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Modeling monthly streamflow in mountainous basin by MARS, GMDH-NN and DENFIS using hydroclimatic data
No full textAccurate estimation of streamflow has a vital importance in water resources engineering, management and planning. In the present study, the abilities of group method of data handling-neural networks (GMDH-NN), dynamic evolving neural-fuzzy inference system (DENFIS) and multivariate adaptive regression spline (MARS) methods are investigated for monthly streamflow prediction. Precipitation, temperature and streamflows from Kalam and Chakdara stations at Swat River basin (mountainous basin), Pakistan, are used as inputs to the applied models in the form of different input scenarios, and models' performances are evaluated on the basis of root mean square error (RMSE), mean absolute error (MAE), Nash-Sutcliffe efficiency (NSE) and combined accuracy (CA) indexes. Test results of the Kalam Station show that the DENFIS model provides more accurate prediction results in comparison of GMDH-NN and MARS models with the lowest RMSE (18.9 m(3)/s), MAE (13.1 m(3)/s), CA (10.6 m(3)/s) and the highest NSE (0.941). For the Chakdara Station, the MARS outperforms the GMDH-NN and DENFIS models with the lowest RMSE (47.5 m(3)/s), MAE (31.6 m(3)/s), CA (26.1 m(3)/s) and the highest NSE (0.905). Periodicity (month number of the year) effect on models' accuracies in predicting monthly streamflow is also examined. Obtained results demonstrate that the periodicity improves the models' accuracies in general but not necessarily in every case. In addition, the results also show that the monthly streamflow could be successfully predicted using only precipitation and temperature variables as inputs
Ferroelectric ceramic dispersion to enhance the beta phase of polymer for improving dielectric and ferroelectric properties of the composites
Get PDFFerroelectric ceramic-polymer composites consisting of Poly Vinyledine Fluoride-Hexa Fluoro Propylene (PVDF-HFP) as polymer host and 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3(BZT-BCT) ceramics as filler were prepared using solution casting technique. These composites are characterized for structural, microstructural, vibrational, optical, dielectric and ferroelectric properties at various experimental conditions. The electroactive beta phase fraction (observed from XRD and FTIR analysis) increases as the filler concentration increases up to 20 wt% of BZT-BCT and above that its value decreases. FTIR results were analyzed to understand the mechanism of enhancement of beta phase by the interaction between negatively surface charged ions of filler with the CH(2)dipole of polymer matrix. UV-visible spectroscopy also employed to confirm polymer-ceramic filler interaction. Variation of the dielectric constant with different filler concentrations is explained using the percolation theory. Finally, the interplay between the functional properties and the beta phase is discussed in detail
Investigating the seasonal variability in source contribution to PM(2.5)and PM(10)using different receptor models during 2013-2016 in Delhi, India
Get PDFThe present work deals with the seasonal variations in the contribution of sources to PM(2.5)and PM(10)in Delhi, India. Samples of PM(2.5)and PM(10)were collected from January 2013 to December 2016 at an urban site of Delhi, India, and analyzed to evaluate their chemical components [organic carbon (OC), elemental carbon (EC), water-soluble inorganic components (WSICs), and major and trace elements]. The average concentrations of PM(2.5)and PM(10)were 131 +/- 79 mu g m(-3)and 238 +/- 106 mu g m(-3), respectively during the entire sampling period. The analyzed and seasonally segregated data sets of both PM(2.5)and PM(10)were used as input in the three different receptor models, i.e., principal component analysis-absolute principal component score (PCA-APCS), UNMIX, and positive matrix factorization (PMF), to achieve conjointly corroborated results. The present study deals with the implementation and comparison of results of three different multivariate receptor models (PCA-APCS, UNMIX, and PMF) on the same data sets that allowed a better understanding of the probable sources of PM(2.5)and PM(10)as well as the comportment of these sources with respect to different seasons. PCA-APCS, UNMIX, and PMF extracted similar sources but in different contributions to PM(2.5)and PM10. All the three models extracted 7 similar sources while mutually confirmed the 4 major sources over Delhi, i.e., secondary aerosols, vehicular emissions, biomass burning, and soil dust, although the contribution of these sources varies seasonally. PCA-APCS and UNMIX analysis identified a less number of sources (besides mixed type) as compared to the PMF, which may cause erroneous interpretation of seasonal implications on source contribution to the PM mass concentration
Improved Measurement Capabilities in Pneumatic Pressure Measurements at NPLI Through Re-establishment of the Traceability Chain
No full textThis work presents, in brief, the recently concluded extensive in-house inter-comparison of the pneumatic pressure standards at CSIR-National Physical Laboratory, India (NPLI) and the resulting marginal improvement in our measurement uncertainties. The measurements are traceable to the Ultrasonic interferometer manometer (UIM), our low-pressure primary pressure standard as well as to the national primary standard in pneumatic pressure, NPLI-P1. The inter-comparisons and the subsequent estimations of measurement uncertainties, starting from the UIM, were carried out in the overlapping pressures, ranging from 0.01 to 40 MPa. In addition, the large-diameter piston gauge, the pneumatic primary standard was also used to establish the traceability chain. A summarized description of the extensive exercise undertaken is given herein which describes the stability and the excellent agreement with previously reported results as well as successful improvement owing to better control over experimentation as well as environmental factors
Intrinsic Sub-Nanocrystalline Silicon Thin Films: Active Layer for Solar Cells
No full textThe study presents the typical aspects of silicon thin films in terms of growth under variation of applied power using Radio frequency Plasma Enhanced Chemical Vapor Deposition technique (RF-PECVD). The corresponding material found to maintain the typical properties of amorphous nature without compensating the structural modification in terms of crystallinity and has been defined as a material having the "sub-nanocrystalline phase". Characterizations like, UV-Visible spectroscopy, Photoluminescence and Temperature dependent conductivity was used to effectively map the structural details along with electrical and optical properties. The optical bandgap of the films found to be vary from 1.77 eV to 1.99 eV with typical photoresponse variations in the range 10(3) to 10(1). At 30 W applied power, the transition regime observed with the formation of sub-nanocrystallites. The analysis of such phase reveals the superior optoelectronic properties. This article suggests the suitability of sub-nanocrystalline silicon thin films to replace hydrogenated amorphous silicon in various applications
Highly efficient flexible perovskite solar cells and their photo-stability
No full textWe report a simple method to fabricate highly efficient and robust flexible perovskite solar cells (F-PSCs) along with their photo-stability. The solar cells were prepared on indium tin oxide (ITO) coated polyethylene terephthalate substrates. The solar cells incorporated methylammonium lead iodide chloride (CH3NH3PbI3-xClx) perovskite as the light absorber, tin oxide (SnO2) as the electron transport layer (ETL), Spiro-MeOTAD as the hole transport layer and Ag as the top electrode. This structure exhibited a very high external quantum efficiency (EQE) of similar to 80% at 500 nm and a power conversion efficiency (PCE) of 12.7%+/- 0.6% (active area 9.6 mm(2)) with multiple bending cycles showing no effect on the performance, even after 100 bending cycles. To evaluate their lifetime in the dark and under actual operating conditions, a systematic study was performed on the unsealed devices. The solar cells showed a halflife (T-50) of about 340 h when stored in the dark in an ambient environment, but they degraded very rapidly in direct sunlight. The main reason behind their degradation was found to be the rapid degradation in their short circuit current density (J(sc)). The same device design was processed to fabricate large area flexible solar modules with an area of 5x5 cm(2) (active area 15.84 cm(2)) and the solar modules exhibited PCE of 5.6%+/- 0.2%. Substantial loss of PCE in the modules compared to small area devices has been attributed to the larger series resistance of the longer ITO electrodes used in the modules
Influence of wheel speed and ageing on nanostructure and magnetic properties of Cr-doped MnBi magnetic material
Get PDFIn the present work, Mn47Bi50Cr3 ribbons were synthesised employing melt spinning at different wheel speeds ranging from 16 to 28 m/s, to study the effect of quenching rate on the microstructure, morphology and magnetic properties of rapidly solidified alloy. X-ray diffraction studies indicate that the FWHM of diffraction peaks for MnBi increases with the increase in wheel speed, leading to a concurrent decrease in the mean grain size. This could be attributed to the high cooling rate causing homogeneous nucleation leading to refined grain size. The maximum value of coercivity of 11.9 kOe and saturation magnetisation of 54.2 emu/g was obtained for the alloy melt spun at 20 m/s, indicating dependence of coercivity on the grain size, and its orientation, which is largely controlled by the wheel speed. Also, XRD pattern confirms that the MnBi phase fraction is found to be maximum at this wheel speed. Therefore, high-performance nanocrystalline Mn47Bi50Cr3 magnetic material has been synthesised by adjusting the wheel speed and thereby tuning the quench rate. In addition, the phase transformation and variation with respect to temperature and time were studied using thermal analysis technique. Stability of magnetic properties of the alloy with respect to time was also studied after the ageing process
LIDAR OVERLAP FUNCTION DETERMINATION USING THE RAMAN LIDAR SIGNALS
Get PDFThe determination of vertical distribution of optical properties of clouds and aerosols using the lidar system is affected by the incomplete overlap between the field of view of transmitter i.e. laser beam & the receiver in the near-field range. Thus, the study of vertical profiles of aerosol optical properties in the lower atmosphere is erroneous without the correction of lidar overlap function. Here we have analysed the effect of overlap using a simple technique proposed by Ansmann and Wandinger to determine overlap function. We have determined the overlap factor for 5 different days of June 2016 and then calculated the mean overlap profile and determined the relative deviation of each day with respect to mean overlap factor. Results reveal that the complete overlap was achieved beyond 300 meters
Localized Surface Plasmon Resonance Studies on Pd/C Nano-Composite System: Effect of Metal Concentration and Annealing Temperature
Get PDFThe effects of metal concentration and annealing temperature on the localized surface plasmon resonance (LSPR) properties of the Pd nanoparticles (NP) dispersed in carbon were investigated. The Pd/C nano-composite thin films with 7 to 39 atomic % concentration of metal content were deposited using the atom beam co-sputtering techniques and subjected to annealing at temperature varying from 300 degrees C to 600 degrees C. The UV-vis spectroscopy studies on as-prepared films displayed a Mie scattering profile, but not well-defined LSPR bands were observed for all the values of Pd concentration. This is attributed to the smaller size (3-4 nm) of Pd NPs and rough Pd/C interface, as confirmed from TEM studies. When samples were annealed at a temperature of 300 degrees C, three broad LSPR absorption bands in the visible region, along with a sharp peak at 210 nm, were observed and the effect of Pd concentration variation was insignificant on their position. The multiple LSPR bands were observed due to agglomeration NPs, which is consistent with earlier reports and is also observed in the TEM images. When annealing temperature was subsequently increased to 500 degrees C, a blue shift in the LSPR peak position with an increase in the Pd concentration was observed, which phenomena is attributed to the formation of bigger NPs with the formation of sharp NPs-interface at high temperature upon annealing. A monotonic increase in the magnitude and decrease in the FWHM with an increase in concentration suggested change in the dielectric function of sample due to the growth of NPs. This is further confirmed from XRD studies, where strain relaxation and grain growth were observed. The intensity of the SPR peak decreased with an increase in the annealing temperature. The LSPR peak disappeared on annealing at a temperature of 600 degrees C, suggesting the formation of continuous polycrystalline thin films of Pd. In summary, NPs size, metal matrix interface, and concentration of metal play key roles in the tailoring the LSPR properties of the Pd
Metal oxide-nanoparticles and liquid crystal composites: A review of recent progress
No full textLiquid Crystals (LCs) are soft materials lying in the midway between solids and liquids which have enjoyed considerable success due to their tremendous display and non-display applications in various areas of science and technology such as physics, chemistry, biology, material science, telecommunication etc. On the other hand, nanotechnology, an emerging research area, has brought revolutionary developments through its nanomaterials and nanoscale approaches creating enormous expectations over the number of years. In order to enhance various electro-optical, dielectric, physico-chemical properties, structural rearrangements of LCs, much work has been done through the incorporation of suitable nanoscale dopants into the host LC material. Metal oxide nanoparticles (MO-NPs) have attracted a great deal of interest on the grounds of their diverse properties in the recent times. Taking advantage of their varied desirable aspects, researchers have successfully dispersed suitable MO-NPs in LCs for winning noteworthy outcomes. In this review article, we have revisited successful doping of MO-NPs in LCs and observed that the doping established by mastering the intricacies of working with LCs and MO-NPs, their composites had resulted in desired and effective properties. This review deals with the detailed analysis of the contribution of MO-NPs in the domains of LCs and their applications. The focus in this work is laid on the doping effects of MO-NPs in various LCs and developing status of doping MO-NPs in LCs. The parameters which got affected after doping have also been summarized according to the type of MO-NPs doped. An extended analysis of the characteristics that were enhanced or suppressed after doping is systematically reviewed. Based on these discussions, possible future outcomes and prospects that might lead to major developments in the scientific technology regarding this work are put forward