the computation time is long, while the binary discrete particle swarm optimization algorithm is easy to fall into the local optimal. To solve the above two problems, a test configuration method based on the hybrid algorithm of genetic -binary discrete particle swarm optimization is proposed. This method can combine the global search ability of genetic algorithm with the optimal speed of binary particle swarm optimization, and use the bayesian network model to calculate more accurate testability indexes. It is proved that the algorithm can make full use of the high-precision information provided by the model, and the calculation speed is fast.And it is not easy to fall into the local optimal solution.