Effect of metal catalyst thermal expansion on thermal stability of synthetic diamonds

Thermal stability of synthetic diamonds grown in various metallic solutions in terms of their residual strength after thermal loading is studied. The micromechanical, cohesive zone model of crack initiation and propagation in the diamond crystal in a vicinity of metal inclusion has been developed. The inclusion-diamond thermal expansion mismatch is found to be a key factor responsible for the strength reduction of diamond crystals after high-temperature treatment. The results of computer simulation satisfactory correlate with the available experimental data.     

Reduction of Escherichia coli O157:H7 population on baby spinach leaves by liquid sanitizers

The effectiveness of various liquid sanitizers and methods of application against Escherichia coli on baby spinach was investigated. Inoculated spinach was treated with (i) Pro‐San L (commercially prepared solution containing 0.66% citric acid, 0.036% sodium dodecyl sulfate (SDS); (ii) chlorine solution (200 ppm), alone or with addition of 0.036% SDS; and (iii) aqueous solution of 0.66% levulinic acid with 0.036% SDS. Population reduction in response to these treatments ranged between 2.1 and 2.8 log CFU/g. No significant difference (p > .05) was found among tested sanitizers in microbial count reduction. Spraying, dipping, and “dry” vacuum impregnation methods of Pro‐San L application were compared. Dipping was the most effective in reducing E. coli O157:H7 population (4.4 log CFU/g reduction). Dry vacuum impregnation was less effective (3.3 log CFU/g reduction) and caused damage to the produce. The effectiveness of spray Pro‐San L application and holding for prolonged time (up to 3 days) was also evaluated. However, increasing time of exposure to organic acid sanitizer did not increase sanitizing effectiveness and led to progressive damage of spinach leaves.     

Blue, green and red emissive silver nanoclusters formed in organic solvents

Strongly luminescent silver nanoclusters with tunable emission are directly synthesized in organic polar and apolar solvents. We show that an amphiphilic polystyrene-block-poly(methacrylic acid) block copolymer can be universally used as their support medium. A remarkable similarity in spectroscopic properties is observed between these clusters and charge-transfer organic dyes.     

基于BP神经网络算法的Ti-6Al-4V激光NiAl-VC合金化的工艺研究

为了进一步提高Ti-6Al-4V的性能,以满足其在工程中更广泛的运用,研究了在Ti-6Al-4V激光NiAl-VC合金化的工艺。以改变激光功率、激光扫描速度和粉末质量含量比例进行了工艺实验,采用BP神经网络(BP-NN)算法,建立了合金化层性能与工艺参数之间的关系模型,并通过验证实验表明预测效果良好,具有可行性。采用BP-NN算法进行了模拟实验,分析了不同工艺参数条件对合金化层深度、宽度、平均硬度、最高硬度的影响规律。本研究对Ti-6Al-4V激光NiAl-VC合金化的实践应用具有指导意义和参考价值。     

Morphology, optical, and photoelectrochemical properties of electrodeposited nanocrystalline ZnO films sensitized with Cd x Zn1−x S nanoparticles

Nanocrystalline ITO/ZnO films formed by porous zinc oxide microplatelets 1–3 μm in size and 100–200 nm in thickness, which consist of 30–50 nm ZnO crystallites, were sensitized to visible light by Cd _x Zn_1?x S nanocrystals deposited using the method of successive ionic layer adsorption and reaction (SILAR). The composition of Cd _x Zn_1?x S nanocrystals as well as the dependence between molar Cd(II) fraction in the films and the ratio of cadmium and zinc nitrate concentrations in solutions used for the SILAR procedure were determined by a combination of electron, Raman, and energy-dispersive X-ray spectroscopies. The photovoltage observed at illumination of the ITO/ZnO/Cd _x Zn_1?x S heterostructures by white light (λ >400 nm) in aqueous Na₂S solution increases with a decrease of Cd(II) content proportionally to an increment in the conduction band potential of the Cd _x Zn_1?x S nanocrystals. The photocurrent density normalized to the light absorbance of the ITO/ZnO/Cd _x Zn_1?x S films increases by a factor of around four when the conduction band potential of Cd _x Zn_1?x S nanocrystals grows by 220 mV as a result of Cd(II) fraction changing from 1.0 to 0.62–0.67. The results show that Cd _x Zn_1?x S solid solutions are more advantageous sensitizers for the short-wavelength part of the sensitivity window of the liquid-junction solar cells (400–450 nm) than conventionally used cadmium sulfide.     

Effect of Deformation Heating on Microstructure Evolution During Hot Forging of Ti-6Al-4V

Metallurgical and Materials Transactions A - The effect of deformation heating on microstructure evolution during hot forging of Ti-6Al-4V was established. For this purpose, right-circular...     

Local dimensionality reduction and supervised learning within natural clusters for biomedical data analysis.

Inductive learning systems were successfully applied in a number of medical domains. Nevertheless, the effective use of these systems often requires data preprocessing before applying a learning algorithm. This is especially important for multidimensional heterogeneous data presented by a large number of features of different types. Dimensionality reduction (DR) is one commonly applied approach. The goal of this paper is to study the impact of natural clustering--clustering according to expert domain knowledge--on DR for supervised learning (SL) in the area of antibiotic resistance. We compare several data-mining strategies that apply DR by means of feature extraction or feature selection with subsequent SL on microbiological data. The results of our study show that local DR within natural clusters may result in better representation for SL in comparison with the global DR on the whole data.     

EPR-Characterization of Carbon Inclusions in Boron Carbide

In boron carbide, the dependence of EPR line width (ΔB) with g = 2.0028 on the contents of free carbon, c_C, is used to determine the surface-to-volume ratio ( S / V ) of free carbon inclusions. Consecutive reduction of c_C was conducted by a method of low-vacuum oxidation at a range of temperatures. The amount of a free carbon (a graphite phase) in samples was measured by X-ray. Analysis of changes in ΔB (c_C) has shown that free carbon inclusions at the surface layer of polycrystalline boron carbide particles has S / V two times smaller than that of free carbon inclusions in the interior of polycrystalline boron carbide.     

Methods for detecting the mobility of trace elements during medium-temperature pyrolysis

The mobility (volatility) of trace elements in coal during pyrolysis has been studied for distances of up to 40 cm between the coal and the trace element collector, which was graphite or a baffled solvent trap. Nineteen elements not previously recorded as mobile were detected.     

Hydrodynamic Cell Model: General Formulation and Comparative Analysis of Different Approaches

This paper is concerned with the Cell Model method of addressing hydrodynamic flow through system of solid particles. The starting point of the analysis is the general problem formulation intended for describing a pressure driven flow through a diaphragm which can be considered as a set of representative cells having arbitrary shape and containing any number of particles. Using the general problem formulation, the hydrodynamic field inside an individual representative cell is interrelated with the applied pressure difference and the external flow velocity. To this end, four relationships containing integrals over the outer boundary of a representative cell are derived in the paper. Assuming that the representative cell is a sphere containing a single particle in the centre, the derived general relationships are transformed into outer cell boundary conditions employed in the literature by different authors. The general number of the obtained outer boundary conditions is more than the required number. Accordingly, by choosing different sets of the outer boundary conditions, different models are considered and compared with each other and with the results obtained by others for regular particle arrays. The common and different features of the hydrodynamic and electrodynamic versions of the Cell Model approaches are analyzed. Finally, it is discussed which version of the cell model gives the best approximation while describing pressure and electrically driven flows through a diaphragm and sedimentation of particles.