Synthesis of nano-structured lanthanum tungstates photocatalysts

Nano-particles of lanthanum tungstate were prepared through an optimized chemical precipitation reaction using the aqueous solutions of the ingredients. The optimization of the procedure was performed based on performing the so-called Taguchi robust design. The effects of various conditions influencing the size of the produced particles were evaluated using an orthogonal array. The optimally prepared lanthanum tungstate particles were found to be about 31 nm in diameter. The chemical and physical properties of the products were studied through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy, UV–Vis and Fluorescence. Also the band gap energy of the produced nanoparticles was assessed through UV–Vis diffuse reflectance spectroscopy. The optimally prepared nano-structures were evaluated as photocatalysts in the pho-degradation of methylene blue.     

Evaluating modes I,II, and mixed mode I-II fracture toughnesses of crystalline rocks using discrete element method

Several cracked chevron-notched Brazilian disk (CCNBD) and hollow center cracked disk (HCCD) samples of crystalline building stones naming Maroon, Baghat, and Neiriz in Iran, bearing the same calcite mineralogy and different grain size distributions were numerically modeled using three-dimensional particle flow code, with the respective microscopic mechanical properties measured through calibration technique. The simulation of CCNBD and HCCD samples highlights higher toughness compared to laboratory measurements. The values regarding HCCD samples are in a better agreement with experimental results than those regarding the CCNBD samples. The principal objective was to evaluate the reliability of numerical simulations in estimating fracture toughness and to recognize the mechanism and the mode of failure, of which laboratory tests are incapable. At microscales, failures occurring due to tensile or shear loadings may not be subsumed within any category as such at macroscales with failure modes I and II. Experimental and numerical results show that the K_IC values determined from both CCNBD and HCCD samples have a negative correlation with the grain size distributions of the marbles. However, no specific trend as such was identified for K_IIC.     

Reducing drag force on polyester fabric through superhydrophobic surface via nano-pretreatment and water repellent finishing

Energy saving is a very important factor for athletics that works in high speed and award winning competition. Drag force is of prime importance for determining the speed of objects that moves in the fluid. Nanotechnology is of great potential among the methods for reducing drag force. Enhancing the fabric speed in the fluids could be achieved using superhydrophobic surfaces to reduce the drag force. A simple and versatile method was utilized for the fabrication of superhydrophobic surfaces via pad-dry-cure and in situ synthesis of ZnO nanoparticles as a pre-treatment. The treated samples were examined by SEM for assessing the structure and size of nanoparticles and mapping and EDX analysis was carried out for further characterization. A novel method was designed based on the tensile tester apparatus for studying the changes in drag force. The results indicated a reduction of 80% in drag force of the treated fabric in the optimum conditions of pre-treatment with 10% zinc nitrate (Zn(NO₃)₂) and 5% sodium hydroxide (NaOH) at 130 °C for 1 h.     

Coupled Simulation-Optimization Model for the Management of Groundwater Resources by Considering Uncertainty and Conflict Resolution

Water Resources Management - Determining the optimized policies in the exploitation of groundwater water resources is a complicated issue, especially when there are several different managers with...     

Determination of Pb2+ ions by a modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and nanosilica

A novel carbon paste ion selective electrode for determination of trace amount of lead was prepared. Multi-walled carbon nanotubes (MWCNTs) and nanosilica were used for improvement of a lead carbon paste sensor response. MWCNTs have a good conductivity which helps the transduction of the signal in carbon paste electrode. The electrode composition of 20 wt% paraffin oil, 57% graphite powder, 15% ionophore (thiram), 5% MWCNTs, and 3% nanosilica showed the stable potential response to Pb²⁺ ions with the Nernstian slope of 29.8 (±0.2) mV decade^?1 over a wide linear concentration range of 10^?7–10^?2 mol L^?1. The electrode has fast response time, and long term stability (more than 2 months). The proposed electrode was used to determine the concentration of lead ions in waste water and black tea samples.     

Strontium PVC-membrane sensor based on 2-[(2-mercaptophenylimino)methyl]phenol

The 2-[(2-mercaptophenylimino)methyl]phenol (MPMP) was used as an excellent ionophore in the construction of a Sr²⁺ PVC-based membrane sensor. The best performance was obtained with a membrane composition of 30% poly(vinyl chloride), 62% nitrobenzen (NB), 5.5% MPMP and 2.5% sodium tetraphenyl borate (NaTBP). This sensor demonstrates a good selectivity and sensitivity towards the strontium ion for many cations, including alkali, alkaline earth, transition and heavy metal ions. The sensor revealed a great enhancement in selectivity coefficients for strontium ions in comparison with the previously reported strontium sensors. The proposed sensor exhibits a Nernstian behavior (with a slope of 29.6 ± 0.3 mV per decade) for the concentration range of (1.0 × 10^− 6–1.0 × 10^− 1 M) with a detection limit of 5.5 × 10^− 7 M (48.2 ng/mL). It illustrates a relatively fast response time in the whole concentration range (< 10 s) and it can be used for at least 10 weeks in a pH range of 2.8–9.6. The developed sensor was successfully used as an indicator electrode in the Sr(II) titration with EDTA and the Sr²⁺ ion recovery from binary mixtures.     

Bearings Fault Diagnosis Using Vibrational Signal Analysis by EMD Method

ABSTRACT

Studying vibrational signals is one reliable method for monitoring the situation of rotary machinery. There are various methods for converting vibrational signals into usable information for fault diagnosis, one of which is the empirical mode decomposition method (EMD). This article is about diagnosing bearing faults using the EMD method, employing nondestructive test. Vibration signals are acquired by a bearing test machine. The discrete wavelet bases are used to translate vibration signals of a roller bearing into time-scale representation. Then, an envelope signal can be obtained by envelope spectrum analysis of wavelet coefficients of high scales. Local Hilbert marginal spectrum can be obtained by applying thr EMD method to the envelope signal from which the faults in a roller bearing can be diagnosed and fault patterns can be identified. The results have shown bearing faults frequencies are easily observable. There is a variant of the EMD method called the ensemble EMD (EEMD), which overcomes the mode mixing problem which may occur when the signal to be decomposed is intermittent. The EEMD method is also applied to the acquired signals, and the two methods were compared. While the outcomes of both methods do not differ much, one important merit of the EMD is that it has much less computational processing time than EEMD.     

Separation and direct detection of heavy lanthanides using new ion-exchange chromatography: fast Fourier transform continuous cyclic voltammetry system

In this study, possibilities of heavy lanthanides (Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺, and Lu³⁺) separation on Nucleosil 100-5-SA, an ion-exchange column, was investigated. Separation of lanthanides was carried out using an isocratic program of α-hydroxyisobutyric acid (HIBA) eluent. Fast Fourier transform continuous cyclic voltammetry (FFT-CCV) at a gold microelectrode was used as the detection method. Simplicity, high precision and accuracy, time efficiency, and being economic are advantages of the developed technique in comparison with the previous reported ones. In addition, removal of oxygen from the test solution is not required, the detection limit is suitable and the technique is fast enough for determination of compounds in a wide variety of chromatographic methods. The waveform potential was continuously applied on an Au disk microelectrode (12.5 μm in radius). The influence of HIBA concentration as well as pH of eluent was optimized. The best performance of the method was obtained at pH of 4.0, scan rate of 30 V s⁻¹, accumulation potential of −300 mV, and accumulation time of 0.3 s. The proposed method displays a linear dynamic range of 140 and 18,000 μg L⁻¹ and a detection limit of 50 μg L⁻¹. Precision, inter-day precision, and accuracy of the assay were reported too. A comparative evaluation of heavy lanthanides distributed in a sophisticated monazite and xenotime minerals solutions was carried out using both FFT-CCV, and inductively coupled plasma-atomic emission spectrometry (ICP-AES).     

Understanding the Critical Role of Binders in Phosphorus/Carbon Anode for Sodium‐Ion Batteries through Unexpected Mechanism

Polymer binders that combine active materials with conductive agents have played a critical role in maintaining the structural integrity of phosphorus anodes with a huge volume change upon sodiation/desodiation. Herein, the role of binders on the structural/chemical stability of phosphorus/carbon anode is spectroscopically uncovered through unexpected mechanism. Surprisingly, the selection of different binders is found to determine the oxidation degree of active phosphorus in various electrodes, which correlate well with their electrochemical properties. At a high oxidation degree, the electrode applying a conventional poly(vinylidene difluoride) binder displays the worst electrochemical properties, while the electrode using a sodium alginate binder delivers the best electrochemical performance (a highly reversible capacity of 1064 mAh g^?1 with a 90.1% capacity retention at 800 mA g^?1 after 200 cycles and an outstanding rate capability of 401 mAh g^?1 at 8000 mA g^?1) for its negligible oxidation. Additionally, the emergence/decomposition of surface intermediates, including (PO₂)^3? and (PO₄)^3? species, are observed in the discharging/charging processes via the ex situ P K‐edge X‐ray absorption spectroscopies. This novel discovery of the unique role of binders in phosphorus anodes, not only provides an opportunity to ameliorate their electrochemical properties, but also enables their practical applications in high‐energy sodium‐ion batteries.     

Bifurcation Analysis of an Electrostatically Actuated Nano-Beam Based on Modified Couple Stress Theory

In this paper, the nonlinear size-dependent static and dynamic behavior of an electrostatically actuated nano-beam is investigated. A fully clamped nano-beam is considered for the modeling of the deformable electrode of the NEMS. The governing differential equation of the motion is derived using Hamiltonian principle based on couple stress theory; a non-classical theory for considering length scale effects. The nonlinear partial differential equation of the motion is discretized to a nonlinear Duffing type ODE’s using Galerkin method. Static and dynamic pull-in instabilities obtained by both classical theory and MCST are compared. At the second stage of analysis, shooting technique is utilized to obtain the frequency response curve, and to capture the periodic solutions of the motion; the stability of the periodic solutions are gained by Floquet theory. The nonlinear dynamic behavior of the deformable electrode due to the AC harmonic accompanied with size dependency is investigated.