Stimulation of negative magnetoresistance by an electric field and light in silicon doped with boron and manganese

It is experimentally ascertained that light stimulates the negative magnetoresistance observed in a high electric field in silicon doped with boron and manganese. The optimum conditions (the electric field, temperature, illumination, and resistivity of the material) for observation of the largest magnitude of negative magnetoresistance in (Si:B):Mn are determined. The dependence of the negative magnetoresistance on the concentration of compensating impurity is established.     

Spoken emotion recognition through optimum-path forest classification using glottal features

A new method for the recognition of spoken emotions is presented based on features of the glottal airflow signal. Its effectiveness is tested on the new optimum path classifier (OPF) as well as on six other previously established classification methods that included the Gaussian mixture model (GMM), support vector machine (SVM), artificial neural networks – multi layer perceptron (ANN-MLP), k-nearest neighbor rule (k-NN), Bayesian classifier (BC) and the C4.5 decision tree. The speech database used in this work was collected in an anechoic environment with ten speakers (5 M and 5 F) each speaking ten sentences in four different emotions: Happy, Angry, Sad, and Neutral. The glottal waveform was extracted from fluent speech via inverse filtering. The investigated features included the glottal symmetry and MFCC vectors of various lengths both for the glottal and the corresponding speech signal. Experimental results indicate that best performance is obtained for the glottal-only features with SVM and OPF generally providing the highest recognition rates, while for GMM or the combination of glottal and speech features performance was relatively inferior. For this text dependent, multi speaker task the top performing classifiers achieved perfect recognition rates for the case of 6th order glottal MFCCs.     

Elastic–plastic response of structural foams subjected to localized static loads

Structural foams are increasingly used in engineering applications where high strength and low weight are important. They are used also as energy absorbers. Sandwich structures are a typical area for application of structural foams (as core materials). In a sandwich structure, the core transfers the transverse forces as shear stresses and supports the face sheets against buckling and wrinkling. The structural foams are notoriously sensitive to failure by the application of localized surface loads. Thus, the proper design requires an understanding of the mechanical response of the foam materials to localized external loads.In this paper, the elastic–plastic behavior of closed-cell cellular foams subjected to point and line loads is investigated both experimentally and numerically. Two types of Divinicell foam (H60 and H100) are studied. A finite element modeling procedure is developed using the ABAQUS package. Both plane and axisymmetric formulations for local indentations by rigid bodies are considered. The plastic behavior is described using the *CRUSHABLE FOAM HARDENING material model. This model is calibrated using experimental curves from uniaxial compression tests. Geometrical non-linearity is also taken into account. Both indentation and unloading phases are modeled. Static indentation tests of foam panels and beams are performed using spherical and cylindrical indentors, respectively. A comparison of indentation response obtained from the numerical analysis and from the tests is carried out. A good agreement between the modeling and the experimental data is achieved. In perspective view, the present investigation can contribute towards the development of a damage tolerance methodology for rigid foams.     

Interaction between multiply charged manganese nanoclusters and sulfur atoms in silicon

We have studied the interaction of manganese nanoclusters with sulfur atoms in silicon. The results indicate that both simultaneous and sequential codoping with manganese and sulfur has little effect on the electrical properties (resistivity, carrier mobility, and conductivity type) of silicon. There is no extrinsic photoconductivity in the IR spectral region, and the material has only a small positive magnetoresistance. According to electron paramagnetic resonance data, the material contains only atomic manganese. Sulfur atoms in the silicon lattice are assumed to facilitate the capture of doubly charged manganese interstitials (Mn²⁺) at negatively charged vacancies, resulting in the formation of a multicomponent impurity cluster of composition Si₂S²⁺Mn²⁻ in the silicon lattice throughout the crystal. The optimal thermal annealing conditions for the formation of such clusters are determined. The ability to produce Si₂S²⁺Mn²⁻ clusters with controlled concentration allows one to tailor the main fundamental parameters of silicon and opens up new possibilities for such materials in nano- and microelectronic device development.     

Investigation of the phase composition of accretions formed into WHB under flash smelting of copper concentrate

The phase composition of the depositions formed in the radiation section of the waste heat boiler utilizer (RS of WHB) after injecting sulphatizing flow in the volume of the off-gases from the uptake of flash smelting furnace for copper sulphide concentrate smelting was studied. With the help of X-ray diffraction (XRD), Reflected-light microscopy and Electron probe microanalysis (EPMA) of samples from the accretions, it was established that the main crystalline phases in the accretions were spinel, delafossite, cuprite and tenorite. The results from EPMA have shown that the spinel phase is with variable composition from cuprospinel to solid solution into the system Fe₃O₄-CuFe₂O₄-ZnFe₂O₄ (magnetite-cuprospinel-franklinite). Calculated on the basis of XRD and EPMA approximate formulae for the phases, identified in the samples from the accretions were the following: of the cuprospinel-(Cu_0.85²⁺Zn_0.09²⁺Fe_0.06²⁺)(Fe_1.87³⁺Al_0.10³⁺Si_0.03⁴⁺)O₄; of the spinel solid solution—(Cu_0.32²⁺Zn_0.36²⁺Fe_0.32²⁺)(Fe_1.81³⁺Al_0.19³⁺)O₄; Delafossite—Cu_1.07Fe_0.93O₂; cuprite—Cu_1.99Fe_0.02Si_0.01O and tenorite—Cu_0.993Fe_0.008O. The influence of the temperature on the sulphate formation processes of copper and iron oxides in the dust-gas flow was evaluated, based on experimental data and thermodynamic analysis of phase equilibriums in the systems Cu-S-O and Fe-S-O for the conditions, typical of the radiation section of the waste heat boiler (RS of WHB).     

Influence of mass transport on the performance of carbon gas-diffusion air electrodes in alkaline solution

The effect of mass transport on the electrochemical behaviour of carbon gas-diffusion air electrodes in alkaline solution was investigated on the basis of ΔE(i) curves. These curves are obtained by subtraction of potential values for an electrode operating with airE _air(i) from potential values for the same electrode operating with pure oxygenE _oxygen(i) at the same current densityi. Three different regions on these curves connected with different modes of mass transport are recognized. A model of the gas-diffusion air electrode which takes into account the diffusion of the gas, diffusion of the dissolved gas, electrochemical reaction and IR drop is used to explain the experimental results.     

Antibacterial and antifungal activities of selected microalgae and cyanobacteria

In vitro activity of nine cyanobacterial and ten microalgal newly isolated or culture collection strains against eight significant food‐borne pathogens has been evaluated and compared. Water extracts and culture liquids of Gloeocapsa sp. and Synechocystis sp. demonstrated the widest spectrum of activity with minimal inhibitory concentration (MIC) ranging from 1.56 to 12.5 mg mL^?1. Culture liquid of Anabaena sp. had the highest activity (MIC = 0.39 mg mL^?1) but only to Gram‐positive bacteria. Ethanol extracts and fatty acids from all cyanobacteria and microalgae were active against Streptococcus pyogenes and/or Staphylococcus aureus. The fatty acids of Synechocystis sp. inhibited the growth of Bacillus cereus, Escherichia coli and Candida albicans (MIC values of 2.5–1.25 mg mL^?1, respectively). Exopolysaccharides (EPS) of Gloeocapsa sp. were the sample that exhibited activity against all test pathogens with lowest MIC values (0.125–1 mg mL^?1). High activity with a narrower range of susceptible targets demonstrated the exopolysaccharides of Synechocystis sp. and Rhodella reticulata. Antimicrobial activity was proven for phycobiliproteins isolated from Synechocystis sp., Arthrospira fusiformis, Porphyridium aerugineum and Porphyridium cruentum, respectively. In conclusion Gloeocapsa sp. and Synechocystis sp. and especially their exopolysaccharides showed the most promising potential against the examined food pathogens.     

Interaction of radiation defects with nickel atom clusters in silicon

Based on infrared microscopic studies, we show that clusters of impurity nickel atoms are uniformly distributed over the entire volume of the silicon crystal; by varying the density of the clusters in silicon exposed to γ-radiation, it is possible to control the concentration of the electroactive atoms and the structure of the nickel clusters. It is shown that the presence of clusters in the lattice significantly increases the radiation resistance of the silicon.     

Low velocity localized impact study of cellular foams

This paper deals with low velocity impact behavior of two densities of ductile polyvinylchloride (PVC) foam manufactured by Divinicell. Low velocity impact tests are carried out on foam beam and panel specimens. A drop-weight rig is used to carry-out the impact tests. The test rig is equipped with a load cell connected to a data acquisition PC computer, which allows the most important dynamic and kinetic parameters, such as the contact force, load–time response, impactor velocity and energy to be measured. Post-impact creep response of the foam is also investigated. Finite element analyzes are also conducted to study the dynamic response of foam specimens subjected to a low velocity impact. The present paper contributes towards the development of a damage tolerance design approach for structural foams.     

Method for computing the milk losses from sterility in cows

An attempt was made to work out a method and establish the indices in calculating the losses of milk due to sterility in cows, along with recording the level of productivity and the duration of the period of sterility. The differences were established between: 1. The size of the average daily milk yield per normative day (a day of the period between calvings of 365 days) and that per day of the actual period between calvings. 2. The average daily milk yield per normative day and that per day of the period of sterility. The milk losses calculated in both ways gave almost comparable results. It is , therefore, suggested when calculating the losses due to sterility to use the established indices of milk losses per sterility day (Table 2) at a varying milkiness of the cows and a varying length of the period between calvings, resp., the period of sterility.