Formaldehyde vapour sensing property of electrospun NiO nanograins

Beads free polyvinyl alcohol (PVA)/NiO nanofibers with an average diameter of 400 nm were successfully prepared through the electrospinning method. NiO nanograins were formed along the axis of the nanofiber due to the calcination of as-spun fibers for 24 h at 450 °C and their presence was confirmed by FESEM. NiO nanograins were characterized by XRD, XPS and FTIR. The characterization results showed the presence of NiO in nanograins and its polycrystalline nature with ionic states. The sensing studies of NiO nanograins were performed towards the pulmonary disease breath markers and they showed better response towards formaldehyde vapour at 350 °C. Calcined NiO grains showed a good response towards the 11–1145 ppm of formaldehyde vapour at the operating temperature of 350 °C. NiO nanograins also showed quick response time (37 s) and recovery time (14 s) towards 46 ppm of formaldehyde. A sensing mechanism was proposed for the formaldehyde vapour interaction at 350 °C with NiO nanograins.     

Genetic algorithms in the design and optimization of antenna arraypatterns

This paper demonstrates the application of genetic algorithms (GAs) in array pattern synthesis. GAs have the ability to escape from local minima and maxima and are ideally suited for problems where the number of variables is very high. We present three examples: two for linear arrays and one involving linear and planar arrays     

Rigorous analysis of weakly excited broadwall slots

The choice of basis functions is found to be critical in the accurate modelling of weakly excited slots. Pulse expansions and the point matching technique are found to be inadequate, whereas polynomial basis functions in the Galerkin method are found to yield very accurate solutions     

Impact of Tuning Molar Ratio in the Starting Materials: <Emphasis Type="Italic">Magneto</Emphasis>-Transport Features of Hybrid YSr<Subscript>2</Subscript>Ru<Subscript>0.9</Subscript>Cu<Subscript>2.1</Subscript>O<Subscript>7.9</Subscript>

The impact of slightly tuning molar ratio in the starting materials on the physical properties of 1212-type rutheno-cuprate, YSr₂Ru_0.9Cu_2.1O_7.9 (nominal) samples prepared under four synthesis approaches are reported. Interestingly, all samples clearly show the differences in the physical properties of the samples prepared under different synthetic protocols. However, neither XRD nor EDX reveal any notable differences in the crystal structure or sample composition. All the samples exhibit magneto-superconducting properties (H _ext=5 Oe) which are slightly varied with synthetic approaches. The high field (H _ext=10 kOe) temperature dependence of magnetization data shows a sharp ferromagnetic transition around 150 K and all the samples obey Curie–Weiss linear behavior above 180 K. The experimental effective paramagnetic moment for the various samples is in the range of 2.5 and 2.7μ _B/Ru which are in line with the literature report. The magnetization, M(H) isotherm curves measured at 5 K and −10 kOe≤H≤10 kOe conditions reveal weak ferromagnetic-like hysteresis loops for all samples with returning moment (M _r) and coercive field (H _c), whereas the high field M(H) loops indicate soft ferromagnetic behaviors with magnetic saturation. The saturation moment of the samples is slightly varied with the synthesis approaches. None of the samples showed bulk superconductivity (T_c^{R = 0})T_{\mathrm{c}}^{R = 0}) down to 2 K, while all samples show onset transitions (T_c^onsetT_{\mathrm{c}}^{\mathrm{onset}}) except the sample prepared by approach-3. The latter approach sample shows semiconducting behavior down to 2 K. The T_c^onsetT_{\mathrm{c}}^{\mathrm{onset}} noticed at 34 K, 12 K, and 6 K for the sample prepared by approach-1, 2, and 4, respectively. The nearly linear dependence suggests that hopping conduction is dominant in certain temperature range for all samples. The magneto-transport features of these samples exhibit maximum magnetoresistance (MR) at low temperatures. Remarkably, the sample prepared by approach-1 shows largest −MR about 77% at low temperature 2 K and H=90 kOe which stimulates for further investigations. Among the four synthesis approaches employed in the present study, we can probably suggest that the approach-1 (0.5Y₂O₃+0.5SrO₂+1.5SrCuO₂+0.9RuO₂+0.6CuO) is the preferable method to achieve the best sample (in terms of magneto-transport features).     

Double layer CuInS2 absorber using spray pyrolysis: A better candidate for CuInS2/In2S3 thin film solar cells

In the fabrication of CuInS₂/In₂S₃ solar cell using chemical spray pyrolysis (CSP) deposition technique, one of the major problems is the diffusion of Cu towards the In₂S₃ layer affecting stability and repeatability of the CuInS₂/In₂S₃ cells. In order to ensure a Cu-free In₂S₃ layer, a ‘double layer structure’ of CuInS₂ film, having a Cu-rich first layer and In-rich second layer was deposited using manual CSP technique. In this paper, we present the difference in material properties of single and double layered CuInS₂ films and the results of characterisation of the junctions prepared using such films with β-In₂S₃ films. Better crystallinity as well as larger and densely packed grains were observed for the CuInS₂ films having ‘double layer structure’. Such samples also possessed two band gaps, which was not due to the presence of different phases, but due to the Cu-rich and Cu-poor layers. In addition, their low resistivity makes the double layered CuInS₂ film more beneficial for photovoltaic applications.     

Development and performance evaluation of Proton Exchange Membrane (PEM) based hydrogen generator for portable applications

This paper presents the development of key components, specifications, configuration and operation characteristics of an 80 l/h Proton Exchange Membrane (PEM) water electrolyzer system for portable application. The developed PEM water electrolyzer can produce 80 l/h hydrogen (purity > 99.99%) with moderate pressure range up to 500 kPa (73 psi) at an operating current of 100 A with energy efficiency of 77.48%. The reliability in operation of developed PEM water electrolyzer system is tested for running the stack about 3000 h with 100 A current. The results indicate the reasonable stability of MEA fabrication and cell design method.     

Operational planning of an engine generator using a high pressure working fluid composed of CO2 hydrate

An actuator system (gas-hydrate engine) using the dissociation and recombined continuous cycle of CO₂ gas hydrate was developed. The heat source temperatures required for the operation of the proposed system are in the temperature range of green energy and low-quality exhaust heat. The energy flow of this proposed system was investigated by numerical analysis. From these results, for example, the entrance operating conditions of the recombination equipment are 9 °C and 1.2 MPa, and the exit conditions are 0 °C and 5 MPa. In the case of a heat source temperature of 20 °C of the recombination equipment, a heat source temperature of −5 °C of the dissociation equipment and the passing of a working fluid comprised of 1150 g/s of CO₂ and H₂O about 5 kW of electric power can be obtained. Moreover, although the recombined speed was remarkably slow compared with dissociation, this study considered the relation of recombined speed between the physical conditions of the working fluid and the volume of the recombination equipment. Based on the results obtained in this study, a prototype will be developed next.