Stability preservation analysis in direct discretization of fractional order transfer functions

In this paper, a class of the direct methods for discretization of fractional order transfer functions is studied in the sense of stability preservation. The stability boundary curve is exactly determined for these discretization methods. Having this boundary helps us to recognize whether the original system and its discretized model are the same in the sense of stability. Finally, some illustrative examples are presented to evaluate achievements of the paper.     

Breakdown probabilities for thin heterostructure avalanche photodiodes

The recurrence theory for the breakdown probability in avalanche photodiodes (APDs) is generalized to heterostructure APDs that may have multiple multiplication layers. The generalization addresses layer-boundary effects such as the initial energy of injected carriers as well as the layer-dependent profile of the dead space in the multiplication region. Reducing the width of the multiplication layer serves to both downshift and sharpen the breakdown probability curve as a function of the applied reverse-bias voltage. In structures where the injected carriers have an initial energy that is comparable to the ionization threshold energy, the transition from linear mode to Geiger-mode is more abrupt than in structures in which such initial energy is negligible. The theory is applied to two recently fabricated Al/sub 0.6/Ga/sub 0.4/As-GaAs heterostructure APDs and to other homostructure thin GaAs APDs and the predictions of the breakdown-voltage thresholds are verified.     

Network‐coded multiple‐source cooperation aided relaying for free‐space optical transmission

A network‐coded cooperative relaying aided free‐space optical (FSO) transmission scheme is designed. The resultant multiple‐source cooperation diversity is exploited by the relay to mitigate the strong turbulence‐induced fading experienced in FSO channels. At the destination, an iterative multiple source detection algorithm is proposed in conjunction with a chip‐level soft network decoding method. Our performance evaluation results using simulation analysis demonstrate that the proposed FSO multiple source detection is capable of approaching the single‐user‐bound for transmission over Gamma–Gamma turbulence channels. Also, the network‐coded cooperative FSO scheme can achieve a significant BER improvement in comparison with conventional noncooperation schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

An energy-aware distributed clustering protocol in wireless sensor networks using fuzzy logic

Clustering is an effective approach for organizing a network into a connected hierarchy, load balancing, and prolonging the network lifetime. On the other hand, fuzzy logic is capable of wisely blending different parameters. This paper proposes an energy-aware distributed dynamic clustering protocol (ECPF) which applies three techniques: (1) non-probabilistic cluster head (CH) elections, (2) fuzzy logic, and (3) on demand clustering. The remaining energy of the nodes is the primary parameter for electing tentative CHs via a non-probabilistic fashion. A non-probabilistic CH election is implemented by introducing a delay inversely proportional to the residual energy of each node. Therefore, tentative CHs are selected based on their remaining energy. In addition, fuzzy logic is employed to evaluate the fitness (cost) of a node in order to choose a final CH from the set of neighboring tentative CHs. On the other hand, every regular (non CH) node elects to connect to the CH with the least fuzzy cost in its neighborhood. Besides, in ECPF, CH elections are performed sporadically (in contrast to performing it every round). Simulation results demonstrate that our approach performs better than well known protocols (LEACH, HEED, and CHEF) in terms of extending network lifetime and saving energy.     

Design of efficient power amplifier for low power transmitters

This paper presents a fully integrated, low transmit-power and high-efficiency 2.4 GHz class-E power amplifier (PA) in TSMC 0.18 μm CMOS process for low-power transmitters such as wireless sensor networks (WSN). In this paper, a new output load has been proposed. Also, analytical design equations have been included to design an efficient low power circuit. This PA, employs the pad capacitance and bond-wire inductance of the output node, for satisfying class-E zero-voltage switching (ZVS) condition and matching the antenna’s 50 Ω resistance. By using bond-wire inductance instead of inductor in the output filter, smaller chip size and higher efficiency has been achieved compared to other works for low transmit-power applications. Also, the effectiveness of bulk-drive technique on faster switching and increasing efficiency have been evaluated. It has been proved that this technique leads to increase the efficiency of switching PAs. This PA delivers a range of output power from 2.7 to 7.2 dBm with a supply voltage range from 500 to 850 mV while achieving overall power efficiency range of 57.3–60.7%.     

Advent of 2D Rhenium Disulfide (ReS2): Fundamentals to Applications

Rhenium disulfide (ReS₂) is a two‐dimensional (2D) group VII transition metal dichalcogenide (TMD). It is attributed with structural and vibrational anisotropy, layer‐independent electrical and optical properties, and metal‐free magnetism properties. These properties are unusual compared with more widely used group VI‐TMDs, e.g., MoS₂, MoSe₂, WS₂ and WSe₂. Consequently, it has attracted significant interest in recent years and is now being used for a variety of applications including solid state electronics, catalysis, and, energy harvesting and energy storage. It is anticipated that ReS₂ has the potential to be equally used in parallel with isotropic TMDs from group VI for all known applications and beyond. Therefore, a review on ReS₂ is very timely. In this first review on ReS₂, we critically analyze the available synthesis procedures and their pros/cons, atomic structure and lattice symmetry, crystal structure, and growth mechanisms with an insight into the orientation and architecture of domain and grain boundaries, decoupling of structural and vibrational properties, anisotropic electrical, optical, and magnetic properties impacted by crystal imperfections, doping and adatoms adsorptions, and contemporary applications in different areas.