Alternating heat transfer between objects of large geometrical difference

The heat transfer on the surface of an object in a gas fluidised bed is sequentially and alternately induced by particle-packet and gas bubble. This phenomenon is studied with computational simulation. The particle-packet and bubble are modelled by a double particle-layers and porous medium model and a hemispherical model, respectively. The heat transfer to and within the object is simulated concurrently. Different grid schemes are applied and different grid sizes are used in meshing the particle-packet and the object as there is a very large difference in their geometrical sizes. Based on theoretical analysis, an approximate method is developed to calculate the heat flux at the surface of the object. The simulation is implemented in a CFD package and the results are compared with experiments.

Geometrical effects on residual stresses in 7050-T7451 aluminum alloy rods subject to laser shock peening

Laser shock peening (LSP) is an emerging surface treatment technology for metallic materials, which appears to produce more significant compressive residual stresses than those from the conventional shot peening (SP) for fatigue, corrosion and wear resistance, etc. The finite element method has been applied to simulate the laser shock peening treatment to provide the overall numerical assessment of the characteristic physical processes and transformations. However, the previous researchers mostly focused on metallic specimens with simple geometry, e.g. flat surface. The current work investigates geometrical effects of metallic specimens with curved surface on the residual stress fields produced by LSP process using three-dimensional finite element (3-D FEM) analysis and aluminium alloy rods with a middle scalloped section subject to two-sided laser shock peening. Specimens were numerically studied to determine dynamic and residual stress fields with varying laser parameters and geometrical parameters, e.g. laser power intensity and radius of the middle scalloped section. The results showed that the geometrical effects of the curved target surface greatly influenced residual stress fields.

Geometrical effects on residual stresses in 7050-T7451 aluminum alloy rods subject to laser shock peening

Laser shock peening (LSP) is an emerging surface treatment technology for metallic materials, which appears to produce more significant compressive residual stresses than those from the conventional shot peening (SP) for fatigue, corrosion and wear resistance, etc. The finite element method has been applied to simulate the laser shock peening treatment to provide the overall numerical assessment of the characteristic physical processes and transformations. However, the previous researchers mostly focused on metallic specimens with simple geometry, e.g. flat surface. The current work investigates geometrical effects of metallic specimens with curved surface on the residual stress fields produced by LSP process using three-dimensional finite element (3-D FEM) analysis and aluminium alloy rods with a middle scalloped section subject to two-sided laser shock peening. Specimens were numerically studied to determine dynamic and residual stress fields with varying laser parameters and geometrical parameters, e.g. laser power intensity and radius of the middle scalloped section. The results showed that the geometrical effects of the curved target surface greatly influenced residual stress fields.

Optimal range-difference-based localization considering geometrical constraints

This paper proposes a new type of algorithm aimed at finding the traditional maximum-likelihood (TML) estimate of the position of a target given time-difference-of-arrival (TDOA) information, contaminated by noise. The novelty lies in the fact that a performance index, akin to but not identical with that in maximum likelihood (ML), is a minimized subject to a number of constraints, which flow from geometric constraints inherent in the underlying problem. The minimization is in a higher dimensional space than for TML, and has the advantage that the algorithm can be very straightforwardly and systematically initialized. Simulation evidence shows that failure to converge to a solution of the localization problem near the true value is less likely to occur with this new algorithm than with TML. This makes it attractive to use in adverse geometric situations.

Design and simulation of a RF MEMS shunt switch for Ka and V bands and the impact of varying its geometrical parameters

RF MEMS plays an important role in microwave switching. The high performance of RF MEMS shunt such as high bandwidth, low insertion loss, and high isolation have made these switches well suitable for high performing microwave and millimeter wave circuits. This paper presents a RF MEMS shunt capacitive switch for Ka and V band application. This paper investigates the effect of various geometrical parameters on RF characteristics of the switch. The simulation results are presented and discussed.

Multiple emitter localization using range only measurements considering geometrical constraints

This paper proposes a constrained optimization approach to improve the accuracy of a Time-of-Arrival (ToA) based multiple target localization system. Instead of using an overdetermined measurement system, this paper uses local distance measurements between the targets/emitters as the geometric constraint.Computer simulations are used to evaluate the performance of the geometrically constrained optimization method.

Characterizing compactness of geometrical clusters using fuzzy measures

Certain tasks in image processing require the preservation of fine image details, while applying a broad operation to the image, such as image reduction, filtering, or smoothing. In such cases, the objects of interest are typically represented by small, spatially cohesive clusters of pixels which are to be preserved or removed, depending on the requirements. When images are corrupted by the noise or contain intensity variations generated by imaging sensors, identification of these clusters within the intensity space is problematic as they are corrupted by outliers. This paper presents a novel approach to accounting for spatial organization of the pixels and to measuring the compactness of pixel clusters based on the construction of fuzzy measures with specific properties: monotonicity with respect to the cluster size; invariance with respect to translation, reflection, and rotation; and discrimination between pixel sets of fixed cardinality with different spatial arrangements. We present construction methods based on Sugeno-type fuzzy measures, minimum spanning trees, and fuzzy measure decomposition. We demonstrate their application to generating fuzzy measures on real and artificial images.

Geometrical properties of coupled oscillators at synchronization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

AN INVESTIGATION OF THE ELECTRONIC-STRUCTURE OF THE ANTITUMOR DRUG ELLIPTICINE AND ITS DERIVATIVES .1. GEOMETRICAL AM1 STUDY

Ellipticine and its derivatives are a class of molecules that show antitumor and cytotoxic activity with a multimodal mechanism of action. In this paper we report a preliminary Austin Method One (AM1) study of ellipticine and some molecules derived from it. We have observed a relationship between charge density distribution and biological selectivity. A mechanism that could improve cytotoxic activity is proposed.

Combinatorial and geometrical properties of a class of tilings

In this paper, we consider a tiling generated by a Pisot unit number of degree d >= 3 which has a finite expansible property. We compute the states of a finite automaton which recognizes the boundary of the central tile. We also prove in the case d = 3 that the interior of each tile is simply connected.