Comparative study to use nanofluid ZnO and CuO with phase change material in photovoltaic thermal system

In this study, the simultaneous use of nanofluid and phase changing material as a coolant for photovoltaic fluid collector system and its effects are investigated experimentally. Two types of nanofluid are taken for the consideration, that is, ZnO and CuO, which are water‐based fluid. The experiments are performed in five different types of photovoltaic thermal system conventional: PT, PVT (ZnO), PVT (CuO), PCM medium (PVT/PCM/ZnO), and PCM medium (PVT/PCM/CuO). The results are obtained for surface temperature, energy, and thermal efficiency, and it is compared with each other. Further, the effect of the nanofluid as the effective alternative for pure deionized water is measured. From the results, it is evident that the PVT/PCM/CuO system minted 15% high electric output compared with convention module. Furthermore, the addition of the CuO nanofluid increases the thermal output significantly up to 8% for PVT and 12% for PCM without energy consumption. It also found that the nanofluid increases the overall energy efficiency of the system compared with convention PV.     

Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature

Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications.     

3D and simplified pseudo-2D modeling of single cell of a high temperature solid oxide fuel cell to be used for online control strategies

In the current study, a single cell of a planar SOFC is firstly modeled in 3D using commercial SOFC module of ANSYS Fluent and the results are validated against the experimental investigations in the literature. Many researchers have used ANSYS Fluent for simulating solid oxide fuel cells. However, there is a huge gap in the literature on explaining the detailed procedure that should be followed in order to use this software effectively. A thorough step-by-step approach is presented to provide a deep insight into the software. Thereafter, a simplified quasi-2D method with infinitely shorter computational time is developed and the results are compared with the 3D model. It is found that the reduced model is capable of being utilized as an alternate method for both online diagnosis and designing active control strategies.     

Design of active reconfigurable wheel antenna based on PIN diodes

In this paper we suggest a reconfigurable wheel antenna based on PIN diodes. The antenna is excited by a single-feed and operates in S-band and X-band. Proposed antenna’s structure is composed of two circular rings that are excited by multiple PIN diodes and microstrip lines. Antenna’s reconfiguration is realized by inserting switches into spokes and peripheral regions of a wheel antenna. The required resonance frequency is provided by combination of the structures which are controlling by PIN diodes. Developed antenna was fabricated on a RT duroid material and its pattern measurements were carried out in the outdoor environment. The measured results have demonstrated antenna’s ability to be reconfigurated and good radiation pattern characteristics within two frequency bands.     

Fluxless arc weld-brazing of aluminium alloy to steel

In this work, joining of aluminium alloy AA6061-T6 to Interstitial Free steel using pulsed gas metal arc welding process has been attempted. The effect of different surface conditions of steel (viz, galvanized, galvanealed and uncoated) and gap between the sheets on braze joint formation have been investigated. Galvanized steel surface showed good bead width, joint formation and lap shear strength compared to the other two combinations. Interface gap has not affected the wetting behaviour significantly but presence of a gap of 300 μm or so helped in escape of zinc vapour during the process there by avoiding formation of any crevice or macroporosity in the joint. Features and properties of the joint are characterized by metallography, fractography, energy dispersive spectroscopy (EDS) and lap shear tests. Load carrying capacity of Al-Galvanized steel was highest (222 N/mm of seam length) compared to other combinations, aided by better wetting due to presence of Zn on the surface and minimum porosity due to interfacial gap provided during brazing.     

Magnetic resonance image denoising using nonlocal maximum likelihood paradigm in DCT‐framework

The data acquired by magnetic resonance (MR) imaging system are inherently degraded by noise that has its origin in the thermal Brownian motion of electrons. Denoising can enhance the quality (by improving the SNR) of the acquired MR image, which is important for both visual analysis and other post processing operations. Recent works on maximum likelihood (ML) based denoising shows that ML methods are very effective in denoising MR images and has an edge over the other state‐of‐the‐art methods for MRI denoising. Among the ML based approaches, the Nonlocal maximum likelihood (NLML) method is commonly used. In the conventional NLML method, the samples for the ML estimation of the unknown true pixel are chosen in a nonlocal fashion based on the intensity similarity of the pixel neighborhoods. Euclidean distance is generally used to measure this similarity. It has been recently shown that computing similarity measure is more robust in discrete cosine transform (DCT) subspace, compared with Euclidean image subspace. Motivated by this observation, we integrated DCT into NLML to produce an improved MRI filtration process. Other than improving the SNR, the time complexity of the conventional NLML can also be significantly reduced through the proposed approach. On synthetic MR brain image, an average improvement of 5% in PSNR and 86%reduction in execution time is achieved with a search window size of 91 × 91 after incorporating the improvements in the existing NLML method. On an experimental kiwi fruit image an improvement of 10% in PSNR is achieved. We did experiments on both simulated and real data sets to validate and to demonstrate the effectiveness of the proposed method. © 2015 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 25, 256–264, 2015     

Growth and characterization of diamond particles,diamond films,and CNT-diamond composite films deposited simultaneously by hot filament CVD

It is important to understand the growth of CNT-diamond composite films in order to improve the inter-link between two carbon allotropes, and, in turn, their physical properties for field emission and other applications. Isolated diamond particles, continuous diamond thin films, and thin films of carbon nanotubes (CNTs) having non-uniformly distributed diamond particles (CNT-diamond composite films) were simultaneously grown on unseeded, seeded, and catalyst pre-treated substrates, respectively, using a large-area multi-wafer-scale hot filament chemical vapor deposition. Films were deposited for four different growth durations at a given deposition condition. The changes in surface morphology and growth behavior of diamond particles with growth duration were investigated ex situ using field emission scanning electron microscopy and 2D confocal Raman depth spectral imaging, respectively. A surface morphological transition from faceted microcrystalline nature to nanocrystalline nature was observed as a function of growth duration in the case of isolated diamond particles grown on both unseeded and catalyst pre-treated substrates. However, such a morphological transition was not observed on the simultaneously grown continuous diamond thin films on seeded substrates. 2D confocal Raman depth spectral imaging of diamond particles showed that the local growth of CNTs did not affect the growth behavior of neighboring diamond particles on catalyst pre-treated substrates. These observations emphasize the importance of surface chemical reactions at the growth site in deciding sp² or sp³ carbon growth and the final grain size of the diamond films.