310 research outputs found
Runaway decomposition of dicumyl peroxide by open cell adiabatic testing at different initial conditions
No full textLow-thermal inertia experiments in the open cell configuration were carried out to perform a comprehensive sensitivity analysis of the parameters affecting the runaway self-decomposition of dicumyl peroxide (DCP). This study facilitates a better understanding on how concentration, initial back pressure, and fill level influence DCP runaway severity. The outcome of this experimental study was compared to previous adiabatic closed cell experiments, with the aim of clarifying the discrepancies reported in the literature and contributing to essential knowledge about self-decomposing peroxide systems. Results showed that the detected onset temperature, maximum temperature, maximum pressure, and time to maximum rate are affected by the configuration of the equipment and initial back pressure of the experiments, while the adiabatic temperature rise did not seem to be affected. The roles that the kinetics, fluid dynamics, and thermodynamics play on these observations is addressed and discussed through the manuscript
Experimental sensitivity analysis of the runaway severity of Dicumyl peroxide decomposition using adiabatic calorimetry
No full textThe behavior of Dicumyl peroxide (DCP) under runaway conditions was studied using low and high phi factor (φ) calorimeters. Solutions of 20, 30 and 40%, by weight, of DCP in 2,2,4-trimethyl-1,3-pentanediol diisobutyrate and cumene were run at different phi factors experiments(1.8 > φ > 1.1). The results depicted that cumene reduces the severity of the runaway decomposition of DCP, while the phi factor of the experiments showed to have a high influence on the rise of temperature and pressure. Values up to 18 and 27 times higher, respectively, were obtained at same concentration when reducing the phi factor from 1.8 to 1.1. Temperatures and self-heating rates obtained at different phi factor experiments were scaled up to a phi factor equal to 1.0 using the correction method recommended by the Design Institute for Emergency Relief System (DIERS) and developed by Fisher [1]. The results showed that this method works well at low concentrations. However, at the highest concentration, fast heating rates (up to 600 °C/min) were observed in the low phi factor equipment. These fast heating rates, most probably caused the equipment to loss its adiabaticity, and the scale up of the temperatures and self-heating rates did not longer give reliable results. This means that the estimation of experimental variables such temperature and rate of temperature rise (used for vent sizing calculations), directly from the data obtained at lab scale, even when using an advance low phi factor equipment, can result in under-conservative design calculations
M-theory moduli from exceptional complex structures
No full textAbstract We continue the analysis of the geometry of generic Minkowski N = 1, D = 4 flux compactifications in M-theory using exceptional generalised geometry, including the calculation of the infinitesimal moduli spaces. The backgrounds can be classified into two classes: type-0 and type-3. For type-0, we review how the moduli arise from standard de Rham cohomology classes. We also argue that, under reasonable assumptions, there are no appropriate sources to support compact flux backgrounds for this class and so the only solutions are in fact G2 geometries. For type-3 backgrounds, given a suitable ∂ ′ ∂ ¯ ′ -lemma, we show that the moduli can be calculated from a cohomology based on an involutive sub-bundle of the complexified tangent space. Using a simple spectral sequence we prove quite generally that the presence of flux can only reduce the number of moduli compared with the fluxless case. We then use the formalism to calculate the moduli of heterotic M-theory and show they match those of the dual Hull-Strominger system as expected
Exceptional complex structures and the hypermultiplet moduli of 5d Minkowski compactifications of M-theory
No full textWe present a detailed study of a new mathematical object in E6(6)ℝ+ generalised geometry called an ‘exceptional complex structure’ (ECS). It is the extension of a conventional complex structure to one that includes all the degrees of freedom of M-theory or type IIB supergravity in six or five dimensions, and as such characterises, in part, the geometry of generic supersymmetric compactifications to five-dimensional Minkowkski space. We define an ECS as an integrable U*(6) × ℝ+ structure and show it is equivalent to a particular form of involutive subbundle of the complexified generalised tangent bundle L1 ⊂ Eℂ. We also define a refinement, an SU*(6) structure, and show that its integrability requires in addition a vanishing moment map on the space of structures. We are able to classify all possible ECSs, showing that they are characterised by two numbers denoted ‘type’ and ‘class’. We then use the deformation theory of ECS to find the moduli of any SU*(6) structure. We relate these structures to the geometry of generic minimally supersymmetric flux backgrounds of M-theory of the form ℝ4,1 × M, where the SU*(6) moduli correspond to the hypermultiplet moduli in the lower-dimensional theory. Such geometries are of class zero or one. The former are equivalent to a choice of (non-metric-compatible) conventional SL(3, ℂ) structure and strikingly have the same space of hypermultiplet moduli as the fluxless Calabi-Yau case
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