Calculation of Decomposition Products from Components of Gunpowder by using ReaxFF Reactive Force Field Molecular Dynamics and Thermodynamic Calculations of Equilibrium Composition

The major combustion products from munitions containing nitro‐based propellants are water, carbon monoxide, carbon dioxide, hydrogen, and nitrogen. In addition, compounds including hydrogen cyanide, ammonia, methane, nitrogen oxides, benzene, acrylonitrile, toluene, furan, aromatic amines, benzopyrene, and various polycyclic aromatic hydrocarbons are detected in minor concentrations. The literature shows that the thermodynamic prediction of the major decomposition products agrees fairly well with the measurements. However, poor agreement is found for the minor species. We have studied the thermal decomposition products of the main gunpowder ingredients. Each of the components nitrocellulose, nitroglycerine, and the nitrate ester stabilizers diphenylamine and ethyl centralite were thermally decomposed with ReaxFF reactive force field molecular dynamics and equilibrium thermodynamics. The molecular dynamics results for the major decomposition products from nitrocellulose were partly consistent with measurements. Compared to the thermodynamic calculations, the molecular dynamics simulations agreed considerably better with experimental results for minor species like hydrogen cyanide. The nitrate ester stabilizers are the main sources for ammonia and aromatic combustion products, whereas hydrogen cyanide is produced from nitrocellulose as well as from the stabilizers when gunpowder is combusted.     

An integral equation method for the numerical solution of a Dirichlet problem for second-order elliptic equations with variable coefficients

We study how fiber-reinforced materials will naturally undergo swelling deformations in which a relatively greater stretch occurs transverse to the fibers than in the fiber direction. This means that a pattern of initially curved fibers prior to swelling will tend to straighten out as swelling proceeds. This can lead to swelling-induced deformations with a high degree of localized shearing and significant overall twisting. Such a process is examined for a plane strain swelling deformation that combines twist with radial expansion. Analytical results are obtained for both types: small and large swelling. Of particular interest is the relation of the extensible fiber theory to a theory for inextensible fibers. We examine the extent to which the former approaches the latter in the limit as the fibers are taken to be progressively stiffer.     

Consideration of uncertainties in LCA for infrastructure using probabilistic methods

The construction and usage of transport infrastructure are major causes of greenhouse gas emissions and energy consumption. The effects of resource consumption and pollutant emissions are often quantified through Life Cycle Assessment (LCA) models. All decisions made in infrastructure projects during the whole life cycle are afflicted by uncertainty, e.g. physical properties of materials or amount of pollutants emitted by certain processes. The pervasive role of uncertainty is reflected in LCA models, which therefore should consider uncertainty from various sources and provide a sound quantification of their effects. The aim of the work presented in this paper is to give an overview of different sources of uncertainty in LCA of infrastructure projects and to describe systematic methods to evaluate their influence on the results. The possibility of including uncertainty in a LCA-tool for infrastructure is presented, studying the sensitivity of the model output to the input parameters and two alternative approaches for propagation of uncertainty using two case studies. It is shown that, besides the influence of uncertainty in emission factors, other inputs such as material amounts and service life could contribute significantly to the variability of model output and has to be considered if reliable results are sought.     

Luminescence of 2,6-Distyrylpyridine-Doped Titania Nanostructured Monoliths

Nanocrystalline 2,6-distyrylpyridine (2,6-DStP)-doped TiO₂ monoliths were prepared by the sol–gel technique. Different concentrations of the 2,6-DStP doping agent were utilized. Samples were characterized by x-ray diffraction, photoacoustic spectroscopy (optical absorption), and luminescence spectroscopy. As-prepared samples showed amorphous structure and traces of the anatase crystalline phase of TiO₂ after annealing at room temperature. The samples exhibited average particle size from 6 nm to 7.5 nm for molar concentration of 2,6-DStP from 0.0% to 0.03%. The photoacoustic spectra revealed the absorption edge at wavelength around 375 nm (3.38 eV), which is attributed to TiO₂, and a gap shift varying from 1.91 eV, to 2.41 eV, to 1.86 eV with the molar concentration of 2,6-DStP. Photoluminescence spectroscopy showed three different bands around 555 nm, 607 nm, and 779 nm when the samples were excited with 407 nm, 488 nm, and 633 nm laser lines, respectively.     

Dissolution of Lignin in Kraft Pulp by Oxygen Bleaching

Gel permeation chromatography of spent liquors from oxygen bleaching showed that cleavage of covalent linkages in the fiber was a prerequisite for the dissolution of the lignin. The reactions continued in the liquor phase. The cleavage was related to the oxidation of the lignin. With pulps pretreated with nitrogen dioxide an appreciable number of lignin linkages were cleaved also by the direct influence of the hydroxide ions on the nitrated lignin. In the alkaline medium the acidic sites in the fiber and in dissolved lignin fragments are ionized. Donnan-exclusion and an increased fiber swelling promote the transfer of the fragments into the liquor. Hydrophilic groups introduced into the lignin during oxygen bleaching promote the delignification.     

Effect of silica sol on the dispersion–gelation process of concentrated silica suspensions for fibre-reinforced ceramic composites

Sol gel process of silica powders dispersed in silica sol has been used to obtain a suitable suspension for the sol infiltration technique of fibre-reinforced ceramics. Efforts have been focused on analysing the effects of polyelectrolyte content, pH, solid load and concentration of gelling agent on the flow behaviour of silica suspensions. The most adequate suspension to manufacture the matrix of composites is a weak flocculated suspension with negligible thixotropic behaviour at pH ≥ 9.5, which is composed of silica microparticles dispersed in silica sol with 41 vol.% of solid load and 1.8 wt.% of Duramax D3005. This suspension easily undergoes a transition to a gel by a slight alteration of stability conditions adding 0.08 M of NH₄Cl, which reduces both the electrostatic repulsion and the pH to 8. Moreover, silica sol promotes the densification of ceramics up to 70% after sintering at 900 °C, allowing porous matrix processing of the composites.     

Prioritizing sustainable electricity production technologies: MCDM approach

Economic, technological, social, and political developments stressed the need for shifts in energy-mix. Therefore it is important to provide a rationale for sustainable decision making in energy policy. The aim of this paper is to develop the multi-criteria decision support framework for choosing the most sustainable electricity production technologies. Given selection of sustainable energy sources involves many conflicting criteria, multi-criteria decision methods MULTIMOORA and TOPSIS were employed for the analysis. The indicator system covering different approaches of sustainability was established. The analysis proved that the future energy policy should be oriented towards the sustainable energy technologies, namely water and solar thermal ones. It is the proposed multi-criteria assessment framework that can constitute a basis for further sub-regional optimization of sustainable energy policy.     

Demand for gasoline is more price-inelastic than commonly thought

One of the most frequently examined statistical relationships in energy economics has been the price elasticity of gasoline demand. We conduct a quantitative survey of the estimates of elasticity reported for various countries around the world. Our meta-analysis indicates that the literature suffers from publication selection bias: insignificant or positive estimates of the price elasticity are rarely reported, although implausibly large negative estimates are reported regularly. In consequence, the average published estimates of both short- and long-run elasticities are exaggerated twofold. Using mixed-effects multilevel meta-regression, we show that after correction for publication bias the average long-run elasticity reaches ? 0.31 and the average short-run elasticity only ? 0.09.     

A Kinetic Study of the Liquid Phase Acetoxylation of α-Pinene

The present study introduces kinetic modeling of liquid phase ??-pinene acetoxylation with acetic acid over an ion-exchange resin catalyst. The reaction was carried out in a laboratory scale high-pressure autoclave. ??-terpinyl (35?wt%) and bornyl (40?wt%) acetates were the primary products. The predominant reaction pathways were identified and evaluated.