Thermal Characterization and Lifetime Prediction of LED Boards for SSL Lamp

This work presents a detailed 3-D thermo-mechanical modelling of two LED board technologies to compare their performance. LED board are considered to be used in high power 800 lumen retrofit SSL (Solid State Lighting) lamp. Thermal, mechanical and life time properties are evaluated by numerical modelling. Experimental results measured on fabricated LED board samples are compared to calculated data. Main role of LED board in SSL lamp is to transport heat from LED die to a heat sink and keep the thermal stresses in all layers as low as possible. The work focuses on improving of new LED board thermal management. Moreover, reliability and lifetime of LED board has been inspected by numerical calculation and validated by experiment. Thermally induced stress has been studied for wide temperature range that can affect the LED boards (-40 to +125°C). Numerical modelling of thermal performance, thermal stress distribution and lifetime has been carried out with ANSYS structural analysis where temperature dependent stress-strain material properties have been taken into account. The objective of this study is to improve not only the thermal performance of new LED board, but also identification of potential problems from mechanical fatigue point of view. Accelerated lifetime testing (e.g., mechanical) is carried out in order to study the failure behaviour of current and newly developed LED board

Relativistic Dynamics of Point Magnetic Moment

The covariant motion of a classical point particle with magnetic moment in the presence of (external) electromagnetic fields is revisited. We are interested in understanding Lorentz force extension involving point particle magnetic moment (Stern-Gerlach force) and how the spin precession dynamics is modified for consistency. We introduce spin as a classical particle property inherent to Poincare\'e symmetry of space-time. We propose a covariant formulation of the magnetic force based on a \lq magnetic\rq\ 4-potential and show how the point particle magnetic moment relates to the Amperian (current loop) and Gilbertian (magnetic monopole) description. We show that covariant spin precession lacks a unique form and discuss connection to $g-2$ anomaly. We consider variational action principle and find that a consistent extension of Lorentz force to include magnetic spin force is not straightforward. We look at non-covariant particle dynamics, and present a short introduction to dynamics of (neutral) particles hit by a laser pulse of arbitrary shape.Comment: 11 page

Classical neutral point particle in linearly polarized EM plane wave field

We study a covariant classical model of neutral point particles with magnetic moment interacting with external electromagnetic fields. Classical dynamical equations which reproduce a correct behavior in the non-relativistic limit are introduced. We also discuss the non-uniqueness of the covariant torque equation. The focus of this work is on Dirac neutrino beam control. We present a full analytical solution of the dynamical equations for a neutral point particle motion in the presence of an external linearly polarized EM plane wave (laser) fields. Neutrino beam control using extremely intense laser fields could possibly demonstrate Dirac nature of the neutrino. However, for linearly polarized ideal laser waves we show cancellation of all leading beam control effects.Comment: 9 pages, 2 figure

Design and Fabrication of 3D Electrostatic Energy Harvester

This paper discusses the design of an electrostatic generator, power supply component of the self-powered microsystem, which is able to provide enough energy to power smart sensor chains or if necessary also other electronic monitoring devices. One of the requirements for this analyzer is the mobility, so designing the power supply expects use of an alternative way of getting electricity to power the device, rather than rely on periodic supply of external energy in the form of charging batteries, etc. In this case the most suitable method to use is so-called energy harvesting – a way how to gather energy. This uses the principle of non-electric conversion of energy into electrical energy in the form of converters. The present study describes the topology design of such structures of electrostatic generator. Structure is designed and modeled as a three-dimensional silicon based MEMS. Innovative approach involving the achievement of very low resonant frequency of the structure, while the minimum area of the chip, the ability to work in all 3 axes of coordinate system and ability to be tuned to reach desired parameters proves promising directions of possible further development of this issue. The work includes simulation of electro-mechanical and electrical properties of the structure, description of its behavior in different operating modes and phases of activity. Simulation results were compared with measured values of the produced prototype chip. These results can suggest possible modifications to the proposed structure for further optimization and application environment adaptation

A conjecture of Regev about the Capelli polynomial

AbstractLet X1,…, Xn2, Y1,…, Yn2 be generic n × n matrices over a field k of characteristic zero. If ƒ(X1,…, Xn) is a multilinear invariant of X1,…, Xn then ∑πϱϵSπZ2 (signπ) f(X1Yπ(1),X2Yπ(2)Yπ(3)Yπ(4), X3Yπ(5)…Yπ(9)…XnYπ(n2−2n+2)…Yπ(n2))=f(X1…Xn)Δ(Y), where Sn2 is the symmetric group of degree n2, Δ(Y) is the discriminant of Y1,…, Yn2 and \̂tf(X1,…, Xn) is a uniquely defined multilinear invariant of X1,…, Xn.Thus ƒ → \̂tf defines a function from the vector space of multilinear invariants of X1,…, Xn to itself. An analysis of this function is used to prove Regev's conjecture that ∑πϱϵSπZ2 (signπϱ)Xn(1)Yϱ(1)Xπ(2)Xπ(3)Xπ(4)Yϱ(2)Yϱ(3)Yϱ(4)Xπ(5) … Xπ(n2−2π+2)…Xπ(n2)Yϱ(n2−2n+2)…Yϱ(n2) is nonzero. In addition, a variant of the above function is used to evaluate the Capelli polynomial

Computational investigations of single-chain nanoparticles: novel synthesis routes, complex flow behavior and reversible gel formation.

167 p.Las llamadas nanopartículas unicadena ("single-chain nanoparticles", SCNPs) se obtienen mediante enlazamiento puramente intramolecular de precursores poliméricos. Hay un interés creciente en estos sistemas debido a sus prometedoras aplicaciones en catálisis, biomedicina, sensores, nanocompuestos, etc. El conocimiento de su estructura y dinámica, que controlan en gran parte su respuesta al entorno, es aún escaso. Esta tesis supone un importante avance en dicho conocimiento al investigar tres problemas de interés fundamental y práctico aún inexplorados. Mediante técnicas de simulación computacional se estudia y demuestra: 1) La posibilidad de controlar la topología (en particular la compacidad) de las SCNPs usando anillos como precursores en disoluciones concentradas de anillos inertes (con interacciones puramente estéricas). 2) La respuesta de las SCNPs al flujo de cizalla, cubriendo todo el intervalo desde alta dilución hasta disolución concentrada. Las SCNPs muestran una respuesta independiente de su topología concreta, únicamente ligada a su arquitectura de tipo red polimérica. A diferencia del caso simple de cadenas lineales, la respuesta es diferente a ambos lados de la concentración de solapamiento, este efecto estando ligado a las interacciones topológicas que evitan la concatenación de los anillos presentes en su arquitectura. 3) La competición entre enlaces intra- e intermoleculares en disoluciones de SCNPs con enlaces reversibles, y la obtención de geles reversibles basados en SCNPs, con redes estables altamente dinámicas y evitando la separación de fases a concentraciones de interés.CFM:Materials Physics Cente