Thermoelastic and structural properties of ionically conducting cerate perovskites: (II) SrCeO₃ between 1273 K and 1723 K

Thermodynamic grüneisen parameter and bond valence parameters for strontium cerate perovskite.</p

Investigation of the elastic/crystallographic anisotropy of welds for improved ultrasonic inspections

Ultrasonic inspection is an effective way of ensuring the initial and continued integrity of welded joints nondestructively. The accuracy of the technique can be compromised due to spatial variations in the anisotropy of the material stiffness in the weld region. Predicted in-plane weld stiffness maps can be used to correct the ultrasound paths for improved results, but these are based on several assumptions about the weld material. This study has examined the validity of these assumptions and provided detailed weld metal grain orientation maps from which a stiffness map has been calculated for an Inconel 600 weld. Good agreement was found except near the boundaries of the weld. Further it was found that the crystal growth (most compliant) direction was typically oriented around 14.5 degrees out of plane towards the welding direction. Having validated the model, a comparison of predicted and calculated stiffness maps was made. The predicted map was found to be satisfactory over the majority of the weld area. (C) 2014 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/)

Intrinsic dielectric and spectroscopic behavior of perovskite Ba(Ni1/3Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 microwave dielectric ceramics

[[abstract]]Ceramics of 0.35Ba(Ni1/3Nb2/3)O3–0.65Ba(Zn1/3Nb2/3)O3 were prepared by the mixed oxide route. The effect of the cooling rate (2 °C–240 °C/h) after sintering on the microwave dielectric properties of the ceramics was examined. While the extrinsic factors, such as porosity and secondary phases, markedly influence the dielectric properties in the low-frequency regime, they have minimal effect on these properties in the high-frequency regime. The mechanisms involved in modifying the high-frequency dielectric properties of the materials were investigated by Fourier transform infrared and Raman spectroscopy, in conjunction with the Rietveld analysis of x-ray diffraction (XRD) spectra. A reduction in the cooling rate after sintering results in an increase in the high-frequency Q×f (product of dielectric Q value and measurement frequency) from 42 to 58 THz in the high-frequency regime (∼1.5 THz). Such behavior correlates very well with the increase in the B-site occupancy by Nb (deduced from the Rietveld analyses of XRD spectra) and the increase in the coherency of the lattice vibration (deduced from the reduction in the full-width-at-half-maximum of the A1g(O) Raman mode). In contrast, the cooling rate after sintering has very limited effect on the relative permittivity (varying from 40.8 to 41.9 at 1.5 THz), which is in accord with the phenomenon that the cell volume and the Raman shift of A1g(O) Raman mode are essentially independent of the cooling rate.[[booktype]]紙

A coupled optical-thermal-electrical model to predict the performance of hybrid PV/T-CCPC roof-top systems

A crossed compound parabolic concentrator (CCPC) is applied into a photovoltaic/thermal (PV/T) hybrid solar collector, i.e. concentrating PV/T (CPV/T) collector, to develop new hybrid roof-top CPV/T systems. However, to optimise the system configuration and operational parameters as well as to predict their performances, a coupled optical, thermal and electrical model is essential. We establish this model by integrating a number of submodels sourced from literature as well as from our recent work on incidence-dependent optical efficiency, six-parameter electrical model and scaling law for outdoor conditions. With the model, electrical performance and cell temperature are predicted on specific days for the roof-top systems installed in Glasgow, Penryn and Jaen. Results obtained by the proposed model reasonably agree with monitored data and it is also clarified that the systems operate under off-optimal operating condition. Long-term electric performance of the CPV/T systems is estimated as well. In addition, effects of transient terms in heat transfer and diffuse solar irradiance on electric energy are identified and discussed

A scaling law for monocrystalline PV/T modules with CCPC and comparison with triple junction PV cells

This is the final version of the article. Available from Elsevier via the DOI in this record.Scaling laws serve as a tool to convert the five parameters in a lumped one-diode electrical model of a photovoltaic (PV) cell/module/panel under indoor standard test conditions (STC) into the parameters under any outdoor conditions. By using the transformed parameters, a current-voltage curve can be established under any outdoor conditions to predict the PV cell/module/panel performance. A scaling law is developed for PV modules with and without crossed compound parabolic concentrator (CCPC) based on the experimental current-voltage curves of six flat monocrystalline PV modules collected from literature at variable irradiances and cell temperatures by using nonlinear least squares method. Experiments are performed to validate the model and method on a monocrystalline PV cell at various irradiances and cell temperatures. The proposed scaling law is compared with the existing one, and the former exhibits a much better accuracy when the cell temperature is higher than 40 °C. The scaling law of a triple junction flat PV cell is also compared with that of the monocrystalline cell and the CCPC effects on the scaling law are investigated with the monocrystalline PV cell. It is identified that the CCPCs impose a more significant influence on the scaling law for the monocrystalline PV cell in comparison with the triple junction PV cell. The proposed scaling law is applied to predict the electrical performance of PV/thermal modules with CCPC.The authors gratefully acknowledge the EPSRC Solar Challenge project SUNTRAP (EP/K022156/1) and Sȇr Cymru National Research Network grant 152 for financial support in the UK

A scaling law for monocrystalline PV/T modules with CCPC and comparison with triple junction PV cells

Scaling laws serve as a tool to convert the five parameters in a lumped one-diode electrical model of a photovoltaic (PV) cell/module/panel under indoor standard test conditions (STC) into the parameters under any outdoor conditions. By using the transformed parameters, a current-voltage curve can be established under any outdoor conditions to predict the PV cell/module/panel performance. A scaling law is developed for PV modules with and without crossed compound parabolic concentrator (CCPC) based on the experimental current-voltage curves of six flat monocrystalline PV modules collected from literature at variable irradiances and cell temperatures by using nonlinear least squares method. Experiments are performed to validate the model and method on a monocrystalline PV cell at various irradiances and cell temperatures. The proposed scaling law is compared with the existing one, and the former exhibits a much better accuracy when the cell temperature is higher than 40 °C. The scaling law of a triple junction flat PV cell is also compared with that of the monocrystalline cell and the CCPC effects on the scaling law are investigated with the monocrystalline PV cell. It is identified that the CCPCs impose a more significant influence on the scaling law for the monocrystalline PV cell in comparison with the triple junction PV cell. The proposed scaling law is applied to predict the electrical performance of PV/thermal modules with CCPC

Multiphysics simulations of thermoelectric generator modules with cold and hot blocks and effects of some factors

This is the final version of the article. Available from Elsevier via the DOI in this record.Transient and steady-state multiphysics numerical simulations are performed to investigate the thermal and electrical performances of a thermoelectric generator (TEG) module placed between hot and cold blocks. Effects of heat radiation, leg length and Seebeck coefficient on the TEG thermal and electrical performances are identified. A new correlation for the Seebeck coefficient with temperature is proposed. Radiation effects on the thermal and electric performances are found to be negligible under both transient and steady-state conditions. The leg length of the TEG module shows a considerable influence on the electrical performance but little on the thermal performance under transient conditions. A nearly linear temperature profile on a leg of the TEG module is identified. The temperature profile of the substrate surfaces is non-uniform, especially in the contacted areas between the straps (tabs) and the substrates.The work is supported by EPSRC SUPERGEN Solar Challenge with grant: EP/K022156/1-Scalable Solar Thermoelectrics and Photovoltaics (SUNTRAP)

Tungsten Bronze Barium Neodymium Titanate (Ba 6–3 Nd 8+2 Ti 18 O 54 ): An Intrinsic Nanostructured Material and Its Defect Distribution

We investigated the structure of the tungsten bronze barium neodymium titanates Ba6–3nNd8+2nTi18O54, which are exploited as microwave dielectric ceramics. They form a complex nanostructure, which resembles a nanofilm with stacking layers of ∼12 Å thickness. The synthesized samples of Ba6–3nNd8+2nTi18O54 (n = 0, 0.3, 0.4, 0.5) are characterized by pentagonal and tetragonal columns, where the A cations are distributed in three symmetrically inequivalent sites. Synchrotron X-ray diffraction and electron energy loss spectroscopy allowed for quantitative analysis of the site occupancy, which determines the defect distribution. This is corroborated by density functional theory calculations. Pentagonal columns are dominated by Ba, and tetragonal columns are dominated by Nd, although specific Nd sites exhibit significant concentrations of Ba. The data indicated significant elongation of the Ba columns in the pentagonal positions and of the Nd columns in tetragonal positions involving a zigzag arrangement of atoms along the b lattice direction. We found that the preferred Ba substitution occurs at Nd[3]/[4] followed by Nd[2] and Nd[1]/[5] sites, which is significantly different to that proposed in earlier studies. Our results on the Ba6–3nNd8+2nTi18O54 “perovskite” superstructure and its defect distribution are particularly valuable in those applications where the optimization of material properties of oxides is imperative; these include not only microwave ceramics but also thermoelectric materials, where the nanostructure and the distribution of the dopants will reduce the thermal conductivity

SeeAround: an offline mobile live support system for the visually impaired

The inability of blind or partially-sighted people to understand visual content and real-life situations reduces their standard of living, especially in a world mainly tailored for sighted individuals. Despite the progress made by certain devices to assist them in using touch, sound, or other senses, these solutions often fall short of bridging the comprehension gap. Our work proposes an intuitive, user-friendly mobile-based framework named "SeeAround" that is capable of automatically providing real-time audio descriptions of the user's immediate visual surroundings. Our solution addresses this challenge by leveraging key point detection, image captioning, text-to-speech (TTS), optical character recognition (OCR), and translation algorithms to offer comprehensive support for visually impaired individuals. Our system architecture relies on convolutional neural networks (CNNs) such as Inception-V3, Inception-V4, and ResNet152-V2 to extract detailed features from images and employs a multi-gated recurrent unit (GRU) decoder to generate word-by-word natural language descriptions. Our framework was integrated into mobile applications and optimized with TensorFlow lite pre-trained models for easy integration on the Android platform