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In a Mobile Ad-Hoc Network (MANET), the optimal placement and movement of relay UAVs and the performance of the relay network are all closely related to the propagation and coverage area of the relay signals. In this paper, on the basis of the geometric model of the relay link and relay signal coverage area, synthetically considering the impact of the propagation path loss, the multipath fading and the shadow fading, we study the coverage area of the relay signals by applying a statistical model based on the coverage of outage probability. The simulation results show that the channel fading has big effects on the radius of coverage area, and the radius of coverage area will increase rapidly with the increase of the outage probability. The results provides valuable recommendations for the placement, the movement strategy and network performance evaluation in the MANET.

The two kinds of composites, including nano-nitrile butadiene rubber (NBR)/epoxy resin (EP) and nano-acrylate/EP composites were prepared with the three-roll mill. The effect of nano-particles on the mechanical property of epoxy resin composites were investigated by tensile strength testing. SEM images were taken to characterize the decentralization of the nano-particles in the composites. Mechanical testing results were presented that the epoxy nano-composites has the higher tensile strengths after filling with nano-particles. The tensile strength of EP composites has been significantly improved with nano-NBR content 4 wt. % and the nano-acrylate content 3 wt. %, respectively. SEM results indicated that nano-particles can be evenly dispersed in the epoxy resin by the three-roll mill dispersion method.

PurposeAccording to the fact that the single function transformation which can both reduce the class ratio dispersion and keep the relative error no enlargement after the inverse transformation does not exist, this paper provides the separable binary function transformation F(x(k),k)=f(x(k))⋅g(k). The authors select the appropriate f(x(k)) and g(k) to get F(x(k),k)=f(x(k))⋅g(k). The sequence {F(x(k),k)}k=1n can not only improve the modeling accuracy but also ensure that the inverse transformation relative error has no enlargement.Design/methodology/approachFirst of all, to meet that the sequence reduces the class ratio dispersion after binary function transformation, the sufficient and necessary condition of binary function transformation with reduced class ratio dispersion is obtained. Secondly, to meet the condition that the inverse transformation relative error is not enlarged, the necessary condition of separable binary function transformation is obtained respectively for monotonically increasing and monotonically decreasing function f(x). Finally, the feasibility and correctness of this method are illustrated by example analysis and application.FindingsThe sufficient and necessary condition of binary function transformation with reduced class ratio dispersion and the necessary condition of separable binary function transformation with the inverse transformation relative error no enlargement.Practical implicationsAccording to the properties of separable binary function transformation provided in this paper, the grey prediction function model is established, which can improve the modeling accuracy.Originality/valueThis paper provides a binary function transformation, and researches the sufficient and necessary condition of binary function transformation with reduced class ratio dispersion and the necessary condition of separable binary function transformation with the inverse transformation relative error no enlargement. It is easy for scholars to carry out the pretest before selecting the separable binary function transformation. The binary function transformation is the further extension of single function transformation, which broadens and enriches the choice of function transformation.

Ecological agriculture is increasingly relying on mobile technologies to monitor the growth of plants, however, the traditional management efficiency is low and waste resources. So, a USB coordinator based on ZigBee-Stack is designed. ZigBee is a low rate, low power consumption wireless communication technology, which can be commonly used in Wireless Sensor Network (WSN). WSN is composed of hundreds sensor nodes, all of the information from these nodes will be sent to the coordinator, so the coordinator undertakes the task to collect and process data information, and also as the interface of the network with users. The design of the coordinator is based on CC2530 chip, and RFX2401C chip is superposed on it. A software was compiled to test the data transmission distance. The results show that the distance was increased by 40-60 meters and RFX2401C chip uses only two pins of CC2530 chip. So the improved coordinator is more cost-savings and efficient.