一种基于聚类的空间数据知识获取算法

本文提出了一个针对空间数据库基于聚类的知识获得取算法,该算法可解决空间的数据的聚类问题。     

高性能BLAS在类Beowulf机群系统上的实现

Beowulf计划关于“基于COTS技术以满足特殊计算需要”的思想使得机群计算成为斋性能计算的一个重要流派,本文针对类Beowulf机群的Intel微处理器特点,讨论了BLAS的优化技术,在以软件DSM系统作为并行编程环境的类Beowulf机群系统上作出了性能评价。     

“双转移”背景下的河源产业集群内企业竞争力研究

河源若想抓住＂双转移＂这个契机加速发展,就势必要结合河源的产业发展现状及资源状况,选择有优势的产业重点培育,发展壮大一些龙头企业,进而带动中小企业的发展,提高区域竞争力。区域竞争力的不断增强,也势必会促进更多、更优秀的企业来河源发展。同时,集群内企业也要充分利用这一机遇,利用企业内外资源,加快提升自身的竞争力。     

一种改进的WCA算法

在WCA的基础上,提出了EWCA（Enhanced Weighted Clustering Algorithm）算法,在提高性能的同时降低了开销,并保持了算法的通用性,移动自组网中通过模拟实验对该分簇算法与WCA算法进行了性能比较。     

中国城市无意识下形成的四种空间类型

一种城市主义的批判性实践不应执着于不相干的美学自主性,而应着眼于作为当代城市化主要征象的四种空间类型:位于城市与农村之间界定模糊区域的工厂区;纵横全国的基础设施管线和网络;新型文化聚落、邻里和建筑物;来自农村而在城市工作的新城市主体所形成的心理与社会网络。     

Pulsed laser deposition of carbon films: Dependence of film properties on laser wavelength

We have grown thin carbon films by pulsed laser deposition and have investigated the extent to which the properties of such films, as well as the processes responsible for these properties, are laser wavelength dependent. Films were grown by ablating material from a graphite target onto room temperature Si(100) substrates with 1064 and 248 nm laser radiation. The films were analyzed byin situ electron energy loss spectroscopy and byex situ Raman spectroscopy. The results indicated that films grown with 1064 nm ablation were graphitic, while those grown with 248 nm radiation were diamond-like. We have also examined the mass and kinetic energy distributions of the particles ejected from graphite by the two laser wavelengths. The results indicated that irradiation of graphite with 1064 nm laser radiation results in the ejection of a series of carbon cluster ions C _n ⁺ (1 ≤ n ≤ 30) with mean kinetic energies less than 5 eV. Ablation of graphite with 248 nm radiation results in the ejection of primarily C ₂ ⁺ and C ₃ ⁺ with mean kinetic energies of 60 and 18 eV, respectively. These results suggest that large, low energy clusters produce graphitic films, while small, high energy clusters produce films of diamond-like carbon.     

Design of efficient noble metal single-atom and cluster catalysts toward low-temperature preferential oxidation of CO in H2

The preferential oxidation of CO in H₂ is attractive for the removal of trace amounts of CO to meet the requirement of proton-exchange membrane fuel cells (PEMFCs) application. The key is to design highly effective catalysts that work well in a wide range of low temperatures. Here, the recent progress in Au and Pt group metal catalysts for the PROX reaction is summarized, covering those with single-atom and cluster dispersed metal species with remarkable performance. Firstly, the progress of some representative catalysts is overviewed, with an emphasis on the strategies for improving low-temperature activity, selectivity, and stability. Then, special attention is focused on the key parameters affecting performance in the PROX reaction. Moreover, the reaction mechanisms in terms of adsorption and activation of reactants are discussed. Finally, the challenges and opportunities are offered for guiding the design of advanced noble metal catalysts toward the PROX process.     

Molecular dynamic simulation of heterogeneity and chemical states of fluorine in amorphous alkaline earth silicate systems

Chemical states of fluorine in fluorosilicate glasses in the system MF₂-MO-SiO₂ (M = Ca, Sr and Ba; SiO₂ content < 60 mol%) have been investigated by molecular dynamic (MD) simulations with a perfect ionic two-body potential. Comparison of the results with those derived by X-ray photoelectron spectra of the actual glasses demonstrates that MD simulations reproduce well the bonding states of fluorine in the systems as well as the formation of M-F clusters. The MD generated structure of imaginary glasses, or glasses not obtained by the conventional melt-quench technique, with 70 mol% SiO₂ indicates that an acidic environment induces a greater amount of F---Si bonds. Their M-F pair correlation functions plotted against normalized M-F distances suggest that relative ion positions in the clusters are very similar.     

纳米SnO_2及分子筛封装纳米SnO_2簇的湿敏性能研究

本文以液相法制备的纳米ＳｎＯ２微粉和分子筛封装的纳米ＳｎＯ２簇微粉为原料，采用涂膜法制作成湿敏元件，并且分别对这两种元件进行了湿敏性能的测试。研究表明纳米ＳｎＯ２微粉和分子筛封装的纳米ＳｎＯ２簇微粉，其湿敏元件灵敏度明显高于普通ＳｎＯ２微粉，阻湿线性关系良好，具有较好的湿敏性能。