EEMD assisted supervised learning for the fault diagnosis of BLDC motor using vibration signal

Journal of Mechanical Science and Technology - Predictive maintenance (PdM) has become a major issue in system health monitoring, as machines are operating under more complex and diverse conditions...     

Aspect based citation sentiment analysis using linguistic patterns for better comprehension of scientific knowledge

Scientometrics - An almost unrestrained access to research plethora has emerged with a potential drawback: extracting relevant scientific publications is not a straightforward task anymore. The...     

Tethered methanol droplet combustion in carbon-dioxide enriched environment under microgravity conditions

Tethered methanol droplet combustion in carbon dioxide enriched environment is simulated using a transient one-dimensional spherosymmetric droplet combustion model that includes the effects of tethering. A priori numerical predictions are compared against recent experimental data. The numerical predictions compare favorably with the experimental results and show significant effects of tethering on the experimental observations. The presence of a relatively large quartz fiber tether increases the burning rate significantly and hence decreases the extinction diameter. The simulations further show that the extinction diameter depends on both the initial droplet diameter and the ambient concentration of carbon dioxide. Increasing the droplet diameter and ambient carbon dioxide concentration both of them lead to a decrease in the burning rate and increase in the extinction diameter. The influence of ambient carbon dioxide concentration on extinction shows a sharp transition in extinction for larger size droplets (d_o > 1.5 mm) due to a change in the mode of extinction from diffusive to radiative control. In addition predictions from the numerical model is compared against a recently developed simplified theoretical model for predicting extinction diameter for methanol droplets, where the presence and heat transfer contribution of the tether is not taken into account implicitly. The numerical results suggest some limitation in the theoretical modeling assumptions for favorable comparisons with the experimental data.     

On the extinction characteristics of alcohol droplet combustion under microgravity conditions – A numerical study

Quasi-steady burning and extinction of droplets are of interest from both fundamental and application viewpoints. The latter is related to combustor performance and fire safety issues in reduced gravity environments. Influences of diluent in the atmosphere on isolated droplet combustion characteristics including extinction provide insights to fire extinguishment phenomena and the effectiveness of various diluents as fire suppressants. Extinction of pure methanol and methanol–water droplets ranging from 1.5 to 7 mm size, for varying levels of ambient carbon-dioxide, helium and oxygen concentration – burning in a quiescent microgravity environment were studied numerically to compare the effectiveness of fire suppressant diluent selection and determining the limiting oxygen index. The results show distinct regimes of diffusive and radiative extinction. The transition from diffusive to radiative extinction is strongly influenced by the ambient diluent selection, especially by carbon dioxide concentration. Results for helium as the diluent showed increased burning rate and extinction due to diffusive heat loss. An “extinction characteristic” correlation is proposed that depends on burning rate, ambient diffusivity and flame standoff ratio. Recent methanol droplet experiments conducted over a wide range of operating conditions onboard the International Space Station were found to yield results that agree well with the proposed “extinction characteristic” correlation.     

Influence of angle deposition on the properties of ZnTe thin films prepared by thermal evaporation

Thin films of ZnTe were deposited at angles of 0°, 20°, 40°, 60° and 80° by thermal evaporation. The chemical, structural, morphological, optical, and photocurrent properties of ZnTe thin films were investigated. The elemental composition of the films was investigated by energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS). EDX and XPS analyses showed that at lower angles (0° and 20°), the deposited films were Te-rich, at 40°, the deposited film was nearly stoichiometric; and at higher angles (60° and 80°), the deposited films were Zn-rich. X-ray diffraction (XRD) analysis showed that all films were polycrystalline. X-ray diffraction patterns showed that lower-angles-deposited films had an extra peak at 2θ =?36.47° that belongs to Te element. Atomic force microscopy analysis revealed that the surface roughness of films was increased by increasing the deposition angle from 0° to 80° because shadowing effect raised due to an oblique angle. It was observed that higher-angles-deposited films (ZnTe-60°, and ZnTe-80°) showed less transmittance and high reflectance compared to lower-angles-deposited films because of high metallic Zn content in these films. Current-voltage (I-V) measurements showed that nearly stoichiometric (ZnTe-40°) film showed better photocurrent response compared to non-stoichiometric films (ZnTe-0°, ZnTe-20°, ZnTe-60°, and ZnTe-80°).     

Recent progress in barium zirconate proton conductors for electrochemical hydrogen device applications: A review

Electrochemical hydrogen devices like fuel cells are widely investigated as promising technologies to mitigate the rising environmental challenges and enhance the renewable energy economy. In these devices, proton-conducting oxides (PCOs) are applied as electrolyte materials to transport protons. Excellent physical stability and higher proton transport number are two essential properties of electrolyte materials. Doped BaZrO₃ (BZO) is a solid ion-conducting perovskite material with high chemical stability and good proton-conducting properties at an intermediate temperature range of 400–650 °C. Therefore, BZO is an attractive material among the exciting proton-conducting oxides as electrolyte material. To enhance the proton transport properties and improve the material fabrication process of BZO, techniques such as the use of dopants, sintering aid, synthesis methods are crucial. The present review work highlights the applications of BZO as electrolyte material in electrochemical hydrogen devices such as hydrogen isotopes separation systems, hydrogen sensors, hydrogen pumps, and protonic ceramic fuel cells (PCFCs) or solid oxide fuel cells (SOFCs). The central section of this review summarizes the recent research investigations of these applications and provides a comprehensive insight into the various synthesis process, doping, sintering aid, operating environments, and operating condition's impact on the composition, morphology, and performance of BZO electrolyte materials. Based on the reviewed literature, remarks on current challenges and prospects are provided. The presented information on in-depth analysis of the physical properties of barium zirconate electrolyte's along with output performance will guide aspirants in conducting research further on this field.     

Managing the future megacity: an appraisal of knowledge about energy challenges and energy-saving attitudes among households in Dhaka

Energy saving is now an important household priority in Dhaka. Energy crisis especially electricity crisis is one of the most important sufferings of the residents in Dhaka. As tackling such immense problem requires initiatives from both government and household ends, this study focuses on appraising the energy saving attitudes of the households in Dhaka to help government in designing and implementing appropriate policy options. Using a sample of 400 households, surveyed in a cross-section of locations in Dhaka, the study reveals that there is an encouraging level of homogeneous knowledge about energy challenges and various dimensions of energy-saving attitudes. Furthermore, the price of the energy-saving appliances is considered as one of the most important impediments in achieving a more comprehensive energy-saving response among the household is quite well match with the socioeconomic characteristics of the majority of the residents in Dhaka.