Supervised Single Channel Speech Enhancement Based on Stationary Wavelet Transforms and Non-negative Matrix Factorization with Concatenated Framing Process and Subband Smooth Ratio Mask

Journal of Signal Processing Systems - In this paper, we propose a novel single channel speech enhancement approach that takes up the Stationary Wavelet Transform (SWT) and Nonnegative Matrix...     

Missing data analysis and homogeneity test for Turkish precipitation series

In this study, missing value analysis and homogeneity tests were conducted for 267 precipitation stations throughout Turkey. For this purpose, the monthly and annual total precipitation records at stations operated by Turkish State Meteorological Service (DMI) from 1968 to 1998 were considered. In these stations, precipitation records for each month was investigated separately and the stations with missing values for too many years were eliminated. The missing values of the stations were completed by Expectation Maximization (EM) method by using the precipitation records of the nearest gauging station. In this analysis, 38 stations were eliminated because they had missing values for more than 5 years, 161 stations had no missing values and missing precipitation values were completed in the remaining 68 stations. By this analysis, annual total precipitation data were obtained by using the monthly values. These data should be hydrologically and statistically reliable for later hydrological, meteorological, climate change modelling and forecasting studies. For this reason, Standard Normal Homogeneity Test (SNHT), (Swed-Eisenhart) Runs Test and Pettitt homogeneity tests were applied for the annual total precipitation data at 229 gauging stations from 1968 to 1998. The results of each of the testing methods were evaluated separately at a significance level of 95% and the inhomogeneous years were determined. With the application of the aforementioned methods, inhomogeneity was detected at 50 stations of which the natural structure was deteriorated and 179 stations were found to be homogeneous.     

Mutasynthesis-derived myxalamids and origin of the isobutyryl-CoA starter unit of myxalamid B

Myxalamids are potent inhibitors of the eukaryotic electron transport chain produced by different myxobacteria. Here, we describe the identification of the myxalamid biosynthesis gene cluster from Myxococcus xanthus. Additionally, new myxalamids (5-13) have been obtained by mutasynthesis from bkd mutants of M. xanthus and Stigmatella aurantiaca. Moreover, as these bkd mutants are still able to produce myxalamid B (2), the origin of the isobutyryl-CoA (IB-CoA) starter unit required for its biosynthesis has been determined. In a M. xanthus bkd mutant, IB-CoA originates from valine, but in S. aurantiaca this starter unit is derived from alpha-oxidation of iso-odd fatty acids, thereby connecting primary and secondary metabolism.     

A one-dimensional plug-flow model of a counter-current spray drying tower

A one-dimensional numerical model for a detergent slurry drying process in a counter-current spray drying tower is developed for the prediction of the gas and droplet/particle temperature profiles within the tower. The model accommodates droplets/particles over a range of sizes. A semi-empirical slurry droplet drying model is integrated with a counter-current tower simulation based on mass, energy and particulate phase momentum balances in order to calculate the drying rate and the particle residence time within the tower. The coupled first order ordinary differential equations for the two phases are solved numerically using the iterative shooting method in an algorithm developed within MATLAB. The predictions of the numerical model are compared with industrial pilot plant data. The results are found to vary significantly with the specified size distribution of the droplets. Despite the simplicity of the model in ignoring the coalescence, agglomeration, wall deposition and re-entrainment, the model gives reasonable agreement with the experimental data.     

Antibacterial responses of zinc oxide structures against Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pyogenes

The antibacterial responses of zinc oxide (ZnO) structures against Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes were investigated. Two ZnO powder samples, one with rod-like (ZnO-1) and the other with plate-like (ZnO-2) structures, were characterized for their morphological, structural, and optical properties. The rods were 30–120 nm in diameter, and the plates were 40–100 nm thick. XRD results revealed the wurtzite crystallinity of ZnO with average crystallite sizes of 33.72 (ZnO-1) and 39.25 (ZnO-2) nm. ZnO-2 possessed a relatively higher green photoluminescence than that of ZnO-1, suggesting a relatively higher amount of oxygen vacancies in ZnO-2 structures. Optical density measurements showed that both ZnO samples inhibited the growth of S. aureus, P. aeruginosa, and S. pyogenes by 29–98% after 24 h of treatment. The most dramatic growth inhibition was observed in S. pyogenes with 96% and 98% inhibition for ZnO-1 and ZnO-2, respectively, leading to a probable bactericidal phenomenon. The toxicological effect on S. pyogenes was probably due to the absence of catalase, making the bacteria vulnerable to the harmful reactive oxygen species (ROS) released by ZnO. ZnO-1 induced higher inhibition toward S. aureus and P. aeruginosa than that of ZnO-2 because of the smaller particle size of rod structures compared to plate and slab structures. The adhesion of ZnO particles on the membrane of bacteria could be the underlying cause of zinc toxicity effect towards the bacteria. ZnO-1 possessed larger surface area and provided higher amount of zinc atom, thereby inducing higher level of toxicity toward the bacteria. Two possible mechanisms were proposed to explain the inhibition of bacteria, namely, ROS toxicity toward cellular constituents and interaction of zinc with bacteria membrane through adhesion of ZnO particle. Several ZnO morphological-antibacterial correlations were presented in this work.     

Effect of light irradiation on esterification of oleic acid with ethanol catalyzed by immobilized Pseudomonas cepacia lipase

The present study demonstrates the effect of light irradiation on the esterification of oleic acid catalyzed by immobilized Pseudomonas cepacia lipase. The reaction rates of all the experiments under light irradiation were found to be higher than dark conditions. The kinetics of reactions supported the Ping‐Pong Bi‐Bi mechanism with dead end inhibition by both the alcohol and acid substrates. Moreover, circular dichroism (CD) spectroscopy was used to analyze the effect of light on lipase enzyme. The CD spectroscopic studies confirmed that the conformational changes in the secondary structure of the lipase enzyme increased the reaction rate of light‐illuminated experiments, which might have opened up the active sites of enzymes and thus, resulted in higher reaction rates compared to dark reactions. These results have successfully demonstrated that the light illumination positively influenced the rate of P. cepacia enzyme‐catalyzed esterification reactions.     

Effect of Crystallization Conditions on the Metastable Zone Width and Nucleation Kinetics of p-Aminobenzoic Acid in Ethanol

A detailed knowledge of the metastable zone width (MSZW) and nucleation kinetics is vital for the design of batch cooling crystallization processes. Factors such as cooling rate and impeller speed affect the MSZW and nucleation kinetics. Crystallization and dissolution temperatures were measured as a function of cooling rate and impeller speed during the batch cooling crystallization of p-aminobenzoic acid (pABA) from ethanol in a 0.5-L stirred-tank crystallizer. The polythermal experimental data were analyzed using the Nyvlt and first principles-based Kashchiev-Borissova-Hammond-Roberts (KBHR) methods. In all experimental cases, the latter model revealed that the nucleation process of pABA in ethanol was dominated by an instantaneous nucleation mechanism. The Nyvlt and KBHR analyses delivered a range of parameter values associated with a power-law model describing the nucleation rate as well as the concentration of nuclei.     

Determination of threshold exposure and intensity for recording holograms in thick green-sensitive acrylamide-based photopolymer

For optical data storage applications, it is essential to determine the lowest intensity (also known as threshold intensity) below or at which no data page or grating can be recorded in the photosensitive material, as this in turn determines the data capacity of the material. Here, experiments were carried out to determine the threshold intensity below which the formation of a simple hologram--a holographic diffraction grating in a green-sensitized acrylamide-based photopolymer--is not possible. Two main parameters of the recording layers--dye concentration and thickness--were varied to study the influence of the density of the generated free radicals on the holographic properties of these layers. It was observed that a minimum concentration per unit volume of free radicals is required for efficient cross-linking of the created polymer chains and for recording a hologram. The threshold intensity below which no hologram can be recorded in the Erythrosin B sensitized layers with absorbance less than 0.16 was 50 μW/cm(2). The real-time diffraction efficiency was analyzed in the early stage of recording. It was determined that the minimum intensity required to obtain diffraction efficiency of 1% was 90 μW/cm(2), and the minimum required exposure was 8 mJ/cm(2). It was also determined that there is an optimum dye concentration of 1.5 × 10(-7) mol/L for effective recording above which no increase in the sensitivity of the layers is observed.     

Simple indoline based donor–acceptor dye for high efficiency dye-sensitized solar cells

A simple metal-free donor–acceptor type sensitizer U01, bearing strong electron donor indoline-triphenylamine was synthesized for panchromatic sensitization of TiO₂ nanocrystalline film. Photovoltaic properties of U01 showed remarkably enhanced light harvesting due to the presence of strong electron donor and robust structure. The new U01 sensitized solar cell exhibited a photovoltaic performance: a short-circuit photocurrent density (J_sc) of 10.70 mA cm⁻², an open-circuit photovoltage (V_oc) of 0.758 V and a fill factor (FF) of 0.74, corresponding to an overall conversion efficiency of 6.01% under standard global AM 1.5 solar light condition. Our results suggest that indoline-triphenylamine based robust D–A molecular architecture is a highly promising class of panchromatic sensitizers for improvement of the performance of dye-sensitized solar cells (DSCs).     

A study on the mechanical and electrical reliability of individual carbon nanotube field emission cathodes

Individual carbon nanotube (CNT) field emission characteristics present a number of advantages for potential applications in electron microscopy and electron beam lithography. Mechanical and electrical reliability of individual CNT cathodes, however, remains a challenge and thus device integration of these cathodes has been limited. In this work, we present an investigation into the reliability issues concerning individual CNT field emission cathodes. We also introduce and analyze the reliability of a novel individual CNT cathode. The cathode structure is composed of a multi-walled carbon nanotube (MWNT) attached by Joule heating to a nickel-coated Si microstructure. The junction of the CNT and the Si microstructure is mechanically and electrically robust to withstand the strong electric field conditions that are typical for field emission devices. An optimal Ni film coating of 25?nm on the Si microstructure is required for mechanical and electrical stability. Experimental current-voltage data for the new cathode structure definitively demonstrates carbon nanotube field emission. Additionally, we demonstrate that our new nanofabrication method is capable of producing sophisticated cathode structures that were previously not realizable, such as one consisting of two parallel MWNTs, with highly controlled CNT lengths with 40?nm accuracy and nanotube-to-nanotube separations of less than 10?μm.