Application of the dual-tree wavelet transform for digital filtering of noisy audio signals

The problem of refinement of the quality of filtering of noisy audio signals with the help of the methods based on a discrete wavelet transform with real bases and a dual-tree (complex) wavelet transform using analytical wavelets as basis functions is considered. Test examples and processing of experimental data have shown that, in the case of the optimum selection of the threshold level, the approach using the dual-tree wavelet transform ensures the minimum signal reconstruction error after correction of wavelet coefficients.     

Digital filtering of noisy data concerned with the effect of the threshold level and choice of a wavelet

The problem of digital wavelet filtering of noisy data is considered. The results are comparatively analyzed when the threshold function is specified in different ways for wavelet transformation coefficients. The influence of the choice of the wavelet basis on the efficiency of the noise removal is studied. It is shown that the minimum filtering error is in most cases provided when the soft variant of the threshold function introduction is introduced.     

Assessment of the effect of N-oxide group in a new high-performance energetic tetrazine derivative on its physicochemical and thermodynamic properties,sensitivity, and combustion and detonation performance

Chemistry of Heterocyclic Compounds - This work uses density functional theory and suitable predictive methods to assess the effect of N-oxide group in 1,2-bis(6-nitro-1,2,4,5-tetrazin-3-yl)diazene...     

Evaluation of Surface Active Properties and Voltammetric Characterizations of Some New Anionic Copolymer Surfactants

The onset of micelles formations critical micelle concentration, diffusion coefficients as well as particle sizes for some new synthesized anionic copolymer surfactants PSA_4a, PSA_4b, and PSA_4c, were determined and discussed. Three different electrochemical techniques such as cyclic voltammetry (CV), rotating disk voltammetry (RDV), and chronocoulometry (CC) were used in this investigation. The voltammetry of electroactive hydrophobic probe ferrocene solubilized surfactants was investigated in aqueous buffer carbonate solutions of pH 10. The CMC for each PSA_4a, PSA_4b, and PSA_4c, was found to be 3.20 × 10^?4, 4.60 × 10^?4 and 6.30 × 10^?4 M, respectively, using both CV and RDV techniques. The amount of adsorption contribution of ferrocene solubilized surfactants at the glassy carbon electrode was determined from chronocoulometric measurements and it was found in the range from (1.4 to 2.7) × 10^?15 M. The apparent diffusion coefficients were estimated from RDV measurements and the real micelles diffusion coefficients were obtained. Re-quilibrium considerations of ferrocene probe kinetics at the electrode surface were treated according to two different modes of slow- and fast-kinetics. The corrected diffusion coefficient values showed constancy at (5.3 ± 0.1) × 10^?7, (4.8 ± 0.1) × 10^?7, and (3.6 ± 0.4) × 10^?7 cm²/sec for PSA_4a, PSA_4b, and PSA_4c, respectively in the concentration range from 20 to 200 mM. The morphological features of anionic copolymeric surfactants PSA_4a, PSA_4b, and PSA_4c, micelles showed globular self-assembled structure.     

Studies on the chemical constituents of Phyllanthus emblica

Phytochemical investigations on Phyllanthus emblica have resulted in the isolation of the two new flavonoids, kaempferol-3-O-alpha-L-(6'-methyl)-rhamnopyranoside (1) and kaempferol-3-O-alpha-L-(6'-ethyl)-rhamnopyranoside (2). Their structures were determined on the basis of extensive spectroscopic studies including 2D-NMR experiments.     

Optimization of Nanofluidic Devices for Geometry-Induced Electrostatic Trapping

Nanoparticle trapping in a nanofluidic device utilizing geometry-induced electrostatic (GIE) potential trap is an efficient and robust way to perform nano‑object confinement and single particle studies. The GIE‑trapping is a passive method that solely depends on the device geometry and device-particle surface interaction. Therefore, optimization of a nanofluidic device based on experimental requirements, helps to achieve stiffer single-particle trapping. The efficiency of a GIE‑trapping device is defined in terms of residence time and trapping stiffness of the nanoparticle inside a potential trap. The present study reveals all crucial parameters that affect the device efficiency, particle trapping stiffness, and particle residence time. Furthermore, the trends of particle trapping stiffness are presented as a function of crucial parameters and demonstrate two variants of simulations to estimate the particle trapping efficiency: (a) using charged particle, and (b) using point charge approximation. Simulations with charged particle give more realistic values related to particle trapping whereas simulations with point charge approximation is a faster approach which gives approximate values and a guideline for more rigorous simulations. The results demonstrate a good agreement with experimental observations and hold the key for future developments in this field, wherein a device geometry can be very precisely optimized.     

环糊精复合薄膜光波导元件的气敏性研究

采用旋转甩涂法在钾离子(K+)交换玻璃光波导表面制备了聚乙烯吡咯烷酮(PVP)-环糊精复合薄膜,研制了PVP-环糊精薄膜/K+交换玻璃光波导传感元件,并对挥发性有机气体进行了检测。该气敏元件对苯乙烯和二甲苯具有较好的响应,并能够检测到体积比为1×10-6的苯乙烯和1×10-5的二甲苯。还具有响应及恢复速度快、容易制备等特点。     

Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

In this study, waste tire dust is recycled as filler and blended with ethylene-propylene diene monomer (EPDM) rubber. Three different polyfuntional monomers (PFMs) are incorporated into the standard formulation and irradiated under electron beam at different doses up to maximum of 100 kGy. The combined effects of PFMs and absorbed dose on the physical properties of EPDM/WTD blend are measured and compared with sulfur crosslinked formulation. Thermogravimetric analysis showed that radiation developed better crosslinked network with higher thermal stability than sulfur crosslinked structure. The physical properties of radiation crosslinked blend are similar to the sulfur crosslinked blend. The absence of toxic chemicals/additives in radiation crosslinked blends made them an ideal candidate for many applications such as roof sealing sheets, water retention pond, playground mat, sealing profile for windows etc.     

The Effect of Heat Treatment on Structural and Multiferroic Properties of Phase-Pure BiFeO3

Phase-pure multiferroic BiFeO₃ (BFO) was prepared by the coprecipitation technique using diverse precursors bismuth oxide at temperature as low as 400°C. The dependence of structural, microstructural, thermal, electrical (AC and DC), and magnetic properties on sintering temperature was systematically investigated. Uniaxially pressed samples (Ø8 mm) were sintered in air at 500°C to 800°C for 4 h. X-ray diffraction analysis was used to determine the amorphous and perovskite nature of as-synthesized and calcined/sintered samples, respectively. The crystallite size of sintered powders increased from 47 nm to 67 nm. Scanning electron microscopy showed grain growth during sintering, which improved intergranular connectivity and decreased porosity in the samples. The ferroelectric to paraelectric Curie transition temperature (T _C) of pure BFO powder was detected by differential scanning calorimetry analysis and found to be 820°C ± 1°C. The samples exhibited high AC resistivity and dielectric constant, and low loss tangent values. The samples exhibited weak ferromagnetic behavior with an unsaturated magnetization versus magnetic field hysteresis loop at room temperature. Ferroelectric behavior and variation in remnant polarization and coercivity were observed from polarization versus electric field loops. Enhanced capacitance in the magnetic field revealed the magnetoelectric effect in the samples.