Effects of AlN/GaN Superlattices on the Structural Properties of Al0.45Ga0.55N Grown on AlN/Sapphire Templates

Q. M. Fu,T. Peng,Y. Pan,C. Liu 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

Crack-free Al0.45Ga0.55N epilayers with and without AlN/GaN superlattices were grown on AlN/sapphire templates by using radio-frequency-assisted molecular beam epitaxy. The effects of the AlN/GaN superlattices on the structural properties of the Al0.45Ga0.55N epilayers were studied. A reduction of screw dislocations was achieved in Al0.45Ga0.55N epilayers by using AlN/GaN superlattices. Transmission electron microscopy and Raman spectroscopy analyses revealed that the compressive strain of Al0.45Ga0.55N epilayers was effectively relaxed through the inclination of edge threading-dislocations. Crack-free Al0.45Ga0.55N epilayers with and without AlN/GaN superlattices were grown on AlN/sapphire templates by using radio-frequency-assisted molecular beam epitaxy. The effects of the AlN/GaN superlattices on the structural properties of the Al0.45Ga0.55N epilayers were studied. A reduction of screw dislocations was achieved in Al0.45Ga0.55N epilayers by using AlN/GaN superlattices. Transmission electron microscopy and Raman spectroscopy analyses revealed that the compressive strain of Al0.45Ga0.55N epilayers was effectively relaxed through the inclination of edge threading-dislocations.

Strain-Rate Sensitivity of Powder Metallurgy Superalloys Associated With Steady-State DRX During Hot Compression Process

Y. Q. Ning,B. C. Xie,C. Zhou,H. Q. Liang,M. W. Fu 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.2

Strain-rate sensitivity (SRS) is an important parameter to describe the thermodynamic behavior in plasticdeformation process. In this research, the variation of SRS associated with steady-state DRX in P/Msuperalloys was quantitatively investigated. Based on the theoretical analysis and microstructural observationof the alloy after deformation, the SRS coefficient was employed to identify the deformation mechanismof the alloy. Meanwhile, the corresponding relationship between SRS coefficient m, stress exponent nand deformation mechanism was revealed. The stress exponent n in the Arrhenius constitutive model of P/Msuperalloys was calculated. In addition, it is found there is a relatively stable stress exponent range (n = 4-6),indicating that dislocation evolution played as the major hot deformation mechanism for P/M FGH4096superalloy. Furthermore, the Bergstrom model and Senkov model were used and combined together to estimatethe SRS coefficient in the steady-state DRX and the m value maintains at 0.2-0.22, which are consistentwith the microstructural evolution during hot deformation process. The SRS coefficient distribution mapand power dissipation efficiency distribution map were finally constructed associated with the microstructuralevolution during hot deformation, which can be used to optimize the processing parameters of thesuperalloys.

Wind effects on a large cantilevered flat roof: loading characteristics and strategy of reduction

Fu, J.Y.,Li, Q.S.,Xie, Z.N. Techno-Press 2005 Wind and Structures, An International Journal (WAS Vol.8 No.5

Mean and extreme pressure distributions on a large cantilevered flat roof model are measured in a boundary layer wind tunnel. The largest peak suction values are observed from pressure taps beneath conical "delta-wing type" corner vortices that occur for oblique winds, then the characteristics and causes of the local peak suctions are discussed in detail. Power spectra of fluctuating wind pressures measured from some typical taps located at the roof edges under different wind directions are presented, and coherence functions of fluctuating pressures are also obtained. Based on these results, it is verified that the peak suctions are highly correlated with the conical vortices. Furthermore, according to the characteristics of wind loads on the roof, an aerodynamic solution to minimize the peak suctions by venting the leading edges and the corners of the roof is recommended. The experimental results show that the suggested strategy can effectively control the generation of the conical vortices and make a reduction of 50% in mean pressures and 25% in extreme local pressures at wind sensitive locations on the roof.

Tetranitrophthalocyanine Zinc/TiO2 Nanofibers Organic–Inorganic Heterostructures with Enhanced Visible Photocatalytic Activity

Q. Zhang,S. Zhou,S. F. Fu,X. Z. Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.10

"2,9,16,23-tetranitrophthalocyanine zinc (TNZnPc)/TiO2 organic–inorganic heterostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. These photocatalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV–Vis, energy dispersive X-ray and X-ray photoelectron spectroscopy. The photocatalytic studies revealed that the TNZnPc/TiO2 organic–inorganic heterostructures exhibited enhanced photocatalytic efficiency of photo-degradation of rhodamine B compared with pure TiO2 nanofibers under visible-light irradiation. Further studies indicate that the photosynergistic effect of organic–inorganic heterostructures can remarkably enhance the photoinduced interfacial charge transfer, thereby increasing the charge separation during the photocatalytic reaction."

Synthesis and spectral properties of nanocrystalline Eu³⁺-doped pyrochlore oxide M₂Sn₂O₇ (M = Gd and Y)

Fu, Z.,Gong, W.,Li, H.,Wu, Q.,Li, W.,Yang, H.K.,Jeong, J.H. Elsevier 2011 CURRENT APPLIED PHYSICS Vol.11 No.3

Nanocrystalline Eu<SUP>3+</SUP>-doped pyrochlore oxide M<SUB>2</SUB>Sn<SUB>2</SUB>O<SUB>7</SUB> (M = Gd and Y) has been successfully prepared by a simple and facile hydrothermal synthesis method without the presence of catalysts. The effects of hydrothermal temperature, time and base concentration on the pure phase of the products are investigated. It is found that tuning the base concentration was a crucial step for the control of the pure phase of the M<SUB>2</SUB>Sn<SUB>2</SUB>O<SUB>7</SUB> (M = Gd and Y) nanocrystals. All the products were systematically characterized by powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-Transform Infrared Spectroscopy (FT-IR), photoluminescence (PL) and photoluminescent excitation spectra (PLE). Furthermore, the luminescence mechanism and size dependence of their spectral properties are also discussed in detail.

Closed-form symbol error rate expression of decode-and-forward relaying using orthogonal space-time block coding

Yang, Q.,Kwak, K.S.,Fu, F. IET 2010 IET COMMUNICATIONS Vol.4 No.3

<P>The authors investigate the symbol error rate (SER) performance of the cooperative decode-and-forward (DF) relaying strategy with orthogonal space-time block coding (OSTBC) applied at all links of source-relay, source-destination and relay-destination. Only when one relay node is able to correctly decode the OSTBC codeword of the source, it will forward source information to the destination with the same OSTBC codeword. The exact SER expressions of DF relaying with OSTBC are presented for M-PSK and M-QAM modulations, respectively, over dissimilar Rayleigh fading channels. By virtue of the multinomial theorem and the law of total probability, the derived expressions are further deduced in closed form. Simulations demonstrate the proposed closed-form analytical results. It is pointed out that such results have seldom appeared in literatures before.</P>

The Synthesis and Spectral Properties of Some New Monomethine Cyanine Dyes for Live Cell Imaging

Y. L. Fu,Y. Z. Zhou,G. Zhang,Q. C. Yang,X. Zhai,L. Y. Wang 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.2

Four monomethine cyanine dyes were synthesized and their structures were confirmed by 1H NMR, IR, UV–Vis, and HRMS. Their spectral properties were studied. It could be found that the λmax of the dyes was shorter in the protonic solvents compared with that in the non-protonic solvents. Moreover, the λmax shows a hypsochromic shift with the increasing polarity of the solvents. The interactions of four dyes with DNA were also studied. The results showed that the fluorescence intensities of the dyes 3a and 3b took place a qualitative change in the presence of DNA compared with the free dyes. The dyes used as cellular imaging agents were researched. The results indicated that the dye 3b could penetrate the live cell membrane.

Sex-specific association of X-linked Toll-like receptor 7 (TLR7) with male systemic lupus erythematosus

Shen, N.,Fu, Q.,Deng, Y.,Qian, X.,Zhao, J.,Kaufman, K.M.,Wu, Y.L.,Yu, C.Y.,Tang, Y.,Chen, J.-Y. National Academy of Sciences 2010 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.107 No.36

Large eddy simulation of wind loads on a long-span spatial lattice roof

Chao Li,Q.S. Li,S.H. Huang,J.Y. Fu,Y.Q. Xiao 한국풍공학회 2010 Wind and Structures, An International Journal (WAS Vol.13 No.1

The 486m-long roof of Shenzhen Citizens Centre is one of the world’s longest spatial lattice roof structures. A comprehensive numerical study of wind effects on the long-span structure is presented in this paper. The discretizing and synthesizing of random flow generation technique (DSRFG) recently proposed by two of the authors (Huang and Li 2008) was adopted to produce a spatially correlated turbulent inflow field for the simulation study. The distributions and characteristics of wind loads on the roof were numerically evaluated by Computational Fluid Dynamics (CFD) methods, in which Large Eddy Simulation (LES) and Reynolds Averaged Navier-Stokes Equations (RANS) Model were employed. The main objective of this study is to explore a useful approach for estimations of wind effects on complex curved roof by CFD techniques. In parallel with the numerical investigation, simultaneous pressure measurements on the entire roof were made in a boundary layer wind tunnel to determine mean, fluctuating and peak pressure coefficient distributions, and spectra, spatial correlation coefficients and probability characteristics of pressure fluctuations. Numerical results were then compared with these experimentally determined data for validating the numerical methods. The comparative study demonstrated that the LES integrated with the DSRFG technique could provide satisfactory prediction of wind effects on the long-span roof with complex shape, especially on separation zones along leading eaves where the worst negative wind-induced pressures commonly occur. The recommended LES and inflow turbulence generation technique as well as associated numerical treatments are useful for structural engineers to assess wind effects on a long-span roof at its design stage.

Deposition of ZnO thin films on GaN substrates

T. Peng,Q. M. Fu,C. Liu 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.-

ZnO thin films were deposited by electron-beam evaporation on undoped GaN and p-GaN substrates, which were grown by radio-frequency assisted molecular-beam epitaxy. It has been found that rotation of the substrate during deposition has a crucial effect on the morphology and microstructure that can be varied from nanorod growth to two-dimensional ZnO thin film growth when the substrate is changed from stationary to rotatory. Under optimized growth conditions, the morphologies of ZnO thin films are similar to those of GaN substrates. ZnO thin films were deposited by electron-beam evaporation on undoped GaN and p-GaN substrates, which were grown by radio-frequency assisted molecular-beam epitaxy. It has been found that rotation of the substrate during deposition has a crucial effect on the morphology and microstructure that can be varied from nanorod growth to two-dimensional ZnO thin film growth when the substrate is changed from stationary to rotatory. Under optimized growth conditions, the morphologies of ZnO thin films are similar to those of GaN substrates.