Novel Rat-race Hybrid Coupler for RF Front-end Module

In this paper, a novel compact rat-race hybrid coupler incorporating an improved beeline compact microstrip resonant cell(IB-CMRC) is presented firstly. The size of the coupler is reduced by 46.5% than conventional one due to IB-CMRC’s excellent slow-wave effect. The novel coupler possesses strong ability of high-order harmonic suppression (above 30 dB) in addition. The measured insertion loss is comparable to that of a conventional microstrip hybrid coupler. Great potential applications of this IB-CMRC can be explored in MICs and MMICs to reduce the circuits size, suppress harmonics and improve the overall performance of the RF front-end module.     

Multifunctional core–shell nanoparticles: superparamagnetic,mesoporous, and thermosensitive

Multifunctional core–shell composite nanoparticles (NPs) have been developed by the combination of three functionalities into one entity, which is composed of a single Fe₃O₄ NP as the magnetic core, mesoporous silica (mSiO₂) with cavities as the sandwiched layer, and thermosensitive poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAAm-co-AAm)) copolymer as the outer shell. The mSiO₂-coated Fe₃O₄ NPs (Fe₃O₄@mSiO₂) are monodisperse and the particle sizes were varied from 25 to 95 nm by precisely controlling the thickness of mSiO₂-coating layer. The P(NIPAAm-co-AAm) were then grown onto surface-initiator-modified Fe₃O₄@mSiO₂ NPs through free radical polymerization. These core–shell composite NPs (designated as Fe₃O₄@mSiO₂@P(NIPAAm-co-AAm)) were found to be superparamagnetic with high r ₂ relaxivity. To manipulate the phase transition behavior of these thermosensitive polymer-coated NPs for future in vivo applications, the characteristic lower critical solution temperature (LCST) was subtly tuned by adjusting the composition of the monomers to be around the human body temperature (i.e. 37 °C), from ca. 34 to ca. 42 °C. The thermal response of the core–shell composite NPs to the external magnetic field was also demonstrated. Owing to their multiple functionality characteristics, these porous superparamagnetic and thermosensitive NPs may prove valuable for simultaneous magnetic resonance imaging (MRI), temperature-controlled drug release, and temperature-programed magnetic targeting and separation applications.     

Diameter-dependent thermal-oxidative stability of single-walled carbon nanotubes synthesized by a floating catalytic chemical vapor deposition method

In this paper, purified single-walled carbon naotubes (SWCNTs) with three different diameters were synthesized using a floating catalytic chemical vapor deposition method with ethanol as carbon feedstock, ferrocene as catalyst, and thiophene as growth promoter. The thermal-oxidative stability of different-diameter SWCNTs was studied by using thermal analysis (TG, DTA), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. The results indicate that small diameter SWCNTs (∼1 nm) are less stable and burn at lower temperature (610 °C), however, the larger diameter SWCNTs (∼5 nm) survive after burning at higher temperature (685 °C), the oxidation rate varies inversely with the tube diameter of SWCNTs, which may be concluded that the higher oxidation-resistant temperature of larger diameter SWCNTs can be attributed to the lower curvature-induced strain by rolling the planar graphene sheet for the larger diameter, so small tubes will become thermodynamically unstable.     

Continuous-wave fiber cavity ring-down measurements using frequency-shifted interferometry

We present a spatial-domain fiber cavity ring-down (CRD) technique that does not require optical pulses for time-resolved detection. Instead of measuring the intensity decay rate of an optical pulse in the time domain as in conventional CRD experiments, we measure the decay rate of a CW signal in a ring-down cavity (RDC) using frequency-shifted interferometry in the spatial domain, as a function of distance traveled by the light. As a proof-of-concept demonstration, we measured fiber bend loss in a loop RDC using this technique, and a cavity loss change as low as 0.0135 dB induced by every fiber turn on a mandrel was unambiguously discerned.     

痂囊腔菌素A与肌红蛋白相互作用的光谱研究

研究了痂囊腔菌素A(EA)与肌红蛋白(Mb)的相互作用.通过紫外-可见吸收光谱研究发现痂囊腔菌素A与肌红蛋白在避光与光照两种条件作用模式存在明显差异;痂囊腔菌素A对肌红蛋白的内源荧光有猝灭作用,形成了新的配合物,属于静态猝灭;热力学计算结果表明痂囊腔菌素A与肌红蛋白之间以疏水作用力结合.同步荧光光谱研究了痂囊腔菌素A对...     

Digital pulse shape discrimination methods for n-γ separation in an EJ-301 liquid scintillation detector

A digital pulse shape discrimination system based on a programmable module NI-5772 has been established and tested with an EJ-301 liquid scintillation detector. The module was operated by running programs developed in Lab VIEW, with a sampling frequency up to 1.6 GS/s. Standard gamma sources22 Na,137Cs and60 Co were used to calibrate the EJ-301 liquid scintillation detector, and the gamma response function was obtained. Digital algorithms for the charge comparison method and zero-crossing method have been developed. The experimental results show that both digital signal processing(DSP) algorithms can discriminate neutrons from γ-rays. Moreover,the zero-crossing method shows better n-γ discrimination at 80 ke Vee and lower, whereas the charge comparison method gives better results at higher thresholds. In addition, the figure-of-merit(FOM) for detectors of two different dimensions were extracted at 9 energy thresholds, and it was found that the smaller detector presented better n-γseparation for fission neutrons.     

基于高光谱成像技术的油菜叶片SPAD值检测

以油菜叶片为研究对象,利用高光谱成像技术,成功建立了叶绿素相对值SPAD值的预测模型。共采集了160个油菜叶片样本在380～1030 nm范围内的高光谱图像。选择500～900 nm之间的平均光谱作为油菜叶片样本的光谱。利用蒙特卡罗最小二乘法(monte carlo partial least squares, MC-PLS)剔除了13个异常样本,基于剩余的147个样本光谱数据与SPAD测量值进行分析,采用了不同的方法建立了多种预测模型,包括：全光谱的偏最小二乘法(partial least squares, PLS)模型,连续投影算法(successive projections algorithm, SPA)选择特征波长的PLS预测模型,“红边”位置(λ_red)的简单经验估测模型,三种植被指数R₇₁₀/R₇₆₀,(R₇₅₀-R₇₀₅)/(R₇₅₀-R₇₀₅)和R₈₆₀/(R₅₅₀*R₇₀₈)分别建立的简单经验估测模型,以及基于这三种植被指数的PLS预测模型。建模结果显示,全光谱的PLS模型预测效果最为精确,其预测相关系数r_p为0.833 9,预测均方根误差RMSEP为1.52。而使用SPA算法选出的8个特征波长所建立的PLS模型其预测结果可达到与全光谱的PLS模型非常接近的水平,而且在保证一定精度的条件下减少了大量运算,节省了运算时间,大幅提高了建模的速度。而基于红边位置和选择的三种植被指数而建立的简单经验估计模型其预测结果虽与基于全光谱的PLS预测模型有一定差距,但模型简单、运算量小,适合用于对精度要求不高的场合,对后续的便携仪器设备开发有一定的指导作用。     

Fabrication and magnetic properties of ordered Fe60Pb40 nanowire arrays electrodeposited in AAO templates

Ordered ferromagnetic-nonmagnetic heterogeneous Fe₆₀Pb₄₀ nanowire arrays were successfully fabricated by alternating current (AC) electrodeposition into nanoporous alumina templates. Transmission electron microscopy (TEM) image and selected-area diffraction (SAED) pattern analysis showed that the Fe₆₀Pb₄₀ nanowires are polycrystalline with an average diameter of 22 nm and lengths up to several micrometers. X-ray diffraction (XRD) observations indicated that α-Fe and fcc Pb phase coexist and do not form metastable alloy phase. The as-deposited samples were annealed at 200, 300, 400 and 500 ^°C, respectively. Magnetic measurements showed that nanowires have high magnetic anisotropy with their easy axis parallel to the nanowire arrays, and the coercivity of the samples increased with the annealing temperature up to 400 ^°C and reached a maximum (2650 Oe). The change of magnetic properties associated with the microstructure was discussed.     

Strong Correlation of Fluorescence Photons without Quantum Interference

It has been predicted that a driven three-level V atom can emit strongly correlated fluorescence photons in the presence of quantum interference. Here we examine the effects of quantum interference on the intensity correlation of fluorescence photons emitted from a driven three-level A atom. Unexpectedly, strong correlation occurs without quantum interference. The quantum interference tends to reduce the correlation function to a normal level. The essential difference between these two cases is traced to the different effects of quantum interference on coherent population trapping （OPT）. For the V atom, quantum interference and coherent excitation combine to lead to OPT. For the A atom, however, the quantum interference tends to spoil OPT while the coherent excitation induces the effect.     

全息波导显示系统中输出光栅的优化

全息波导显示系统中输出光栅的衍射效率、位置和长度对整个显示系统的光强输出均匀性及能量利用率有重要的影响.通常输出光强均匀性由输出光栅的衍射效率决定,能量利用率受多重光栅的位置和长度影响.本文以中心视场光束的输出光强均匀为目的,对相应输出光栅衍射效率的位置分布进行优化与曲线拟合,得到输出光栅衍射效率随输出位置连续递增的分布曲线,并应用到所有视场光束.计算结果表明,相比于传统阶梯状衍射效率分布输出光栅,全息波导显示系统中采用具有连续衍射效率分布输出光栅时的光强输出均匀性得到明显提升.针对部分衍射光束未能进入出瞳的现象,提出错位优化法,按照出瞳大小和使用距离优化各重输出光栅的位置和尺寸,减小了光栅的无效衍射区域,提高了出瞳范围内的能量利用率.