Thermodynamic,spectroscopic, and molecular characterization of rice straw biomass for use as biofuel feedstock

India is one of the leading producers of rice in the world. Gasification and pyrolysis are two thermochemical processes. In the gasification process, biomass is transformed into syngas, which serves as an energy source. This conversion occurs under high temperatures with a carefully regulated and restricted air supply. On the other hand, pyrolysis, which transpires at lower temperatures without the presence of air, generates pyrolysis oil as a by-product. This oil can be further refined into liquid fuels. For the purpose of investigating the feasibility of biofuel production, the current study involved the characterization of rice straw biomass using various techniques such as thermogravimetry differential thermal analysis (TG/DTA), Fourier transform infrared (FTIR), carbon, hydrogen, nitrogen, sulphur and oxygen (CHNS/O), inductively coupled plasma optical emission spectroscopy (ICP-OES), among others. These analytical methods were employed to assess the potential of rice straw biomass for the production of biofuels. The existence of a significant amount of cellulose (32.1%), volatiles (approximately 67.06%), and high heating value (HHV) (13.18 MJKg⁻¹) in rice straw inferred their capability to be used as feedstocks in the production of biofuel. The activation energy of approximately 173.20 KJ/Mol (Flynn Wall Ozawa [FWO]) indicated the viability of the burning process. From master plot (Z(α)) analysis, the experimental curve was seen passing through different theoretical curves, indicating the complex nature of the pyrolysis process for rice straw.     

A fourth-order B-spline collocation method and its error analysis for Bratu-type and Lane–Emden problems

Recently, Caglar et al. [B-spline method for solving Bratu's problem, Int. J. Comput. Math. 87(8) (2010), pp. 1885–1891] proposed a numerical technique based on cubic B-spline for solving a Bratu-type problem. This method provides a second-order convergent approximation to the solution of the problem. In this paper, we develop a high-order numerical method based on quartic B-spline collocation approach for the Bratu-type and Lane–Emden problems. The error analysis of the quartic B-spline interpolation is carried out. Some numerical examples are provided to demonstrate the efficiency and applicability of the method and to verify its rate of convergence. The numerical results are compared with exact solutions and a numerical method based on cubic B-spline approach. Comparison reveals that our method produces more accurate results than the method proposed by Caglar et al. [B-spline method for solving Bratu's problem, Int. J. Comput. Math. 87(8) (2010), pp. 1885–1891].     

Distributed fault tolerant computation of weakly connected dominating set in ad hoc networks

Our purpose in this paper is to propose a self-stabilizing protocol for weakly connected dominating set (WCDS) set in a given ad hoc network graph. WCDS is a particular variant of graph domination predicates which play an important role in routing in ad hoc networks. There are many variants of domination problems in bidirectional networks; WCDS is also useful in forming clusters in ad hoc networks. There are many heuristic and distributed algorithms to compute WCDS in network graphs while almost all of them will need complete information about the network topology and most of them are not fault tolerant or mobility tolerant. Self-stabilization is a protocol design paradigm that is especially useful in resource constrained infrastructure-less networks since nodes can make moves based on local knowledge only and yet a global task is accomplished in a fault tolerant manner; it also facilitates for nodes to enter and exit the network freely. There exist self-stabilizing protocols for minimal spanning tree, total domination, and others. We have shown that the paradigm is capable of designing a protocol for WCDS. Our objective is to mathematically prove the correctness and the convergence of the protocol in any worst-case scenario, as is usually done for self-stabilizing protocols for other graph predicates used for ad hoc networks.     

Two-phase modeling of evaporation characteristics of ethanol droplet under force-convection environment

Studies on the evaporation phenomenon of a pure ethanol droplet have been mostly confined to the semianalytical modeling in stagnant ambient. Investigation into this aspect in a convective environment by considering the Navier–Stokes equation is also minimal. Hence, in this study we analyze and investigate the evaporation characteristics of a single-component spherical-shaped isolated pure ethanol droplet under force convective air environment by considering both gas- and liquid-phase motions, nonunitary Lewis number in the interface, variable Stefan flow (blowing) effect, and the transient droplet heating. The finite difference method is utilized while solving the governing equations of the spherical polar coordinate system for species, momentum, and energy transfer. The maximum Reynolds number and ambient temperature are kept at 100 and 600 K, respectively. The present work is validated by comparing the normalized surface regression curve of the droplet with the earlier experimental and theoretical results. Using the current simulated data, flow and temperature profiles of both gas and liquid regions are visualized in streamline and isotherm contour plots at various instants of time. It is observed that at a moderate Reynolds number a detached vortex forms at the downstream location of the droplet. However, the detachment length increases with time. The temperature gradients along the droplet surface are observed at the initial stage. Moreover, the heat-up period occupies about 20% of the total lifetime of the droplet. The droplet life and heat-up period decrease with an increase in free-stream velocity. In addition, the saturation temperature increases with ambient temperature.     

Stabilizing effect in nano-titania functionalized CdS photoanode for sustained hydrogen generation

Efficient and stable photoanode has been fabricated by the surface functionalization of the nanostructured film. For this, the surface of spray deposited CdS thin film was modified through bi-functional molecule mediated chemisorption of TiO₂ nanoparticles (NP). Consequently, a systematic control over efficiency and photoanode stability against corrosion has been investigated. An in-depth quantitative analysis of the photocorrosion of these photoanodes is further studied using chronoamperometry, X-ray photoelectron spectroscopy and induced coupled plasma spectroscopy. TiO₂ NP modified photoanodes show an enhanced efficiency and a stability. For photoelectrochemical (PEC) systems, the stability factor (∑) has been defined for the first time based on the time dependent chronoamperometry, which clearly demonstrates that ∑_modified >> ∑_bare. The modified photoanode shows an improved Incident Photon to Current Efficiency of 22% than the bare CdS (∼8%) electrode. It gives an enhanced solar-to-hydrogen conversion efficiency of STH ∼ 0.7% w.r.t bare CdS (0.2%) under AM 1.5G solar simulator, at 0.2 V/SCE. Improved stability of more than nine hours and enhanced efficiency is attributed to the controlled passivation of CdS surface through TiO₂ NP (5 nm), and inhibition of the charge recombination. Superior and stable performance of modified photoelectrode has been validated by higher and stable hydrogen evolution over modified electrode.     

Biodiesel from jatropha: Can India meet the 20% blending target?

The need for biofuels, particularly liquid ones like ethanol and biodiesel, has been felt by most of the countries and their governments have been trying to promote these fuels. Following in line with global trend, India declared its biofuel policy in which biodiesel, primarily from jatropha, would meet 20% of the diesel demand beginning with 2011–2012. In spite of the efforts made by the state, production of biodiesel, however, has not picked up at all. Doubt arises as to whether the country will be able to meet the target. It is felt that the government policy, particularly regarding land utilization, organizing cultivation of jatropha and pricing of jatropha seeds, needs to be more clear. This paper attempts to make an assessment of the state of India’s biofuel programme and to identify the hurdles that policy-maker need to overcome to achieve the goal.     

Structural characterization of vacuum evaporated ZnSe thin films

Thermally evaporated ZnSe thin films deposited on glass substrates within substrate temperatures (T _s)at 303 K-623 K are of polycrystalline nature having f.c.c. zincblende structure. The most preferential orientation is along [111] direction for all deposited films together with other abundant planes [220] and [311]. The lattice parameter, grain size, average internal stress, microstrain, dislocation density and degree of preferred orientation in the film are calculated and correlated with T _s.