Screening the optimal Co_(x)/CeO_(2)(110)(x=1–6)catalyst for methane activation in coalbed gas

The challenges posed by energy and environmental issues have forced mankind to explore and utilize unconventional energy sources.It is imperative to convert the abundant coalbed gas(CBG)into high value-added products,i.e.,selective and efficient conversion of methane from CBG.Methane activation,known as the“holy grail”,poses a challenge to the design and development of catalysts.The structural complexity of the active metal on the carrier is of particular concern.In this work,we have studied the nucleation growth of small Co clusters(up to Co_(6))on the surface of CeO_(2)(110)using density functional theory,from which a stable loaded Co/CeO_(2)(110)structure was selected to investigate the methane activation mechanism.Despite the relatively small size of the selected Co clusters,the obtained Co_(x)/CeO_(2)(110)exhibits interesting properties.The optimized Co_(5)/CeO_(2)(110)structure was selected as the optimal structure to study the activation mechanism of methane due to its competitive electronic structure,adsorption energy and binding energy.The energy barriers for the stepwise dissociation of methane to form CH3^(*),CH2^(*),CH^(*),and C^(*)radical fragments are 0.44,0.55,0.31,and 1.20 eV,respectively,indicating that CH^(*)dissociative dehydrogenation is the rate-determining step for the system under investigation here.This fundamental study of metal-support interactions based on Co growth on the CeO_(2)(110)surface contributes to the understanding of the essence of Co/CeO_(2) catalysts with promising catalytic behavior.It provides theoretical guidance for better designing the optimal Co/CeO_(2) catalyst for tailored catalytic reactions.

双金属团簇Cu_(12)Fe吸附CO和H_(2)的理论研究

基于第一性原理密度泛函理论(DFT)方法研究了Cu_(12)Fe团簇的结构稳定性、热力学稳定性和反应活性.计算得出正二十面体Fe原子核心团簇Ih-core比正二十面体Fe原子壳层团簇Ih-shell的热力学稳定性更强.通过分析吸附能讨论了CO和H_(2)在Ih-core团簇上的吸附构型.计算结果表明,Ih-core团簇以顶角Corner位吸附CO时吸附能最大,吸附模型最稳定,H_(2)吸附过程中发生了解离,两个氢原子均形成表面Facet位吸附构型.最后,通过分析前线轨道得到吸附过程的轨道信息.

小团簇Co_(n)(n=1~7)吸附O,CO,CO_(2)的密度泛函研究

利用密度泛函理论(DFT),研究了吸附物(A:O、CO和CO_(2))在小团簇Co_(n)(n=1~7)上的吸附行为,即团簇Co_(n)A的几何结构、稳定特性和电子性质。结果表明:团簇Co_(n)O吸附位点的构型保持不变;团簇Co_(n)CO吸附位点除7B1转变为7T2构型之外,其余都与初始结构一致;团簇Co_(n)CO_(2)随吸附位点(顶位、桥位和空位)结构的不同显著变化。团簇Co_(n)A的吸附能由大到小依次为:Co_(n)O、Co_(n)CO、Co_(n)CO_(2),而能隙的变化规律不强,团簇Co_(n)A的吸附稳定性、Co和O(C)间距离、C—O键长、电荷转移都呈现规律性变化,说明吸附物被活化。团簇CO_(2)对CO的氧化机制研究中,路径b仅需越过0.436 eV的能垒,而路径a需要1.686 eV,表明路径b更有利,团簇CO_(2)OT有望成为良好的CO氧化催化剂。

A Fast Multi-tasking Solution: NMF-Theoretic Co-clustering for Gear Fault Diagnosis under Variable Working Conditions

Most gear fault diagnosis(GFD)approaches su er from ine ciency when facing with multiple varying working conditions at the same time.In this paper,a non-negative matrix factorization(NMF)-theoretic co-clustering strategy is proposed specially to classify more than one task at the same time using the high dimension matrix,aiming to o er a fast multi-tasking solution.The short-time Fourier transform(STFT)is first used to obtain the time-frequency features from the gear vibration signal.Then,the optimal clustering numbers are estimated using the Bayesian information criterion(BIC)theory,which possesses the simultaneous assessment capability,compared with traditional validity indexes.Subsequently,the classical/modified NMF-based co-clustering methods are carried out to obtain the classification results in both row and column tasks.Finally,the parameters involved in BIC and NMF algorithms are determined using the gradient ascent(GA)strategy in order to achieve reliable diagnostic results.The Spectra Quest’s Drivetrain Dynamics Simulator gear data sets were analyzed to verify the e ectiveness of the proposed approach.

A Novel 3D Metal Coordination Polymer Based on Tetranuclear Cobalt Cluster Building Blocks:Synthesis,Crystal Structure and Photocatalytic Property

A novel 3D MCP,[Co;（μ;-OH）(btc)（bmip）];(1,H;btc=1,3,5-benzenetricarboxylate acid,bmip=1,3-bis（2-methylimidazolyl）propane),was synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction,powder XRD,FT-IR,TGA and elemental analysis techniques.MCP 1 features a 3D framework based on tetranuclear Co（Ⅱ）clusters where the four cobalt ions are coplanar,and shows an unusual binodal（3,10）-connected topology.Furthermore,the photocatalytic experiment result indicates the degradation ratios of rhodamine B（RhB）reach 78.2%when MCP 1 acts as catalyst.

Large adsorption energies for CO on Sc_n(n=2-8,13) nanoclusters

In order to seek a transition metal cluster with high ability to adsorb CO molecule, the author performs a density function theory calculation on COScn （n = 2-8, 13） clusters. The results demonstrate that COScn （n = 2-8, 13） clusters have the large adsorption energies of which the values are over 3.6 eV, and the elongations of C-O bond length exceed 20% in most calculated sizes. Adsorbing CO contributes to the improvement of the chemical activity, but reduces the magnetic moment of corresponding Scn cluster.

Two New Complexes with the Same(3,8)-Connected tfz-d Topology Based on [Co4(μ3-OH)2] Clusters and Different Aromatic Multicarboxylic Acids

Two new metal-organic frameworks（MOFs）, namely, [Co_2（L_1）（bix）（μ_3-OH）]·2H_2O（1） and [Co_2（L_2）（bix）（μ_3-OH）]·2.5H_2O（2）（H_3L_1 = 5-oxyacetate isophthalic acid, H_3L_2 = 3,5-bis-oxyacetate-benzoic acid, bix = 1,4-bis（imidazol-1-ylmethyl）benzene）, have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and powder X-ray diffraction（PXRD） analysis. Both complexes 1 and 2 demonstrate identical three-dimensional（3D）（3,8）-connected tfz-d nets with（4~3）_2（4~6·6^（18）·8~4） topologies, where the tetranuclear [Co_4（μ_3-OH）_2] clusters act as 8-connected nodes and aromatic multicarboxylic ligands as 3-connected nodes. The results show that the ligands with different geometrical conformations can form products with the same topological structures. Their thermal and magnetic properties were also investigated.

Research on technology cluster evolution of global MEMS sensors based on patent co-occurrence analysis

At present, microelectro mechanical systems (MEMS) sensors have gradually replaced traditional mechanical sensors and are applied to several fields. Many developed countries pay high attention to technological innovation of MEMS sensors, and have applied a large number of patents since 2000. In this study, the patents of MEMS sensor from 2000 to 2015 are researched, the patents data is collected from Derwent Innovation Index (DII), and the method of co-classification analysis is used to investigate the technology cluster evolution of MEMS sensors. Results show that the technology diffusion occurrs in each technical field and the technology relevance between different technical fields is changed over time. On the whole, the evolution process of MEMS sensor is the manufacture and material of sensor chip, the electronic components and measuring function, the computing and control technology, and applications to biochemical field and communication.

Preparation and characterization of Ni/Co bimetallic nano-clusters

Ni/Co bimetallic nano-cluters have been prepared from the aqueous solution byreducing their corresponding metal salts under suitable conditions. The experimental conditionsincluding the type and concentration of protective agent, feeding order and the pH of the solutionthat influence the average particle size have been studied in detail. Transmission electronmicroscopy (TEM) indicates that the shape of those bimetallic nano-cluster particles is spheroid.The alloy structure has been shown by X-ray powder diffraction (XRD). The X-ray photoelectronspectroscopic (XPS) data have confirmed that the nickel and cobalt in the bimetallic nano-clustersare in the zero-valence state.

A Visualization Study of Hot Spots of Research on Siraitiae Fructus over a Decade Based on Co-clustering Analysis

[Objectives] To use co-clustering analysis and visualization method to analyze the research on Siraitiae Fructus in recent ten years,to know the hot spots and trend of research. [Methods] Relevant research results about S. Fructus in CNKI from January of 2007 to December of 2016 were retrieved by computers,and the retrieval time was February 20,2017. BICOMB,Net Draw,g CLUTO and SPSS19. 0 software were used to conduct co-clustering analysis and visualization analysis for included articles. Keywords were analyzed,and social network graph,visualization matrix,peak image and multidimensional scaling analysis map were drawn. Correlation among high-frequency key words were analyzed. [Results] Totally 723 articles were included,among which 70 articles were issued during 2012-2016; 76 key words were obtained by key word co-occurrence network map,among which mogroside,MOG,extraction process,tissue culture,cultivation technology,varieties,growth and development were in the core position; visualization and the peak image showed that the topics in this research field could be divided into 6 categories; research hotspot dynamic evolution showed that S. Fructus flower,beverage,total flavonoids,gene expression,gene cloning,enzyme,apoptosis,and S. Fructus seed oil would be the hot spots of further study. [Conclusions]This study reveals that the research on S. Fructus in the recent ten years is becoming mature,and expanding to deep level. This study can be promoted to discipline development evaluation of TCM research field.

江西赣州站大气CO变化特征及区域输送研究

基于2018年12月—2019年11月江西省赣州站大气CO和CO_(2)浓度高精度在线观测资料,探究了赣州站CO浓度水平及其变化特征,厘清了该区域气团的轨迹,分析了区域大气输送的影响以及潜在排放源区分布特征,并对△CO_(2)和△CO浓度之间的相关性进行了分析。结果表明:(1)研究期内赣州站CO的平均浓度为415.0×10^(-9);赣州站CO浓度日变化特征具有季节差异性,在春夏季,夜间至清晨期间,CO浓度较高,午后CO浓度开始下降;在秋冬季,CO浓度日变化总体呈现白天高,夜间至清晨略低的特征。CO本底季节浓度呈现出明显的季节变化,1月出现峰值(694.8×10^(-9)),7月出现最小值(215.6×10^(-9))。(2)轨迹聚类分析表明,春、秋、冬季的赣州站高浓度CO主导气流来自江西省北部、湖北省东部、安徽省南部以及珠江三角洲地区;2019年1月28—29日污染事件的轨迹聚类分析表明,江西、安徽和江苏等省份的燃烧效率较高。(3)冬季的△CO和△CO_(2)呈强相关性,表明化石燃料和生物质燃烧以及人为排放活动对寒冷季节CO_(2)浓度变化的影响显著高于其他季节。

Preparation, Structures and Magnetic Properties of Two Co-based Clusters with Triangular Core and Cuboidal Core Geometries

Two novel Co-based clusters with the 2-(hydroxylmethyl)pyridine(hmpH)ligand,formulated as[Co3(hmp)6(hmpH)]×2NO3×3H2O(ZTU-3)and[Co4(hmp)4(CH3CO2)2(H2O)4]×2NO3(ZTU-4),have been successfully synthesized and structurally characterized.ZTU-3 features a triangular core geometry,while ZTU-4 exhibits a cuboidal core geometry.In addition,the magnetic properties of ZTU-3 and ZTU-4 are also all investigated.

The reflection of hierarchical cluster analysis of co-occurrence matrices in SPSS

Purpose： To discuss the problems arising from hierarchical cluster analysis of co-occurrence matrices in SPSS, and the corresponding solutions. Design/methodology/approach： We design different methods of using the SPSS hierarchical clustering module for co-occurrence matrices in order to compare these methods. We offer the correct syntax to deactivate the similarity algorithm for clustering analysis within the hierarchical clustering module of SPSS. Findings： When one inputs co-occurrence matrices into the data editor of the SPSS hierarchical clustering module without deactivating the embedded similarity algorithm, the program calculates similarity twice, and thus distorts and overestimates the degree of similarity. Practical implications： We offer the correct syntax to block the similarity algorithm for clustering analysis in the SPSS hierarchical clustering module in the case of co-occurrence matrices. This syntax enables researchers to avoid obtaining incorrect results. Originality/value： This paper presents a method of editing syntax to prevent the default use of a similarity algorithm for SPSS＇s hierarchical clustering module. This will help researchers, especially those from China, to properly implement the co-occurrence matrix when using SPSS for hierarchical cluster analysis, in order to provide more scientific and rational results.

Co-word clustering analysis for nursing safety management research focuses by PubMed

目的：基于Pubmed数据库分析护理安全管理研究的现状及热点。方法：以“safety management”为主题词，检索2007年9月至2017年9月PubMed数据库中有关护理安全管理的文献，并使用Bicomb软件、SPSS20．0对主题词进行共词聚类分析。结果：共获得文献2353篇，提取高频主题词19个，占总频次的27．50％，通过对高频主题词词篇矩阵进行共词聚类，得到5个研究热点：护理安全文化的研究、团队协作促进护理安全、护理安全管理实践、护理人员工作场所暴力以及护理安全质量评价标准的相关研究。结论：对近10年护理安全管理研究热点的分析有助于了解该领域研究重点及发展趋势，为随后护理安全管理研究及实践提供参考。

SYNTHESIS AND CATALYTIC PROPERTY OF POLYMER-SUPPORTED Fe-Co HETEROTETRAMETALLIC CLUSTERS

Four polymer-supported Fe-Co tetrametallic clusters have been prepared by ion exchange and ligand exchange. Their structures were characterized by IR, UV/visible diffuse reflectance spectra and elemental analysis, and by analogy with the reference cluster PhCH_2NMe_3FeCo_3 (CO)_2 . The four heterogenous clusters were efficient catalysts in the hydroformylation of 1-hexene, turnover numbers amounted to 823 — 924 with the yield of 83.2—92.4% heptyl aldehydes and ratios of normal aldehyde to iso-aldehyde of 1.2—1.6, they are facilitated forming the normal aldehyde in comparison with the homogeneous analogue. For the polymer-supported clusters prepared by ion exchange, the polymer-cation parts had no obvious effect on the activity of the cluster anion. The polymer-phosphine substituted cluster prepared by ligand exchange was more stable than the clusters preparedby ion exchange.

Research status and hotspots of economic evaluation in nursing by co-word clustering analysis

Objective:The aim of this study is to discover research status and hotspots of economic evaluation(EE)in nursing area using co-word cluster analysis.Methods:Medical Subject Heading(MeSH)term“cost–benefit analysis”was searched in PubMed and nursing journals were limited by the function of filter.The information of author,country,year,journal,and keywords of collected paper was extracted and exported to Bicomb 2.0 system,where high-frequency terms and other data could be further mined.SPSS 19.0 was used for cluster analysis to generate dendrogram.Results:In all,3,020 articles were found and 10,573 MeSH terms were detected;among them,1,909 were MeSH major topics and generated 42 high-frequency terms.The consequence of dendrogram showed seven clusters,representing seven research hotspots:skin administration,infection prevention,education program,nurse education and management,EE research,neoplasm patient,and extension of nurse function.Conclusions:Nursing EE research involved multiple aspects in nursing area,which is an important indicator for decision-making.Although the number of papers is increasing,the quality of study is not promising.Therefore,further study may be required to detect nurses’knowledge of economic analysis method and their attitude to apply it into nursing research.More nursing economics course could carry out in nursing school or hospitals.

Cluster-assembled cobalt doped ZnO nanostructured film prepared by low energy cluster beam deposition

Cobalt doped ZnO film assembled by the nanoparticles was prepared by low energy cluster beam deposition.The microstructure,phase structure and optical properties were investigated for the nanostructured films.The results show that the nanostructured film was assembled by monodisperse spherical nanoparticles with average diameter of about 29.3 nm which are distributed uniformly and compactly.The results of X-ray diffraction(XRD)show that cobalt doped ZnO nanostructured film is indexed to a wurtzite structure of ZnO,and no Co-phase structure and other phases are observed.The UV-visible absorption spectra show that the optical band-gap of the film is broadened after doping.

A Density Functional Study for the Reaction Mechanism of CO Oxidation on the Copper Cluster

We have studied the reaction mechanism of CO oxidation on the Cu13 cluster via density functional theory. There are two main reaction pathways to be considered： Eley-Rideal（ER） and Langmuir-Hinshelwood（LH） mechanisms, respectively. According to these two main reaction mechanisms, we have obtained five reaction pathways for the first CO oxidation（denoted as RER1,RER2, RLH1, RLH2 and RLH3, respectively）： RER1 is COgas ＋ O2（ads） → O（ads） ＋ CO2（gas）; RER2 is COgas ＋ O2（ads） → CO3（ads） → O（ads） ＋ CO2（gas）; RLH1 refers to CO（ads） ＋ O2（ads） → O（ads） ＋ CO2（gas）; RLH2 refers to CO（ads） ＋ O2（ads） → OOCO（ads） → O（ads） ＋ CO2（gas） and RLH3 refers to O2（ads） ＋ CO（ads）→ O（ads） ＋ O（ads） ＋ CO（ads） → O（ads） ＋ CO2（gas）. These pathways have low energy barriers and are strongly exothermic, suggesting the Cu13 cluster is very favorable catalyst for the first CO oxidation. However, there are higher energy barriers of 99. 8 and 45.4 kJ/mol in the process of producing and decomposing intermediates along the RLH2 and RER2, indicating that RER1, RLH1 and RLH3 are superior pathways with lower energy barriers, especially the RER1 channel. Thereafter, the second CO is more prone to react with the remaining oxygen atom on Cu13 along the ER channel in comparison with the LH pathway, in which the moderate barrier is 70.0 kJ/mol and it is exothermic by 59.6 kJ/mol. Furthermore, the interaction between the absorbate and cluster is analyzed by electronic analysis to gain insights into high activity of the copper cluster.

Efficiently Adsorbing CO Molecules Using Al_6Si Cluster

Based on the density functional theory with generalized gradient approximation, the stable geometrical structures of one or more CO molecules adsorbed on the Al6Si cluster are investigated and the corresponding adsorption energies are also calculated. It is found that the cluster Al6Si can adsorb six CO molecules. The thermal stability of the（CO）6@Al6Si complexes is examined using the atom centered density matrix propagation molecular dynamics calculations at 373 K. The results show that two isomers of Al6Si cluster can solidly adsorb six CO molecules, and the other isomer adsorbs four ones. Therefore, the Al6Si cluster is a promising candidate for eliminating CO effectively.

Nanoclusters Au19Pd and Au19Pt Catalyzing CO Oxidation: a Density Functional Study

The gold atoms on the Au20 cluster had been substituted by the palladium and platinum atoms to obtain the doped clusters with more stable geometries as a function of the bind energy and interaction energy in the previous study. Therefore, we investigated the catalytic activities of the AuPd and AuPt clusters for CO oxidation along the Langmuir-Hinshelwood mechanism. It is found that the coadsorption of CO and O2 on the doped clusters is obviously stronger than on the Au20 cluster, especially on the doped atom, which makes potential energy of the transition state lower than the total energy of the reactants so that it can promote CO oxidation. The reaction on these doped clusters with the heteroatom on the vertex is more difficult. However, the AuPd(S) is more prone to catalyzing the CO oxidation, in which the rate-limiting step has the lower energy barrier of 38.84 kJ/mol for this study. Therefore, the single atom can be modified to change the catalytic activity of the cluster for the CO oxidation. Meanwhile, the different sites on the clusters have different strengths of activity for the reaction.