scholarly journals Active thermal cloaking and mimicking

Author(s):  
Maxence Cassier ◽  
Trent DeGiovanni ◽  
Sébastien Guenneau ◽  
Fernando Guevara Vasquez

We present an active cloaking method for the parabolic heat (and mass or light diffusion) equation that can hide both objects and sources. By active, we mean that it relies on designing monopole and dipole heat source distributions on the boundary of the region to be cloaked. The same technique can be used to make a source or an object look like a different one to an observer outside the cloaked region, from the perspective of thermal measurements. Our results assume a homogeneous isotropic bulk medium and require knowledge of the source to cloak or mimic, but are in most cases independent of the object to cloak.

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1860 ◽  
Author(s):  
Anton Alexeev ◽  
Grigory Onushkin ◽  
Jean-Paul Linnartz ◽  
Genevieve Martin

Thermal transient testing is widely used for LED characterization, derivation of compact models, and calibration of 3D finite element models. The traditional analysis of transient thermal measurements yields a thermal model for a single heat source. However, it appears that secondary heat sources are typically present in LED packages and significantly limit the model’s precision. In this paper, we reveal inaccuracies of thermal transient measurements interpretation associated with the secondary heat sources related to the light trapped in an optical encapsulant and phosphor light conversion losses. We show that both have a significant impact on the transient response for mid-power LED packages. We present a novel methodology of a derivation and calibration of thermal models for LEDs with multiple heat sources. It can be applied not only to monochromatic LEDs but particularly also to LEDs with phosphor light conversion. The methodology enables a separate characterization of the primary pn junction thermal power source and the secondary heat sources in an LED package.


1962 ◽  
Vol 84 (4) ◽  
pp. 312-316 ◽  
Author(s):  
S. A. Hovanessian

Analytical and finite difference solutions are developed for the temperature distribution in a medium of rectangular cross section having uniform properties and either constant temperature or insulated boundaries and with a line heat source of constant strength perpendicular to the section. The analytical solutions are infinite series which converge rapidly except at the source location where they diverge to infinity. The finite difference solutions are given in closed form. The temperature values obtained from the latter are compared to those of the former and the effect of time step and space increments on the finite difference solutions studied.


2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Xiao-Mei Yang ◽  
Zhi-Liang Deng

An inverse source identification problem for a time fractional diffusion equation is discussed. The unknown heat source is supposed to be space dependent only. Based on the use of Green’s function, an effective numerical algorithm is developed to recover both the intensities and locations of unknown point sources from final measurements. Numerical results indicate that the proposed method is efficient and accurate.


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