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1.
本文主要总结了新冠疫情期间作者的电磁场理论课程在线教学经验。对比分析了录播和直播的优缺点后,选择录播教学方式。基于超星网络教学平台,展示了录播网络教学的具体措施,包括网上答疑和学习效果检查以及在线批改作业等。给出了网络教学可以为线下教学继续使用的方法和手段,为疫情结束后的正常教学提供了新的网络教学补充措施。 相似文献
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Sumeng Wei Yining Xu Baohua Kong Meijuan Wang Jingming Zhang Qian Liu Yuling Yang 《International Journal of Food Science & Technology》2022,57(8):5024-5035
The present work was conducted to illustrate the mechanism of gel formation of myofibrillar proteins (MPs) under different microwave heating times. The results showed that the denaturation enthalpy (ΔH) of the MPs significantly decreased when the heating time increased from 3 to 9 s and then completely disappeared as the heating time progressed, indicating that the MPs gradually denatured and subsequently aggregated with increasing heating time, which was further verified by the changes in the secondary structure, electrophoretic bands, and gel properties (e.g., water holding capacity and textural profiles) of the MPs. Microstructural images indicated that the MP gel formed under 12 s had the most compact network, indicating that extended microwave heating time could induce quality deterioration of MP gels. Moreover, the hydrophobic forces, electrostatic forces, and disulphide bonds of the MPs gradually intensified with increasing microwave heating time, suggesting that both non-covalent and covalent bonds could promote molecular denaturation and subsequent aggregation of MPs. In addition, correlation analysis revealed that the changes in the molecular conformation of MPs induced by different microwave heating times could effectively regulate the formation of MP gels and their related properties. 相似文献
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目的 对某福利院一起肠炎沙门菌食源性疾病进行调查和溯源,为研究相关食源性疾病提供参考。方法采用流行病学、食品卫生学和脉冲场凝胶电泳(PFGE)同源性分析等方法,分析本次食源性疾病事件。结果 确认本次事件中病例23名,患病率5.65%(23/407);现场采集病例肛拭子15份和厨房工作人员肛拭子3份、留样菜品3份、水果2份以及冰棒1份,其中从11份病例肛拭子中检出肠炎沙门菌,PFGE结果显示11株肠炎沙门菌的DNA条带图谱相似性为96.4%,聚类分析为同一型,结合流行病学调查,初步判断菌株来自同一克隆系。结论 综合流行病学、食品卫生学和实验室检测结果,确定为一起肠炎沙门菌引起的食源性疾病,福利院应加强对特殊人群的饮食安全管理,制定相应的食源性疾病突发事件应急处理预案,防止此类事故再发生。 相似文献
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The ceramic joining using electric field (E-field) has garnered significant research attention due to the decreased joining barrier and enhanced reliability. However, the underlying mechanism of E-field assisted joining remains unclear. Herein, we report the rapid joining of alumina ceramics using a small current. Moreover, the E-field is applied in both perpendicular and parallel directions to the faying surfaces, demonstrating a significant difference in terms of joint strength. These results indicate that the E-field generates defects and promotes the joining process by facilitating ionic diffusion. 相似文献
7.
《Journal of the European Ceramic Society》2021,41(15):7381-7403
Silica-based ceramics have been explored extensively as a class of versatile materials for various applications in architecture, catalysis, energy, machinery, and biomedical engineering. Nevertheless, comprehensive information on silica-based ceramic and electromagnetic microwave (EMW) absorption is scarce, although excellent progress has been made in this field. Here, recent progress in the investigation of silica-based ceramics toward EMW absorption is reviewed. We first introduced the basis of ceramics (characteristics, classification, synthetic methods, potential applications). Subsequently, the silica-based ceramics, including Si-based oxides and alloys, SiOC/SiC/Si3N4/SiCN-based composite, Ti3SiC2 and composite for EMW absorption were systematically summarized. Notably, the fabrication strategies, absorption properties, and mechanisms of silica-based ceramics are described in detail, with a focus on structure and component design. Lastly, the prospects and ongoing challenges of this field in the future are presented. This review is expected to learn from the past and achieve progress toward the future of silica-based ceramic for EMW absorption. 相似文献
8.
微波隔离器是微波系统中不可或缺的器件,常见的隔离器都采用了铁氧体旋磁材料配合吸收负载实现电磁波的单向传输。这种器件虽然可以使电磁波单向传输,但是并不能改善能量的浪费问题,还增加了系统的复杂度。针对上述问题,本文基于电磁超材料设计了一种微波单向传输的圆波导,使用波导内壁涂覆折射率逐渐变化的材料来影响电磁波的传输特性,从而实现电磁波单向传输。本文给出了微波单向传输的电磁计算模型和超材料结构及属性,并通过简化这种超材料使其易于实现;最后通过电磁仿真分析了这种材料的电磁特性并给出了这种材料的实现方法。 相似文献
9.
《Ceramics International》2022,48(10):13719-13731
Li0.04Ca0.96-xSiO3:Smx orange?red emitting phosphors were synthesized using the sol-gel method. X-ray diffraction, Rietveld refinement of XRD patterns, Fourier transform infrared spectroscopy and ?uorescence spectrophotometry were used to characterize the crystal structure, sites of cationic Ca and luminescence properties of the prepared phosphors. The relationship of the different Ca sites in the matrix with the luminescence properties was analysed. The results indicate that the prepared phosphors reveal a β-CaSiO3 phase with a monoclinic crystal structure and space Group P21/a. As the Sm3+ concentration increases, the unit cell volume of phosphors and the Ca–O band lengths of different Ca sites decrease due to substitution of Ca2+ by smaller Sm3+ ions. By excitation at 404 nm, Li0.04Ca0.96-xSiO3:Smx phosphors exhibit warm orange?red light, corresponding to the electron transitions from 4G5/2 → 6H5/2 (567 nm), 4G5/2 → 6H7/2 (605 nm) and 4G5/2 → 6H9/2 (651 nm) of Sm3+. The concentration quenching phenomenon appears at Sm3+ concentrations beyond 0.02. The refinement results demonstrate that three cationic Ca sites, named Ca1, Ca2 and Ca3, exist in the β-CaSiO3 host lattice. The Ca2+ ions at Ca1 and Ca2 sites are coordinated with six oxygen ions, leading to the same coordination number (CN). The Ca2+ ion located at Ca3 site has seven coordination numbers. The Ca1 site possesses a smaller lattice distortion and better symmetry than those of Ca2 and Ca3 sites. However, the Ca3 site exhibits the largest lattice distortion and poor symmetry. The Sm3+ present in symmetric Ca1 sites in the matrix illustrates the strong emission intensity, long luminescence lifetimes and good thermal stability. 相似文献
10.
While the challenges associated with the stability of metal halide perovskites are well known and intensely studied, variability in electronic properties represents an equally significant, yet seldom studied, challenge that could potentially slow or inhibit the commercial viability of these systems. In this work, the contactless characterization technique time-resolved microwave conductivity (TRMC) is used to quantify the variability in electronic properties of the prototypical perovskite, methylammonium lead iodide (MAPbI3) both between different samples, and at different locations within the same sample. Using scanning electron microscopy (SEM) and a quasi-automated image-analysis strategy, it is possible to evaluate the metrics of heterogeneity in surface microstructure and correlate them with the electronic properties as obtained by TRMC. Substantial intra-sample and inter-sample variation is observed in the mobility-yield product in samples prepared following differing protocols, and in samples prepared following identical protocols. 相似文献