微流控纸芯片的加工及其分析应用的实验设计*

设计了一个使用喷墨打印法加工微流控纸芯片的实验,在经烷基烯酮二聚体(AKD)的正己烷溶液浸泡过的滤纸上,以三乙醇胺溶液为打印墨水,用喷墨打印机打印出设计好的芯片图案。滤纸加热后,打印区域呈现亲水性,非打印区域为疏水性,从而制备出纸芯片,用该纸芯片通过数字比色法实现了亚硝酸根离子的定量测定。该实验不使用昂贵仪器设备,易普及。通过实验,促使学生了解微流控芯片这一前沿科学技术,锻炼学生细致、灵巧的动手能力,激发学生科技创新活力。     

求解矩阵方程AXB+CXD=F参数迭代法的最优参数分析

本文针对求矩阵方程AXB+CXD=F唯一解的参数迭代法，分析当矩阵A，B，C，D均是Hermite正（负）定矩阵时，迭代矩阵的特征值表达式，给出了最优参数的确定方法，并提出了相应的加速算法.     

A MODAL TESTING METHOD FOR CANTILEVER BEAM1)

基于欧拉-伯努利梁理论得到悬臂梁自由振动的振型函数。通过数值计算得出实验用的悬臂梁前五阶振型的节点位置及其与梁长的比值。考虑传感器对悬臂梁固有频率的影响,建立梁-传感器模型进行仿真分析并得出悬臂梁前五阶固有频率。基于节点位置和测点位置,在实验中选择激励点。将具体实验的结果与梁-传感器仿真模型结果进行对比,通过前五阶固有频率的误差分析,发现仿真分析结果与实验结果误差最高为 1.3%。研究完整地叙述了悬臂梁的模态测试流程,可为工程技术人员的模态测试起一定的指导作用。     

甲烷-二氧化碳重整制合成气与现代分析技术应用于探究性化工专业实验的设计与探索

以甲烷-二氧化碳重整制合成气为实例，设计探究性实验，将合成气的制备和现代分析技术应用于化工专业实验的教学实践中以提高学生的创新和实践能力。实验包括催化剂的制备，催化剂的性能评价和催化剂的表征等3大部分。采用工业最常用的浸渍法制备含有不同助剂的Ni/X/γ-Al2O3（X为Co，Fe，MgO，CeO2）催化剂，以甲烷-二氧化碳重整反应评价其催化性能，并采用XRD、H2-TPR、BET和TG对催化剂的微观结构进行表征。结合催化剂的性能评价结果和表征结果，探讨不同助剂对镍基催化剂性能的改善效果及机制。通过开设该实验，可以让学生了解化工学科的前沿知识以及现代分析技术的基本原理和用途，掌握专业的实验操作、数据处理和谱图绘制方法，提高学生的专业素养和综合能力。     

An adaptive multilevel wavelet framework for scale‐selective WENO reconstruction schemes

We put forth a dynamic computing framework for scale‐selective adaptation of weighted essential nonoscillatory (WENO) schemes for the simulation of hyperbolic conservation laws exhibiting strong discontinuities. A multilevel wavelet‐based multiresolution procedure, embedded in a conservative finite volume formulation, is used for a twofold purpose. (i) a dynamic grid adaptation of the solution field for redistributing grid points optimally (in some sense) according to the underlying flow structures, and (ii) a dynamic minimization of the in built artificial dissipation of WENO schemes. Taking advantage of the structure detection properties of this multiresolution algorithm, the nonlinear weights of the conventional WENO implementation are selectively modified to ensure lower dissipation in smoother areas. This modification is implemented through a linear transition from the fifth‐order upwind stencil at the coarsest regions of the adaptive grid to a fully nonlinear fifth‐order WENO scheme at areas of high irregularity. Therefore, our computing algorithm consists of a dynamic grid adaptation strategy, a scale‐selective state reconstruction, a conservative flux calculation, and a total variation diminishing Runge‐Kutta scheme for time advancement. Results are presented for canonical examples drawn from the inviscid Burgers, shallow water, Euler, and magnetohydrodynamic equations. Our findings represent a novel direction for providing a scale‐selective dissipation process without a compromise on shock capturing behavior for conservation laws, which would be a strong contender for dynamic implicit large eddy simulation approaches.     

Damage characteristics and surface description of near-wall materials subjected to ultrasonic cavitation

For the analysis of ultrasonic cavitation erosion on the surface of materials, the ultrasonic cavitation erosion experiments for AlCu4Mg1 and Ti6Al4V were carried out, and the changes of surface topography, surface roughness, and Vickers hardness were explored. Cavitation pits gradually expand and deepen with the increase of experiment time, and Ti6Al4V is more difficult to erode by cavitation than AlCu4Mg1. After experiments, the cavitation damage characteristics such as the single pit, the rainbow ring area, the fisheye pit, and some small pits were observed, which can be considered to be induced by a single micro-jet impact, ablation effect caused by the high temperature, micro-jet impingement with a sharp angle, and multibeam micro-jets coupling impact or negative pressure in the local area produced by micro-jet impact, respectively. The surface roughness and Vickers hardness of the material increase slowly after rapid growth at different points in time as the experiment time increases. With the increase of the ultrasonic amplitude, both of them first increase and then decrease after the ultrasonic amplitude is greater than 10.8 μm. The increases in surface roughness and Vickers hardness tend to decrease as the viscosity coefficient increases. Ultrasonic cavitation can cause submicron surface roughness and increase surface hardness by 20.36%, so it can be used as a surface treatment method.     

D-T中子活化实验中89Rb半衰期的实验测量研究

加速器中子活化实验是核专业本科实验教学中的重要实验之一.本文在利用14 MeV快中子辐照238U诱发裂变截面实验过程中引导学生挖掘实验数据,测量了裂变核素(89Rb)的重要核参数—半衰期.本工作运用低本底HPGe-γ谱仪测定裂变产物的一系列γ射线能谱,解谱得到89Rb的特征γ峰计数,从而确定89Rb的半衰期.数据分析中应用89Rb核素两条γ射线分别独立得到89 Rb的半衰期为15.30±0.09 min和15.25±0.07 min.测量结果在与文献数据符合较好的基础上,提高了测量精度.     

熵的一种通俗教法

熵如力、能量和动量一样是物理学中一个重要概念,若能用一种通俗易懂的方法设计熵的教学,对文科物理的教学有重要意义.为此本文提出了一种通俗的熵的教法,这一教法不需要学生学习热力学第二定律也可以建立熵的概念.具体教学设计如下:通过日常生活例子引入熵的概念(也就是玻尔兹曼熵),设计两个例子让学生会计算熵,通过具体问题的讨论让学生充分理解熵的意义,通过一个实例由玻尔兹曼熵引入克劳修斯熵公式,设计一个演示实验强化教学效果,将熵与环境保护联系起来融入人文情怀,最后还强调了熵计算的不同层次.教学设计完全采用基于问题学习(PBL)的教学模式.