A Mathematical Model for the Calculation of the Adhesion of a Flame Sprayed Coating of Aluminum on S 235 JR Steel

In this work the method of response surfaces was used for the purpose of drawing up a mathematical model for the calculation (forecasting) of the adhesion of a flame sprayed coating of powdered aluminum on S 235 JR steel. Experimental work was conducted according to a fractional central-composite design at three levels. The adhesion of the coatings made with combinations of input parameters of the procedure according to the experiment plan mentioned is measured in line with the EN 582 standard. A mathematical model was derived describing the dependence of the experimentally obtained adhesion values on the input parameters of the procedure. The possibility of analyzing the influence of the parameters on the adhesion for a certain combination of input parameters has been presented with the use of perturbation plots.     

Influence of T4 Heat Treatment on Tribological Behavior of Za27 Alloy Under Lubricated Sliding Condition

The effects of heat treatment on the microstructure, hardness, tensile properties, and tribological behavior of ZA27 alloy were examined. The alloys were prepared by conventional melting and casting route. The heat treatment of samples included the heating up to 370 °C for 3 or 5 h, quenching in water, and natural aging. Lubricated sliding wear test were conducted on as-cast and heat-treated ZA27 samples using block-on-disc machine. The friction and wear behavior of alloys were tested in contact with steel discs using combinations of three levels of load (10, 30, and 50 N) and three levels of linear sliding speeds (0.26, 0.50, and 1.00 m/s). To determine the wear mechanisms, the worn surfaces of the samples were examined by scanning electron microscopy (SEM). The heat treatment resulted in reduction in the hardness and tensile strength but increase in elongation. The heat-treated alloy samples attained improved tribological behavior over the as-cast ones, under all combinations of sliding speeds and contact loads. The rate of improvement increased with duration of solutionizing process before quenching in water. Obtained tribological results were related to the effects of heat treatment on microstructure changes of alloy.     

Aerodynamic design and analysis of a small-scale vertical axis wind turbine

Small-scale vertical axis wind turbines are regarded today as an attractive source of green energy, still insufficiently implemented and tested. This paper presents a fast design methodology of such a VAWT, in terms of choosing its main parameters: airfoil, rotor diameter and solidity. For obtaining generated power of each considered geometrical model at different undisturbed wind velocities and rotor angular velocities two models were used — momentum and vortex-wake model, combined with experimentally measured airfoil data (airfoil lift and drag coefficients). Even though the former model is simpler, it is the most utilized model, known to provide good results in stationary working regimes. Both models still present fairly accurate and fast tools for computation and optimization, particularly useful in the phase of conceptual design. In this research, the use of the momentum model resulted in determination of the maximal power coefficient, optimal- and minimal freestream velocity for every considered VAWT model. From these output parameters, a selection of the optimal geometric model was done, and a more detailed transient analysis and flow representation around the selected solution was obtained by the vortex-wake model. The results obtained by the two used computational models coincide satisfactorily.     

Application of fuzzy logic for evaluation of the level of social acceptance of waste treatment

The social aspect is very important in sustainability assessment of waste treatment technique, as well as making decision on their application and planning. In recent years, it is becoming evident that a waste treatment technique, which ignores social aspects, is doomed to failure. The most commonly used social indicators are: number of jobs created, level of social acceptance, public knowledge, public health etc. The most of them are qualitative and measuring the sustainability and quantifying the social dimension of sustainability are difficult tasks. This paper presents the application of fuzzy logic for evaluating the social indicator—level of social acceptance. The fuzzy set theory and fuzzy logic were used to develop a model for the evaluation of level of social acceptance, due to the lack of data, uncertainties, and qualitative character of indicators and also to provide effective way to include knowledge and gained experience on the process. A questionnaire was applied as instrument for data collection. The fuzzy model was verified using the city of Ni? as a case study. The results obtained using the developed fuzzy model, shows that the highest level of social acceptance in the city of Ni? is for recycling (57.47 %) and the lowest level of social acceptance is for incineration (17.74 %). The presented study suggests an innovative methodology for evaluation of level of social acceptance of certain waste treatment based on fuzzy logic approach and can be used for ranking of waste management scenarios in the sustainability assessment.     

Estimation of sedimentation rate in the Middle and South Adriatic Sea using 137Cs

(137)Cs activity concentrations were studied in the sediment profiles collected at five locations in the Middle and South Adriatic. In the sediment profiles collected from the South Adriatic Pit, the deepest part of the Adriatic Sea, two (137)Cs peaks were identified. The peak in the deeper layer was attributed to the period of intensive atmospheric nuclear weapon tests (early 1960s), and the other to the Chernobyl nuclear accident (1986). Those peaks could be used to estimate sedimentation rates by relating them to the respective time periods. Grain-size analysis showed no changes in vertical distribution through the depth of the sediment profile, and these results indicate uniform sedimentation, as is expected in deeper marine environments. It was not possible to identify respective peaks on more shallow locations due to disturbance of the seabed either by trawlers (locations Palagru?a and Jabuka) or by river sediment (location Albania). The highest sedimentation rates were found in Albania (～4 mm y(-1)) and Jabuka (3.1 mm y(-1)). For Palagru?a, the sedimentation rate was estimated to be 1.8 mm y(-1), similar to the South Adriatic Pit where the sedimentation rate was estimated to be 1.8±0.5 mm y(-1). Low sedimentation rates found for the Middle and South Adriatic Sea are consistent with previously reported results for the rest of the Mediterranean.     

A comparative study of photocatalytically active nanocrystalline tetragonal zyrcon-type and monoclinic scheelite-type bismuth vanadate

Monoclinic scheelite-type BiVO₄ is currently considered as one of the most promising non-titania photocatalysts, wheras tetragonal zircon-type BiVO₄ is still poorly understood. Herein, a new and simple synthetic approach was applied and nanostructured single-phase zircon-type BiVO₄ was successfully prepared by a controllable ethylene-glycol colloidal route. In addition, nanostructured monoclinic scheelite-type BiVO₄ powders were also fabricated through annealing of the as-prepared samples. A comparative study of the two BiVO₄ polymorphs was conducted and it turned out that the novel synthetic approach had a significant impact on porosity and photocatalytic performance of zircon-structured BiVO₄. All the prepared materials, as-prepared and annealed, were mesoporous, while measured values of specific surface area of some zircon-structured samples (～34?m²/g) were ～7 times higher than those reported thus far for this phase. Interestingly, for the first time, zircon-type BiVO₄, previously considered to be a poor photocatalyst, exhibited a better overall performance in degradation of methyl orange compared to monoclinic scheelite-type BiVO₄. Hence, it could be expected that the here-presented synthesis and observations will both arouse interest in scarcely studied tetragonal zircon-type BiVO₄ and facilitate as well as speed up further research of its properties.     

Composition of the Defensive Secretion in Three Species of European Millipedes

Three European julid species, Cylindroiulus boleti, Leptoiulus trilineatus, and Megaphyllum bosniense, secrete mixtures of up to 12 different quinones. The major components in these species are 2-methoxy-3-methyl-1,4-benzoquinone and 2-methyl-1,4-benzoquinone. 2-Methoxy-5-methylhydroquinone is detected for the first time in the Class Diplopoda. 2-Hydroxy-3-methyl-1,4-benzoquinone, 2,3-dimethoxyhydroquinone, 2-methyl-3,4-methylendioxyphenol, and 2,3-dimethoxy-5-methylhydroquinone are registered for the first time in representatives of the family Julidae. The similar chemical composition of defense secretions in all analyzed European julids and Pacific spirobolids supports the idea of the chemical consistency of defensive compounds in juliform millipedes.     

A parametric method for non-stationary interference suppression in direct sequence spread-spectrum systems

The problem of non-stationary interference suppression in direct sequence spread-spectrum (DS-SS) systems is considered. The phase of interference is approximated by a polynomial within the considered interval. According to the local polynomial Fourier transform (LPFT) principle, the received signal is dechirped by using the obtained phase approximation and the interference is, in turn, suppressed by excising the corrupted low-pass frequency band. For the estimation of polynomial coefficients, we use the product high-order ambiguity function (PHAF), known for its capability to successfully resolve components of a multicomponent polynomial-phase signal (PPS). The proposed method can suppress interferences with both polynomial and non-polynomial phase. In addition, it can suppress both monocomponent and multicomponent interferences. The simulations show that the proposed method outperforms time-frequency (TF) methods, that successfully deal with multicomponent interferences, in terms of the error probability and computational complexity.     

A multimodal hand-based verification system with an aliveness-detection module

This paper presents a multimodal biometrie verification system based on the following hand features: palmprint, four digitprints and four fingerprints. The features are obtained using the Karhunen-Loève transform based approach, and information fusion at the matching-score level was applied. We experimented with different resolutions of the regions of interest, different numbers of features and several normalization and fusion techniques at the matching-score level. To increase the reliability of the system to spoof attacks we included an aliveness-detection module based on thermal images of the hand dor sa. The verification performance when using a system configuration with optimum parameters, i.e., resolution, number of features, normalization and fusion technique, showed an equal error rate (EER) of 0.0020%, which makes the system appropriate for the implementation of high-security biometric systems.