Impact of the Cd2+ treatment on the electrical properties of Cu2ZnSnSe4 and Cu(In,Ga)Se2 solar cells

The present contribution aims at determining the impact of modifying the properties of the absorber/buffer layer interface on the electrical performance of Cu₂ZnSnSe₄ (CZTSe) thin‐film solar cells, by using a Cd²⁺ partial electrolyte (Cd PE) treatment of the absorber before the buffer layer deposition. In this work, CZTSe/CdS solar cells with and without Cd PE treatment were compared with their respective Cu(In,Ga)Se₂ (CIGSe)/CdS references. The Cd PE treatment was performed in a chemical bath for 7 min at 70 °C using a basic solution of cadmium acetate. X‐ray photoemission spectroscopy measurements have revealed the presence of Cd at the absorber surface after the treatment. The solar cells were characterized using current density–voltage (J–V), external quantum efficiency, and drive‐level capacitance profiling measurements. For the CZTSe‐based devices, the fill factor increased from 57.7% to 64.0% when using the Cd PE treatment, leading to the improvement of the efficiency (η) from 8.3% to 9.0% for the best solar cells. Similar observations were made on the CIGSe solar cell reference. This effect comes from a considerable reduction of the series resistance (R_S) of the dark and light J–V, as determined using the one‐diode model. The crossover effect between dark and light J–V curves is also significantly reduced by Cd PE treatment. Copyright © 2015 John Wiley & Sons, Ltd.     

Narrow Range of Hafnium Doping for Promoted Mechanical Properties and Critical Current Density (Jc) Values of?Mg1?xHfxB2 Superconductor

Hafnium was used as a softener dopant to replace at magnesium sites of Mg_1−x Hf _x B₂ regime (where x=0.0, 0.05, 0.1, 0.2, and 0.4 mole). Samples were prepared via high temperature solid state reaction technique depending upon diffusion mechanism of Mg-vapor ions through hafnium–boron matrix. The maximum solubility limit of hafnium (n) was found to be ∼0.22 mole. The crystalline lattice constants exhibit slight elongation in the case of the c-axis as x increases. Furthermore, the effect of Hf-doping on the microstructure properties of the MgB₂ system was investigated carefully. The SE-microscopic analysis indicated that hafnium ions diffuse regularly through surface and bulk in case of (x=0.05–0.2 mole). The grain size was estimated and found to be between 0.33 and 1.34 μm. The mechanical tensile strength of the samples was clearly improved linearly as Hf-content increased, recording the maximum tensile strength of 34.8 MPa for the sample with x=0.4 mole. A visualization of the Hf-doped MgB₂ structure was constructed and investigated to confirm the success of hafnium substitutions at the Mg-sites of the MgB₂ superconductor.     

Effect of Fiber-Reinforced Polymer Wraps on Corrosion Activity and Concrete Cracking in Chloride-Contaminated Concrete Cylinders

This paper presents the results of an experimental study designed to investigate the effect of fiber-reinforced polymer (FRP) wraps on corrosion activity and concrete cracking in chloride-contaminated concrete cylinders. Thirty-five concrete cylinders, each having 102?mm diameter and 204?mm height, concentrically reinforced with one steel reinforcing bar, were subjected to accelerated corrosion exposure for 80?days. Test parameters included level of applied potential, presence of FRP wraps, and bar diameter. The corresponding current and concrete expansion were continuously monitored throughout the corrosion exposure. At the end of the test, the steel bars were extracted, cleaned of rust, and weighed to determine the actual steel mass loss. The results showed that, for the same applied fixed potential, FRP wraps effectively reduced the corresponding current, the concrete expansion, and the steel mass loss. For the same applied potential, the current density increased as the bar diameter decreased. For the same corrosion depth, the circumferential expansion of the cylinder caused by corrosion decreased as the concrete cover-to-bar diameter ratio (c/d) increased.     

Infrared spectra, Raman laser, XRD, DSC/TGA and SEM investigations on the preparations of selenium metal, (Sb2O3, Ga2O3, SnO and HgO) oxides and lead carbonate with pure grade using acetamide precursors

Ga₂O₃, Se metal, SnO, Sb₂O₃, HgO and PbCO₃ are formed upon the reaction of acetamide aqueous solutions with Ga(NO₃)₃, SeO₂, SnCl₂, SbCl₃, HgCl₂ and Pb(NO₃)₂, respectively, at 90°C. Different amorphous or crystalline phases can be obtained depending upon the experimental conditions (molar ratios, metal salts and temperature). The chemical mechanisms for the formations of this metal, oxides or carbonate are discussed and the X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscope (AFM) are described. The type of metal ions plays an important role in the decomposition of acetamide, leading to the formation of solid stable (metal, oxides or carbonate), soluble and gases species. These new precursors are more stable preventing the rapid precipitation of metal, oxides or carbonate. Furthermore, this route allows the formation of pure compounds in solutions.     

Reliable information rate of signal‐time coding for half‐duplex additive white Gaussian noise relay networks

Signal‐time coding (STC) is a newly proposed transmission scheme for half‐duplex relay networks, which is able to achieve higher information flow rate by combining the traditional encoding/modulation mode in the signal domain with the signal pulse phase modulation in the time domain. However, most of the results for STC are only obtained under the ideal assumptions that the signal detections at physical layer are perfect and there are still a lot of fundamental problems to be explored. This paper considers the implementing issues of STC at physical layer in additive white Gaussian noise relay networks. Firstly, a performance evaluation criterion, the reliable information per symbol (RIPS), is proposed to characterize the performance of STC in noisy wireless networks. Secondly, a new construction scheme based on route ID for the codeword of STC is presented, and some structural properties of the codeword of STC are investigated. Thirdly, the error probabilities of STC in both the signal domain and the time domain are discussed. Furthermore, two implementing schemes, that is, the energy detection based STC (ED‐STC) and the symbol detection based STC (SD‐STC), are proposed, and their performance bounds in terms of RIPS are discussed. Numerical analyses show that both ED‐STC and SD‐STC outperform traditional transmission methods in terms of effective information rate even under some practical conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrogenerated base-promoted synthesis and antimicrobial activity of 2-imino-1,3-thiazolidin-4-one derivatives

Electrogenerated cyanomethylanions obtained by reduction of dry acetonitrile at a steel grid cathode were used to promote the addition of ethyl bromoacetate to thiourea derivatives. The reaction yields the corresponding 2-imino-1,3-thiazolidin-4-one. The reaction pathway was discussed based on the kinetic and thermodynamic data obtained by computational methods. In addition, the biological activity of these new compounds was also investigated.     

Partially bonded near-surface-mounted CFRP bars for strengthened concrete T-beams

A partially bonded strengthening approach for reinforced concrete (RC) beams utilizing near-surface-mounted (NSM) carbon fiber reinforced polymer (CFRP) bars was investigated with the specific objective of improving deformability. A total of six RC T-beams strengthened with NSM CFRP bars of various unbonded lengths were tested. Test results showed a decrease of the stiffness at the post-yield stage of the load–deflection response in the partially bonded beams. This is caused by the delayed increase of the FRP strain within the unbonded length. As a result the beam deformability was increased as the unbonded length increased at the same applied load. Internal slip of the FRP bar and gradual concrete failure were observed near the ultimate state, which caused a complicate nonlinear behavior of the beams. An analytical model is proposed to address the complete beam behavior including the effect of slip of FRP reinforcement and gradual concrete crushing. This model was developed based on the compatibility of deformation of the partially bonded system and was able to represent the ultimate behavior of the beams well.     

2D and 3D numerical simulation of the wind-rotor/nacelle interaction in an atmospheric boundary layer

Two-dimensional axisymmetric and three-dimensional steady turbulent flow computations around two horizontal-axis wind turbines (Nordex N80 and Jeumont J48) are carried out to investigate the wind-rotor/nacelle interaction and quantify its effects on the wind speed at the nacelle anemometry. The actuator disk concept has been used to model the action of the blades. For both turbines, the geometry of the nacelle was reproduced as faithfully as possible. The terrain was represented by an appropriate law of the wall to account for roughness with particular attention paid to the boundary conditions in order to reproduce the neutral atmospheric boundary layer. The calculated velocity field in the vicinity of the nacelle exhibits good agreement with available experimental data. The results also show that for a complex nacelle geometry, like that of the N80, a three-dimensional calculation is necessary to obtain a good prediction of the velocity field in the near wake. The hub height effect is evaluated for the J48 by raising the nacelle from a height of 36 to 60 m. No significant impact is noted on the ratio nacelle wind speed/freestream wind speed.