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An FPGA based all-in-one function generator, lock-in amplifier and auto-relockable PID system
No full textWe report an all-in-onewaveformgenerator, lock-in amplifier and Proportional-Integral-Differential (PID) controller, embedded in a single Field Programmable Gate Array (FPGA). The PID controller is advanced with a novel automatic relocking mechanism, which is capable of self-finding and relocking at the desired setpoint upon unlocking of the PID due to disturbances. The instrument is designed in such a way that these devices can either be used individually or simultaneously. Digital implementation via software processing of the associated modules is used and the firmware is embedded in an FPGA IC, which makes it compact and reconfigurable. The instrument consists of a hardware for establishing external linkage and a Python based computer-controlled interface to control it from a remote PC as well as for acquiring and plotting relevant data. A steep roll-off of the filters (6 dB/octave to 24 dB/octave), low noise density (30 nV/root Hz @ 100 kHz) in the lock-in amplifier and a PID bandwidth of 100 kHz makes it useful for wide range of applications. Versatility of the instrument is demonstrated in three different experiments, (i) Auger electron spectroscopy, (ii) low coherence optical tomography and (iii) laser frequency stabilization followed by self identification of the setpoint upon unlocking and automatic relocking to that
Comparison of Monte Carlo Simulation, Least Square Fitting and Calibration Factor Methods for the Evaluation of Measurement Uncertainty Using Direct Pressure Indicating Devices
No full textAt present, several measuring instruments are commercially available in the market for accurate and precise pressure measurements. In case of electromechanical type pressure sensors, the evaluation of measurement uncertainty is always a tedious task for researchers due to lack of availability of the suitable and well-defined mathematical model. In order to harmonize the method of evaluation of measurement uncertainty associated with measuring instruments, "The Guide to the Expression of Uncertainty in measurement," published by International Standard Organization, is a major directional guide which is equally important in pressure metrology. The present paper describes the various uncertainty propagation models developed for the evaluation of measurement uncertainty associated with direct pressure indicating devices (DPIDs). A detailed comparative study is presented while using Monte Carlo simulation, least square fitting and calibration factor methods for the evaluation of measurement uncertainty using a DPID. In order to judge the feasibility and practical applicability of these contemporary methods, it is demonstrated through an example of a case study on the results thus obtained on a DPID that results using three different approaches are in excellent agreement and quite comparable
Contributions of National Standards on the growth of Barometric Pressure and Vacuum Industries
No full textA rigorous data analysis has been carried out for various barometric pressure transmitters and sensors and vacuum gauges over a period of 8 years; it has been found that a small fraction of pressure and vacuum industries and research institutions from private and government organizations approach to National Metrology Laboratory (NMI), CSIR-NPL, for calibration of their equipment. The observation also pointed out that it might be possible that the traceability chain throughout the country is not properly maintained, especially keeping in view that India is one of the fastest economies in the world
Defect induced broadband visible to near-infrared luminescence in ZnAl2O4 nanocrystals
No full textMaterials emitting over a broad range of wavelengths have been gaining attention consistently owing to their potential applications. ZnAl2O4 has been an attractive material due to its robust luminescence properties. Herein, we report white and intense near-infrared emission, simultaneously, in undoped ZnAl2O4 nanocrystals at a relatively lower temperature (550 degrees C) than reported earlier. Emission is accompanied by various types of shallow and deep donor/acceptor defects, for instance, ionic vacancies and antisite defects existing in the crystal lattice. Switching of white to blue color is observed with annealing owing to rearrangement of defects. Rietveld refinement of X-ray diffraction patterns confirm the presence of multiple defects in the crystal lattice. Transmission electron microscopic analysis has revealed the change in morphology from spherical to polyhedron and increase in crystallite size on annealing. Suitable values of illuminating engineering society colorimetric parameters such as fidelity index, luminous efficiency of radiation, color gamut etc. predict its potential applications in lighting and bioimaging
Dynamic magneto-optical inversion in magnetic fluid using NanoMOKE
No full textSystematic inversion of optical anisotropy with magnetic field sweep (0-5000 Gauss) has been observed at a critical concentration in the monodispersed magnetic fluids using NanoMOKE III. This experimental technique is significantly novel method to investigate the optical anisotropy of magnetic nano-suspensions with the time-varying magnetic field. In this work, we report a detailed experimental investigation on the field dependent magneto-optical behaviour of dilute water dispersed Fe3O4 based magnetic fluid. Magnetic fluid shows tunable magneto-optical properties which primarily depends on parameters such as, particle concentration, composition and carrier medium. We have observed a systematic inversion in optical anisotropy at critical concentration for a Fe3O4 magnetic fluid with strong spatial dependence. The observed tuneable magneto-optical phenomena have been correlated to the net effect of the structuration process, electronic transitions and gravitational force in the presence magnetic field. This phenomenon leads to the development of two particle size distribution, negative optical activity initially and strong spatial dependence respectively. The present results provide a strong correlation with theoretical models presented to expound the dependency of various parameters on magneto-optical inversion behaviour of magnetic fluids
Enhancement in thermoelectric properties due to Ag nanoparticles incorporated in Bi2Te3 matrix
Get PDFThe present study aims to see the enhancement in thermoelectric properties of bismuth telluride (Bi2Te3) annealed at different temperatures (573 and 773 K) through silver (Ag) nano-inclusions (0, 2, 5, 10, 15 and 20 wt %). Transmission electron microscopy (TEM) images of Ag incorporated in Bi2Te3 annealed at 573 K shows tubular, pentagonal, trigonal, circular and hexagonal nano-particles with sizes of 6-25 nm (for 5 wt % Ag ) and 7-30 nm (for 20 wt % Ag). Ag incorporated in Bi2Te3 annealed at 773 K shows mainly hexagonally shaped structures with particle sizes of 2-20 nm and 40-80 nm (for 5 wt % Ag) and 10-60 nm (for 20 wt % Ag). Interestingly, the samples annealed at 573 K show the highest Seebeck coefficient (S, also called thermopower) at room temperature (p-type behavior) for 5% Ag which is increased ca. five-fold in comparison to Ag-free Bi2Te3, whereas for samples with the same content (5% Ag) annealed at 773 K the increment in thermopower is only about three-fold with a 6.9-fold enhancement of the power factor (S-2 sigma). The effect of size and shape of the nanoparticles on thermoelectric properties can be understood on the basis of a carrier-filtering effect that results in an increase in thermopower along with a control over the reduction in electrical conductivity to maintain a high power factor yielding a high figure of merit
Measurement of Static and Dynamic Magneto-Viscoelasticity in Facile Varying pH Synthesized CoFe2O4-Based Magnetic Fluid
Get PDFIn this work, we have investigated the size induced on the viscoelasticity of CoFe2O4 magnetic nanofluids (MNFs). The focus of this work is to provide an insight into the effect of varying particle size on viscoelastic properties of CoFe2O4 MNFs with varying CoFe2O4 nanoparticle sizes. Kerosene-based MNFs containing surfactant coated CoFe2O4 were synthesized using standard optimized coprecipitation method, and variations in average mean size similar to 9-30 nm have been synthesized. The physical properties, such as structural and morphology, have been investigated to confirm the purity, and variation in size. Steady-state and oscillatory mode measurements were performed using a magneto-rheometer to investigate the field-induced magneto-rheology. The steady-state rheograms (viscosity vs. shear rate curve) has been well fitted with power-law eta = c(gamma)over dot(n) + eta(infinity), confirming the shear thinning behavior with n <= 1. Furthermore, magneto-sweep rheograms (viscosity vs. magnetic field) has been used to investigate the steady increase in viscosity, which is due to the formation of a chain-like structure in the field direction causing an interruption in the smooth streamline flow of the MNFs. Furthermore, dynamic oscillatory measurement shows the transition between G' and G '' with applied dynamic strain confirming solid-liquid phase transition behavior. Field-induced viscoelastic behavior in static and dynamic mode provides significant information for optimization of MNFs for various applications
Non-invasive oral cancer detection from saliva using zinc oxide-reduced graphene oxide nanocomposite based bioelectrode
Get PDFMultifunctional materials with excellent biocompatibility and electron-transport properties are critical for the pursuit of point-of-care biosensing devices. The authors report the synthesis of zinc oxide-reduced graphene oxide (ZnO-rGO) nanocomposite for the fabrication of an electrochemical immunosensing test-bed for noninvasive onsite detection of oral cancer biomarker (interleukin-8, IL8). The immunosensor showed successful detection of IL8 at low concentration ranges, i.e., 100 fg/mL-5 ng/mL with a sensitivity of 12.46 +/- 0.82 mu A mL/ng and a detection limit of 51.53 +/- 0.43 pg/mL. These results have been validated through in vitro investigations using real saliva samples spiked with IL8
Long-term fertilisation impact on temperature sensitivity of aggregate associated soil organic carbon in a sub-tropical inceptisol
No full textUnderstanding impact of long-term fertilisation on soil aggregation, carbon (C) stabilisation and temperature sensitivity of soil organic C (SOC) mineralisation are necessary to foresee C dynamics. The present study was conducted in an Inceptisol under wheat (Triticum aestivum) based cropping system, with the objective to quantify the effect of 44 years of integrated nutrient management on soil aggregation, enzymatic activity, and temperature sensitivity (Q(10)) of SOC. Treatments were: unfertilised control (UC), 100% recommended dose of nitrogen (N), N and phosphorus (NP), N, P and potassium (NPK), integrated application of NPK and farmyard manure (FYM) (NPKF) and 150% recommended dose of N, P and K (1.5NPK). The observed data were analysed using analysis of variance for randomized block design and Tukey's HSD test (P < 0.05) was used for mean separation. In the 0-15 cm soil layer, plots under NPKF had (similar to)121 and 19% larger macroaggregate-associated C than UC and NPK plots, respectively. Irrespective of soil depth and temperature, higher cumulative C mineralisation was observed for NPKF (by (similar to)67-91%) and NPK (by (similar to)42-56%) treated plots than UC. Activation energies for SOC decomposition in 0-15 cm bulk soil were (similar to)205, and 258% higher in NPKF, and 1.5NPK, respectively, than UC plots. Mean Q(10) of macroaggregate-C was higher than microaggregate-C. Aggregate-C of sub-surface soil was more temperature sensitive than surface soil, possibly due to higher recalcitrant/total SOC in the subsurface than surface layer. Thus, it reveals the need of better C management practices to augment the lability of C in subsurface soil layers. Plots under NPKF had higher beta-glucosidase and fluorescein diacetate activities in bulk soils and aggregates over NPK in the both layers. NPKF application is recommended for improved soil aggregation, SOC protection within macroaggregates, enzyme activities in bulk soils and aggregates and capable for less proportional SOC decomposition than NPK or UC plots at higher temperature. Thus, soil management involving organic manure application and mineral fertilisers would enhance the activation energy of SOC and act as a barrier for SOC decomposition by facilitating soil aggregation and enhance SOC sequestration
Dielectric, magnetic and magneto-dielectric properties of (La, Co) co-doped BiFeO3
No full textBLFCO [Bi1-xLaxFe1-xCoxO3(x = 0.00, 0.01, 0.03, 0.05, 0.10)] ceramics were synthesized using sol-gel technique. The effect of Lanthanum (La) and Cobalt (Co) co-doping in BiFeO3 (BFO) on structural, electrical, magnetic and magneto-dielectric (MD) properties are systematically investigated. The phase purity and crystal structures were studied using x-ray diffraction technique. The dielectric properties [dielectric constant (epsilon) and tangent loss (tan delta)] were studied as a function of frequency and temperature for pure and co-doped BFO samples. The magnetization study reveals that the ferromagnetic (FM) properties in La and Co co-doped samples enhance with an increasing dopant concentration. The coercive field is found to increase with the doping concentration suggest a competition between the antiferromagnetic and FM ordering. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements of these samples also confirm the change in the magnetic behaviour of BLFCO as doping concentration increases. ZFC and FC magnetization curves split at low temperature with sharp cusps suggest a spin-glass like behaviour of BLFCO. The pure and co-doped samples exhibit a MD coupling effect. Furthermore, the anomaly near the magnetic phase transition (around the Neel temperature of BFO) implies the MD coupling in BLFCO samples