Synthesis of nano-crystalline Zr-M (M=Ni,Co, Fe,Cu) bilayer films and their thermodynamics of hydrogen uptake by resistance measurement

Nano-crystalline thin metal films for hydride formation for small amount of hydrogen storage is an emerging field of research for portable applications e.g. thin film fuel cells. Nano-crystalline films of Zr/ M (M = Ni, Co, Fe, Cu) bilayer systems were synthesized using ion beam sputtering technique in argon atmosphere which were characterized using GIXRD and AFM techniques. In thin film metal hydride it is difficult to measure P-C-T isotherm because of the small amount of hydrogen present and the same difficulty is to study thermodynamics of such systems. Hence in the present work change in electrical resistance with hydrogen pressure in temperatures range 298 to 573 K has been used to investigate thermodynamic properties and found that resistance of film increases with the absorption of hydrogen and decreases due to hydrogen desorption.     

Sources and reactivity of NMHCs and VOCs in the atmosphere: A review

Nonmethane hydrocarbons (NMHCs) and volatile organic compounds (VOCs) are important species present in the environment, which results in alteration of the chemistry of atmosphere. On the global scale natural emissions of NMHCs and VOCs exceed anthropogenic emissions, although anthropogenic sources usually dominate within urban areas. Among the natural sources, vegetation is the dominant source. Oceanic and microbial production of these species is minimal as compared to other sources of input. Isoprene and terpenes are main species of NMHCs which are emitted from plants as a protective mechanism against temperature stress tolerance and protection from ravages of insects and pests. The major anthropogenic sources for NMHCs emissions are biomass burning and transportation. NMHCs play a significant role in ozone (O₃) production in the presence of adequate concentration of oxides of nitrogen in the atmosphere. The production of O₃ is based on Maximum Incremental Reactivity (MIR) of NMHCS and VOCs. The compound's MIR multiplied by molecular weight gives Relative Ozone Productivity (ROPi). To check the reliability of current methods of measuring the NMHCs the Nonmethane Hydrocarbon Inter-comparison Experiment (NMHICE) had been designed. The sample of known composition and unknown concentration of different hydrocarbons was supplied to different laboratories worldwide and less than 50% laboratories correctly separated the unknown mixture. Atmospheric scientists throughout the world are evaluating current analytical methods being employed and are trying to correct the problems to ensure quality control in hydrocarbon analysis.     

Dual-Layer Oxidation-Protective Plasma-Sprayed SiC-ZrB<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Carbon Nanotube Coating on Graphite

Graphite is used in high-temperature gas-cooled reactors because of its outstanding irradiation performance and corrosion resistance. To restrict its high-temperature (>873 K) oxidation, atmospheric-plasma-sprayed SiC-ZrB₂-Al₂O₃-carbon nanotube (CNT) dual-layer coating was deposited on graphite substrate in this work. The effect of each layer was isolated by processing each component of the coating via spark plasma sintering followed by isothermal kinetic studies. Based on isothermal analysis and the presence of high residual thermal stress in the oxide scale, degradation appeared to be more severe in composites reinforced with CNTs. To avoid the complexity of analysis of composites, the high-temperature activation energy for oxidation was calculated for the single-phase materials only, yielding values of 11.8, 20.5, 43.5, and 4.5 kJ/mol for graphite, SiC, ZrB₂, and CNT, respectively, with increased thermal stability for ZrB₂ and SiC. These results were then used to evaluate the oxidation rate for the composites analytically. This study has broad implications for wider use of dual-layer (SiC-ZrB₂/Al₂O₃) coatings for protecting graphite crucibles even at temperatures above 1073 K.     

Intergranular Corrosion Behavior of Low-Nickel and 304 Austenitic Stainless Steels

Intergranular corrosion (IGC) susceptibility for Cr-Mn austenitic stainless steel and 304 austenitic stainless steel (ASS) was estimated using electrochemical techniques. Optical and SEM microscopy studies were carried out to investigate the nature of IGC at 700 °C with increasing time (15, 30, 60, 180, 360, 720, 1440 min) according to ASTM standard 262 A. Quantitative analysis was performed to estimate the degree of sensitization (DOS) using double loop electrochemical potentiokinetic reactivation (DLEPR) and EIS technique. DLEPR results indicated that with the increase in thermal aging duration, DOS becomes more severe for both types of stainless steel. The DOS for Cr-Mn ASS was found to be higher (65.12% for 1440 min) than that of the AISI 304 ASS (23% for 1440 min). The higher degree of sensitization resulted in lowering of electrical charge capacitance resistance. Chronoamperometry studies were carried out at a passive potential of 0.4 V versus SCE and was observed to have a higher anodic dissolution of the passive film of Cr-Mn ASS. EDS studies show the formation of chromium carbide precipitates in the vicinity of the grain boundary. The higher Mn content was also observed for Cr-Mn ASS at the grain boundary.     

Protecting data privacy in growing neural gas

Growing neural gas is a well-known algorithm in evolutionary computing. It is very effective for training neural networks. However, if the training data for growing neural gas comes from two different parties, privacy concerns may become a hurdle for using this algorithm: Each party may not be willing to reveal her own data to the other, although she wants to collaborate with the other party in running the growing neural gas algorithm on their joint data. In this paper, we propose a privacy-preserving algorithm for growing neural gas with training data from two parties. Our algorithm allows two parties to jointly execute the growing neural gas algorithm without revealing any party’s data to the other. Our algorithm is secure in that it leaks no knowledge about any participant’s data to the other. Experiments on the real-world data show that our algorithm is very efficient.     

Analysis of air pollution during a severe smog episode of November 2012 and the Diwali Festival over Delhi,India

The hazardous combination of smoke and pollutant gases, smog, is harmful for health. The harmful smog episodes over London, the Meuse Valley, and Donora are some of the well-known pollution episodes formed due to the mixture of smoky fumes and adverse meteorological conditions. A severe smog episode was observed over Delhi, India, during November 2012, resulting in very low visibility and various respiratory problems. Very high values of pollutants (particulate matter, PM₁₀ as high as 989 µg m^?3, PM_2.5 as high as 585 µg m^?3, and nitrogen dioxide as high as 540 µg m^?3) were measured all over Delhi during the smog episode. In the study done, episodes of different nature and intensity are analysed based on remote-sensing data for 3 years (2010–2012): one of regional origin (the Delhi smog episode of 2012) and another of local origin (Diwali). Remote-sensing and in situ data have revealed an insight into the genesis and temporal and spatial variance during these episodes. Extensive use of satellite-derived parameters such as fire maps, the ultra violet aerosol index from the Aura satellite, and aerosol optical depth is made in the present study along with the output trajectories from the Hybrid Single-Particle Lagrangian-Integrated Trajectory model and in situ data. It is observed that during the smog episode all the aerosol optical depth, ultra violet aerosol index, PM_2.5, and PM₁₀ values surpassed those of the Diwali period (which in itself is a major dreaded annual air pollution event in the city) by a considerable amount at all stations across Delhi. The parameters used from the remote-sensing data and the ground-based observations at various stations across Delhi are very well in agreement with the intensity of smog episodes. The analysis clearly shows that regional pollution can have a greater contribution towards deteriorating air quality than local pollution under adverse meteorological conditions and is in agreement with other similar studies over Delhi.     

Impact of similarity between avatar and their users on their perceived identifiability: Evidence from virtual teams in Second Life platform

Research on the application of avatars in the virtual teams is growing. In this study, we examined the effect of perceived similarity of an avatar user with his/her avatar on the perceptions of his/her identifiability within a virtual team. The study utilized a sample of 124 users actively involved in Second Life, a virtual world platform. Results of structural equation modeling utilizing the partial least squares method corroborate the hypothesis. An important contribution of this research is to inform practitioners about the critical role that users’ similarity with the avatar plays in enhancing their identifiability. We draw conclusions based on the result and identify some important avenues for future research.     

Quantification of annual glacier surface mass balance for the Chhota Shigri Glacier,Western Himalayas,India using an Equilibrium-Line Altitude (ELA) based approach

ABSTRACT

In line with the increasing scientific interest on the Himalayan glaciers, this study focuses on estimating a long-term annual surface mass balance time series of the Chhota Shigri glacier, a ‘benchmark’ glacier in the western Himalayas. The approach used here is based on the fact that the annual glacier-wide surface mass balance can be deduced from the equilibrium-line altitude (ELA). Depending on the distribution and availability of multiple cloud free remotely sensed images during ablation period, a multi-temporal approach has been used to estimate ELA. When compared with field-based ELA, the results indicate that the multi-temporal approach resulted in better estimates of ELA than the conventional single image approach. Likewise, the annual surface mass balances quantified from this study closely match with field estimates over the common period (2003–2014) and even better than some estimates from earlier studies based on other proxies (meteorological data or glacier surface albedo). A sensitivity analysis shows that the annual surface mass balance quantified from the ELA-based approach is not very sensitive to changes in the mass balance gradient and average mass balance. Hence, the approach has been further applied to reconstruct the long-term annual surface mass balance series of the Chhota Shigri Glacier over the period 1989–2017. Our results show a good agreement between the reconstructed surface mass balance and estimates of other long-term studies. Therefore, this study indicates the great potential for this approach for quantifying the annual surface mass balance for glaciers with no ground data lying in same climatic zone.     

Sensor fault diagnostics for a class of non-linear systems using linear matrix inequalities

This paper develops a systematic approach to fault diagnostic system design for sensor health monitoring in Lipschitz non-linear systems. The methodology applies to non-linear systems with three or more sensors in which the state is observable through any one of the sensor measurements. Two major issues are addressed in the paper—observer design for the non-linear system to ensure directional growth of residues for failure identification and use of linear matrix inequalities for explicit design of the observer gain. The use of the methodology is demonstrated through an illustrative example.