Presence Of Vertices Research Articles

Flame structure and dynamics in pool fires of different geometries: Experimental and numerical investigation

Fire accidents might be caused by liquid fuel leakage, which can accumulate in a prescribed area under the action of physical barriers. Therefore, pool fires could be of an arbitrary geometry in less ideal configurations. The current objective is to uncover the underlying physics of flame structure and dynamics in pool fires of different geometries. In this work, pool fires with seven different geometries were examined. Flame base structure and instantaneous flame height in pool fires of different geometries were recorded. Temperature, velocity/vorticity fields and coherent vortical structures were further presented by Large Eddy Simulation (LES). Results show that mean flame height of circular pool fire is the highest, while that of right triangle fires is the lowest. Mean flame height of the other noncircular geometries lies in these two extremes. The presence of vertices and hypotenuses has a dramatic influence on the formation and development of vortical structures. Triangular pool fires have the highest oscillation frequency, followed by quadrangular and circular geometries. To account for the physics of air entrainment and vortex dynamics due to pool fire geometry, pool perimeter is used as a characteristic length scale to propose new scaling relations for describing flame height and oscillation frequency.

Algorithm for the route’sformation of food raw materials procure-ment on the community territory taking into account the production conditions during emergency situations

The article concerns the improvement of the ACO (Ant Colony Optimization) ant colony optimization algorithm for the formationof routes of vehicles for the procurement of food raw materials on the territory of the community during emergencies. The purpose of the study is to improve the algorithm for the formation of routes of vehicles for the procurement of food raw materials on the territory of the community during emergencies. The proposed algorithm is based on the classical algorithm of ant colony optimization ACO and, unlike it, takes into account real production conditions during emergencies. The task of the research is to create an algorithm for the formation of effective routes of vehicles for the procurement of food raw materials in the territory of the community during emergencies, as well as its comparison with the classic ACO algorithm for solving various problems of route formation. It was established that the use of the classic algorithm for the optimization of ant colonies ACO, or its known modernizations, does not provide a high-quality solution to the problem of forming routes of vehicles for harvesting food raw materials on the territory of the community during emergencies.This is due to incomplete consideration of specific production conditions. The improved route formation algorithm involves 8 steps and is based on the classic ACO algorithm. In contrast to it, it takes into account real production conditions (damaged sections of the roadway,the presence of partial passage of vehicles, traffic jams caused by an emergency, etc.). The rule of the classic ACO algorithm regarding the selection of the next point in the route using the probabilistic-proportional transition of the k-th ant from the i-th to the j-th node (farm producing food raw materials) is proposed, replaced by one that takes into account the state of production conditions (road surface) be-tween individual nodes. This ensures an increase in accuracy and a decrease in the duration of route formation, as well as an increase in the quality of making appropriate management decisions. The obtained results regarding the comparison of the use of algorithms when solving transport problems with a different number of vertices indicate that the proposed algorithm provides a deviation of the total path in the route, which does not exceed 1%. The proposed algorithm reduces the decision-making time by up to 6% in the presence of up to 50 units of vertices, and by 12...15% in the presence of vertices from 51 to 100 units. The improved vehicle routing algorithm can be used in decision-making support systems to plan the procurement of food raw materials on the territory of the community during emer-gencies, which will increase their efficiency.

A Tool for Predicting Heating Uniformity in Industrial Radio Frequency Processing

Radio frequency energy is utilised for heating in a wide range of applications, particularly in the food industry. A major challenge of RF processing is non-uniform heating in loads of variable and angular geometry, leading to reduced quality and product damage. In the study, the specific effects of geometry on the heating profiles of a range of geometrically variable loads in an industrial scale RF system are analysed, and the understanding used to derive a general tool to predict heating uniformity. Potato was selected as a test material for experimental work; dielectric properties were measured using a 44mm coaxial probe. Analysis of simulated and experimental surface temperature profiles and simulated power uniformity indices indicates that the presence of vertices and edges on angular particles, and their proximity to faces perpendicular to the RF electrodes increases localised heating; faces parallel to the electrodes heated less than those faces perpendicular to them. Comparison of the same geometrical shape in different orientations indicates that overall power absorption uniformity can be better even when localised heating of edges is greater. It is suggested, for the first time, that the rotation of angular shapes within a parallel plate electric field can improve heating uniformity, and that this can be achieved through the design of bespoke electrode systems. A Euler characteristic based shape factor is proposed, again for the first time, that can predict heating uniformity for solid, dielectrically homogenous shapes. This provides industry with a tool to quickly determine the feasibility for uniform RF heating of different three dimensional shapes based on geometry alone. This provides a screening method for food technologists developing new products, allowing rapid assessment of potential heating uniformity and reducing the need for early stage specialist computational modelling.

A foam drainage equation generalized for all liquidcontents

Recently the study of liquid drainage through foams hasgenerated considerable experimental and theoretical research.This research has usually made the assumptions that the liquidcontent is very low and that the viscous resistance islimited to occurring within either the Plateau borders or vertices.This paper presents a foam drainage model that notonly describes the low-liquid-content extreme, but also takes account ofliquid content effects. These include the increase in the foamvolume with increasing liquid content and the increase in theliquid flowrate in the Plateau borders over the averageflowrate brought about by the presence of vertices. The relativeimportance of the Plateau borders and vertices to viscous losswithin the foam is also made dependent on the liquid content ofthe foam.This model is verified experimentally for two surfactant typesand various bubble sizes using a standard forced drainagesystem.

Staggered conformers of alkanes: complete solution of the enumeration problem

Staggered conformers of alkanes are represented as chemical graphs by angle-restricted trees which can be embedded in a diamond lattice; they are referred to as alkane systems. The enumeration of unbranched alkane systems, which correspond to staggered n-alkanes, are revisited. When the branched systems are included the corresponding enumeration problem is substantially more difficult, but was solved completely in terms of generating functions. This solution pertains to both non-overlapping and overlapping systems, where the latter category is characterized by the presence of vertices which occupy the same sites in the diamond lattice. Hand in hand with the mathematical solution, the alkane systems were also generated and enumerated by computer programming. In particular, this approach gave new information about the non-overlapping systems. Finally, several classes of systems, especially among the overlapping alkane systems, were generated by hand according to combinatorial constructions. A special classification of the alkane systems according to the constitutional isomers is supposed to be of particular interest in structural chemistry. Symmetry considerations, which imply the distribution of the alkane systems into sixteen symmetry groups, play an important role in this work.

Electronic Factors Controlling Bandwidths in Oxides with the Perovskite and Cadmium Halide Structures

The electronic structure of oxides with the perovskite and cadmium halide structures are derived using tightbinding theory and the angular overlap model. The control of the form of the energy bands by the presence of vertex(perovskite) and edge-sharing (cadmium halide) of the coordination octahedra is first explored using onedimensional examples. For one-, two-, and three-dimensional structures of the perovskite type, a very interesting result is uncovered. It is shown that on the band model a band gap may only arise if the oxygen 2s orbital is included in the orbital problem. Prediction of the magnitude of the band gaps in d6 perovskites is thus not a simple matter. This band structure, derived from tight-binding theory via the construction of Bloch orbitals, is compared with an energy band scheme based on local crystal field orbitals and covalent metal-oxygen interactions, which has traditionally been used in this area.

Instability, softening and localization of deformation

Abstract Material strain softening is commonly taken as a necessary and sufficient condition for localization in deforming rocks. However, there is a wide range of experimental and theoretical information which shows that localization can occur in sands, brittle rocks and ductile metals under strain-hardening conditions. This paper aims to bring these two contrasted views together. Three separate criteria are necessary in order to understand localization behaviour. The first involves the stability of the deforming system. The second determines whether a deforming system will undergo bifurcation so as to cease deforming in a homogeneous mode and instead deform in an inhomogeneous mode such as barrelling or localization. The stability and bifurcation criteria are independent of each other since barrelling is a stable mode whereas localization is unstable. The third criterion establishes if the unstable bifurcation mode is one of localization or of some other kind. Localization may arise from the presence of vertices on the yield surface (as in the case of pressure insensitive, rate dependent metals and in brittle rocks due to the development of preferred microfractures for slip) or from the constitutive relation being such that the plastic strain-rate vector is not normal to the yield surface (as in the cases of pressure sensitive, dilatant rocks, of materials deforming by crystal-plastic processes involving dislocation cross-slip and/or climb, and of visco-plastic materials in which voids are forming due to diffusive processes). It is important to distinguish between material and system softening (or hardening) behaviour. The theory for a kinematically unconstrained shortening experiment (that is, rigid, frictionless platens) indicates that localization can occur in strain-hardening materials but the system must strain-soften from then on; that is, localization occurs at peak stress for the system even though the material may continue to harden (or soften). However, the addition of kinematic constraints (such as friction at elastic platens, a constraint to deform in plane strain or at constant volume) means that localization may occur in a system that is monotonically strain hardening. Shear zones in naturally deformed rocks show ample evidence of dilatant behaviour in that evidence for the passage of large volumes of fluid during localization is common as is the development of dilatant vein systems. As such, since shear zones are strongly constrained by the elastic and (limited) plastic response of the relatively undeformed rocks surrounding the shear zones, strain-hardening behaviour of the system is to be expected as the norm, even if the rocks within the shear zones are undergoing material strain-softening.