Nonlinearity in regulating the metal to insulator transition of ReNiO3 towards low temperature range

Among the existing material family of the correlated oxides, the rare earth nickelates (ReNiO₃) exhibit broadly adjustable metal to insulator transition (MIT) properties that enables correlated electronic applications, such as thermistors, thermochromics, and logical devices. Nevertheless, how to accurately control the critical temperature (T_MIT) of ReNiO₃ via the co-occupation of the rare-earth elements is yet worthy to be further explored. Herein, we demonstrate the non-linearity in adjusting the T_MIT of ReNiO₃ towards lower temperatures via introducing Pr co-occupation within ReNiO₃ (e.g., Pr_xNd_1-xNiO₃ and Pr_xSm_1-xNiO₃) as synthesized by KCl molten-salt assisted high oxygen pressure reaction approach. Although the T_MIT is effectively reduced via Pr substitution, it does not strictly follow a linear relationship, in particular, when there is large difference in the ionic radius of the co-occupation rare-earth elements. Furthermore, the most significant deviation in T_MIT from the expected linear relationship appears at an equal co-occupation ratio of the two different rare-earth elements, while the abruption in the variation of resistivity across T_MIT is also reduced. The present work highlights the importance to use adjacent rare-earth elements with co-occupation ratio away from 1:1 for achieving more linear adjustment in designing the metal to insulator transition properties for ReNiO₃.     

基于人工神经网络的智能化架空线路应变快速解调方法北大核心

为了提高智能化光纤复合架空线路态势感知的实时性,将人工神经网络方法应用于光纤沿线应变解调,确定了神经网络的结构。编程实现了基于洛伦兹模型的最小二乘谱拟合方法和神经网络方法,采用不同信噪比和布里渊频移的布里渊谱训练神经网络,将它们应用于某光纤复合架空线路沿线光纤应变的测量,从不同角度比较了两种方法的计算结果。计算结果表明,神经网络方法能有效获得光纤沿线的布里渊频移进而获得应变,具有与谱拟合方法相似的准确性,但应变解调时间仅约为谱拟合方法的1/20000。研究结果为提高智能光纤复合架空线路态势感知的实时性提供了参考。     

新工科背景下电子通信专业“人工智能技术基础”课程改革实践

人工智能技术已经成为新一轮科技革命的重要驱动力量，这要求电子、通信等非计算机专业的人才培养引入针对性强的人工智能课程教学。本文针对新工科背景下电子、通信专业“人工智能技术基础”课程存在的问题进行课程改革，从授课和实验两个环节入手，分别从教学内容、教学方法和考核办法三个方面提出了具体的改革举措，并在“人工智能技术基础”课程中进行了实践，激发了学生的学习热情，拓展了学生的专业视野，提高了学生的实践创新能力，取得了良好的教学效果。为了进一步培养电子、通信学科交叉型AI人才，该课程选拔优秀学生开展丰富的人工智能课外实践活动，进一步提升学生的实践创新能力。     

纳米零价铁材料对放射性核素的 去除及机理研究进展

随着人类社会的发展，放射性铀矿的开采和使用越来越多，环境面临着越来越严重的放射性污染问题。从生物和环境的角度来看，有效地清除环境中的放射性核素是核能利用过程中最重要的问题之一。纳米零价铁（nanoscale zero valent iron, nZVI）具有较大的比表面积和较高的活性位点，能显著提高放射性污染物的修复效率。本综述的目的是展示nZVI基材料对放射性核素的高效去除能力和环境修复作用。简介了常用的nZVI基材料（表面改性或多孔材料支撑的nZVI材料）及其对放射性核素的去除效果和相互作用机制（如吸附和氧化还原）。最后，对nZVI材料的应用和挑战给出个人见解。本综述有助于为高效去除放射性核素的nZVI材料的设计指明方向，为放射性核素的高效处理处置提供新材料。     

Mathematical model for coal conversion in supercritical water: reacting multiphase flow with conjugate heat transfer

Providing heat for supercritical water gasification (SCWG) of coal by coupling subsequent products oxidation in integrated supercritical water reactor (ISWR) provides an effective method for directional control of temperature field and avoids excessive hot spots caused by uniform heating. An exploratory numerical model incorporating particle-fluid flow dynamics, multispecies transport and thermal coupling between endothermic coal gasification and exothermic product oxidation was established to simulate the reacting multiphase flow process of coal conversion in a novel lab-scale ISWR. An eleven-lump kinetic model was proposed for the prediction of chemical reactions. And the thermal coupling relationship was described by conjugate heat transfer boundary conditions (BC). Detailed physical and chemical field distribution in ISWR were analyzed and influence factors were discussed. The results showed that oxidation of gas products as inner heat source could promote the gasification reaction with only slight or even little maximum temperature increase of the pressure-bearing wall. Coal feeding rate and oxygen supply method significantly affected the field distribution. The multi-injection compressed-air supply method provided a more uniform temperature field but would reduce heat transfer temperature difference. The carbon gasification efficiency (CGE) in the gasification zone could easily reach up to 97% under mild conditions (less than 650 °C).     

Photoluminescence and thermal expansion of zirconium vanadate

The optical property and phase transition of ZrV₂O₇ were investigated by temperature-dependent X-ray diffraction, photoluminescence (PL), and Raman spectra. It was found that the material exhibited PL emission in the visible region. The temperature-dependent PL emission showed that the peak energy for emission (at red wavelength) presented a red shift from 10 to 80 K, and then a blue shift with the increase in temperature. The PL emission bands of ZrV₂O₇ shifted with change in temperature relating to its phase transition (80-100 K), which could be confirmed by temperature-dependent Raman spectra.     

冠状动脉系统的微分积分终端滑模混沌抑制

冠状动脉系统的混沌现象会导致严重的健康问题。以非线性冠状动脉系统为研究对象，建立了不确定性冠状动脉系统动力学模型，提出了不确定性冠状动脉系统的微分积分终端滑模混沌抑制方法，针对该模型的不确定性设计了扰动观测器，根据Lyapunov理论证明了所设计控制系统的稳定性，通过仿真实验验证了所提出的混沌抑制方法的有效性和可行性。     

超亲水毛细芯环路热管启动及热性能分析

为解决电子设备高热通量下的散热问题，采用H₂O₂氧化法对烧结毛细芯进行了超亲水改性，研究了毛细芯表面润湿性对吸液性能的影响。并将改性后的超亲水毛细芯应用到环路热管内，研究了倾斜角度及加热功率对超亲水毛细芯环路热管的换热特性的影响。实验结果表明：超亲水毛细芯的吸液速度增加，吸液时间较亲水毛细芯减小了3.52ms；与普通亲水毛细芯环路热管相比，在加热功率Q=200W时，超亲水毛细芯环路热管蒸发器中心温度降低了约6.0℃，在Q=20W时启动时间与温度分别降低了33s与2.5℃。同时发现超亲水毛细芯环路热管在正重力状态时的运行温度更低，热阻较小，最低热阻仅为0.084℃/W。