Preparation of rare earth-doped ZnO hierarchical micro/nanospheres and their enhanced photocatalytic activity under visible light irradiation

Rare earth-doped ZnO hierarchical micro/nanospheres were prepared by a facile chemical precipitation method and characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. The results showed that the as-synthesized products were well-crystalline and accumulated by large amount of interleaving nanosheets. It was also observed that the rare earth doping increased the visible light absorption ability of the catalysts and red shift for rare earth-doped ZnO products appeared when compared to pure ZnO. The photocatalytic studies revealed that all the rare earth-doped ZnO products exhibited excellent photocatalytic degradation of phenol compared with the pure ZnO and commercial TiO₂ under visible light irradiation. Nd-doped ZnO had the highest photocatalytic activity among all of the rare earth-doped ZnO products studied. The optimal Nd content was 2.0 at% under visible light irradiation. The enhanced photocatalytic performance of rare earth-doped ZnO products can be attributed to the increase in the rate of separation of photogenerated electron–hole pairs and hydroxyl radicals generation ability as evidenced by photoluminescence spectra.     

The structure and photocatalytic performances of mechanically synthesized poly(3′,4′‐ethylenedioxy‐2,2′:5′,2″‐Terthiophene)/Zno composites

Poly(3′,4′‐ethylenedioxy‐2,2′:5′,2″‐terthiophene)/ZnO(poly(TET)/ZnO) composites with the ratio of poly(TET) and nano‐ZnO from 3:1 to 1:3 were synthesized by hand grinding and ball milling methods, respectively. The photocatalytic activities of the composites were examined through the degradation processes of methylene blue (MB) solution under UV light irradiation, and the possible mechanism for the photocatalytic activity enhancement by synergetic effects between nano‐ZnO and poly(TET) was proposed. The results showed that the strong interactions between the poly(TET) and nano‐ZnO occurred in the case of ball milling method. The results also proved that the crystallinity of ZnO was not disturbed in both of methods, and the nano‐ZnO was uniformly distributed in polymer matrix in the case of ball milling method. The comparative studies showed that the addition of the nano‐ZnO could enhance the photocatalytic activities of the composites. The highest degradation efficiency (100%) at 3 h under UV light irradiation occurred in the case of poly(TET)/ZnO(1:1) synthesized by ball milling method. Furthermore, the nanocompsosite displayed higher photocatalytic activity than nano‐ZnO, which was due to the holes (h⁺) transferring from the valence band of ZnO to the polymer backbone and the adsorption of MB molecules in polymer matrix via π–π conjugation between MB and aromatic regions of the poly(TET). POLYM. COMPOS., 36:1597–1605, 2015. © 2014 Society of Plastics Engineers     

Structural and optical properties of nc-Si:H thin films deposited by layer-by-layer technique

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited on c-Si and quartz substrates by layer-by-layer (LBL) technique using radio-frequency plasma enhanced chemical vapour deposition system. The effects of rf power on the interlayer elemental profiling, structural and optical properties of the films were investigated by Auger electron spectroscopy, Fourier transform infrared spectroscopy, Raman scattering spectroscopy, X-ray diffraction and optical transmission and reflection spectroscopy. The results revealed that the LBL deposition leads to a formation of different ranges of crystallite sizes of nc-Si corresponds 3–6 and 8–26 nm respectively. LBL deposition also demonstrated a capability to increase the crystalline volume fraction of nc-Si up to 65.3 % with the crystallite size in between 5 and 6 nm, at the rf power in between 80 and 100 W. However, the crystalline volume fraction decreased for the rf power above 100 W due to the growth of nc-Si was suppressed by the formation of SiO₂. In addition, the onset of crystallization of the films deposited on c-Si and quartz substrates are different with increase in the rf power. The effects of rf power on the growth of nc-Si, and the hydrogen content, structural disorder, crystallite size of nc-Si and oxygen diffusion into the LBL layer with the change of optical energy gap under the variation of rf power are also discussed.     

Development and Implementation of a Novel Fault Diagnostic and Protection Technique for IPM Motor Drives

This paper presents the practical implementation of a novel fault diagnostic and protection scheme for the interior permanent-magnet (IPM) synchronous motors using wavelet packet transform (WPT) and artificial neural network. In the proposed technique, the line currents of different faulted and normal conditions of the IPM motor are preprocessed by the WPT. The second level WPT coefficients of line currents are used as inputs of a three-layer feedforward neural network. The proposed protection technique is successfully simulated and experimentally tested on the line-fed and inverter-fed IPM motors. The Texas Instrument 32-bit floating-point digital signal processor TMS320C31 is used for the real-time implementation of the proposed protection algorithm. The offline and online test results of both line-fed and inverter-fed IPM motors are given. These test results showed satisfactory performances of the proposed diagnostic and protection technique in terms of speed, accuracy, and reliability.     

Energy conservation measures in an institutional building in sub-tropical climate in Australia

In this study, various energy conservation measures (ECMs) on heating, ventilating and air conditioning (HVAC) and lighting systems for a four-storied institutional building in sub-tropical (hot and humid climate) Queensland, Australia are evaluated using the simulation software called DesignBuilder (DB). Base case scenario of energy consumption profiles of existing systems are analysed and simulated first then, the simulated results are verified by on-site measured data. Three categories of ECMs, namely major investment ECMs (variable air volume (VAV) systems against constant air volume (CAV); and low coefficient of performance (COP) chillers against high COP chillers); minor investment ECMs (photo electric dimming control system against general lighting, and double glazed low emittance windows against single-glazed windows) and zero investment ECMs (reset heating and cooling set point temperatures) are evaluated. It is found that the building considered in this study can save up to 41.87% energy without compromising occupancies thermal comfort by implementing the above mentioned ECMs into the existing system.     

Production of acoustic waves from pulsed thermal radiation

Generation of acoustic waves from a pulsed thermal radiation beam was experimentally investigated in this paper. Unlike other TACs (thermal acoustic converters), acoustic wave frequencies and phases of this type of TACs can be easily adjusted and controlled—a feature essential to the synchronization of TACs in an array. The TACs we developed were made up of a cylindrical aluminum housing, a glass cover, and metallic wool for effective thermal‐to‐acoustic energy conversion. Radiation emitted from an infrared heater was chopped at a constant frequency prior to entering the converter through the glass cover. The metallic wool was periodically heated by the pulsed radiation beam and cooled because of heat losses to the surroundings. Experiments were conducted for different converter designs and metallic wools, as well as different chopper speeds and radiation intensities. The amplitudes of generated sound waves were found to be dependent on the radiation intensity, the grade and properties of the metallic wool, and the cooling rate of the wool. Higher radiation intensities and thinner wools of lower thermal conductivity produced sounds of higher amplitude. More effective cooling of the metallic wool also helped. Acoustic energy output can also be enhanced by reducing the amount of air in the converter. Copyright © 2015 John Wiley & Sons, Ltd.     

Schulze and ranked-pairs voting are fixed-parameter tractable to bribe,manipulate, and control

Schulze and ranked-pairs elections have received much attention recently, and the former has quickly become a quite widely used election system. For many cases these systems have been proven resistant to bribery, control, or manipulation, with ranked pairs being particularly praised for being NP-hard for all three of those. Nonetheless, the present paper shows that with respect to the number of candidates, Schulze and ranked-pairs elections are fixed-parameter tractable to bribe, control, and manipulate: we obtain uniform, polynomial-time algorithms whose running times’ degrees do not depend on the number of candidates. We also provide such algorithms for some weighted variants of these problems.     

The view from the top

The challenge of integrating large amounts of renewable energy resources into the electric sector requires updated transmission analysis techniques. Economic planning, primarily in the form of value-based planning over interconnectionwide areas, is needed before performing the traditional single-hour, capacity-based reliability analyses.