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result(s) for
"Black body"
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The Cambridge companion to the Black body in American literature
\"This volume tracks and uncovers the Black body as a persistent presence and absence in American literature. It provides an invaluable guide for teachers and students interested in literary representations of Blackness and embodiment. It centers Black thinking about Black embodiment from current, diverse, and intersectional perspectives\"-- Provided by publisher.
Book
Overcoming black body radiation limit in free space: metamaterial superemitter
Here, we demonstrate that the power spectral density of thermal radiation at a specific wavelength produced by a body of finite dimensions set up in free space under a fixed temperature could be made theoretically arbitrary high, if one could realize double negative metamaterials with arbitrary small loss and arbitrary high absolute values of permittivity and permeability (at a given frequency). This result refutes the widespread belief that Planck's law itself sets a hard upper limit on the spectral density of power emitted by a finite macroscopic body whose size is much greater than the wavelength. Here we propose a physical realization of a metamaterial emitter whose spectral emissivity can be greater than that of the ideal black body under the same conditions. Due to the reciprocity between the heat emission and absorption processes such cooled down superemitter also acts as an optimal sink for the thermal radiation-the 'thermal black hole'-which outperforms Kirchhoff-Planck's black body which can absorb only the rays directly incident on its surface. The results may open a possibility to realize narrowband super-Planckian thermal radiators and absorbers for future thermo-photovoltaic systems and other devices.
Journal Article
Token Black girl : a memoir
\"Token Black Girl unpacks the adverse effects of insidious white supremacy in the media--both unconscious and strategic--to tell a personal story about recovery from damaging concepts of perfection, celebrating identity, and demolishing social conditioning\"--Book jacket flap.
Book
Generation Mechanism for the Far-Infrared Emission Between Rydberg States of NO
We report generation of directional far-infrared emission between Rydberg states of NO in the gas phase initiated by the absorption of black body radiation at room temperature. All the transitions detected are assignable to the
nf
→ (
n
− 1)
g
and
n′g
→ (
n′
− 1)
f
transitions. The longest wavelength observed in the present experiment was ~ 112 µm (2.7 THz) which corresponds to the 14
f
→ 13
g
transition. The laser-prepared population in the 14
s
and 15
s
states is transferred to the 13
f
and 14
f
states located energetically higher, respectively, which generates the subsequent emission of 13
f
→ 12
g
at ~ 88 µm and 14
f
→ 13
g
at ~ 112 µm. Collisions of Rydberg molecules with the surrounding ground state molecules are considered to responsible for the upward population flow. The population in the 14
p
and 15
p
states is transported to the 13
f
and 14
f
states located energetically lower, respectively, which gives rise to the subsequent emission of 13
f
→ 12
g
at ~ 88 µm and 14
f
→ 13
g
at ~ 112 µm.
Graphical abstract
Journal Article
Impact of Black Body Material Enhanced Gas Movement on CO2 Photocatalytic Reduction Performance
Gas movement around and/or through the photocatalyst is thought to be an inhibition factor to promote photocatalytic CO2 reduction performance. In this study, a hypothesis is put forward that the natural thermosiphon movement of gases around the photocatalyst can be improved by using black body material/surface. The black body material/surface that is placed underneath the photocatalyst in the reactor would be heated by absorbing light and then this heats up the gases to promote their movement around/through the photocatalyst. The aim of this study is to prove or disprove this hypothesis by conducting CO2 reduction performance of a TiO2 photocatalyst with NH3 under the conditions without black body material (W/O B.B.), with one black body material (W B.B.-1), and with three black body materials (W B.B.-3). The impact of molar ratio of CO2/NH3 on CO2 reduction performance is also investigated. This study revealed/proved that the hypothesis worked and that the CO2 reduction performance is promoted more with W B.B.-3 compared to that with W B.B.-1. The maximum concentration of formed CO with W B.B.-3 is two to five times as large as that under the condition W/O B.B.
Journal Article
Observation of stationary spontaneous Hawking radiation and the time evolution of an analogue black hole
The emission of Hawking radiation from a black hole was predicted to be stationary, which is necessary for the correspondence between Hawking radiation and blackbody radiation. Spontaneous Hawking radiation was observed in analogue black holes in atomic Bose–Einstein condensates, although the stationarity was not probed. Here we confirm that the spontaneous Hawking radiation is stationary by observing such a system at six different times. Furthermore, we follow the time evolution of Hawking radiation and compare and contrast it with predictions for real black holes. We observe the ramp-up of Hawking radiation followed by stationary spontaneous emission, similar to a real black hole. The end of the spontaneous Hawking radiation is marked by the formation of an inner horizon, which is seen to cause stimulated Hawking radiation, as predicted. We find that the stimulated Hawking and partner particles are directly observable, and that the stimulated emission evolves from multi-mode to monochromatic. Numerical simulations suggest that Bogoliubov–Cherenkov–Landau stimulation predominates, rather than black-hole lasing.In an analogue black hole in an atomic Bose–Einstein condensate, spontaneous Hawking radiation is confirmed to be stationary and the time evolution of Hawking radiation is reported.
Journal Article
Dulong-Petit’s law and Boltzmann’s theoretical proof from the Kinetic Theory of Gases
The main aspect that we will address in this work is the introductory presentation of the empirical law of the specific heats of material bodies, published by Dulong and Petit on April 12, 1819, in the magazine Comptes Rendus. The analytical demonstration of this law appeared for the first time in 1866 in the Doctoral Thesis of the Austrian physicist Ludwig Boltzmann, according to the research carried out by Cássio C. Laranjeiras and presented in his Doctoral Thesis in 2002. In the introduction we discussed how Dulong’s law and Petit played a key role in the subsequent development of a new physics (Quantum Mechanics), when Max Planck changed his research program from electrodynamics to thermodynamics, evidenced in the book: Black Body Theory and the Quantum Discontinuity, 1894-1912, published by Thomas Khun in 1978. Between 1900 and 1912, we observed that fundamental works published by Albert Einstein, Henri Poincaré and Peter Debye explained the mathematical relationship of this empirical law based on Planck’s hypothesis of the quantum of action of blackbody radiation. Despite the controversy over the authorship of the law, whether it would have been formulated in advance by Arago, we agree with Robert Fox that it was the results of Dulong and Petit’s experiments that led to the formulation of the law.
Journal Article
Synergistic-potential engineering enables high-efficiency graphene photodetectors for near- to mid-infrared light
High quantum efficiency and wide-band detection capability are the major thrusts of infrared sensing technology. However, bulk materials with high efficiency have consistently encountered challenges in integration and operational complexity. Meanwhile, two-dimensional (2D) semimetal materials with unique zero-bandgap structures are constrained by the bottleneck of intrinsic quantum efficiency. Here, we report a near-mid infrared ultra-miniaturized graphene photodetector with configurable 2D potential well. The 2D potential well constructed by dielectric structures can spatially (laterally and vertically) produce a strong trapping force on the photogenerated carriers in graphene and inhibit their recombination, thereby improving the external quantum efficiency (EQE) and photogain of the device with wavelength-immunity, which enable a high responsivity of 0.2 A/W–38 A/W across a broad infrared detection band from 1.55 to 11 µm. Thereafter, a room-temperature detectivity approaching 1 × 10
9
cm Hz
1/2
W
−1
is obtained under blackbody radiation. Furthermore, a synergistic effect of electric and light field in the 2D potential well enables high-efficiency polarization-sensitive detection at tunable wavelengths. Our strategy opens up alternative possibilities for easy fabrication, high-performance and multifunctional infrared photodetectors.
The integration of 2D materials with metasurfaces can enhance their quantum efficiency, but the approach is usually limited to a narrow spectral band. Here, the authors report the realization of gate-tunable graphene photodetectors combined with all-dielectric periodic slits, leading to enhanced photoresponse in the short-to-long-wave infrared.
Journal Article
Incandescent temporal metamaterials
Regarded as a promising alternative to spatially shaping matter, time-varying media can be seized to control and manipulate wave phenomena, including thermal radiation. Here, based upon the framework of macroscopic quantum electrodynamics, we elaborate a comprehensive quantum theoretical formulation that lies the basis for investigating thermal emission effects in time-modulated media. Our theory unveils unique physical features brought about by time-varying media: nontrivial correlations between fluctuating electromagnetic currents at different frequencies and positions, thermal radiation overcoming the black-body spectrum, and quantum vacuum amplification effects at finite temperature. We illustrate how these features lead to striking phenomena and innovative thermal emitters, specifically, showing that the time-modulation releases strong field fluctuations confined within epsilon-near-zero (ENZ) bodies, and that, in turn, it enables a narrowband (partially coherent) emission spanning the whole range of wavevectors, from near to far-field regimes.
Here the authors employ quantum electrodynamics to formulate thermal emission effects in time-modulated media, resulting in innovative thermal emitters. They show that time modulation induces strong field fluctuations in epsilon-near-zero bodies, enabling narrowband emission across the entire range of wavevectors, from near to far-field regimes.
Journal Article