硫化氢在金属-有机骨架材料中吸附与分离的计算模拟

摘 要: 采用优化的DREIDING力场参数，通过巨正则系综蒙特卡洛(GCMC)模拟方法对天然气中的两种气体CH4和H2S在Cu6(BTTC)4(H2O)6·xS (1)和[(CH3)2NH2]3[(Cu4Cl)3(BTTC)8]·yS (2)两种金属有机骨架(MOFs)材料中的吸附与分离性能进行了比较研究.结果证明了聚合物2的吸附量和分离性能相比之下高于聚合物1，且两种材料的吸附机理存在差异，聚合物1中金属Cu和有机基团对于吸附两种气体没有明显的作用，主要分布在小孔道和大孔道；然而聚合物2中H2S和CH4主要吸附在有机基团、金属Cu和-Cl基团周围.则含有-Cl基团的聚合物2展现了优越的吸附能力和稳定性.总而言之，本文获得的结果可以应用于此类研究领域，因此在环境范围中吸附去除污染物可以产生更深层次定性和定量的作用.     

基于第一性原理计算H_2S、CO_2、CH_4在Fe-MoS_2上的吸附性能

在高含硫气藏开发中,伴随着CH_4的采出,H_2S和CO_2也不可避免的被采出.这两种气体会产生管道腐蚀和气体中毒等诸多不利影响.为了解决这一现实需要,从研究较为广泛的MoS_2材料入手,考虑了其掺杂结构中的吸附性能的变化,相关计算原理基于密度泛函数理论.主要计算了一种吸附式掺杂过渡金属原子Fe在MoS_2上的结构,同时也计算了H_2S,CO_2,CH_4气体在其表面的吸附能,电荷转移,电子密度差等相关参数.结果表明,CH_4对这种材料表现出不敏感的特性,而CO_2、H_2S均表现出吸附的性质,预测这种材料可能作为一种可使用的吸附材料,或是开发作为一种新型的气体预警材料.     

沸石分子筛对CH_4/H_2的吸附与分离性能

基于分子模拟的高通量计算方法,通过对199个沸石结构特征和吸附分离性能之间的关联性研究,发现具有超微孔结构的沸石材料对CH_4分子有良好的吸附分离性能,等摩尔CH_4/H_2混合组份的CH_4吸附选择性和单组份的CH_4吸附量之间存在明显的线性关系.通过使用巨正则蒙特卡罗模拟方法,获得了 3个孔道形沸石对CH_4和H_2的吸附等温线和等量吸附热等物理量.结果表明在相同外界环境下,孔道形沸石的孔结构(表面积和孔体积)对CH_4吸附量的影响高于能量效应(吸附热).结合甲烷蒸汽重整制氢的工业背景,进一步研究了 CH_4/H_2混合体系在不同组份下的分离选择性能,结果表明,超微孔沸石材料对CH_4的吸附选择性与体相压力和进料比无关.通过气体分子的质心分布密度发现,CH_4在孔道形沸石中优先占据更小孔窗的空间,而H_2的分布范围更大但是未存在明显的优先吸附位点.     

人工金刚石薄膜生长过程中有关反应活性的研究

用原子簇团模拟人工金刚石膜生长过程中的一些生长核,采用从头自治的DV-X_n方法对这些簇团和与生长过程有关的一些气相分子和基团(CH,CH_2,CH_3,·CH_3,CH_4·H,C_2H,C_2H_2,C_2H_4)进行了电子结构计算,从化学反应活性的角度探讨金刚石膜生长过程中这些气相分子和基团与生长核的反应活性,结果表明,CH,CH_2,CH_3,CH_4·H和变形的C_2H_2更易于与金刚石表面发生化学吸附。另外,通过分析簇团的电子态密度和前线分子轨道的组成情况,提出了人工金刚石膜生长中生长核长大的 关键词：     

双齿配位过渡金属化合物化学——Ⅱ.化合物(Et_4N)_2[Ni_2(SC_6H_4O)_2(μ-SC_6H_4OH)_2]和(Ph_4P)_2[Ni_3(SCH(CH_3)CH_2S)_4]·2CH_3CN的核磁共振研究(英文)

测定并分析了化合物(Et4_N)_2[Ni_2(SC_6H_4O)_2(μ-SC_6H_4OH)_2]和(Ph_4P)_2[Ni_3(SCH(CH_3)CH_2S)_4]·2CH_3CN的_1H NMR数据,计算了模拟谱,确认它们在DMSO溶液中仍保持原有固体状态的分子结构,它们的抗磁性质得到~(13)C NMR的证实。     

碳纸复合材料导热及吸附分离特性研究

Cu-BTC金属有机骨架是最具潜力的甲烷气体吸附存储材料,然而其具有吸附热高、导热性低的缺陷,制约着材料的实际应用。为了提高Cu-BTC材料的导热性能并保持合理的吸附分离特性,本文制备出了一种Cu-BTC/CuO/Carbon fiber paper多级孔结构材料。实验结果表明,这种多级孔结构材料的导热性是纯Cu-BTC材料的17.64倍;压力为0~100kPa、温度为0℃时,多级孔结构材料的CH_4/H_2分离性能与Cu-BTC接近,CH_4/N_2的吸附分离性能却比纯Cu-BTC材料提高了2.15~2.65倍。     

致密气在α-SiO_2(010)面吸附的第一性原理研究

致密气在砂岩储层中的赋存状态一直是人们研究的热点.为了论证致密气在石英砂岩表面吸附性的强弱,基于密度泛函理论的第一性原理方法,以CH_4分子为主要研究对象,研究了CH_4、C_2H_6、CO_2、N_2分子在α-SiO_2(010)面的吸附性质.结果表明:CH_4、C_2H_6、CO_2、N_2分子在α-SiO_2(010)面的吸附能力从小到大依次为CO_2N_2CH_4C_2H_6,其中CH_4分子在B12位的吸附能最低,为-0.5379 eV,几何结构变化最小,吸附最稳定,是一种物理吸附;烃类气体的吸附性比非烃类的吸附性强;不同高对称位的吸附能变化范围很小,气体在α-SiO_2(010)面的流动性很强;在B12位吸附后,CH_4分子的s态、p态电子密度整体向低能量区域偏移约3.2 eV,而α-SiO_2(010)表面硅原子的电子态密度曲线几乎不变.     

高速精磨冷却液的“化学自锐”产物的研究

一、“化学自锐”产物的初期看法通过实验现已完全证实了三乙醇胺一水体系冷却液在高速精磨中对金刚石磨具存在“化学自锐”作用,我们认为:其产物是[(Cu(N(CH_2CH_2OH)_+3)_4]CO_3,这是基于以下一些考虑:1.铜离子(Cu~(2+))是形成络合物的典型中心离子。2.铜离子可以和某些含有氢氧基的有机     

H,Cl和F原子钝化Cu_2ZnSnS_4(112)表面态的第一性原理计算

采用基于密度泛函理论的第一性原理计算方法系统研究了Cu_2ZnSnS_4体相的晶格结构、能带、态密度及表面重构与H,Cl和F原子在Cu_2ZnSnS_4(112)表面上的吸附和钝化机理.计算结果表明:表面重构出现在以金属原子Cu-Zn-Sn终止的Cu_2ZnSnS_4(112)表面上,并且表面重构使表面发生自钝化;当单个H,Cl或F原子吸附在S原子终止的Cu_2ZnSnS_4(112)表面上时,相比于桥位(bridge)、六方密排(hcp)位和面心立方(fcc)位点,三种原子均在特定的顶位(top)吸附位点表现出最佳稳定性.当覆盖度为0.5 ML时,无论H,Cl还是F原子占据Cu_2ZnSnS_4(112)表面的2个顶位均具有最低的吸附能.以S原子终止的Cu_2ZnSnS_4(112)表面在费米能级附近的电子态主要由价带顶部Cu-3d轨道和S-3p轨道电子贡献,此即表面态.当H,Cl或F原子在表面的覆盖度达0.5 ML时,费米能级附近的表面态降低,其中H原子钝化表面态的效果最佳,Cl原子的效果次之,F原子的效果最差.表面态降低的主要原因在于吸附原子从S原子获得电子致使表面Cu原子和S原子在费米能级处的态密度峰几乎完全消失.     

H_2S/CH_4混合物在石墨烯表面吸附性能的分子动力学模拟

本文采用分子动力学方法研究了常温(300K)条件,不同气相密度下H_2S/CH_4二元混合物在石墨烯表面的吸附性能.讨论了气相密度对气-固界面张力,表面吸附量及吸附选择性的影响,并统计了密度分布,法相及切向压力分布。此外,还讨论了石墨烯表面缺陷对混合物吸附的影响。研究表明H_2S/CH_4二元混合物在石墨烯表面的吸附可视为单分子层吸附;且吸附选择性与气-固界面张力均随着气相密度的增加而增大;H_2S与CH_4均在石墨烯表面缺陷处存在一明显的吸附峰.     

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.     

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.     

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.     

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].     

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.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.