Efficient Continuous-Wave and Q-Switched Operation of a 946-nm Nd:YAG Laser Pumped by an Injection-Locked Broad-Area Diode Laser

The efficient, low-threshold operation of a 946-nm Nd:YAG laser pumped by an injection-locked broad-area diode laser is reported. The implications of pump-beam quality for efficient, low-threshold operation, particularly with intrinsically inefficient transitions, are discussed in the context of previously published models. Results are presented showing that the M(2) = 1.3 pump beam of the injection-locked diode laser enabled a cw slope efficiency of 48% and a threshold of 52 mW to be attained. When Q-switched, 335 mW of pump power gave 27-ns, 5.2-muJ pulses. These were frequency doubled to obtain 19-ns, 1-muJ pulses at 473 nm. These results represent significant improvements over similar systems pumped by free-running broad-area diode lasers or arrays.     

A Fuzzy Congestion Control Protocol Based on Active Queue Management in Wireless Sensor Networks with Medical Applications

Wireless Personal Communications - Wireless Sensor Network has been widely used in a variety of applications such as; medical, agriculture, military, monitoring environment and so on. In healthcare...     

Application of response surface methodology and central composite rotatable design for modeling the influence of some operating variables of the lab scale thickener performance

This study discussed the application of response surface methodology (RSM) and central composite rotatable design (CCRD) for modeling and optimization of the influence of some operating variables on the performance of a lab scale thickener for dewatering of tailing in the flotation circuit. Four thickener operating variables, namely feed flowrate, solid percent, flocculant dosage and feedwell height were changed during the tests based on CCRD. The ranges of values of the thickener variables used in the design were a feed flowrate of 9–21 L/min, solid percent of 8%–20%, flocculant dosage of 1.25–4.25 g/t and feedwell height of 16–26 cm. A total of 30 thickening tests were conducted using lab scale thickener on flotation tailing obtained from the Sarcheshmeh copper mine, Iran. The underflow solid percent and bed height were expressed as functions of four operating parameters of thickener. Predicted values were found to be in good agreement with experimental values (R² values of 0.992 and 0.997 for underflow solid percent and bed height, respectively). This study has shown that the RSM and CCRD could efficiently be applied for the modeling of thickener for dewatering of flotation tailing.     

Investigation of the photocatalytic activity of magnesium-doped Viburnum Opulus-like nickel oxide microstructure under visible light irradiation

In this study, the Viburnum Opulus-like NiO microstructure was synthesized by doping with various levels of Mg (1, 2, 3, 7, and 13 wt%) with the hydrothermal method. The X-ray diffraction analysis showed the tensile lattice strain and dispersion of Mg dopants in prepared samples. The cubic phase was observed in NiO and NiO with 13 wt% Mg-doping and phase change to rhombohedral was appeared in 1–3 and 7 wt% Mg-doping samples. According to the Urbach energy value, lattice disorder was reduced in 1–3 wt% Mg-doping. The sample with 13 wt% Mg-doping exhibited 3.1 times higher Urbach energy value compared to NiO. The degradation efficiency of the Methylene blue was approximately 92.98% for Mg-doped NiO with 13 wt% Mg in 105?min due to the charge trapping by localized states and reduction of recombination of charges. The photoluminescence showed the efficient electron–hole separation for all Mg-doped samples. The excellent durability and recyclability of photocatalyst over four cycles are representing that this material has a potential application in water remediation.

     

A new PI-based optimal linear quadratic state-estimate tracker for discrete-time non-square non-minimum phase systems

A new proportional–integral (PI)-based optimal linear quadratic state-estimate tracker, derived using a proportional–integral–derivative (PID) filter-based frequency-domain shaping approach, is proposed in this paper for discrete-time non-square non-minimum phase multi-input-multi-output systems. Subsequently, a new integrated PID filter-shaped optimal PI state estimator is presented for the aforementioned systems, so that both the proposed state estimator and the state-estimate tracker are able to achieve satisfactory minimum phase-like tracking performance, for the case of arbitrary command inputs with significant variations at some isolated time instants.     

Continuously tunable femtosecond pulses covering 2·1–2·5 μm from an optical parametric oscillator based on RbTiOAsO4

Abstract

The operation of a synchronously pumped femtosecond optical parametric oscillator based on the nonlinear material RbTiOAsO₄ is described. The idler output was continuously tuned from 2·1 to 2·5 μm, the pulses having powers as high as 140 mW and durations as short as 140 fs. Characterization of the pulses was achieved by use of a novel autocorrelator based on an InGaAs photodiode and a LiNbO₃ frequency-doubling crystal, capable of producing high quality interferometric and intensity autocorrelations.     

Pyridine‐2,6‐diamine‐functionalized Fe3O4 nanoparticles as a novel sorbent for determination of lead and cadmium ions in cosmetic samples

A novel sorbent based on pyridine‐2,6‐diamine‐functionalized Fe₃O₄ nanoparticles was developed and characterized by X‐ray powder diffraction (XRD), elemental analysis, IR spectroscopy and scanning electron microscopy (SEM). The application of the sorbent was investigated for pre‐concentration and determination of lead and cadmium ions in aqueous samples. Effects of various factors such as the sample pH, eluent parameters (type, concentration and volume) and time (adsorption and desorption) were appraised. The effects of several interfering ions on method recovery were also investigated. The limit of detection (LOD) was found to be 1.3 and 0.089 μg L^?1 for lead and cadmium ions, respectively. Recovery and precision (RSD%) of the method were above 97.9% and below 0.6%, respectively. Validation of the outlined method was performed by analysing several certified reference materials. This method was successfully used for determination of lead and cadmium ions in several cosmetic samples, which are usually contaminated by lead and cadmium ions.     

Fabrication and characterization of electrospun fibrous nanocomposite scaffolds based on poly(lactide‐co‐glycolide)/poly(vinyl alcohol) blends

Tissue engineering involves the fabrication of three‐dimensional scaffolds to support cellular in‐growth and proliferation. Ideally, the scaffolds should be similar to the native extracellular matrix (ECM). Electrospun polymer nanofibrous scaffolds are appropriate candidates for ECM mimetic materials since they mimic the nanoscale properties of ECM. Electrospun polymer nanocomposites based on poly(lactide‐co‐glycolide) (PLGA)/poly(vinyl alcohol) (PVA) and organically modified montmorillonite (OMMT) were prepared by a solution intercalation technique followed by electrospinning. The morphology of fibrous scaffolds based on these nanocomposites was investigated using scanning electron microscopy. The scaffolds showed highly porous structure within the nanofibres of diameters ranging from 400 to 700 nm. X‐ray diffractometry gave evidence of good dispersion of the OMMT in the blends with exfoliated morphology. Measurements of the water uptake and water contact angle of the fibrous scaffolds indicated significant improvement in the hydrophilicity of the scaffolds. Evaluations of the mechanical properties and unrestricted somatic stem cell culture of the electrospun fibrous nanocomposite scaffolds revealed that the PLGA90/PVA10/1.5% OMMT and PLGA90/PVA10/3% OMMT samples are the most useful from the tissue engineering application viewpoint. Copyright © 2010 Society of Chemical Industry     

Binary quadratic programming formulation for routing and wavelength assignment problem in all-optical WDM networks

Routing and wavelength assignment (RWA) is the most concern in wavelength routed optical networks. This paper proposes a novel binary quadratic programming (BQP) formulation for the static RWA problem in order to balance traffic load among a network links more fairly. Subsequently, a greedy heuristic algorithm namely variable-weight routing and wavelength assignment (VW-RWA) is proposed to solve the developed BQP problem. In this method, the weight of a link is proportional to the link congestion. Performance evaluation results for different practical network topologies show that our proposed algorithm can decrease the number of required wavelengths in the network, blocking rate and variance of used wavelengths in each link. Besides, it is shown that the number of required wavelengths to establish call requests for a given network topology can be reduced at lower cost compared to other heuristics.