654 research outputs found
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Enhanced sensitivity refractive index sensor based on segmented fiber with bending.
Get PDFA refractive index sensor fabricated by splicing segments of multimode and single mode fibers was investigated for enhanced sensitivity. The investigation revealed that when this sensor is used in bent position its sensitivity is improved by a factor of 5 to 10 depending on its bend curvature. It was found that the sensitivity is enhanced as the curvature is increased
Simulation and experimental characterization of Raman/EDFA hybrid amplifier with enhanced performance
No full textWe present simulation and experimental characterization of a hybrid amplifier comprising of a Raman amplifier and an erbium doped fiber (EDF) amplifier, with enhanced performance. The incorporation of a pumped EDF section in a fiber Raman amplifier (FRA) employing a dispersion compensating fiber is demonstrated to provide superior performance than a sole FRA system. The hybrid amplifier is characterized in terms of single channel gain and noise figure, and the results of measurements are shown to be in close agreement with the simulated results. Polarization-dependent gain (PDG) and multi-channel measured and simulated gain characterization of the Raman/EDFA hybrid amplifier are also presented
Genetic Algorithm Based Node Placement Methodology For Wireless Sensor Networks
No full textA Genetic Algorithm based multi-objective methodology was implemented for a self-organizing wireless sensor network. Design parameters such as network density,connectivity and energy consumption are taken into account for developing the fitness function. The genetic algorithm optimises the operational modes of the sensor nodes along with clustering schemes and transmission signal strengths. The algorithm has been implemented in MATLAB using its Genetic Algorithm toolbox along with custom codes. The optimal designs so achieved by the algorithm conform to all the design parameters
Characterization of solvatomorphs of methotrexate using thermoanalytical and other techniques
No full textIdentification and characterization of different forms of methotrexate were carried out by crystallization from different solvents. Five different forms of the drug were obtained. Appearance of a desolvation endotherm in the DSC accompanied by mass loss in TGA for forms I, II, IV and V showed these forms to be acetonitrile solvate hydrate (form I), trihydrate (forms II and IV) and dimethylformamide solvate (form V), respectively. However, the desolvation peak was absent in form III (obtained from methanol) indicating the absence of any solvent of crystallization. This form was found to be partially crystalline by its XRPD pattern. Solution calorimetry was further used to differentiate between the forms as they differ in lattice energy, resulting in different enthalpies of solution. The dissolution and solubility profiles were correlated with the enthalpy of solution and subsequently with crystallinity of all the forms; the least endothermic form (form III) had the highest dissolution rate
Embedded dual fiber Bragg grating sensor for simultaneous measurement of temperature and load (strain) with enhanced sensitivity.
No full textAn embedded dual fiber Bragg gratings sensor for simultaneous measurement of temperature and load (strain) is proposed and experimentally demonstrated. Two nearly identical gratings are mounted on opposite side of an arch-shaped steel strip. The grating in concave and convex position experiences equal blue and red shift, respectively, due to bending of the strip which is exploited in temperature and load (strain) discrimination. The temperature and load (strain) sensitivity of the sensor improves to 28.5 pm/°C and 2.8 pm/g (2.6 pm/με). The sensor can measure temperature and load (strain) accurately with small error of ±1°C and ±1 g, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1621–1624, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24439
Poddar,1 Nahar Singh,1 ,1
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Non destructive Brix evaluation of apples of different origin using near infrared (NIR) filter based reflectance spectroscopy
No full textA filter based near infrared (NIR) technique to evaluate Brix value, in a non destructive way, of Indian apples, along with apples from other countries, has been investigated here. Reflectance characteristics at ten NIR wavelengths were recorded by in-house developed probe for five Indian varieties and four imported varieties. A separate calibration and validation set for each variety was formed. Brix values of the calibration and validation sets of apples were evaluated with a refractometer from Bellingham and Stanley, Model 840. Principal component regression was used to generate calibration and prediction of Brix for the validation set. It was found that Brix values of all varieties of apples can be predicted with a standard error of prediction, 0.7322-1.7809, while root mean square error is also in the same range. It was further noticed that reduction in data recording wavelength leads to an increase in SEP and RMSE
Study of photoluminescence quenching and DC conductivity measurements in polymer-SWNT composite films for various SWNT concentrations
No full textConducting polymer-SWNT composite films have a high potential in the area of photovoltaic devices and light emitting diodes (LEDs). SWNTs have high electron affinity and high mobility for electrons. As a result of this, the separation of photoinduced charges in the solar cell is very fast and efficient. For LEDs, the polymer-SWNT composite films act as efficient electron transporting layer (ETL). In the present work, composite solutions of P3HT and SWNTs were prepared in 1,2-dichlorobenzene with nanotube to polymer mass ratios varied from 0% to 30%. The films from this solution were spin coated on a glass substrate with the help of spinner keeping the film thickness ∼100 nm. The photoluminescence (PL) of the film was observed with the help of Shimadzu Spectrofluorophotometer. It was found that the PL intensity decreases by ∼90% as the concentration of the SWNT is increased from 0% to 30%. This decrease is due to the transfer of electrons from P3HT to SWNTs before the exciton in the polymer can decay radiatively to emit PL. DC conductivity of the composite films was measured with the help of Keithley sourcemeter in sandwich structures. It was found that conductivity increases by more than five orders of magnitude with the increase of SWNT concentration. The composite films can therefore act as good electron transporter for LEDs and efficient electron acceptor for solar cells
Study of chemical composition and morphology of airborne particles in Chandigarh, India using EDXRF and SEM techniques
No full textThe elemental composition and morphology of aerosols, collected from March 95 to February 96 and March 96 to August 96 respectively in the city of Chandigarh, India is determined using Energy Dispersive X-ray fluorescence and scanning electron microscopic techniques. The elemental concentration levels are found to be higher by a factor of 2-7 in the spring season as compared to the rainy season. The concentration of spherical and non-spherical (i.e. elongated) aerosols is more in the spring season and is reduced drastically in the rainy season due to the prominent wash out effect of rains. More accurate particle classification and source identification is obtained when based on combination of chemical composition and particle morphology. Possible sources identified from this analysis are soil dust, Industrial activity, Agricultural and Garbage burning, Maritime aerosols and Automobile exhaust
Optical characterization of ZnO nanoparticles capped with various surfactants
No full textThe presence of surfactants (Hexamine, tetraethylammonium bromide (TEAB), cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB) and PVP) on the surface of zinc oxide (ZnO) nanoparticles resulted variation in their optical properties. The optical properties of each surfactant-capped zinc oxide nanoparticles were investigated using UV–visible absorption and fluorescence techniques. The particle size of these nanoparticles were calculated from their absorption edge, and found to be in the quantum confinement range. The absorption spectra and fluorescent emission spectra showed a significant blue shift compared to that of the bulk zinc oxide. Large reduction in the intensity of visible emission of zinc oxide/surfactant was observed and these emissions were vanished more quickly, with the decrease in excitation energy, for the smaller nanoparticles. Out of the four surfactants (other than PVP), CTAB-capped zinc oxide has smallest particle size of 2.4 nm, as calculated from the absorption spectrum. Thus the presence of surfactant on the surface of zinc oxide plays a significant role in reducing defect emissions. Furthermore, ZnO/PVP nanoparticles showed no separate UV emission peak; however, the excitonic UV emission and the visible emission at 420 nm overlap to form a single broad band around 420 nm
Comparative Study of synthesis, characterisation and electric properties of polypyrrole and polythiophene composites with tellurium oxide
No full textThe study involves the synthesis of polypyrrole (PPY) and polythiophene (PTP) composites of TeO2 via in situ oxidative polymerization procedure. These composites were characterized by FTIR, XRD and SEM, which proves the successful chemical synthesis of PPY, PTP and their composites. FTIR absorption peaks confirms the insertion of TeO2 in the backbone of PPY and PTP and also justifies the strong interaction of TeO2 with PTP than PPY, which is responsible for a significant increase in the conductivity value in case of PTP composite than PPY composite, which ensures its better capability in future electronics. Thermal analysis shows no change in thermal stability unlike composites of PPY and PTP with other metal oxides, hence rules out the application of these composites for higher temperature purposes, however, the PTP composite material has shown the stability up to 200 °C which ensures its use in low temperature applications. The compactness, ordered morphology, better conjugation or chain length and orientation of TeO2 with PTP backbone are responsible for more conductivity of PTP composite than PPY