Comparison of total ozone column observations from space-borne Ozone Monitoring Instrument with ground-based Dobson Ozone Spectrophotometer measurements at an urban location in Indo-Gangetic Basin

This article presents a comparison analysis of OMIT (Ozone Monitoring Instrument retrieved overpass total ozone column (TOC)), and DOST (Dobson Ozone Spectrophotometer observed TOC) over Delhi during a period from October 2004 to June 2011. Megacity Delhi, located in Indo-Gangetic Basin, is an important site for comparison of ground-based and satellite retrieved TOCs due to significant anthropogenic emissions of ozone precursors, large shift in seasons, and large-scale crop residue burning in the region. DOST and OMIT data show an overall bias of 3.07% and significant correlation with coefficient of determination R² = 0.73. Large seasonal fluctuations in the biases and correlations have been observed ranging from 2.46% (winter) to 3.82% (spring), and R² = 0.84 (winter) to R² = 0.09 (summer), respectively. The large biases are attributed to changes in temperature, cloud cover, pollutants emissions from urban area, and crop-residue burning events. We also find notable variations in correlations between the datasets due to the varying burden of absorbing aerosols from open field crop-residue burning. The R² has changed from 0.67 (for aerosol optical depth, AOD 1.5–3.5) to 0.77 (for AOD 0–0.99). The dependence of the bias on solar zenith angle, cloud fraction, and satellite distance is also discussed. A simple linear regression analysis is applied to check the linkage between DOST and OMIT. The influence of atmospheric air temperature and relative humidity on OMIT at different pressure levels between 1000 and 20 hPa has been discussed.     

Controlling the material removal and roughness of Inconel 718 in laser machining

Nickel alloys including Inconel 718 are considered as challenging materials for machining. Laser beam machining could be a promising choice to deal with such materials for simple to complex machining features. The machining accuracy is mainly dependent on the rate of material removal per laser scan. Because of the involvement of many laser parameters and complexity of the machining mechanism it is not always simple to achieve machining with desired accuracy. Actual machining depth extremely varies from very low to aggressively high values with reference to the designed depth. Thus, a research is needed to be carried out to control the process parameters to get actual material removal rate (MRR_act) equals to the theoretical material removal rate (MRR_th) with minimum surface roughness (SR) of the machined surfaces. In this study, five important laser parameters have been used to investigate their effects on MRR and SR. Statistical analysis are performed to identify the significant parameters with their strength of effects. Mathematical models have been developed and validated to predict the machining responses. Optimal set of laser parameters have also been proposed and confirmed to achieve the actual MRR close to the designed MRR (MRR_% = 100.1%) with minimum surface roughness (R_a = 2.67 µm).     

Comparative photocatalytic performance and therapeutic applications of zinc oxide (ZnO) and neodymium-doped zinc oxide (Nd–ZnO) nanocatalysts against Acid Yellow-3 dye: kinetic and thermodynamic study of the reaction and effect of various parameters

Zinc oxide (ZnO) nanoparticles (NPs) were synthesized hydrothermally and doped with 4% Neodymium (Nd). The produced NPs were characterized using UV–Vis spectroscopy, X-ray diffraction (XRD), Energy dispersive X-ray analysis, Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Photoluminescence (PL) spectroscopy. With the addition of 4% Nd, the bandgap reduced from 3.20 to 3.00 eV which confirmed successful doping with Nd which also evident from FTIR study. The XRD study showed hexagonal structure of the synthesized material, while SEM study confirmed that Nd-doped ZnO (Nd–ZnO) NPs are well dispersed as compare to ZnO. TGA study revealed that synthesized NPs were much stable to temperature and only 11.3% and 7.2% the total loss occurred during heating range (40–600 °C) in case of ZnO and Nd–ZnO NPs, respectively. The PL intensity of the visible peaks of ZnO reduced after doping with Nd. The degradation of Acid yellow-3 over both the catalysts followed first-order kinetics. The activation energy calculated for the photodegradation reaction was 43.8 and 33.7 kJ/mol using pure ZnO and Nd–ZnO NPs, respectively. About 91% and 80% dye was degraded at the time interval of 160 min using Nd–ZnO and ZnO NPs, respectively. High percent degradation of dye was found at low concentration (10 ppm) and at optimal dosage (0.035 g) of the catalyst. The rate of Acid yellow-3 dye degradation was found to increase with increase in temperature (up to 50 °C) and pH(8) of the medium. The recyclability study showed that both pure ZnO and Nd–ZnO NPs could be reused for the degradation of the given dye. With the addition of H₂O₂ up to 5 µL, the rate of reaction increased clearly indicating the effect of OH^· generation during photocatalysis. When compared with Nd–ZnO NPs at low concentrations, ZnO NPs at higher concentrations were found to be less hazardous. Both the NPs showed best antibacterial activities against Staphylococcus aureus. The hemolytic study indicated that at low concentration, pure ZnO was non-hemolytic as compared to Nd–ZnO.

     

Towards Ensuring Reliability of Vehicular Ad Hoc Networks Using a Relay Selection Techniques and D2D Communications in 5G Networks

Wireless Personal Communications - Benefiting from unlimited power supply, vehicular ad hoc networks (VANETs), in a 5G platform, can deal superiorly with the challenges of providing high...     

Mechanical properties of bovine hydroxyapatite (BHA) composites doped with SiO<Subscript>2</Subscript>, MgO,Al<Subscript>2</Subscript>O<Subscript>3</Subscript>, and ZrO<Subscript>2</Subscript>

Biologically derived hydroxyapatite from calcinated (at 850 °C) bovine bones (BHA) was doped with 5 wt% and 10 wt% of SiO₂, MgO, Al₂O₃ and ZrO₂ (stabilized with 8% Y₂O₃). The aim was to improve the sintering ability and the mechanical properties (compression strength and hardness) of the resultant BHA-composites. Cylindrical samples were sintered at several temperatures between 1,000 and 1,300 °C for 4 h in air. The experimental results showed that sintering generally occurs at 1,200 °C. The BHA–MgO composites showed the best sintering performance. In the BHA–SiO₂ composites, extended formation of glassy phase occurred at 1,300 °C, resulting in structural degradation of the resultant samples. No sound reinforcement was achieved in the case of doping with Al₂O₃ and zirconia probably due to the big gap between the optimum sintering temperatures of BHA and these two oxides.     

Selective wakeup for parallel forward engines under variable load towards energy conservation in IP routers

Recent studies have shown that a large amount of energy consumption in the communication medium occurs at the data processing plane. The data plane executes the forwarding decisions in the routers and switches. Through initial studies, the line card was identified as the most granular component of the router and later forward engine, a sub component of line card has been recognized as the most power intensive component of routers. Fundamental techniques like link rate adaption, sleep and wake-up have been imposed to reduce the energy at line cards and forward engines. On the other hand, router's architectures undergo drastic changes like empowering data plane with parallel processing due to the rise of gigabit routers. In this paper, to increase the degree of local autonomy and better energy savings, we have adopted the parallel processing design and imposed a variable amount of traffic on different line cards. The existing parallel forward engines perform load balancing in synchronous manner. In our design, asynchronous behavior is imposed such that every line card could independently decide to wake up or turn off their forward engine based on the traffic parameters. We have done simulations and witnessed increased energy savings (average sleeping time) without compromising the completion of lookup process.     

Insight into the binding of copper(II) by non-toxic biodegradable material (Oryza sativa): effect of modification and interfering ions

The present studies are focused on the use of non-toxic biodegradable straw from Oryza sativa in its simple and modified forms for the binding of copper(II) ions. A relatively new “green” method was adopted for modification with urea under microwaves. The studies have been performed by using the aqueous solution of Cu(II) ions with and without the presence of Cd(II) and Pb(II) as interfering ions. FTIR analysis showed the presence of oxygen- and nitrogen-containing functional groups in simple and modified materials. The emergence of new bands and shifts in the peaks confirmed the modification. The kinetics of the process was studied using the commonly employed mathematical models. Although Elovich model seemed to fit yet coefficient of determination did not reinforce it. Pseudo-second-order model was found to explain the kinetics of the binding of metal ions by simple and modified straw. The equilibrium was studied using the non-linear approach. Based on root mean square error values, it was found that Langmuir model was the most suitable model, followed by Temkin model. Surface areas were compared for single and multi-metal systems. The effect of pH was also studied. Under the studied set of conditions, the modification of straw caused a decrease in the equilibrium time of contact and increase in the biosorption capacities. The presence of other ions decreased the capacities drastically due the competition to bind with the materials.     

Generative regular-freeform surface recognition for generating material removal volume from stock model

The present paper illustrates the development of generative surface recognition for regular and freeform. To obtain the final form of product, material removal volume generation from a stock model is also discussed. Only a few studies integrated the regular and freeform surfaces to provide a comprehensive definition of surface recognition as well as for the volumetric estimation of removal material in finishing and roughing operations. The current research deploys a comprehensive surface recognition approach that can recognise both regular and freeform surfaces based on the geometry as well as loop entity of a face. In contrast to the regular surface that can be categorised into a particular group of geometrical shape, such as cylindrical shape, the proposed approach enables the recognition of a freeform surface that cannot be defined as a generic geometrical shape. In addition, the new method also simplifies the existing surface recognition for regular surfaces. The material removal volumes created consist of machining volumes for finishing and roughing operations needed to be machined to obtain the final form of the product. The present research provides a unique user customisation feature that enables user to specify the volumetric thickness for material removal volume in the finishing operation as well as the size for the stock model. These estimated volumes are prepared for subsequent manufacturing applications, such as sequencing of machining operation.     

Fabrication of circular microfluidic channels through grayscale dual-projection lithography

Circular microfluidic channels are in great demand since they are more realistic in mimicking physiological flow systems, generating axis-symmetrical flow, and achieving uniform shear stress. A typical microchannel with rectangular cross section can induce non-physiological gradients of shear rate, pressure, and velocity. This paper presents a novel method of fabricating microfluidic channels with circular and elliptical cross sections through grayscale dual-projection lithography. Our method utilizes two projecting systems to expose grayscale image face-to-face and simultaneously polymerize the photocurable material. The cross-sectional profiles of the fabricated microchannels are consistent with mathematical predictions and, therefore, demonstrate the capability of controlling the channel shapes precisely. Customized circular microchannels can be generated with complex features such as junctions, bifurcations, hierarchies, and gradually changed diameters. This method is capable of fabricating circular channels with a wide range of diameters (39 μm–2 mm) as well as elliptical channels with a major-to-minor axis ratio up to 600%. Microfluidic devices with circular cross sections suitable for particle analysis were made as a demonstrative application in nanoparticle binding and distribution within a mimetic blood vessel. A ready-to-use microfluidic device with customized circular channels can be fabricated within 1 h without the need of clean room or expensive photolithography devices.     

Buckypapers of polyvinyl chloride/poly(styrene-co-maleic anhydride) blend intercalated graphene oxide-carbon nanotube nanobifiller: Physical property exploration

Novel buckypaper of polyvinyl chloride (PVC) and poly(styrene-co-maleic anhydride) (PSMA) intercalated with carbon nanotube (CNT) and graphene oxide-CNT (GO-CNT) nanobifiller was prepared using resin infiltration technique. Two series of buckypaper were prepared with varying CNT and GO-CNT contents. According to field emission scanning electron microscopy, PVC/SMA/CNT 0.1 showed porous morphology while PVC/PSMA/GO-CNT 0.1 revealed unique sort of island-nodule morphology. T_max of PVC/PSMA/GO-CNT 0.1 was 561°C while PVC/PSMA/CNT 0.1 depicted relatively lower value (552°C). T_g of PVC/PSMA/GO-CNT 0.1 was also increased to 294°C. Peak heat release rate of poly(methyl methacrylate-co-methacrylic acid)/polyamide 6/montmorillonite-modified GO was decreased from 322 to 209 kW/m² (65%) with 0.03–0.3 g GO-CNT loading.