188 research outputs found
Numerical investigation of fluid structure interaction between unsteady flow and vibrating liner in a combustion chamber
Numerical investigations of fluid structure interaction between unsteady flow\ud
and vibrating liner in a combustion chamber are undertaken. The computational study consist of two approaches. Firstly, a partioned procedure consists of coupling the LES code AVBP for combustion modelling with the FEM code CaluliX for structural dynamic analysis. The CFD code CFX together with the FEM Ansys package are then used.\ud
Results of unsteady fluid structure interaction applied to combustion system are presented and compare well with experimental results
Comparative metric semantics for concurrent Prolog
AbstractThis paper shows the equivalence of two semantics for a version of Concurrent Prolog with non-flat guards: an operational semantics based on a transition system and a denotational semantics which is a metric semantics (the domains are metric spaces). We do this in the following manner. First a uniform language L is considered, that is a language where the atomic actions have arbitrary interpretations. For this language we define an operational and a denotational semantics, and we prove that the denotational semantics is correct with respect to the operational semantics. This result relies on Banach's fixed point theorem. Techniques stemming from imperative languages are used. Then we show how to translate a Concurrent Prolog program to a program in L by selecting certain basic sets for L and then instantiating the interpretation function for the atomic actions. In this way we induce the two semantics for Concurrent Prolog and the equivalence between the two semantics
The Role of Conformal Symmetry in the Jackiw-Pi Model
The Jackiw-Pi model in 2+1 dimensions is a non-relativistic conformal field
theory of charged particles with point-like self-interaction. For specific
values of the interaction strengths the classical theory possesses vortex and
multi-vortex solutions, which are all degenerate in energy. We compute the full
set of first-order perturbative quantum corrections. Only the coupling constant
g^2 requires renormalization; the fields and electric charge e are not
renormalized. It is shown that in general the conformal symmetries are broken
by an anomalous contribution to the conservation law, proportional to the
beta-function. However, the beta-function vanishes upon restricting the
coupling constants to values g^2 = +/- e^2, which includes the case in which
vortex solutions exist. Therefore the existence of vortices also guarantees the
preservation of the conformal symmetries.Comment: 18 pages, 15 figure
Implications of phosphor coating on the thermal characteristics of phosphor-converted white LEDs
The phosphor layer in phosphor-converted white
Light Emitting Diodes (pcLEDs) affects their optical and thermal
performances. This paper reports the effects of phosphor
thickness and particle concentration on the optical efficiency and
temperature rise on conformal phosphor-coated LED package. It
is observed that a thicker phosphor layer and a higher phosphor
particle concentration will increase the amount of backscattering
and back reflection of light from the phosphor layer. These light
extraction losses not only reduce the optical efficiency of the light
output but also cause heat accumulation in the phosphor layer,
leading to higher LED junction temperature. At 2700 K
correlated colour temperature (CCT), the temperature rise is
observed to increase by as much as 2.6 times as compared to its
blue emitting LED package. However, the self-heating effect can
be reduced through its die-bonding configuration. Structure
function-based thermal evaluation shows heat accumulation in
the phosphor layer and that flip-chip bonding can dissipate the
heat generated in the GaN LED and phosphor layer effectively.
Evidence in this study demonstrates that optical efficiency and
thermal resistance of pcLEDs are dependent on the CCT ratings
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