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Secondary instability of separated shear layers

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Chinese Journal of Aeronautics 2019年第1期32卷 37-44页

作者： Zhiyin YANG Department of Mechanical Engineering and the Built Environment College of Engineering and TechnologyUniversity of Derby

The process through which a laminar flow undergoes transition to turbulence is of great fundamental and practical interest. Such a process is hugely complex as there are many diverse routes for a laminar flow to become turbulent flow. The transition process is usually initiated by flow instabilities—a primary instability stage followed by a secondary instability stage. This forms a rational framework for the early stage of a transition process and it is crucially important to understand the physics of instabilities leading to turbulence. This article reviews the results of studies on secondary instability of separated shear layers in separation bubbles and summaries the current status of our understanding in this area.

关键词： Primary instability Secondary instability Separated shear layers Separation bubbles Transition

Effects of surface shapes on properties of turbulent/non-turbulent interface in turbulent boundary layers

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Science China(Technological Sciences) 2020年第2期63卷 214-222页

作者： WU Di WANG JinJun CUI GuangYao PAN Chong Fluid Mechanics Key Laboratory of Education Ministry Beijing University of Aeronautics and AstronauticsBeijing 100191China

The effects of directional riblets surfaces on the turbulent/non-turbulent(T/NT) interface in turbulent boundary layers are experimentally investigated using two-dimensional time-resolved particle image velocimetry(PIV). The velocity field of streamwise-wall-normal plane for the smooth surface, converging and diverging riblets surfaces are measured. The interface is detected using the criterion of local kinetic energy. The statistical properties of interface height and conditional averaged velocity for different surfaces are analyzed. It is shown that, the converging and diverging riblets surfaces have little effect on the fractal dimension of the T/NT interface, but they cause the intermittency profile deviate from error function and the probability distribution of interface height deviate from Gaussian function. To be specific, the distribution of interface height for the converging riblets surface shows a positive skewness while it shows a negative skewness for the diverging riblets ***, the conditional averaged streamwise velocity and spanwise vorticity across the interface are analyzed, and it is found that their self-similarities are preserved for different surfaces when normalized with respective friction velocity. The correlation analysis reveals that near-wall streamwise velocity fluctuation and interface height show a negative correlation.

关键词： riblets surface turbulent boundary layers turbulent/non-turbulent(T/NT)interface conditional averaging

Effect of Reactor Pressure on Qualities of GaN layers Grown by Hydride Vapour Phase Epitaxy

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Chinese Physics Letters 2007年第5期24卷 1390-1392页

作者：邱凯尹志军李新化钟飞姬长建韩奇峰曹先存陈家荣罗向东王玉琦 Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 Jiangsu Provincial Key Lab of ASIC Design Nantong University Nantong 226007

The influence of reactor pressure on GaN layers grown by hydride vapour phase epitaxy （HVPE） is investigated. By decreasing the reactor pressure from0. 7 to 0.5 mm, the GaN layer growth mode changes from the island-like one to the step flow. The improvements in structural and optical properties and surface morphology of GaN layers are observed in the step flow growth mode. The results clearly indicate that the reactor pressure, similarly to the growth temperature, is One of the important parameters to influence the qualities of GaN epilayers grown by HVPE, due to the change of growth mode.

关键词： Pressure layers Hydride

High-Efficiency Phosphorescent White Organic Light-Emitting Diodes with Stable Emission Spectrum Based on RGB Separately Monochromatic Emission layers

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Chinese Physics Letters 2014年第4期31卷 122-125页

作者： ZHANG Zhi-Qiang LIU Yi-Peng DAI Yan-Feng CHEN Jiang-Shan MA Dong-Ge ZHANG Hong-Mei State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chan~chun 130022 University of Chinese Academy of Sciences Beijing 100049 Department of Materials Science and Engineering Nanjing University of Posts and Telecommunications Nanjing 210023

Highly efficient phosphorescent white organic light-emitting diodes （WOLEDs） with stable emission spectra are successfully fabricated by using an RGB three-color separately monochromatic emission layer （EML） struc- ture. The EML consists of a sequence of bis（2-methyldibenzo[f, h]quinoxaline）（acetylacetonate） iridium （Ⅲ）（Ir（MDQ）2（acac）） doped tris（4-carbazoyl-9-ylphenyl）amine （TCTA） as the red emission layer, iridium, tris（2- phenylpyidine）（Ir（ppy）3） doped TCTA as the green emission layer and iridium（Ill） Ibis（4, 6-difuorophenyl）- pyridinato-N, C2＇]picolinate （FIrpic） doped a mixed-host of TCTA and tris（4-carbazoyl-9-ylphenyl）amine （26DCz PPy） as the blue emission layer. Without using any out-coupling techniques, the resulting WOLEDs achieve a power efficiency of 421m/W at lOO cd/m2, and 34 lm/W at 1000 cd/m2. The WOLEDs also show excellent spec- trum stability with bias voltages, remaining the Commission Internationale de L＇Eclairage coordinates at （0.44, 0.43） from 1000 cd/m2 to 10000 cd/m2 and the color rendering index is as high as over 80. We contribute the sta- ble emission spectrum to the RGB separate EML structure that successfully suppresses the undesired competition between host-guest energy transfer and direct exciton formation on emissive dopants by effectively controlling the position of exciton recombination region.

关键词： layers High-Efficiency red emission

Improved automatic search of impossible differentials for camellia with FL/FL-1 layers

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Science China(Information Sciences) 2018年第3期61卷 220-222页

作者： Yaoling DING Xiaoyun WANG Ning WANG Wei WANG Department of Computer Science and Technology Tsinghua University Institute for Advanced Study Tsinghua University Key Laboratory of Cryptologic Technology and Information Security Ministry of EducationShandong University School of Mathematics Shandong University School of Computer Science and Technology Shandong University

Camellia is an international standard adopted by ISO/IEC and is recommended by CRYPTREC and NESSIE *** et al.[1]presented an effective tool to search truncated impossible differentials for word-oriented block ciphers with bijective ***,their method only adopted Sbox as the nonlinear part and cannot be applied to Camellia with F L/F *** discover

关键词： Improved automatic search of impossible differentials for camellia with FL/FL layers

Enhancing Fluorescence of Shallow Nitrogen-Vacancy Centers in Diamond by Surface Coating with Titanium Oxide layers

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Chinese Journal of Chemical Physics 2019年第5期32卷 521-524页

作者： Wen-long Zhang Li-ren Lou Wei Zhu Guan-zhong Wang Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics University of Science and Technology of China Hefei 230026 China

We present an enhancement of the fluorescence of shallow(<10 nm) nitrogen-vacancy(NV^-)centers by using atomic layer deposition to deposit titanium oxide layers on the diamond surface. In this way, the shallow NV-cent... 详细信息

We present an enhancement of the fluorescence of shallow(layers on the diamond surface. In this way, the shallow NV-center charge states were stabilized, leading to the increasing fluorescence intensity of about 2 times. This surface coating technique could produce a protective layer of controllable thickness without any damages to the solid-state quantum system surface, which might be an approach to the further passivation or packaging techniques for the solid-state quantum devices.

关键词： Shallow NV- center Titanium oxide coating layers Charge state stabilization Fluorescence enhancement

Lanthanide-based downshifting layers tested in a solar car race

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Opto-Electronic Advances 2019年第6期2卷 1-8页

作者： Sandra F.H.Correia Ana R.N.Bastos Lianshe Fu Luís D.Carlos Paulo S.André Rute A.S.Ferreira Department of Physics and CICECO-Aveiro Institute of Materials University of Aveiro3810-193 AveiroPortugal Department of Electric and Computer Engineering and Instituto de Telecomunicacoes Instituto Superior TénicoUniversidade de Lisboa1049-001 LisbonPortugal Department of Electronics Telecommunications and InformaticsInstituto de TelecomunicacoesUniversity of AveiroCampus Universitário de Santiago3810-193 AveiroPortugal

The mismatch between the AM1.5G spectrum and the photovoltaic (PV) cells absorption is one of the most limiting factors for PV *** overcome this constraint through the enhancement of solar energy harvesting,luminescent downshifting (LDS) layers are very promising to shape the incident sunlight and,thus,we report here the use of Tb^3+- and Eu^3+-doped organic-inorganic hybrid materials as LDS layers on Si PV *** measurements on the PV cell,done before and after the deposition of the LDS layers,confirm the positive effect of the coatings on the cell’s performance in the UV spectral *** maximum delivered power and the maximum absolute external quantum efficiency increased 14% and 27%,***,a solar powered car race was organized in which the small vehicle containing the coated PV cells presented a relative increase of 9% in the velocity,when compared to that with the uncoated one.

关键词： photovoltaics downshifting layers solar car organic-inorganic hybrids lanthanide ions

Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 513-525页

作者： YAN Wei1 & CHEN Weiqiu1,2 1. Department of Civil Engineering, Zhejiang University, Hangzhou 310027, China 2. State Key Lab of CAD & CG, Zhejiang University, Hangzhou 310027, China Department of Civil Engineering Zhejiang University Hangzhou China State Key Lab of CAD & CG Zhejiang University Hangzhou China

The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with time elapsing.

关键词： functionally graded beam piezoelectric layers Kelvin-Voigt model state-space method

Continuous Deposition of Double-sided Y_2O_3/YSZ/CeO_2 Buffer layers for Coated Conductors

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稀有金属材料与工程 2011年第S3期40卷 311-314页

作者： Xia Yudong, Zhang Fei, Zhang Ning, Zhang Junfei, Chai Gang, Guo Pei, Jing Tongguo, Xiong Jie, Zhao Xiaohui, Tao Bowan, Li Yanrong State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China Univ Elect Sci & Technol China State Key Lab Elect Thin Films & Integrated Devic Chengdu 610054 Peoples R China

In this paper, we report a continuous deposition method for double-sided CeO2/YSZ/Y2O3 buffer layers by reel-to-reel in a D.C. magnetron reactive sputtering system. X-ray diffraction exhibited all the samples were highly c-axis oriented and atomic force microscope observations revealed a smooth, dense and crack-free surface morphology. Out-of-plane, in-plane texture, and surface roughness of multi-buffer layers were improved under optimized deposition conditions. Full width at half maximum (FWHM) values of out-of-plane and in-plane were about 4° and 5.5° in 50 cm double-sided buffed template. YBa2Cu3O7-δ films with thickness of 1.2 μm were deposited on both sides of the buffed tape. Both sides showed similar critical current density, Jc (77 K, self field) as 0.8 MA/cm2 and 0.7 MA/cm2, respectively.

关键词： continuous deposition double-sided Y2O3/YSZ/CeO2 buffer layers