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91.
Sharp leading edges with a millimeter-scale radius are required for hypersonic vehicles from aerodynamic reasons. However, with the leading edges being so sharp, stagnation regions at wing and tail leading edges suffer a hostile thermal environment. Therefore, a high-temperature heat pipe is considered to be integrated into the structure of the leading edge to reduce the temperature of the stagnation point. In this paper, a superalloy-refractory composite-container-“wall” combined with the wick and working fluid structure is proposed, which is proved to be a feasible design of a heat pipe for the semi-passive thermal protection system (TPS). The effects of different material of the exterior surface on the temperature distributions are investigated. The effect of the half wedge angle, the design length and porosity of the wick is also investigated to find the effect of the geometry of the structure of the leading edge on the operation of the heat pipe. 相似文献
92.
Zhao JF Ou HW Wu G Xie BP Zhang Y Shen DW Wei J Yang LX Dong JK Arita M Namatame H Taniguchi M Chen XH Feng DL 《Physical review letters》2007,99(14):146401
The electronic structure of a new charge-density-wave system or superconductor, 1T-Cu(x)TiSe(2), has been studied by photoemission spectroscopy. A correlated semiconductor band structure is revealed for the undoped case, which resolves a long-standing controversy in the system. With Cu doping, the charge-density wave is suppressed by the raising of the chemical potential, while the superconductivity is enhanced by the enhancement of the density of states, and possibly suppressed at higher doping by the strong scattering. 相似文献
93.
In this review article, we describe turbulence control in excitable systems by using a local periodic pacing method. The controllability conditions of turbulence suppression and the mechanisms underlying these conditions are analyzed. The local pacing method is applied to control Winfree turbulence (WT) and defect turbulence (DT) induced by spiral-wave breakup. It is shown that WT can always be suppressed by local pacing if the pacing amplitude and frequency are properly chosen. On the other hand, the pacing method can achieve suppression of DT induced by instabilities associated with the motions of spiral tips while failing to suppress DT induced by the instabilities of wave propagation far from tips. In the latter case, an auxiliary method of applying gradient field is suggested to improve the control effects. The implication of this local pacing method to realistic cardiac defibrillation is addressed. 相似文献
94.
We present the design and experimental characterization of a monolithic optical time-division multiplexer (MUX) for 160 Gbit/s operation based on periodically poled lithium niobate (PPLN) waveguides. Its key figures of merit agree well with theoretical predictions and meet or exceed those of a previously demonstrated PPLN-planar-light-wave-circuit hybrid MUX. The monolithic design has a simpler layout and higher efficiency while keeping the cross talk low. 相似文献
95.
Photonic generation of a millimeter-wave signal based on sextuple-frequency multiplication 总被引:2,自引:0,他引:2
A millimeter-wave signal with sextuple-frequency multiplication of a microwave source is obtained with two cascaded optical modulators, which are driven by the same microwave source with phase deviation of pi/2 introduced by an electrical phase shifter. Without any optical filter, a wideband continuously tunable millimeter-wave signal is easily generated. 相似文献
96.
97.
Some novel cycloaddition reactions based on benzyne and olefins have been developed.These reactions were performed in the absence of a transition metal catalyst,and they displayed good yields.These cycloaddition reactions of benzyne with olefins provide effective routes for synthesizing benzocyclobutenes,biaryl compounds and 9,10-dihydrophenanthrene derivatives. 相似文献
98.
Dr. Lu Jin Fangyuan Cheng Hao Li Prof. Dr. Kui Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8976-8980
Porous tantalum nitride (Ta3N5) single crystals, combining structural coherence and porous microstructure, would substantially improve the photoelectrochemical performance. The structural coherence would reduce the recombination of charge carriers and maintain excellent transport properties while the porous microstructure would not only reduce photon scattering but also facilitate surface reactions. Here, we grow bulk-porous Ta3N5 single crystals on a two-centimeter scale with (002), (023), and (041) facets, respectively, and show significantly enhanced photoelectrochemical performance. We show the preferential facet growth of porous crystals in a lattice reconstruction strategy in relation to lattice match and lattice channel. We present the facet engineering to enhance light absorption, exciton lifetime and transport properties. The porous Ta3N5 single crystal boosts photoelectrochemical oxidation of alcohols with the (002) facet showing the highest performance of >99 % alcohol conversion and >99 % aldehyde/ketone selectivity. 相似文献
99.
Meng Zhao Dr. Hong-Jie Peng Bo-Quan Li Dr. Xiao Chen Jin Xie Dr. Xinyan Liu Prof. Qiang Zhang Prof. Jia-Qi Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9096-9102
In situ evolution of electrocatalysts is of paramount importance in defining catalytic reactions. Catalysts for aprotic electrochemistry such as lithium–sulfur (Li-S) batteries are the cornerstone to enhance intrinsically sluggish reaction kinetics but the true active phases are often controversial. Herein, we reveal the electrochemical phase evolution of metal-based pre-catalysts (Co4N) in working Li-S batteries that renders highly active electrocatalysts (CoSx). Electrochemical cycling induces the transformation from single-crystalline Co4N to polycrystalline CoSx that are rich in active sites. This transformation propels all-phase polysulfide-involving reactions. Consequently, Co4N enables stable operation of high-rate (10 C, 16.7 mA cm−2) and electrolyte-starved (4.7 μL mgS−1) Li-S batteries. The general concept of electrochemically induced sulfurization is verified by thermodynamic energetics for most of low-valence metal compounds. 相似文献
100.
Dr. Yong Wang Yajun Zhao Shuaishuai Zhu Prof. Dr. Xingping Zhou Prof. Dr. Jing Xu Prof. Dr. Xiaolin Xie Prof. Dr. Rinaldo Poli 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(15):6044-6050
A strategy that uses carbon monoxide (CO) as a molecular trigger to switch the polymerization mechanism of a cobalt Salen complex [salen=(R,R)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine] from ring-opening copolymerization (ROCOP) of epoxides/anhydrides to organometallic mediated controlled radical polymerization (OMRP) of acrylates is described. The key phenomenon is a rapid and quantitative insertion of CO into the Co−O bond, allowing for in situ transformation of the ROCOP active species (Salen)CoIII-OR into the OMRP photoinitiator (Salen)CoIII-CO2R. The proposed mechanism, which involves CO coordination to (Salen)CoIII-OR and subsequent intramolecular rearrangement via migratory insertion has been rationalized by DFT calculations. Regulated by both CO and visible light, on-demand sequence control can be achieved for the one-pot synthesis of polyester-b-polyacrylate diblock copolymers (Đ<1.15). 相似文献