基于Struts框架的科研资源计划系统的应用研究

Struts是基于模型视图控制体系(MVC)的Web应用框架。详细介绍了基于MVC体系的Struts工作原理，探讨应用Struts框架构建企业级应用系统的步骤及方法。给出了基于Struts的科研资源计划系(SRRPS)的设计实现，结果表明Struts框架能极大地提高系统的可扩展性、可重用性及可维护性。     

Designing collaborative,constructionist and contextual applications for handheld devices

This paper explores current applications for handheld devices and questions which of these make full use of the unique attributes of handheld devices in order to facilitate learning in a pedagogically sensible manner. In order to do so, the paper presents a functional framework which analyses handheld application in relation to their use as well as the pedagogical underpinning, if any, that informs their development. Our framework currently consists of seven distinct categories of application, which we term: administrative, referential, interactive, microworld, data collection, location aware and collaborative. We argue that three categories, namely data collection, location aware and collaborative, are particularly suited to learning with handheld devices when they are informed by collaborative, contextual and constructionist learning theories. Furthermore, we contend that applications of the type just outlined deserve further research since they are not attempting to replicate, or even augment, existing learning scenarios but rather they try to create new learning opportunities which would not be possible without (mobile) technology. Finally, the authors introduce a number of applications and learning scenarios that they have developed for handheld devices and explain their position within the framework.     

Scalable framework for blockchain-based shared manufacturing

Shared Manufacturing is a new mode of social manufacturing based on the principles of a sharing economy. This paper presents a scalable framework for blockchain-based Shared Manufacturing that preserves the transparency and immutability characteristics of transaction records, which is critical to building trust between entities in blockchain-based systems. We define a blockchain-based protocol for the service execution according to the design principles of the sharing economy. We present a scalable integration of blockchain technology into the concept of Shared Manufacturing by employing cross-chain solutions. We discuss existing cross chain technologies regarding the requirements of Shared Manufacturing and propose hybrid approach. We compare implementations of the proposed framework on two different blockchain networks: Ethereum public network and Xdai sidechain network. We conduct user-oriented test to explore the performance (cost and time) of the implementations in realistic situations in order to justify the use of the sidechain technology. Results indicate that the implementation on the sidechains provides greater scalability than the implementation on the public blockchain network.     

领域驱动模型的WEB软件系统设计研究

首先分析了J2EE3层架构的特性及局限,说明了领域驱动设计模型中的充血模型的优势。通过运用最新JDKI．7及Tomcat的相应改造,设计出能实现以充血模型结构为基础的新型WEB系统开发框架,并通过一简单实例说明架构如何支持系统开发。     

Supramolecular π–π assembly of a neutral [Cu(salen)] complex via the templating effect of an ionic inorganic complex Na2[Cu(mnt)2] forming a framework type material having well-defined channels

A classical ionic inorganic complex Na₂[Cu(mnt)₂] (mnt²⁻ = maleonitriledithiolate = 1,2-dicyanoethylenedithiolate), that acts as a template in assembling neutral [Cu(salen)] (salen = bis(salicylidene)ethylenediamine) complexes forming a framework type arrangement, is accommodated in the channel formed in the crystal structure of a new type of host–guest compound [Cu(salen)]₄ · Na₂[Cu(mnt)₂] (1). The non-covalent supramolecular interactions among [Cu(salen)] complexes and between [Cu(salen)] and [Cu(mnt)₂]²⁻ complexes in the crystal lattice of 1 result in weak antiferromagnetic coupling.     

Entity Framework数据访问性能优化的几种方法

Entity Framework一般通过LINQ代码或lambda表达式自动生成SQL语句,开发效率很高,然而使用时如果不注意会引来性能问题。通过对不同方法使用Entity Framework进行比较,提出Entity Framework数据访问性能优化的几种方法,包括更新数据时使用无跟踪查询、通过附加数据修改和删除数据、合理使用ToList()和FirstOrDefault()、合理使用预先加载。经过性能测试,这些方法是有效的。     

基于B／S模式的焊接工艺专家系统

采用．NET Framework技术实现了基于B／S模式的焊接工艺专家系统,系统可以实现碳钢、合金钢、铝合金材料的焊接工艺设计,通过XML文件存储知识库,实现更好地资源共享,使用LINQ to XML技术简化和优化推理机的推理过程,具有一定的实用价值。     

Synthesis and structure of the n = 4 member of the framework aluminium alkylenediphosphonate series Al2[O3PCnH2nPO3](H2O)2F2

We report here the solvothermal synthesis and crystal structure of the hybrid inorganic-organic framework material Al₂[O₃PC₄H₈PO₃](H₂O)₂F₂⋅2H₂O (monoclinic, 1P2₁/m, a = 4.961(2) ?, b = 11.930(5) ?, c = 10.727(5) ?, β = 93.972(6)^∘, Z = 2, R(F, F² > 2σ) = 0.094, R_w(F², all data) = 0.262), the third member of the Al₂[O₃PC_nH_2nPO₃](H₂O)₂F₂ framework series. The structure is formed from corrugated chains of corner-sharing AlO₄F₂ octahedra in which alternating AlO₄F₂ octahedra contain two fluorine atoms in a trans or a cis configuration. The diphosphonate groups link the chains together through Al-O-P-O-Al bridges and through the butyl groups to form a three-dimensional framework structure containing a one-dimensional channel system consisting of one type of channel only. The channels contain four extra-framework water molecules per unit cell. The formation of this member of the series shows that the form of the alkyl chain can successfully define the number of channel types and the channel length in this hybrid framework system.     

云环境下基于数据流的k-means聚类算法

k-means算法是一种 最常用的基于划分的聚类算法。传统的集中式k-means算法已不能适应当前呈爆炸式增长的数据规模,设计分布式k-means算法成为了目前亟需解决的问题。现有分布式k-means算法基于MapReduce计算框架且没有考虑初始聚类中心的影响。由于每个MapReduce任务均需要读写分布式文件系统,导致MapReduce不能有效表达多个任务之间的依赖关系,因此提出了一种基于数据流的计算框架,该框架建立在MapReduce之上,将数据处理过程按照数据流图建模。在该框架的基础上,提出了一种高效的k-means算法,它采用基于多次采样的初始聚类中心选取方法来实现负载均衡及减少迭代次数。实验结果表明,该算法的可扩展性较好,且效率比现有算法高。     

Groundwater use in Spain: an overview in light of the EU Water Framework Directive

In semi-arid regions, aquifers provide a series of practical advantages that make them preferential sources of water supply. In Spain, groundwater meets about one-fifth of the total water demand and is used to irrigate over one-third of the total irrigated land. This article examines groundwater use in Spain from the perspective of the EU Water Framework Directive. Analysis of different sector uses suggests that core problems (and solutions) related to groundwater lie in agricultural uses and that the Directive's environmental requirements remain distant from reality on the ground, where economic, political and social reasons prevail on legal obligations set by national and supranational authorities.