Asymptotically optimum detection of primary user in cognitive radio networks

Traditionally, the frequency spectrum is licensed to users by government agencies in a fixed manner where the licensee has exclusive right to access the allocated band. However, with increasing demand for the spectrum and scarcity of vacant bands, a spectrum policy reform seems inevitable. Meanwhile, recent measurements suggest the possibility of sharing spectrum among different parties subject to interference-protection constraints. In order to enable access to an unused licensed spectrum, a secondary user has to monitor licensed bands and opportunistically transmit whenever no primary signal is detected. Spectrum-sharing between a primary licensee and a group of secondary users has been studied. The structure of an asymptotically optimum detector based on the measurements of all secondary users is derived and the effect of the quantisation error in such a system is evaluated. Also, it is shown that by using the proposed detector in a sequential detection structure, it is possible to shorten the decision time needed by the detector. The results show the superiority of the proposed detector to other schemes.     

Optimizing the Runoff Estimation with HEC-HMS Model Using Spatial Evapotranspiration by the SEBS Model

Most of the commonly used hydrological models do not account for the actual evapotranspiration (ETa) as a key contributor to water loss in semi-arid/arid regions. In this study, the HEC-HMS (Hydrologic Engineering Center Hydrologic Modeling System) model was calibrated, modified, and its performance in simulating runoff resulting from short-duration rainfall events was evaluated. The model modifications included integrating spatially distributed ETa, calculated using the surface energy balance system (SEBS), into the model. Evaluating the model’s performance in simulating runoff showed that the default HEC-HMS model underestimated the runoff with root mean squared error (RMSE) of 0.14 m³/s (R²?=?0.92) while incorporating SEBS ETa into the model reduced RMSE to 0.01 m³/s (R²?=?0.99). The integration of HECHMS and SEBS resulted in smaller and more realistic latent heat flux estimates translated into a lower water loss rate and a higher magnitude of runoff simulated by the HECHMS model. The difference between runoff simulations using the default and modified model translated into an average of 95,000 m³ runoff per rainfall event (equal to seasonal water requirement of ten-hectare winter wheat) that could be planned and triggered for agricultural purposes, flood harvesting, and groundwater recharge in the region. The effect of ETa on the simulated runoff volume is expected to be more pronounced during high evaporative demand periods, longer rainfall events, and larger catchments. The outcome of this study signifies the importance of implementing accurate estimates of evapotranspiration into a hydrological model.

     

Modeling of Hydrogen Permeation through Pd Membrane on Ceramic Supports Activated via Pd Nanoparticles–TiO2–Bohemite Suspension

Theoretical Foundations of Chemical Engineering - Thin dense Pd composite membrane was prepared via electroless plating method. Pd nanoparticles embedded polyethylene glycol (PEG) was used in...     

Investigation of Creep Feed Grinding Parameters and Heat treatment Effects on the Nickel-base Superalloys

The Nickel base Superalloys are the most famous complicated and useable of Superalloys to make hot zone components of the gas turbines. The complicated dimensional tolerances, specially at the root of the blade show importance of grinding processes at the production of blades root. The prediction of the effect of machining parameters on the soundness of component surface strengthening for reaching to a suitable surface finishing and avoiding from crack formation at the work part during machining operation often is not easy and feasible so needs to more industrial investigation.This research is about frame 5 blade designed by GE and made from Superalloy IN738LC has been investigated. The formation of a plastically deformed and heat affected zone during grinding of Superalloy IN738LC with a high depth of cut but slow work speed (creep feed grinding) was investigated. Parameters such as work speed, depth of cut and radial dressing speed have been considered as variables and their effects have been studied. During experimental performed, the voltage and current of motor measured and power and special energy calculated.Some samples heat-treated (of the 1176℃ for 1 hr under neutral argon gas and cooling rate of 15℃/min up to 537℃ and then air cooling) to study grains recrystallization. Other samples have been created from the roots of blades and then coated by Nickel to measure boundary layer micro-hardness. The results show that increasing work speed leads to increasing the use power. Increasing the depth of cut, by increasing material removal rate, and the radial dressing speed, by decreasing power, lead to decreasing special energy. The temperature created by grinding lead to decreasing plastic deformation and boundary layer formation. When the radial dressing speed changes from 1 to 0.6μm/rev and other parameters are kept unchanged the roughness of surface increases and the special energy decreases. Sufficient dressing is very essential in limiting the width of the molten zone to few micrometers. As a result, it was found that local melting at contact spots to be a rather common mechanism during grinding of superalloys, lead to so-called white layers which can easily be observed on metallographic cross sections.     

Operational Regimes and Physics Present in Optoelectronic Tweezers

Optoelectronic tweezers (OET) are a powerful light-based technique for the manipulation of micro- and nanoscopic particles. In addition to an optically patterned dielectrophoresis (DEP) force, other light-induced electrokinetic and thermal effects occur in the OET device. In this paper, we present a comprehensive theoretical and experimental investigation of various fluidic, optical, and electrical effects present during OET operation. These effects include DEP, light-induced ac electroosmosis, electrothermal flow, and buoyancy-driven flow. We present finite-element modeling of these effects to establish the dominant mode for a given set of device parameters and bias conditions. These results are confirmed experimentally and present a comprehensive outline of the operational regimes of the OET device.     

Performance of Pd composite membrane prepared by organic–inorganic method in WGS membrane reactor

H₂ production via water–gas shift (WGS) reaction in a Pd membrane reactor prepared by the electroless plating technique (ELP) “organic–inorganic” method was investigated. Pd nanoparticles embedded polyethylene glycol (PEG) was used as a polymer template during the activation step. Gas permeation results showed an infinite selectivity for H₂/N₂ with a H₂ flux of 0.004–0.016 mol/m²·s depending on operating conditions while it decreased until 0.0005 mol/m²·s for gas mixtures. Furthermore, WGS membrane reactor experiments showed a maximum CO conversion of 98.5% with a H₂ recovery of 16% at 450°C. The membrane performance was consistent during WGS catalytic membrane reactors (CMR) tests, thereby confirming the stability of the obtained membrane.     

A new predictor parameter for production rate of ornamental stones

Bulletin of Engineering Geology and the Environment - In this study, a new predictor parameter (NPP), which is based on the product of uniaxial compressive strength (UCS) and Mohs hardness (MH),...     

Using Fuzzy Cost‐Based FMEA,GRA and Profitability Theory for Minimizing Failures at a Healthcare Diagnosis Service

This paper proposes an integrated approach to identify, evaluate and improve the potential failures in a service setting. This integrated approach combines Fuzzy cost‐based service‐specific FMEA (FCS‐FMEA), Grey Relational Analysis (GRA) and profitability theory for better prioritization of the service failures by considering cost as an important issue and using the profitability theory in a way that the corrective actions costs are taken into account. Considering profitability with FCS‐FMEA and GRA reduces the losses caused by failure occurrence. Besides, a maximization linear mathematical problem is used to select the best mix of failures to be repaired. We apply our approach to an academic example concerning the potential failures diagnosis of the Internal Medicine service of a hospital located in Seoul, Korea. We applied our approach and solved the associated maximization problem by a commercial solver, producing an optimal solution which indicates the most convenient mix of failures to be repaired by considering available budget. Copyright © 2013 John Wiley & Sons, Ltd.     

Potency of Different Carbon Sources in Reduction of Microsilica to Synthesize SiC from Mechanically Activated Powder Mixtures

In the present study, the influences of three different types of carbon (carbon black, graphite, and petroleum coke) on SiC synthesis via mechanical activation and sintering were evaluated. In this regard, the phase components, morphology, and the formation mechanism were investigated. SiC nanoparticles were detected to be formed after 4 h of milling and sintering at 1450°C, regardless of the sources of carbon. The carbon types exert their effects on the morphology of the as‐synthesized particles, where carbon black leads to form rod‐like SiC particles and the other two carbon types result in semi‐spherical SiC particles. This is due to the dominant mechanism in the mentioned process. The rod‐like particles obtained from the carbon black‐containing powder were synthesized via the VSL mechanism, whereas the solid‐state reactions occurred to form the SiC particles in the graphite‐ or petroleum coke‐containing samples. In the VSL mechanism, any increase in the milling time leads to facilitate the SiC formation due to entrance of Fe debris, whereas in the other samples (graphite or petroleum coke) the procedure is reversed.     

Electropolymerization and characterization of polyaniline, poly(2-anilinoethanol) and poly(aniline-co-2-anilinoethanol)

Applications of conducting polymers to biosensors have recently aroused much interest. This is because these molecular electronic materials offer control of different parameters such as polymer layer thickness, electrical properties and bio-reagent loading, diversity, ease of fabrication and potentially low cost, etc. Polyaniline, poly(2-anilinoethanol) and poly(aniline-co-2-anilinoethanol) preparations are performed with electrochemical (CV) method at room temperature, in a standard three-electrode cell. Homopolymer and the copolymers of aniline and 2-anilinoethanol films were deposited from 1?M acidic aqueous media containing 0.2?M aniline, 2-anilinoethanol by voltammetric sweep between ?0.1 and 1 V Ag/AgCl, at 20?mV/s^?1. The sweep was stopped after 30 cycles at ?0.1?V Ag/AgCl and the working electrode was covered by homopolymer and copolymer of aniline and 2-anilinoethanol. Characterizations of the products were carried out by cyclic voltammograms, UV?Cvisible, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance (EIS) was employed to examine the water absorption of the synthesized polymers to be used in biosensor application. Electrochemical properties of polyaniline, poly(2-anilinoethanol) and poly(aniline-co-2-anilinoethanol) were studied and it is shown that with increased (2-anilinoethanol) content in the copolymer, its electroactivity, conductivity and resistance are reduced, though the processability and adhesion properties improve. The hydrophilicity of polymer film obtained has increased with increasing (2-anilinoethanol) content which leads to salt moving to the surface of steel.