NnHn(n=3～7)氮氢化合物的结构质理论研究

本文对53种NnHn(n=3～7)氮氢化合物进行了理论计算,应用自然键轨道理论(Nature Bond Orbital,NBO)和分子中的原子理论(Atoms In Molecules,AIM)分析了化合物的成键特征、相对稳定性.氮原子孤对电子与氮氮键以及氮氮键相互之间的超共轭作用是影响氮氮键长的重要因素.采用原子基团...     

环状氮氢化合物NnHn(n=3~5)的构象研究

应用密度泛函理论对10种环状氮氢化合物异构体进行了研究。利用自然键轨道理论(NBO)和分子中的原子理论(AIM)分析了这些异构体的成键特征、相对稳定性。N-N键长与键临界点的电荷密度存在反比关系。超共轭作用和立体排斥作用计算表明:立体排斥作用和超共轭作用在决定构象稳定性的方面均起了主要的作用。H原子的相对位置的差异影响了键-键立体排斥能的类型。     

环状氮氢化合物NnHn(n=3~5)的构象研究

应用密度泛函理论对10种环状氮氢化合物异构体进行了研究.利用自然键轨道理论(NBO)和分子中的原子理论(AIM)分析了这些异构体的成键特征、相对稳定性.N-N键长与键临界点的电荷密度存在反比关系.超共轭作用和立体排斥作用计算表明:立体排斥作用和超共轭作用在决定构象稳定性的方面均起了主要的作用.H原子的相对位置的差异影响了键-键立体排斥能的类型.     

用分子子图法计算硝基呋咱化合物的生成热

用新的分子子图法计算硝基呋咱类化合物的生成热 ,将呋咱基团视为母体 ,即基子图项 ;硝基、叠氮基、甲基、氰基拆分为一个个原子 ,从原子的角度来分分子子图 ,将碳、氢、氧、氮原子视为取代基 ,即亚子图项 .同时考虑呋咱基团的个数 ,考虑 1位、2位、3位、4位上碳、氢、氧、氮原子及双键、叁键对生成热的影响 ,还考虑不饱和度、总硝基个数、环的个数 (除呋咱环 )、氮氮及氮氧双键的个数对生成热的影响 .用这种新的分子子图编码方法 ,对硝基呋咱化合物的生成热进行了拟合和预估 ,取得了满意的结果 ,其回归方程的相关系数达到了 0 .995 4 .     

腺嘌呤-5-溴尿嘧啶复合物中的卤键

利用从头算和密度泛函理论研究了腺嘌呤(A)-5-溴尿嘧啶复合物中(T+)中的键合模式. 研究结果表明，T+中的Br原子同时与A分子中的氨基氢和氮原子存在弱的相互作用，在这种结合模式中，Br原子与亲核基团H正面结合，同时与亲电基团N侧面结合，分别形成氢键和卤键.静电势分析发现：T+中的Br原子与A中的N7 (或N1)是通过静电相互吸引的. Br与N原子之间的相互作用通过分子中的原子理论得以证实. 关键点的拓扑参数显示卤键是闭壳层相互作用. 自然键轨道分析说明，A中N原子上孤对电子的电荷主要转移到C{Br的反     

氮氢共掺杂金刚石中氢的典型红外特征峰的表征

所有天然Ia型金刚石红外光谱中都存在3107 cm-1特征峰,而在金属触媒直接合成的金刚石红外光谱中没有检测出3107 cm-1特征峰.本文在6.3 GPa,1500?C条件下,通过Fe70Ni30触媒中添加P3N5直接合成出具有3107 cm-1特征峰的氮氢共掺杂的金刚石.红外光谱分析表明,合成的金刚石中氢有两种存在形式:一种对应着乙烯基团C=CH2中C—H键的伸缩振动(3107 cm-1)和弯曲振动(1450 cm-1)的吸收峰,另一种对应着sp3杂化C—H键的对称伸缩振动(2850 cm-1)和反对称伸缩振动(2920 cm-1)的吸收峰.通过分析发现,3107 cm-1吸收峰与金刚石中聚集态的氮原子有关,当金刚石中没有聚集态的氮元素时,即使氮含量高也不会出现3107 cm-1峰;并且2850和2920 cm-1附近的吸收峰比3107 cm-1附近的吸收峰更为普遍存在.这说明sp3杂化C—H键比乙烯基团的C—H键更广泛存在于金刚石中,从两者的峰值看,天然金刚石中的氢杂质主要以乙烯基团C=CH2存在.3107 cm-1吸收峰与聚集态的氮原子的这种存在关系为天然金刚石形成机制的研究提供了一种新思路,同时较低的合成条件也可能为氢与其他元素共掺杂合成具有n型半导体特性的金刚石提供一个较理想的合成环境.     

分子内氮原子上亲核取代反应的理论研究

在MP2(full)/631+G(d,p)理论水平上,以-CHR-(CH2)3-NFCH3(R=H,CH3,CH2CF3,CHO,COCH3)为计算模型,对分子内可能发生的两条反应路径—氮原子上的亲核取代反应及消去反应进行了理论研究.结果表明,当进攻基团-CHR为碱性较强的基团,即R=H、CH3、CH2CF3时,有利于发生消去反应而生成直链化合物R-CH2-(CH2)3N=CH2;而当R为吸电子基团-CHO、-COCH3时,主要发生分子内氮原子上的亲核取代反应,产物为含氮的五员杂环化合物.这些理论预测与已有的实验结果吻合.     

自由基聚合中二硫酯结构及其活性的研究

用密度泛函方法,在B3LYP/6-31G+(d)水平上对三种二硫酯化合物进行了几何构型全优化. 计算了C-S键离解能以及对于自由基的原子自旋密度,并且探讨了它们与化合物活性之间的关系, 分析的结论与实验结论完全一致。同时结论也表明密度泛函理论计算能为C-S键离解能,原子自旋密度变化趋势提供一个很好的预测。     

三乙烯四胺基双(二硫代甲酸钠)及其重金属配合物的光谱研究

采用红外光谱、紫外光谱、原子吸收光谱及元素分析研究了三乙烯四胺基双(二硫代甲酸钠)(DTC-TETA)的结构及其重金属配合物的配位行为。在DTC-TETA的红外光谱图中,在1 461～1 388 cm-1处和1 174～996 cm-1处分别出现含有部分双键性质的CN键和CS键的特征吸收峰;在紫外光谱图中,分别在265和290 nm处出现两个最大吸收峰,分别对应于N…C…S基团的π—π*跃迁和S…C…S基团中硫原子上非键电子向共轭体系的n—π*跃迁;元素分析结果表明该化合物中碳、氢、氮、硫的摩尔比近似为2∶4∶1∶1。在Cu(Ⅱ), Cd(Ⅱ), Zn(Ⅱ), Ni(Ⅱ)配合物的紫外光谱图中分别在紫外区的321, 310, 311, 325 nm处出现新的最大吸收峰。流动注射与火焰原子吸收联用分析结果表明DTC-TETA对铜、镉、镍、锌等重金属离子的络合能力强于二乙基二硫代氨基甲酸钠(DDTC)。     

自由基聚合中二硫酯结构及其活性的研究

用密度泛函方法,在B3LYP/6-31G+(d)水平上对三种二硫酯化合物进行了几何构型全优化.计算了C-S键离解能以及对于自由基的原子自旋密度,并且探讨了它们与化合物活性之间的关系,分析的结论与实验结论完全一致.同时结论也表明密度泛函理论计算能为C—S键离解能,原子自旋密度变化趋势提供一个很好的预测.     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

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.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.