Thermodynamic analysis of afterburning of detonation products in confined explosions

Abstract

In the paper, an attempt is undertaken to apply the thermodynamic theory of closed combustion, proposed by A. K. Oppenheim and co-workers, to analyse the process of afterburning of the detonation products of condensed explosives in a chamber filled with air. The principal assumptions of the theory are presented and the problem of combustion of fuel in a closed volume is formulated. The relations between thermodynamic parameters and fuel consumption are determined from the laws of conservation of volume, mass and energy. These relations are used to estimate the rate and heat effect of afterburning of the detonation products of some explosives in a steel chamber of 150 dm³ volume. The influence of assumed degree of mixing of the combustion products and air on the mean pressure in the chamber is discussed.     

Adsorption Studies of Chlorpropham and 3-Chloroaniline on Chemically Activated Halloysite

Chemically modified halloysite proved to be an effective adsorbent for the pesticide chlorpropham and 3-chloroaniline from an aqueous solution. Adsorption experiments were conducted using such procedures as the time-dependent （kinetic） procedure and the concentration dependent （isotherm） procedure. Results indicate that the adsorption process is related to the kind of the studied compound. The equilibrium data are well suited to a Freundlich isotherm in the case of both investigated compounds. Adsorption kinetics of chlorpropham and 3-chloroaniline on acid-treated halloysite was successfully described by pseudo-second order kinetic model and the model of Weber and Morris. From the present study, we suggest that the adsorption of chlorpropham and 3-chloroaniline on the modified halloysite is a rather complex process involving two steps： external mass transfer and intra-particle diffusion.     

Selection of yeast strains for alcoholic fermentation of sugar beet thick juice and green syrup

Presented work aimed at determination of effect of various strains of yeast Saccharomyces cerevisiae and concentration of fermentation worts on dynamics and efficiency of alcoholic fermentation. Fermentation worts contained either thick juice or green syrup.It was found that yeast strains designated as M₁, M₂ and D-2 most efficiently fermented thick juice worts inoculated with yeast cream at a rate of 2 kg m⁻³ of wort. Fermentation processes lasted for approximately 2 days and ethanol yield approached 92-94% of the theoretical yield. Fermentations of green syrup worts were most efficient (ethanol yield reached 90-92% of the theoretical yield) when these processes were carried out by yeast strains M₁, M₂, D-2 and As4 (inoculum - 2 kg m⁻³ of wort).S. cerevisiae strains M₁ and M₂ dynamically and efficiently fermented thick juice worts with extract of 200 g kg⁻¹ and 250 g kg⁻¹ (89-94% of the theoretical yield) while strain D-2 preferred less dense worts (extract of 200 g kg⁻¹) and produced ethanol with the yield of over 92% of the theoretical yield. The optimum green syrup worts extract was 200 g kg⁻¹.     

Detection of early bruises in apples using hyperspectral data and thermal imaging

The early detection of bruises in apples was studied using a system that included hyperspectral cameras equipped with sensors working in the visible and near-infrared (400–1000 nm), short wavelength infrared (1000–2500 nm) and thermal imaging camera in mid-wavelength infrared (3500–5000 nm) ranges. The principal components analysis (PCA) and minimum noise fraction (MNF) analyses of the images that were captured in particular ranges made it possible to distinguish between areas with defects in the tissue and the sound ones. The fast Fourier analysis of the image sequences after pulse heating of the fruit surface provided additional information not only about the position of the area of damaged tissue but also about its depth. The comparison of the results obtained with supervised classification methods, including soft independent modelling of class analogy (SIMCA), linear discriminant analysis (LDA) and support vector machines (SVM) confirmed that broad spectrum range (400–5000 nm) of fruit surface imaging can improve the detection of early bruises with varying depths.     

Evaluation of the mechanical behavior of W7-X central support connections by means of semi-automated FE analysis

The stellarator Wendelstein 7-X is under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald. Its superconducting coil system is fixed by a massive structure. During machine operation the coils exert high forces and moments against each other and the central support structure (CSS). Therefore, the detailed analysis of the coil to CSS connections, the so-called central support elements (CSE), is a critical item. The major details of the design have been frozen; nevertheless, there is still need for detailed analysis of the CSEs due to assembly issues, and later on for exploring operational limits of the machine. These analyses have to be performed quickly, reliably, and shall provide results in a standardized form to enable timely responses to the assembly team. Special numerical tools – finite element (FE) parametric models of CSEs – have been developed for the purpose of such analyses. In the models, the geometry, material properties, contact conditions, loads as well as results presentation are defined in a parametric way. The use of the developed models for the definition of the final weld parameters, bolt preloads, assessment of acceptable tolerances, and optimal positions of the CSE-wedges before welding is also discussed.     

Surface effects and flow conditions in small volume melts with varying sulphur content

The surface effects and flow behaviour in melts with a volume of a few cubic millimetres were investigated using 1 mm thick X5CrNi18‐9 (AISI 304) stainless steel strips after partial remelting by a TIG (tungsten inert gas) burner. In the industrially produced material the S mass content was varied between 20 and 100 ppm. The surface excess of sulphur indicates that the surface saturation was not achieved compared to the values in the Fe‐S system. The thickness of the layer with high sulphur enrichment depends on the S activity and varied between approximately 260 and 460 nm and achieves the bulk S content at a distance of approximately 1.2 μm from the surface. This layer is noticeably thinner than the diffusion boundary layer and considerably thinner than the flow boundary layer. The topography of the rapidly solidified liquid pool makes it possible, taking previously estimated temperature coefficients of surface tension into account, to explain the flow behaviour in the melt with regard to the S content and to the temperature gradients. The results obtained indicate that the shearing force caused by surface tension gradients (Marangoni effect) controls the flow conditions in small volume melts.     

Passivation of pinhole defect microelectrode arrays in ultrathin silica films immobilized on gold substrates

Nanoscopic defects present in ultrathin (~ 6 nm) silica films covalently attached to gold substrates through a gold oxide layer exhibit a voltammetric response consistent with a random array of ultramicroelectrodes. These pinholes can be passivated via electrochemical polymerization of phenol to create insulating poly(phenylene) oxide plugs as documented by atomic force microscopy and infrared reflectance-absorbance spectroscopy. Passivation of pinholes is ~ 99.5% complete after 550 voltammetric cycles of oxidative electropolymerization.     

Transgenic DNA integrated into the oat genome is frequently interspersed by host DNA

Integration of transgenic DNA into the plant genome was investigated in 13 transgenic oat (Avena sativa L.) lines produced using microprojectile bombardment with one or two cotransformed plasmids. In all transformation events, the transgenic DNA integrated into the plant genome consisted of intact transgene copies that were accompanied by multiple, rearranged, and/or truncated transgene fragments. All fragments of transgenic DNA cosegregated, indicating that they were integrated at single gene loci. Analysis of the structure of the transgenic loci indicated that the transgenic DNA was interspersed by the host genomic DNA. The number of insertions of transgenic DNA within the transgene loci varied from 2 to 12 among the 13 lines. Restriction endonucleases that do not cleave the introduced plasmids produced restriction fragments ranging from 3.6 to about 60 kb in length hybridizing to a probe comprising the introduced plasmids. Although the size of the interspersing host DNA within the transgene locus is unknown, the sizes of the transgene-hybridizing restriction fragments indicated that the entire transgene locus must be at least from 35-280 kb. The observation that all transgenic lines analyzed exhibited genomic interspersion of multiple clustered transgenes suggests a predominating integration mechanism. We propose that transgene integration at multiple clustered DNA replication forks could account for the observed interspersion of transgenic DNA with host genomic DNA within transgenic loci.     

Diffusion of polymer chains in porous media. A Monte Carlo study

In order to determine the structure and the dynamical properties of branched polymers in a random environment an idealized model was developed and studied by means of the Monte Carlo method. All atomic details were suppressed and the chain was represented as a sequence of identical beads. The model chains were star-branched with three arms of equal length. The chains were embedded to a simple cubic lattice and the polymer systems were confined between two parallel surfaces. The confining surfaces were attractive for polymer segments. A set of irregular obstacles was also introduced into the slit which can be viewed as a model of porous media. A Metropolis sampling algorithm employing local changes of chain conformation was used to sample the conformational space. It was shown that the mean dimensions of the chain depend strongly on the strength of surface's attraction and the concentration of obstacles. It was found that the size of the chains scales with the exponent close to the 2-dimensional case rather than to the 3-dimensional system. The long-time (diffusion) dynamic properties of the system were studied. The differences in the mobility of chains depending on the confinement, on the filling of the slit and on the internal macromolecular architectures were shown and discussed. The possible mechanism of chain's motion was shown: during the migration of the chain in the obstacles dense environment it can be trapped in the region of local lower density of obstacles (a ‘cavity’) and after some time it can leave the place moving into another cavity.