热镀锌板表面锌层起泡原因探讨

热镀锌板在冲压成零件时,局部的镀锌层出现约3mm大小的起泡,将起泡用手术刀切开,撕下锌层,采用扫描电镜对起泡部位的基体以及锌层靠基体的表面进行了分析,对比分析正常部位纯锌层与基体之间的抑制层。结果表明:正常部位的抑制层为细小弥散分布的Fe2Al5颗粒,产生起泡的缺陷部位未见到抑制层颗粒,锌层与基板之间存在局部聚集的Al2O3夹渣,冲压成型后,夹渣松动,锌层与基板分离,导致锌层起泡。     

The effect of peer feedback for blogging on college students' reflective learning processes

Reflection is an important prerequisite to making meaning of new information, and to advance from surface to deep learning. Strategies such as journal writing and peer feedback have been found to promote reflection as well as deep thinking and learning. This study used an empirical design to investigate the interaction effects of peer feedback and blogging on college students' reflective thinking skills and their learning approaches. Forty-four first- and second-year undergraduate students participated in the study. Students kept blogs each week throughout a whole semester. Two journals were sampled at the beginning and end of the semester for each student. A repeated measure one-way ANOVA suggested that students' reflective thinking level increased significantly over time; however, peer feedback was found to negatively affect students' reflective thinking skills. The result of the study suggests more carefully designed uses in the future.     

速度攀岩运动员上肢肌表面肌电信号变化的研究

记录速度攀岩运动员上肢肌最大肌力的40%、60%和80%三种负荷强度下分别进行肘关节屈伸运动时腕屈肌和腕伸肌的表面肌电(sEMG)信号,并用MegaWin软件对之进行时、频阈指标的分析。结果表明:(1)sEMG信号分析中时阈指标AEMG和频阈指标MF、MPF都能较好监控速度攀岩运动员进行上肢肌力量训练时腕屈肌及腕伸肌的疲劳状况。(2)MF、MPF、AEMG出现显著下降时间的提前与负荷有着密切的关联,这为速度攀岩运动员训练上肢肌力量提供了科学的理论依据:教练员或运动员应根据上肢肌力量训练的持续时间来选择相应的运动负荷。(3)攀岩运动中腕屈肌与腕伸肌往往同步用力。所以,在平时的训练中都要重视腕屈肌、腕伸肌的力量训练,而不能有所偏向。     

Spectral Characterizations of Veronese Surface in S^4

In this paper,we prove that the Veronese surface can be determined by the 1-spectrum of the Laplace operator.     

旋转二次曲面透镜基点和基面的位置确定

在光学仪器中,非球面透镜具有一定的实用价值,故对旋转二次曲面透镜光学性质的研究将有重要意义．根据等效光学系统理论和旋转二次曲面折射的焦距公式,并考虑了透镜两曲面的不同形状及不同曲率,导出了旋转二次曲面透镜的主距公式和焦距公式,统称为旋转二次曲面的基点位置公式．这些公式具有一般性,该文进行了分类讨论,最后给出了应用实例     

应用“点线面分析法”提高空间想象能力

组合体的读图与画图在工程制图课程中是重点和难点,正确理解投影面垂直面的“类似形”投影是关键。文中作者提出用“点线面分析法”来求解“类似形”。综合应用“点线面分析法”和“形体分析法”,能够帮助学生识读和绘制组合体,并提升学生的空间想象能力。     

中国县域地面坡谱分级及其与人口分布的关系

针对平均坡度指标难以稳健描述地面坡谱特征的问题,提出一种基于频率累加分位归并的坡谱分级方法。作为验证,运用数字高程模型数据将全国县域分为5个坡级,借助2000年和2020年人口普查数据分析了坡级与人口分布的关系。结果发现：（1）所提出的分级方法包含频率累加曲线的构建、基于分位数的参考曲线生成、基于相似度的类型归并3个关键步骤,由此得到的全国县域坡级划分方案具备稳健坡度梯度性、宏观空间连片性以及清晰地学含义。（2）全国县域人口数量总体保持随坡级升高而波动式缩小的特征,且二者间呈现明显的线性负相关关系,线性拟合R2从2000年的0.761上升到了2020年的0.845,20年间人口总数变化量与坡级的线性拟合R2达0.963;人口密度的极端值对其自身的坡级分布有较大影响,当剔除人口密度小于20人/km2和大于2000人/km2的区域后,两个分析年份全国县域人口密度均稳健保持着随坡级升高而线性减小（R2> 0.985）。本文为稳健表达如坡度等环境梯度提供了一种新的可行分级方法,并深化了对中国县域人口分布与坡度关系的认识。     

Surface superconductivity in the type II Weyl semimetal TaIrTe4

The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically non-trivial and host exotic Majorana modes. The layered material TaIrTe₄ is a newly predicted time-reversal invariant type II Weyl semimetal with the minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe₄. Our scanning tunneling microscopy/spectroscopy (STM/STS) visualizes Fermi arc surface states of TaIrTe₄ that are consistent with the previous angle-resolved photoemission spectroscopy results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (T_c) up to 1.54 K being observed. The normalized upper critical field h*(T/T_c) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, and thickness- and angular-dependent transport measurements reveal that the detected superconductivity is quasi-1D and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe₄ provides a new novel platform to explore topological superconductivity and Majorana modes.     

Exploring Developmental Appropriateness of Multitouch Tables in Prekindergarten: A Video Analysis

This study explored how developmentally appropriate practices influenced the affordances of a multitouch surface in an early childhood classroom. Children, ages 4 to 5 years old, were videotaped while engaged in a storymaking application on a multitouch table. As a result of the study, we found that some challenges with the functionality undermined children's autonomous control. The researchers observed numerous instances of issues with control of the medium, including height of the table, sensitivity to multiple types of touch, and limited instructions and prompts. Implications for future research and practice are discussed.     

Vibration shape testing of space sheet structure

The space sheet for a solar array structure is large in dimension, and flexible to induce complex distortion. It is difficult to measure the distortion. A large-scale flexible test prototype system is built for sheet structure vibration monitoring based on the vibration information of the solar array in space. The system provides an intelligent test method for flexible space structure with embedded sensors and non-visualization reinstruction. Multiple fiber Bragg grating （FBG） sensors are packaged and embedded into the structure with spatial division multiplexing （SDM） and wavelength division multiplexing （WDM）. The sensor interrogator distinguishes wavelength shifts that can be turned into curvature of the curve. The structure shape is reconstructed based on the curvature information and the arc-length, and then displayed. The experiment shows that the system has a high FBG sensitivity. The reconstruction algorithm is fast with high precision. The system has great potential for use in health monitoring of the space sheet structure.