Spectrum sensing performance of wireless cognitive radio sensor network with hard-decision fusion over generalized α−μ fading channels

The analysis of spectrum sensing performance of energy detection (ED)-based wireless cognitive radio sensor network (ED-WCRSN) with hard-decision combining (HDC) is presented in this paper. Particularly, several network parameters are derived to estimate the performance of ED-WCRSN, considering channel errors, noise, and generalized $\alpha -\mu$ fading. In the considered network, first, cognitive radio sensor (CRS) senses a primary user (PU), gets sensing data, and then uses an ED to make a local binary decisions about PU's active or inactive status. In both sensing and reporting channels, the channel error probability is also taken into account. Next, HDC technique is used at control center (CC) to combine the locally obtained decisions, and a final decision about the status of the PU is made. To do so, first, the expression for the novel and analytical, which incorporates noise and $\alpha -\mu$ fading, detection probability in a CRS is derived and validated using Monte Carlo simulations in MATLAB and using an experimental setup. Then, utilizing derived mathematical expressions, closed-form expressions of an average error rate (AER), optimal numbers of CRSs, and detection thresholds under noisy and $\alpha -\mu$ fading conditions are developed. The substantial influence of channel and network factors is assessed using receiver operating characteristics (ROC), complementary ROC, and AER. Finally, the impacts of channel and network parameters on ED-WCRSN performance are explored. For numerous parameters of the considered network, the optimal values detection threshold and number of CRSs are also found.     

Hydrogen economy: hope or hype?

Clean Technologies and Environmental Policy -     

E-shaped patch with reactive impedance surface for high gain and broadband circularly polarized antenna

A low-profile circularly polarized (CP) antenna with high gain and broad bandwidth is aimed at 5-GHz Wi-Fi applications using a symmetrical E-shaped patch. Initially, the radiating element is modeled as a symmetrical E-shape. An array of 4 × 4 rectangular patches are arranged periodically to make up a reactive impedance surface (RIS) structure. Furthermore, the RIS structure is deployed in the middle of a symmetrical E-shaped radiating patch and a perfect electric conductor (PEC) ground plane. As a result, the broadband CP is achieved with high gain. The above-mentioned combinations have achieved a −10-dB reflection coefficient bandwidth of 21.4% (4.92–6.1 GHz) and a 3-dB axial ratio (AR) bandwidth of 15.5% (5.25–6.1 GHz), and the antenna has attained a gain of 7.45–7.53 dBic.     

Physical Insight into Self-heating Induced Performance Degradation in RingFET

Silicon - In nanoscale FETs, the confined geometry and increased packaging density induce increased power density, which translates into larger heat generation. The substrate’s low thermal...     

Influence of Process Parameters on Microstructure and Mechanical Properties ofAS21-SiC Composites through Two-Step Stir-Casting

Silicon - This work aims to focus on fine precipitation of Mg-Si compound in AS21 alloy system by the dispersion of SiC reinforcement through stir-casting in two steps. Dual step stir-casting at a...     

Effect of low thermal conductivity wick on the performance of compact loop heat pipe

The existing work deals with the evaluation of compact loop heat pipe by means of a low thermal conductivity sintered chrysotile wick to avoid large heat leaks as of the evaporator to the compensation chamber. Accordingly, a wick with low thermal conductivity (0.068–0.098 W/mK) chrysotile powder of a mean particle diameter of 3.4 μm is fabricated through sintering. Nine chrysotile wicks are sintered with different compositions of binders (bentonite and dextrin) and pore-forming agent NaCl at sintering temperatures of 500°C, 600°C, and 700°C with a sintering time of 30 min. The wick properties, for instance, porosity, permeability, wettability, and capillary rise are studied owing to sintering temperature. Consequently, it is observed that a pure chrysotile powdered wick at a sintering temperature of 600°C exhibits a high porosity of 61.8% with permeability 1.04 × 10⁻¹³ m² and a capillary rise of 4.5 cm in 30 s and is considered optimal. This optimal wick is used for performance evaluation in compact loop heat pipe and a decrease of 36.1% in thermal resistance is found when compared with copper mesh wick in a loop heat pipe. The lowermost thermal resistance originates to be 0.147 K/W at 120 W with wall temperature 57.7°C. This indicates that loop heat pipe with sintered chrysotile wick can operate at lower heat loads efficiently when compared with copper mesh wick and as heat load increases a chance of dry out condition occurs. The highest evaporative heat transfer coefficient obtained is 65.7 kW/m² K at a minimum heat load.     

3D-printed and foamed triply periodic minimal surface lattice structures for energy absorption applications

Structures currently used for energy absorption include foams, composites, and honeycombs. Recent studies have indicated the potential of triply periodic minimal surfaces (TPMS) for energy absorption applications as well as weight reduction. This study presents three TPMS lattice structures, namely the Gyroid, Fischer-Koch S, and PMY, which are fabricated in uniform and graded densities. These structures, created in the MSLattice software are 3D printed using polylactic acid. Subsequently, the 3D-printed structures undergo a gas foaming process to investigate benefits of higher porosity on energy absorption. The structures are then characterized for porosity, compressive properties, energy absorption, and thermal properties. The results show that the uniform and graded density structures have similar energy absorption values as long as the structures have a similar average density with the PMY structure exhibiting the highest energy absorption value, both in unfoamed and foamed conditions, respectively. The foaming process increased the porosity by 50% but did not improve the energy absorption characteristics of any of the structures with the foamed PMY structures exhibiting the least deviation compared to the unfoamed samples. These foamed TPMS structures are suitable for applications in the automotive and aerospace industry that demand lightweight structures for energy absorption.