Polychlorinated dibenzo-p-dioxins and dibenzofurans in flue gas emissions from municipal solid waste incinerators in China   总被引：2，自引：0，他引：2  

Tong CHEN  Yue-ling GU  Jian-hua YAN  Xiao-dong LI  Sheng-yong LU  Hui-fen DAI  Ke-fa CEN 《浙江大学学报(A卷英文版)》2008,9(9)

Polychlorinated dibenzo-p-dioxins and furalls(PCDD/Fs)emissions in flue gas from two types of municipal solid waste incinerators(MSWIs)most commonly used in China were investigated in this study.The selected incinerators include two grate-type MSWIs:MSWl-A(350 t/d)and MSWI-B(150 t/d),and two fluidized bed MSWIs:MSWI-C(400 t/d) and MSWI-D (400 t/d),which are all equipped with semi-dry lime scrubber and bag filter except MSWI-D equipped with cyclone and wet scrubber(WS)as air pollutant conffol device(APCD).Results indicated that the emission concentration and the international toxic equivalents(I-TEQs)of the PCDD/Fs from the stacks were in the range of 1.210～10.273 ng/Nm3 and 0.019～0.201 ngI-TEQ/Nm3,respectively.They were greatly lower than the emission regulation standard of PCDD/FS in China(1.0 ng I-TEQ/Nm3).However,only the PCDD/Fs emission Ievel from MSWI-C Was below 0.1 ng I-TEQ/Nm3.Although the homologue profiles were distinct,the contributions of the 2,3,7,8-subsituted congenem to the total I-TEQ were similar among all the investigated MSWIs.Two major 2,3,7,8-substituted congeners,2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD,account for 47% and 9%(average values)of the total I-TEQ values,respectively.The correlation between PCDD/Fs levels and composition of flue gas Was also discussed.  相似文献   

Understanding the dynamics of MOOC discussion forums with simulation investigation for empirical network analysis (SIENA)     

Jingjing Zhang  Maxim Skryabin  Xiongwei Song 《Distance Education》2016,37(3):270-286

This study attempts to make inferences about the mechanisms that drive network change over time. It adopts simulation investigation for empirical network analysis to examine the patterns and evolution of relationships formed in the context of a massive open online course (MOOC) discussion forum. Four network effects—homophily, reciprocity, transitivity, and preferential attachment—were tested to explain the dynamic mechanisms of interaction in the MOOC forum. Understanding the network dynamics of relationships will allow us to explore how to develop a robust peer-supported learning environment and in turn improve the online learning experience in MOOCs.  相似文献   

The Talking Drawings Strategy: Using Primary Children’s Illustrations and Oral Language to Improve Comprehension of Expository Text     

Kelli R. Paquette  Susan E. Fello  Mary Renck Jalongo 《Early Childhood Education Journal》2007,35(1):65-73

Listening and reading comprehension can be assessed by analyzing children’s visual, verbal, and written representations of their understandings. “Talking Drawings” (McConnell, S. (1993). Talking drawings: A strategy for assisting learners. Journal of Reading, 36(4), 260–269 is one strategy that enables children to combine their prior knowledge with the new information derived from an expository text and “translate” those newly-acquired understandings into other symbol systems, including an oral discussion with a partner, a more detailed drawing, and written labels for the drawing. The Talking Drawings strategy begins by inviting children to create pre-learning drawings. These initial drawings are a way of taking inventory of a child’s current content knowledge about a particular topic. After pre-learning drawings are created and shared, children listen to or read an expository text (e.g., information book, passage from a textbook) on the same topic as their drawing. Pairs of students discuss the information and either modify their pre-learning drawings to be more detailed or create completely new drawings that reflect the recently-acquired information. Students are encouraged to label their drawings with words in a diagram or schematic fashion. By evaluating the “before” and “after” artwork, educators can identify advances in students’ reading and listening comprehension of the terminology, facts, and principles on a particular topic.  相似文献   

为何进步、为何退步：重点大学城乡学生学业表现变化过程     

牛新春  杨菲  杨滢 《复旦教育论坛》2020,18(3):58-66

对于学业表现变化过程的考察指向本科教育质量这个目前被广泛关注的议题。以大学生投入理论为指导，使用教育部直属X大学的学生学业记录和跟踪调研数据，考察学生学业表现进步和退步的过程。对学生大一、大二、大三学业表现进行了聚类分析，从而将学生分为五类——持续优秀、中上等进步、中上等退步、中下等进步、持续差等。学业进步的学生大二到大三持续投入，并没有避免挑战性课程；学业退步的学生从大二开始松懈，相对回避挑战性课程，深度学习相对不足。学生大学期间对作业的态度是影响学生学业表现变化的核心因素。农村学生虽然更可能持续差等，却也更可能取得学业进步；这些学生虽然面临家庭背景劣势和学习方法不当的压力，却依然实现了学业进步。研究结果不仅对重点大学进行过程性学业支持提供了实证依据，也对基于学业表现变化进行过程性评价，并以此激励弱势学生发展有着重要启示。  相似文献   

毛泽东的生死观     

程林辉 《江西师范大学学报(哲学社会科学版)》2006,39(3):15-19

青年毛泽东的生死现具有自然主义和浪漫主义相结合的特色,晚年则转变为理性主义。人的生命虽然是有限的,但可以通过体育锻炼延长生命的长度和“只争朝夕”的精神扩大生命的内涵。生命的意义不在于寿命的长短,而在于是否活得有意义和死得其所。只有那些为人民利益而死、捍卫自己人格尊严和民族气节的人才是高尚的、伟大的。  相似文献   

What Can the Teacher Learn in the Classroom?     

Claire Margolinas  Lalina Coulange  Annie Bessot 《Educational Studies in Mathematics》2005,59(1-3):205-234

Our research is concerned with teacher’s knowledge, and especially with teacher’s processes of learning, in the classroom, from observing and interacting with students’ work. In the first part of the paper, we outline the theoretical framework of our study and distinguish it from some other perspectives. We argue for the importance of distinguishing a kind of teacher’s knowledge, which we call didactic knowledge. In this paper, we concentrate on a subcategory of this knowledge, namely observational didactic knowledge, which grows from teacher’s observation and reflection upon students’ mathematical activity in the classroom. In modeling the processes of evolution of this particular knowledge in teachers, we are inspired, among others, by some general aspects of the theory of didactic situations. In the second part of the paper, the model is applied in two case studies of teachers conducting ordinary lessons. In conclusion, we will discuss what seems to be taken into account by teachers as they observe students’ activity, and how in-service teacher training can play a role in modifying their knowledge about students’ ways of dealing with mathematical problems.  相似文献   

Experimental Investigation and Modelling for the Optimisation of Conduction Cooled HTS Hybrid Current Leads for SMES     

程德威  王惠龄  Spiller D M  Huang Y B  饶荣水  唐跃进 《天津大学学报(英文版)》2003,9(1)

Ａｔｐｒｅｓｅｎｔ,Ｂｉ(2 2 2 3) /Ａｇｍｕｌｔｉｆｉｌａｍｅｎｔａｒｙｓｕｐｅｒ ｃｏｎｄｕｃｔｉｎｇｔａｐｅｓａｒｅｃｏｎｓｉｄｅｒｅｄｔｈｅｍｏｓｔｓｕｉｔａｂｌｅｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｕｐｅｒｃｏｎｄｕｃｔｏｒｓ (ＨＴＳ)ｔｏｂｅａｐｐｌｉｅｄｔｏｓｕ ｐｅｒｃｏｎｄｕｃｔｉｎｇｍａｇｎｅｔｉｃｅｎｅｒｇｙｓｔｏｒａｇｅ(ＳＭＥＳ) ,ｓｕｐｅｒ ｃｏｎｄｕｃｔｉｎｇｍａｇｎｅｔｓ,ｓｕｐｅｒｃｏｎｄｕｃｔｉｎｇｆａｕｌｔｃｕｒｒｅｎｔｌｉｍ ｉｔｅｒｓａｎｄｃｕｒｒｅｎｔｌｅａｄｓ,ｅｔ…  相似文献   

HIT—MU（2）的结构和复杂度     

徐小萍  丁德成 《襄樊学院学报》2004,25(5):3-6

SAT问题(可满足性问题)是计算机科学的核心问题,研究SAT问题的方法很多,利用极小不可满足公式的性质来研究SAT问题是近几年兴起的一个热点研究方向. 本文主要利用1(,)*-消解和分裂方法研究了差为2的碰撞极小不可满足公式集()2(MUHIT-)的结构和复杂度.此前,只有G.Davydov, I.Davydova 和H.Kleine Büning对)1(MU和)2(MU的结构和复杂度得出了较好的结果.  相似文献   

莘数理论(V)     

孙桂秋 《湖南城市学院学报》2002,(6)

首先给出了函数的本式值和标式值的概念 .在限制使用极限的前提下 ,独立地推出了微积分理论 .并给出了在相对论方面的简单应用 ,求出了光子的静止质量 .  相似文献   

How to count —An exposition of Polya’s theory of enumeration     

Shriya Anand 《Resonance》2002,7(9):19-35

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