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951.
《Mathematical Methods in the Applied Sciences》2018,41(8):2939-2960
In this paper, we consider a rotating Euler‐Bernoulli beam. The beam is made of a viscoelastic material, and it is subject to undesirable vibrations. Under a suitable control torque applied at the motor, we prove the arbitrary stabilization of the system for a large class of relaxation functions by using the multiplier method and some ideas introduced by Tatar (J. Math. Phys. 52:013502, 2011). 相似文献
952.
《Particuology》2015
Anti-wear beams installed on water walls of circulating fluidized bed (CFB) boilers are one of the most effective ways to protect against water-wall erosion. Beam effects from, for example, beam size and superficial gas velocity were investigated on gas–solid hydrodynamics in a CFB test rig using CFD simulations and experimental methods. The downward flow of the wall layer solids is observed to be disrupted by the beam but is then restored some distance further downstream. When falling solids from the wall layer hit the anti-wear beam, the velocity of the falling solids decreases rapidly. A fraction of the solids accumulates on the beam. Below the beams, the falling solids have reduced velocities but upward-moving solids were observed on the wall. The effect of the beam increases with width and superficial gas velocity. Wear occurs mainly above the beam and its variation with width is different above to below the beam. There is an optimum width that, when combined with beam height, results in less erosion. 相似文献
953.
S. Marlafeka N. Bock T. S. Cheng S. V. Novikov A. J. Winser I. Harrison C. T. Foxon P. D. Brown 《Journal of Crystal Growth》2001,230(3-4):415-420
The epitaxial growth of GaN layers on sapphire substrates by molecular beam epitaxy at low temperatures (500°C) has been investigated. Samples exhibited a transition from hexagonal to mixed hexagonal/cubic phase under conditions of increasing Ga flux as determined using a TEM-RHEED technique with complementary SEM and PL observations. Embedded cubic grains adopted two domain variants with additional evidence for twinning. 相似文献
954.
S.D. Wu L.W. Guo W.X. Wang Z.H. Li X.Z. Shang H.Y. Hu Q. Huang J.M. Zhou 《Journal of Crystal Growth》2004,270(3-4):359-363
GaAsSb ternary epitaxial layers were grown on GaAs (0 0 1) substrate in various Sb4/As2 flux ratios by solid source molecular beam epitaxy. The alloy compositions of GaAs1−ySby were inferred using high-resolution X-ray symmetric (0 0 4) and asymmetric (2 2 4) glance exit diffraction. The non-equilibrium thermodynamic model is used to explain the different incorporation behavior between the Sb4 and As2 under the assumption that one incident Sb4 molecule produces one active Sb2 molecule. It is inferred that the activation energy of Sb4 dissociation is about 0.46 eV. The calculated results for the incorporation efficiency of group V are in good agreement with the experimental data. 相似文献
955.
956.
Xiu-Qi Huang Feng-Qi Liu Xiao-Ling Che Jun-Qi Liu Wen Lei Zhan-Guo Wang 《Journal of Crystal Growth》2004,270(3-4):364-369
Self-assembled InAs quantum dots (QDs) in an InAlGaAs matrix, lattice-matched to InP substrate, have been grown by molecular beam epitaxy (MBE). Transmission electron microscopy (TEM), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL) are used to study their structural and optical properties. In InAs/InAlGaAs/InP system, we propose that when the thickness of InAs layer deposited is small, the random strain distribution of the matrix layer results in the formation of tadpole-shaped QDs with tails towards random directions, while the QDs begin to turn into dome-shaped and then coalesce to form islands with larger size and lower density to release the increasing misfit strain with the continuous deposition of InAs. XRD rocking curves showing the reduced strain with increasing thickness of InAs layer may also support our notion. The results of PL measurements are in well agreement with that of TEM images. 相似文献
957.
Ho Jin Park Jong Ho Kim J.J. Yoon J.S. Son D.Y. Lee H.H. Ryu Minhyon Jeon J.Y. Leem 《Journal of Crystal Growth》2007,300(2):319-323
The effects of multi-step rapid thermal annealing (RTA) for the self-assembled InAs quantum dots (QDs), which were grown by a molecular beam epitaxy (MBE), were investigated through photoluminescence (PL) and transmission electron microscopy (TEM). Postgrowth multi-step RTA was used to modify the structural and optical properties of the self-assembled InAs QDs. Postgrowth multi-step RTAs are as follows: one step (20 s at 750 °C); two step (20 s at 650 °C, 20 s at 750 °C); three step (30 s at 450 °C, 20 s at 650 °C, 20 s at 750 °C). It is found that significant narrowing of the luminescence linewidth (from 132 to 31 meV) from the InAs QDs occurs together with about 150 meV blueshift by two-step annealing, compared to as-grown InAs QDs. Observation of transmission electron microscopy (TEM) shows the existence of the dots under one- and two-step annealing but the disappearance of the dots by three-step annealing. Comparing with the samples under only one-step annealing, we demonstrate a significant enhancement of the interdiffusion in the dot layer under multi-step annealing. 相似文献
958.
E.M. Jackson G.I. Boishin E.H. Aifer B.R. Bennett L.J. Whitman 《Journal of Crystal Growth》2004,270(3-4):301-308
We have investigated the cross-contamination of As in GaSb/InAs superlattices. We demonstrate a method of varying the lattice constant of the superlattice. By controlling the As background pressure in the growth chamber, the strain can be controlled to about 0.01%, corresponding to As cross-incorporation variations of about ±1%. The distribution of As is investigated by X-ray diffraction and cross-sectional scanning tunneling microscopy, and the critical thickness is obtained. 相似文献
959.
J. He B. Xu Z. G. Wang S. C. Qu F. Q. Liu T. W. Zhu X. L. Ye F. A. Zhao X. Q. Meng 《Journal of Crystal Growth》2002,240(3-4):395-400
A high density of 1.02×1011 cm−2 of InAs islands with In0.15Ga0.85As underlying layer has been achieved on GaAs (1 0 0) substrate by solid source molecular beam epitaxy. Atomic force microscopy and PL spectra show the size evolution of InAs islands. A 1.3 μm photoluminescence (PL) from InAs islands with In0.15Ga0.85As underlying layer and InGaAs strain-reduced layer has been obtained. Our results provide important information for optimizing the epitaxial structures of 1.3 μm wavelength quantum dots devices. 相似文献
960.
《Progress in Surface Science》2023,98(2):100704
Borophene, a two-dimensional (2D) planar boron sheet, has attracted dramatic attention for its unique physical properties that are theoretically predicted to be different from those of bulk boron, such as polymorphism, superconductivity, Dirac fermions, mechanical flexibility and anisotropic metallicity. Nevertheless, it has long been difficult to obtain borophene experimentally due to its susceptibility to oxidation and the strong covalent bonds in bulk forms. With the development of growth technology in ultra-high vacuum (UHV), borophene has been successfully synthesized by molecular beam epitaxy (MBE) supported by substrates in recent years. Due to the intrinsic polymorphism of borophene, the choice of substrates in the synthesis of borophene is pivotal to the atomic structure of borophene. The different interactions and commensuration of borophene on various substrates can induce various allotropes of borophene with distinct atomic structures, which suggests a potential approach to explore and manipulate the structure of borophene and benefits the realization of novel physical and chemical properties in borophene due to the structure–property correspondence. In this review, we summarize the recent research progress in the synthesis of monolayer (ML) borophene on various substrates, including Ag(1 1 1), Ag(1 1 0), Ag(1 0 0), Cu(1 1 1), Cu(1 0 0), Au(1 1 1), Al(1 1 1) and Ir(1 1 1), in which the polymorphism of borophene is present. Moreover, we introduce the realization of bilayer (BL) borophene on Ag(1 1 1), Cu(1 1 1) and Ru(0 0 0 1) surfaces, which possess richer electronic properties, including better thermal stability and oxidation resistance. Then, the stabilization mechanism of polymorphic borophene on their substrates is discussed. In addition, experimental investigations on the unique physical properties of borophene are also introduced, including metallicity, topology, superconductivity, optical and mechanical properties. Finally, we present an outlook on the challenges and prospects for the synthesis and potential applications of borophene. 相似文献