Analysis of Joint Multiband Sensing‐Time M‐QAM Signal Detection in Cognitive Radios

We analyze a wideband spectrum in a cognitive radio (CR) network by employing the optimal adaptive multiband sensing‐time joint detection framework. This framework detects a wideband M‐ary quadrature amplitude modulation (M‐QAM) primary signal over multiple nonoverlapping narrowband Gaussian channels, using the energy detection technique so as to maximize the throughput in CR networks while limiting interference with the primary network. The signal detection problem is formulated as an optimization problem to maximize the aggregate achievable secondary throughput capacity by jointly optimizing the sensing duration and individual detection thresholds under the overall interference imposed on the primary network. It is shown that the detection problems can be solved as convex optimization problems if certain practical constraints are applied. Simulation results show that the framework under consideration achieves much better performance for M‐QAM than for binary phase‐shift keying or any real modulation scheme.     

Single fiber colorless symmetric WDM-PON architecture using time interleaved remodulation technique for mitigating Rayleigh backscattering resilience

A time interleaved differential phase shift keying (DPSK) remodulation technique is proposed to mitigate the effect of Rayleigh backscattering (RBS)-induced noise in a single fiber colorless wavelength-division-multiplexing passive optical network (WDM-PON). In order to achieve a cost effective optical network unit (ONU) solution without dedicated laser sources for upstream signals to provide optimum symmetric capacity in a colorless WDM-PON, remodulation becomes the core attraction. Also as the performance of colorless WDM-PON systems suffers from the transmission impairments due to RBS, it is mitigated by using this remodulation scheme. Simulation results show that downstream and upstream signals achieve the error-free performance at 10 Gbit/s with negligible penalty, and enhance the tolerance to RBS-induced noise over a 25 km single-mode fiber.     

RECENT PROGRESS IN HYDRODYNAMICS OF INVERSE FLUIDIZED BED REACTORS: A REVIEW

Hydrodynamic characteristics of the inverse fluidized bed reactor such as phase holdup, pressure drop, minimum fluidization velocity, liquid circulation velocity, friction factor, bubble size and bubble rise velocity, and mass-transfer coefficient along with heat transfer studies, RTD studies, and the influence of these parameters on the extent of inverse fluidization are reviewed in this work. The importance of each of these is presented, and certain correlations developed on some hydrodynamic characteristics are provided. Our work has shown that the majority of investigations focused on phase holdup, pressure drop, and minimum fluidization velocity, and studies related to other characteristics such as friction factor, mass-transfer coefficient, and residence time distribution are generally scarce. This review also projects some of the areas on which future research work can concentrate.     

Aqueous processing of nickel spent catalyst for a value added product

Nickel was recovered from a fertilizer industry spent catalyst by leaching with nitric acid followed by nickel hydroxide precipitation. The optimization of temperature, initial acid concentration and particle size for leaching of the spent catalyst was done through 2³ factorial design. A maximum extraction of 91.9% was achieved at 90 °C, 1.5M HNO₃ and 62.5 μm particle size. Temperature and acid concentration showed positive effect, while particle size showed no effect. A regression equation was developed and employed to predict conditions for 100% extraction which were experimentally tested. Nickel hydroxide was electrochemically precipitated from the leach liquor and its maximum discharge capacity was found to be 155 mAh/g. A 3-stage counter current leaching circuit was designed to obtain a leach liquor of suitable pH. XRD characterization of the precipitated Ni(OH)₂ shows to consist of both α- and β-forms.     

State of the water in crosslinked sulfonated poly(ether ether ketone)

We investigated the material properties of different crosslinked sulfonated poly(aryl ether ketone) membranes, focusing on the effect of the degree of sulfonation and crosslinking density on the water uptake, the physical state of the water, and the pore size distribution within the membranes. We observed that the degree of sulfonation and, in particular, the ion‐exchange capacity (IEC) had less effect on the control of the extent of water absorbed than the crosslinking density of the membranes. Crosslinking also enabled the membranes to reach a higher water contents without losing mechanical integrity. Moreover, increasing the crosslinking density resulted in the presence of more bound water, without dissolution of the membrane. The crosslinked membranes had lower methanol permeability and electroosmotic drag values. Only at low IEC values and low water uptake in partially crystalline sulphonated poly(ether ether ketone), SPEEK could the presence of nanometer pores in the water‐equilibrated crosslinked membranes be confirmed by thermoporometry and the pore size distributions were then comparable to those reported for Nafion membranes. At higher IEC values, the water uptake was extremely high, up to 300%, and then the structure of the swollen membranes was more analogous to that of a dilute aqueous solution of the sulfonated polymer, and no nanopores were present. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Passive cooling techniques through reflective and radiative roofs in tropical houses in Southeast Asia: A literture review

Cooling is one of the major concerns in building tropical houses. This problem is exacerbated by the heat gain of the roof, which constitutes 70% of the total heat gain. The passive cooling technique is one of the innovative practices and technologies that provide buildings with comfortable conditions through natural means. Reflective and radiative processes are the methods used to decrease heat gain by facilitating the elimination of excess heat in a building's interior to maintain a comfortable environment. Given that the potential of these techniques vary from region to region, their application in the tropics should be examined. Exploring these approaches in detail allows us to rethink how to effectively adapt these techniques to overcome the build-up of heat in modern tropical houses in Southeast Asia. This study reviews the physical characteristics of these approaches to guide architects and building designers. Results indicate a great reduction in operational cost. However, the significant differences in the performance of colour and material properties should be considered, given that the selected approach strongly affects the required thermal conditions of a building.     

Regulation of Proteolytic Activity to Improve the Recovery of Macrobrachium rosenbergii Nodavirus Capsid Protein

The causative agent of white tail disease (WTD) in the giant freshwater prawn is Macrobrachium rosenbergii nodavirus (MrNV). The recombinant capsid protein (CP) of MrNV was previously expressed in Escherichia coli, and it self-assembled into icosahedral virus-like particles (VLPs) with a diameter of approximately 30 nm. Extensive studies on the MrNV CP VLPs have attracted widespread attention in their potential applications as biological nano-containers for targeted drug delivery and antigen display scaffolds for vaccine developments. Despite their advantageous features, the recombinant MrNV CP VLPs produced in E. coli are seriously affected by protease degradations, which significantly affect the yield and stability of the VLPs. Therefore, the aim of this study is to enhance the stability of MrNV CP by modulating the protease degradation activity. Edman degradation amino acid sequencing revealed that the proteolytic cleavage occurred at arginine 26 of the MrNV CP. The potential proteases responsible for the degradation were predicted in silico using the Peptidecutter, Expasy. To circumvent proteolysis, specific protease inhibitors (PMSF, AEBSF and E-64) were tested to reduce the degradation rates. Modulation of proteolytic activity demonstrated that a cysteine protease was responsible for the MrNV CP degradation. The addition of E-64, a cysteine protease inhibitor, remarkably improved the yield of MrNV CP by 2.3-fold compared to the control. This innovative approach generates an economical method to improve the scalability of MrNV CP VLPs using individual protease inhibitors, enabling the protein to retain their structural integrity and stability for prominent downstream applications including drug delivery and vaccine development.     

An optimized forwarding protocol for lifetime extension of wireless sensor networks

Optimized routing (from source to sink) in wireless sensor networks (WSN) constitutes one of the key design issues in prolonging the lifetime of battery‐limited sensor nodes. In this paper, we explore this optimization problem by considering different cost functions such as distance, remaining battery power, and link usage in selecting the next hop node among multiple candidates. Optimized selection is carried out through fuzzy inference system (FIS). Two differing algorithms are presented, namely optimized forwarding by fuzzy inference systems (OFFIS), and two‐layer OFFIS (2L‐OFFIS), that have been developed for flat and hierarchical networks, respectively. The proposed algorithms are compared with popular routing protocols that are considered as the closest counterparts such as minimum transmit energy (MTE) and low energy adaptive clustering hierarchy (LEACH). Simulation results demonstrate the superiority of the proposed algorithms in extending the WSN lifetime. Copyright © 2008 John Wiley & Sons, Ltd.