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To the existing spectrum sharing schemes in wireless-powered cognitive wireless sensor networks, the protocols are limited to either separate the primary and the secondary transmission or allow the secondary user to transmit signals in a time slot when it forwards the primary signal. In order to address this limitation, a novel cooperative spectrum sharing scheme is proposed, where the secondary transmission is multiplexed with both the primary transmission and the relay transmission. Specifically, the process of transmission is on a three-phase time-switching relaying basis. In the first phase, a cognitive sensor node SU1 scavenges energy from the primary transmission. In the second phase, another sensor node SU2 and primary transmitter simultaneously transmit signals to the SU1. In the third phase, the node SU1 can assist the primary transmission to acquire the opportunity of spectrum sharing. Joint decoding and interference cancellation technique is adopted at the receivers to retrieve the desired signals. We further derive the closed-form expressions for the outage probabilities of both the primary and secondary systems. Moreover, we address optimization of energy harvesting duration and power allocation coefficient strategy under performance criteria. An effective algorithm is then presented to solve the optimization problem. Simulation results demonstrate that with the optimized solutions, the sensor nodes with the proposed cooperative spectrum sharing scheme can utilize the spectrum in a more efficient manner without deteriorating the performance of the primary transmission, as compared with the existing one-directional scheme in the literature.

In this paper, the fourth in a series documenting palynological characters across angiosperms using a contemporary phylogenetic framework, we deal with the basal eudicots, a group which includes Buxales, Proteales, Ranunculales, Sabiaceae, and Trochodendrales. Using available molecular sequences of matK and rbcL from previous studies, we reconstructed a maximum likelihood tree for a total of 196 genera (including nine outgroups), representing 13 families and all four orders of basal eudicots. Across the 196 genera, 20 pollen characters were documented from prior publications and new observations. These were coded using two strategies and optimized onto the reconstructed phylogenetic tree using Fitch parsimony, maximum likelihood, and hierarchical Bayesian inference to infer ancestral states. Pollen samples of 24 species from 24 genera in eight families were imaged under LM and SEM to illustrate the diversity of basal eudicot pollen. In addition, we tested for correlated evolution between plant growth form and pollen shape class, and between anemophily and pollen aperture number, using maximum likelihood and Markov chain Monte Carlo analyses. Basal eudicot pollen showed high morphological diversity, especially in characters including tectum sculpture, aperture number, and ectoaperture shape. Depending upon the method of reconstruction, 14 to 18 plesiomorphic palynological states were unequivocally inferred, and a total number of 357 character state transitions were found at or above tribal level. These provide palynological support for at least 58 of the clades discovered by molecular phylogenetic estimation. For example, using hierarchical Bayesian inference with comprehensive data coding, 222 state changes were inferred. Pollen size, tectum sculpture, and pollen shape class changed the most frequently among the 20 studied characters. The most concentrated character state changes in basal eudicot pollen are estimated to have occurred around the Barremian to Albian stages of the Early Cretaceous. Tests of correlated evolution suggest that the herbaceous growth form is significantly associated with spheroidal pollen shape and the arborescent growth form with oblate pollen shape. However, no significant correlations were found between anemophily and aperture number. Patterns of evolutionary change in pollen size and tectum sculpture, and their adaptive functions, are discussed. Based on previous evidence and our data, pollination syndrome is the most likely factor associated with the high frequency of state changes in these two characters.

The free-electron relaxation time is a crucial property to be considered in the design of optical devices, because it determines the dielectric function. Thus, an accurate understanding of this relaxation time is essential for design optimization. Some simulations showed that the relaxation times of Au thin films with thicknesses below 30 nm are different from those of the bulk material. Therefore, we deposited films with four different thicknesses below this value and used near-infrared spectroscopic ellipsometry to show that the relaxation time is dependent on the film thickness. We fitted the ellipsometry spectrum of Au thin films with a thickness