IR@NPL
Not a member yet
3815 research outputs found
Sort by
Mid-Latitude Spread-F Structures Over the Geomagnetic Low-Mid Latitude Transition Region: An Observational Evidence
No full textAn observational evidence of a unique plasma depletion event was captured by an O(D-1) 630.0 nm airglow imager on 13 June 2018 over a transition region of geomagnetic low-mid latitude, Hanle, Leh Ladakh, India (32.77 degrees N, 78.97 degrees E; Mlat. similar to 24.1 degrees N). The observed plasma depletion structures are tilted at an angle of 13 degrees 2 degrees west of the geomagnetic north and drifted toward west. Collocated Global Navigation Satellite System-Total Electron Content measurements confirm that the structures are indeed associated with TEC depletions. Simultaneous ionosonde measurements from Delhi, India (28.70 degrees N, 77.10 degrees E; Mlat. similar to 20.2 degrees N) shows spread-F signatures confirming that these structures are associated with the ionospheric irregularities. Interestingly, radar observations over the geomagnetic low-latitude station Gadanki, India (13.5 degrees N; 79.2 degrees E; Mlat. similar to 6.5 degrees N) reveal the absence of equatorial plasma bubbles on this night. Therefore, these observations strongly suggest that the observed structures in the airglow images over Hanle are associated with mid-latitude spread-F (MSF). These MSF structures are possibly affected by the shear in the zonal plasma drift that forces the field aligned plasma irregularity structures to tilt toward west. These observations, for the first time, bring out the presence of MSF structures over geomagnetic low-mid latitude transition region. It is suggested that the plasma distribution over low latitudes plays an important role in the occurrence of MSF structures over this transition region. Understanding the source and characteristics of the plasma irregularity structures over this transition region can help in understanding the spatio-temporal evolution of global L-band scintillation in a better way.
Plain Language Summary Understanding the spatio-temporal distribution of the ionospheric plasma irregularities is important in the operational forecasting of L-band scintillation and therefore has important ramifications in the satellite-based communication and navigation systems. Traditionally, plasma irregularities in the low and mid-latitudes had received focused attentions in the past with very less attention has been paid over the low to mid-latitude transition region. The present investigation provides an attempt toward that direction and proposes a mechanism on the relationship between the plasma distribution over low latitudes and the occurrence of the mid-latitude plasma irregularities over the geomagnetic low-mid latitude transition region. Comprehensive investigations are further needed in the future to understand and characterize the ionospheric plasma irregularity structures over this region
Investigations on key aspects of solution growth L-Alanine strontium chloride trihydrate single crystal for non-linear optical and photonic applications
No full textIn the modern era materials with high NLO efficiency, better mechanical and thermal properties are on leading edge and highly demanded for their efficient use in optical communication and fibers optics. In the present course of work, authors have grown successfully single crystals of L-alanine strontium chloride trihydrate(LASRT) by slow evaporation solution and slow cooling techniques so as to meet the demand of industries. Structure of the grown crystal with lattice parameters were confirmed by employing powder XRD technique. Mechanical strain present in the lattice is determined as -7.066 x 10(-2) by Williamson-Hall relation. The newly grown crystals were subjected to HRXRD to assess crystal perfection and various types of defects. In this research, quality of the grown crystals is found moderately good. The specimen has better transmission nearly 44% as indicated by UV-Vis spectra. Various remarkable parameters like optical band gap, reflectance, refractive index, extinction coefficient and electrical susceptibility are determined. Some important electronic parameters are calculated by using Claussius-Mossottee relation. Thermal properties were also investigated in detail by subjecting the crystals to TGA/DTA measurements. By photo acoustic analysis, thermal diffusivity (alpha) is found 1.8816 x 10(-6) m(2)/s which indicates large heat bearable capacity of the grown sample. Mechanical stability of LASRT is determined larger than already reported LOMHCl and LLHBr single crystals by Nano-indentation technique. Results for nonlinear optical testing, crystalline perfection and optoelectronic parameters indicate its suitability for laser applications
Long-term impacts of integrated nutrient management with equivalent nutrient doses to mineral fertilization on soil organic carbon sequestration in a sub-tropical Alfisol of India
Get PDFLimited evidence is available on carbon sequestration potential of long-term integrated nutrient management (INM) versus mineral fertilization, when equivalent amounts of nutrients were added. Hence, this study was carried out to understand the impact of 60 years of INM with adjusted nutrient doses and mineral fertilization in an Alfisol in a maize (Zea maysL.)-wheat (Triticum aestivumL.) system on soil organic carbon (SOC) sequestration in surface (0-30 cm) and deep (30-60 cm) soil layers. Conventional tillage was done twice before sowing of both maize and wheat using a spade. In farmyard manure (FYM) and lime treated plots (FYMP'K'L: plots with nitrogen (N) applied in terms of FYM; additional dose of phosphorus (P) and potassium (K) and lime) total SOC concentration was nearly 83% higher than unfertilized control plots. The FYMP'K'L plots had similar to 11% more total SOC concentration than plots treated with mineral fertilizer and lime (NPKL: recommended dose of N, P, K and lime) in the 0-30 cm soil layer. Labile C, including KMnO4-C, was more in plots with FYM than NPKL plots, whereas the recalcitrant C stock was more in NPKL than FYM treated plots. In the 0-60 cm soil layer, the labile C stock was highest in FYMP'K'L plots, but the recalcitrant C stock was highest in NPKL. Total SOC accumulation rate (over unfertilized control plots) was highest for FYMP'K'L plots (0.38 Mg ha(-1 )year(-1)) in the surface soil layer, whereas SOC sequestration rate was highest in NPKL plots (0.18 Mg ha(-1 )year(-1)) in the deep layer and in the 0-60 cm layer. Overall, although NPKL management practice had the highest C sequestration in the 0-60 cm layer, FYMP'K'L had the best CMI and labile C pools. Thus, resource poor farmers need not to use full doses of NPK and FYM for soil C management in the region
Partial Pressure Assisted Growth of Single-Layer Graphene Grown by Low-Pressure Chemical Vapor Deposition: Implications for High-Performance Graphene FET Devices
Get PDFAn attempt has been made to understand the thermodynamic mechanism study of the low-pressure chemical vapor deposition (LPCVD) process during single-layer graphene (SLG) growth as it is the most debatable part of the CVD process. The intensive studies are being carried out worldwide to enhance the quality of LPCVD-grown graphene up to the level of mechanically exfoliated SLG. The mechanism and processes have been discussed earlier by several research groups during the variation in different parameters. However, the optimization and mechanism involvement due to individual partial pressure-based effects has not been elaborately discussed so far. Hence, we have addressed this issue in detail including thermodynamics of the growth process and tried to establish the effect of the partial pressures of individual gases during the growth of SLG. Also, optical microscopy, Raman spectroscopy, and atomic force microscopy (AFM) have been performed to determine the quality of SLG. Furthermore, nucleation density has also been estimated to understand a plausible mechanism of graphene growth based on partial pressure. Moreover, the field-effect transistor (FET) device has been fabricated to determine the electrical properties of SLG, and the estimated mobility has been found as similar to 2595 cm(2) V-1 s(-1) at n = -2 x 10(12) cm(-2). Hence, the obtained results trigger that the partial pressure is an important parameter for the growth of SLG and having various potential applications in high-performance graphene FET (GFET) devices
Assessment of optical, mechanical and nonlinear properties of potassium acid phthalate single crystal: a potential candidate for optoelectronic applications
Get PDFA good optical quality semi-organic single crystal of Potassium Acid Phthalate (KAP) was harvested from aqueous solution by using slow evaporation solution growth technique (SEST) at ambient condition. The defect free single crystal of KAP was analyzed by different instrumentation techniques, for checking its compatibility for different applications. Its unit cell dimensions and phase purity was examined by powder X-ray diffraction (PXRD) and found that it crystallizes in orthorhombic with non-centrosymmetric in nature. The quality of the grown ingot was assessed by high resolution X-ray diffraction (HRXRD) technique and found that, the crystalline quality is better with less grain boundaries. Its optical properties were scrutinized by UV-vis., photoluminescence (PL) and time resolved photoluminescence (TRPL) measurements respectively. The mechanical stability of the grown crystal was tested by Vickers microhardness method and found that the grown crystal shows indentation size effect (ISE) which was explained using different theoretical models. Its third order nonlinear optical properties were studied by Z-scan measurement by using Ti:Sapphire laser as a source and determined its nonlinear absorption coefficient (beta) and it was found that the KAP crystal is one of the preferable choices for optical limiting applications
A facile fabrication of poly(methyl methacrylate)/α-NaYF4:Eu3+ tunable electrospun photoluminescent nanofibers
No full textThe photoluminescent nanofibers (PLNs) were successfully produced by incorporating α-NaYF4:Eu3+ nanophosphor into the polymethylmethacrylate (PMMA) matrix using electrospinning technique. The morphology of PLNs was investigated by scanning electron microscope (SEM) with the diameter in the range of 165–450 nm. The nanofibers revealed hypersensitivity in emission regime from orange to red (589–707 nm) with 5% concentration of nanophosphor at the excitation wavelength of 239 nm. X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy confirm the uniform co-ordination (dispersion) of nanophosphor with the carbonyl group of PMMA molecular chain. The PMMA/ α-NaYF4:Eu3+ composite nanofibers have the potential application in colored light-emitting diode (LED)
Nickel substituted oxygen deficient nanoporous lithium ferrite based green energy device hydroelectric cell
No full textIn green energy generation, recently Hydroelectric cell (HEC) by dissociating the water molecules at room temperature has taken a big stride among other alternative green energy sources. In this work, another unique novel material Ni substituted lithium ferrite (LNFO) for the fabrication of hydroelectric cell to generate green electricity has been reported. Oxygen deficient nanoporous LNFO has been synthesised by the Solid-State reaction method. Special processing steps were taken to control oxygen defect's concentration in the ferrite by varying pre-sintering temperature during its synthesis to deliver more power output. Phase formation of nickel substituted lithium ferrite has been confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The porous microstructure of LNFO has been analysed by Field-emission scanning electron microscope (FESEM) micrographs, BET and DFT techniques. The presence of defects and decrease in their concentration with the increase in pre-sintering temperature has been confirmed by analysing X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. Hydroelectric cell fabricated using LNFO pellets pre-sintered at 750 degrees C and 800 degrees C, delivered output current densities of 3.8 mA/cm(2) and 3.6 mA/cm(2) respectively. The decrease in output current is attributed to reduction in defect concentration as confirmed by PL and XPS spectrum. Generated current densities are two times higher than reported in lithium substituted magnesium ferrite based hydroelectric cell (1.7 mA/cm(2))
Hydroelectric Cell Based on a Cerium Oxide-Decorated Reduced Graphene Oxide (CeO2-rG) Nanocomposite Generates Green Electricity by Room-Temperature Water Splitting
No full textNon-photocatalytic water splitting by oxygen-deficient, mesoporous metal oxide-engineering-based hydroelectric cell (HEC) as a path-breaking invention to generate electricity is a well-known phenomenon. To obtain more electricity from HEC, the metal oxide with higher oxygen deficiency is a better option; therefore, use of CeO2 would be a better choice in the present work. Oxygen-deficient mesoporous CeO2, CeO2-rG1, and CeO2-rG2 nanocomposites have been synthesized by the one-step wet precipitation method. Increase in oxygen vacancies in the presence of Ce3+ concentration by the intense F-2g peak in Raman spectra of CeO2-rGO nanocomposite is compared to CeO2. The strain developed in the CeO2 lattice because of defect creation has been verified by high-resolution transmission electron microscopy images and X-ray diffraction. Defect pair formation in nanocomposite emits visible emission were taken by photoluminescence spectroscopy. Addition of rGO in CeO2 improved the surface area from 60.57 to 74.49 m(2)/g, which is confirmed by Brunauer-Emmett-Teller measurements. In HEC, water molecules are chemidissociated on the oxygen-deficient mesoporous surface of the pellet followed by physidissociation of water molecules at mesopores. Current is produced by redox reaction of dissociated ions at the Zn anode and Ag cathode attached to the nanocomposite pellet. Nanocomposite CeO2-rG(2)-based HEC delivers a short circuit current of 21.3 mA and an open-cell voltage of 0.84 V by adding few drops of water. CeO2-rG(2)-based HEC of an area of 4.8 cm(2) delivers a maximum power of 17.66 mW which is 2.25 times higher than the reported power of 7.84 mW for Li-magnesium ferrite-based HEC. Addition of rGO in highly resistive CeO2 significantly enhanced oxygen vacancies and mesoporosity, which improved the output power of HEC
Influence of laser fluence in modifying energy storage property of BiFeO3 thin film capacitor
No full textRecent focus of the research community is on identifying multifunctional materials for the realization of high density energy storage capacitors. Present work focuses on the growth of multifunctional BiFeO3 (BFO) thin films using Pulsed Laser Deposition technique for the energy storage application. Influence of Laser fluence (150 mJ to 250 mJ) on the energy storage density of BFO thin films has been identified. The enhanced energy storage density of 191 mJ/cm(3) has been accomplished for the BFO thin film deposited at 200 mJ incident laser energy, which is higher compared to the earlier available reports. Results indicate that the proper tuning of laser fluence while deposition of BFO thin films is crucial for the realization of optimum energy storage density capacitors
Metal doping in topological insulators- a key for tunable generation of terahertz
No full textThe unique surface edge states make topological insulators a primary focus among different applications. In this article, we synthesized a large single crystal of Niobium (Nb)-doped Bi2Se3 topological insulator (TI) with a formula Nb0.25Bi2Se3. The single crystal has characterized by using various techniques such as Powder X-ray Diffractometer (PXRD), DC magnetization measurements, Raman, and Ultrafast transient absorption spectroscopy (TRUS). There are (001) reflections in the PXRD, and Superconductivity ingrown crystal is evident from clearly visible diamagnetic transition at 2.5 K in both FC and ZFC measurements. The Raman spectroscopy is used to find the different vibrational modes in the sample. Further, the sample is excited by a pump of 1.90 eV, and a kinetic decay profile at 1.38 eV is considered for terahertz analysis. The differential decay profile has different vibrations, and these oscillations have analyzed in terms of terahertz. This article not only provides evidence of terahertz generation in Nb-doped sample along with undoped sample but also show that the dopant atom changes the dynamics of charge carriers and thereby the shift in the Terahertz frequency response. In conclusion, a suitable dopant can be used as a processor for the tunability of terahertz frequency in TI