激光诱导击穿光谱定量分析玉石中的Mg,Fe和Ca

基于对样品进行的激光诱导击穿光谱和X射线荧光光谱分析测试建立了天然玉石中主要元素Mg,Ca和微量元素Fe的定标曲线。实验采用纳秒级的Nd∶YAG激光器(波长:1 064nm)为光源,在延迟时间为3μs,激光脉冲累积数量为110,单个脉冲能量为100mJ,脉冲重复频率为10Hz的实验条件下,采用激光诱导击穿光谱技术装置对天然南阳独山玉石样品中的元素进行等离子体激发测试,得到波长在300~1 000nm的等离子光谱图。通过将得到的光谱图中特征峰与美国国家标准与技术研究院数据库进行对比,发现测试样品中含有Mg,Fe和Ca等元素,以X射线荧光光谱分析技术对四种南阳独山玉标准样品中测量出的Mg,Fe和Ca元素氧化物含量作为标准数据,选取含量比较高的Al元素作为内标元素,采用内标法对玉石光谱图中Mg,Fe和Ca元素特征峰值进行线性拟合,从而得出Mg,Fe和Ca三种元素的定标曲线,求出待测样品中这3种元素氧化物的含量,结果表明这三种元素氧化物的含量与中国珠宝宝石收藏鉴赏全集资料中所给出的元素氧化物含量的百分比范围MgO(0.28%~1.73%),Fe2O3(0~0.8%),CaO(18%~20%)相符合,相比于常用的方法,激光诱导击穿光谱技术可以快速地对待测样品进行检测,样品预处理简单且对样品损害较小。进一步验证了激光诱导击穿光谱技术对于玉石应用的可行性。     

电感耦合等离子体原子发射光谱法测定硅铝铁合金中多种元素的优化研究

应用电感耦合等离子体原子发射光谱 (ICP AES)法 ,对硅铝铁合金中的Al,Fe ,Ca,Cr,Mn ,Ni,Si和Ti元素进行了测定。研究了ICP AES的操作条件和溶样方法 ,确定了适宜的实验条件 ,如对仪器参数和共存元素对信号的影响进行了研究。将实验条件优化后 ,使用该方法测定硅铝铁合金中多种元素 ,标准钢样测定结果与推荐值相符。对各种元素的检出限分别为Al(0 0 2 9μg·mL- 1 ) ,Fe(0 0 0 4 μg·mL- 1 ) ,Ca(0 0 0 75 μg·mL- 1 ) ,Cr(0 0 0 15 μg·mL- 1 ) ,Mn(0 0 0 0 9μg·mL- 1 ) ,Ni(0 0 0 2 7μg·mL- 1 ) ,Si(0 0 4 5 μg·mL- 1 )和Ti(0 0 0 3μg·mL- 1 )。对所测元素 ,测定结果的相对标准偏差 (n =6 )在 0 3%～ 1 8%之间 ,加入标准溶液的回收率在96 7%～ 10 2 9%范围。测定合金样品中高含量硅的结果与标准化学 (重量 )法的结果也相符。该方法的特点是数据可靠 ,简便可行和易于推广。     

缅甸翡翠中铁元素的激光诱导击穿光谱定量检测

采用激光诱导击穿光谱(LIBS)技术定量分析缅甸翡翠中Fe元素的浓度。选择Fe元素的275.57 nm光谱线作为定量分析谱线,选取Si元素的288.17 nm光谱线作为内标谱线,选取12个缅甸翡翠样品作为研究对象,以其中9个样品绘制了传统定标法和内定标法的Fe元素定标曲线,并将定标曲线用于3个检验样品的Fe含量的实际预测。实验结果表明,采用传统定标方法时,定标样品光谱强度的相对标准偏差(RSD)在1.4%～8.3%之间,所建立的Fe元素浓度含量定标曲线的拟合相关系数R2为0.979,使用该方法建立的定标曲线对3个检验样品中Fe元素含量进行测定,最大相对误差为10.6%;而采用内定标法时,定标样品光谱强度的比值(I_Fe/I_Si)的相对标准偏差(RSD)在0.9%～5.7%之间,Fe的拟合相关系数R2达到0.989,样品中Fe元素的测定相对误差均可降低到7%以下。结果证明,利用内定标法定量分析翡翠中Fe的含量比传统定标法相对误差更小,采用LIBS技术结合内定标法更适于缅甸翡翠样品中Fe元素定量分析。     

偏振X射线荧光系统测量痕量Cd元素的Geant4模拟研究

通过传统能量色散X射线荧光分析(EDXRF)对Cd元素进行痕量分析时,X光管发出的原级轫致辐射连续谱对Cd元素的分析具有严重的影响。为了减弱原级X射线对测量结果的影响,通过Geant4程序包模拟不同几何尺寸下偏振激发X射线荧光分析(P-EDXRF)中荧光靶的结构,研究其在减弱测量过程中原级X射线轫致辐射连续谱的影响。为了提高模拟效率,本文分三步进行模拟。第一步模拟不同管电压下电子打靶过程,得到不同管压下的X光管原级能谱。第二步针对Cd元素的痕量分析设置不同种类、不同几何条件的Te及BaSO₄作为荧光靶材料进行模拟。结果表明在使用K_α1能量(27.468 keV)与Cd元素吸收限26.711 keV最为接近的Te作为荧光靶材料时,随着Te靶厚度增加Te元素的特征峰强度在100 μm前快速增长,在150 μm后趋于稳定。而其信噪比(SNR)在80 μm到达最大值21.434。继续增加厚度由于荧光靶材料的自吸收作用SNR开始有些许下降,达到饱和吸收厚度后稳定。在不同应用场景时荧光靶选材应有不同,对于测量时间没有限制的条件下,应选择荧光强度更大的荧光靶厚度。而对于测量时间相对较短的条件下,则应该选择SNR更大的荧光靶厚度。第三步模拟通过荧光靶后的出射能谱激发含0.01%Cd的样品,经过Te靶后的出射能谱激发样品,得到Cd元素K_α1峰背比为8.28。相较于直接通过原级谱激发样品,Cd元素K_α1峰背比为2.29,其峰背比明显提高但Te元素的散射峰对Cd元素K_α1峰仍然有所影响。选用特征X射线能量与Cd元素K_α1相距更远的BaSO₄作为荧光靶材料,可减弱由于样品中的基体轻元素的散射作用而引起目标元素的峰背比降低情况,可将Cd元素K_α1峰背比提高至14.179。通过增大X光管管电压可进一步提高激发效果,在管电压为70 kV时对于Cd元素有最佳激发效果,峰背比为21.431。     

ICP-AES法测定钕铁硼永磁材料中常量元素

研究了等离子发射光谱法 (ICP AES)直接测定钕铁硼永磁材料中常量元素Nd ,Fe,B的方法。选择了合适的分析线 ,采用基体匹配法消除样品中基体元素的干扰。详细讨论了ICP AES法测定硼的“记忆效应”及其消除方法。以多点 (3个点 )标准曲线法减小测定的误差。本方法已应用于钕铁硼产品的快速检验 ,样品中Nd ,Fe,B含量测定的相对标准偏差分别为 0 6 2 % ,0 5 6 % ,0 90 %     

ICP-AES法测定人血清中的硒

采用消化法预处理血清样品 ,并用ICP AES法测定样品中的Se ,同时 ,探索Fe的存在对测定的干扰情况以及干扰的消除方法。结果表明 ,Se的检测限为 0 0 0 76μg·mL- 1 ,加标回收率为 91 6 % ,1 0次测定的RSD(n =1 0 )为 2 1 4 7% ;在样品中加入KOH ,可以大大降低Fe对Se测定的干扰。     

电感耦合等离子体发射光谱法测定食用菌中微量元素的方法研究

采用高压硝化罐在较低温度下进行缓慢样品消化,减少了消化过程中微量元素的损失。采用电感耦合等离子体发射光谱法测定了食用菌中Ca,Na,K,Mg,Mn,Ba,Fe,Co,Ge和Cu等多种微量元素的含量。高压硝化罐法测定各元素的相对标准偏差在0·16%～2·86%之间,湿法测定各元素的相对标准偏差在0·33%～3·49%之间。可见高压硝化罐法处理样品的测量精密度和湿法处理样品的测量精密度均比较好,前者的测量精密度更高一些。对高压硝化罐法和湿法处理样品的测量结果进行了t检验,t值在0·0024～2·473,均小于t0·99,9(3·25),说明两种方法的测量结果无显著性差异,即两种方法不存在系统误差。同时,高压硝化罐法处理样品的回收率在96·6%～103%之间,该方法具有简便、快速、灵敏、稳定、准确等优点,适于食用菌中微量元素的分析测定。     

平面薄膜靶激光等离子体消融参量的测量

报道了使用1ns脉冲宽度钕玻璃大功率激光以P偏振及S偏振方式辐照倾斜的平面聚脂薄膜靶,用离子法测量比质量消融率、消融压力及流体动力学转换效率等参量的实验结果。靶面激光辐照强度为2×10~(12)W·cm~(-2)～1×10~(14)W·cm~(-2)。比较了实验和理论给出的定标规律。初步讨论了P偏振及S偏振两种入射情况下,消融参数及薄膜靶背面收集到的离子信号波形的差异。     

原子吸收光谱法测定冬凌草中的矿物元素

用原子吸收光谱法测定冬凌草中影响人体健康的8种矿物元素Cu、Zn、Fe、Mn、Ca、Mg、Se和Pb的含量。样品经硝酸-高氯酸消解后,采用偏振塞曼效应扣除背景吸收,用火焰原子吸收光谱法检测积分吸收测定冬凌草中Cu、Zn、Fe、Mn、Ca和Mg的含量,用石墨炉程序升温原子吸收光谱法检测峰值吸收测定Se和Pb含量。测定结果显示:该方法的精密度RSD为1.22%—5.64%;加标回收率为95.0%—110.5%;8种矿物元素的检出限(P=95%,α=0.5)分别为Cu0.034、Zn0.0028、Fe0.031、Mn0.110、Ca0.367、Mg0.132mg·mL-1,Pb1.40μg.L-1和Se1.86μg.L-1。该方法简便快速、灵敏、准确,适用于中药冬凌草中矿物元素含量的测定。     

原子吸收光谱法测定血清中不同化学形态的铜、铁、锌

融合分子生物学技术与原子吸收光谱对血清中元素铜、铁和锌的化学形态进行研究。用60%乙醇低温(4℃)沉淀血清蛋白的方法将血清中的铜,铁,锌分为结合态和非结合态,原子吸收分光光度计分别测定血清中Cu,Fe和Zn三种元素的总量及非结合态含量,通过减差法求出血清中结合态元素含量,从而建立了Cu,Fe和Zn元素这两种化学形态的分离分析方法,并讨论了有关的实验条件。该方法铜、铁和锌的检出限分别为9·84×10-3μg·mL-1,2·76×10-2μg·mL-1,1·06×10-3μg·mL-1,相对标准偏差为0·30%～2·31%,回收率为95·0%～104·0%。该法已应用于SD大鼠血清中Cu,Fe和Zn三种元素不同化学形态的测量。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.