Forming simulation of aluminum sheets using an anisotropic yield function coupled with crystal plasticity theory

This paper describes the application of a coupled crystal plasticity based microstructural model with an anisotropic yield criterion to compute a 3D yield surface of a textured aluminum sheet (continuous cast AA5754 aluminum sheet). Both the in-plane and out-of-plane deformation characteristics of the sheet material have been generated from the measured initial texture and the uniaxial tensile curve along the rolling direction of the sheet by employing a rate-dependent crystal plasticity model. It is shown that the stress–strain curves and R-value distribution in all orientations of the sheet surface can be modeled accurately by crystal plasticity if a “finite element per grain” unit cell model is used that accounts for non-uniform deformation as well as grain interactions. In particular, the polycrystal calculation using the Bassani and Wu (1991) single crystal hardening law and experimental electron backscatter data as input has been shown to be accurate enough to substitute experimental data by crystal plasticity data for calibration of macroscopic yield functions. The macroscopic anisotropic yield criterion CPB06ex2 (Plunkett et al., 2008) has been calibrated using the results of the polycrystal calculations and the experimental data from mechanical tests. The coupled model is validated by comparing its predictions with the anisotropy in the experimental yield stress ratio and strain ratios at 15% tensile deformation. The biaxial section of the 3D yield surface calculated directly by crystal plasticity model and that predicted by the phenomenological model calibrated with experimental and crystal plasticity data are also compared. The good agreement shows the strength of the approach. Although in this paper, the Plunkett et al. (2008) yield function is used, the proposed methodology is general and can be applied to any yield function. The results presented here represent a robust demonstration of implementing microscale crystal plasticity simulation with measured texture data and hardening laws in macroscale yield criterion simulations in an accurate manner.     

Metal oxides composite electrode with high areal capacitance formed by thermal oxidation of stainless steel mesh

Journal of Solid State Electrochemistry - The motivation of this study is to understand the usability of annealed stainless steel mesh obtained by a straightforward method for energy storage...     

Simulation and micro-fabrication of optically switchable split ring resonators

The effect of conductivity variation as a proposed method for the investigation of photoconductive switching properties of split ring resonators (SRRs) is simulated. Three different systems that are applicable under certain fabrication and/or optical excitation conditions are described. The simulated transmission spectrum indicates that for a large range of dark conductivity values, complete switching of the SRR resonance is possible. One of the simulated systems, involving split ring resonators on Si substrate, was fabricated and characterized. The transmission spectrum of that system was measured, with the Si in its high-resistivity state, and a −60 dB dip between 108 and 115 GHz, due to SRRs magnetic resonance, was observed.     

Experimental observation of true left-handed transmission peaks in metamaterials

We report true left-handed (LH) behavior in a composite metamaterial consisting of a periodically arranged split ring resonator (SRR) and wire structures. We demonstrate the magnetic resonance of the SRR structure by comparing the transmission spectra of SRRs with those of closed SRRs. We have confirmed experimentally that the effective plasma frequency of the LH material composed of SRRs and wires is lower than the plasma frequency of the wires. A well-defined LH transmission band with a peak value of -1.2 dB (-0.3 dB/cm) was obtained. The experimental results agree extremely well with the theoretical calculations.     

Simple high‐performance liquid chromatography method for formaldehyde determination in human tissue through derivatization with 2,4‐dinitrophenylhydrazine

A simple high‐performance liquid chromatography method has been developed for the determination of formaldehyde in human tissue. FA Formaldehyde was derivatized with 2,4‐dinitrophenylhydrazine. It was extracted from human tissue with ethyl acetate by liquid–liquid extraction and analyzed by high‐performance liquid chromatography. The calibration curve was linear in the concentration range of 5.0–200 μg/mL. Intra‐ and interday precision values for formaldehyde in tissue were <6.9%, and accuracy (relative error) was better than 6.5%. The extraction recoveries of formaldehyde from human tissue were between 88 and 98%. The limits of detection and quantification of formaldehyde were 1.5 and 5.0 μg/mL, respectively. Also, this assay was applied to liver samples taken from a biopsy material.     

Comparison of preconcentration methods for nontargeted analysis of natural waters using HPLC-HRMS: Large volume injection versus solid-phase extraction

Nontargeted analysis of water samples using liquid chromatography combined with high-resolution mass spectrometers is an emerging approach for surface water monitoring and evaluation of water treatment processes. In this study, sample preconcentration via direct, large volume injection with 500 μL and 1000 μL injection volumes was compared to SPE regarding analytical performance parameters in targeted and nontargeted workflows. In targeted analysis, the methods were evaluated in terms of LOD and intrabatch precision of the selected compounds, whereas in nontargeted analysis, the number of detected unknown compounds, the method's intra-batch precision, and the retention time versus molecular mass pattern of the detected unknowns were evaluated. In addition, a novel intensity drift correction method was developed that is not based on quality control samples and makes use of the signals obtained for continuously infused reference compounds, which are conventionally utilized for online mass drift correction. It could be demonstrated that the new correction method significantly reduced the bias introduced by instrumental drift and is important for the reliable intercomparison of different nontargeted methods. Intercomparison of results showed that the 1000 μL large volume injection method revealed the best performance in terms of precision under repeatability conditions of measurement as well as lower LODs for targeted compound analysis. In nontargeted analysis, the SPE method detected a higher number of unknown compounds but exhibited also a higher uncertainty of measurement caused by matrix effects.     

Determination of mineral element concentrations in wheat,sunflower, chickpea and lentil cultivars in response to P fertilization by polarized energy dispersive X‐ray fluorescence

Concentrations of elements (P, K, S, Ca, Mg, Si, Cl, Fe, Zn, Cu, Mn, Mo, Na, Al, Ti, Ni, Ba, As, Br, Rb and Sr) of wheat, sunflower, chickpea and lentil cultivars grown in low and high phosphorus soil were investigated by polarized energy dispersive X‐ray fluorescence (PEDXRF). The phosphorus treatment x cultivars interaction was significant for the growth and element concentrations, and cultivars within plant species differed considerably with respect to element concentrations as the result of P fertilization. Shoot growth of the cultivars of each plant species was increased in response to phosphorus fertilization. Application of P increased the P concentrations of wheat, sunflower, chickpea and lentil cultivars. Under high P conditions, mean K concentrations of wheat and sunflower cultivars were decreased while the mean K concentrations of chickpea and lentil were increased. With the exception of sunflower cultivars, applied P significantly increased S concentration of the cultivars of wheat, chickpea and lentil. Calcium concentrations of wheat and sunflower cultivars were reduced by P fertilization and that of chickpea and lentil were increased. Applied P decreased mean Mg concentrations in sunflower, increased in chickpea and lentil cultivars and showed no effects on the wheat cultivars. Applied P significantly decreased mean Si concentrations of wheat and sunflower while mean Si concentrations of the chickpea and lentil cultivars were increased. Chloride concentrations of the wheat and sunflower cultivars were decreased and those of the chickpea and lentil cultivars were increased by applied P. In general, Fe concentrations of the wheat and chickpea cultivars were significantly increased by applied P. Zinc and Cu concentrations of all the cultivars of the four plant species were reduced by P, particularly Zn concentrations. However, applied P increased mean Mn concentrations of wheat and chickpea and decreased those of chickpea cultivars. Mean Mo concentrations of wheat and chickpea increased but decreased in sunflower and lentil cultivars. In general, applied P increased mean Na concentration of wheat and decreased that of chickpea and lentil. Aluminum concentrations of wheat and chickpea cultivars were decreased by applied P. Applied P decreased Ti concentrations of wheat and sunflower cultivars and increased Ti concentrations of chickpea and lentil. Nickel concentrations of wheat and chickpea were increased and those of sunflower and lentil were decreased by applied P. Applied P reduced the Ba and increased As and Rb concentrations of all the cultivars within the plant species. Bromine concentrations of wheat and lentil were decreased and those of sunflower and chickpea were increased by applied P. Finally, Sr concentrations in wheat and sunflower cultivars were reduced, and increased in chickpea cultivars with applied P. Copyright © 2009 John Wiley & Sons, Ltd.     

A New Fluorescent “Turn-Off” Coumarin-Based Chemosensor: Synthesis,Structure and Cu-Selective Fluorescent Sensing in Water Samples

We report the synthesis and characterization two coumarin-based fluorescence probes, N′-{[7-(diethylamino)-2-oxo-2H-chromen-3-yl]carbonyl}pyridine-3-carbohydrazide (3) and N′-benzoyl-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (4), proposed as a novel fluorescent chemosensor. The two probes designed showed an instant turn-off fluorescence response to Cu²⁺ over other metal ions in ethanol-water mixture based on intramolecular charge transfer (ICT). It was found that pyridine-analogue coumarin is highly selective and sensitive sensor for Cu²⁺. The 3 sensor coordinates Cu²⁺ in 1:1 stoichiometry with a binding constant, K_a = 5.22 M^?1 and the detection limit was calculated 1.97 × 10^?9 M.