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关键词： Radio frequency vacuum drying   banana   drying dynamic   drying uniformity  

摘要： Radio frequency (RF) drying can offer better drying rate and drying uniformity than traditional and microwave drying. Vacuum drying can be used to improve the problems accomplished with conventional drying methods. In this, the RF-vacuum drying equipment was developed and the drying dynamic and uniformity were studied. It can be found that RF-vacuum drying showed better drying rate that after 270 min drying, the samples with lower moisture content compared with RF dried ones. During RF-vacuum drying, it also can be observed that the top layer of samples had the lowest moisture content, followed by middle layer and bottom layer. The graphs showed that during RF-vacuum drying, the hot spots of single slice were located at the center of sample surface, whereas the cold spots were at the edges. For the whole samples, higher temperatures at the corners and edges of the top layer but lower ones in the central part of layer. The difference between uniformity index of surface and inner was a bit smaller than RF dried samples. RF-vacuum drying banana slices had better drying uniformity between different layers. These characteristics ensure RF-vacuum drying can be sued for massive samples drying.

关键词： 安全防护工作   燃烧理论   网络损伤   传播模型   数学分析   串扰   燃烧过程   燃烧模型  

摘要： 本文针对多域光网络串扰攻击传播带来的网络损伤问题,描述了大功率串扰攻击在多域光网络中的传播过程,同时与自然社会燃烧过程相类比,提出了一种基于燃烧理论的多域光网络串扰攻击DBS燃烧模型,对模型进行了描述与数学分析,得出大功率串扰攻击在多域光网络中的传播特点与规律,为光网络的安全防护工作提供理论参考。

关键词： 管道   腐蚀速率   计算方法   内检测   数学分析  

摘要： 腐蚀是威胁管道安全的重要因素,研判管道腐蚀风险具有重要意义。管道腐蚀速率是重要的管道外腐蚀控制准则和依据。确定准确管道腐蚀速率,可监控腐蚀缺陷发展趋势,制定科学的管道维修计划。管道腐蚀速率计算方法包括试验法、NACE经验公式、基于内检测和完整性评价法以及数学分析方法。阐述了上述方法的优缺点和适用范围,针对准确计算管道腐蚀速率提出应用建议。

关键词： 数学分析   课程思政   案例库  

摘要： 数学分析是数学类专业的最主要的核心基础课程之一。数学分析蕴含丰富的思政元素,为了提高数学分析课程思政的育人成效,需要将这些思政元素案例化,并将所设计的案例汇集成库,充分发挥数学分析课程思政元素的整体效益。遵循案例教学法的基本要求,结合课程思政的发展趋势,探索具有课程特色和时代特点的数学分析思政案例库建设原则、着力点以及实现途径。

关键词： 离心泵   圆柱形叶片   几何参数   设计   数学分析  

摘要： 为帮助离心泵设计人员准确认识与理解非等变角螺旋线这一新形型线的几何特性,消除广泛存在的对这一型线的性能与设计要求的误解,以数学方法为依据导出了这一曲线的极坐标方程和包角的限制条件,由此形成了在叶片设计中应用这一优势曲线的完整可行方法。叶片包角是离心叶轮圆柱形叶片的重要几何参数,有一种模糊认识,认为在使用等变角螺旋线选择包角值时,包角由设计人员自行确定,其值不受任何限制。在分析这一曲线的极坐标方程后,这一类曲线包角的选择仍然必须受到限制,这种约束是由曲线在进出口处的几何特征决定的,不同的叶片包角可取范围的上下限有不同的计算值,导出了这一限制区间由曲线特性决定的两个边界值的数学表达式,并按一般统计规律选择的最佳叶片包角只有进入这一区间时方可得到预期的结果。本文以试验对比结果证实了叶片设计新方法对改善叶片水力性能有积极作用。

关键词： 数学启发   金属晶体结构   学习兴趣   创新思维  

摘要： 该文探讨把数学思维与抽象专业知识结合起来,把数学启发渗透且运用到专业课材料科学与工程基础的晶体结构及间隙教学过程。该教学方法帮助学生借助已有的数学基础知识理解抽象的晶体结构。强化学生的逻辑思维能力,激发学生学习兴趣,并且有助于培养学生跨学科知识的综合运用技巧及创新思维能力。运用数学启发辅助材料科学与工程基础相关知识的教学,强调对晶体结构基本概念内涵的挖掘和分析,为提高课堂教学效果和学生综合素质提供有效策略。

关键词： 中考   考细化   常规教学  

摘要： 翻开今年的数学试卷不少教师感叹:“变化太大了”。教师有点惊讶,学生有点触手不及。静下心来,统观全卷,究其本质可以概括为“稳中突变”,稳在分值占比,变在试题结构。

关键词： 数学分析   课程思政   思政元素   教学策略  

摘要： 结合广西师范大学数学分析教学状况,着力解决数学分析教与学过程中出现的两大矛盾与四大问题,深入挖掘每个数学符号中及各教学环节中所蕴含的思政元素,认真做好每堂课程的教学设计与实施,提高学生的理论学习能力与创新和实践能力。

关键词： Epidemic   COVID-19   Compartmental models   Partial differential equations  

摘要： The outbreak of COVID-19 in 2020 has led to a surge in interest in the research of the mathematical modeling of epidemics. Many of the introduced models are so-calledcompartmental models, in which the total quantities characterizing a certain system may be decomposed into two (or more) species that are distributed into two (or more) homogeneous units called compartments. We propose herein a formulation of compartmental models based on partial differential equations (PDEs) based on concepts familiar to continuum mechanics, interpreting such models in terms of fundamental equations of balance and compatibility, joined by a constitutive relation. We believe that such an interpretation may be useful to aid understanding and interdisciplinary collaboration. We then proceed to focus on a compartmental PDE model of COVID-19 within the newly-introduced framework, beginning with a detailed derivation and explanation. We then analyze the model mathematically, presenting several results concerning its stability and sensitivity to different parameters. We conclude with a series of numerical simulations to support our findings.

关键词： Porous media   Pore network   Extraction   Network clustering   Curved throat  

摘要： Static and dynamic properties of porous media are highly dependent on its internal geometry. CT scan images are generally used to characterize porous media geometry. Direct simulation of fluid flow on CT scan images is possible but considerably time-consuming. In this study, a new method was developed for extracting a simplified representation known as "pore network model" by utilizing a rigorous algebraic-analytical method. By using a moving frame in the 3D matrix of the CT scan image and stepwise identifying-removing of image components, running time for a 400(3) voxels sample in a typical computer system decreased to less than 350 s. The identification of throats was based on a new clustering method maximizing connectivity degree for an extracted model. For a sandstone sample, the developed model was consistent with the "maximum ball" model. The values obtained for average coordination number from the model proposed in this work and one proposed by Dong and Blunt using the maximum ball, were 4.13 and 3.98, respectively. Moreover, comparing the results of the proposed model with the ones obtained by Dong and Blunt using the maximum ball, average pore and average throat radii [PR, TR] were [26.43, 12.23] and [15.36, 7.01], respectively. The numbers of pores and throats [NP, NT] for the proposed model were [4921, 9494] and [6004, 12067] were reported by Dong and Blunt for the maximum ball model. In addition, an identification algorithm of curved throat was developed and validated with the help of a simple synthetic sample.