过渡金属Co2+离子掺杂ZnS硫化物纳米晶制备与中红外发光特性研究

利用不含有机相的简单水热法制备了Co^2+∶ZnS纳米晶,纳米晶具有立方闪锌矿结构,平均晶粒尺寸约为8.3 nm,在808 nm激光泵浦下具有2~5μm波段的中红外荧光发射,中心波长位于3400 nm和4700 nm,分别对应Co^2+离子的4T2(F)→4 A 1(F)和4T1(F)→4T2(F)的能级跃迁.进一步将制备的纳米晶在还原气氛下进行800℃热处理,获得立方闪锌矿和纤锌矿混合晶型的纳米晶,平均晶粒尺寸增大到22.5 nm左右,热处理后的纳米晶表面羟基含量更低,中红外荧光发射强度显著提高.该Co^2+∶ZnS纳米晶的制备方法简单、在制备过程中不引入有机相等荧光淬灭中心,同时证明通过后热处理过程可以进一步减少表面缺陷及羟基含量,使荧光强度得到大幅提升.     

用于高功率系统的掺镱石英光纤研究进展及发展趋势

掺镱石英光纤是掺镱光纤激光器及放大器的重要基础元件.掺镱光纤性能提升是促进掺镱光纤激光器系统功率进一步攀升的关键.本文回顾了高功率掺镱光纤激光器系统功率攀升情况及功率限制性问题,简述了针对激光功率攀升的瓶颈问题所提出的改善性方案.重点阐述了掺镱光纤制备技术、光纤材料、结构性设计在改善功率限制性方面所取得的研究进展,并对未来掺镱石英光纤的研究及发展趋势进行了展望.     

中红外7×1硫化物光纤合束器的设计与制备

硫化物光纤合束器可以实现对多个中红外光源(2～5μm)的功率组合和光谱扩展,基于自研As₂S₃多模光纤,使用低温熔融拉锥技术制备得到7×1中红外光纤合束器,分析了拉锥区域的损耗产生机理,并表征和评估了合束器的传输效率和光束质量。实现了输入光纤合束端与输出光纤的高质量熔接(熔接点损耗低至0.45 dB,抗拉张力超过300 g),合束器平均传输效率约为80%,单通道最高输出功率为4.32 W,表现出了优良的传输特性和功率承载能力。     

Spectroscopic properties of Yb~(3+)-doped TeO_2–BaO–BaF_2–Nb_2O_5-based oxyfluoride tellurite glasses

A series of oxyfluoride glasses with the compositions of 75 mol% TeO2, 10 mol% Nb2O5,(15 mol%-x) BaO, x BaF2(x = 0 mol%, 5 mol%, 10 mol%, 15 mol%) doped with Yb2O3 were prepared by the melt-quenching method. Their emission cross-sections, fluorescence lifetimes, and gain properties were investigated by using the absorption spectra and the fluorescence decay curves. The results show that by substituting BaF2 for BaO, the emission cross-section decreases from 1.37 pm2 to 1.21 pm2, and the fluorescence lifetime increases from 0.71 ms to 0.96 ms. These properties indicate that this oxyfluoride tellurite glass may have potential uses as the Yb2O3-doped gain medium in a solid laser.     

黑胸大蠊浓核病毒基因组末端序列测定与分析

利用构建的黑胸大蠊浓核病毒(PfDNV)全基因组重组质粒(PfDNV-pUC119)以及一系列完整缺失克隆,通过全自动测序方法完成了PfDNV两末端各728 bp 和730 bp 核苷酸序列的测定. 通过计算机软件分析发现,PfDNV 末端201nt为倒置重复序列,其中最末端122nt为回文序列,能形成典型的发夹结构. 并与同科其它病毒末端序列进行了核苷酸序列同源性比较.     

Structural evolution study of additions of Sb_2S_3 and CdS into GeS_2 chalcogenide glass by Raman spectroscopy

The structures of pseudo-binary GeS_2–Sb_2S_3, GeS_2–CdS, Sb_2S_3–CdS, and pseudo-ternary GeS_2–Sb_2S_3–CdS chalcogenide systems are systematically investigated by Raman spectroscopy. It is shown that a small number of [S_3Ge–GeS_3]structural units(SUs) and-S-S-/S8 groups exist simultaneously in GeS_2 glass which has a three-dimensional continuous network backbone consisting of cross-linked corner-sharing and edge-sharing [GeS_4] tetrahedra. When Sb_2S_3 is added into GeS_2 glass, the network backbone becomes interconnected [GeS_4] tetrahedra and [SbS_3] pyramids. Moreover, Ge atoms in[S_3Ge–GeS_3] SUs tend to capture S atoms from Sb_2S_3, leading to the formation of [S_2Sb–SbS_2] SUs. When CdS is added into GeS_2 glass, [Cd_4GeS_6] polyhedra are formed, resulting in a strong crystallization tendency. In addition, Ge atoms in[S_3Ge–GeS_3] SUs tend to capture S atoms from CdS, resulting in the dissolution of Ge–Ge bond. Co-melting of Sb_2S_3 or CdS with GeS_2 reduces the viscosity of the melt and improves the homogeneity of the glass. The GeS_2 glass can only dissolve up to 10-mol% CdS without crystallization. In comparison, GeS_2–Sb_2S_3 glasses can dissolve up to 20-mol% CdS,implying that Sb_2S_3 could delay the construction of [Cd_4GeS_6] polyhedron and increase the dissolving amount of CdS in the glass.     

Planar waveguides in neodymium-doped calcium niobium gallium garnet crystals produced by proton implantation

In this work, the fabrication and optical properties of a planar waveguide in a neodymium-doped calcium niobium gallium garnet(Nd:CNGG) crystal are reported. The waveguide is produced by proton(H~+) implantation at 480 ke V and a fluence of 1.0×10~(17) ions/cm~2. The prism-coupling measurement is performed to obtain the dark mode of the waveguide at a wavelength of 632.8nm. The reflectivity calculation method(RCM) is used to reconstruct the refractive index profile. The finite-difference beam propagation method(FD-BPM) is employed to calculate the guided mode profile of the waveguide.The stopping and range of ions in matter 2010(SRIM 2010) code is used to simulate the damage profile induced by the ion implantation. The experimental and theoretical results indicate that the waveguide can confine the light propagation.     

利用二维属性直方图的最大熵的图像分割方法

提出二维属性直方图的概念。它是一种由先验知识约束的二维直方图,可以使一些图像处理方法得到简化和变得可行。在此基础上提出一种基于二维属性直方图的图像分割方法。该方法步骤是构造图像的属性集,确定相应的二维属性直方图,然后利用二维属性直方图的最大熵法确定灰度阈值。为了说明该方法的性能,将其用于一种海底小目标图像分割。同时,也使用一维属性直方图的最大熵分割法。结果表明该方法比一维属性直方图的最大熵法抗干扰性更强,分割效果更好。二维属性直方图的概念具有理论意义与应用价值。该方法适用于图像有某种先验知识的场合。     

固相萃取-高效液相色谱法同时测定羊肉制品中9种杂环胺

建立了同时测定羊肉制品中9种杂环胺的固相萃取-高效液相色谱(SPE-HPLC)分析方法。样品经2 mol/L NaOH超声提取、80 mL二氯甲烷液-液萃取,利用阳离子交换柱(MCX柱)净化和富集后进行HPLC分析。采用反相C18色谱柱,以乙腈和0.01 mol/L磷酸溶液(用三乙胺调整pH 3.6)为流动相对杂环胺进行梯度洗脱,使用二极管阵列检测器(DAD)分别在228 nm(2-氨基-9H-吡啶并［2,3-b］吲哚(AaC)、2-氨基-3-甲基-9H-吡啶并［2,3-b］吲哚(MeAaC))、253 nm(2-氨基-3-甲基咪唑并［4,5-f］喹啉(IQ)、1-甲基-9H-吡啶并［3,4-b］吲哚(Harman)、2-9H-吡啶并［3,4-b］吲哚(Norharman))、263 nm(2-氨基-3,8-二甲基咪唑并［4,5-f］喹喔啉(MeIQx)、2-氨基-3,4,8-三甲基咪唑并［4,5-f］喹喔啉(4,8-DiMeIQx)、3-氨基-1-甲基-5H-吡啶并［4,3-b］吲哚(Trp-p-2))、321 nm(2-氨基-1-甲基-6-苯基咪唑并［4,5-b］吡啶(PhIP))处进行检测。实验结果表明,9种杂环胺分离效果良好,回收率为50.27%～94.77%(n=6),相对标准偏差为0.08%～4.42%;通过全波长扫描,确定检出限(以信噪比(S/N)=3计)为1.6～41.0 μg/L。该方法操作简单,结果准确,重现性好,可用于同时检测羊肉制品中9种杂环胺的含量。     

KDP晶体单点金刚石飞切过程裂纹扩展影响因素研究

针对KDP晶体在单点金刚石飞切过程中承受周期性的断续冲击,易于产生裂纹,而常规有限元方法无法准确模拟裂纹尖端扩展路径等问题.以扩展有限元理论为基础,在ABAQUS中建立KDP晶体数值模型,研究刀具参数和工作参数对裂纹尖端扩展的综合影响作用.结果表明:主轴转速与切深对飞切过程中裂纹尖端扩展在0.1水平下呈显著性影响,而工作台进给量对裂纹尖端扩展的影响作用最小;裂纹尖端最大主应力值和扩展趋势随着主轴转速的提升而逐渐增大,其中在600 r/min至800 r/min区间内增长速度最快;裂纹尖端最大主应力值和扩展趋势随着切深的增加而增大,且切深小于25 μm时的增长速度要高于切深大于25 μm时的增长速度.