Direct incorporation of vanadium into three-dimensional KIT-6: 2. Reactivity test for styrene oxidation

The direct incorporation of vanadium into the three-dimensional (3-D) cubic Ia3d mesostructure designated as V-KIT-6 was prepared, and the material obtained therein showed a very high specific surface area of ∼1,000 m²/g with tunable pore diameters in a narrow distribution of sizes, ∼5.7 to 6.0 nm. The coordination and nature of the V sites in V-KIT-6 were characterized by ⁵¹V-spin-echo NMR analysis. It shows that after calcination, the V⁴⁺ species are totally oxidized to the V⁵⁺ state with 4- and 6-coordinated V-O environments in a highly dispersed state with much less crystalline V₂O₅ formation. The calcined V-KIT-6 materials showed excellent catalytic activity in the direct oxidation of styrene using tert-butyl hydroperoxide (TBHP) as an oxidant.     

Development of optoelectronic-based pulsed current sensor to detect the poor laser discharge condition

A current transformer (CT)-based sensor has been developed to detect poor discharge conditions in copper vapour laser. The optoelectronic-based pulsed current sensor architecture involves the optical transmitter–receiver HFBR, high-frequency current transformer, and fiber optic link. The CT has been designed and calibrated to ensure generation of an optical signal at the current threshold crossover. Bandwidth analysis of the CT is carried out using the bode plot. The optoelectronic inter-conversion of the pulsed voltage of the CT and transmission via fiber optic link provides the non-contact current sensing and remote signal processing of the signal. This study discusses the details of the sensor.     

Contact-Barrier Free,High Mobility,Dual-Gated Junctionless Transistor Using Tellurium Nanowire

The gate-all-around nanowire transistor, due to its extremely tight electrostatic control and vertical integration capability, is a highly promising candidate for sub-5 nm technology nodes. In particular, the junctionless nanowire transistors are highly scalable with reduced variability due to avoidance of steep source/drain junction formation by ion implantation. Here a dual-gated junctionless nanowire p-type field effect transistor is demonstrated using tellurium nanowire as the channel. The dangling-bond-free surface due to the unique helical crystal structure of the nanowire, coupled with an integration of dangling-bond-free, high quality hBN gate dielectric, allows for a phonon-limited field effect hole mobility of 570 cm² V⁻¹ s⁻¹ at 270 K, which is well above state-of-the-art strained Si hole mobility. By lowering the temperature, the mobility increases to 1390 cm² V⁻¹ s⁻¹ and becomes primarily limited by Coulomb scattering. The combination of an electron affinity of ≈ 4 eV and a small bandgap of tellurium provides zero Schottky barrier height for hole injection at the metal-contact interface, which is remarkable for reduction of contact resistance in a highly scaled transistor. Exploiting these properties, coupled with the dual-gated operation, we achieve a high drive current of 216 μA μm⁻¹ while maintaining an on-off ratio in excess of 2 × 10⁴. The findings have intriguing prospects for alternate channel material based next-generation electronics.     

Growth by SR method and characterization of hippuric acid single crystals

The potential organic nonlinear optical material of hippuric acid (HA) has been grown by novel unidirectional solution growth method using dimethyl formamide (DMF) as the solvent. The crystal system has been identified and lattice dimensions have been measured from the single crystal X-ray diffraction analysis. The crystalline perfection has been evaluated by high resolution X-ray diffraction (HRXRD) technique and found that the crystal quality is reasonably good. However, it contains a low angle structural grain boundary. The relative second harmonic generation (SHG) has been tested using Kurtz powder technique and found to be 1.54 times higher than that of potassium dihydrogen phosphate (KDP) single crystal. Its optical character has been assessed by UV-Vis. analysis and found that there is no absorption in the entire visible region.     

Epoch Extraction by Phase Modelling of Speech Signals

Epochs are instants of significant excitation of vocal-tract system in speech production process. In this paper, we attempt to extract information about epochs from phase spectra of speech signals. The phase spectrum of speech is modelled as the response of an allpass (AP) filter, and the resulting error signal is used for epoch extraction. The parameters of AP model are estimated by imposing sparsity constraints on the error signal. The error signal, thus obtained, exhibits prominent peaks at epoch locations. The epochal candidates obtained from the error signal are refined using a dynamic programming algorithm. The performance of the proposed method is consistent across genders and is comparable with the state-of-the-art methods.     

Color Characterization and Balancing by a Nonlinear Line Attractor Network for Image Enhancement

A novel method to map high dynamic range scenes to low dynamic range images utilizing the concept of color characterization, enhancement, and balancing is described in this letter. Each pixel of the image is first characterized by extracting the relationship of the red, green, and blue components along with its corresponding neighbors using a nonlinear line attractor network to form an associative memory. Then, the illumination enhancement process is performed using a hyperbolic tangent function to provide dynamic range compression to each pixel in the image. The slope of the hyperbolic tangent function is controlled using a parameter that is determined by the local and global statistics of the image to facilitate the change of the intensity level. A color balancing process restores the original color characteristics of the image based on learned associative memory matrices which eliminate image distortion due to improper recombination of red, green and blue components after enhancement. Experiments conducted on images captured at extremely uneven lighting environments show that the proposed method outperforms other image enhancement algorithms.     

Characterization of the Hot Deformation Behavior and Microstructure Evolution of a New γ-γ′ Strengthened Cobalt-Based Superalloy

Recently, cobalt-based γ-γ′ microstructured superalloys have attracted attention. However, studies on their processing behavior [i.e., processing maps (the variation of strain rate sensitivity (m) with temperature)] are limited. Thus, the high-temperature flow behavior of a γ-γ′ Co-30Ni-10Al-5Mo-2Ta-2Ti-5Cr (at. pct) superalloy was investigated using isothermal compression tests between 1348 and 1498 K at strain rates from 0.001 to 10 s⁻¹. The m contour map was generated using the experimental flow stress values, which were used to locate the optimum hot workability and desired microstructural processing range. A strong dependence of m on the deformation parameters (temperature, strain rate, and strain) was observed. A maximum m value of around 0.3 at 1460 K to 1498 K and strain rates of 0.01 to 0.5 s⁻¹ was found. The deformed samples show a fully recrystallized microstructure at high m. Unstable domains showed the formation of cavities at the grain boundary triple points and cracks along the grain boundaries at high strain rates (1 to 10 s⁻¹), corresponding to m < 0.10. A constitutive model was developed using an Arrhenius hyperbolic sine function, yielding an apparent activation energy of 540 ± 30 kJ mol⁻¹ for hot deformation. This study indicates reasonable formability under certain conditions below the solvus, thus opening possibilities for further thermomechanical treatment.

     

Influence of machining parameters and new nano-coated tool on drilling performance of CFRP/Aluminium sandwich

Drilling and fastening of hybrid materials in one-shot operation reduces cycle time of assembly of aerospace structures. One of the most common problems encountered in automatic drilling and riveting of multimaterial is that the continuous chips curl up on the body of the tool. Drilling of carbon fiber reinforced plastic (CFRP) is manageable, but when the minute drill hits the aluminium (Al) or titanium (Ti), the hot and continuous chips produced during machining considerably damage the CFRP hole. This study aims to solve this problem by employing nano-coated drills on multimaterial made of CFRP and aluminium alloy. The influence of cutting parameters on the quality of the holes, chip formation and tool wear were also analyzed. Two types of tungsten carbide drills were used for the present study, one with nano-coating and the other, without nano coating. The experimental results indicated that the shape and the size of the chips are strongly influenced by feed rate. The thrust force generated during drilling of the composite plate with coated drills was 10–15% lesser when compared to that generated during drilling with uncoated drills; similarly, the thrust force in the aluminium alloy was 50% lesser with coated drills when compared to thrust force generated without coated drills. Thus, the use of nano-coated drills significantly reduced the surface roughness and thrust force when compared with uncoated tools.