化学战剂的SERS检测及应用前景研究

化学武器和技术的扩散使化学恐怖活动成为事关世界安全的突出问题之一.针对化学战剂的高毒性和快速致命特点,表面增强拉曼散射(SERS)光谱技术研究可以实现生化战剂的快速、高灵敏实时检测,有助于战时和突发恐怖袭击时对人员的及时救治和预防,为更好的防范化学武器威胁和恐怖袭击提供必要的技术保障.本文主要对SERS技术在化学战剂检...     

基于集成最小二乘支持向量机方法的近红外光谱分析

针对近红外（Near Infrared,NIR）光谱测量中的小样本问题。本文提出了一种集成最小二乘支持向量机（Ensemble Least Squares Support Vector Machine,ELS-SVM）新算法。首先使用随机子空间算法（Random Subspace Method,RSM）原始高维变量空间划分为若干个低维度的子空间,然后分别在各个子空间建立最小二乘支持向量机（LS-SVM）模型,最后构造一个集成结果来进行预测。针对一批柴油样本的实验结果表明,本法对柴油十六烷值的预测精度优于传统的LS-SVM方法。     

Structural and spectroscopic properties of small Pun （n= 2-5） molecules

The equilibrium structures and the electronic, spectroscopic and thermodynamic properties of small Pu_n (n=2-5) molecules are systematically investigated using the methods of general gradient approximation (GGA) of density functional theory (DFT). The results show that the bond length of the lowest-energy structure of Pu₂ is 2.578 AA. The ground state structure of Pu₃ is a triangle with D_3h symmetry, whereas for Pu₄, the ground state structure is a square (D_4h) and the spin polarization of 16 for molecule Pu₅ with square geometry (D_4h) is the most stable structure. For the ground state structures, the vibrational spectra as well as thermodynamic parameters are worked out. In addition, the values for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) along with the energy gap of all the Pu_2-5 structures are presented. The relevant structural and chemical stabilities are predicted.     

Theoretical studies on the structural, electronic, and optical properties of Ag2HgSnSe4

We investigate the electronic structure of Ag₂HgSnSe₄ in a wurtzite-stannite structure with the first principles method. This crystal is a direct band-gap compound. In addition the dielectric function, absorption coefficient, reflectivity, and energy-loss function are studied using the density functional theory in the generalized gradient approximation. We discuss the optical transitions between the valence bands and the conduction bands in the spectrum of the imaginary part of the dielectric function at length. We also find a very high absorption coefficient and a wide absorption band for this material. The prominent structures in the spectra of reflectivity and the energy-loss function are discussed in detail.     

Short range order transformation and magnetostriction of Fes3Ga17 ribbons

The relationship between magnetostriction and structure of melt-spun Fes3Ga17 ribbons are investigated by XRD and M5ssbauer spectrum technique （MS）. As the heat-treatment temperature increases from 650℃ to 800℃, the magnetostriction coefficient of Fes3Ga17 ribbon first increases and then decreases. The largest magnetostriction coeiffcient （-578.4 ppm） is achieved in those specimens quenched at 750oc. According to the XRD and MSssbauer spectrum anal- ysis, a small quantity of DO3 phase is precipitated in Fe83Ga17 ribbons when quenched from 650℃ and the DO3 phase is gradually transformed into B2-1ike phase if quenched at higher temperature. However, both DO3 and B2-1ike phases disappear when the temperature increases up to 800℃. From this point of view, B2-1ike phase might be beneficial to the enhancement of magnetostrictive properties of melt-spun ribbons.     

Transmission-mode GaN photocathode based on graded Al_xGa_(1-x)N buffer layer

We create a GaN photocathode based on graded Alx Ga1-x N buffer layers to overcome the influence of buffer-emission layer interface on the photoemission of transmission-mode GaN photocathodes.A gateshaped spectral response with a 260-nm starting wavelength and a 375-nm cut-off wavelength is obtained.Average quantum efficiency is 15% and short wavelength responses are almost equivalent to long wavelength ones.The fitted interface recombination velocity is 5×104 cm/s,with negligible magnitude,proving that the design of the graded buffer layers is efficient in obtaining good interface quality between the buffer and the emission layer.     

High sensitivity and high selectivity terahertz biomedical imaging

We demonstrate two distinct emerging terahertz (THz) biomedical imaging techniques.One is based on the use of a new single frequency THz quantum cascade laser and the other is based on broadband THz time domain spectrocopy.The first method is employed to derive a metastasis lung tissue imaging at 3.7 THz with clear contrast between cancerous and healthy areas.The second approach is used to study an osseous tissue under several imaging modalities and achieve full THz spectroscopic imaging based on the freque...     

Diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate content in lube base oils in terahertz regime

We investigate the diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate (ZDDP) mixed with lube base oil (LBO) at different concentrations using terahertz time-domain spectroscopy (THzTDS).When the concentration exceeds 6.78%,the characteristic absorption peaks exhibit significantly shift,and the absorption coefficient peak value is nonlinear against concentration.Moreover,the absorption coefficients of mixed samples follow the Beer’s law at a concentration below 6.78%.The quantitative analysis enables a strategy for monitoring the formulation of lubricating oil in real time.     

Modeling the THz spectrum of the bentazon

Terahertz (THz) spectra of bentazon are determined within the range of 0.3 2.4 THz at room temperature.Density functional methods are used to compute the THz spectra using three different programs:Gaussian03 for isolated-molecule form,DMol 3 and CRYSTAL09 for solid-state forms.Among the three,the computed THz spectrum of CRYSTAL09 shows better bond length and angle agreements with Xray experimental results,and corresponds with observed THz experiment spectral characteristics.The isolated-molecule vibrational mode values are less by half than those derived from solid-state calculations.The last five peak positions of the two solid-state computations coincide with each other.Moreover,all the experimental THz absorption peaks are assigned by utilizing CRYSTAL09.     

液晶光谱成像技术研究进展

液晶光谱成像技术是基于液晶可调滤光片的新型光谱成像技术.利用向列相液晶材料的电控双折射效应,液晶可调滤光片可在工作谱段内进行连续光谱调谐,实现光谱成像系统的小型化、多用途、实时控制.获取高空间分辫率和高光谱分辫率的光谱图像,是今后航天航空遥感的一个重要发展方向.结合液晶光谱成像技术的国内外研究进展,分析了其目前存在的主...