Electric-field control of nonvolatile magnetization in Co40Fe40B20/Pb(Mg(1/3)Nb(2/3))(0.7)Ti(0.3)O3 structure at room temperature

We report a large and nonvolatile bipolar-electric-field-controlled magnetization at room temperature in a Co(40)Fe(40)B(20)/Pb(Mg(1/3)Nb(2/3))(0.7)Ti(0.3)O(3) structure, which exhibits an electric-field-controlled looplike magnetization. Investigations on the ferroelectric domains and crystal structures with in situ electric fields reveal that the effect is related to the combined action of 109° ferroelastic domain switching and the absence of magnetocrystalline anisotropy in Co(40)Fe(40)B(20). This work provides a route to realize large and nonvolatile magnetoelectric coupling at room temperature and is significant for applications.     

Acousto-optic Q-switched self-frequency-doubling Er:Yb:YAl3(BO3)4 laser at 800 nm

Actively Q-switched self-frequency-doubling laser at 800 nm was first reported in an Er:Yb:YAl3(BO3)4 crystal by using an acousto-optical modulator. At incident pump power of 16 W and pulse repetition frequency of 1 kHz, 1600 nm fundamental pulse laser with energy of 130 μJ and width of 170 ns, and self-frequency-doubling 800 nm pulse laser with energy of 20 μJ and width of 96 ns were respectively achieved in a hemispherical resonator end-pumped by a 970 nm laser diode. Pulse characteristics of fundamental and self-frequency-doubling lasers at different pulse repetition frequencies were also investigated.     

Vertical-bandwidth-limited digital holography

Optical scanning holography (OSH) is a promising technique to acquire a big-size digital hologram. However, the acquisition speed is limited by the mechanical scanner. In this Letter we apply the OSH in conjunction with an anisotropic low-pass filtering pupil to acquire vertical-bandwidth-limited (VBL) holograms. The size and the acquisition time of the VBL hologram can be reduced by one order of magnitude while the horizontal resolution remains the same as the conventional scanning hologram. The VBL hologram can be coded as an off-axis hologram without any postfiltering. Meanwhile, the full horizontal bandwidth of the displaying device can be capitalized.     

Spectral tuning and energy transfer in a potential fluorescent lamp phosphor BaMg2Al6Si9O30:Eu2+

BaMg₂Al₆Si₉O₃₀:Eu²⁺ phosphors are synthesized by the solid-state reaction method and their photoluminescence (PL) properties are investigated. The ultraviolet emission originates from Eu²⁺(I) substituting for Ba²⁺ sites, whereas the blue emission is attributed to Eu²⁺(II) substituting for Mg²⁺ sites. With increasing Eu²⁺ doping concentrations, the blue emission band shifts to long wavelength and the PL intensity ratio of blue to ultraviolet emission increases. Energy transfer between the two different Eu²⁺ ions is analyzed by photoluminescence excitation and emission spectra, and lifetimes. Results indicate that the emission spectra can be tuned by changing Eu²⁺ contents. We have also demonstrated that BaMg₂Al₆Si₉O₃₀:Eu²⁺ phosphor is a kind of potential phosphor for fluorescent lamps.     

Phase sensitive amplifier for PSK signals based on non-degenerate four-wave-mixing in the optical fiber

A phase-sensitive-amplifier (PSA) using only one pump channel based on frequency non-degenerate four-wave-mixing (FWM) process for phase-shift-keying (PSK) signals is proposed and demonstrated. Theoretical analyses are given first. By optimizing power levels of three channels and parameters of the highly nonlinear fiber (HNLF), the PSA is able to restore the signal fidelity (down to a BER of 10^? 9) as the input signal shows an error-floor with the BER of 10^? 6. Moreover, the PSA for the multi-level PSK signals could be achieved by adjusting the phase relationship between two input signals.     

Highly-efficient optical power combiners based on evanescently-coupled micro/nano optical fibers

Novel highly-efficient power combiners based on evanescently-coupled micro/nano optical fibers are proposed and experimentally demonstrated. Experimental results show that the maximum power combing efficiency can be >90%. The combining efficiency is overlap length dependent. As long as the overlap length is long enough (～7 mm), a stable high combining efficiency can always be achieved. The presented optical power combiners with the advantages of easy fabrication, low-loss, low-cost, and wavelength insensitivity can find potential applications in micro/nano photonic devices, optical communications and optical interconnects.     

The use of chromium minerals in the 4th–3rd century BC China? A preliminary study of a bronze Pan unearthed from Jiuliandun Graves,Hubei Province,central southern China

A bronze Pan (water vessel), dating back to the 4th–3rd century BC, was excavated at Jiuliandun in Hubei Province, central southern China, in 2002. The Pan attracts wide attention among the Chinese archaeologists and conservators for its uniqueness in style and color, which turns out to be due to a black‐brown film of about 1 mm thickness. In the present work, a combined use of X‐ray fluorescence (XRF), micro‐Raman, and X‐ray diffraction (XRD) was employed to determine both chemical and physical compositions of the Pan's film. The results are summarized as follows: (1) The film, as XRF analysis indicates, has high concentrations of chromium (Cr) and iron (Fe); (2) Both Raman and XRD analyses suggest that the element Cr probably exists in the film mainly in the form of chromium oxide (Cr₂O₃). Raman analysis also implies the presence of PbCrO₄·PbO in the film; (3) XRD analysis suggests that the element Fe exists in the film in the form of magnetite (Fe₃O₄). Based on these analytical results and Chinese historical records, we propose that, as early as in the 3rd century BC, people in central southern China might have discovered and intentionally used chromium minerals for bronze surface treatment (such as coating). The source of chromium minerals used in this period was likely Cr‐spinel minerals from meteorites. More work remains to be done to test the possibility of using Cr‐spinel minerals for bronze production and decoration. Other issues, such as the possibility of forming a chromium‐rich film during the underground burial, also need to be solved. Copyright © 2011 John Wiley & Sons, Ltd.     

基于LabVIEW的惯性测量单元信号采集及处理系统设计

利用LabVIEW设计了惯性测量单元信号采集及处理软件,主要包括串口通信、数据分离及信号处理等模块;串口通信模块采用VISA方式编程,建立了惯性测量单元与上位机之间的通信;根据惯性测量单元输出数据的格式,利用LabVIEW中的匹配模式函数分离出沿三轴向的加速度信号和角速率信号;设计了一种用于去除加速度信号中低频成份的数字滤波器;在建立的陀螺漂移模型基础上,分别进行小波基、小波分解层数、阈值函数及阈值估计方法等小波参数的选取.     

基于超导储能脉冲变压器的多模块脉冲电源设计

为了探索一种更加紧凑的导轨型电磁推进基础实验用脉冲电源,以实验室现有高温超导储能脉冲变压器为单元模型,在单谐振电路脉冲成形方案的基础上,设计了环形结构的多模块脉冲电源,分析了环形结构中考虑互感的多模脉冲电源电路的充放电过程。通过对八模块环形结构脉冲电源进行仿真分析,得到了接近150kA的电流脉冲,原边电压限制13kV左右。可以得出,利用单谐振电路的多模块超导储能脉冲变压器并联放电方式,可以实现大电流脉冲的输出的要求,而且环形结构中各线圈存在的互感更有利于多模块脉冲电源。     

强激光加载下金属材料微喷回收诊断

金属材料在冲击载荷下的动态响应在许多民用工程、航空航天等领域都有重要的应用背景.而金属材料在冲击载荷下的微喷形成过程,包括微射流、碎裂以及微层裂的物理过程的研究中尚存在许多空白.介绍了国内首次在神光Ⅲ原型激光装置上开展的金属材料微喷回收实验,实现了激光加载下低密度泡沫材料对微喷颗粒的回收,对回收样品进行了X光CT分析,通过图像重建,获得了回收微喷颗粒的三维图像,以及颗粒不同形态分布、颗粒尺寸、颗粒质量等定量结果.