Stable‐path multi‐channel routing with extended level channel assignment

Wireless mesh networks (WMNs) have gained considerable popularity in recent times thanks to their self‐healing, self‐organizing, and self‐configuring nature. Because of their ability to provide high throughput and minimum packet delay, WMNs are considered to be favorable for broadband applications. For such applications, WMNs employ multiple channels, which give rise to issues like channel assignment, load balancing, and interference avoidance. Most of these issues fall into two broad categories, namely routing and channel assignment. For routing, we propose a novel proactive protocol, the stable‐path multi‐channel routing protocol (SMRP). Our proposed solution, to address channel assignment, is the extended level‐based channel assignment (ELCA) scheme. SMRP is designed to work in combination with ELCA in order to minimize interference and balance the load among the underlying nodes. Simulation results show enhanced throughput and minimal packet delay as compared with the contemporary schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

Toward Distributed Robust Power Allocation of Wireless Backhaul Links in Vehicular Small Cells

The vehicular small cell (VSC) is a new paradigm that has been recently proposed to be a potential technology for 5G cellular systems. Briefly, VSC concept lies in using the small cell technology inside vehicles such as buses and private cars to provide better coverage and good internet experience while on the move where the wireless backhaul link is inevitable. However, in order to increase the spectral efficiency, co-channel deployment of VSCs on the wireless backhaul link is preferred. Thus, managing the variable interference on the wireless backhaul and its power allocation requirement seem to be serious challenges in implementing the VSCs. Motivated by the simplicity and practically of the power allocation based on pilot power and received signal strength index (RSSI) information, this paper proposes an evolutionary approach and robust to the interference fluctuations in which, taking the limited dynamic range of transmitted power using linear mapping into account, the signal to interference plus noise ratio (SINR) balancing of the vehicular small base stations in their home macro base station and maximum capacity on the backhaul link are achieved at the cost of exchanging some power level information among both macro and small base stations. Finally, simulation results prove aforementioned potential advantages attained from the presented schemes.     

Network selection in heterogeneous access networks simultaneously satisfying user profile and QoS

Multimode capability empowers mobile devices to select the appropriate network to meet the requirements of user and applications. However, network selection is a challenging task owing to heterogeneous nature of network access links. At the same time, pervasiveness of mobile communication networks accompanied by the advances in wireless devices has raised the user expectations of persistent service and quality. Therefore, it is important for a mobile device to take situation‐based and timely decisions while selecting an access network to ensure both user's and operator's demand. The existing standard, called IEEE 802.21 (media‐independent handover), considers mobile device signal‐strength parameter for network selection from a list of networks. This research has proposed a ranking algorithm to rank heterogeneous networks based on a set of parameters including user profile and QoS. It selects most suitable network owing to multiple handover scenarios. The simulation results have shown that the proposed scheme has successfully satisfied apparently the contradictory requirements related to user profiles and QoS simultaneously.     

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO2−x-Based Heterojunctions

Critical catalysis studies often lack elucidation of the mechanistic role of defect equilibria in solid solubility and charge compensation. This approach is applied to interpret the physicochemical properties and catalytic performance of a free-standing 2D–3D CeO_2−x scaffold, which is comprised of holey 2D nanosheets, and its heterojunctions with MoO_3−x and RuO₂. The band gap alignment and structural defects are engineered using density functional theory (DFT) simulations and atomic characterization. Further, the heterojunctions are used in hydrogen evolution reaction (HER) and catalytic ozonation applications, and the impacts of the metal oxide heteroatoms are analyzed. A key outcome is that the principal regulator of the ozonation performance is not oxygen vacancies but the concentration of Ce³⁺ and Ce vacancies. Cation vacancy defects are measured to be as high as 8.1 at% for Ru-CeO_2−x. The homogeneous distribution of chemisorbed, Mo-oxide, heterojunction nanoparticles on the CeO_2−x holey nanosheets facilitates intervalence charge transfer, resulting in the dominant effect and resultant ≈50% decrease in overpotential for HER. The heterojunctions are tested for aqueous-catalytic ozonation of salicylic acid, revealing excellent catalytic performance from Mo doping despite the adverse impact of Ce vacancies. The present study highlights the use of defect engineering to leverage experimental and DFT results for band alignment.     

Nd:YAG-pumped periodically poled LiNbO3 optical parametric generator seeded with the narrowband output of a 532-nm pumped optical parametric generator

We present a simple scheme to generate a continuously tunable pulsed narrow-bandwidth infrared wave. An Nd:YAG-pumped periodically poled lithium niobate optical parametric generator (OPG) is seeded with the output of another OPG pumped by the second harmonic (0.532 microm) of the Nd:YAG laser. A tunable idler wave from the 0.532-microm pumped OPG, operated away from the degenerate point, provides a narrow linewidth seed source for the 1.064-microm pumped broadband OPG. Seeding forces the second OPG to operate in a narrowband operation comparable with that of the seed source. Linewidth of the YAG-pumped OPG is 5-25 nm, in the tuning range of 1.61-1.83 microm (signal), narrowed to 1.48-1.05 nm. Methods of further reduction of linewidth also have been discussed.     

A new frequency compensation technique for three stages OTA by differential feedback path

A new single Miller capacitor for frequency compensation of three‐stage amplifier is proposed in this paper. In this scheme, a differential stage in which its negative and positive inputs are connected to the output and input nodes of third stage with a cascade capacitor forms the compensation block of a conventional three‐stage amplifier. Analysis shows that this configuration significantly improves the frequency domain performances of total circuit such as phase margin (PM) and gain‐bandwidth product (GBW) with just a very small amount of compensation capacitor. A three‐stage amplifier has been simulated with and without a differential feedback path in a 0.18 µm complementary metal–oxide–semiconductor (CMOS). The simulated amplifier with a 100 pF capacitive load achieved more than 9 MHz GBW and 83° PM while the compensation is less than 0.2% of load capacitor. An amplifier based on conventional nested Miller compensation can just achieve less than 0.23 MHz GBW with the same load, while using more than 100 pF as compensation capacitor. So this method shows an improvement of a factor of 40 in GBW and reduction of a factor of 550 in the size of compensation capacitor. It is a suitable strategy for ON‐CHIP compensation in comparison to other methods. Copyright © 2014 John Wiley & Sons, Ltd.     

A Fully Programmable Analog CMOS Rational-Powered Membership Function Generator with Continuously Adjustable High Precision Parameters

This paper presents a novel structure for implementing rational-powered membership functions (RPMFs), which are the extended forms of triangular/trapezoidal membership functions and those functions which are generated by applying linguistic hedges. The hardware realization of an RPMF consists of a triangular membership function generator circuit followed by a rational-powered generator module (RPGM). A novel fully programmable compact triangular/trapezoidal/s-shaped/z-shaped membership function generator with the ability to continuously change parameters is presented which is compatible with the proposed RPGM. A new method is introduced to implement the RPGM based on the approximation of the function “x ^a ” by the functions square and square-rooter which are simply implemented in a current-mode analog approach based on the translinear principle, which leads to a design that is simple, and has high accuracy and less hardware usage, with a resulting lower chip area and lower power consumption. The designed circuit was simulated by an HSPICE simulator with level 49 parameters (BSIM3v3), and the simulation results show that the maximum power consumption of the RPGM is 800 μW, while the maximum RMS error is 1.25 %. Finally, layouts of the circuits prepared using Cadence software are presented.     

Facile Synthesis of Fe3O4−SiO2 Nanocomposites for Wastewater Treatment

Water constitutes ≈70–90% of the organism's body by mass and is highly important for its survival. Water contains a variety of chemical contaminants introduced by various sectors, resulting in contamination that has a direct impact on the ecosystem. Various approaches are in practice to tackle these issues. Among these, semiconductor photocatalysis appears to be the cutting-edge technology for the degradation of wastewater contaminants. Herein, the fabrication of Fe₃O₄−SiO₂ nanocomposite via facile co-precipitation and Stober methods are reported. Various characterization techniques are employed for the structural elucidation, morphology, crystallinity, and stability of the as-prepared composite. The nanocomposite is employed in catalytic and photocatalytic applications toward the removal of methylene blue (MB) and methyl orange (MO) dyes from a comparative perspective. It is observed that the composite can remove about 93% of MB and 51% of MO within 7 and 6 h, respectively. These findings indicate that the nanocomposite has a higher MB removal effectiveness than the MO. This trend can be accredited to the difference in the chemical structure of both dyes. The nanocomposite is also evaluated for antioxidant and antileishmanial activity, and it is shown to be quite effective even at very low concentrations.     

Lateral-torsional buckling capacity assessment of web opening steel girders by artificial neural networks — elastic investigation

Bridge girders exposed to aggressive environmental conditions are subject to time-variant changes in resistance. There is therefore a need for evaluation procedures that produce accurate predictions of the load-carrying capacity and reliability of bridge structures to allow rational decisions to be made about repair, rehabilitation and expected life-cycle costs. This study deals with the stability of damaged steel I-beams with web opening subjected to bending loads. A three-dimensional (3D) finite element (FE) model using ABAQUS for the elastic flexural torsional analysis of I-beams has been used to assess the effect of web opening on the lateral buckling moment capacity. Artificial neural network (ANN) approach has been also employed to derive empirical formulae for predicting the lateral-torsional buckling moment capacity of deteriorated steel I-beams with different sizes of rectangular web opening using obtained FE results. It is found out that the proposed formulae can accurately predict residual lateral buckling capacities of doubly-symmetric steel I-beams with rectangular web opening. Hence, the results of this study can be used for better prediction of buckling life of web opening of steel beams by practice engineers.