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...     

Data Fusion Techniques for Improving Soil Moisture Deficit Using SMOS Satellite and WRF-NOAH Land Surface Model

Microwave remote sensing and mesoscale weather models have high potential to monitor global hydrological processes. The latest satellite soil moisture dedicated mission SMOS and WRF-NOAH Land Surface Model (WRF-NOAH LSM) provide a flow of coarse resolution soil moisture data, which may be useful data sources for hydrological applications. In this study, four data fusion techniques: Linear Weighted Algorithm (LWA), Multiple Linear Regression (MLR), Kalman Filter (KF) and Artificial Neural Network (ANN) are evaluated for Soil Moisture Deficit (SMD) estimation using the SMOS and WRF-NOAH LSM derived soil moisture. The first method (and most simplest) utilizes a series of simple combinations between SMOS and WRF-NOAH LSM soil moisture products, while the second uses a predictor equation generally formed by dependent variables (Probability Distributed Model based SMD) and independent predictors (SMOS and WRF-NOAH LSM). The third and fourth techniques are based on rigorous calibration and validation and need proper optimisation for the final outputs backboned by strong non-linear statistical analysis. The performances of all the techniques are validated against the probability distributed model based soil moisture deficit as benchmark; estimated using the ground based observed datasets. The observed high Nash Sutcliffe Efficiencies between the fused datasets with Probability Distribution Model clearly demonstrate an improved performance from the individual products. However, the overall analysis indicates a higher capability of ANN and KF for data fusion than the LWA or MLR approach. These techniques serve as one of the first demonstrations that there is hydrological relevant information in the coarse resolution SMOS satellite and WRF-NOAH LSM data, which could be used for hydrological applications.     

Efficient PAPR Reduction in DCT-SCFDMA System Based on Absolute Exponential Companding Technique with Pulse Shaping

Discrete Cosine Transform based Single carrier frequency division multiple access (DCT-SCFDMA) is a prominent technique for providing high data rates in multimedia services. It also provides high Quality of Service to the users by mitigating the fading of signals. But High peak-to-average power ratio (PAPR) is a technical challenge which reduces the efficiency of RF power amplifiers. In this article, a novel joint scheme of PAPR reduction method is proposed and analyzed based on pulse shaping and absolute exponential companding (AEXP) technique. Our method proposes the use of standard raised cosine filter and square root raised cosine filter along with the AEXP companding process separately in DCT-SCFDMA system for different subcarrier mapping techniques e.g. interleaved frequency division multiple access and localized frequency division multiple access. Through extensive simulations, the numerical analysis presents that proposed architecture achieves significant improvements over the existing standard pulse shaping methods when used alone in DCT-SCFDMA system as far as the lowest PAPR is concerned.     

Temperature rise due to slip between wheel and rail—an analytical solution for hertzian contact

The temperature rise due to slip between wheel and rail is obtained by the Laplace transform method. The pressure distribution at the wheel-rail contact is taken to be elliptical and it is assumed that the fast moving heat source can be approximated to an instantaneous static source.     

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.     

Thermodynamics of ion conductivity of alkali halides across a polystyrene-based titanium arsenate membrane

The electric conductance of ion across titanium arsenate membrane has been recorded. Aqueous solutions of KCl, NaCl and LiCl were used. The conductance values of titanium arsenate membrane have been found to increase with increase in concentrations as well as temperature (10-50 °C) in these cases. The conductance values of electrolytes follow the sequence for the cations: K⁺ > Na⁺ > Li⁺. Negative ΔS values are considered to indicate formation of bond between the permeating species and the membrane material. The physico-chemical characterization of the hybrid material was established by XRD, TGA and simultaneous SEM studies.     

Impedance characteristics and electrical double-layer capacitance of composite polystyrene–cobalt–arsenate membrane

In continuation of our previous work with composite polystyrene–cobalt–arsenate (PS–Co–As), we further extended impedance measurements. All calculations reported were extracted from experiments carried out in the frequency range of 1–5 kHz and different concentrations (0.0001 ≤ c(M) ≤ 1) of KCl and NaCl at isothermal temperature (25 ± 0.1 °C). The membrane capacitance and resistance measurements were observed to depend on the concentration and the applied frequency of the electrolyte. The observed capacitances and resistances were used to calculate the membrane resistances (R_M), capacitance (C_M), reactance (X_X), and also derive the impedance (Z). At higher frequencies, the capacitances became low and the impedance decreased with increasing frequency with a corresponding increase in the measured phase angle. On the other hand at the highest frequencies attainable, the phase angle became low. At low frequencies, the phase angle was become independent of the cation, while the impedance showed a clear dependence. The diffused double-layer polarization charge on the geometric capacitor played important role by affecting the overall membrane capacitance. The applied frequencies affected the double-layer capacitance due to the movement of ions across the membrane. At the membrane–electrolyte interface, the electrical double-layer was influenced in addition to being controlled by the transport of ions.     

Phase stability and mechanical properties of wire+arc additively manufactured H13 tool steel at elevated temperatures

Wire+arc additive manufacturing(WAAM)is considered an innovative technology that can change the manufacturing landscape in the near future.WAAM offers the benefits of inexpensive initial system setup and a high deposition rate for fabricating medium-and large-sized parts such as die-casting tools.In this study,AISI H13 tool steel,a popular die-casting tool metal,is manufactured by cold metal transfer(CMT)-based WAAM and is then comprehensively analyzed for its microstructural and mechanical properties.Location-dependent phase combinations are observed,which could be explained by nonequilibrium thermal cycles that resulted from the layer-by-layer stacking mechanism used in WAAM.In addition,remelting and reheating of the layers reduces welding anomalies(e.g.,pores and voids).The metallurgical characteristics of the H13 strongly correlate with the mechanical properties.The combinations of phases at different locations of the additively manufactured part exhibit a periodic microhardness profile.Martensite,Retained Austenite,Ferrite,and Carbide phases are found in combination at different locations of the part based on the part’s temperature distribution during additive deposition.Moreover,the tensile properties at elevated temperatures(23℃,300℃,and 600℃)are comparable to those from other WAAM and additive manufacturing(AM)processes.The X-ray diffraction results verify that the microstructural stability of the fabricated parts at high temperatures would allow them to be used in high temperatures.