Configuring Linux to Enable Multipath I/O
存储是数据中心关键组成部分，并且SAN可以对多重冗余数据路径（multiple redundant data paths）提供极好地高可用性和负载均衡。为了在Linux 操作系统环境中充分利用这些好处，企业IT部门可以使用一些程序来建立多路径I/O的配置。
在数据中心环境中，为了将宕机时间和服务中断带来的损失最小化，IT部门必须避免在任何高可用性系统中使用单点故障（single point of failure）。对于SAN，管理员可以在服务器和存储系统之间建立多重冗余数据路径（multipaths），来避免硬件错误导致的数据流的中断。
为了管理一个multipath I/O配置，管理员应该要保证服务器操作系统支持multipath I/O 并正确配置，来从存储系统中获得数据，在失败的时候以后第二条路径可以作为备用。对于linux系统，有两种multipath I/O程序可以使用：device mapper multipath 和EMC PowerPath 软件。这篇文章提供了这两种应用的概述，并且比较了他们之间的优缺点。
Understanging the basics of multipath I/O
在下面的例图中，是一个典型的高可用性SAN存储的配置。它包括一个Dell PowerEdge 服务器（有几个HBAs----host bus adapters）,两个FC交换机，以及一个Dell/EMC CX系列的存储阵列。一个集群应该包括多个PowerEdge 服务器。正如例图所示，在服务器和存储系统之间有多个数据路径，存储系统提供了必要的冗余（Redundancy）。In such a configuration —for example, a PowerEdge server running Red Hat?Enterprise Linux 4—a logical unit (LUN) on the CX storage that is assigned to the server is detected as many times as there are paths available.的那个一个HBA 驱动加载时，SCSI设备中间层会启动对总线的扫描，然后通过每个可用的路径侦测到所有被分配的存储LUN。于是，就会有很多SCSI磁盘设备被操作系统注册。在例图1中，有四个路径通往存储系统，因此一个被指派给特定的服务器的LUN就被侦测到了四次。这四个SCSI设备被HBA驱动侦测到，并都被注册到操作系统了。
对然冗余路径带来了好处，但是它带来的挑战也是必须要考虑的。这些挑战包括为I/O 识别一个特定的设备，管理同一个物理设备的多重设备（managing multiple devices of the same physical device.）
不同的存储系统管理一个特定LUN的多个路径的方式不尽相同。一些系统将路径视为isotropic or symmetric，所有路径都视为相同的，这是所有的路径都是active的，I/O可以重定向到他们中的任何一个上。其他的存储系统，比如Dell/EMC CX系列FC系统，implement asymmetric arrays。在这些系统中，同一个LUN的路径被划分为active/passive，限制可以使用的设备（path）在任何时候都是总的设备（path）数量的一半。
Active/passive集群在一个时间点上只允许一个存储处理器属于active状态来执行I/O。
1.Traveling alone Please talk about traveling alone according to the following hints 1) Describing traveling alone 2) Advantages of traveling alone 3) How to prepare for a solo travel Nowadays,traveling alone is not uncommon, most people love traveling alone becaus e of the feeling on their roads.Traveling alone can open you up to unique personal ex perience in new place. If you love freedom,Traveling alone is your best choice.When you are traveling alone, your time and budget（预 算） are your own! It's all up to you how much time to spend someplace, what your daily modes（方 式） of travelwill be！ And it's easier to make friends with the locals. Solo travel can be a great opportunity for reflection and moving at an individual pace. Traveling by y ourself, you only have to please yourself. But you should prepare for your solo travel ,too.Without a thoughtful preparation,your traveling won’t be so successfully. You ha ve to prepare all your need before setting off.Like medicine,ID card,passport,camera and so on.A solo travel means you may be lonely and bored,so bring some interesting magizines to make your travel more funny. And the last,do what you want! Teacher’s Questions: 1)Would you like to travel in a group or alone? (Why or Why not?) Yes.Because it’s an unusual experience for me to learn how to be more independent,and I also enj oy the unconstraint. 2) What places are your ideal destinations if you are traveling solo? Why do you t hink so? HaiNan island.Because the scenery there is very charming and I can eat bananas and coconut as many as I can. 2. Staying Healthy The following are ways some people try to stay healthy. Please offer your comments. 1) Regular exercise 2) Balanced diet 3) Good living habit Health is the most precious（珍贵 的） wealth we have,so it is important to take good care of our health,here are some advice to help you to stay healthy. There is an old saying says:An apple a day keep doctor away.A balance diet is import
Topics for Oral test 1. Which great leader do you admire most? What qualities did/does he/she have? bill gates 2. Which do you cherish more, your friendship with a good friend or your romantic relationship? obviously, friend is easy to make, but lover is kind of hard to seek for. Since relationship between friends might be not that close compared to romantic relationship, I will probably take it serious and cherish this sweet relationship. Also, I believe that my friends will support me and our relationship won’t be tense and freezing because of this. As the Chinese saying goes, once you got a boyfriend or a girlfriend, you may leave your friends out of your mind. I partly agree this, and when I fall in love, especially at the very beginning, I think I will cherish it more than friendship. 3. What factors would you consider first if you were to find a job (even a part-time job)? I will first consider whether this company and the offered position is high potential. I think high potential is a quality that is vital for the company’s future development and its personnel’s self improvement. Every one need a room to promote and realize one’s self-value. Another factor I concern is—its location. I’d like to work and live in big cities because big cities offer so many opportunities and a higher salary while small cities can’t. 4. Whom do you usually turn to when in trouble, vour parents or your friends? They know me better than anyone else and their vision is wide, their thoughts are mature.
A NSWER KEY Part One: Essay Writing 1 An Introduction to Writing Activity (Point and Support in a Paragraph), pages 5–6 Point:There are drawbacks to moviegoing. Support: 1. Inconvenience b. Long time to find parking spot and long walk to theater d. Sticky floor 3. Other moviegoers a. Running kids b. Laughing, shouting teenagers Activity (Introductory Paragraph), 8 1. c 2. b 3. a 4. a. Inconvenience of going out b. Temptations of the theater c. Behavior of some patrons Activity (Body: Supporting Paragraphs), 9–10 1. To begin with, I just don’t enjoy the general hassle of the evening. 2. b. Parking lot is always jammed d. Tickets may sell out, and theater is crowded e. Tickets cost up to $8 each 3. Second, the theater offers tempting snacks that I really don’t need. 4. b. 2) chocolate bars 3) Milk Duds 5. Many of the other patrons are even more of a problem than the concession stand. 6. a. Little kids race up and down the aisles b. Teenagers talk back to the screen, whistle, make funny noises Activity (Concluding Paragraph), 10 1. a 2. c Review Activities, 18–20 Answers will vary. 2 The Writing Process Activities (Freewriting, Questioning, Making a List, Clustering, Scratch Outline), 25–31 Answers will vary.
多路径配置与管理
目录 1. 多路径概述 (1) 1.1 什么是多路径 (1) 1.2 业界的MPIO (1) 2. Windows Server 2008/2012 MPIO配置与管理 (1) 2.1 MPIO安装 (1) 3.2 MPIO配置 (5) 3.3 MPIO切换策略介绍 (13) 4. RedHat Linux MPIO配置与管理 (15) 4.1 多路径软件的安装 (15) 4.2 Multipath.conf配置文件解析 (16) 4.3 配置multipath.conf (19) 4.3.1 快速配置 (19) 4.3.2 高级配置 (19) 4.4 多路径管理 (24) 4.5 多路径磁盘的使用 (25) 5 各产品multipath.conf参数配置 (26) 5.1 INSPUR AS500G/E、AS520G/E (26) 5.1.1 Windows客户端 (26) 5.1.2 Linux客户端 (27) 6 Multipath Issues Troubleshooting (27) 6.1在群集中保持多路径设备名称一致 (27)
1. 多路径概述 1.1 什么是多路径 普通的电脑主机都是一个硬盘挂接到一个总线上，这里是一对一的关系。而到了有光纤组成的SAN环境，或者由iSCSI组成的IPSAN环境，由于主机和存储通过了光纤交换机或者多块网卡及IP来连接，这样的话，就构成了多对多的关系。也就是说，主机到存储之间的IO由多条路径可以选择。每个主机到所对应的存储可以经过几条不同的路径，如果是同时使用的话，I/O流量如何分配？其中一条路径坏掉了，如何处理？还有在操作系统的角度来看，每条路径，操作系统会认为是一个实际存在的物理盘，但实际上只是通向同一个物理盘的不同路径而已，这样在使用的时候，就给用户带来了困惑。多路径软件就是为了解决上面的问题应运而生的。 多路径管理MPIO（Multi-Path），对支持MPIO的存储设备，MPIO自动发现、配置和管理多个存储路径，提供IO高可靠性和负载均衡。MPIO方案的实现有三个部分组成，分别为存储系统部分、存储软件部分和操作系统部分。 多路径的主要功能就是和存储设备一起配合实现如下功能： 1.故障的切换和恢复 2.IO流量的负载均衡 3.磁盘的虚拟化 在RedHat和Suse的2.6内核中都自带了免费的多路径软件包，并且可以免费使用，同时也是一个比较通用的包，可以支持大多数存储厂商的设备，即使是一些不是出名的厂商，通过对配置文件进行稍作修改，也是可以支持并运行的很好的。 1.2 业界的MPIO 由于多路径软件是需要和存储在一起配合使用的，不同的厂商基于不同的操作系统，都提供了不同的版本。并且有的厂商，软件和硬件也不是一起卖的，如果要使用多路径软件的话，可能还需要向厂商购买license才行。，业界比较常见的MPIO功能软件有EMC 的PowerPath，IBM的SDD，日立的Hitachi Dynamic Link Manager和广泛使用的linux开源软件device-mapper。 2. Windows Server 2008/2012 MPIO配置与管理 2.1 MPIO安装 Windows Server 2008系统包含MPIO软件，不需要使用其它的MPIO软件。具体安装步
Device-Mapper Multipath 一DM-Multipath概述 DM-Multipath 能够使服务器与存储控制器间multiple I/O路径变成一个单一的设备。I/O 路径是由线缆、交换机、控制器组成的物理SAN。DM-Multipath能够创建一个由I/O路径聚集组成的新设备。 在不配置DM-Multipath的情况下，盘阵的一个LUN从控制器主机端口映射到服务器，在操作系统里被识别成一个独立的设备，这样就会造成同一个LUN通过盘阵不同的主机端口映射到服务器被识别成不同的设备。作为一种解决方案，DM-Multipath通过在物理设备上创建一个单独的多路径设备，提供了一种在逻辑上管理I/O路径的机制，这样盘阵的LUN 从控制器主机端口映射到服务器，在操作系统里被识别成一个多路径设备。 每个多路径设备拥有一个唯一标识的World Wide Identifier（全球识别号，WWID），默认情况下，多路径设备的名称被设置成它的WWID。通过修改multipath.conf文件中的user_friendly_names选项参数，可以设置多路径设备的别名为mpathn。例如如下的配置环境：一个拥有两个HBA的服务器通过一个未配置zone的FC交换机连接到有两个主机端口的盘阵控制器（盘阵仅有一个LUN）上，在操作系统里能够看到四个设备：/dev/sda, /dev/sdb, dev/sdc, 和/dev/sdd。通过配置multipath.conf文件，DM-Multipath就会创建一个拥有WWID 的多路径设备，多路径设备受控于DM-Multipath，我们可以在三个不同目录查看多路径设备：/dev/目录；/dev/mapper/mpathn,/dev/mpath/mpathn；/dev/dm-n.。使用/dev/mapper目录中的设备名对多路径设备进行管理，如创建逻辑卷，创建文件系统等。/dev/mpath将所有的多路径设备放到该目录下，只是便于查看，不要使用该目录下的设备进行创建逻辑卷，创建文件系统等操作。/dev/dm-n只是用于系统内部的使用，不要使用这里面的设备。 二DM-Multipath功能 DM-Multipath能够提供： 冗余 在active/passive模式中，DM-Multipath提供失效转移功能。active/passive环境中，在任何时间内只有一半的I/O路径被使用。如果一个I/O路径内的元素例如线缆、交换机、控制器失效，DM-Multipath切换到轮换的路径。 提高性能 DM-Multipath能够被配置在active/ active模式下，在这种模式下，I/O路径处于round-robin方式。DM-Multipath能够动态的平衡I/O负荷。 三DM-Multipath应用环境示例 ①Active/ Passive Multipath Configuration with One RAID Device 该配置里服务器有两个HBA，两个SAN交换机和两个控制器。从服务器到一个RAID存在两个I/O路径。如下图：
Device Mapper Multipath配置指导书 华为技术有限公司 版权所有侵权必究
Device Mapper Multipath配置指导书文档密级：内部公开修订记录
目录 目录 (1) 前言 (3) 1检查系统DM-Multipath (4) 1.1检查DM-Multipath是否正确安装 (4) 1.2查看DM-Multipath版本 (5) 1.3检查DM-Multipath配置文件 (5) 1.4检查DM-Multipath服务multipathd是否开机启动 (5) 2修改DM-Multipath配置 (6) 2.1修改multipath.conf文件 (6) 2.1.1 CentOS 6.3 对接阵列S5800T 配置 (7) 2.1.2 NeoKylin Advance Linux Server V5.6 对接阵列18500配置 (8) 2.2 FAQ (9) 2.2.1如何获取阵列vendor及product (9) 2.2.2 DM-Multipath可用的磁盘在哪里 (9) 3注意事项 (11) 3.1集群应用 (11) 3.2 DM-Multipath与UltraPath共存 (11) 3.3设备屏蔽 (11) 3.4驱动超时参数 (11) 3.4.1 FC驱动 (11) 3.4.2 ISCSI驱动 (12) 附录A DM-Multipath盘符绑定 (13) 附录B DM-Multipath磁盘屏蔽 (14) 附录C 常用命令 (16)
关键词： Device Mapper Multipath、配置 摘要： 本指导书是针对Linux系统自带多路径Device Mapper Multipath对接我司阵列，配置操作过程中需要的步骤、注意事项等提供的指导，本指导书描述了Multipath配置过程及注意事项。 缩略语清单： DM-Multipath(Device Mapper Multipath )：Linux系统自带多路径 LUN(Logical Unit Number): 逻辑单元号 ALUA（Asymmetric Logical Unit Access）：非对称逻辑单元 IALUA（Implicit Asymmetric Logical Unit Access）：隐式ALUA EALUA（Explicit Asymmetric Logical Unit Access）：显式ALUA 参考资料清单： 无。
英文论文Introduction的写作技巧 —as a "hook" to attract the readers 学术论文中的引言(Introduction)是对全文内容和结构的总体勾画（The purpose of the Introduction is to stimulate the reader’s interest and to provide pertinent background information necessary to understand the rest of the paper.Without an introduction it is sometimes very difficult for your audience to figure out what you are trying to say. There needs to be a thread of an idea that they will follow through your paper）。The introduction section shows the questions that shoul d be answered for the readers once they finish reading the “Introduction”. 1 引言的内容与结构布局 引言的主要任务是向读者勾勒出全文的基本内容和轮廓。它可以包括以下五项内容中的全部或其中几项： 1）介绍某研究领域的背景、意义、发展状况、目前的水平等； 2）对相关领域的文献进行回顾和综述，包括前人的研究成果，已经解决的问题，并适当加以评价或比较； 3）指出前人尚未解决的问题，留下的技术空白，也可以提出新问题、解决这些新问题的新方法、新思路，从而引出自己研究课题的动机与意义； 4）说明自己研究课题的目的； 5）概括论文的主要内容，或勾勒其大体轮廓。 如何合理安排以上这些内容，将它们有条有理地给读者描绘清楚，并非容易之事。经验告诉我们，引言其实是全文最难写的—部分。这是因为作者对有关学科领域的熟悉程度，作者的知识是渊博、还是贫乏，研究的意义何在、价值如何等问题，都在引言的字里行间得以充分体现。 我们可以将引言的内容分为三到四个层次来安排。第一层由研究背景、意义、发展状况等内容组成，其中还包括某一研究领域的文献综述；第二层提出目前尚未解决的问题或急需解决的问题，从而引出自己的研究动机与意义；第三层说明自己研究的具体目的与内容；最后是引言的结尾，可以介绍一下论文的组成部分。 第一层：1) Introducing the general research area including its background, importance, and p resent level of development……2) Reviewing previous researc h in this area……… 第二层：Indicating the problem that has not been solved by previous research, raising a relevant
1.Shared Bikes in Foshan 佛山共享单车 My name is Zhong Jian. I’m from Big Data Class 2,Group 5.I like playing basketball and listening to music.Thank you. That’s my introduction.Now ,let’s welcome our next presenter. What do you think of going to the park by bike? As far as I am concerned, the development of Shared bikes in Foshan is very good. We can see Shared bikes everywhere on the street, we can use them easily, and the price is right. I think it is for this reason that Shared bikes have developed so quickly. Of course, the development and widespread use of Shared bikes has also facilitated our daily life. Do you think bike sharing is convenient? 2.Celebrating birthdays 庆祝生日 In my opinion, celebrating birthdays is a very common thing. This is because this day is the day we come to this beautiful world, so that we can have a mother's Day of course. When we celebrate our birthdays, we should also be grateful to our mothers for taking care of us. 就我看来，庆祝生日是一件很常见的事情。这是因为这一天是我们来到这个美丽世界的一天，让我们可以拥有眼前的一切。当然也是母亲的受难日，在我们庆祝自己生日的时候，我们也要感恩我们的母亲，感谢母亲对我们的照顾。 3.Business negotiation 商务谈判 For me, I think business negotiation is to exchange for their own interests. People on both sides want the other side to give in, not to give in. Business interests make everyone hope to get the result they want. However, the result is generally a compromise between the two sides. 对我来说，我认为商务谈判就是为了各自的利益而交流。两边的人都希望对方可以让步，而不希望自己让步。商业利益让大家都希望从中可以获得自己所想要的结局。可是，结果一般都是需要双方让步。 你认为商务谈判的主要意义是什么？ What do you think is the main significance of business negotiation? 4.Globalization 全球化 In my opinion, globalization is an inevitable trend, and no one can reverse it. Every country or country is the beneficiary or victim of globalization. The key is how to deal with the trend of globalization. I believe that only by taking the initiative to meet globalization can we benefit from it. 就我看来，全球化是一个必然的趋势，任何人都没有办法去逆转全球化。每一个或者每一个国家都是全球化的受益者，当然也可能是受害者，其中的关键是我们需要处理好如何去面对全球化这一趋势。我相信，只有积极主动去迎接全球化，才能够从中获利。 全球化中谁获得的利益最大？ Who gains the most in globalization? 5.Anti-smoking in Foshan 佛山禁烟 In my opinion, it is a good thing to ban smoking in Foshan. Of course, banning smoking is not only a good thing in Foshan, but also a good thing all over the world. Because smoking is harmful to health, second-hand smoke makes many innocent people die, which is the reality we have to face. If we see these facts, we will know that banning smoking is a good thing.
2014-2015学年下学期期末英语口语考试材料 zzqXQiang专用 1.It is said that a tough childhood might drive people to remarkable achievement and success. Do you agree with it or not? Why? 你同意“艰苦的童年也许能使人获得卓越成就”吗？ Yes, I agree. It’s true that difficul t childhoods do leave some people wounded and disadvantaged. But for others, a tough childhood actually drives them to remarkable achievement and success, because the tough childhood make them realize their full potential. So, hardships do not have to lead to failure and “well-being” is not always an advantage for us. All in all, i t’s the positive attitude towards life that really matters.是的,我同意。的确,这是真的，艰难的童年也让某些人受伤 也对他们不利（弱势群体）。但对另一些人来说,一个艰难的童年真正驱使他们非凡的成就和成功,因为艰难的童年使他们意识到他们的全部潜力。所以,困难没有导致失败,“幸福”是对我们来说不是一个优势。总之,积极的生活态度,真的很重要。 2.How much do you know about Anna Eleanor Roosevelt? 你对安娜·埃莉诺·罗斯福有何了解？ She was a former US “First Lady”. She lost her parents at the age of 10, and had a very unpleasant childhood, but she always kept a positive attitude towards life. After becoming the First Lady, she helped her husband manage the White House and raised 6 children. After her husband’s death, she spent the remainder of her life as a highly respected American spokesperson to the US. 她是美国前“第一夫人”。她10岁时失去了父母，过了一个很不愉快的童年，但她始终保持着积极的生活态度。在成为第一夫人，她帮助她的丈夫管理白宫和抚养6个孩子。在她丈夫死后，她将生命中剩下的时间都花在了美国，作为一个备受尊敬的美国发言人。 3.What has happened to the British pubs nowadays? Why? 如今英国的酒吧发生了怎样的变化？
《大学英语预备级1》课程开篇导学 Introduction of College English (Foundation) 一. 课程简介：General Introduction of this Course 1课程名称：大学英语精读课 Intensive Reading 2授课教材：《大学英语》（综合教程预备级）(上海外语教育出版社, 2003) College English -Integrated Course (foundation) 二. 课程任务：Content of Class 2.1 阅读：Reading Unit 1, Reading: A School with No Rules This unit discusses different ideas about discipline in schools by looking at the context of the “free” school of Summerhill where the students make the rules. This unit relates discipline to learning and motivation Unit 2, Reading: Fear of the Unknown, Not the known This unit has a mystery poem and a mystery story.
Unit 3, Reading: Reporting the News This unit looks at the job of newspaper reporting and the role of the international news agencies. Unit 4, Reading: Living in Virtual Reality This unit looks at the world of virtual reality: special helmets and clothing and computers. Unit 5, Reading: The Richest Man in the World This unit looks at the stories of how some of the richest people became rich. Unit 6, Reading: Practical Jokes This unit takes up the topic of practical jokes and reports on some tricks which have been played by the media. Unit 7, Reading: Life is Just a Dream In this unit there is an interview with a doctor who explains why we dream and what
NetApp Multipath最佳实践配置 1.Red Hat Enterprise Linux 6 with ALUA enabled sample configuration file The following file provides an example of the values you need to supply when your host is running Red Hat Enterprise Linux 6 with ALUA enabled: defaults { user_friendly_names no max_fds max flush_on_last_del yes queue_without_daemon no } blacklist { devnode "^hd[a-z]" devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*" devnode "^cciss.*" } devices { device { vendor "NETAPP" product "LUN" path_grouping_policy group_by_prio features "3 queue_if_no_path pg_init_retries 50" prio "alua" path_checker tur failback immediate path_selector "round-robin 0" hardware_handler "1 alua" rr_weight uniform rr_min_io 128 getuid_callout "/lib/udev/scsi_id -g -u -d /dev/%n" } } 2.Red Hat Enterprise Linux 6 without ALUA enabled sample configuration file The following file provides an example of the values you need to supply when your host is running Red Hat Enterprise Linux 6 and does not have ALUA enabled. Note: Unless you are running the iSCSI protocol and Data ONTAP operating in 7-Mode, you should have ALUA enabled. defaults {
大多数英文科技学术论文都可以使用一种所谓Introduction-Methods-Results and Discussion (IMRAD) 的形式，如下图的沙漏所示，先由普遍到具体问题，再由具体到普遍结论。 这里先总结Introduction的写法和注意事项。 与中文论文“简短”的“概述”(或“前言”)不一样，英文的Introduction内容通常较长。好的论文在Introduction部分很见功底，文献的阅读量、信息综合能力，可以给读者很多的信息量，因此写好它容不得半点马虎。 Introduction(说明综述)部分的内容通常用来为作者创造一个研究空间。先介绍目前的研究现状，然后指出存在的不足或尚没有解决的问题，最后再介绍“存在的问题”是“如何”被作者的研究所解决。因此，Introduction可以由这“三波”或者说“三部分”来组成。 具体而言，这“三波”如此展开： 第一波：提出研究现状和此研究的重要性 先通过陈述表明所要研究问题的重要性——当然这部分内容不是必须，并介绍此领域的研究现状，具体可参考文献综述引用。 研究问题要与自己的研究内容高度相关，时态一般可用一般现在时，并通过很确定的语气和具体的形容词来强调研究的重要生。
The flow of foams is seen in many process, and its use in major industries means that an understanding of foam rheology is of paramount importance. 第二波：强调有必要解决存在的问题 指出该研究目前存在的问题，可以通过提问的方式或者通过某种方式扩展此领域已有知识和结论。 这一波非常重要，只有指出存在的问题或尚待解决的问题，才能突显出自己的研究价值。在这一部分的写作时，一般通过转折词来表示过渡，并在指出问题时使用负面的词汇。 … ; however, the relationship between emergence and soil temperature has not been investigated previously… In contrast to the extensive literature describing ….., little attention has been paid to…第三波：介绍作者自己的研究内容 介绍作者的研究目的和大致的研究内容。也可以在此部分表明自己的研究假设前提，宣布自己的主要研究发现、它们的价值，如有需要，也可以介绍论文的框架结构——方便读者了解复杂的文章结构。 这部分的内容主要用来介绍作者如何“填补”提出的“问题”或“不足”。 This paper presents the results of an extensive experimental program… 关于此处的时态，比如是presents还是presented? 即是一般过去时还是一般现在时？一般而言： ?如果主语是paper, article, thesis, report等指代文章本身的抽象词汇，使用一般现在时； ?如果主语是实验调查本身，比如study, experiment, investigation等具体词汇，使用一般过去时或一般现在时都可以。 万能法则：此处的时态如果拿不准，一直使用一般现在时。
1.What are the advantages and disadvantages of online learning? In online learning, we can learn something at the time and place ,that is most convenience to us .On the other hang ,online learning offers the flexibility(灵活性)we need ,Every thing has two slides. In online learning, you have to have some special skills ,You have to be self-motivated(自我激励)、responsible for your own learning and have good time management skills. 2、If you were to go to an interview, what would you do to make a good impression? Here are many ways for make a good impression, First, we have to wear a formal wear .we want to be a polite person. And we should keep smiling. Then, we do not be afraid ,answer questions calmly. Last ,the most important thing is ,we must believe ourselves can do it。 3、What do you think parents should do when children do something wrong, such as telling lies? As parents, first we should love our children ,whatever children do something wrong ,we can not hit our children. When children do something wrong ,first ,we should analyze why they do, then we should make a communication with our children,let them understand the harm. 4、Ways to make my university life more rewarding. First I will set goals ,and I will try my best to achieve it.Then I will take part in all kinds of activities if I have time and I will do it well. the