多参数对叶顶气膜冷却的影响

基于压力敏感漆(PSP)实验技术,本文研究了某F级重型燃机一级动叶平面叶顶和凹槽叶顶在不同冷却射流与主流质量流量比,不同密度比和不同叶顶间隙大小等多参数影响下的气膜冷却特性。平面叶顶冷却射流在气膜孔后往吸力面覆盖,凹槽叶顶在槽内形成回旋涡,冷却射流往压力面覆盖并向尾缘形成累积效应。平面叶顶和凹槽叶顶气膜冷却效率均随质量流量比的增大而增大。密度比增大,冷却射流出口动量减小,抑制了叶顶气膜垂直射流的吹离趋势,从而提高气膜冷却效果。叶顶间隙与叶顶形状、质量流量比等参数对气膜冷却效率有关联影响;间隙增大,气膜冷却效率在不同工况下的表现不同。另外凹槽叶顶的整体气膜冷却效果优于同等条件的平面叶顶。     

食品微生物对超高压处理的逆境响应

 超高压（High Hydrostatic Pressure,HHP）作为一种非热杀菌技术,在食品工业中有着很广泛的应用,与传统的热加工处理相比,在保持食品品质、杀菌、钝酶等方面都有其明显的优势。通过对国内外相关文献的分析,对HHP处理后处于亚致死状态食品微生物的细胞膜、遗传与结构物质、机体代谢等方面,以及大部分食品微生物在应对外界的多种刺激时而进行的普遍性调控机制的研究进行了总结,探讨了经过HHP处理后处于亚致死状态的食品微生物在逆境下存活的应激反应。     

多孔介质高温蓄热的热性能分析

高温蓄热是太阳能热发电、高温热利用中的重要组成部分。本文对基于多孔介质和熔融盐流体的高温蓄热过程进行了计算分析,对蓄热时间、流体进口温度、进口速度对斜温层温度分布的影响进行了分析。结果表明进口温度对斜温层厚度的影响较小,进口速度的增加会导致斜温层厚度的增加。同时对流体和多孔介质的温度差进行了分析,得到了应用于局部热平衡和非热平衡的雷诺数判据。     

符号回归在换热关联式求解中的应用

本文利用符号回归分析换热器的实验数据,以寻找更高精度的换热关联式。为改进MATLAB环境下的遗传规划工具箱GPLAB的性能,增入了四种新功能:个体简化、常数优化、单亲交叉、新生操作。利用改进后的GPLAB对连续螺旋折流板管壳式换热器壳程传热的实验数据进行了符号回归,得到的换热关联式的预测精度高且稳健度强。     

Efficient Multiparty Quantum Secret Sharing of Secure Direct Communication Based on Bell States and Continuous Variable Operations

By using some ordered Bell states as quantum channel, we propose a protocol for multiparty quantum secret sharing of secure direct communication. The present scheme follows the ideas of dense coding and ping-pong technique. It has a high source capacity as each traveling photon carries two bits of classical secret messages, and has a high intrinsic efficiency because almost all the instances are useful. Since the continuous variable operations instead of the discrete unitary operations used usually are employed to realize the sharing controls, the security of the present protocol is therefore enhanced. Furthermore, due to existing multilevel security checking procedures, the present scheme can prevent against some usual attack strategies.     

Design for broadband high-efficiency grating couplers

In this Letter, we propose general optimization methods to design broadband high-efficiency grating couplers for planar waveguides. We attribute the coupling bandwidth to the mismatch of effective indices between the diffracted beam and the actual grating structure around the operation wavelength for fiber to waveguide excitation. The coupling bandwidth formula is deduced. A simple parameter-separate optimization procedure is proposed for general layered grating couplers for high coupling efficiency. Using our principle, we optimized a grating coupler for a horizontal slot waveguide operating at wavelength 1.55 μm for TM polarization. The grating coupler has 1 dB bandwidth of 60 nm and coupling efficiency of 65% with incident light from single-mode optical fiber (SMF) at 8°.     

Diode-pumped mode-locked femtosecond Tm:CLNGG disordered crystal laser

A diode-end-pumped passively mode-locked femtosecond Tm-doped calcium lithium niobium gallium garnet (Tm:CLNGG) disordered crystal laser was demonstrated for the first time to our knowledge. With a 790 nm laser diode pumping, stable CW mode-locking operation was obtained by using a semiconductor saturable absorber mirror. The disordered crystal laser generated mode-locked pulses as short as 479 fs, with an average output power of 288 mW, and repetition rate of 99 MHz in 2 μm spectral region.     

Synchronization between integer-order chaotic systems and a class of fractional-order chaotic systems via sliding mode control

In this paper, we focus on the synchronization between integer-order chaotic systems and a class of fractional-order chaotic system using the stability theory of fractional-order systems. A new sliding mode method is proposed to accomplish this end for different initial conditions and number of dimensions. More importantly, the vector controller is one-dimensional less than the system. Furthermore, three examples are presented to illustrate the effectiveness of the proposed scheme, which are the synchronization between a fractional-order Chen chaotic system and an integer-order T chaotic system, the synchronization between a fractional-order hyperchaotic system based on Chen's system and an integer-order hyperchaotic system, and the synchronization between a fractional-order hyperchaotic system based on Chen's system and an integer-order Lorenz chaotic system. Finally, numerical results are presented and are in agreement with theoretical analysis.     

Defects in room-temperature ferromagnetic Cu-doped ZnO films probed by x-ray absorption spectroscopy

We report a comprehensive study of the defects in room-temperature ferromagnetic (RTFM) Cu-doped ZnO thin films using x-ray absorption spectroscopy. The films are doped with 2 at.% Cu, and are prepared by reactive magnetron sputtering (RMS) and pulsed laser deposition (PLD), respectively. The results reveal unambiguously that atomic point defects exist in these RTFM thin films. The valence states of the Cu ions in both films are 2(+). In the film prepared by PLD, the oxygen vacancies (V(O)) form around both Zn ions and Cu ions in the hexagonal wurtzite structure. Upon annealing of the film in O(2), the V(O) population reduces and so does the RTFM. In the film prepared by RMS, the V(O)s around Cu ions are not detected, and the V(O) population around Zn ions is also smaller than in the PLD-prepared film. However, zinc vacancies (V(Zn)) are evidenced. Given the low doping level of spin-carrying Cu ions, these results provide strong support for defect-mediated ferromagnetism in Cu-doped ZnO thin films.     

Crystal growth and optical properties of Cr3+, Er3+, RE3+: Gd3Ga5O12 (RE=Tm,Ho, Eu) for mid-IR laser applications

In this paper we report on the optical properties of triply Cr³⁺, Er³⁺, and RE³⁺ (RE=Tm, Ho, Eu) doped Gd₃Ga₅O₁₂ crystals that were grown by the Czochralski method. Optical absorption, near-infrared (NIR), and mid-infrared (mid-IR) fluorescence spectra were characterized for the fabricated crystals and corresponding luminescence decay measurements under 654 nm excitation were also carried out. Based on the analysis of energy transfer process between Er and RE (RE=Tm, Ho, Eu) ions, the energy transfer efficiency (ETE) values were evaluated, correspondingly. From the spectral data of all the studied crystals, it is observed that the co-doped Cr³⁺ ion highly increases the absorption pump power and the three kinds of co-doped RE³⁺ ions depopulate the Er:⁴I_13/2 energy level effectively. The spectral analysis shows that titled rare earth doped crystals are promising materials for ～3.0 μm mid-IR laser applications and among them Cr,Er,Eu:GGG is relatively more suitable due to its excellent optical properties compared with others.