Concreteness fading in learning secondary school physics concepts     

《Learning and Instruction》2022

Concreteness fading has been proposed as a general instructional approach to support learning of abstract mathematics and science concepts. Accordingly, organizing external knowledge representations in a three-step concrete-to-idealized sequence should be more beneficial than the reverse, concreteness introduction, sequence. So far, evidence for the benefits of concreteness fading come mainly from studies investigating learning of basic mathematics concepts. Studies on learning natural science concepts are scarce and have not implemented the full three-step-sequence. In an experimental classroom study (N = 70), we compared concreteness fading and concreteness introduction in high school science education about electromagnetic induction using a detailed assessment. Furthermore, we explored whether these sequences differentially affect the use of the different representations during instruction. Both sequences were equally effective and there were no differences in using the representations. We discuss why our results question the proposed advantages of concreteness fading and highlight conceptual differences and learning goals across domains.  相似文献   

多传感器融合定位技术研究进展分析     

卢光明 《科技广场》2014,(10)

随着GNSS及计算机技术的不断发展,人们对室内外位置服务的需求不断增加。学校、医院、展厅、写字楼等都需要使用准确的室内外定位信息,特别是在应对紧急情况时,室内定位信息显得尤为重要。本文分析了多传感器融合的室内外定位技术研究进展,提出了基于数据融合的多传感器融合定位平台,以GPS技术为主导,结合WIFI、航位推算等定位技术的方法,通过一定的数据融合算法,增强室内外定位的完备性,为进一步实现室内外无缝定位、智慧地球等提供了参考。  相似文献   

Natural surface design for sliding mode control with multiple discontinuous inputs     

Pedro Acosta 《Journal of The Franklin Institute》2014

It is well known that sliding mode control is based on the definition of an invariant manifold, where the system dynamics are forced to in a finite time. Such a manifold is somewhat arbitrarily defined, as long as the system dynamics are stable on it. Computational and control effort may vary depending on selected manifold. Obviously, if a system has naturally acceptable stable dynamics around a desired equilibrium point, no control is needed unless uncertainties or disturbances are present. It would be desirable that if such a system had uncertainties or disturbances, the control effort be designed only to overcome the effect of such factors. For a system with first order dynamics and affine control input, designing a sliding mode control overcoming only such uncertainties or disturbances is a trivial task. When a higher order dynamics system is involved, unit control may be used, where the input control signals are not discontinuous, but when only discontinuous control inputs are available, a design approach is not readily available. In this paper, taking advantage of the natural stable dynamics of a system, a sliding mode control approach is introduced for designing multiple discontinuous control inputs, where the control effort overcomes only uncertainties, disturbances or unstable dynamics. Two illustrative examples are given in order to show the feasibility of the method.  相似文献   

基于多重螺旋协同创新理论的DEA评价模型——以皖江城市带为例     

鲁强  孔庆洋 《科技管理研究》2014,(16)

根据三螺旋模型的基本框架、产学研理论和系统动力学构建I-U-G-R-U多螺旋协同创新模型,基于该模型内嵌两阶段链DEA模型和多重螺旋协同创新评价指标体系,并以皖江城市带为例进行科技创新能力评价的实证分析。实证结果表明:I-U-G-R-U多螺旋协同创新模型的测度结果较好;皖江城市带存在显著的科技梯度现象,科技创新没能实现承续性以及存在各要素投入存在不合理等现象。从区域内科技创新来看,皖江城市带内部科技创新效率差异大;从分阶段科技创新来看,皖江城市带将科技创新成果转化为经济产出的效率明显高于将科技创新所需资源利用并转化为科技创新成果的效率。  相似文献   

Exploring the relations between epistemic beliefs,emotions, and learning from texts     

《Contemporary educational psychology》2017

Conflicting claims about important socio-scientific debates are proliferating in contemporary society. It is therefore important to understand the individual characteristics that predict learning from conflicting claims. We explored individuals’ beliefs about the nature of knowledge and knowing (i.e., epistemic beliefs) and their emotions as potentially interrelated sets of learner characteristics that predict learning in such contexts. Undergraduate university students (N = 282) self-reported their topic-specific epistemic beliefs and were given three conflicting texts about climate change to read. Immediately after each of the three texts, participants self-reported the emotions they experienced. Following reading and self-report, participants wrote summaries of the conflicting texts. Text-mining and human coding were applied to summaries to construct two indices of learning from conflicting texts that reflected which source’s information is privileged in memory. Results from structural equation modeling revealed that epistemic beliefs were consistent in their predictions of emotions, which in turn variously predicted different learning outcomes. In particular, a belief that knowledge is justified by inquiry predicted surprise and curiosity, which at times facilitated learning. In contrast, confusion, predicted by passive reliance on external sources, related to impaired memory of conflicting content. Theoretical and methodological implications are discussed for research on the relations between epistemic beliefs, emotions, and learning about controversial topics.  相似文献   

传统农业区稻田多个物种共存对病虫草害的生态控制效应——以贵州省从江县为例     

张丹  成升魁  杨海龙  何露  焦雯珺  刘珊  闵庆文 《资源科学》2011,33(6):1032-1037

本文运用半试验与调查相结合的方法,以贵州省从江县传统农业地区的糯稻和杂交稻为例,研究了传统品种和现代品种在水稻单作(R)、稻-鱼(R-F)和稻-鱼-鸭(R-F-D)3种不同稻作方式下,稻田多个物种共存对稻田生态系统主要病虫草害及蜘蛛的影响。结果表明,就水稻品种而言,糯稻在3种稻作方式下的抑制杂草能力均优于杂交稻,糯稻田与杂交稻田的稻飞虱虫量、稻纵卷叶螟虫量以及蜘蛛量差异不显著,杂交稻在3种稻作方式下的抗稻瘟病能力显著高于糯稻。就稻作方式而言,R-F-D显著降低了田间杂草的发生密度,对稻田杂草鸭舌草(Monochoria vaginalis)、节节菜(Rotala indica)等的抑制效果达到100%,总体抑制效果显著优于其它的稻作方式;R-F-D系统的稻飞虱、稻纵卷叶螟虫量较水稻单作明显减少;R-F系统的蜘蛛数量最高;R-F-D系统的抗稻瘟病性最好。  相似文献   

在废水处理过程中基于过程分析技术的多重响应优化     

Abbas AL-REFAIE 《浙江大学学报(A卷英文版)》2014,15(5):374-384

研究目的：基于过程分析技术框架,优化家禽业的废水处理工艺的性能。研究方法：生产商主要关注浊度和污泥容积指数（SVI）这两个响应。首先为每个响应建立移动平均（MA）和移动范围（MR）控制图,并在实验工作中重复两次3。全因子设计。基于模糊目标规划建立加权相加模型,并用于确定最佳的因子设置组合。最后,在最佳的因子设置组合条件下,对实验结果进行跟踪确认。重要结论：在絮凝剂为18mg／L、凝结剂为40．0mg／L和pH=4．0的最佳工艺条件下,得到的浊度和污泥体积指数的最佳值分别为6．184NTU和73．21ml／g。在此条件下得到的浊度和污泥沉降指数能够满足设计要求,它们的过程变异性分别显著下降了41．22％和77．75％,且多重能力指数从1．95显著增加至10．6。这表明此过程可行性很高。总之,加权相加模型是一种用于优化多个响应流程性能的有效技术,并且可以考虑工程师的首选设置流程。  相似文献   

基于多元价值观的大学生心理危机干预机制研究     

孙国俊 《河南科技学院学报》2014,(3):84-87

社会观念的多元化,使得价值观多元化发展并对当代大学生的心理发展产生很大的影响,探究在多元价值观视角下的大学生心理干预机制,可以更好地发挥价值观的引领作用,引导大学生在积极学习和正确吸收人类优秀文明成果的基础上发展形成良好的价值观,树立坚定的社会主义信念,培养学生新思想、新观念,培养学生在正确的指导思想引领下形成以社会主义核心价值体系为主的价值观,并发挥好导向作用,防止大学生在多元价值观中迷失方向,没有了辨识力。文章在对大学生价值观导向问题进行探究的基础上,阐明了多元价值观的作用和意义,以社会主义核心价值为主体正面引领大学生价值观发展,并分析了如何建立多元价值观视角的大学生心理干预机制,构建心理防护的网络,从而引导大学生在当前复杂的社会环境下坚定中国特色社会主义信念。  相似文献   

基于多重调谐质量阻尼器的苏通大桥抖振位移最优控制的数值模拟     

Hao WANG Tian-you TAO Huai-yu CHENG Ai-qun LI 《浙江大学学报(A卷英文版)》2014,(10):798-812

研究目的：为超大跨度斜拉桥抗风设计与抖振控制提供参考。研究方法：基于ANSYS建立了苏通大桥三维有限元模型,并在MATLAB平台模拟了苏通大桥三维脉动风场。考虑主梁断面气动自激力,进行了苏通大桥抖振时域分析。根据苏通大桥动力特性和抖振时域分析结果,重点分析了多重调谐质量阻尼器（MTMD）用于抖振控制的参数敏感性。考虑MTMD的控制效果、建造费用、施工难度及鲁棒性等因素建立了关于MTMD设计参数的目标函数,并基于一阶优化算法进行目标函数最优解的非线性搜索,据此获得了MTMD在约束条件下的最优设计参数。重要结论：1.苏通大桥侧向抖振位移主要由第一阶侧弯振型控制,竖向抖振位移主要由第一阶竖弯振型控制;2.MTMD的控制效果对设计参数的变化十分敏感,其中质量比和频带宽敏感性更强;3.MTMD的最优设计参数可以通过一阶优化算法获得,并可通过零阶优化算法对优化结果进行验证;4.采用优化后的MTMD设计参数,苏通大桥的抖振响应可以得到明显抑制,且侧向抖振控制效果更加明显。  相似文献   

试论多元价值观对在校大学生阅读价值的影响     

谢凝 《河南科技学院学报》2014,(5):86-89

近年来,中国社会的思想文化和价值观念都发生了深刻变化,境外的个人利己主义、极端个人主义、自我中心主义等逐渐进入人们的意识形态之中,在社会上形成了一种多元价值观并存的格局。在校大学生阅读价值的多元化,不仅反映了他们多层次的人生价值诉求,同时也在一定程度上体现了其价值观的多元化。只有对我国在校大学生多层次的阅读需求进行正确引导,才可能在多元价值观的冲突与调适中真正实现他们的阅读价值。  相似文献