Research on energy storage devices has created a niche owing to the ever increasing demand for alternative energy production and its efficient utilisation. Here, a novel composite of Fe
3
O
4
...nanospheres and carbon quantum dots (C-dots) have been synthesized by a two step chemical route. Hybrids of C-dots with metal oxides can contribute to charge storage capacity through the combined effect of Faradaic pseudocapacitance from the Fe
3
O
4
and the excellent electrical properties of the C-dots, which are a promising new member of the carbon family. The structural and morphological properties of the obtained Fe
3
O
4
-C hybrid nanocomposite were extensively studied. Detailed electrochemical studies show that the high performance of the magnetically responsive Fe
3
O
4
-C hybrid nanocomposite makes it an efficient supercapacitor electrode material. The remarkable improvement in the electrochemical performance of the Fe
3
O
4
-C hybrid nanocomposite is attributed to the Faradaic pseudocapacitance of Fe
3
O
4
coupled with the high electrical conductivity of the C-dot which aided in fast transport and ionic motion during the charge-discharge cycles. Cyclic voltammetry and galvanostatic charge-discharge studies of Fe
3
O
4
-C hybrid nanocomposite show that the nanosystem delivers a maximum specific capacitance of ∼208 F g
−1
. These results demonstrate that the novel Fe
3
O
4
-C hybrid nanocomposite has great potential as a high performance electrode material for supercapacitors.
Here, the novel Fe
3
O
4
-C hybrid nanocomposite demonstrates high specific capacitance (S.C.) than the pristine Fe
3
O
4
nanospheres due to the presence of the highly conducting carbon quantum dots.
Digital image correlation (DIC) is a powerful experimental technique for measuring full-field displacement and strain. The basic idea of the method is to compare images of an object decorated with a ...speckle pattern before and after deformation, and thereby to compute the displacement and strain fields. Local subset DIC and finite element-based global DIC are two widely used image matching methods. However there are some drawbacks to these methods. In local subset DIC, the computed displacement field may not be compatible, and the deformation gradient may be noisy, especially when the subset size is small. Global DIC incorporates displacement compatibility, but can be computationally expensive. In this paper, we propose a new method, the augmented-Lagrangian digital image correlation (ALDIC), that combines the advantages of both the local (fast) and global (compatible) methods. We demonstrate that ALDIC has higher accuracy and behaves more robustly compared to both local subset DIC and global DIC.
This paper presents a comparative investigation of (PV) effect on system stability at different penetration levels. Three different scenarios with their relevant dynamic models are considered, ...namely, distributed units, and centralized farms with and without voltage regulation capabilities. Based on these models, the impact is examined through eigenvalue, voltage stability and transient stability analyses using real network data pertaining to Ontario and its neighboring systems. This impact is quantized in monetary terms based on the long run marginal cost of electricity production in Ontario. It is demonstrated that distributed solar PV generators are significantly more advantageous, from the stability point of view, than solar farms.
The removal of Cr(VI) from aqueous solution by batch adsorption technique using different low-cost adsorbents was investigated. Adsorbents such as clarified sludge—a steel industry waste material, ...rice husk ash, activated alumina, fuller's earth, fly ash, saw dust and neem bark were used to determine the adsorption efficiency. The influence of pH, adsorbent type and concentration, initial Cr(VI) concentration and contact time on the selectivity and sensitivity of the removal process were investigated. Adsorption process was found to be highly pH dependent. The optimum pH range for adsorption of Cr(VI) was found to be between 2 and 3. Kinetics studies were performed to understand the mechanistic steps of the adsorption process and the rate kinetics for the adsorption of Cr(VI) was best fitted with the pseudo-2nd-order kinetic model. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The thermodynamic equilibrium constant and the Gibbs free energy were determined for each system. The adsorption capacity (
q
max) calculated from Langmuir isotherm and the Gibbs free energy (Δ
G
o) value obtained for the different adsorbents showed that clarified sludge was the most effective among the selected adsorbents for the removal of Cr(VI) from aqueous solution. The adsorption efficiencies of rice husk ash and activated alumina were also equally comparable with that of clarified sludge.
Shoreline change analysis and prediction are important for integrated coastal zone management, and are conventionally performed by field and aerial surveys. This paper discusses an alternative ...cost-effective methodology involving satellite remote sensing images and statistics. Multi-date satellite images have been used to demarcate shoreline positions, from which shoreline change rates have been estimated using linear regression. Shoreline interpretation error, uncertainty in shoreline change rate, and cross-validation of the calculated past shorelines have been performed using the statistical methods, namely, Regression coefficient (
R
2) and Root Mean Square Error (RMSE). This study has been carried out along 113.5 km of coast adjoining Bay of Bengal in eastern India, over the time interval 1973 to 2003. The study area has been subdivided into seven littoral cells, and transects at uniform interval have been chosen within each cell. The past and future shoreline positions have been estimated over two time periods of short and long terms in three modes, viz., transect-wise, littoral cell-wise and regionally.
The result shows that 39% of transects have uncertainties in shoreline change rate estimations, which are usually nearer to cell boundaries. On the other hand, 69% of transects exhibit lower RMSE values for the short-term period, indicating better agreement between the estimated and satellite based shoreline positions. It is also found that cells dominated by natural processes have lower RMSE, when considered for long term period, while cells affected by anthropogenic interventions show better agreement for the short-term period. However, on regional considerations, there is not much difference in the RMSE values for the two periods. Geomorphological evidence corroborates the results. The present study demonstrates that combined use of satellite imagery and statistical methods can be a reliable method for shoreline related studies.
Surface soil wetness determines moisture availability that controls the response and feedback mechanisms between land surface and atmospheric processes. A study was carried out to estimate volumetric ...surface soil moisture content (
θ
v
) in cropped areas at field (<10
2
m) to landscape (
≤10
3
m) scales. Triangular scatters from land surface temperature (LST) and normalized difference vegetation index (NDVI) space were utilized to obtain a soil wetness index (SWI), from which
θ
v
was derived, with the combination of dry and wet edges using data from ASTER (Advanced Space borne Thermal Emission and Reflection Radiometer) for field scale and MODIS (MODerate resolution Imaging Spectroradiometer) AQUA for landscape scale studies. The root mean square error (RMSE) of field scale
θ
v
estimates was higher (0.039
m
3
m
−3) than that of the landscape scale (0.033
m
3
m
−3). The narrow swath (∼60
km) of finer resolution sensors (e.g. ASTER) often fails to capture the surface heterogeneity required in the triangle method for deriving SWI and could be one of the main reasons leading to relatively high error in
θ
v
estimates. At both the scales, the lowest error of
θ
v
estimates was found to be restricted within the NDVI range of 0.35–0.65. A geostatistical technique was applied to assess the influence of sub-pixel heterogeneity as an additional source of error for cross-scale comparison of
θ
v
estimates obtained from LST–NDVI scatters. The overall errors of θ
v
estimates from LST–NDVI space were comparable with other globally available test results. The comparison of landscape scale
θ
v
from MODIS AQUA with large-area global estimates from a passive microwave sensor (e.g. AMSR-E) with longer microwave frequency (e.g. C-band) yielded 75% correlation and 0.027
m
3
m
−3 root mean square deviation (RMSD) for fractional vegetation cover less than 0.5. The study recommends the synergistic use of shorter microwave frequency (e.g. L-band) and optical–thermal infrared bands as the best way of satellite based passive soil moisture sensing for vegetated surfaces.
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