Proton Nuclear Magnetic Resonance-Based Method for the Quantification of Epoxidized Methyl Oleate

Epoxidized methyl esters (EMO) with their high oxirane ring reactivity, acts as a raw material in the synthesis of various industrial chemicals including polymers, stabilizers, plasticizers, glycols, polyols, carbonyl compounds, biolubricants etc. EMO has been generally quantified by the gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. Taking into the account of the limitations of these techniques, two qHNMR-based equations have been proposed for the quantification of EMO in the mixture of EMO and methylesters (MO). The validity of the proposed method was determined using standard mixtures of MO and EMO having different molar concentrations. The developed equations have been applied on the samples of EMO prepared from oleic acid in two-step process viz., esterification followed by epoxidation. The qHNMR-based EMO quantification showed acceptable agreement with the results obtained from HPLC analysis.     

A climatological study of the spatio-temporal variability of land surface temperature and vegetation cover of Vadodara district of Gujarat using satellite data

In the present study, a comprehensive assessment of the spatio-temporal variation of day-time and night-time land surface temperature (LST) and normalized difference vegetation index (NDVI) of Vadodara district of Gujarat in India from 2001 to 2012 has been carried out using satellite data. A significant cooling trend was observed in the day-time LST, whereas the night-time LST showed a distinct warming trend. The entire geographical extent of Vadodara was classified into different night-time LST classes to quantify the extent of the hot pockets, and it showed a clear-cut warming pattern for all the months of the year with an increase in the geographical areas under higher temperature range. Further analysis of Diurnal Temperature Range (DTR) also revealed a strong impact of the urbanization process, with annual DTR showing a decreasing trend at the rate of 0.29°C year^?1. An analysis of the vegetation cover of the district showed that on an average, the NDVI of the district increased during the study period. However, a micro-level examination of NDVI values depicted that the type of vegetation cover had drastically changed. The maximum NDVI values for months from May to December for 2012 were much lower than those of 2001 and 2006, indicating a change in vegetation pattern of the district. An assessment of the area under different NDVI values exhibited that for all the months of the year (except September), the total area with NDVI values of higher range (i.e. +0.5 and above) had substantially decreased from 2001 to 2012. The analysis revealed that for some of the months like February, while in 2001, 45% of district exhibited NDVI values above +0.5, but by 2012, it had decreased to only 18%, showing a drastic change in vegetation type and deterioration of the extent of thick dense vegetation.     

Traffic grooming and clique partitioning‐based spectrum assignment in elastic optical networks

We adopt a fragmentation reducing policy for spectrum assignment and incorporate it with multicast traffic grooming in EON. To reduce fragmentation, the spectrum is partitioned based on the clique partitioning approach and spectral slots are assigned to traffic demands depending on which partition they belong. Simulation results predict that the proposed approach has better spectrum slot utilization compared to the state‐of‐the‐art non‐partitioning approach and the proposed approach reduces fragmentation, and also has less blocking ratio compared to the state‐of‐the‐art partitioning approach.     

Synthesis,characterization and luminescence studies of rare earth activated Sr<Subscript>2</Subscript>SiO<Subscript>4</Subscript> phosphor: a review

This review includes research papers on different method of preparation of rare earth activated Sr₂SiO₄ phosphors and its luminescence studies. Here in Sr₂SiO₄ has attracted great interest due to its special structure features, excellent physical and chemical stability. Besides, it absorbs ultraviolet radiation and emits white light when activated by different rare earth ions. Different synthesis techniques were compared and it is found that sol–gel synthesis technique is best for preparation of rare earth activated Sr₂SiO₄ phosphors. Literature related to characterization techniques such as X-ray diffraction techniques, scanning electron microscopy, transmission electron microscopy and other studies are also compared. Photoluminescence studies for white light emitting diode of various rare earth phosphors are compared with Sr₂SiO₄ phosphor reported in this review. Also some luminescence techniques such as thermoluminescence glow curve analysis and some spectroscopic parameters are also compared. The review end with some important conclusion related to rare earth activated Sr₂SiO₄ phosphors with proper justifications.     

Hikami-Larkin-Nagaoka (HLN) Treatment of the Magneto-Conductivity of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> Topological Insulator

We report the magneto-conductivity analysis at different temperatures under a magnetic field of up to 5 T of a well- characterized Bi₂Te₃ crystal. Details of crystal growth and various physical properties including high linear magneto-resistance are already reported by some of us. To elaborate upon the transport properties of Bi₂Te₃ crystal, the magneto-conductivity is fitted to the known Hikami-Larkin-Nagaoka (HLN) equation and it is found that the conduction mechanism is dominated by both surface-driven weak anti-localization (WAL) and the bulk weak localization (WL) states. The value of HLN equation coefficient (α) signifying the type of localization (WL, WAL or both WL and WAL) falls within the range of ??0.5 to ??1.5. In our case, the low-field (±?0.25 T) fitting of studied crystal exhibited a value of α close to ??0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (l_φ) is found to decrease from 98.266 to 40.314 nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi₂Te₃ follows the HLN equation and quantitative analysis of the same facilitates to know the quality of studied crystal in terms of WAL to WL contributions and thus the surface to bulk conduction ratio.     

Dual Wide Band Circularly Polarized Microstrip Patch Antenna with Offset Feed

Wireless Personal Communications - A compact, dual band circularly polarized antenna has been proposed and investigated. It has been designed with single feed and has simple structure. The antenna...     

Continuous User Authentication System: A Risk Analysis Based Approach

With the expansion of smart device users, the security mechanism of these devices in terms of user authentication has been advanced a lot. These mechanisms consist of a pattern based authentication, biometric based authentication, etc. For security purpose whenever a user fails to authenticate themselves, these devices get locked. But as these devices consist of numerous applications (document creator, pdf viewer, e-banking, Social networking app, etc.), locking of the whole devices prevents the user from using any of the applications. Since the variety of applications provided by the devices have different security needs, we feel it is better to have application level security rather than device level. Here, in this paper, we have proposed a behavioral biometric based user authentication mechanism for application level security. First, we have performed a risk assessment of different applications. Then for complete protection, static multi-modal (keystroke and mouse dynamics) authentication at the start of an interactive session, and a continuous keystroke authentication during this session is performed. An analysis of the proposed authentication mechanism has been conducted on the basis of false acceptance rate (FAR), false rejection rate (FRR) and equal error rate (EER). The static multi-modal authentication achieved a FAR of 0.89%, FRR of 1.2% and EER of 1.04% using J48 classification algorithm. Whereas the continuous keystroke authentication has been analyzed by the time (no. of keystrokes pressed) taken to capture an intruder.

     

Capability of DICE Circuit to Withstand Ionizing Radiations

Memory devices continue to be an irreplaceable part of most semiconductor circuits. This is expected to continue to rise in the coming years. Thus, there is a need to incorporate radiation hardness in all memory elements. There are numerous techniques to make a circuit immune to radiations at processing level, circuit level or design level. One of the most accepted methods of achieving resilience to radiations at design level is DICE (Dual Interlocked Storage Cell). The efficiency and range of operation of DICE structure can be improved through various factors. Sizing of transistors as well as pulse width and amplitude of striking pulse of radiation are key parameters in determining successful circuit operation. Effect of varying these parameters on the circuit operation is studied with the help of simulation results. The self restoring logic in the design has a certain threshold after which the circuit is unable to regain its original value.

     

Function Follows Form: Correlation between the Growth and Local Emission of Perovskite Structures and the Performance of Solar Cells

Understanding the relationship between the growth and local emission of hybrid perovskite structures and the performance of the devices based on them demands attention. This study investigates the local structural and emission features of CH₃NH₃PbI₃, CH₃NH₃PbBr₃, and CH(NH₂)₂PbBr₃ perovskite films deposited under different yet optimized conditions using X‐ray scattering and cathodoluminescence spectroscopy, respectively. X‐ray scattering shows that a CH₃NH₃PbI₃ film involving spin coating of CH₃NH₃I instead of dipping is composed of perovskite structures exhibiting a preferred orientation with [202] direction perpendicular to the surface plane. The device based on the CH₃NH₃PbI₃ film composed of oriented crystals yields a relatively higher photovoltage. In the case of CH₃NH₃PbBr₃, while the crystallinity decreases when the HBr solution is used in a single‐step method, the photovoltage enhancement from 1.1 to 1.46 V seems largely stemming from the morphological improvements, i.e., a better connection between the crystallites due to a higher nucleation density. Furthermore, a high photovoltage of 1.47 V obtained from CH(NH₂)₂PbBr₃ devices could be attributed to the formation of perovskite films displaying uniform cathodoluminescence emission. The comparative analysis of the local structural, morphological, and emission characteristics of the different perovskite films supports the higher photovoltage yielded by the relatively better performing devices.