含能双环HMX衍生物分子设计的密度泛函研究（英文）

运用DFT-B3LYP/6-311G(d,p)方法,计算了所设计的三种双环HMX(2,4,6,8-四硝基-2,4,6,8-四氮杂双环[3.3.0]辛烷)衍生物分子.基于理论晶体密度和固态生成热计算衍生物分子的爆轰性能;通过前线轨道能与特征高度(h_(50))评价衍生物分子的感度.结果表明,理论晶体密度均高于1.90 g·cm~(-3),爆速高于9.0 km·s~(-1),爆压约为40 GPa.三种双环HMX衍生物分子是潜在的高能量密度材料.     

β-1,3,5,7-四硝基-1,3,5,7-四氮杂环辛烷热膨胀各向异性的量子化学计算与分子动力学模拟

在303～383 K和NPT系综和COMPASS力场下对β-1,3,5,7-四硝基-1,3,5,7-四氮杂环辛烷(HMX)超晶胞初始结构的分子动力学模拟,得到常压下各温度的晶体平衡构型并发现分子的堆积方式不变;通过线性拟合求算出线膨胀系数与实验值相近,体现出明显的各向异性. 采用密度泛函理论方法对沿各晶轴方向膨胀率变化(100%～105%)的HMX单胞模型进行了总能计算,得到的能量变化率体现各向异性并与热膨胀系数值关联,建立了关联方程. 由此阐 释了HMX晶体热膨胀各向异性的本质即特定的分子堆积模式.     

HMX不同晶型热膨胀特性及相变的ReaxFF分子动力学模拟

HMX（octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine）晶体不同晶型对温度的响应对于深入认识含能材料在外加载荷下的感度、稳定性、相变等具有重要意义．采用ReaxFF—lg势函数和等温等压分子动力学（NPT-MD）方法,研究了β-,δ-和α-HMX三种固态晶型在T=303—503K内的晶体结构和分子结构．结果表明,ReaxFF—lg势函数能够合理地描述HMX晶体的热膨胀行为,计算得到的晶体结构和热膨胀系数与实验数据比较符合．三种晶型的线膨胀系数表明,β-HMX晶体具有明显的热膨胀各向异性;δ-HMX晶体C轴的热膨胀特性与a,b轴略有不同;α-HMX晶体三个方向的热膨胀特性基本相同．三种晶型的体膨胀系数为8-HMX〉α-HMX〉β-HMX,表明δ-HMX晶体对温度最敏感,这可能是δ-HMX晶体具有更高感度的原因．在T=443K时,β-HMX晶体的晶胞参数突变,且部分分子构型由“椅式”转变为“船式-椅式”．采用两相热力学模型（2PT）得到的亥姆赫兹自由能表明,β—HMX晶体在T=423—443K时发生相变．β-,δ-和α-HMX晶体分别在T=303—423K,T=443—503K和T=363-423K内稳定存在．     

HMX与含硼化合物相互作用的理论计算

在PBX体系中加入合适的键合剂通常能改善HMX与高聚物的界面作用.为了预测其界面作用强度及粘合效果,本文采用B3LYP密度泛函方法和6-31G*基组计算HMX与含硼化合物BR1R2R3的相互作用.优化得到了存在B…O相互作用的HMX…BR1R2R3复合物的几何构型.计算结果表明,HMX…BH3和HMX…BH2(CH3)中的B与O原子间相互作用强,二者分子间相互作用能在MP2/6-31 G**//B3LYP/6-31G*水平上分别为-65.3 kJ/mol和-40.2 kJ/mol.由于空间位阻效应HMX中的O原子与BH(CH3)2、B(CH3)3和B(OH)(CH3)(CH2NH2)中的B原子距离大于3.理论计算结果与实验结果基本一致.     

吐昔烯衍生物分子的电子光谱与非线性光学性质北大核心CSCD

采用含时密度泛函理论（TDDFT）B3LYP对5个吐昔烯及其衍生物分子的吸收光谱进行理论计算．结果表明,该5个分子的吸收波长在281～307nm范围内,属于近紫外区．使用有限场（FF）方法理论计算5个化合物分子的非线性光学（NLO）性质．结果显示,吐昔烯分子引入烷氧基将明显增大二阶和三阶非线性光学性质（β0和Y值）,此类化合物分子的三阶非线性光学性质明显优于二阶非线性光学性质．     

吐昔烯衍生物分子的电荷传输性质

根据爱因斯坦方程和Marcus电荷传输模型, 使用密度泛函理论B3lyp/6-31g^**理论水平计算6 个吐昔烯衍生物分子的结构和电荷传输性质. 结果显示: 6个吐昔烯的衍生物分子的空穴迁移速率为0.018–0.062 cm²·V^-1·s^-1, 电子迁移率为0.055–0.070 cm²·V^-1·s^-1, 其中3, 8, 13-辛烷氧基吐昔烯衍生物分子适合作为双极性传输材料. 三条烷氧基链的吐昔烯衍生物分子上引入三个甲氧基或羟基, 均使空穴和电子传输率降低. 引入给电子基团或共轭性基团可减小吐昔烯衍生物分子的能隙, 达到有机半导体的能隙要求. 关键词： 吐昔烯衍生物 空穴传输 电子传输 有机半导体     

电子传输材料1，3，4-噁二唑衍生物和1，2，4m三唑衍生物的DFT研究

采用密度泛函理论B3LYP方法，对1，3，4-噁二唑衍生物和1，2，4-三唑衍生物两类电子传输材料在中性、阴离子态和阳离子态下分别进行几何结构优化计算．结果表明，1，3，4-噁二唑衍生物的电子传输过程主要是分子内噁二唑上的N→O电子转移，1，2，4-三唑衍生物的电子传输过程主要是分子内三唑上N（双键）→N（单键）以及三唑环向与N相连的苯环电子转移．当其苯环上3位被拉电子基团取代后，其电子传输性能提高；而被给电子基团取代后，电子传输性能降低．     

基于ESIPT机理检测Al3+荧光探针分子结构和电子光谱的理论研究

本文应用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）方法，研究了具有激发态分子内质子转移（ESIPT）特性的3-羟基黄酮（3HF）及其两种氰基和氨基取代衍生物（3HF-CY和3HF-AM）作为水溶液中Al3+离子检测的荧光探针分子结构和电子光谱性质. 计算得到了与ESIPT过程相关的键长、键角以及势能曲线，模拟计算了单独分子和分子@Al3+复合物的吸收和荧光光谱. 结果表明，氰基或氨基的引入均会抑制3HF的质子在基态（S0）或激发态（S1）的转移. 而从得到的吸收光谱可以看出，在3HF中引入吸电子基团氰基可以引起其吸收光谱的红移，而给电子基团氨基的引入则出现相反现象. 此外，与3HF-AM的荧光光谱相比，3HF-AM@Al3+复合物发生了75.88 nm的蓝移，由此推测3HF-AM与水中的Al3+反应后，在光激发下溶液荧光会由绿色转变为紫色，表明3HF-AM分子可以作为有效检测水中Al3+的荧光探针.     

顺式与反式偶氮苯衍生物分子非线性光学性质理论研究

利用密度泛函理论(DFT)B3LYP/6-31G(d,p)方法优化了一系列顺式与反式偶氮苯衍生物分子,在此基础上结合有限场(FF)方法和密度泛函理论对分子非线性光学(NLO)性质及电子光谱进行了计算分析,结果表明:顺式与反式结构的变化对其偶极矩、分子内电荷分布与转移以及前线轨道跃迁都造成影响,从而影响分子的第一超极化率.同时相对于顺式偶氮苯衍生物分子,反式分子具有较大的二阶非线性光学系数.     

HMX炸药爆轰产物物态方程研究

采用自主研制的考虑产物组分间化学反应的类CHEQ程序研究HMX炸药爆轰产物物态方程,给出初始密度为1.90 g·cm^-3的HMX炸药CJ点的爆速和爆压,计算值与实验值符合较好;计算CJ点的爆轰产物组成,并与BKW和LJD的计算结果进行比较分析;同时给出过CJ点的等熵膨胀线上压强、 γ和产物组分随比体积的变化规律,加深对爆轰产物作功能力的认识.     

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.