共享数据模式下多租户数据库复制技术研究

复制是一项利用资源副本来提高系统可用性,保证容错性并能提高性能的技术。云计算主要通过服务方式提供动态可伸缩的虚拟化资源,其中通过整合多个租户资源来实现资源共享和规模经济的多租户技术是一项重要技术,而共享数据模式的多租户技术具有最高的共享程度。鉴于云对于高可用性和弹性动态伸缩的需求,本文探讨了传统技术中的复制模型,同时介绍了复制副本之间的一致性维护策略,在此基础上探讨其在共享数据模式多租户技术中的适用性。     

基于变精度粗糙集理论的网格自学习及预测

提出了网格自学习和预测系统体系架构,采用变精度粗糙集和不协调目标信息系统理论揭示有关网格应用属性、网格资源动态状况和网格应用性能之间关系的知识,并采用增量式知识约减算法确定重要属性.利用所发现的知识,可以预测应用的资源需求及其性能.数据实验证明对作业资源需求和运行时间的预测值与实际值的偏差不超过30%.     

基于LQN模型的租户兴趣浏览路径挖掘

面向云计算环境中多租户应用的租户个性化服务需求,从多租户应用日志记录挖掘出租户兴趣浏览路径受到关注。针对传统的以浏览频度为主体的网络拓扑图研究问题,为了更好地找出租户在云平台网站上的兴趣网页,挖掘租户的兴趣浏览路径,综合租户对网页的浏览时长、接收字节数和浏览频度等多个要素定义租户兴趣度,构造租户执行图,纠正路径交叉状况以消除租户执行图中存在的多余路径,对循环路径中的对等节点进行整合以 消除循环嵌套,给出了 一种基于分层排队网（layered queue network, LQN)模型的租户兴趣浏览路径挖掘方法,在此基础上,借助广度优先遍历（breadth first search, BFS)算法进行挖掘。实验证明,改造后的LQN模型在租户兴趣浏览路径挖掘方面的效率有所提高。     

多步预测误差方法在先控性能评估中的应用

本文在基于最优预报的基础上提出了一种新的MPC性能评估方法。通过将已有的基于k步预测误差的控制系统性能评估方法进行拓展,得到了一种新的基于多步最优预测误差的先进控制系统的性能评估方法。最后提出了一个新的基于多步预测误差的性能指标用来对先进控制系统的控制性能进行评估和分析。该方法不需要关于过程的任何先验信息,因此便于在实际工程中实施和应用。将所提出的方法应用在某石化企业的一套先进控制装置的性能评估当中,验证了该方法的有效性。     

IaaS云环境下一种基于综合满意度的虚拟机放置策略

基础设施即服务(IaaS)环境下的一个关键需求是对租户申请的虚拟机进行合理放置。当前虚拟机放置策略的研究大都集中在数据中心能耗、资源损耗以及负载均衡等方面,很少有工作关注其对租户虚拟机启动时间的影响。为了减少虚拟机请求的周转时间,降低数据中心的资源损耗,本文首先建立了云服务租户满意度模型,给出了虚拟机请求到达云端后周转时间的量化方法;然后基于数据中心的资源损耗建立了云服务提供商满意度模型;最后,基于租户虚拟机启动时间与系统资源损耗建立了多目标约束优化模型,并提出了一种基于综合满意度(Comprehensive Satisfaction Based,CS-B)的虚拟机放置策略,该策略综合考虑了云服务租户与云服务提供商的需求,将租户所申请的虚拟机放置到综合满意度最高的服务器中运行。在OpenStack云平台上的仿真实验表明,CS-B虚拟机放置策略能够有效减少租户虚拟机在云端的部署时间,降低数据中心的资源损耗,有效提高了云服务商及租户的满意度。     

多资源闭环反馈调度系统的构建与分析

该文针对工作在不可预测环境下并且被调度任务集有着多个资源需求的计算机实时调度系统进行建模与分析,将多回路闭环反馈控制应用于计算机调度系统,利用反馈控制的强健性特征构建整个适应型多资源反馈调度机制。闭环系统可以根据运行时任务集执行情况及资源利用状况,通过调整调度任务的执行周期以及带宽服务层,达到改善任务集执行性能和优化利用系统的CPU资源与带宽资源的目的。     

一种基于时分复用的云资源管理方法

为了实现多租户的云计算环境下用户对计算资源的公平使用,用有限资源应对最大量的用户需求,针对云计算中成批到达的可划分独立任务,研究了一种基于时分复用的虚拟化资源管理方法.将整个云中计算资源作为复用对象,根据用户任务需求确定资源的复用周期和时间片,给出了资源时分复用的多种策略,并且对不同策略进行了深入的性能指标分析,形成了相应结论,以应对和指导不同应用场景.最后验证了资源管理方法的有效性.     

云计算数据中心的租户独享VPN的设计与研究

基于云计算数据中心领域在多VPN实例、多租户的情况下,VPN租户如何独享VPN系统、以及VPN租户如何动态分配各自用户VPN权限的方法研究。虚拟专用网络的原则和依据是首先必须符合国家等级保护的法律法规;其次必须满足云服务平台的环境需求;最后根据需求分析,必须满足云服务平台下各个租户、用户、互联网用户、平台间以及虚拟主机间的实际业务需求。接入平台的客户端都通过VPN方式进行访问,确保数据安全,该方案采用硬件VPN系统及虚拟化VPN组件和软件VPN客户端相结合的方式建设平台VPN系统,通过VPN系统的建设可实现网络资源的逻辑划分及安全隔离,使核心网与边缘网络形成一个整体。     

面向多租户的多层次可伸缩SaaS软件架构研究

针对SaaS模式下面向多租户的SaaS软件如何随着用户数量及请求规模的变化而进行自适应伸缩的问题,在分析SaaS软件的可伸缩需求的基础上,从一个较为宏观的角度提出了一个面向多租户的多层次可伸缩SaaS软件架构.该软件架构将SaaS软件的伸缩层次划分为业务层和数据层两个部分,从应用、流程和构件等三个粒度研究多粒度业务层的动态可伸缩实现方法;在数据层,以内存数据库子层、全局数据库子层以及数据引擎构建一个面向多租户的数据库开发框架,实现租户数据的隔离、存储以及一致性.基于该软件架构,开发了一个面向物流行业的多租户SaaS原型系统,验证了其有效性和可用性.     

SaaS云服务环境下的管理信息系统方案研究

为了降低北京大学各院系等基层单位的信息化门槛,深化学校信息化建设,根据学校院系管理的需求特点,提出了一种SaaS云服务环境下的管理信息系统方案.探讨了方案的多层次可扩展的应用架构,并且重点研究了其中的3个关键技术:多层次数据存储模型,基于IAAA的多租户访问控制策略MT-IAAA,以及面向多租户的可配置方法和运行机制.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the