Correction to: Performance Analysis of Cooperative Spectrum Sensing Network Using Optimization Technique in Different Fading Channels

Wireless Personal Communications - In order to reduce the cost of logistics distribution, a capacitated open vehicle routing problem with split deliveries by order is studied. According to the...     

The effect of Weibull fading channel on cooperative spectrum sensing network using an improved energy detector

This paper analyses the performance of proposed cooperative spectrum sensing (CSS) network in Weibull fading environment. First, we have derived the novel analytic expressions for probabilities of missed detection and false alarm in Weibull fading channel, assuming an improved energy detector (IED), selection combining diversity scheme and multiple antennas at each cognitive radio (CRs). Next, performance is analyzed using complementary receiver operating characteristics curves, total error rate, average channel throughput, and network utility function curves for the proposed CSS network. The optimal performance of CSS network is achieved by optimizing the CSS network parameters. The closed form of expressions for the optimum value of number of CRs, arbitrary power of received signal, and detection threshold at each CR are derived using OR-Rule and AND-Rule at fusion center (FC). The average channel throughput and network utility function analysis are evaluated using \(k=1+n\) and \(k=N-n\) fusion rules at FC. Finally, the impact of several network parameters such as, multiple antennas at each CR (M), number of CRs (N) in CSS network, Weibull fading parameter (V), arbitrary power of received signal (p), and sensing channel SNR (\({\bar{\gamma }})\) on the performance of proposed CSS network are investigated using the simulation results. The performance comparison between conventional energy detector and an IED has been highlighted with the simulations.     

Microfibrous entrapped small particle adsorbents for high efficiency heterogeneous contacting

Hexane adsorption breakthrough tests on activated carbon particles (ACP) were used to demonstrate and understand the anomalous high efficiency of novel microstructured heterogeneous contacting systems: Microfibrous Entrapped Sorbents (MFES). MFES consist of small particles (0.05–0.30 mm) of adsorbent entrapped in micron-diameter fibers. They are characterized by small structural dimensions and uniform structures of high voidages. These materials are in the form of flexible sheets about 0.5–2.0 mm thick and can be conveniently stacked to create a required bed height. Experimental breakthrough curves were obtained from packed beds of various particle sizes (0.15–0.84 mm) and bed dilutions (with inerts) and microfibrous entrapped carbon particles (0.18–0.25 mm) of various void fractions (62.5–85%). The performance of the various bed configurations was evaluated based on their breakthrough times and percentage adsorbent utilizations. The rate of adsorption and hence the performance of packed beds improved with a decrease in particle size and also with an increase in bed dilution level. MFES clearly outperformed packed beds of similar particle size. A mathematical model accounting for axial molecular diffusion and intrabed flow maldistribution (or channeling) was used to explain these experimental results. In accordance with literature findings, the negative effect of the axial dispersion due to flow maldistributions on the transport rates in packed beds were evident in low Re regime (Re < 10). These shortcomings of packed beds were significantly minimized by high voidages and uniform flow distributions inherently present within MFES, thus leading to higher fluid–solid contacting efficiency.     

Prediction and Control of Internal Condensing Flows in the Experimental Context of their Inlet Condition Sensitivities

The reported experimental results involve fully condensing flows of pure FC-72 vapor on a horizontal condensing surface (316 stainless steel) which is the bottom surface (wall) of a rectangular cross-section duct of 2 mm height, 15 mm width, and 1 m length. The sides and top of the duct are made of clear plastic. The experimental system in which this condenser is used is able to control steady-in-the-mean (termed quasi-steady) mass flow rate, exit pressure, and wall cooling conditions. It has been found that, with the condenser mean (time averaged) inlet mass flow rate, exit pressure, and wall cooling condition held fixed at steady values, there is a very strong sensitivity to high amplitude pressure fluctuations and flow rate pulsations at the condenser inlet. This sensitivity often significantly alters the condenser mean inlet pressure, pressure drop, local heat transfer rates (>200% increase at certain locations), and the condensing flow morphology. These effects are representative of fluctuations/pulsations that are typically encountered in applications but are either not accounted for or are not detected. The effects of imposed fluctuations/pulsations, as opposed to cases involving negligible imposed fluctuations/pulsations, are dependent on the amplitude and the frequency content of the imposed fluctuations and this is discussed in a separate paper. A significant upstream annular regime portion of the reported shear/pressure driven fully condensing flows operate under conditions where the laboratory??s transverse gravity effects are negligible and, therefore, the identified sensitivity phenomenon is highly relevant to zero- or micro-gravity conditions. The micro-gravity relevance of this sensitivity for the annular regime phenomenon is currently also being demonstrated with the help of computations and simulations.     

Optimized cooperative spectrum sensing network analysis in nonfading and fading environments

The proposed cooperative spectrum sensing (CSS) network is equipped with multiple antennas and an improved energy detector (IED) scheme at each cognitive radio (CR). Each CR in the network receives the information about the primary user (PU) in the form of binary decisions at multiple antennas. Diversity technique called selection combining (SC) scheme is used at multiple antennas to select the maximum value of sensing information present at multiple antennas. Finally, sensing information will be passed to the fusion center (FC) through reporting channel, and the final decision about PU is made at FC using fusion rules. Initially, we have derived the novel missed detection probability expressions for AWGN channel, Rayleigh, and Rician fading environments. Later, the closed form of optimized expressions for proposed CSS network parameters are derived to achieve an optimal performance. The closed form of optimized expressions such as number of CR users (N_opt ), normalize threshold value (λ_n,opt ), and an arbitrary power of the received signal (p_opt ) are derived under various fading environments. The performance is evaluated using complementary receiver operating characteristics (CROC) and total error rate curves. The MATLAB‐based simulations are evaluated with the strong support of theoretical expressions. Finally, various simulation parameters such as sensing channel SNR, the error rate in reporting channel, threshold value, and number of antennas at each CR are considered in the simulation to show the effect on the performance of proposed CSS network.     

Event Detection and Information Passing Using LEACH Protocol in Wireless Sensor Networks

Wireless Personal Communications - Wireless Sensor Networks plays an important role in creating and developing smart environments. It includes sensors geographically distributed which are...     

Experimental results on gravity driven fully condensing flows in vertical tubes,their agreement with theory,and their differences with shear driven flows’ boundary-condition sensitivities

This paper synthesizes experimental results with computational results towards development of a reliable heat transfer correlation for gravity driven annular wavy condensing flows inside a vertical tube. For fully condensing flows of pure vapor (FC-72) inside a vertical cylindrical tube of 6.6 mm diameter and 0.7 m length, the experimental conditions are typically annular wavy and they cover: mass flux G over a range of 2.9 kg/m² s ? G ? 87.7 kg/m² s, temperature difference ΔT of 5–45 °C, and length of full condensation x_FC in the range of 0 < x_FC < 0.7 m.The range of flow conditions over which there is good (within 15%) and poor (15–30% or >30%) agreement with the theory and modeling assumptions are discussed and these conditions have been identified. The paper also refers to key experimental results with regard to sensitivity of the flow to time-varying or quasi-steady (i.e. steady-in-the-mean) impositions of pressure at both the inlet and the outlet.     

Comparative heterogeneous contacting efficiency in fixed bed reactors: Opportunities for new microstructured systems

Novel microstructured heterogeneous contacting systems called microfibrous entrapped catalysts (MFEC) were prepared by entrapping small particles of γ-alumina (150–180 μm) in sinter-locked network of metal (SS-304) microfibers (8 and 12 μm). These materials are in the form of thin flexible sheets (0.5–2.0 mm) and have uniform structures of high and variable voidages. Head-to-head theoretical comparisons of the performance efficiencies of flow-through pleated MFEC structures of various pleat factors (PF = face area of MFEC/cross-sectional area of the reactor) were made with packed bed reactors of various particle sizes (0.16–2.0 mm) and monolith reactors of various cpsi (100–900 cells per square inch). These comparisons showed that while packed beds produced high pressure drops, monoliths resulted in low fluid-solid mass transfer rates. On the other hand, MFEC structures with high PF (≥4) showed remarkable improvements in terms of conversion along with significant reduction in pressure drops and catalyst requirements compared to monoliths and packed beds. While small particles used in MFEC improved interphase and intraparticle mass transport rates, high voidages and ease of pleating helped lower the pressure drops in MFEC. To further ascertain these results, pleated structures of MFEC containing Pd/γ-alumina were tested for application in catalytic aircraft cabin air purification (ozone decomposition). Pressure drop and ozone conversion efficiency of pleated MFEC designs were measured at various flow rates and temperatures, and compared with those of a commercial monolith based ozone catalytic converter. The experimental results substantiated the mathematical findings.