The pyrolysis of propane

The pyrolysis of propane plays an important role in determining the combustion properties of natural gas mixtures and offers insight into the cracking patterns of larger fuels. This work investigates propane pyrolysis behind reflected shock waves with a multiwavelength laser-absorption speciation technique. Nine laser wavelengths, sensitive to key pyrolysis species, were used to measure absorbance time histories during the decomposition of 2% propane in argon between 1022 and 1467 K, 3.7-4.3 atm. Absorbance models were developed at each diagnostic wavelength to interrogate common initial conditions, and time histories of all major species are reported at 1250, 1290, 1330, 1370, and 1410 K. Nearly complete carbon recovery observed at lower temperatures enabled the inference of hydrogen formation from atomic conservation, while decaying carbon recovery at high temperatures suggests the formation of allene and 1-butene. The results show systematically faster pyrolysis than predicted by kinetic modeling and motivate further study into the kinetics of propane pyrolysis.     

A Close Look at the Molecular Structure,Prototropic Behavior and Supramolecular Architecture of (E)-4-Bromo-2-[(phenylimino)methyl]-5-methoxyphenol by Spectroscopic,Crystallographic, and Computational Methods

Crystallography Reports - In this study, the molecular structure, prototropic behavior and supramolecular architecture of a new Schiff base have been studied in depth using spectroscopic (UV-vis),...     

On converse H-theorem

In the present paper the so-called weighting process is defined. Conditions on the weights implying the converse H-theorem are given. These conditions are satisfied by the iterated weighting process which contains, as a particular case, the Bayesian model for prediction and retrodiction given by S. Watanabe.     

“神龙一号”直线感应加速器物理设计

介绍了 “神龙一号”直线感应加速器物理设计的主要考虑。“神龙一号”加速器是一台电子直线感应加速器,由3.6MeV感应迭加型注入器、72个感应加速腔、脉冲功率系统、束流输运和聚焦系统、控制系统和真空、绝缘油、绝缘气体以及去离子水系统组成。能产生20MeV、束流大于2.5kA,脉冲宽度为60ns的强流脉冲电子束,X光焦斑均方根直径为1.5mm。     

Further Results for kth order Kantorovich Modification of Linking Baskakov Type Operators

In this paper we consider a non-trivial link between Baskakov type operators and their genuine Durrmeyer type modification as well as the kth order Kantorovich variant. Recursion formulas for the moments and the images of monomials are proved in order to derive asymptotic expansions. Furthermore we investigate convexity properties of the linking operators and the limiting behavior for certain function spaces.     

Well-posedness for a phase-field transition system endowed with a polynomial nonlinearity and a general class of nonlinear dynamic boundary conditions

This work is devoted to the study of a phase-field transition system of Caginalp type endowed with a general polynomial nonlinearity and a general class of nonlinear and nonhomogeneous dynamic boundary conditions (in both unknown functions). The existence, uniqueness and regularity of solutions are established. Here we extend several results proved by some authors, including the already studied boundary conditions, which makes the present mathematical model capable of revealing the complexity of a wide class of physical phenomena (for instance, phase change in Ω at the boundary of Ω).     

On whistling of pipes with a corrugated segment: Experiment and theory

Corrugated pipes are commonly used because of their local rigidity combined with global flexibility. The flow through such a pipe can induce strong whistling tones, which is an environmental nuisance and can be a threat to the mechanical integrity of the system. This paper considers the use of a composite pipe: a shorter corrugated pipe segment embedded between smooth pipe segments. Such a pipe retains some flexibility, while the acoustical damping in the smooth pipe reduces whistling tones. Whistling is the result of coherent vortex shedding at the cavities in the wall. This vortex shedding is synchronized by longitudinal acoustic waves traveling along the pipe. The acoustic waves trigger the vortex shedding, which reinforces the acoustic field for a critical range of the Strouhal number values. A linear theory for plane wave propagation and the sound production is proposed, which allows a prediction of the Mach number at the threshold of whistling in such pipes. A semi-empirical approach is chosen to determine the sound source in this model. This source corresponds to a fluctuating force acting on the fluid as a consequence of the vortex shedding. The functional form of the Strouhal number dependency of the dimensionless sound source amplitude is based on numerical simulations. The magnitude of the source and the Strouhal number range in which it can drive whistling are determined by matching the model to results for a specific corrugated pipe segment length. This semi-empirical source model is then applied to composite pipes with different corrugated segment lengths. In addition, the effect of inlet acoustical convective losses due to flow separation is considered. The Mach number at the threshold of whistling is predicted within a factor 2.     

Structural Transformations of Ni1 – xCuxFe2O4 Nanoparticles Depending on the Number of Cu Ions

Physics of the Solid State - Changes in the structure and properties of the Ni1 – xCuxFe2O4 ferrites-spinel magnetic nanoparticles depending on the Cu ion concentration (0...