From Large-Eddy Simulation to Direct Numerical Simulation of a lean premixed swirl flame: Filtered laminar flame-PDF modeling

Large-Eddy Simulations (LES) and Direct Numerical Simulation (DNS) are applied to the analysis of a swirl burner operated with a lean methane–air mixture and experimentally studied by Meier et al. [19]. LES is performed for various mesh refinements, to study unsteady and coherent large-scale behavior and to validate the simulation tool from measurements, while DNS enables to gain insight into the flame structure and dynamics. The DNS features a 2.6 billion cells unstructured-mesh and a resolution of less than 100 microns, which is sufficient to capture all the turbulent scales and the major species of the flame brush; the unresolved species are taken into account thanks to a tabulated chemistry approach. In a second part of the paper, the DNS is filtered at several filter widths to estimate the prediction capabilities of modeling based on premixed flamelet and presumed probability density functions. The similarities and differences between spatially-filtered laminar and turbulent flames are discussed and a new sub-grid scale closure for premixed turbulent combustion is proposed, which preserves spectral properties of sub-filter flame length scales. All these simulations are performed with a solver specifically tailored for large-scale computations on massively parallel machines.     

一种基于Android平台的定制化PDF阅读器

在教学和生产实践中,一些特定的PDF资料可以存放在Android终端供用户阅读,而市场上存在的Android终端PDF阅读器功能过于复杂或者单一,难以满足特殊用户定制化的阅读需求。本文开发一款以开源的MuPDF分析器为内核的PDF阅读器,分别从启动视图、书架目录视图和阅读视图3个层面着手,增加了启动密码、固定书架、导航抽屉、书签等个性化功能,对开源PDF阅读器的开发具有一定的借鉴意义。     

真鲷转铁蛋白基因的克隆与表达特征分析

采用同源克隆的方法,根据相近物种转铁蛋白(Transferrin,TF)基因的序列设计简并引物,在经感染真鲷的cDNA上进行PCR扩增,获得了真鲷TF的全基因编码序列(GeneBank Accession No．AY335444)。该序列由2444bp核苷酸组成,含31bp5’非编码区和340bp3’非编码区以及2073bp的开放阅读框,可编码691个氨基酸,预测分子量约为74．3kD,等电点为5．63。同源性分析表明,真鲷TF与鱼类TF的相似性很高,约为65％～75％;与哺乳类转铁蛋白和乳铁蛋白的相似性约40％～50％;与脊索动物海鞘和无脊椎动物昆虫也有一定的相似性。进化分析表明,该基因是转铁蛋白而不是乳铁蛋白。真鲷TF与其它动物TF结构相似,是由两叶相似的结构域构成的单一肽链;该基因有一信号肽序列,缺乏糖基化位点,在它的两个结构域上,分别有三个TF家族的标签序列及一个MHC分子标签序列;与哺乳类相比,参与蛋白二硫键形成的半胱氨酸以及铁离子结合位点高度保守。RT-PCR结果显示,真鲷TF在肝脏成组成型表达,但在其它组织中的表达可受病原调控,表现为经病原刺激后转铁蛋白基因的组织分布显著增多。     

基于协同表示的多特征融合岩石分类

针对传统的岩石薄片成分分析耗时、识别率不高等问题,提出了一种基于协同表示(CR)的岩石薄片成分分析方法。首先,分析探讨了岩石薄片中颗粒纹理特性,证明将薄片图像的分层多尺度局部二值化(HMLBP)特征与灰度共生矩阵(GLCM)特征相融合能有效地表征岩石薄片中颗粒的纹理。然后,为降低识别阶段时间复杂度,采用主成分分析(PCA)方法将新特征降维到100维。最后,采用基于协同表示的分类器(CRC)进行分类识别。与基于稀疏表示的分类器(SRC)分别采用样本字典中某一个样本单独编码表征预测样本不同,基于协同表示的分类器采用样本字典中的所有样本协同编码表征预测样本,借助不同样本的同一属性提高识别率。实验结果表明该方法的识别速度较基于稀疏的分类器识别方法提高300%,识别率提高2%;在实践应用中能较好地区分岩石薄片中的石英成分和长石成分。     

国外煤炭加工技术

将煤炭加工成固体燃料和４种液体工业原料是国外目前比较先进的煤炭加工技术。煤的加工除能达到环境保护的要求外,还原获得效益。本文介绍了该技术及产品情况。     

基于网络发行的PDF文档版权保护系统的设计与实现

针对目前文档版权管理领域的需求,提出了基于网络发行的PDF文档版权保护整体解决方案.在系统中,采用了一种新的基于机器指纹的版权保护方法,使内容许可证与用户的机器指纹及用户的个人信息绑定.PDF文档内容采用高强度的对称密钥算法加密,客户端采用Acrobat插件开发技术来实现,最终PDF文档得到了内容级的加密保护,并且文档只能在本地按照内容许可证的要求进行解密及可控使用,从而在整个数字内容生命周期实行版权保护.     

办公文档与固定版式文档格式关系探讨

 从文档承载信息的抽象程度,提出了文档分层的思想,分析了以流式办公文档和固定版式文档为主的不同层次文档之间的关系.利用Tagged PDF,成功尝试了在固定版式文档中蕴含和提取办公文档信息,说明固定版式文档中容纳结构化办公文档格式的可行性,指出文档格式标准应贯通两种文档格式,形成完整的标准体系.     

PDF文档的一种数字水印算法

针对PDF文档的结构特点,研究并提出一种新的文本数字水印算法。在不改变PDF文档原有任何可见属性的前提下,利用PDF二进制文件自身的语法和结构特征嵌入水印信息。实验结果表明,该数字水印嵌入方法具有很好的不可感知性,能有效地实现文档版权和内容完整性保护。     

基于PDF的文献管理软件的开发

主要介绍了如何开发基于PDF的文献管理软件,并且对于在开发过程中所用到的一些关键技术给出了详细的介绍,最后分析了该软件的应用性,展望了文献管理软件未来的发展趋势。     

Verification and validation benchmarks

Verification and validation (V&V) are the primary means to assess the accuracy and reliability of computational simulations. V&V methods and procedures have fundamentally improved the credibility of simulations in several high-consequence fields, such as nuclear reactor safety, underground nuclear waste storage, and nuclear weapon safety. Although the terminology is not uniform across engineering disciplines, code verification deals with assessing the reliability of the software coding, and solution verification deals with assessing the numerical accuracy of the solution to a computational model. Validation addresses the physics modeling accuracy of a computational simulation by comparing the computational results with experimental data. Code verification benchmarks and validation benchmarks have been constructed for a number of years in every field of computational simulation. However, no comprehensive guidelines have been proposed for the construction and use of V&V benchmarks. For example, the field of nuclear reactor safety has not focused on code verification benchmarks, but it has placed great emphasis on developing validation benchmarks. Many of these validation benchmarks are closely related to the operations of actual reactors at near-safety-critical conditions, as opposed to being more fundamental-physics benchmarks. This paper presents recommendations for the effective design and use of code verification benchmarks based on manufactured solutions, classical analytical solutions, and highly accurate numerical solutions. In addition, this paper presents recommendations for the design and use of validation benchmarks, highlighting the careful design of building-block experiments, the estimation of experimental measurement uncertainty for both inputs and outputs to the code, validation metrics, and the role of model calibration in validation. It is argued that the understanding of predictive capability of a computational model is built on the level of achievement in V&V activities, how closely related the V&V benchmarks are to the actual application of interest, and the quantification of uncertainties related to the application of interest.