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51.
多维漫透射光谱技术利用传统的近红外透射测量方式,增加一维扫描装置,获得透射方向上的径向光谱,并利用多点漫透射光谱对复杂混合溶液进行成分分析。实验设计了基于氙灯光源、精密电控平移台和光谱仪的检测装置,选用Intralipid-20%,India Ink和C6H12O6共配制225种成分含量不同的混合溶液,分别测量距其透射中心点0~5 mm(间隔0.25 mm)范围内的20点漫透射光谱信号,以偏最小二乘回归算法对单点和多点漫透射光谱信号进行建模分析。实验得到India Ink含量和Intralipid-20%含量随漫透射光位置点的增加建模及预测的精度提高,C6H12O6含量随漫透射光位置点的增加建模及预测精度没有明显变化。结果表明,增加不同位置信息的漫透射光谱信号,能够提高复杂混合溶液中强吸收物质和强散射物质的信噪比,对于弱吸收弱散射物质有望在提升系统精度的前提下提高其预测能力。 相似文献
52.
在HIRFL加速器系统中, 需要对射频加速电压的幅度和相位进行精确控制,以实现对重离子的精确俘获、 加速和引出。传统的幅度、相位稳定控制系统采用幅度和相位两个反馈闭合环路来分别稳定腔体电压的幅度和相位。 数字化高频低电平控制系统(LLRF) 基于可编程逻辑门阵列(FPGA)和数字信号处理(DSP), 采用直接数字频率合成(DDS)与数字正交调制解调(I/Q)技术来实现对高频功率源的控制。 相位控制精度更高, 系统更加稳定。 目前控制系统在假负载上通过了长期稳定性的实验和高功率实验, 幅度偏差小于或等于±1%, 相位偏差小于或等于±0.5°。 In order to ensure that the beam quality is well enough, we need to precisely control the frequency, amplitude and phase of cavity electric field. Traditional control system consists of amplitude loop and phase loop. And these two loops control amplitude and phase stability respectively. The digital low level radio frequency (LLRF) system, which uses advanced digital control technology, needs only one feed back loop to control amplitude and phase stability. The phase control precision and stability of the system are higher than the traditional control system. The LLRF system is based on field programmable gate array (FPGA) and digital signal processing (DSP), and implemented by direct digital frequency synthesis (DDS) and digital orthogonal modulation and demodulation (I/Q) technology. The digital LLRF system has been tested in a long term stability and high power experiments. The amplitude deviation is lower than ±1%, and phase control accuracy is within ±1°. 相似文献
53.
采用电子束及真空热蒸发的方式镀制了氧化钨薄膜及掺杂的氧化钨的复合共生薄膜.运用拉曼光谱以及电化学工作站等测试手段分析了氧化钨复合共生薄膜的结构及电致变色性能.通过对拉曼光谱曲线的解叠分峰处理发现,源于晶相的810 cm-1拉曼峰的相对强度变化与样品的致色效率存在负相关,即拉曼峰相对强度越小,样品的致色效率越高. 相似文献
54.
Employing the approximation theory based on refraction and the definition of the total point-spread-function of the imaging system, the variation in the edge contrast of simple model samples is discussed with different source-to-sample and sample-to-detector distances, which actually means different spatial resolutions of the imaging system. The experiments were carried out with the Beamline 4W1A imaging setup at the Beijing Synchrotron Radiation Facility for simple model and insect samples. The results show that to obtain clear phase-contrast images of biologic tissues for the X-ray in-line imaging setup, with determined parameters such as the size of the X-ray source, the pixel size of the detector and the fixed source-to-sample distance, there is a range of optimized sample-to-detector distances. The analysis method discussed in this article can be helpful in optimizing the setup of X-ray in-line phase-contrast imaging. 相似文献
55.
56.
Gang Zhang Shengzhi Zhao Kejian Yang Guiqiu Li Dechun Li Kang Cheng Chao Han Bin Zhao Yonggang Wang 《Optics & Laser Technology》2012,44(4):794-799
By using both the single-walled carbon nanotube saturable absorber (SWCNT-SA) and the electro-optic (EO) modulator, the stably doubly Q-switched and mode-locked (QML) operation of Nd:Gd0.3Lu0.33Y0.37VO4 laser has been demonstrated. The QML laser characteristics such as the pulse width, single-pulse energy, etc., have been measured for different modulation frequencies of the EO modulator (fe) and reflectivity (R) of output coupler. In comparison with the solely passively QML laser with SWCNT-SA, the experimental results show that the doubly QML laser can generate more stable and shorter pulses with higher pulse energy. At 9.24 W pump power, fe=1 kHz and R=93.5%, the doubly QML laser has compressed the Q-switched envelope pulse width 88% and improved the mode-locked pulsed energy 55 times. 相似文献
57.
58.
LI ZhiHong SU Jun GUO Bing LI ZhiChang BAI XiXiang LIU JianCheng LI YunJu YAN ShengQuan WANG BaoXiang WANG YouBao LIAN Gang ZENG Sheng LI ErTao CHEN YongShou SHU NengChuan FAN QiWen & LIU WeiPing China Institute of Atomic Energy Beijing China 《中国科学:物理学 力学 天文学(英文版)》2010,(4)
The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance. 相似文献
59.
Based on a systematic investigation of J/ψ(ψ) → VP,where V and P stand for light vector and pseudoscalar mesons,we identify the role played by the electromagnetic(EM) transitions and intermediate meson loop transitions,which are essential ingredients for understanding the J/ψ and ψ couplings to VP.We show that on the one hand,the EM transitions have relatively larger interferences in ψ→ρπ and K*K+c.c.as explicitly shown by vector meson dominance(VMD).On the other hand,the strong decay of ψ receives relatively larger destructive interferences from the intermediate meson loop transitions.By identifying these mechanisms in an overall study of J/ψ(ψ)→VP,we provide a coherent understanding of the so-called "ρπ puzzle". 相似文献
60.