The material theory of induction and the epistemology of thought experiments

John D. Norton is responsible for a number of influential views in contemporary philosophy of science. This paper will discuss two of them. The material theory of induction claims that inductive arguments are ultimately justified by their material features, not their formal features. Thus, while a deductive argument can be valid irrespective of the content of the propositions that make up the argument, an inductive argument about, say, apples, will be justified (or not) depending on facts about apples. The argument view of thought experiments claims that thought experiments are arguments, and that they function epistemically however arguments do. These two views have generated a great deal of discussion, although there hasn't been much written about their combination. I argue that despite some interesting harmonies, there is a serious tension between them. I consider several options for easing this tension, before suggesting a set of changes to the argument view that I take to be consistent with Norton's fundamental philosophical commitments, and which retain what seems intuitively correct about the argument view. These changes require that we move away from a unitary epistemology of thought experiments and towards a more pluralist position.     

The role of orientation experiments in discovering mechanisms

Many types of experiments have been recognized in the literature. One important type we discuss in this article is the orientation experiment. While orientation experiments are like other types of experiments in that they are tests for causal relevance, they also have other qualities. One important (but not the only) goal of these experiments is to offer a rough, qualitative characterization of the mechanism responsible for a capacity of interest, effectively constraining future research. This makes them particularly useful during the early stages of investigation, when an explanandum-phenomenon has just been identified and several (often competing) hypotheses as to the qualitative character of the mechanism responsible for it are proposed. We illustrate our claims, and explicate a number of additional aims that orientation experiments can sometimes serve, by considering three case studies from different era's, namely the discovery of the mechanisms responsible for i) the capacity of eels to produce numbing sensations (17th and 18th century), ii) puerperal fever in Semmelweis' Vienna Maternity Hospital (19th century), and iii) the capacity of pigeons to home (20th century).     

波流环境下多孔射流运动和稀释特性试验

采用PIV和PLIF技术对波流环境下多孔垂向射流近区的速度场和浓度场进行测量,对比分析不同波浪条件下射流运动轨迹、速度场、浓度场及涡量场特性,重点探讨波流和纯流环境下射流运动特性的差异以及波浪作用对多孔射流发展的影响。结果表明:波流流场中射流时均轨迹发生扭曲,产生"污染物云团"现象,与纯流环境下射流差异明显;波浪对波流环境下的多孔射流运动影响显著,具体表现在波浪强度的增大能够增加射流与环境水体的接触面积、加快射流垂向动量衰减、增强前方射流对后方射流的遮掩作用、降低多孔射流汇合点高度等方面。当前组次下,波浪的存在使得各断面污染物浓度峰值减小,因此对波流环境下多孔射流的稀释有积极的作用。     

大学物理设计型实验的开发与设计

大学物理实验课程是高校大学生的一门必修基础实验课程,传统的物理实验教学,往往不重视对学生创新能力和动手能力的培养。本文先是对设计型实验的选题原则、教学要求和教学方式进行了阐述,然后列举实例进行分析,最后对设计型物理实验提出了几点建议。设计型物理实验对于提高学生的创新能力具有很大帮助。     

建筑多孔饰面砖蒸发降温的风洞实验研究

采用热湿气候风洞复现广州地区夏季典型气象日环境,研究两个相同试件在补水和不补水状态下的热量传递过程.研究结果表明:试件补水后蒸发降温效果显著,与不补水试件相比,补水试件的外表面最高温度和内表面最大热流分别降低10.9℃和14.8 W/m2,同时,补水试件的平均热阻比不补水试件的平均热阻增大约1倍,隔热效果显著增加.此外,研究过程中引入土壤学的Penman-Menteith蒸发量计算模型,结合实测数据对该模型中的参数进行修正,将总蒸发量分解为热力蒸发量和动力蒸发量,分析三者的变化规律,采用逐时蒸发量数据计算试件外表面的热量平衡方程.计算结果表明:蒸发过程可以消耗约64.5%的入射短波辐射热量,在夏季,蒸发过程可以显著减少建筑外表面的太阳辐射的热量,降低表面温度,减少进入房间的热量,从而节省空调能耗.     

有机化学实验中自我安全意识的教育

有机化学是一门以实验为基础的学科,学习有机化学必须认真做好有机化学实验。在实验室对学生进行动手能力,研究设计能力,思维表达能力等的培养固然是主要目的,但是基于有机化学实验自身的特点,对学生进行安全知识教育,培养学生的自我安全意识也是至关重要的。从大学有机化学实验安全出发,从几个方面对学生安全意识的培养提出了自己的一些看法及解决途径。     

LTSpice在《医学电子学》实验教学中的应用

针对医学院校《医学电子学》实验教学存在的困境,探讨了将LTspice仿真软件引入实验教学环节。结合一个具体实例给出LTspice在医学电子学实验中的应用方法。实践表明,LTspice提供了一个便捷的虚拟实验平台,弥补了传统实验教学方法的不足,是提高实验教学质量,培养学生动手和创新能力的有效手段。     

《通信原理》课程的课堂与实验教学改革简

《通信原理》是通信类、电子类专业非常重要的专业基础课.该课程具有理论性强、抽象概念多、教学难度大等特点.为了提高学生的学习兴趣、激发学生的潜在能力,针对教学中存在的问题,从改进教学课件、采用软硬件结合的实验等方面探索如何提高教学效果的一些思路.实践证明,通过以上教学方法的改革,教学质量得到了提高,教学实践取得了良好的效果.     

潮流能自由变偏角水轮机自启动特性分析

垂直轴水轮机的启动特性是潮流能发电技术的关键问题之一.根据模型试验技术,测量潮流能自由变偏角水轮机转速和转矩在启动过程中的变化规律.基于黏性CFD数值模拟方法,监测该水轮机水动力转矩、负载转矩、叶片偏角、叶片切向力等参数在启动过程中的变化规律.通过分析上述运动参数与动力参数之间的相互作用探讨该水轮机启动特性.研究结果表明:自由变偏角水轮机由于能够迅速调整叶片偏角,因此可以改善水轮机启动过程的总体水动力性能;转矩-速比特性决定该水轮机启动过程经历起步、加速和渐进稳定3个阶段;当发生超载或者受到波浪影响时,水轮机将从渐进稳定段进入不能稳定运行的加速段,继而发生快速停机现象.     

北京大学加速器质谱循环气体剥离系统

基于EN型串列静电加速器的北京大学加速器质谱系统(PKUAMS)将主要开展高灵敏度10Be测量,为此需要对该加速器的剥离系统进行改造.介绍了PKUAMS循环气体剥离器的研制,包括真空系统物理设计、模拟实验以及控制系统设计等.