四条腿桌子能在不平地面放稳的数学模型

在凸凹不平的地面上，很难一次将四条腿桌子放稳，但在任何位置，四条腿桌子至少有三条腿着地，然而将四条腿桌子旋转调整几次，就可以使其放稳。本文先就桌子四脚的连线呈正方形的情形建立了数学模型，然后再推广到桌子四脚连线呈长方形的情形，并给出了模型解释。     

线性代数教学改革中融入数学建模思想的探讨

将数学建模的思想融入到高校数学教学改革中,是当前应用型本科教学改革的一项重要举措。本文探讨了如何将数学建模的思想融入到线性代数课程教学中,旨在培养学生运用数学知识解决实际问题的能力,提高学生的数学素养和创新思维。     

线面积分的类比教学法

高等数学是大学理工科专业的一门必修学位课。线面积分(曲线积分与曲面积分)是高等数学中下册中的一个重难点。很多同学在学习曲线积分和曲面积分时感到很茫然,无从下手。为了能让学生更好地掌握曲线积分与曲面积分,快速、准确地计算曲线积分与曲面积分,本文用类比法来讲解曲线积分与曲面积分,并结合Matlab 2018a软件来演示两类积分的区别。     

The Role of the Internet in the Adoption of Computer Modeling as Legitimate High School Science

We describe a recent project that explored combined use of Internet client-server technology and interactive computer modeling software for improving secondary science teaching. We envisioned a constructivist network in which teachers make contributions to the resources available. The purpose of the network was to promote the emerging field of computer modeling in high school science. Our approach coupled the networking and curricular initiatives with evaluation of changes in classroom core practices—those which have a traceable impact on student learning. Distribution of work, ideology of science, teaching styles, and curricular goals come together dynamically to influence teachers' use of modeling technology in the high school science classroom. A combination of Internet tools, each affording a different contribution to the spread of innovation, provides the best promise for future networks of this kind.     

Student learning approaches in the UAE: the case for the achieving domain

The deep versus surface learning approach dichotomy has dominated recent research in student learning approach dimensions. However, the achievement dimension may differ in importance in non-Western and vocational tertiary settings. The aim was to assess how Emirati tertiary students could be characterized in terms of their learning approaches. The study looked into emergent learning factors that may be important in Emirati students. The students were Emirati men in a first-year English for academic purposes programme at a tertiary college (N?=?252). The students completed the Revised Two-Factor Study Process Questionnaire (R-SPQ-2F) to determine learning orientation along the deep and surface approach dimensions. A factor analysis was carried out to assess emergent dimensions in the data. The results on the deep and surface dimensions were inconclusive. However, the factor analysis suggested a disposition towards a construct that we characterize as ‘attainment of satisfaction from learning’. In addition, the factor analysis suggested the possibility of the achieving domain emerging as a separate construct from the surface domain in this context, contrasting with previous research employing the R-SPQ-2F. The results suggest that the deep versus surface learning approach model may not sufficiently represent the complexity of student motivations and strategies in the current context. In addition, student affect tied to outcomes is discussed as an important though perhaps overlooked dimension in non-Western contexts. The implications of the results to future research are considered.     

基于MDT生成表驱动零件的研究

基于MDT生成表驱动标准件模型库的方法和步骤，对如何建立模型、使用设计变量、给模型分配设计变量以及设置和编辑电子表进行了详细的论述。实践证明，利用此方法建立标准件模型库方例快捷，能大大提高设计效率。     

基于AutoCAD的水工隧洞开挖断面的自动绘制与量算

开挖断面的绘制与量算是水工隧洞施工的一项日常性工作,传统方法的劳动强度大、工作效率低.本文介绍了利用AutoCAD制图及二次开发功能,实现水工隧洞开挖断面的自动绘制与量算.该方法应用于工程实践,提高了工作效率.     

浅谈轮胎胎侧滚花线的实现

阐述了如何实现圆锥面导向活络模具侧模胎侧上的滚花线以及改进工艺的方法，从而使子午线轮胎的质量得到了提高。     

Improvement of xylanase production by Aspergillus niger XY-1 using response surface methodology for optimizing the medium composition

Objective: To study the optimal medium composition for xylanase production by Aspergillus niger XY-1 in solid-state fermentation (SSF). Methods: Statistical methodology including the Plackett-Burman design (PBD) and the central composite design (CCD) was employed to investigate the individual crucial component of the medium that significantly affected the enzyme yield. Results: Firstly, NaNO3, yeast extract, urea, Na2CO3, MgSO4, peptone and (NH4)2SO4 were screened as the significant factors positively affecting the xylanase production by PBD. Secondly, by valuating the nitrogen sources effect, urea was proved to be the most effective and economic nitrogen source for xylanase production and used for further optimization.Finally, the CCD and response surface methodology (RSM) were applied to determine the optimal concentration of each sig-nificant variable, which included urea, Na2CO3 and MgSO4. Subsequently a second-order polynomial was determined by mul-tiple regression analysis. The optimum values of the critical components for maximum xylanase production were obtained as follows: x1 (urea)=0.163 (41.63 g/L), x2 (Na2CO3)=-1.68 (2.64 g/L), x3 (MGSO4)=1.338 (10.68 g/L) and the predicted xylanase value was 14374.6 U/g dry substrate. Using the optimized condition, xylanase production by Aspergillus niger XY-1 after 48 h fermentation reached 14637 U/g dry substrate with wheat bran in the shake flask. Conclusion: By using PBD and CCD, we obtained the optimal composition for xylanase production by Aspergillus niger XY-1 in SSF, and the results of no additional expensive medium and shortened fermentation time for higher xylanase production show the potential for industrial utilization.     

基于VHDL-AMS的结型场效应管行为建模与仿真

提出一种基于SPICE模型半导体器件的VHDL-AMS行为建模方法,给出了结型场效应管模型中温度效应、噪声、直流和电容方程的行为模型,最后以N沟道结型场效应管共源极放大电路为例在混合信号仿真器SMASH5.5中验证了模型的正确性。