丙烯酰胺-甲基丙烯酸共聚物结构的NMR研究

用¹H NMR谱,¹³C NMR谱,DEPT谱,gHMQC,gHMBC二维谱和质子弛豫时间等方法研究了在紫外光辐照条件下丙烯酰胺(AM) -甲基丙烯酸(MAA)共聚合反应,讨论了AM-MAA共聚合反应时间与转化率的关系、共聚单体的连接方式、共聚物序列结构以及不同辐照时间下形成的共聚物链运动. 结果表明在紫外光辐照条件下,AM-MAA共聚物链节中同时存在多种连接方式,当反应时间为45 min时,共聚合转化率可达100%. 从自旋-晶格弛豫时间（T₁）和自旋-自旋弛豫时间（T₂）测定中得出,在辐照1小时范围内,时间越长聚合物长链分子运动速度越快,但主链的链段运动变化不明显.     

氯化聚乙烯辐射效应的NMR研究

用¹H NMR,¹³C NMR谱,二维谱,FT-IR等方法研究了氯化聚乙烯（CPE）在室温下限量空气中经⁶⁰Co γ射线辐照后的辐照效应. 结果表明CPE在辐照过程中以发生裂解反应为主,在裂解反应过程中伴随着HCl脱出,HCl的脱出量随着辐照剂量的增加而增加. 辐照后CPE样品的大分子结构发生相应变化,序列结构为CH₂CHClCHClCH₂CHCl,CH₂CH₂CHClCH₂CH₂,CHClCH₂CHClCH₂CH₂,CHClCH₂CHClCH₂CHCl的单元数量减少,但没有形成新的序列结构类型,T₁ 和T₂值给出了有关辐照前后分子运动变化的信息.     

丙烯腈γ辐射聚合的NMR研究

用¹H NMR、¹³C NMR谱、自旋-晶格弛豫时间（T₁）和自旋-自旋弛豫时间（T₂）研究了丙烯腈在⁶⁰Co γ射线辐射聚合后的大分子结构变化与大分子链的运动. 结果表明随着辐射剂量增大，在单体形成聚合物的过程中，聚合物主链上出现了少量的-OH基团，继续增大辐射剂量， -OH部分被氧化. 对聚合物溶液的变温氢谱的研究表明，溶剂中的残余水与上述-OH形成氢键，且随着温度升高氢键被破坏，同时H₂O与-OH之间还存在着质子交换. 利用¹³C NMR谱对丙烯腈辐射聚合的产物进行了序列结构分析. 对T₁和T₂的研究表明，辐射剂量的增大并未影响到聚丙烯腈的链运动，证明了在丙烯腈的辐射聚合过程交联反应未发生.     

紫外光辐照镍系聚丁二烯的NMR研究

用¹H NMR谱,¹³C NMR谱,二维谱,X-射线衍射等方法研究了镍系高顺式聚丁二烯橡胶(NiBR) 在强紫外（UV）光辐照前后的微观结构变化和分子运动情况. 分析表明NiBR样品随着UV光辐照时间的增加,侧链乙烯基端基双键比主链端基双键更易发生氧化反应;并且随着NiBR样品的各基团的半峰宽值逐渐增加,表明NiBR在UV辐照过程中发生了部分交联反应. 样品的X-射线衍射谱图中结晶峰强度随UV光辐照时间的增加逐渐降低,表明样品的晶形无序程度增加了. 自旋-晶格弛豫时间（T₁）和自旋-自旋弛豫时间（T₂）值给出了有关NiBR辐照前后分子运动变化的信息.      

新疆长绒棉辐射效应的谱学研究

用¹³C CP/MAS NMR谱、ESR谱和质子弛豫时间等方法,研究了经γ射线在室温下辐照后新疆长绒棉纤维的辐射效应. 结果表明随着辐照剂量的增加,长绒棉纤维内的自由基浓度明显的增大,并产生了多种自由基的混合物. 由辐照前后的长绒棉纤维的¹³C CP/MAS NMR谱可以得出,随着辐射剂量的增加,C1峰的谱宽趋向增宽,表明了自由基存在的位置. 各类弛豫时间的改变则反映出长绒棉纤维内部聚集态结构和大分子链运动随辐射剂量的变化.     

盐酸氯丙嗪1H NMR、 13C NMR谱的归属及结构表征

通过运用¹H-¹H COSY(¹H-¹H COrrelation SpectroscopY)、TOCSY(TOtal Correlation SpectroscopY)、HSQC(Heteronuclear Single Quantum Correlation)、HMBC (Heteronuclear Multiple Bond Correlation)、NOESY(Nuclear Overhauser Enhancement SpectroscopY)等多种二维核磁技术,对盐酸氯丙嗪（Chlorpromazine hydrochloride CPZ· HCl）在CDCl₃、CD₃COCD₃和D₂O三种溶剂中的¹H、¹³C NMR谱进行了准确归属（重点集中于谱峰重叠程度较高的芳香族区域）．实验表明：杂环上N与苯环存在部分共轭;在CDCl₃、CD₃COCD₃中,侧链卷曲至芳环上方处于屏蔽区,且侧链上N为较稳定的四面体构型;比较了CPZ· HCl在不同溶剂与浓度下的¹H NMR谱的变化,对文献中其核磁共振谱（特别是芳香区的谱峰）归属的争议作了解释．量子化学计算结果与实验结果相吻合．     

卤代甲烷核磁共振谱化学位移的QSSR研究

利用描述电子效应的诱导效应指数（ΣI）、原子的平衡电负性（X_E）和反映核外电子云变形程度的总电子数（Σ_e）、各取代基到中心原子的化学键键长总和（Σ_d）以及各取代基电负性的和差值（ΔX）等参数对45个卤代甲烷化合物中的碳原子结构进行表征,并与其¹³C NMR谱化学位移建立了优良的定量结构-波谱关系模型：δ_Ｃ＝ -7403.8022-47.1765ΣI＋4290.0270X_E－3.3067ΔX－163.4672Σd－4.5153Σe＋22.9851Σe／Σd＋15.2597Σe／X_E－890.2521Σd／X_E．所建多元线性回归方程复相关系数R²及留一法（leave-one-out,LOO）交互验证（cross validation, CV）的复相关系数R²_CV分别为0.09951和0.9950．结果表明所建模型不仅能比现有文献更好地揭示卤代甲烷¹³C NMR谱化学位移与其分子结构信息之间的关系,同时也提供一种计算卤代甲烷¹³C NMR谱化学位移的新方法．     

紫外光辐照聚乙烯醇的1H NMR研究

用¹H NMR谱,自旋-晶格弛豫时间（T₁）和X-射线衍射研究了聚乙烯醇(PVA)在紫外光（UV）辐照后-OH基团与溶剂中残余水质子间氢键的生成与质子交换. 结果表明随着UV光辐照时间的增长,水峰与-OH质子峰逐渐相互靠近,同时水峰逐渐变宽,向低场方向移动,这与-OH基团与溶剂DMSO中残余水的质子之间既有氢键生成又有质子交换有关. 对辐照前后的PVA的DMSO溶液进行变温氢谱的研究,表明随着温度的升高,二者的-OH基团共振峰均逐渐变弱,溶剂残余水峰与-OH基团峰逐渐移向高场. PVA辐照前后随着浓度增大,羟基质子峰“变钝”. 辐照后的PVA的X-射线衍射表明聚集态结构中部分分子间氢键受到了破坏.     

几种高分子材料的域结构、分子动力学和相互作用的固体NMR研究

聚3-羟基丁酸酯(PHB)是微生物细胞在其生长的特定时期在胞内合成的具有相应生物功能的聚羟基烷酸酯类物质, 是一种具有潜在的广泛应用前景的生物可降解的高分子材料. 由于天然的PHB其较高的结晶度和较窄的温度处理范围,它在应用过程中受到较大的局限性. 人们将结构相似的单体3-羟基戊酸(HV)与3-羟基丁酸(HB)共聚形成共聚物(PHBV)以后, 显著改善了PHB的物理机械性能,譬如:冲击强度和韧性有所增加，而硬度脆性有一定程度的下降. 人们虽然在这些降解高分子材料的开发、制备和物理机械性能以及这些材料的应用等方面有很多研究，但是有关分子水平的问题并未得到系统的探索. 因此，针对这些分子基础问题(结构域特征和分子动力学等)做了一些初步的研究.  全氟磺酸树脂(Nafion)是杜邦公司生产的一种燃料电池电极薄膜材料，其较低的使用温度(<100℃)严重地限制了它的应用范围. 人们发现，当把层状硅酸盐(蒙脱土)和Nafion合成为有机无机纳米复合材料之后，在一定程度上提高了它的使用温度. 虽然这种复合材料很容易合成出来并且已经运用到了实际工业应用之中，但是这种热稳定性提高的原因却不甚清楚. 通过固体NMR等分析方法从微观相互作用方面来认识这种宏观性能改善的原因.  使用固体¹³C CP MAS、¹³C SPE MAS NMR以及XRD方法测定了PHB和两种PHBV的结晶度(X_c)，发现随着HV的引入它们的X_c 逐渐减小. 研究同时发现在测量X_c 的这几种方法中¹³C SPE MAS NMR误差较小. 实验中我们利用质子弛豫诱导谱编辑(PRISE)、质子自旋扩散(Spin-diffusion)等固体NMR技术研究了PHB以及不同含量HV的PHBV的结构域特征和相应结构域的运动性. 实验结果表明随着HV含量的增加，它们的非晶相结构域尺寸增大，晶相结构域尺寸减小，可以看出HV的引入导致PHB的结构域特征的变化是其宏观性能改善的原因.  进一步通过低分辨固体NMR测量了PHB和PHBV的变温质子弛豫时间(T₁, T_1ρ, T₂), 然后通过理论拟合获得了它们不同运动状态的分子运动相关频率(τ_c)和分子活化能(E_a)等动力学信息，研究发现随着HV含量的增加，分子运动加快，活化能减小，在分子水平上认识了HV的引入使得PHB宏观性能改善的微观原因.  通过溶胶凝胶法合成了燃料电池电极薄膜(Nafion)和层状硅酸盐(蒙脱土)纳米复合材料来提高Nafion的使用温度，FT-IR和²⁹Si MAS NMR实验结果表明在杂化材料中虽然质子化的十二烷基胺修饰的蒙脱土(MMT)的引入没有导致MMT的骨架结构发生明显变化，而且Nafion也没有插入到MMT的层间，但是TGA分析表明杂化材料中的Nafion的热稳定性比纯的Nafion高. 通过一系列固体NMR技术包括¹⁹F MAS、¹H-¹³C CP MAS NMR和¹H-¹³C HETCOR 2D NMR实验初步证实了这种材料的热稳定性的提高可能是由于MMT表面吸附的NH⁺₃与Nafion侧链上的SO^-₃之间存在较强的静电相互作用，初步可以认为这种相互作用是导致电极材料性能改善的原因.     

超支化高分子桥联聚倍半硅氧烷复合物的NMR研究

以三羟甲基丙烷(TMP)为内核,二羟甲基丙酸(DMP)为支化单元用准一步法合成了重均分子量为12100的第四代端羟基脂肪族超支化聚酯(HBPE-G4),用3-异氰酸酯基丙基三乙氧基硅烷(TPIC)对它进行了端基改性,并以其为桥联剂,与聚倍半硅氧烷(PMSQ)复合制备出超支化高分子桥联聚倍半硅氧烷复合物．利用固体核磁共振(NMR),傅立叶红外(FI-IR),分子纳米粒度分析等方法表征了改性超支化高分子和复合物的结构和反应程度,并通过测量¹³C T₁,¹H T₂,¹H T_1ρ研究了体系中各组分的运动性能,以及超支化高分子与聚倍半硅氧烷之间的相容性．     

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.