Adaptive joint subband vector quantisation codec for handheld videophone applications

A new wavelet-based video codec is presented, which joins vectors in the same subbands of different frames in a frame group and uses the properties of the human visual system. Perceptual weights are designed and used in the vector selection and quantisation of the wavelet coefficients. Results indicate a significant improvement in frame quality compared to JPEG2000 image sequence coder.     

Electrophoretic deposition of titanium nitride coatings

Electrophoretic deposition of the titanium nitride (TiN) coatings from suspensions prepared by dispersion of TiN particles in triethanolamine (TEA) containing butanol medium was studied. Effects of the TiN particles concentration (C_TiN) on the weight of the deposited coatings, triethanolamine concentration (C_TEA=0.25, 0.5, 0.75, and 1 mL/L) on the Zeta potential of the TiN particles, suspension electrical conductivity and pH, as well as effects of the deposition voltage (V_d=60, 90, and 120 V) and time (t_d =1, 2, and 3 minutes) on the microstructure and thickness of the deposited coatings were investigated. Variations in deposition current density, effective deposition voltage, electrical resistance, and deposited coating weight versus deposition time were recorded. The morphology of the as‐dried coatings was studied using Scanning Electron Microscope (SEM). The results indicated that by increasing the C_TiN the weight of deposits increases linearly up to 40 g/L. For suspensions containing C_TiN=40 g/L, the optimum C_TEA is obtained to be 0.5 mL/L leading to Zeta potential of 43.25 mV. Uniform and crack‐free as‐dried coatings obtained at V_d and t_d of 90 V and 2 minutes, respectively.     

Investigation of cohesive FE modeling to predict crack depth during deep-scratching on optical glasses

Optical glass scratching can induce various types of cracks, among which median cracks are extremely detrimental and penetrate deeply under the surface. Due to deep-scratching process complexity, it is challenging to devise a method to predict median crack depth. Indentation testing has been examined comprehensively in prior research works. It has been found that using the correlation between scratch and indentation testing can simplify predictive method development. In this research, a numerical method based on indentation testing is proposed to determine median crack depth during deep scratching. In the first step, an FE model is configured to simulate the indentation testing process and the Cohesive Zone Method is applied to describe median crack behavior. The cohesive parameters calibrated through experimental indentation testing are implemented in the FE scratch model, and the results are compared with the experimental scratch test results. According to the results, the FE scratch model was enhanced by mode II fracture energy and the modeled friction coefficient. The indentation and scratch experiments were conducted with BK7, F2, Fused silica, K5, Pyrex, Quartz, SF6, and SF19. The experimental results prove that the nonlinearity of the median crack depth curve correlates with K_Ic. A comparison of the experimental and numerical results demonstrates the model is virtually functional for materials with K_Ic below 1000?kPa?m^1/2. Comparisons between the current findings and other studies infer the model and experimental results are accurate and reliable.     

Thermodynamic Phase Diagram,Half-Metallic and Optical Properties of the Zr2TiSi [111] Films Based on DFT

Silicon - Thermodynamic stability, electronic and optical properties of the Zr2TiSi compound in the bulk and its [111] films have been investigated, based on the density functional theory (DFT)...     

Gas-liquid flow mass transfer in a T-shape microreactor stimulated with 1.7 MHz ultrasound waves

This paper describes the application of ultrasound waves on hydrodynamics and mass transfer characteristics in the gas-liquid flow in a T-shape microreactor with a diameter of 800 μm.A 1.7 MHz piezoelectric transducer (PZT) was employed to induce the vibration in this microreactor.Liquid side volumetric mass transfer coefficients were measured by physical and chemical methods of CO2 absorption into water and NaOH solution.The approach of absorption of CO2 into a 1 mol· L-1 NaOH solution was used for analysis of interfacial areas.With the help of a photography system,the fluid flow patterns inside the microreactor were analyzed.The effects of superficial liquid velocity,initial concentration of NaOH,superficial CO2 gas velocity and length of microreactor on the mass transfer rate were investigated.The comparison between sonicated and plain microreactors (microreactor with and without ultrasound) shows that the ultrasound wave irradiation has a significant effect on kLa and interfacial area at various operational conditions.For the microreactor length of 12 cm,ultrasound waves improved kLa and interfacial area about 21％ and 22％,respectively.From this study,it can be concluded that ultrasound wave irradiation in microreactor has a great effect on the mass transfer rate.This study suggests a new enhancement technique to establish high interfacial area and kLa in microreactors.     

Dendrigraft with citric acid on acrylonitrile/acrylic acid copolymer electrospun fibres

Acrylonitrile/acrylic acid copolymers were synthesized with different mole fractions (1, 2, 5 and 10 mol%) of acrylic acid (AA) in the feed by aqueous suspension polymerization, and bead‐free fibres (295–375 nm in diameter) were made from the copolymers in dimethylformamide solutions by electrospinning. In a heterogeneous system containing electrospun fibre mats, dendritic molecules were grown by reaction between carboxylic acid of AA and –OH groups of citric acid activated by dicyclohexylcarbodiimide. The products were analysed using ¹H NMR, ¹³C NMR and Fourier transform infrared spectroscopies, density determination, scanning electron microscopy, optical microscopy, differential scanning calorimetry and pH response properties. With decreasing AA content, the isotacticity of the copolymers decreases with a more random distribution of the co‐monomers which leads to higher percentage conversions of dendrigraft due to reduced steric hindrance. On the formation of dendrigraft, the percentage conversion of the reactions decreases with an increase of generation number and AA content. A reduction of density for the first generation and then an increase with increasing generation are observed. During oxidation stabilization of fibres with a decrease of AA content and an increase in generation number, the amount of liberated heat increases. Fibres containing more carboxylic groups show significantly greater amounts of swelling/de‐swelling in basic and acidic media, respectively. To be used as nanocarbon fibre precursors, or as active particles for loading with guest molecules, or as pH actuators, the first generation of dendrigrafted fibres are expected to have the greatest potential among the various samples examined. © 2013 Society of Chemical Industry     

The effect of EEMAO processing on surface mechanical properties of the TiO2–ZrO2 nanostructured composite coatings

We report fabrication of TiO₂–ZrO₂ nanostructured composite coatings by EPD-Enhanced MAO (EEMAO) technique on titanium substrates where especial emphasis was placed on improving the surface hardness of the substrates and establishing a microstructure-property correlation. Based on the XRD and the EDX results, the layers consisted of anatase, rutile, monoclinic zirconia, and tetragonal zirconia. It was observed that the anatase/rutile and tetragonal/monoclinic zirconia rations increased with the processing time and the electrolyte concentration. The zirconia content also increased with the processing time and the electrolyte concentration. XPS technique was also employed to further confirm the surface chemical composition and stoichiometry of the layers. A uniform distribution of zirconia across the titania matrix was evident in the SEM images. The surface hardness of the TiO₂-ZrO₂ composite layers was observed to increase with the zirconia concentration. Employing EEMAO technique, the surface harness of the titanium substrates was successfully improved from ∼190 Hv to ∼700 Hv.     

Sulfur removal of gas oil using ultrasound-assisted catalytic oxidative process and study of its optimum conditions

Ultrasound-assisted oxidative desulfurization process (UAOD) was applied to reduce sulfur compounds of gas oil containing various types of sulfur content. The environmental regulation requires a very deep desulfurization to eliminate the sulfur compounds. UAOD is a promising technology with lower operating cost and higher safety and environmental protection. For the first time the typical phase transfer agent (tetraoctyl-ammonium-bromide) was replaced with isobutanol because using isobutanol is much more economical than TOAB, imposing no contamination. The reaction was carried out at optimal point with various temperatures, in single-, two- and three step-procedures, investigating the effect of gradual increase of H₂O₂ and TOAB being used instead of isobutanol. Total sulfur concentration in oil phase was analyzed by ASTM-D3120 method. The highest removal of about 90% for gas oil containing 9,500 mg/kg of sulfur was achieved in three-steps during 17 minutes of process at 62±2 °C when 180.3 mmol of H₂O₂ was used and extraction carried out by methanol.