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  • 1
    Publication Date: 2021-10-29
    Description: Thickness-shear (TSh) vibration of a rectangular piezoelectric crystal plate is studied with the consideration of flexoelectric effect in this paper. The developed theoretical model is based on the assumed displacement function which includes the anti-symmetric mode through thickness and symmetric mode in length. The constitutive equation with flexoelectricity, governing equations and boundary conditions are derived from the Gibbs energy density function and variational principle. For the effect of flexoelectricity, we only consider the shear strain gradient in the thickness direction so as to simply the mathematical model. Thus, two flexoelectric coefficients are used in the present model. The electric potential functions are also obtained for different electric boundary conditions. The present results clearly show that the flexoelectric effect has significant effect on vibration frequencies of thickness-shear modes of thin piezoelectric crystal plate. It is also found that the flexoelectric coefficients and length to thickness ratio have influence on the thickness-shear modes. The results tell that flexoelectricity cannot be neglected for design of small size piezoelectric resonators.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 2
    Publication Date: 2021-10-29
    Description: This paper aims to investigate the influence of periodicity temperature change on the properties of dry granular materials in macroscopic and microscopic. A series of cyclic thermal consolidation tests have been carried out based on the discrete element method (DEM) that incorporate particles’ volumetric thermal expansion coefficient. The simulation of the direct shear test was carried out on the samples after thermal cycling. Results showed that thermally-induced volumetric strain accumulation of the specimen can be calculated by the DEM model, based on the PFC2D software. The lateral pressure degraded concomitantly thanks to decreases in particles’ horizontal contact during periodic thermal cycling. In addition, the shear dilatancy level decreases during the shearing process with the number of thermal cycles. Both the size and anisotropy of the normal contact force and contact number and the force chain are affected by the temperature cycle. Finally, the results of this paper have a certain reference for the engineering practice, such as thermal piles or others, when granular materials are subjected to thermal cycling.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 3
    Publication Date: 2021-10-29
    Description: Olive oil production processes breed two kinds of environmentally detriment waste by-products; the solid olive residue (SOR) and olive waste water (OWW) by-products. The current work aims to treat simultaneously both wastes in the same location. The solid olive residue was converted to activated carbon with pyrolysis at 600°C, followed by steam activation at 600, 700 and 800°C. The produced activated carbons were investigated by FTIR, SEM, BET surface areas analyzer and iodine number. The surface area increases with increasing stream activation temperature up to 800°C (1020 m2/g BET). However, steam activation at 700°C is most environmental and economically feasible, because increasing the activation temperature from 700 to 800°C increases the surface area only from 979 to 1020 m2/g. Activated carbon steam cured at 700°C shows high removal capacity of both polyphenolic compounds and COD of OWW. 95.5% of COD and 84.2% of polyphenolic compounds was removed after equilibrium with activated carbon for 2 hours at room temperature.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 4
    Publication Date: 2021-10-29
    Description: In this study, the hot tensile test was carried out using the extruded and annealed Mg-1Al-6Y alloy. The effect of temperature and strain rate on the hot tensile deformation behavior of the alloy was systematically studied at different temperatures (200 ℃ ~ 350 ℃) and different strain rates (8×10-5 s-1 ~ 1.6×10-3 s-1). In addition, the effect of temperature on the evolution of microstructure when the strain rate is 1.6×10-3 s-1 was investigated. The results showed that as the temperature increased or the strain rate decreased, the peak stress decreased and the elongation increased. Hot tensile at different temperatures all increased the texture intensity, and the microstructure after deformation showed obvious characteristics of basal fiber texture ([0001]⊥ED). Correspondingly, the weaker [-15-40]//ED texture before deformation transformed into a stronger [01-10]//ED fiber texture. After deformation, the average Schmid factor (SF) of each non-basal slip was significantly increased compared with the average SF before deformation, indicating that abundant non-basal slip was activated during the deformation. When the deformation temperature was 300 °C, dynamic recrystallization (DRX) occurred significantly, and the DRXed grains accounted for 15.9%. DRX was a combination of continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). Furthermore, the calculated activation energy of the alloy was about 98.8 kJ/mol. Comprehensive research showed that the hot tensile deformation mechanism mainly included intragranular slip, grain boundary slip (GBS) and DRX.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 5
    Publication Date: 2021-10-01
    Description: Sn63Pb37/SAC305 mixed solder joint is inevitably in the electronic device requiring high reliability, such as health care, aerospace etc. However, the usage history of mixed solder joint is relatively short and as such their interfacial behaviour and reliability in service has not been completely figure out. Herein, the evolution of microstructures in fully mixed Sn63Pb37/SAC305 BGA solder joints during high-temperature storage were systematically studied. After reflow soldering process, the Pb-rich phases uniformly distributed in the fully mixed joint. During the thermal aging test, the size of Pb-rich phases gradually coarsened. The intermetallic compound (IMC) layers thickness at the two-side interface (upper interface: between the pad on substrate and solder; lower interface: between the pad on PCB and solder) were also increased. Moreover, the growth kinetics models of two-side IMC layer were successfully established according to the Arrhenius equation. IMC layer grows faster at higher temperature, because of higher diffusion coefficient. With the increasing of aging time, the fracture position partially moved from the interface between Ni layer and IMC layer into IMC internal. These results may provide support for the reliable applications of mixed Sn63Pb37/SAC305 solder joints.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 6
    Publication Date: 2021-10-01
    Description: Electropolishing (EP) is a reliable post-processing method of the drilled metals for achieving a high-quality surface finish with an appropriate material removal rate. This process has many applications due to its advantages such as improving the surface quality by removing the surface peaks on a micro-scale. The aim of most attempts on this process is setting up the optimum parameters to obtain maximum Material Removal Rate (MRR) with minimum surface roughness. In the present wo k, electropolishing of AISI 4340 low alloy steel immersed in eco-friendly NaCl solution has been studied numerically and experimentally. So, primarily a simulation model was developed for the EP process on cylinder parts in COMSOL Multiphysics which was validated with experimental approaches. The results revealed that the numerical model would be convenient for EP. The experiments were performed using Response Surface Methodology (RSM) to evaluate the effect of input variables on the responses. The effects of input variables electrolyte temperature, current intensity, and primary gap were investigated on the outputs MRR and surface roughness at five levels. Based on the results, the electrolyte temperature and current intensity were more effective parameters on the outputs. Results of ANOVA and regression analysis approach revealed that by increasing the current and electrolyte temperature, the MRR increases correspondingly and surface roughness declines and the primary gap has a reverse effect on the MRR. Finally, by performing a multi-objective optimization using Derringer’s desirability approach, the EP of AISI 4340 with an eco-friendly NaCl solution was optimized.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 7
    Publication Date: 2021-10-01
    Description: In this study, high-density polyethylene (HDPE) surfaces were treated with plasma to enhance the adhesion of a water-based paint. A custom-built cold atmospheric pressure plasma jet (CAPPJ) device using a neon transformer as its power source was developed and used in the surface treatment. The jet nozzle of the device was made from polytetrafluoroethylene with two bare stainless-steel electrodes positioned laterally through the nozzle and opposite each other with a 1 mm gap. Gas was allowed to pass through the nozzle, exiting through a 1 mm diameter hole where a plasma jet is ejected through the arc from the electrodes. The effect of plasma treatment on HDPE surfaces was determined. Air and nitrogen were used as the process gases and exposure times were also varied. Hydrophilicity of the surface increased with longer plasma exposure with a corresponding 50% increase in surface free energy compared to the untreated surface. From Fourier transform infrared and x-ray photoelectron spectroscopy analysis, it was seen that plasma treatment introduced oxygen containing functionalities onto the surface. Increase in adhesion of a water-based paint was observed for plasma-treated HDPE sheets.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 8
    Publication Date: 2021-10-01
    Description: Energy absorption for AZ31 magnesium Alloy was investigated with Split Hopkinson Pressure Bar using single stress wave so as to avoid multiple stress wave loading. The stress wave amplitude, which was in elastic stress range and propagated along the AZ31 magnesium bar, was reduced with increasing propagating distance, and with increasing stress wave amplitude, the stress wave amplitude reduction along the magnesium bar was increased losing more energy as compared with that of the stress wave with lower amplitude. The drastically decreased stress wave amplitude could be explained based on dislocations movements, which was similar to the established theory of damping for the explanation of the energy loss during cyclic loading. However, it was not the case for LY12 aluminum alloy: the stress wave amplitude changed slightly without drastic energy loss regardless of the variation of stress wave amplitude.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 9
    Publication Date: 2021-10-01
    Description: Here, the corrosion weight-loss method, surface analysis technology, and electrochemical test methods were used to study the corrosion behavior and electrochemical characteristics of experimental samples of Q345R steel in a sterile solution (pH 2.0) and a solution containing T. ferrooxidans. The growth cycle of T. ferrooxidans was determined to be approximately 8 days. The corrosion weight-loss method showed that the corrosion rate of Q345R carbon steel coupons decreased with time in the T. ferrooxidans system and the sterile system; the corrosion rate was approximately two times higher in the T. ferrooxidans system than in the sterile system. The corrosion morphology results showed that the presence of T. ferrooxidans promotes the corrosion of Q345R steel and increases the local corrosion of the matrix material. The electrochemical test results showed that after 5 days of corrosion, the polarization resistance of the T. ferrooxidans system was approximately 50% of that of the sterile system, and the corrosion current density of the T. ferrooxidans system was approximately twice as high as that of the sterile system. Therefore, T. ferrooxidans can accelerate the corrosion of Q345R steel two-fold.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 10
    Publication Date: 2021-10-01
    Description: As good models for developing techniques, Haloarchaea are using as cell factories to produce a considerable concentration of bioplastics, polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), and polyhydroxyvalerate (PHV). In this study, low-cost carbon sources by Sudan Black staining was applied for screening haloarchaea a hypersaline environment (southern coast of Jeddah, Saudi Arabia). The growth of the selected isolate and PHB-production under different carbon sources, temperature, pH values and NaCl concentrations were investigated. The biopolymer was extracted and quantitatively measured. The biopolymer was qualitatively identified by Fourier-transform infra-red analysis (FTIR) and High Performance Liquid Chromatography (HPLC). The potential Haloarcula sp strain NRS20 (MZ520352) could significantly accumulate PHB under nutrient-limiting conditions using different carbon sources including starch, carboxymethyl cellulose (CMC), sucrose, glucose and glycerol with 23.83%, 14%, 11%, 12% and 8% of PHB/CDW respectively under 25% NaCl (w/v), pH 7, at 37 °C. The results of FTIR pattern indicated that the significant peak at 1709.22 cm−1 confirmed the presence of the ester carbonyl-group (C=O) which is typical of PHB. HPLC analysis indicated that produced PHB was detected at 7.5 min with intensity exceeding the standard PHB at 8.0 min. Few potential species of haloarchaea were reported for economical PHB-production, here, Haloarcula sp strain NRS20 showed high content of PHB, exhibited a promising PHB-producer using inexpensive sources of carbon.
    Electronic ISSN: 2053-1591
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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