A new simulation model for inhomogeneous Au/<Emphasis Type="Italic">n</Emphasis>-GaN structure

The larger the device area, the more difficult to carry on homogeneity during the fabrication and following treatments. Structural inhomogeneity may indicate themselves in variations in local electronic device parameters. Electrical current through the potential barriers is exponentially sensitive to the local device parameters and its fluctuations in the Schottky devices. A new simulation program is developed to describe a relation between multiple, random barrier heights and current-voltage characteristics of the Schottky device. We model the barrier height inhomogeneity in terms of random microcells connected in parallel, which have different barrier height values. Analyzing the integral of the simulated light current-voltage curves show that fluctuations of the local barrier height result in a degradation of the open circuit voltage, fill factor and in consequence, of the over all power conversation efficiency. The implementation described here is quite general and can be used to simulate any device parameter fluctuations in the Schottky devices.     

Sol–gel synthesis of Cu0.9Zn0.05M0.05O (M = Cr,Co, Cd) nanocrystals for removal of pollutant dyes and bacterial inactivation

Journal of Materials Science: Materials in Electronics - In this work, we focus on the synthesis of Cu0.95Zn0.05O and Cu0.9Zn0.05M0.05O (M?=?Cr, Co, Cd) nanocrystals by employing...     

Lexicon-based approach outperforms Supervised Machine Learning approach for Urdu Sentiment Analysis in multiple domains

Web is facilitating people to express their views and opinions on different topics through reviews and blogs. Effective advantages can be reaped from these reviews and blogs by fusing the sentiment knowledge. In this research, Sentiment Analysis of Urdu blogs from multiple domains is done by using the two widely used approaches i.e. the Lexicon-based approach and the Supervised Machine Learning approach. Three well known classifiers i.e. Support Vector Machine, Decision Tree and K Nearest Neighbor are used in case of Supervised Machine Learning approach whereas a wide coverage Urdu Sentiment Lexicon and an efficient Urdu Sentiment Analyzer are used in Lexicon-based approach. In both the approaches the information are fused from two sources to successfully perform Sentiment Analysis. In case of Lexicon-based approach, the two sources are the wide coverage Urdu Sentiment Lexicon and the efficient Urdu Sentiment Analyzer. In case of Supervised Machine Learning approach, the two sources are the un-annotated data and annotated data along with important attributes. After performing Sentiment Analysis using both the approaches, the results are observed carefully and on the basis of experiments performed in this research, it is concluded that the Lexicon-based approach outperforms Supervised Machine Learning approach not only in terms of Accuracy, Precision, Recall and F-measure but also in terms of economy of time and efforts used.     

Electric and Dielectric Properties of Cr-Ga Substituted BaM Hexaferrites for High-Frequency Applications

Single-phase Cr-Ga-substituted BaM hexaferrites with chemical formula BaCr _x Ga _x Fe_12?2x O₁₉ (x = 0.0, 0.1, 0.2, 0.3, and 0.4) are synthesized by means of a sol-gel autocombustion technique. Cold isostatic-pressing technique has been used to press the as-prepared powders into pellets. Room-temperature DC resistivity enhances with the substitution of Cr-Ga contents. The temperature dependence of the DC resistivity shows the semiconducting nature. The dielectric constant and dielectric tangent loss decrease, while AC conductivity increases with the increasing applied field frequency in the range of 1 MHz-3 GHz consistent with Koop’s theory and Maxwell-Wagner’s bi-layer model. The magnetic loss enhances, while the reflection coefficient decreases with the increase of frequency as well as with the increase of Cr-Ga contents. Owing to improved properties, these materials are potential candidates for high-frequency applications in GHz range.     

Effects of Heat-Treatment Time on the Structural, Dielectric, Electrical, and Magnetic Properties of BaM Hexaferrite

M-type hexaferrite (BaFe₁₂O₁₉) powders have been synthesized by means of the sol-gel autocombustion technique and is heat treated at 1000 °C for different times (t = 1, 2, 3, and 4 h). Differential scanning calorimetry and thermogravimetric analyses are carried out to observe the weight loss and transformation of different phases during heat treatment. X-Ray diffraction patterns of the sample heat treated for 4 h confirms the formation of single phase M-type hexaferrite. The dielectric parameters and ac conductivity (σ_ac) are measured in the high frequency range 1 MHz-3 GHz. The dielectric properties and ac conductivity are based on the space charge polarization according to the Maxwell-Wagner two-layer model and the Koop’s phenomenological theory. The dielectric constant (ε′) and dielectric loss (tan δ) decrease, while ac conductivity enhances with the increase of frequency. The room temperature DC electrical resistivity of the sample heat treated for 2 h enhances up to 2.93 × 10⁹ (Ω-cm) and attributed to the migration of Fe²⁺ ions to the neighboring tetrahedral sites and lowering the Fe³⁺ contents on the octahedral sites. The temperature-dependent DC resistivity of samples shows a normal semiconducting behavior. The saturation magnetization, magnetic moment, and coercivity of the samples are observed to enhance with the increase of heat-treatment time. Owing to these qualities, the synthesized materials may be considered useful for high frequency applications, recording media, and permanent magnets.     

Enhancement in the photocatalytic and antimicrobial properties of ZnO nanoparticles by structural variations and energy bandgap tuning through Fe and Co co-doping

In this study, pure ZnO and iron (Fe) and cobalt (Co) co-doped ZnO nanoparticles were synthesized by varying Fe and Co concentrations using the co-precipitation method. The physical properties of as-prepared samples were investigated through XRD, FTIR, SEM, and UV–vis spectroscopy. X-ray diffraction confirmed the strong influence of Fe and Co ions on structural parameters without disturbing the basic ZnO hexagonal structure. The microstructural study was executed by using the Scherrer, W–H, and SSP methods. FTIR confirmed the presence of Zn–O, and Zn–M–O (M = Fe, Co) vibrational modes, which further confirmed the successful incorporation of dopants ions. The energy bandgap (E_g) extracted from UV–vis spectra has shown red-shift (3.37–2.7 eV) for decreasing Fe contents, whereas blue-shift (3.37–3.39 eV) for increasing Co concentration. SEM was used to investigate surface morphology, which represents the high rate of agglomeration. The photocatalytic test was performed on grown samples against various dyes and also observed the effects of varying concentrations of Fe and Co ions. The maximum degradation efficiency (98.8%) at 6%Fe and 4%Co under direct sunlight in 60 min against methylene blue (MB) was achieved. The photocatalytic activity of optimized concentration (6%Fe and 4%Co) was further tested against cresol red (CR), methyl orange (MO), safranin-O (SO), rhodamine-B (RhB), and methyl red (MR) dyes. The maximum degradation efficiency against MR dye (96.0%) was observed. The antibacterial test against Staphylococcus aureus and Klebsiella pneumoniae bacterial strains have shown that co-doped ZnO nanoparticles have a higher activity as compared to pristine ZnO, and furthermore, the sample with 6%Fe and 4%Co concentration exposed the highest antibacterial actively for both bacterial strains.     

THERMAL REACTIVITIES OF SOME TURKISH LIGNITES

Abstract

A DTA study has been made to investigate the thermal reactivities of five Turkish lignites (Elbistan, Ilgin, Karliova, Xangal, Yatagan) in an air atmosphere. The coal samples exhibited thermal reactivity at temperatures starting from 20 °C and continuing up to 671 °C. Endothermic peaks were observed at the lower end of the temperature range, the highest endothermic peak temperature being 146°C for Elbistan lignite. Exothermic peaks appeared at around 260, 360 and 600 °C. These temperatures are considered to signify the release and combustion of single benzene ring structures and combustion of condensed aromatic rings respectively. Corresponding stages are observed in the TGA traces. After correcting for differences in methodology, the overall heat effects measured by DTA are within greater than 90% of the calorific values of the coal samples determined by bomb calorimetry.     

Constitutive modeling of Leighton Buzzard Sands using genetic programming

This paper investigates the results of laboratory experiments and numerical simulations conducted to examine the behavior of mixtures composed of coarse (i.e. Leighton Buzzard Sand fraction B) and fine (i.e. Leighton Buzzard Sand fraction E) sand particles. Emphasis was placed on assessing the role of fines content in mixture and strain level on the deviatoric stress and pore water pressure generation using experimental (i.e. Triaxial testing) and numerical approaches (i.e. genetic programming, GP). The experimental database used for GP modeling is based on a laboratory study of the properties of saturated coarse and fine sand mixtures with various mix ratios under a 100 kPa effective stresses in a 100 mm diameter conventional triaxial testing apparatus. Experimental results show that coarse–fine sand mixtures exhibit clay-like behavior due to particle–particle effects with the increase in fines content. It is shown that GP modeling of coarse–fine sand mixtures is observed to be quite satisfactory. The results have implications in the design of compressible particulate systems and in the development of prediction tools for the field performance coarse–fine sands.     

Susceptibility to the biological effects of polyaromatic hydrocarbons is influenced by genes of the major histocompatibility complex

Polyaromatic hydrocarbons are ubiquitous environmental chemicals that are important mutagens and carcinogens. The purpose of this study was to determine whether genes within the major histocompatibility complex (MHC) influence their biological activities. Cell-mediated immunity to dimethylbenz(a)anthracene (DMBA) was investigated in congenic strains of mice. On three different backgrounds, H-2(k) and H-2(a) haplotype mice developed significantly greater contact-hypersensitivity responses to DMBA than H-2(b), H-2(d), and H-2(s) mice. In B10.A(R1) mice, which are Kk and Id, a vigorous contact-hypersensitivity response was present, indicating that the response was governed by class I, rather than class II, MHC genes. C3H/HeN (H-2(k)) and C3H.SW (H-2(s)) strains were also compared for the development of skin tumors and the persistence of DMBA-DNA adducts. When subjected to a DMBA initiation, phorbol 12-tetradecanoate 13-acetate (TPA)-promotion skin-tumorigenesis protocol, C3H/HeN mice, (which develop cell-mediated immunity to DMBA) were found to have significantly fewer tumors than C3H.SW mice (a strain that failed to develop a cell-mediated immune response to DMBA). DMBA-DNA adducts were removed more rapidly in C3H/HeN than in C3H.SW mice. The results indicate that genes within the MHC play an important role in several of the biological activities of carcinogenic polyaromatic hydrocarbons. The observations are consistent with the hypothesis that cell-mediated immunity to chemical carcinogens serves to protect individuals by removing mutant cells before they can evolve into clinically apparent neoplasms.