467,956 research outputs found
Engineering the accurate distortion of an object's temperature-distribution signature
It is up to now a challenge to control the conduction of heat. Here we
develop a method to distort the temperature distribution signature of an object
at will. As a result, the object accurately exhibits the same temperature
distribution signature as another object that is predetermined, but actually
does not exist in the system. Our finite element simulations confirm the
desired effect for different objects with various geometries and compositions.
The underlying mechanism lies in the effects of thermal metamaterials designed
by using this method. Our work is of value for applications in thermal
engineering.Comment: 11 pages, 4 figure
Possible huge enhancement in the radiative decay of the weal W boson into the charmed meson
We point out that the rare decay mode could be spectacularly enhanced, with a branching ratio around
which is three order of magnitude larger than previous predictions.
Its observation will determine the W boson mass with great accuracy, providing
additional high precision tests of the standard model, as well as reveal
eventual deviation from the trilinear non-abelian gauge coupling.Comment: 14, PAR/LPTHE 93 - 0
Symmetric Real Dirac Fermions and Semimetals
Recently Weyl fermions have attracted increasing interest in condensed matter
physics due to their rich phenomenology originated from their nontrivial
monopole charges. Here we present a theory of real Dirac points that can be
understood as real monopoles in momentum space, serving as a real
generalization of Weyl fermions with the reality being endowed by the
symmetry. The real counterparts of topological features of Weyl semimetals,
such as Nielsen-Ninomiya no-go theorem, D sub topological insulators and
Fermi arcs, are studied in the symmetric Dirac semimetals, and the
underlying reality-dependent topological structures are discussed. In
particular, we construct a minimal model of the real Dirac semimetals based on
recently proposed cold atom experiments and quantum materials about
symmetric Dirac nodal line semimetals.Comment: 7.5 pages, 5 figures. Accepted by Phys. Rev. Let
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High-Order Dual-Port Quasi-Absorptive Microstrip Coupled-Line Bandpass Filters
In this article, we present the first demonstration of distributed and symmetrical all-band quasi-absorptive filters that can be designed to arbitrarily high orders. The proposed quasi-absorptive filter consists of a bandpass section (reflective-type coupled-line filter) and absorptive sections (a matched resistor in series with a shorted quarter-wavelength transmission line). Through a detailed analysis, we show that the absorptive sections not only eliminate out-of-band reflections but also determine the passband bandwidth (BW). As such, the bandpass section mainly determines the out-of-band roll-off and the order of the filter can be arbitrarily increased without affecting the filter BW by cascading more bandpass sections. A set of 2.45-GHz one-, two-, and three-pole quasi-absorptive microstrip bandpass filters are designed and measured. The filters show simultaneous input and output absorption across both the passband and the stopband. Measurement results agree very well with the simulation and validate the proposed design concept
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