Dynamic behavior of a two-stage gear train used in a fixed-speed wind turbine

The dynamic behavior of a two stage spur gear system used in a typical wind turbine is investigated in this paper. With the purpose of having an accurate simulation, for a given excitations, of the dynamic response of bearings, shafts and teeth in contact.In this study, we developed a lamped mass dynamic model with 12 DOFs. This model is excited by external and internal issues sources. The main factors of these excitations are the variability in the wind resource and the time varying mesh stiffness fluctuation.The aerodynamic torque is calculated from an empirical approach of the power coefficient. The incoming flow is modeled by an analytic equation test varies with time. The differential equations governing the system motion are solved by an implicit Newmark algorithm.     

Corrosion resistance enhancement of Ni–P electroless coatings by incorporation of nano-SiO2 particles

Composite coatings were prepared using hypophosphite reduced electroless nickel bath containing 7 g/L SiO₂ nano-particles at pH 4.6 ± 0.2 and temperature 90 ± 2 °C. Deposition rate for SiO₂ nano-composite coatings was 10–12 μm/h. The amount of SiO₂ nano-particles co-deposited in the Ni–P matrix was around 2 wt.%. The analyzes of coating compositions, carried out by Energy Dispersive Analysis of X-ray (EDAX), showed that plain Ni–P and Ni–P/nano-SiO₂ deposits contained around 8 wt.% phosphorus. The X-ray diffraction (XRD) pattern of Ni–P/nano-SiO₂ coating was very similar to that of plain electroless Ni–P coating, whose structure was also amorphous.     

Wear assessment of plasma nitrided AISI H11 steel

Plasma nitriding is one of the effective methods for improvement of the hardness, wear and corrosion resistance of steels. In this research AISI H11 hot working tool steel was plasma nitrided in various gas mixtures for different times and temperatures. The morphology, size and composition of nitride nanoparticles formed on the surface of the specimens were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD). The wear behavior of plasma nitrided samples was studied by means of unlubricated pin-on-disc method under constant load of 80 N, sliding speed of 1 m/s, sliding distance of 2000 m at room temperature. The results showed plasma nitriding process improved the wear behavior of H11 steel. The increase in time and temperature of plasma nitriding decreased the hardness and increased the wear weigh loss of the specimens.     

Alumina coated with oxazolone derivative for extraction of trace amounts of cadmium and copper from water and plant samples

A solid phase extraction procedure is proposed for simultaneous separation and preconcentration trace amounts of Cu(II) and Cd(II) using alumina coated with N'-{4-[4-{1-[4-(dimethylamino)phenyl]methylidene}-5-(4-H)oxazolone]phenyle}acetamide and determination by flame atomic absorption spectrometry. Using 0.1g of the sorbent, the metal ions were sorbed at pH 7 and recovered with 5.0 mL of 0.5 mol L(-1) HNO(3). It was found that extraction can be performed from the sample volumes of 2000 and 800 mL for Cu and Cd, respectively (preconcentration factors of 400 for Cu and 160 for Cd). Obtained sorption capacities for 1g sorbent were 8 mg Cu and 14 mg Cd. The linearity was maintained in the concentration range of 0.1 ng mL(-1) to 7.0 μg mL(-1) for Cu and 0.13 ng mL(-1) to 2.0 μg mL(-1) for Cd in the original solution. Eight replicate determinations of a mixture containing 1.0 μg mL(-1) each of the elements in the final solution gave relative standard deviation ±1.6 and ±1.3% for Cu and Cd, respectively. The detection limit was calculated as 0.06 and 0.05 ng mL(-1) for Cu and Cd, respectively. The proposed method was successfully applied to the determination trace amounts of Cu and Cd in the water and plant samples.     

Measurement of Urbach edge and midgap states in amorphous silicon p-i-n devices

Urbach energy of valence band tails and mid-gap defect densities are important parameters for determining the performance of amorphous silicon (a-Si:H) devices. In this paper, we examine a technique which allows one to determine these parameters in device structures, as opposed to in films. The technique consists of measuring sub-gap quantum efficiency as a function of reverse bias and photon wavelength. We show that there is a distinction between the response of tail states and mid-gap states to the application of reverse bias, and that by analyzing these differences, one can locate the energies of the mid-gap states in the device. The technique gives an accurate measurement of Urbach edge of tail states, even on textured substrates, but only estimates mid-gap states within a factor of 2.     

Switched diversity approach for multireceiving optical wireless systems

A number of existing spatial diversity schemes have been shown to improve the performance of optical wireless communication systems in diversity-rich environments. Among all, switched diversity has low complexity and is simple to implement. In this paper, an innovative spatial diversity scheme based on switched diversity is proposed. The scheme, namely switch-to-dominant combining, contributes to a higher bit error rate (BER) performance when compared to conventional switched diversity schemes, including switch-and-stay and switch-and-examine diversity. The optical multireceiver wireless system operates in a spatially correlated and lognormally distributed fading channel. Analytical analyses are conducted to demonstrate BER and processing load performance offered by the new scheme and compare them to available schemes, i.e., conventional switched combining and selection combining.     

Mixed sulphide-oxide lead and zinc ores: Problems and solutions

Mixed sulphide-oxide lead and zinc ores are most often found in the transition, and occasionally in the oxidised, zones of lead-zinc ore-bodies. They are of great importance because there are numerous unexploited or abandoned reserves of these ores in the world.However they present difficulties for conventional mineral processing due to complex mineralogy. In this paper, the specific problems associated with these types of ores are described and methods for solving these problems, combining economic and technical considerations, are discussed.The results of experiments carried out at laboratory scale are presented, in which the dissolution of mixed ore in sulphuric acid without oxidising agents was investigated. The results show the feasibility of zinc recovery from mixed sulphide-oxide lead and zinc ores, which underlines the potential of this approach. We also propose a conceptual flow diagram for the hydrometallurgical processing of these ores.     

A density-based fuzzy clustering technique for non-destructive detection of defects in materials

In non-destructive testing and evaluation of materials, defects contain visible aggregations of similar levels of brightness with large scale of correlation between them. In most cases, these brightnesses have no notable contrast relative to non-defect counterparts. However, the density and the size of the defect are visually the most notable features. In this paper, we have utilized human conception for classifying defects by the fusion of fuzzy clustering method and fuzzy logic rules based on the density and the size of the defect. The probability of detection and the probability of error are compared with the Bayes classifier. The proposed approach shows that there is less dependency between the variation of density and size of a defect and variations of noise density and distribution. Experimental images from eddy current, ultrasonic and radiography techniques are investigated. It is shown that the new approach reduces the noise and drift, leading to a better detection of defects.     

Efficient and mild synthesis of ortho-hydroxyaryl ketones catalyzed by zinc chloride under solvent-free condition and microwave irradiation

Preparation of ortho-hydroxyaryl ketones was regioselectively carried out from phenol and naphthol derivatives, in reaction with various organic acids by using a ZnCl₂ as catalyst, under microwave and solvent-free mild conditions. In this reaction, the products were obtained in very high yields and very short reaction times.