Morphology,Mineralogy and Mixing of Individual Atmospheric Particles Over Kanpur (IGP): Relevance of Homogeneous Equivalent Sphere Approximation in Radiative Models

Estimation of the direct radiative forcing (DRF) by atmospheric particles is uncertain to a large extent owing to uncertainties in their morphology (shape and size), mixing states, and chemical composition. A region-specific database of the aforementioned physico-chemical properties (at individual particle level) is necessary to improve numerically-estimated optical and radiative properties. Till date, there is no detailed observation of the above mentioned properties over Kanpur in the Indo-Gangetic Plain (IGP). To fill this gap, an experiment was carried out at Kanpur (IITK; 26.52°N, 80.23°E, 142 m msl), India from April to July, 2011. Particle types broadly classified as (a) Cu-rich particles mixed with carbon and sulphur (b) dust and clays mixed with carbonaceous species (c) Fe-rich particles mixed with carbon and sulfur and (d) calcite (CaCO₃) particles aged with nitrate, were observed. The frequency distributions of aspect ratio (AR; indicator of extent of particle non-sphericity) of total 708 particles from April to June reveal that particles with aspect ratio range >1.2 to ≤1.4 were abundant throughout the experiment except during June when it was found to shift to high AR range, >1.4 to ≤1.6 (followed with another peak of AR i.e. >2 to ≤2.4) due to dust storm conditions enhancing the occurrence of more non-spherical particles over the sampling site. The spherical particles (and close to spherical shape; AR range, 1.0 to ≤1.2) were found to be <20% throughout the experiment with a minimum (11.5%) during June. Consideration of Homogeneous Equivalent Sphere Approximation (HESA) in the optical/radiative model over the study region is found to be irrelevant during the campaign.     

Influence of reduced graphene oxide on structural,optical, thermal and dielectric properties of SnO2 nanoparticles

The present work has been carried out with the aim to synthesize tin oxide decorated reduce graphene oxide nanocomposite (SnO₂/RGO-Nc) via in-situ synthesis process and the influence of RGO loading on structural, optical, thermal and dielectric properties of SnO₂ has been discussed. The XRD, FESEM coupled with EDX elemental mapping, TEM, FTIR, Raman and XPS results reveal that the SnO₂ nanoparticles have been successfully incorporated onto the RGO sheets. The reduction in the energy gap of the composite sample as compared to SnO₂ measured from the Tauc’s relation can be attributed to strong coupling between RGO and SnO₂ NPs. Thermogravimetric analysis (TGA) shows improved thermal stability of the SnO₂/RGO-Nc. From the dielectric measurements, it is observed that the dielectric constant and dielectric loss decreases as frequency of applied field increases. AC conductivity of all samples increases as applied frequency increases which follows Jonscher’s power law. All composite samples show better conductivity as compared to SnO₂. This is due to the formation of continuous conductive pathway between SnO₂ and RGO sheets. Further high dielectric constant, low loss and high ac conductivity have been observed at optimum loading of RGO in SnO₂/RGO2-Nc as compared to other composite samples which is due the percolation effects. The impedance analysis exhibits only one semicircle for SnO₂ and SnO₂/RGO composite which suggests that the involvement of grain boundaries dominated over the grain contribution.     

Intradomain QoS routing in IP networks: a feasibility andcost/benefit analysis

Constraint-based routing gradually becomes an essential enabling mechanism for a variety of emerging network services such as virtual private networking and QoS support. A number of previous works have recognized its significance and investigated many aspects of the operation of constraint-based routing and in particular its variant concerned with determining paths for requests with specific QoS requirements, known as QoS routing. In this work we build on previous results on the cost of QoS routing and investigate the performance/cost trade-offs involved in the operation of a representative QoS routing architecture, elaborate on the constituents of this cost, and identify the main methods for containing the cost that QoS routing incurs on routers. Our results show that the cost of QoS routing is not excessive and that there indeed exist operational configurations, which can achieve reasonable performance gains with only a minimal increase in processing cost when compared to conventional best-effort routing     

Systematic generation of OTA-C sinusoidal oscillators

The authors outline a method for generating all possible, canonic, linearly tunable, OTA-C sinusoidal oscillators systematically.<>     

Surface modification of semiconductor photoelectrode for improved solar cell performance

The investigation is focused on the synthesis of nanostructured TiO₂–CuO admixed photoelectrode and its use as a photoelectrode of high-efficiency PEC solar cells for hydrogen production. TiO₂, in the nanostructured form, has been prepared by hydrolysis of titanium(IV) isopropoxide solution. An improvement in the nanostructured TiO₂ photoelectrode carried out in the present work corresponds to admixing CuO to improve the spectral response. In the present study, photo-electrochemical (PEC) and hydrogen evolution characteristics of new types of ns-TiO₂–CuO admixed/Ti septum-based semiconductor septum photo-electrochemical (SC-SEP PEC) solar cell has been studied. The CuO admixed ns-TiO₂ exhibited a high photocurrent and photovoltage of 18.6 mA/cm² and 680 mV, respectively. The ns-TiO₂–CuO electrode exhibited a higher hydrogen gas evolution rate of 14.00 l/h m².     

Negative differential resistance in a resonant quantum wirestructure

It is shown that the transmission characteristics of a semiconductor split-gate device with a double constriction exhibit resonant behavior similar to that in resonant-tunneling diodes (RTDs). The double constriction is modeled with cascaded quantum waveguides of different widths and analyzed by applying a mode-matching technique to the wave function at the discontinuities. At low temperature, the calculated current-voltage characteristics exhibit a region of negative differential resistance. Current-voltage characteristics are presented for different constriction widths and temperatures exhibiting peak-to-valley ratios of up to 4:1 which persist up to temperatures around 10 K     

The mode features of an annular sector microstrip antenna

A rigorous analysis of the features of the modes of an annular sector printed microstrip antenna is presented. General expressions for its radiation field are derived by using the cavity model. The expressions are used to study the radiation patterns, radiation peak in the broadside direction, and beamwidth of different structures for various sector angles, widths, and modes of excitation. This includes the special cases of quarter-, half-, three-quarters-, and ideal-gap open-ring structures. Compared to a closed ring, the results indicate that the TM₁₂ mode is superior to the TM₁₁ mode with regard to the radiation properties in the annular sector as its angle approaches 2π