CCK1受体的同源模拟和分子对接研究

采用同源建模法对CCK1受体的三维结构进行了模拟,并采用分子动力学方法对模型进行修正和优化,再采用与训练集激动剂和拮抗剂分子对接的方法分别得到激动状态和拮抗状态CCK1受体的三维结构模型。得到的模型使用DOCK对接软件对训练集中的分子进行对接,所得结果与其实际活性拟合度较好,说明我们建立的激动和拮抗状态下的CCK1受体的三维结构模型比较合理,可以作为化合物虚拟筛选的模型对新化合物进行虚拟筛选。     

煤焦水蒸气气化动力学模型及参数敏感性研究

在热重分析仪上对小龙潭煤焦、府谷煤焦和晋城煤焦水蒸气气化过程进行了研究。使用收缩核模型、混合模型和随机孔模型模拟了三种煤焦水蒸气气化反应过程。结果表明,混合模型总体上模拟效果最好,收缩核模型和随机孔模型对低变质程度的小龙潭煤焦气化过程模拟效果不佳,但是适用于模拟另外两种煤阶较高的煤焦气化过程。求解了三种模型的动力学参数,并分析了不同模型参数出现差异的原因。同时,采用敏感性分析法定量研究了模型中的参数发生偏差时引起模型误差的大小,并通过比较发现反应速率常数k为敏感性因素,而混合模型中反应级数n和随机孔模型中孔结构参数ψ为非敏感性因素。     

一种热解炭在金属钠中的相变

通过酚醛树脂的裂解和碳化所形成的热解炭与金属钠在氩气保护气氛中加热, 得到一种无定形碳在常压和较低温度下进行石墨化的方法, 并研究了热解炭在金属钠熔体中的相变. 对所得样品用X射线粉末衍射(XRD)、光散射拉曼光谱、透射电子显微镜(TEM)以及Brunauer-Emmett-Teller (BET)法氮气吸附进行表征与分析. 结果表明: 热解炭在金属钠熔体中于800 °C加热24 h, 发生明显的石墨化; 于900 °C加热24 h, 所得样品的石墨化度为40%, 石墨化碳的平均厚度约为40 nm, 孔结构由微孔转变为介孔. 探讨了金属钠在无定形碳中的渗透扩散导致其相变的原因.     

溶剂浓度对PVDF相转换膜大孔结构的影响

提出决定大孔能否发展的初始分相点处溶剂浓度临界点的概念 ,认为初始分相点处较高的溶剂浓度有利于大孔的发展 ,溶剂浓度低于一定的界限后 ,大孔停止发展 ,转为海绵状结构 .实验考察了不同凝胶液组成下制得的PVDF中空膜的结构 ,建立了相应的传质模型 ,模拟不同制膜条件下初生态膜内的组成分布情况 ,根据初始分相点处溶剂浓度临界点的概念 ,预测膜的形态结构 .模拟结果与相应制膜条件下的电镜照片有很好的对应关系 ,证明了上述大孔形成机理的正确性 .     

近红外光谱法无损检测平谷产大桃品质方法研究

利用近红外（Near infrared, NIR）漫反射光谱法结合化学计量学定量分析技术开展了平谷产大桃品质的无损检测研究。使用手持式近红外光谱仪采集7个不同品种平谷产大桃的近红外漫反射光谱，采用系统抽样法将其划分为验证集和验证集，结合Savitzky-Golay卷积平滑法（Savitzky-Golay Smoothing, S-G）、标准正态变换法（Standard normal variation, SNV）和多元散射校正法（Multivariate scattering correction, MSC）3种预处理方法以及偏最小二乘回归（Partial least square regression, PLSR）与随机森林（Random forest, RF）两种建模算法，分别建立了大桃中的糖度（Soluble solids content, SSC）、酸度、硬度和水分定量模型。结果表明，非线性RF模型优于线性PLSR模型，对于SSC，一阶导数光谱结合MSC预处理建立的RF模型效果最佳，验证集决定系数（Coefficient of determination,R2）和预测均方根误差...     

模拟气固两相流动非均匀结构的颗粒运动分解轨道模型

针对气固两相流动具有稀密两相非均匀结构的特征 ,将两相流动中颗粒的运动过程进行分解 ,分别处理颗粒 颗粒及颗粒 流体间的两种作用 ,并对影响模拟真实性的空隙率计算提出新的算法 ,从而建立了接近于真实系统的离散型颗粒运动分解轨道模型 .该模型对气固流化床中典型的非均匀结构———鼓泡与节涌现象的模拟结果较已有工作有明显地改进 ,对于气泡破碎方式的模拟也与实验结果吻合 .研究结果表明 :颗粒运动分解轨道模型能够真实地模拟鼓泡流化床中的非均匀流动结构 ,并具有模拟图象真实、算法简单、适用面宽、计算量少的优点 .     

纳米自组装γ-Al_2O_3孔隙结构的核磁共振表征

纳米自组装γ-Al_2O_3具有两种纳米级孔道,可作为适合于大分子扩散的催化剂载体,也可用于页岩气藏模型。表征纳米材料孔隙结构的方法有扫描电镜、氮吸附法及压汞法等,各有局限。本文利用核磁共振弛豫测量对纳米自组装γ-Al_2O_3孔隙结构进行研究和定量表征,并通过核磁共振实验和数值模拟对纳米自组装γ-Al_2O_3表面弛豫强度及孔径分布进行探索。结果表明,数值模拟核磁弛豫表征的纳米自组装γ-Al_2O_3的主体孔径为5-7 nm和30-42 nm,核磁弛豫实验通过误差函数法表征的主体孔径为5-9 nm和29-47 nm。相比于氮吸附仅表征微孔介孔及部分大孔,不能表征大于100 nm孔径,压汞法描述小于10 nm孔径相对不准确等问题,核磁弛豫能够全面表征2.8-315 nm纳米自组装γ-Al_2O_3的双峰孔隙系统。三个样品S-1、S-2、S-3的横向弛豫时间T_2谱小孔大孔波峰的信号幅度比0.603、1.15、1.84直接反映各自的化学小孔大孔氧化铝投料比0.85、1.38、1.7的变化。建立的表征方法可以应用于页岩气微观结构和机理研究中,前景广阔。     

压汞法研究大孔离子交换树脂和大孔吸附树脂的孔结构.V.汞接触角和表面张力

利用压汞法测定多孔径大小及孔分布已是众所周知，而且得到广泛应用。一般情况下，压汞法最常用的是园柱孔模型，实际上，大孔离子交换树脂和大孔吸附树脂的孔道是呈异形孔，表面各处并不均匀。因此，汞与树脂表达的接触角和表面张力是和树脂和孔结构直接相关。     

煤焦在燃烧过程中孔隙结构变化的模拟

煤焦在燃烧过程中的物理特性，如比表面积和孔径分布会发生连续变化，直接测量煤焦在燃烧过程中的孔隙结构变化很困难，但可以通过合适的数学模型来观察，二维的圆柱孔模型已大量用来对煤焦气化与燃烧过程中表面积和孔隙结构的变化进行模拟，这个模型把孔隙分成两大部分－－大孔与小孔，因为小孔构成比表面的绝大部分，所以在反应过程中比表面积的变化可以由单一小孔模型来拟合，本文采用了用Ｔｓｅｎｇ和Ｅｄｇａｒ提出的孔模型对几     

介孔二氧化锆分子筛比表面和孔结构的调变

在非离子表面活性剂PEO作用下，用固态反应结构导向法合成了介孔二氧化锆。根据Zr-O-Zr骨架结构与有机物种键合较弱的特点，使用了溶剂抽提法脱除结构导向剂。结果发现该法所得介孔材料与焙烧法所得结构显著不同，溶剂抽提法所得材料具有丰富的介孔结构，且比表面较高；而焙烧法所得样品为超微孔结构，热稳定性较高，SEM结果表明在较高的焙烧温度下其有序的表观形貌依然存在。     

Molecular modeling of porous carbons using the hybrid reverse Monte Carlo method

We apply a simulation protocol based on the reverse Monte Carlo (RMC) method, which incorporates an energy constraint, to model porous carbons. This method is called hybrid reverse Monte Carlo (HRMC), since it combines the features of the Monte Carlo and reverse Monte Carlo methods. The use of the energy constraint term helps alleviate the problem of the presence of unrealistic features (such as three- and four-membered carbon rings), reported in previous RMC studies of carbons, and also correctly describes the local environment of carbon atoms. The HRMC protocol is used to develop molecular models of saccharose-based porous carbons in which hydrogen atoms are taken into account explicitly in addition to the carbon atoms. We find that the model reproduces the experimental pair correlation function with good accuracy. The local structure differs from that obtained with a previous model (Pikunic, J.; Clinard, C.; Cohaut, N.; Gubbins, K. E.; Guet, J. M.; Pellenq, R. J.-M.; Rannou, I.; Rouzaud, J. N. Langmuir 2003, 19 (20), 8565). We study the local structure by calculating the nearest neighbor distribution, bond angle distribution, and ring statistics.     

Adsorption, structure and dynamics of benzene in ordered and disordered porous carbons

Molecular simulations are used to study the adsorption, structure, and dynamics of benzene at 298 K in atomistic models of ordered and disordered nanoporous carbons. The ordered porous carbon is a regular slit pore made up of graphene sheets. The disordered porous carbon is a structural model that reproduces the morphological (pore shape) and topological (pore connectivity) disorder of saccharose-based porous carbons. As expected for pores of a regular geometry, the filling occurs at well-defined pressures which are an increasing function of the pore width H. In contrast, in qualitative agreement with experimental data for activated carbon fibers, the filling of the disordered carbon is continuous and spans over a large pressure range. The structure and dynamics of benzene in the disordered carbon also strongly depart from that for the slit pore geometry. While benzene in the slit graphite nanopores exhibits significant layering, benzene in the disordered porous carbon exhibits a liquid-like structure very close to its bulk counterpart. Both the ordering and self-diffusivity of benzene in the graphite nanopores depend in a complex manner on the pore width. The dynamics is either slower or faster than its bulk counterpart; our data show that the self-diffusivity decreases as the number of confined layers n divided by the pore width H increases (except for very small pore sizes for which benzene crystallizes and is necessarily slower than the liquid phase). The dynamics of benzene in the disordered porous carbon is isotropic and is much slower than that for the graphite slit nanopores (even with the smallest slit nanopore considered in this work). The results above show that the adsorption, structure, and dynamics of benzene confined in disordered porous carbons cannot be described in simple terms using an ideal model such as the slit pore geometry.     

RMC_POT: A computer code for reverse monte carlo modeling the structure of disordered systems containing molecules of arbitrary complexity

An approach has been devised and tested for preserving the molecular dynamics molecular geometry taking into account energetic considerations during Reverse Monte Carlo (RMC) modeling. Instead of the commonly used fixed neighbor constraints, where molecules are held together by constraining distance ranges available for the specified atom pairs, here molecules are kept together via bond, angle, and dihedral potential energies. The scaled total potential energy contributes to the measure of the goodness‐of‐fit, thus, the atoms can be prevented from drifting apart. In some of the calculations (Lennard‐Jones and Coulombic) nonbonding potentials were also applied. The algorithm was successfully tested for the X‐ray structure factor‐based structure study of liquid dimethyl trisulfide, for which material now significantly more sensible results have been obtained than during previous attempts via any earlier version of RMC modeling. It is envisaged that structural modeling of a large class of materials, primarily liquids and amorphous solids containing molecules of up to about 100 atoms, will make use of the new code in the near future. © 2012 Wiley Periodicals, Inc.     

Efficient simultaneous reverse Monte Carlo modeling of pair-distribution functions and extended x-ray-absorption fine structure spectra of crystalline disordered materials

An efficient implementation of simultaneous reverse Monte Carlo (RMC) modeling of pair distribution function (PDF) and EXAFS spectra is reported. This implementation is an extension of the technique established by Krayzman et al. [J. Appl. Cryst. 42, 867 (2009)] in the sense that it enables simultaneous real-space fitting of x-ray PDF with accurate treatment of Q-dependence of the scattering cross-sections and EXAFS with multiple photoelectron scattering included. The extension also allows for atom swaps during EXAFS fits thereby enabling modeling the effects of chemical disorder, such as migrating atoms and vacancies. Significant acceleration of EXAFS computation is achieved via discretization of effective path lengths and subsequent reduction of operation counts. The validity and accuracy of the approach is illustrated on small atomic clusters and on 5500-9000 atom models of bcc-Fe and α-Fe(2)O(3). The accuracy gains of combined simultaneous EXAFS and PDF fits are pointed out against PDF-only and EXAFS-only RMC fits. Our modeling approach may be widely used in PDF and EXAFS based investigations of disordered materials.     

多孔碳材料的制备

多孔碳材料不仅具有碳材料化学稳定高、导电性好等优点,由于多孔结构的引入,还具有比表面积高、孔道结构丰富、孔径可调等特点,在催化、吸附和电化学储能等方面都得到了广泛的应用。本文综述了微孔、介孔、大孔及多级孔碳等多孔碳材料的最新研究进展,重点介绍了多孔碳孔道结构的调控,并对多孔碳材料的应用进行了展望。     

Fullrmc,a rigid body reverse monte carlo modeling package enabled with machine learning and artificial intelligence

A new Reverse Monte Carlo (RMC) package “fullrmc” for atomic or rigid body and molecular, amorphous, or crystalline materials is presented. fullrmc main purpose is to provide a fully modular, fast and flexible software, thoroughly documented, complex molecules enabled, written in a modern programming language (python, cython, C and C++ when performance is needed) and complying to modern programming practices. fullrmc approach in solving an atomic or molecular structure is different from existing RMC algorithms and software. In a nutshell, traditional RMC methods and software randomly adjust atom positions until the whole system has the greatest consistency with a set of experimental data. In contrast, fullrmc applies smart moves endorsed with reinforcement machine learning to groups of atoms. While fullrmc allows running traditional RMC modeling, the uniqueness of this approach resides in its ability to customize grouping atoms in any convenient way with no additional programming efforts and to apply smart and more physically meaningful moves to the defined groups of atoms. In addition, fullrmc provides a unique way with almost no additional computational cost to recur a group's selection, allowing the system to go out of local minimas by refining a group's position or exploring through and beyond not allowed positions and energy barriers the unrestricted three dimensional space around a group. © 2016 Wiley Periodicals, Inc.     

Scalable synthesis of macroscopic porous carbon sheet anode for potassium-ion capacitor

Carbon materials hold the great promise for application in energy storage devices owing to their low cost, high thermal/chemical stability, and high electrical conductivity. However, it remains challenging to synthesize high-performance carbon electrodes in a simple, scalable and sustainable way. Here, we report a facile method for scalable synthesis of porous carbon anode by using cheap and easily accessible zeolitic imidazolate framework-8 as a template and polyvinylpyrrolidone as an additiona...     

Molecular Modeling of Adsorption in Activated Carbon: Comparison of Monte Carlo Simulations with Experiment

We present Mont Carlo computer simulation results for a molecular model of fluids adsorbed in porous carbon materials. The model carbon used is based on the platelet model for carbon of Segarra and Glandt (1994). The model we use has a single basal plane per platelet and the structure is isotropic, disordered, with weak short-range correlations between the platelets. We have performed grand canonical Monte Carlo simulations of the adsorption isotherms for methane, ethane, and their mixtures in this model carbon. We find generally good agreement with experimental and the mixture results are quite accurately described by the ideal adsorbed solution theory. An exception to this is the behavior for the mixture at the highest pressures. In this case the experimental data show significant deviations from ideal adsorbed solution theory and the simulation results.