钛在TS—1中的位置及化学结构的理论计算

采用晶格能优化方法ＣＵＬＰ和量子力学从头计算方法对ＴＳ－１中钛在骨架上的位置进行了理论计算,结果表明,钛的取代位置基本是随机的,量子力学从头计算方法对多个ＴＳ－１分子筛碎片模型的计算结果表明钛在ＡＳ－１分子筛骨架中以四面体结构存在,钛硅分子筛在９６０ｃｍ＾－１附近的吸收不应被看作是钛处于分子筛骨架上的依据。     

ZSM-5分子筛中Al的分布及Ga改性对其酸性强度的影响

利用量子化学理论研究了ZSM-5分子筛中骨架Al的分布,计算采用11T簇模型[(HSiO)_3 SiO(H)M(OSiH)_2OSi(OSiH)_3](M=Si,Al,Ga),和B3LYP/6-31G(d)的计算方法,得到了T1,T2,T12位置上的Al/Si,(Al,H)/Si替代能,结果表明11T簇模型中骨架Al优先取代于ZSM-5分子筛中的T12位。采用MP2/6-311++G(3df,2p),计算得到Al/ZSM-5、Ga/ZSM-5分子筛的质子亲和势分别是316.6 kcal/mol,319.4 kcal/mol;B3LYP/6-31G(d)的方法计算吡啶在分子筛及改性分子筛上的吸附能分别是-25.35 kcal/mol和-23.02 kcal/mol。研究结果表明Ga改性ZSM-5分子筛降低了其酸性强度。     

LTA和FAU型分子筛吸附CO2力场的研究

采用巨正则系综的蒙特卡罗法,由通用力场Universal、Pcff、Dreiding和Cvff模拟CO2在LTA(4A和5A)和FAU型(NaX和NaY)分子筛上的吸附行为.计算结果显示,现有的通用力场已不适用于分子筛吸附CO2的体系,需要优化力场.CO2在分子筛上吸附是通过分子间非键能发生作用,而文献中优化力场常用的量子化学计算法,虽然求得的分子内键作用力较为精确,但对分子间作用力却不一定有效,特别是范德华力.而计算结果与实验数据拟合法可以更真实反映分子间作用力,故采用后一种方法优化CO2/LTA型分子筛的力场.所得力场参数既适合CO2与5A分子筛吸附体系又适合CO2在4A分子筛上的吸附,但根据LTA型分子筛得到的优化力场不能正确描述FAU型分子筛的吸附行为.采用拟合实验数据的方法,同样得到1组适合NaY分子筛的优化力场,用于计算NaX分子筛的CO2吸附等温线,结果与实验值相吻合.可见,骨架结构相同的分子筛,可以用相同的力场参数去计算其吸附性质,而不受硅铝比和骨架外阳离子的影响.但不同的骨架结构需要不同的力场参数来描述.     

P改性ZSM-5分子筛的结构及酸性变化

P-ZSM-5分子筛通常用来催化甲醇转化制轻烯烃,乙醇脱水制乙烯,芳烃的烷基化或者歧化等反应。目前,P-ZSM-5分子筛中磷和分子筛之间的相互作用仍不清楚。本文通过密度泛函理论（Density Functional Theory,DFT）计算了ZSM-5分子筛改性前后的结构及酸性变化。结果发现P骨架外改性后,磷酸分子的氢原子和分子筛骨架氧原子形成氢键作用,并且O₄,H_a和0_zeo总是保持在一条直线上,这是稳定的骨架外改性结构;骨架改性后,分子筛优化前后的结构发生较大变化,这是因为固定了8T模型中的终止氢原子,分子筛的骨架结构阻止了H₂PO₃基团的插入。本文还计算了磷酸分子和分子筛的酸性位之间的关系,研究发现,分子筛中引入P后,其酸性降低,且骨架改性后酸性减弱的程度更大。这一结果可以进一步指导实验,制备出不同酸性的分子筛。     

从头预测蛋白质骨架的一种并行蚁群方法及其在CASP8/9中的应用

从低同源关系的氨基酸序列预测蛋白质的三维结构被称为从头预测,它是计算生物学领域中的挑战之一.蛋白质骨架预测是从头预测的必要先导步骤.本文应用一种基于共享信息素的并行蚁群优化算法,在现有能量函数指导下,通过不同能量项之间的定性互补,构建具有最低能量的蛋白质骨架结构,并通过聚类选择构象候选集合中具有最低自由能的构象.在CASP8/9所公布的从头建模目标上应用了该方法,CASP8的13个从头建模目标中,模型1中有2个目标的预测结果超过CASP8中最好的结果,7个位列前10名;CASP9的29个从头建模目标中,候选集中的最佳结果中有20个进入Server组的前10名,模型1中有11个进入前10名.本文的结果说明融合多个不同的能量函数指导并行搜索,可以更好地模拟天然蛋白质的折叠行为.同时,在本算法载体上实现了不同种类搜索策略的融合并行,对于用非确定性算法解决类似的优化问题来说也是一种新颖的方法.     

分子筛催化甲苯歧化SE1反应机理的分子模拟研究

应用分子模拟半经验量子力学Mopac 6．0-AM1近似计算方法分析了分子筛催化甲苯歧化反应的S_E~1反应历程,确定了反应历程中的反应态、过渡态和产物态,得到了反应活化能和反应热等相关信息,对内禀反应坐标的计算进一步验证了反应过程中的能量变化。计算结果表明,分子筛催化的甲苯歧化反应沿S_E~1反应历程可通过两步基元反应完成；质子由分子筛向甲苯分子转移的过程为反应的快速步骤,其活化能达到428．54 kJ·mol~(-1),需要在高温下进行；甲苯歧化总反应的热效应很小,与实验数据相吻合。     

铁离子在ZSM-5分子筛中存在位置的理论研究

对磷铁改性的ZSM-5分子筛粉末进行X射线扫描,获得了较高分辨率的衍射数据,并由X射线荧光分析数据得到分子筛的化学组成。采用分子模拟软件中的建模及结构优化工具,构建了硅铝比为23.77的ZSM-5分子筛的三维空间构型,用分子力学方法计算二价铁离子在分子筛孔道中的位置并用Rietveld精修的方法验证铁离子在ZSM-5分子筛孔道中的位置。结果表明,金属改性的ZSM-5分子筛中二价铁离子主要存在于十元环S形孔道和直孔道交叉处,少量存在于直孔道中。计算了Fe²⁺离子在孔道内的配位间距,对改性的ZSM-5分子筛进行了结构参数分析,最终确定了两种Fe²⁺在孔道内的确切坐标分数。     

分子计算理论方法及在化工计算中的应用

论述了量子力学中从头计算、半经验和密度泛函方法及分子力学的基础理论，概述了常用的MD、MC分子模拟方法，总结了多种应用软件的主要功能，并结合实例对HyperChem．7软件的功能进行了具体的说明。     

HZSM-5中水吸附行为的实验与分子模拟

利用智能重量分析仪(IGA—003,HIDEN)测定了298K条件下水蒸汽在HZSM-5型分子筛中的吸附等温线。并采用巨正则系综Monte Carlo模拟方法(GCMC)研究了水在HZSM—5型分子筛中的吸附等温线,计算结果与实验结果吻合较好。分子模拟计算得到的水分子的微观吸附性质表明水分子吸附在氢离子和铝原子的周围,这是因为水分子是极性分子,分子筛上的氢在库仑力的作用下会与水分子发生强的相互作用,并导致分子筛骨架上的硅铝比与水分子的吸附量之间存在线性关系。计算结果还表明水的吸附热与H_2O/Al之间存在线性关系。     

HA和HYP分子内质子传递模式差异的理论研究

采用量子化学从头算的计算方法,研究了竹红菌素(HA)4种异构体发生分子内质子传递(IPT)的过程。结果表明,在竹红菌素分子内质子传递的过程中不会发生碳骨架结构的变化,这与之前文献中的猜测是不一致的,利用CIS和TD方法计算研究了竹红菌素激发态分子内质子传递的过程.结果表明,竹红菌素顺式结构的IPT过程是一个～10ps的瞬态过程,而竹红菌素反式结构的IPT过程则是一个～50～250ps的瞬态过程.根据计算结果我们对竹红菌素和金丝桃蒽酮分子内质子传递模式之间的差异做出了初步的解释.     

氧分子在镍钛合金(100)表面吸附行为的研究

NiTi形状记忆合金作为一种广泛使用的生物医学材料，表面形成的氧化膜是其具有良好生物相容性的基础。氧分子在NiTi合金表面的吸附是其形成氧化膜的关键，应用离散变分Xα方法，首次对O2分子在B2结构NiTi(100)表面的吸附过程进行了理论研究，分别计算了在两种不同的O2分子吸附方式中Ti-O原子间的键级和电荷分布。结果表明：O2分子垂直接近NiTi(100)表面对其发生吸附更为有利。在吸附过程中，O2分子中只有一个氧原子被其最近邻的一个表面铁原子所吸附，而合金中其它表面原子及体相原子的电子结构没有变化。Mulliken集居数及局域态密度分析表明，吸附过程中铁原子与氧原子之间的相互作用主要是由2p(O)电子和4s，4p(Ti)电子贡献。     

Charting of geoelectric potential signal dynamics via geometrical techniques and its possible relation to significant earthquakes in Western Greece

An exploratory data analysis (EDA) framework was developed in order to investigate the presence of possible correlations in the long-term geoelectric potential (LTGP) signal, prior to significant seismic events in Western Greece. Experimental data, which had been collected continuously within a 6-year period (1998–2003) at the earthquake signal-acquisition center of the University of Patras Seismological Laboratory (UPSL), were studied. The multidimensional scaling (MDS) technique was used to detect putative clustering tendencies in the ensemble of time-series (TS) segments that could indicate the existence of a possible correlation between the geoelectric signal structure and the impending seismic activity. The end result is a 2-dimensional point diagram with the geometry reflecting important signal characteristics, directly related with the underlying seismic events. In addition, the “appending technique”, a well-suited data analysis methodology was incorporated as a means of relating any other TS segment directly with the pre-computed, via the MDS, point diagram. Using the proposed EDA framework, we examined the presence of similar temporal patterns in the recorded geoelectric TS field, 10 days before the occurrence of the major earthquakes. The presented experimental results indicated clearly the validity of the introduced approach and, further, motivated the use of such advanced visualization schemes for charting precursor trends of significance seismicity.     

A visual analytics framework for spatio-temporal analysis and modelling

To support analysis and modelling of large amounts of spatio-temporal data having the form of spatially referenced time series (TS) of numeric values, we combine interactive visual techniques with computational methods from machine learning and statistics. Clustering methods and interactive techniques are used to group TS by similarity. Statistical methods for TS modelling are then applied to representative TS derived from the groups of similar TS. The framework includes interactive visual interfaces to a library of modelling methods supporting the selection of a suitable method, adjustment of model parameters, and evaluation of the models obtained. The models can be externally stored, communicated, and used for prediction and in further computational analyses. From the visual analytics perspective, the framework suggests a way to externalize spatio-temporal patterns emerging in the mind of the analyst as a result of interactive visual analysis: the patterns are represented in the form of computer-processable and reusable models. From the statistical analysis perspective, the framework demonstrates how TS analysis and modelling can be supported by interactive visual interfaces, particularly, in a case of numerous TS that are hard to analyse individually. From the application perspective, the framework suggests a way to analyse large numbers of spatial TS with the use of well-established statistical methods for TS analysis.     

Ab initio calculations on the five-membered alumino-silicate framework rings model: implications for dissolution in alkaline solutions

An ab initio restricted Hartree-Fock calculation utilising the standard 6-31G basis set was used to calculate total energies after PM3 calculations of energy-optimised geometries for the five-membered alumino-silicate framework rings cluster for a total of ten T sites. Calculations have shown that in the absence of protons or other ions, the most favourable sites for 1A1, 2A1 and 3A1 substitution of Si are the T6, T1 and T9 sites respectively. With more Al atoms replacing Si in a cluster, T-O bond lengths and T-O-T angles show lengthening and sharpening trends respectively, which indicates that the structure is distorted to a more relaxed symmetry with Obr atoms moving outwards. The calculated bond lengths and angles have been shown to match the values observed in previous studies, including those for a four-membered alumino-silicate single ring cluster. Based on the optimised five-membered alumino-silicate framework rings model, a further ab initio HF calculation has been conducted on ring breakage for releasing Al(Q3) and Si(Q3) centres to form T(OH)4 and HOT(OM)3 tetrahedra under local and highly alkaline environment. The obtained results suggest that Al(Q3) compared with Si(Q3) breaks more readily with the exothermal reaction enthalpy being in excess of -244.4 kJ/mol, while the most reactive Si(Q3) centre shows an exothermal reaction enthalpy of only -33.8 kJ/mol. This indicates that Al dissolves in preference to Si in local environment. The dissolution mechanism of the five-membered Al-Si framework rings model in highly alkaline solutions has been suggested to be composed of an ion-pairing reaction and an interaction between the remaining broken ring cluster triple bond TOH and MOH.     

Multistart Tabu Search and Diversification Strategies for the Quadratic Assignment Problem

The quadratic assignment problem (QAP) is a well-known combinatorial optimization problem with a wide variety of applications, prominently including the facility location problem. The acknowledged difficulty of the QAP has made it the focus of many metaheuristic solution approaches. In this paper, we show the benefit of utilizing strategic diversification within the tabu search (TS) framework for the QAP, by incorporating several diversification and multistart TS variants. Computational results for an extensive and challenging set of QAP benchmark test problems demonstrate the ability of our TS variants to improve on a classic TS approach that is one of the principal and most extensively used methods for the QAP. We also show that our new procedures are highly competitive with the best recently introduced methods from the literature, including more complex hybrid approaches that incorporate the classic TS method as a subroutine.     

An Analytical Study on Structure, Stability and Design of General Nonlinear Takagi–Sugeno Fuzzy Control Systems

In this paper, we first study analytical structure of general nonlinear Takagi-Sugeno (TS, for short) fuzzy controllers, then establish a condition for analytically determining asymptotic stability of the fuzzy control systems at the equilibrium point, and finally use the stability condition in design of the control systems that are at least locally stable. The general TS fuzzy controllers use arbitrary input fuzzy sets, any types of fuzzy logic AND, TS fuzzy rules with linear consequent and the generalized defuzzifier which contains the popular centroid defuzzifier as a special case. We have mathematically proved that the general TS fuzzy controllers are nonlinear controllers with variable gains continuously changing with controllers’ input variables. Using Lyapunov’s linearization method, we have established a necessary and sufficient condition for analytically determining local asymptotic stability of TS fuzzy control systems, each of which is made up of a fuzzy controller of the general class and a nonlinear plant. We show that the condition can be used in practice even when the plant model is not explicitly known. We have utilized the stability condition to design, with or without plant model, general TS fuzzy control systems that are at least locally stable. Three numerical examples are given to illustrate in detail how to use our new results. Our results offer four important practical advantages: (1) our stability condition, being a necessary and sufficient one, is the tightest possible stability condition, (2) the condition is simple and easy to use partially because it only needs the fuzzy controller structure around the equilibrium point, (3) the condition can be used for determining system local stability and designing fuzzy control systems that are stable at least around the equilibrium point even when the explicit plant models are unavailable, and (4) the condition covers a very broad range of nonlinear TS fuzzy control systems, for which a meaningful global stability condition seems impossible to establish.     

基于禁忌搜索的模糊神经网络结构优化

本文提出了一种基于禁忌搜索的模糊神经网络自动优化学习方法（fuzzy neural network based on tabusearch，FNNTS）。该方法利用禁忌搜索算法搜索最优的模糊神经网络结构，并结合最小二乘法和梯度下降法对网络参数进行学习，大大减少了对专家知识的依赖。非线性函数逼近的实验结果表明，所提出的方法能获得更精练的网络结构和更小的误差，从而验证了本文方法的有效性和可行性。     

求解作业车间调度问题的混合帝国主义竞争算法

针对最小化最大完工时间的作业车间调度问题（JSP）,提出一种结合帝国主义竞争算法（ICA）和禁忌搜索（TS）算法的混合算法。混合算法以帝国主义竞争算法为基础,在同化操作中融入遗传算法中的杂交算子和变异算子,使算法全局搜索能力更强。为了克服帝国主义竞争算法局部搜索能力弱的缺点,引入禁忌搜索算法进一步优化同化操作后的后代。禁忌搜索算法采用混合邻域结构和新型选择策略,使得算法能够更有效地搜索邻域解。混合算法兼具全局搜索能力和局部搜索能力,通过对13个经典的Benchmark调度问题进行仿真测试,并与近年4种新型混合算法进行对比分析,实验结果表明了所提算法求解Job Shop调度问题的有效性和稳定性。     

DVB数字广播台标/字幕插入机

介绍一种用于DVB数字广播的台标／字幕插入机。对系统结构和功能做出了描述，给出了具体的实现，并对未来可进行的拓展工作进行了展望。此服务器可广泛应用于城镇电视台的节目实时插入字幕台标及其他多种数据业务，在经过QAM调制器后可通过DVB标准的广播网直接播送给最终用户，也可以通过IP网广播节目。