Recsplorer:Recommendation Algorithms Based on Precedence Mining
1. Introduction
Thank you very much, Dr. Li, for your kind introduction. Ladies and gentlemen, Good morning! I am honored to have been invited to speak at this conference. Before I start my speech, let me ask a question. Do you think recomemdations from others are useful for your internet shopping? Thank you. It is obvious that recommendations play an important role in our daily consumption decisions.
Today, my topic is about Recommendation Algorithms Based on Precedence Mining. I want to share our interesting research result on recommendation algorithms with you. The content of this presentation is divided into 5 parts: in session 1, I will intruduce the tradictional recommendation and our new strategy; in session 2, I will give the formal definition of Precedence Mining; in session 3, I will talk about the novel recommendation algorithms; experimental result will be showed in session 4; and finally, I will make a conclusion.
2. Body
Session 1: Introduction
The picture on this slide is an instance of recommemdation application on amazon.
Recommender systems provide advice on products, movies,web pages, and many other topics, and have become popular in many sites, such as Amazon. Many systems use collaborative filtering methods. The main process of CF is organized as follow: first, identify users similar to target user; second, recommend items based on the similar users. Unfortunately, the order of consumed items is neglect. In our paper, we consider a new recommendation strategy based on precedence patterns. These patterns may encompass user preferences, encode some logical order of options and capture how interests evolve.
Precedence mining model estimate the probability of user future consumption based on past behavior. And these probabilities are used to make recommendations. Through our experiment, precedence mining can significantly improve recommendation performance. Futhermore, it does not suffer from the sparsity of ratings problem and exploit patterns across all users, not just similar users.
This slide demonstrates the differences between collaborative filtering and precedence mining. Suppose that the scenario is about course selection. Each quarter/semester a student chooses a course, and rates it from 1 to 5. Figure a) shows five transcripts, a transcript means a list of course. U is our target student who need recommendations. Figure b) illustrates how CF work. Assume similar users share at least two common courses and have similar rating, then u3 and u4 are similar to u, and their common course h will be a recommendation to u. Figure c) presents how precedence mining work. For this example, we consider patterns where one course follows another. Suppose patterns occour at least two transcrips are recognized as significant, then (a,d), (e,f) and (g,h) are found out. And d, h, and f are recommendation to u who has taken a, g and e.
Now I will a probabilistic framework to solve the precedence mining problems. Our target user has selected course a , we want to compute the probability course x will follow, i.e., Pr[x|a]. howerve, what we really need to calculate is Pr[x|a﹁X] rather than Pr[x|a]. Because in our context, we are deciding if x is a good recommendation for the target user that has taken a. Thus we know that our target user’s transcript does not have x before a. For instance, the transcript no. 5 will be omitted. In more common situation, our target user has taken a list of co urses, T = {a,b,c,…} not just a. Thus, what really need is Pr[x|T﹁X]. The question is how to figure out this probability. I will answer it later.
Session 2: Precedence Mining
We consider a set D of distinct courses. We use lowercase letters (e.g., a, b, … ) to refer to courses in D. A transcript T is a sequence of courses, e.g., a -> b -> c -> d. Then the definition of Top-k Recommendation Problem is as follows. Given a set transcripts over D for n users, the extra transcript T of a target user, and a desired number of recommendations k, our goal is to:
1. Assign a score score(x) (between 0 and 1) to every course x∈D that reflects how likely it is the target student will be interested in taking x. If x ∈T , then score(x) = 0.
2. Using the score function, select the top k courses to recommend to the target user.
To compute scores, we propose to use the following statistics, where x, y ∈D: f(x): the number of transcripts that contain x.
g(x; y): the number of transcripts in which x precedes course y.
This slide shows the calculation result of f(x) and g(x,y). For example, from the table, we know that f(a) is 10 and g(a,c) is 3.
We propose a precedence mining model to solve the Top-k Recommendation Problem. Here are some notation: x﹁y, which we have memtioned in session 1, refers to transcript where x occurs without a preceding y; x﹁y refers to transcript where x occurs without y following it. We use quantities f(x) and g(x,y) to compte probabilities that encode the precedence information. For instance, from formular 1 to 7. I would not tell the detail of all formulars. We just pay attention to formular 5, note that this quantity above is the same as: Pr[x﹁y|y﹁x] which will be used to compute score(x).
As we know, the target user usually has taken a list of courses rather than a course, so we need to extent our probability calculation formulars. For example, suppose T={a,b}, Pr[x﹁T] the probability x occurs without either an a or b preceding it; Pr[x﹁T] the probability x occurs without either an a or b following it. This probability can be calculated exactly. So how to calculate it?
Session 3: Recommendation Algorithms
Let’s review session 2. The main goal of the recommendation algorithms is to calculate the score(x), and then select the top k courses based on these scores. Traditional recommendation algorithms compute a recommendation score for a course x in D only based on its frequency of occurence. It does not take into account the courses taken by the target user.
Our recommendation algorithms called SingleMC conquer the shortcoming of the traditional ones. It computes the score(x) using the formular 5. The detail is as follows: a student with a transcrip T of taken courses, for the course y ∈T, if y and x appear together in transcripts satisfies the threshold θ, then compute the Pr[x﹁y |y﹁x], reflecting the likelihood the student will take course x and ignoring the effect of the other courses in T; finally the maximum of Pr[x﹁y |y﹁x] is choosen as the score(x).
Here is the calculation formular of score(x) of SignleMC. For example, with the higer score, d will be recommended.
Another new recommendation algorithm named Joint Probabilities algorithm, JointP for short, is proposed. Unlike SingleMC, JointP takes into account the complete set of courses in a transcript. In formular 12, we cannot compute its quantity exactly, Remember this problem we have mentioned. Our solution is to use approximations. This slide is about the first approximating formular. And this the second approximating formular.
The system is courseRand, and data set for experiment contains 7,500 transcripts.
This slide shows the new recommendation algoritms with black color and the traditional ones with blue color.
The chart on this slide indicates our new recommendation algorithms beat the traditional ones in precision, because the former ones exploit patterns across all users, while the latter ones just use the similar users.
The chart on this slide points out our new recommendation algorithms also beat the traditional ones in coverage for the same reason.
Session 5: Conclusion and Summary
In conclusion, we proposed a novel precedence mining model, developed a probabilistic framework for making recommendations and implemented a suite of recommendation algorithms that use the precedence information. Experimental result shows that our new algorithms perform better than the traditional ones, and our recommendation system can be easily generalized to other scenarios, such as purchases of books, DVDs and electronic equitment.
To sum up, first, I introduced the motivation and the outline of work; second, I gave the definition of precedence mining model; third, I described some new recommendation algorithms using precedence information; forth, I showed our experimental results to compare the new algorithms with traditional ones. Finally, I made a conclusion of our work..
That’s all. Thank you! Are there any questions?
最新学术会议领导讲话稿 在科学发展早期,学术会议兴起于无形学院式的学术聚会,随着现代科学的发展,学术会议被逐步制度化,会议的目的、形式、功能等被格式化,显示出独有的特征。下面是给大家整理的最新学术会议领导讲话稿，仅供参考。 最新学术会议领导讲话稿【篇一】 各位领导、各位来宾、各位同行： 盛夏时节逢盛会，洪湖岸边迎嘉宾。今天我们在这里齐聚一堂，隆重举行焦作市年年会开幕仪式，这是焦作市医学会的一件盛事。年会选在医院召开，更是我院的荣誉。 借此机会，我代表我院全体同仁，向参加会议的各位领导、嘉宾及学会会员表示热烈的欢迎!向长期支持我院建设发展的各级领导、专家表示衷心的感谢! 焦作2006年学术会议，是焦作医学会召开的一次重要会议，来自焦作各县、市、区医院的各位同仁会聚一堂，进行学术交流，相互研究探讨，的确是学界彼此促进、共同提高的一个重要载体和大好时机。这次还特邀了的知名教授专家参加，将有效提升此次学术交流的整体层次，提高各参会医院的诊断技术水平，并推动医院的整体业务发展。医院作为承办单位，其拥有的先进专科设备，将为此次年会提供一个良好的交流平台。各位领导，各位专家，我为此次焦作放射学年会的胜利召开感到无比荣幸，我们将一如既往地积极
参加医院举办的各项活动，并尽最大努力给予支持，做好各项协助工作。最后，预祝此次会议圆满成功!谢谢!我们承办方，精心策划，科学组织，热情服务，确保本次会议圆满成功，取得预期的效果。同时要求我们，要以研究推进工作，以工作带动研究，加快临床神经外科建设与改革的速度，加大医学教育与科研的力度，从而赢得患者更大的满意度，为医院的整体发展做贡献，为该学科理论与实践发展注入新的元素，做人民满意的科研型医务工作者，为促进我国医学事业的发展，提高和带动本地区在临床神经外科医学上的研究作出我们应有的贡献! 预祝会议圆满成功! 谢谢大家。 最新学术会议领导讲话稿【篇二】 尊敬的各位领导、各位来宾 女士们、先生们： 大家好! 正当大部地区还处在骄阳似火的炎炎夏日时，塞外明珠的美丽古城大同已是凉风习习、气候宜人。今天，我们云集于此，隆重举行山西省第十六届眼科学术会议，这是我省眼科界两年一度的盛大聚会。首先，请允许我代表山西省医学会眼科专业委员会和本届大会组委会，向与会的各位领导嘉宾、专家教授、眼科同道和参展厂商表示热烈的欢迎;我们还要对本次大会的东道主大同市人民政府、大同市卫生局、大同市第三人民医院表示诚挚的谢意，他们为会议的
英语模拟国际会议讲稿 Company Document number：WUUT-WUUY-WBBGB-BWYTT-1982GT
英语模拟国际会议 主持人：王×会议出席人：朱××会议中提问者两人：董×、赵××休会中途与嘉宾交谈两人：张×、唐×× 会议结束提问者：余×、龚× 主持人王×：Ladies and Gentleman: May I have your attention please Our conference will begin in a few minutes. All the presenters are requested to be seated. Let me introduce myself,i am wang yuan from SCNU,it’s a privilege for me to chair this session. Once the ceremony has started,you are refrained from taking pictures, using flashbulbs or leaving your seats. guests, distinguished delegates, ladies and gentlemen, and all the friends:At this special time of wonderful June, in this grand hall of the beautiful city, our respectable guests are here getting together. Academic Seminars of CAS are organized by the Bureau of Personnel and Education of CAS, and held by the CAS research institutes. Now, first of all, please allow me to give our hearty welcome to all of you present, and thank you, for your friendly coming. We feel so proud, and appreciated as well to be the host of the event. For this conference, we are following the agenda here. The meeting is supposed to last for five days，it is the first congress which covers the true sense of psychological education、moral education,basic education
Introducing a speaker (Sample)
Having spoken to over a million people, give or take a few thousand, our speaker is known for her ability to relate to audiences by leaving them in the "interested student of life position." Her passion is contagious! And, she claims to have many great passions in life–including her husband, two children, sailing and watching her identical twin sister get older. So to speak to you on "Speak and Grow Rich," Please join me in welcoming–from the coast of Massachusetts –author, educator, business owner, wife and first mate, Nancy Hunter Denney. 其它个人信息 表示欢迎 He has co-authored over 300 peer-reviewed publications and 75 issued U.S. patents, and is the recipient of several awa rds and honors including the Eli Lilly Award in Biological Chemistry and the Pure Chemistry Award from the American Che mical Society; the Allan P. Colburn Award and the Profession al Progress Award from the American Institute of Chemical En gineers; and the Alan T. Waterman Award from the National S cience Foundation. He is an elected member of the American Academy for Arts and Science and the National Academy of En gineering. Over the past two decades, he has co-founded four biotechnology companies (Kosan Biosciences (KOSN), Alvine Pha rmaceuticals, Flamentera AG, Sitari Pharmaceuticals), and was the founding President of the non-profit Celiac Sprue Researc h Foundation. Dr. Zhang is a Professor in the Departments of Chemical Eng ineering Dalian University of technology, panjin campus, and assistant dean of Departments of Chemical Engineering. He rec eived his PhD in chemical engineering in 1990 at (place fro m he obtain degree.) After completing postdoctoral studies ch emical engineering from UK, he joined Dalian University in 1992. His research on fuel cells has opened the door to fundamentally new approaches for engineering of fuel cell
国际会议作报告英语发言 稿 Prepared on 22 November 2020
Thankyou,prof.….Mynameis…..I’m from…..Iamverypleasedtobeheret ojointhisforum.Thetopic,themainpartsofmyresearchareaboutsoilpavement. Mypresentationwillincludethesefourparts: First,somebackgroundinformationaboutthisresearch;second,themainwork wehavedone;third,someconclusionswehavegotandthelast:innovationandpr esentationofourpublishedpapers. WhyIchoosethisitem,theexistingquantityofairfieldsisstillnotsufficientand theairfieldshavemanyshortcomingsespeciallyinwartime.Second,thecomple mentaryfacilities,suchashighwayrunwaysarefarlessthanairfields,however,, ,thefieldairfieldcanfillthevoidofairfieldandtheycanbecombinedtobeairfield network. ,convenientandvalidity,fastmeansthefieldairfieldmustbeconstructedasfasta spossible,convenientmeanstheconstructionshouldneedtheminimumequip ment,laborandmaterialsconsideringtheactualconstructioncondition,validit ymeanstheconstructedairfieldisabletosupporttheoperationofgivenaircraftin specificallytime. Justlikemanyotherterritories,
学术会议主席发言稿 【篇一：会议主席发言稿】 模拟国际会议会议主席发言稿 第七届中美关系论坛 开场白：good morning, ladies and gentleman. welcome to the 7th conference on sino [sa?n?]-u.s. relations, the theme of this conference is “china and us: partners, competitors or enemies”. its a great pleasure for me to be the conference chairman. 背景：we can realize gratefully that the relationship between china and us is very important, which has a key influence on the stabilization and peace in the world. 往届会议介绍：the conference has been held six sessions. the 1st conference on sino-u.s. relations was launched in 2003, organized by former u.s. president george bush initiatively. and this is the seventh. 1. lets welcome miss wang to give us the opening speech. 2. thank you. next welcome to a keynote speech, deputy secretary zhu please. 3. thank you for such an excellent speech. now professor zhang and professor fang will make an introduction for their research. 4. ok, what a good job. and now, its time for a question and answer session, any questions from everyone here? 5. thanks for the qa. our conference is drawing to a close, professor zhang will give us the closing speech, please. 结束语：we can say, without exaggeration, that it is a conference of great benefits. over the past 10 years, although ups and downs in sino-us relations, but cooperation has been irreversible [?r?v??s?b(?)l] trend in the relations between the two countries. this is the end of this session, i hope to see you next time. thank you. 过去10年中，尽管中美关系出现过起伏，但合作一直是两国关系中不可扭转的趋势。 【篇二：学术会议主持人发言稿】
英文学术会议开场的演讲 稿 Prepared on 22 November 2020
Good morning, ladies and gentleman. Welcome to Xian, a beautiful city of China. I’m Xinpei Zhang. It is a great pleasure to participate in the Mathematics Conference as the chairman. And I really enjoy staying here with you this morning. The Mathematics Conference has been held 4th times by Shaanxi Normal University since 2008. The purpose of the conference is to share our experiences and knowledge in regard to the theory, frontier developments and researches, as well as possible applications of them in solving practical problems. A lot of current issues have been d i s c u s s e d,a n d s o m e o f t h e m h a v e b e e n e f f e c t i v e l y s o l v e d. Today, as the first time of the conference debut in this city, we’ll have a unique session. The topic of prepared presentations is Mathematics. Today, speakers will share their thoughts on how to effectively run models in different issues and give a reasonable ,we’ll have a Q&A session,w hich allows the everyone to ask some questions you may be interested. I am sure that you will find some topics to be presented both interesting and informative. Now,Let me introduce the first speaker,who is very very rich,not in dollars,but in knowledges and experiences,He got his in financial economics at the UCB,followed by a series of teaching and research positions at MIT and Harvard. Please dont hesitate to join me in welcoming our first speaker, , whose topic is entitled threshold effect between the scale of shadow banking and the stability of the banking system. Welcome.
国际会议发言稿英文(精选多篇) 第一篇：国际会议--英文 表示欢迎：good morning, ladies and gentlemen, i’m privileged to welcome you all to “the current status and future development of cotton machinery” conference. 自我介绍：let me introduce myself i am dr lifrom beijing, china, and i am going to be the chair for this morning’s session. 介绍议题： this conference will focus on the discussion of the various aspects of cotton machinery. it includes the application of cotton machinery and the current status.and we will also discuss the prospect of cotton machinery. 介绍报告人： now it gives me great pleasure to introduce today’sparticipants. they are :han dan, the director general of the united nations industrial development organization(联合国工业发展组织总干事) zhang hui, president of china power investment group company. shang fengjiao, professor of physics ,head of american nuclear energy association. now, we welcome the opening of han dan do for us（现在，我们欢迎aa 为我们做致开幕词） aa上台
英文国际会议演讲稿范文 英文会议演讲稿篇一：英文国际学术会议开幕词演 讲稿 Distinguished guests, distinguished delegates, ladies and gentlemen, and all the friends: At this special time of wonderful August, With a pleasant subtropical climate in Xiamen, Our respectable guests are here getting together , undertaken by XMU , the 2014 10th International Conference on Natural Computation and the 2014 11th International Conference on Fuzzy Systems and Knowledge Discovery , will be open. Now, First of all, please allow me to give our hearty welcome to all of you present, and thank you , for your friendly coming. We feel so proud, and appreciated as well to be the host of the event. It is a great honor for us to have all you here to attend this conference, of which the theme is the academic exchange about the advanced technologies on Computer Science. Here I’d be delighted to introduce our conventioneers in brief. Apart from
国际会议英文发言稿 篇一：英文国际学术会议开幕词演讲稿 Distinguished guests, distinguished delegates, ladies and gentlemen, and all the friends: At this special time of wonderful August, With a pleasant subtropical climate in Xiamen, Our respectable guests are here getting together , undertaken by XMU , the XX 10th Interna tional Conference on Natural Computation and the XX 11th International Conference on Fuzzy Systems and Knowledge Discovery , will be open. Now, First of all, please allow me to give our hearty welcome to all of you present, and thank you , for your friendly coming. We feel so proud, and appreciated as well to be the host of the event. It is a great honor for us to have all you here to attend this conference, of which the theme is the academic exchange about the advanced technologies on Computer Science. Here I’d be delighted to introduce our conventioneers in brief. Apart from our faculty and
国际会议的最终演讲稿 good afternoon ladies and gentlemen: my name is shaoshasha,i am a senior in china jiliang university and majoring in business management. i am honored to be here to deliver an introduction of our group case study .this is our team member tanglihua ,sundan and me as we all know. sony and lenovo both enjoy high reputation among the mass. therefore, as a famous brand over asia, sony competes with lenovo in domestic market only by obtaining the knowledge of the comparative disadvantage and corresponding betterment, and this is the primary issue we should to settle. taking the customers#39; demand as an base, we launched a market research and thereby get an understanding that the technical standard is the computer’s feature. since qfd is of great usefulness in analyzing dates, we apply it in our study in order to figure the approach of sony‘s improvement. in addition, quality function deployment is to help transform the customer wants into engineering characteristics for a product or service, prioritizing each product or service characteristic while simultaneously setting the development targets for the product
2020 学术会议领导讲话稿文档 SPEECH DRAFT
学术会议领导讲话稿文档 前言语料：温馨提醒，演讲又叫讲演或演说，是指在公众场合，以有声语言为主要 手段，以体态语言为辅助手段，针对某个具体问题，鲜明、完整地发表自己的见解 和主张，阐明事理或抒发情感，进行宣传鼓动的一种语言交际活动。魅力演讲可以 让演说者能够更好的抓住核心，把握本质，从根本上解决问题！把演讲的效果，发 挥到极致，充分展现演讲魅力，释放能量，从而产生最大影响力！ 本文内容如下：【下载该文档后使用Word打开】 学术会议领导讲话稿(一)： 各位领导，各位来宾，各位代表，女士们，先生们，大家好。 由国际易学联合会主办的第x届易学应用与经济发展国际学术研讨会在我们的祖国的首都北京大学隆重开幕了，在此，我谨代表易元亨国学院和席学易国际易学研究院向本次大会表示衷心的祝贺，同时向参会的各位领导、各位来宾、各位专家学者表示最诚挚的问候和感谢。 本次会议是我们易学界的又一次盛会，是我们易学界在新的时期新的社会条件下，弘扬我们祖国优秀文化的一次盛会，这次会议把我们来自世界各地的易学同仁们聚集在一起，进行传承发扬光大我们中华民族的智慧，解析博大精深的易学文化，让我们最古老的经典周易文化造福于社会，造福于人类，让我们的祖国在各个方面更强大，进行这一课题的探讨和研究，是一件值得庆贺和骄傲的大好事情，对于以后的全面共同推动易学的发展也是
非常有意义的事情。 席学易国际易学研究院是专业从事易学的学习培训和策划服务的专业机构，即培养培训一般的易学人才，同时也培养一批具有掌握易学术数高端技术的专业高端人才，十七年来，席学易国际易学研究院始终站在实用易学的前沿。在此，我代表本院向大家发出邀请，诚望诸位同仁将席学易国际易学研究院当成你们的交流学习园地，一如既往的支持我们，让我们携起手来，为易学的研究及易学事业在不远的将来出现更加美好的未来而共同努力。 各位领导，各位来宾，各位专家学者和各位易学同仁，本次会议的召开，必将使我们的易学事业向前更推进一步。我们满怀信心的认为，只要各位同仁齐心协力，并切实有效地发挥易学在现代社会中的作用，未来的易学研究事业，一定会更加辉煌。“乾道变化，各正性命，保合太和，乃利贞”;“君子黄中通理，正位居体，美在其中，而畅于四支，发于事业，美之至也。”我们相信，本次大会在国际易学联合会的主办下，在北京联合大学易学与经济发展研究中心的学术支持下，我们各位代表秉持“修辞立其诚”的学术精神，就易学的各种问题和研究“发己之所欲发，言己之所欲言”，会议必将取得丰硕成果，以学聚、问辩、宽居、仁行的精神，园满完成本届大会的使命。 祝各位领导、各位来宾、各位与会代表身体健康，精神愉快，自天佑之，吉无不利。 祝大会取得园满成功! 谢谢大家!
Thank you, prof. …. My name is ….. I’m from ….. I am very pleased to be here to join this forum. The topic of my presentation is properties of rapid construction materials for soil pavement of field airfield. As is shown in the picture, the main parts of my research are about soil pavement. My presentation will include these four parts: First, some background information about this research; second, the main work we have done; third, some conclusions we have got and the last: innovation and presentation of our published papers. Why I choose this item? I think it can be illustrated from the following four parts. First, the existing quantity of airfields is still not sufficient and the airfields have many shortcomings especially in war time. Second, the complementary facilities, such as highway runways are far less than airfields, however, have more weakness. Third, a certain amount of field airfield is quite necessary considering some emergencies such as rescue and disaster relief. Forth, the field airfield can fill the void of airfield and they can be combined to be airfield network. The meaning and aim of this research contains three parts. Fast, convenient and validity, fast means the field airfield must be constructed
1. Introduction Thank you very much. Mr. Jiao, for your kind introduction. Ladies and gentlemen, Good afternoon! My name is Lijia, came from Harbin Engineering University. I am honored to have been invited to speak at this conference. Before I start my speech, let me ask a question. Do you know what can affect the properties of foam concrete? Do you think how to reinforced the properties of foam concrete？Most of the investigations on foam concrete in the past have been con?ned（被限于）to neat cement paste, cement paste with partial replacement with admixtures and to cement–sand mixes. Today, my topic is about In?uence of ?ller type on the properties of foam concrete. I want to share our interesting research result on reinforced concrete frame with you. The content of this presentation is divided into 4 parts: In section 1, I will introduce what is the foam concrete. In section 2, I will talk about Parameters investigated and mix compositions.In section 3, I will give E?ect of water–solids ratio on design density. And finally, I will make a conclusion. 2. Body Section 1: the foam concrete Now, I will introduce the foam concrete. Pre-formed(成型的) foam concrete is manufactured（加工）by adding foam, prepared by aerating （充气）a foaming agent solution, to cement paste or cement mortar（灰
国际会议发言稿-英文(精选多篇)
国际会议发言稿英文(精选多篇) 第一篇：国际会议--英文 表示欢迎：good morning, ladies and gentlemen, i’m privileged to welcome you all to “the current status and future development of cotton machinery” conference. 自我介绍：let me introduce myself i am dr lifrom beijing, china, and i am going to be the chair for this morning’s session. 介绍议题： this conference will focus on the discussion of the various aspects of cotton machinery. it includes the application of cotton machinery and the current status.and we will also discuss the prospect of cotton machinery. 介绍报告人： now it gives me great pleasure to introduce today’sparticipants. they are :han dan, the director general of the united nations industrial development organization(联合国工业发展组织总干事) zhang hui, president of china power investment group company. shang fengjiao, professor of physics ,head of american nuclear energy association. now, we welcome the opening of han dan do for us（现在，我们欢迎aa 为我们做致开幕词） aa上台
A Keynote Speech at the 2nd Symposium on Environmental Pollution Respected President, Ladies and Gentlemen, It's my great honor to make the keynote speech at this conference. Nowadays, PM2.5 has become an environmental problem we can’t neglect any more.A recent research shows very high levels of PM2.5 in a broad swath stretching from the Saharan Desert in Northern Africa to Eastern Asia. PM2.5 refers to the atmosphere diameter less than or equal to the particles 2.5 microns. Although PM2.5 only group content of a few earth atmospheric composition points, but it has an important influence on air quality and visibility, especially in winter. Besides, PM2.5, which has a small particle size, contains a lot of toxic and harmful substances. As a result, longtime exposure to PM2.5 which can go directly to the alveoli of the lungs, is a major health hazard. In fact, the American Heart Association estimates that in the United States alone, PM2.5 air pollution spark some 60, 000 deaths a year. Recently, PM2.5 has influenced our life obviously. There are fog and hazy weather in big city from time to time, which even causes many protest haze activities in China. And many factors may contribute to it. Firstly, the large amount of pollutant emission, including coal-fired pollution, motor vehicle emission, industrial pollution and dust is the root