排序方式: 共有124条查询结果,搜索用时 15 毫秒
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朱宇芳 《泰州职业技术学院学报》2007,7(4):75-78
通过对2001-2005年降水常规监测数据的分析,探讨了泰州市区“十五”期间酸雨的时空分布特征、酸雨类型及产生原因。结果表明,泰州市区城区的酸雨污染状况较郊区严重。夏季降水的酸雨频率较高,冬春季其次,秋季最低。泰州市区酸雨属“硫酸型”酸雨。降水中Ca^2+对降水酸度的缓冲作用比较明显。降水阴阳离子平衡情况基本符合要求。酸性降水的形成与环境空气质量、机动车尾气、异地污染物的影响有关。 相似文献
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酸雨对植物的危害,已为人们所共识.通过人工模拟酸雨实验,可进一步探讨酸雨 的低PH值(PH值由7.0下降到2.0)会使植物的叶细胞透性增加(叶细胞透性增加的百分率( %):青菜最大可达到214.2%,莴苣可达到136.23%).同时也会使植物叶片中的叶绿素含量 下降(青菜的叶绿素含量从0.851mg/g·鲜重下降到0.247mg/g·鲜重,莴苣的叶绿素含量从 0.868mg/g·鲜重下降到0.185mg/g·鲜重).进而影响植物的生长发育,对植物造成伤害. 相似文献
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对近年来有关共轭亚油酸在猪营养上的研究与应用进展进行综述,介绍了共轭亚油酸在猪生产上的应用,重点论述了共轭亚油酸对猪的生产性能和胴体品质的影响,以及分析了上述作用的潜在机制. 相似文献
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柠檬酸改性竹屑吸附亚甲基蓝的动力学和热力学分析 总被引:1,自引:0,他引:1
为拓宽竹材剩余物的开发应用新途径。以竹屑为原料,柠檬酸为改性剂,制备了柠檬酸改性竹屑吸附剂,以亚甲基蓝(MB)为吸附对象,考察了pH、时间、吸附剂投量及吸附温度等对吸附剂吸附MB效果的影响,并对其吸附动力学和热力学进行了分析。结果表明:溶液pH增大,吸附剂对MB的吸附量增大,pH在5-9间变动,吸附剂对MB吸附量变化不大;染料初始浓度和吸附温度增加,吸附剂对MB吸附能力增强;在吸附120min,吸附达到平衡,吸附动力学过程符合二级动力学模型,吸附热力学过程符合Langmuir模型;在25℃、35℃、45℃时,吸附剂对MB的最大吸附量分别为106.38 mg/g、121.95 mg/g和125mg/g;竹屑吸附剂对MB的吸附过程是一个吸热的自发过程。 相似文献
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陈亚萍 《杨凌职业技术学院学报》2012,(4):7-9
通过对难于处理的低温低浊水进行投加助凝剂改性活化硅酸进行试验研究,提出了改性活化硅酸使用中的最佳粘度、最佳投加量等具体参数;同时在试验中了解到改性活化硅酸活化时间短,保存时间长,助凝效果好,投药量少等最优性能。 相似文献
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Harika Ozge Arslan Ceyhan Cigdemoglu Christine Moseley 《International Journal of Science Education》2013,35(11):1667-1686
This study describes the development and validation of a three-tier multiple-choice diagnostic test, the atmosphere-related environmental problems diagnostic test (AREPDiT), to reveal common misconceptions of global warming (GW), greenhouse effect (GE), ozone layer depletion (OLD), and acid rain (AR). The development of a two-tier diagnostic test procedure as described by Treagust constitutes the framework for this study. To differentiate a lack of knowledge from a misconception, a certainty response index is added as a third tier to each item. Based on propositional knowledge statements, related literature, and the identified misconceptions gathered initially from 157 pre-service teachers, the AREPDiT was constructed and administered to 256 pre-service teachers. The Cronbach alpha reliability coefficient of the pre-service teachers’ scores was estimated to be 0.74. Content and face validations were established by senior experts. A moderate positive correlation between the participants’ both-tiers scores and their certainty scores indicated evidence for construct validity. Therefore, the AREPDiT is a reliable and valid instrument not only to identify pre-service teachers’ misconceptions about GW, GE, OLD, and AR but also to differentiate these misconceptions from lack of knowledge. The results also reveal that a majority of the respondents demonstrated limited understandings about atmosphere-related environmental problems and held six common misconceptions. Future studies could test the AREPDiT as a tool for assessing the misconceptions held by pre-service teachers from different programs as well as in-service teachers and high school students. 相似文献
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采用一步法自行研制无机高分子混凝剂——聚硅硫酸铁(PSPFs),采用正交试验法,通过对印染模拟废水的混凝试验,确定合成PSPFS的最佳条件是:Fe/Si摩尔比为1:1;活性硅酸聚合时间为10m/n;反应时间为10min;反应温度为90℃。用PSPFS处理模拟印染废水和实际印染废水的实验表明,PSPFS对印染废水色度具有较好的去除效果,而且优于商品PAC。 相似文献
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LaKeisha McClary 《International Journal of Science Education》2013,35(10):1433-1454
The characterization of students’ reasoning strategies is of central importance in the development of instructional strategies that foster meaningful learning. In particular, the identification of shortcut reasoning procedures (heuristics) used by students to reduce cognitive load can help us devise strategies to facilitate the development of more analytical ways of thinking. The central goal of this qualitative study was thus to investigate heuristic reasoning as used by organic chemistry college students, focusing our attention on their ability to predict the relative acid strength of chemical compounds represented using explicit composition and structural features (i.e., structural formulas). Our results indicated that many study participants relied heavily on one or more of the following heuristics to make most of their decisions: reduction, representativeness, and lexicographic. Despite having visual access to reach structural information about the substances included in each ranking task, many students relied on isolated composition features to make their decisions. However, the specific characteristics of the tasks seemed to trigger heuristic reasoning in different ways. Although the use of heuristics allowed students to simplify some components of the ranking tasks and generate correct responses, it often led them astray. Very few study participants predicted the correct trends based on scientifically acceptable arguments. Our results suggest the need for instructional interventions that explicitly develop college chemistry students’ abilities to monitor their thinking and evaluate the effectiveness of analytical versus heuristic reasoning strategies in different contexts. 相似文献