Antiperovskites with Exceptional Functionalities

ABX₃ perovskites, as the largest family of crystalline materials, have attracted tremendous research interest worldwide due to their versatile multifunctionalities and the intriguing scientific principles underlying them. Their counterparts, antiperovskites (X₃BA), are actually electronically inverted perovskite derivatives, but they are not an ignorable family of functional materials. In fact, inheriting the flexible structural features of perovskites while being rich in cations at X sites, antiperovskites exhibit a diverse array of unconventional physical and chemical properties. However, rather less attention has been paid to these “inverse” analogs, and therefore, a comprehensive review is urgently needed to arouse general concern. Recent advances in novel antiperovskite materials and their exceptional functionalities are summarized, including superionic conductivity, superconductivity, giant magnetoresistance, negative thermal expansion, luminescence, and electrochemical energy conversion. In particular, considering the feasibility of the perovskite structure, a universal strategy for enhancing the performance of or generating new phenomena in antiperovskites is discussed from the perspective of solid-state chemistry. With more research enthusiasm, antiperovskites are highly anticipated to become a rising star family of functional materials.     

基于单神经元PID的真空炉自适应温度控制

根据真空热处理系统的特点,将单神经元PID控制算法应用到真空热处理系统的温度控制上。根据神经网络的非线性逼近能力和自学习自适应的特点,将单神经元网络与PID控制结合实现对真空炉温度的控制,以达到提高真空炉温度控制品质的目的。并通过计算机仿真软件进行仿真试验,仿真结果表明单神经元PID控制系统可以对控制参数自整定,其对温度控制更加稳健,具有更强的抗干扰能力和鲁棒性。经过搭建真空炉温度控制系统试验平台验证后发现,应用单神经元PID控制的真空炉系统的温升过程表现出了良好的稳定性,但是温度控制的响应速度和保温的精度略有下降。要想进一步提高温控品质,需要就单神经元PID控制方法在响应速度和控制精度上做进一步改进。     

新冠肺炎应急临床试验设计中的统计学考虑

新型冠状病毒肺炎的突然来袭，国内各地相继启动重大突发公共卫生事件一级响应。为了探索新冠肺炎的治疗，百余项临床研究陆续在国内开展。在突发公共卫生事件下，尽早找到有效的药物和治疗方案对于疾病的控制更加重要，这也对在这种应急情况下所开展临床试验的时效性提出要求，尤其是针对新冠肺炎的注册临床试验。本文从统计学角度，对应急临床试验中临床终点的选择和试验设计中的相关问题进行探讨。     

一种新型高杆灯灯盘挂接装置模型的设计与实验研究

高杆灯是由钢制柱型灯杆和大功率组合式灯架构成的新型照明装置。文中对高杆灯顶部灯盘的挂接进行研究,设计了一套挂接和脱卸方便,电极对接可靠的灯盘挂接装置模型,以指导实际产品的设计制作。通过改变挂接方式与挂接装置结构,借助SolidWorks软件进行三维模型结构设计,加工装配得到挂接装置实物模型。整套机构模型利用单片机控制,引导灯盘挂接顺利完成。     

β-B-BiW9O33夹心型铋（III）钨酸盐的合成、结构及光谱性质

用常规法合成了一种新的一维链状结构的夹心型多酸Na10{[(Cu(H2O)3)2(WO2)2(BiW9O33)2]}·23.5H2O(1),并对其进行X射线单晶结构分析、元素分析、红外光谱和紫外光谱表征。结果显示,该多酸阴离子属于单斜晶系, P2(1)/n空间群,晶胞参数a=1.2865(26) nm, b=2.52563(49) nm, c=1.62185(41) nm,β=94.03(4)°, V=5.20836(1093) nm3, Z=2, R1=0.0539,ωR2=0.1189, Dc=3.36 g/cm3。紫外光谱在236和293 nm有两个多酸特征的吸收峰。     

The relationship between crystallization and break temperature of mould flux

ABSTRACT

Many researchers believe that crystallization is responsible for drastic viscosity changes near the break temperature of mould flux; however, there are no reasonable experimental data to support this view. In this study, the complete crystallization process is recorded in situ by inhibiting the volatilization of fluoride, and the relationship between viscosity change and crystallization near the break temperature is studied. Mould flux with a basicity of 0.65 had no break temperature, and no crystallization occurs within the temperature range of the viscosity test. The other three mould fluxes begin to crystallize before the break temperature, but the crystal volume fractions at the break temperature are different. The break temperature of mould flux is the crystallization temperature with a critical crystal volume fraction, which is related to the viscosity before the break temperature. The higher the viscosity, the smaller the critical crystal volume fraction. Therefore, break temperature?≤?initial crystallization temperature.     

The effect of the exposed crystal plane on the antioxidant activity of nanoceria

Previous reports have noted that exposed crystal planes could affect the antioxidant activity of nanocerias, although the synthesized nanocerias used in those studies had different exposed crystal planes, as well as different sizes and morphologies. In order to better understand the effect of the crystal planes on the antioxidant activity of the materials, two types of nanocerias with similar morphology and size distribution but different crystal planes were synthesized using the hydrothermal method (CeO₂–H) and the ultrasonic template method (CeO₂–U). The antioxidant activities of the nanocerias were further explored within different ·OH concentrations in the reaction system. The experimental results showed that there is an obvious difference in the antioxidant activity of the two types of nanocerias in the lower free radical concentration system due to the effects of exposed crystal planes. CeO₂–U, with more active crystal planes (100), had stronger antioxidant activity. However, with the increase in the ·OH concentration in the reaction system, the difference in the antioxidant activity of the two nanocerias decreased. This research will increase our understanding of the antioxidant activity of the exposed crystal planes on nanocerias.     

Single-Crystalline TiO2(B) Nanobelts with Unusual Large Exposed {100} Facets and Enhanced Li-Storage Capacity

The {100} facet of single-crystalline TiO₂(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO₂(B) nanobelts from H₂Ti₃O₇ with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO₂ formula with specific capacity up to 335 mAh g⁻¹, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g⁻¹ after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures.