Compact frequency reconfigurable triple band notched monopole antenna for ultrawideband applications

A compact ultra‐wideband (UWB) reconfigurable microstrip fed monopole antenna having size of 0.22 λ₀ × 0.28 λ₀ × 0.005 λ₀ with switchable frequency bands is presented. Triple band notched characteristics are achieved by inserting two stubs at top of radiator and one slot in between the radiator and microstrip feed line. Proposed antenna achieves reconfigurability with three PIN diodes at strategic positions to obtain eight different operational modes. In one of the operational modes, antenna operates in the entire UWB (3‐14 GHz) with fractional bandwidth of 127.5%. Two stubs are used to notch two frequency bands worldwide interoperability for microwave access (3.3‐3.6 GHz/WiMAX) and C‐band (3.7‐4.2 GHz). T‐shaped slot is also inserted to notch wireless local area network (5.725‐5.825 GHz/WLAN) frequency band. Proper biasing of PIN diodes is done by using suitable chip inductors and capacitors. Proposed antenna exhibits stable radiation patterns with average gain of around 3 dBi. Simulation and measurement results are in good agreement. Proposed antenna is suitable for on‐demand band rejection of parasitic bands coexisting in UWB.     

Electrochemical investigations of cobalt-free perovskite cathode material for intermediate temperature solid oxide fuel cell

A novel cobalt-free perovskite zinc-doped lanthanum strontium iron oxide (La_0.8Sr_0.2Zn_xFe_1?xO_3?δ, LSZF, x = 0.1–0.3) is synthesized and evaluated as cathode material for intermediate temperature solid oxide fuel cell (IT-SOFC) with samarium doped ceria (SDC) electrolyte. LSZF cathode at x = 0.2 composition demonstrates the remarkable electrochemical activity at intermediate temperature (550 °C): such as, high electrical conductivity (13.63 S cm^?1), excellent thermal stability with SDC electrolyte (12.10 μK^?1), high surface area (4.52 m² g^?1), extremely reduced area specific resistance (0.69 Ω cm^?2) and low activation energy (0.117 eV). Furthermore, single fuel cells are fabricated using LSZF as a cathode, which exhibits the excellent performance by achieving the high power density of 409 mW cm^?2 under natural gas as a fuel and ambient air as an oxidant at 550 °C with good stability over 10 h. All experimental results indicate that the LSZF is a promising cathode material for natural gas based intermediate temperature fuel cell applications.     

Electrochemical evaluation of mixed ionic electronic perovskite cathode LaNi1-xCoxO3-δ for IT-SOFC synthesized by high temperature decomposition

The cobalt doped perovskite cathode material LaNi_1-xCo_xO_3-δ (x = 0.4, 0.6, 0.8) synthesized by cost effective high temperature decomposition is investigated as mixed ionic electronic conductor (MIEC) for intermediate temperature solid oxide fuel cell (IT-SOFC). LaNiO₃ is known for its high electronic conductivity and to introduce more oxygen vacancies for enhancing its ionic conductivity, Ni at B site is substituted by Co. XRD analysis showed perovskite structure for all samples with no additional phases, which was also confirmed by FTIR results. Microstructure analysis revealed well connected and porous structure for LaNi_1-xCo_xO_3-δ (x = 0.6) compared to other compositions. The elemental analysis using EDX confirmed presence of lanthanum, nickel, and cobalt within all samples. No prominent weight loss was observed during TGA analysis. The highest value of conductivity was obtained for LaNi_1-xCo_xO_3-δ (x = 0.6) due to its porous and networked structure of sub micrometric grains. The superior performance is attained for the cell based on LaNi_1-xCo_xO_3-δ (x = 0.6) cathode with maximum power density of 0.45 Wcm^?2 compared to other composition which can be attributed to its well connected and porous structure that caused enhanced electrochemical reaction at triple phase boundary (TPB). It was therefore deduced that LaNi_1-xCo_xO_3-δ (x = 0.6) is promising composition to be used as MIEC cathode for IT-SOFC.     

Photovoltaic performance and impedance spectroscopy of ZnS-Cu-Go nanocomposites

In this work, novel, non-toxic and cost effective ZnS-Cu-GO nanocomposite is synthesized via wet chemical route to study its photovoltaic properties. Three samples including ZnS,ZnS-Cu and ZnS-Cu-GO were prepared and deposited as sensitizers on ZnO coated FTO substrates to assemble PV devices.The samples were characterized using UV–Vis NIR spectroscopy, Atomic force microscopy (AFM).Electrochemical impedance spectroscopy (EIS) and AM 1.5 Sun Simulator. It was observed that ZnS-Cu-GO exhibitedsuperiorchargetransport, remarkably high open circuit voltage(0.8 V) and Fill factor (0.806).The current density significantly enhanced and maximum solar cell efficiency was observed for ZnS-Cu-GO based PV device. A pronounced red shift of 360 nm in the absorption spectra was observed in the ZnS-Cu-GO due to fine dispersion of GO sheets.The AFM analysis showed that incorporation of GO and Cu maximized grain density and trench like grain boundaries in ZnS-Cu-GO which facilitated charge transport mechanism.A detailed electrochemical impedance study to probe charge dynamics in the prepared PV devices is presented herein.     

Synthesis of highly pure single crystalline SnSe nanostructures by thermal evaporation and condensation route

Here we report the synthesis of highly pure single crystalline tin selenide (SnSe) nanospheres by pretreatment of precursors with aqueous ammonia. In this work we have demonstrated that aqueous ammonia not only controls the preferred growth orientation but also controls the morphology of SnSe. Chemical vapor deposition technique was used for the growth of SnSe nanostructures. The optical properties were studied using UV–vis–NIR spectroscopy and Photoluminescence (PL) spectrum.     

Physicochemical properties of acetylated starches from some Indian kidney bean (Phaseolus vulgaris L.) cultivars

Starches separated from four kidney bean cultivars were modified by acetylation to reduce retrogradation and increase gel stability and compared with respective native starches (data of native starch reported by Wani et al., 2010 ). Acetylation was carried out by treating starches with 0.04 and 0.08 g of acetic anhydride per gram of starch dry weight basis (dwb) at 25 °C and pH between 8.0 and 8.5. The extent of acetylation increased proportionally with the concentration of acetic anhydride used. The pasting curves of 10.7% starch determined by Rapid Visco Analyzer at 160 rpm showed that acetylation decreased the setback viscosity values by 0.64–34.58% and pasting temperature by 4.4–9.2 °C when compared with the native starch. Differential scanning calorimetry observations also revealed significant (P ≤ 0.05) decrease in gelatinisation temperature of acetylated starches than the corresponding native starches. Hardness of starch gels varied between 14.3 and 44.0 g, which was significantly (P ≤ 0.05) lower than the corresponding native starch gels.     

Physical and cooking characteristics of black gram (Phaseolus mungoo L.) cultivars grown in India

Pulses are important component of diet, and information on their physical properties is needed for designing machines while cooking quality is important for consumer acceptance. Three black gram cultivars grown in India were evaluated for physical and cooking properties. Proximate composition revealed that three cultivars contained 24.5–26.7% protein, 1.1–1.3% fat, 2.8–3.7% ash and 60.4–63.3% carbohydrates. Length, breadth and thickness of seeds were in the range of 4.66–5.11 mm, 3.71–3.79 mm and 3.20–3.29 mm, respectively. True density and porosity varied from 1.25–1.29 g mL^?1 to 33.43–36.09%, respectively. Hydration and swelling capacities of the seeds varied from 0.036–0.041 g per seed to 0.037–0.042 mL per seed, respectively. Cooking time of unsoaked seeds varied significantly from 35.3 to 42.7 min. Hardness and adhesiveness of the cooked seeds varied from 2.12–2.55 kg to 0.02–0.99 kg s, respectively. The black gram cultivars are rich in protein, and soaking treatment improved their cooking quality.     

Modelling of multicomponent salt systems: Application to sea water and brines I. Derivation of the model

The solubility of a salt in saturated solution is described in terms of heterogeneous reaction between solid and liquid and an equation of the solubility field is established for each solid phase (limiting or intermediate phase) of a multicomponent aqueous salt system.

The model supposes that solid phases are stoichiometric and that the solution is a strong electrolyte. It includes all sub-systems and the procedure used for the calculation of coefficients is described.

The equations allow the critical evaluation of solubility data, the calculation of phase diagrams and the determination of equilibrium (proportion and nature of phases) under any conditions of temperature and composition.

The application to the sub-systems involved in sea water and natural brines will be developed in forthcoming publications.