Exploring the Core-shell Structure of BaTiO3-based Dielectric Ceramics Using Machine Learning Models and Interpretability Analysis

A machine learning(ML)-based random forest(RF)classification model algorithm was employed to investigate the main factors affecting the formation of the core-shell structure of BaTiO_(3)-based ceramics and their interpretability was analyzed by using Shapley additive explanations(SHAP).An F1-score changed from 0.8795 to 0.9310,accuracy from 0.8450 to 0.9070,precision from 0.8714 to 0.9000,recall from 0.8929 to 0.9643,and ROC/AUC value of 0.97±0.03 was achieved by the RF classification with the optimal set of features containing only 5 features,demonstrating the high accuracy of our model and its high robustness.During the interpretability analysis of the model,it was found that the electronegativity,melting point,and sintering temperature of the dopant contribute highly to the formation of the core-shell structure,and based on these characteristics,specific ranges were delineated and twelve elements were finally obtained that met all the requirements,namely Si,Sc,Mn,Fe,Co,Ni,Pd,Er,Tm,Lu,Pa,and Cm.In the process of exploring the structure of the core-shell,the doping elements can be effectively localized to be selected by choosing the range of features.

国际协同研究生培养模式探索——基于武汉理工大学国际化示范学院的实践

结合高校国际协同培养研究生存在的认知偏差、体制机制障碍、有效模式缺乏等共性问题,武汉理工大学国际化示范学院对人才培养模式等进行了整体制度设计,开展了实行流入流出竞争机制、优化国际化人才选拔制度,探索多元人才联培形式、创建国际化支撑教育平台,汇聚校企世界高端人才、打造国际化优秀导师团队,搭建国际交流六大平台、营造国际化浓郁文化氛围等具体实践。认为高校在国际协同培养人才方面的改革走向是:培养理念迈向国际化、本土化融通,培养对象实施普惠式、多元化延伸,培养资源实行自主性、系统化转换,培养制度实现层级化、差异化发展转变。

Influence of Organic Cations on the Crystal and Electronic Structures of Two-dimensional Lead Iodide Perovskites

The crystal structures and electronic structures(including band gap,project density of states,partial charge density,effective mass and electron localization function)of the 2D lead iodide perovskites hybrids with different organic spacer cations of 4-fluorophenylethanaminium(4F-PEA^(+)),ethanolamine(EA^(+)),thienylethylamine(TEA^(+))were investigated using first-principles calculations.It was found the higher dipole moment,the stronger the hydrogen bonding between the organic amino and iodide in the inorganic layer,and the larger the[PbI_(6)]^(4-)octahedral distortions in these crystal structure.Further quantifying the degree of the distortions using OctaDist software showed that the distortion of adjacent[PbI_(6)]^(4-)octahedra had a decisive effect on the band gap.Specifically,the greater deviation of Pb-I-Pb bond angles from 180°,together with the larger distortion of multiple[PbI_(6)]^(4-)octahedron resulted in a wider band gap,which was verified by calculated band gap using different DFT methods.The results outlined the relationships of hydrogen bonding,ocathedra distortion and band structure in 2D perovskites,highlighting the importance of the cations on the structural tuning and optoelectronic properties.

First Principle Study of Cesium-based Lead-free Halide Double Perovskites

Inorganic halide double perovskites A_(2)B'B"X_(6) have gained significant interests for their diverse composition,stable physicochemical properties,and potential for photoelectric applications.The influences of trivalent and monovalent cations on the formation energy,decomposition energy,electronic structure and optical properties of cesium-based lead-free Cs^(+)_(2)B'B"Br_(6) (B'=Na^(+),In^(+)Cu^(+),or Ag^(+);B"=Bi^(3),Sb^(3+),In^(3+)) are systematically studied.In view of the analysis and results of the selected double perovskites,for the double perovskites with different B-site trivalent cation,the band gap increases in the order of Cs_(2)AgInBr_(6),Cs_(2)AgSbBr_(6) and Cs_(2)AgBiBr_(6),with Cs_(2)AgBiBr_(6) possessing the highest thermodynamic stability.Therefore,the Bi-based perovskites are further studied to elucidate the effect of monovalent cation on their stability and electronics.Results show that the thermodynamic stability rises in the sequence of Cs_(2)NaBiBr_(6),Cs_(2)InBiBr_(6),Cs_(2)AgBiBr_(6) and Cs_(2)CuBiBr_(6).Notably,Cs_(2)CuBiBr_(6) exhibits a relatively narrow and appropriate band gap of 1.4634 eV,together with the highest absorption coefficient than other compounds,suggesting that Cs_(2)CuBiBr_(6) is a promising light absorbing material that can be further explored experimentally and be applied to optoelectronic devices.Our research offers theoretical backing for the potential optoelectronic application of cesium-based lead-free halide double perovskites in solar energy conversion.

Enhanced Electrochemical Performances of Ni Doped Cr_(8)O_(21)Cathode Materials for Lithium-ion Batteries

Cathode materials,nickel doped Cr_(8)O_(21),were synthesized by a solid-state method.The effects of Ni doping on the electrochemical performances of Cr_(8)O_(21) were investigated.The experimental results show that the discharge capacities of the samples depend on the nickel contents,which increases firstly and then decreases with increasing Ni contents.Optimized Ni_(0.5)Cr_(7.5)O_(21)delivers a first capacity up to 392.6 m Ah·g^(-1)at 0.1C.In addition,Ni doped sample also demonstrates enhanced cycling stability and rate capability compared with that of the bare Cr_(8)O_(21).At 1 C,an initial discharge capacity of 348.7 m Ah·g^(-1)was achieved for Ni_(0.5)Cr_(7.5)O_(21),much higher than 271.4 m Ah·g^(-1)of the un-doped sample,with an increase of more than 28%.Electrochemical impedance spectroscopy results confirm that Ni doping reduces the growth of interface resistance and charge transfer resistance,which is conducive to the electrochemical kinetic behaviors during charge-discharge.

基于深度网络模型的牛脸检测算法比较

针对传统检测方法在牛脸检测应用方面存在的检测设备易损、检测结果不理想等问题,根据大数据、多差异性原则,使用手机和相机在某奶牛养殖场采集奶牛数据,构建了一个超过10 000张不同条件下(如遮挡、模糊、光照变化等)的奶牛数据集.在此基础上使用目前有代表性的基于深度网络模型的目标检测方法(如SSD,Faster R-CNN和R-FCN等)对该数据集进行试验对比分析.结果表明:Faster R-CNN模型综合检测精度最高,可达0.990,但其检测速度相对较慢,为11 F·s^(-1);SSD模型的检测速度最快,为47 F·s^(-1),但其检测精度与Faster R-CNN相比略低,约为0.945.

Synthesis and characterization of LiNi_(0.95-x)Co_xAl_(0.05)O_2 for lithium-ion batteries

Samples of LiNi0.95-xCoxAl0.05O2 （x = 0.10 and 0.15） and LiNiO2, synthesized by the solid-state reaction at 725℃ for 24 h from LiOH-H2O, Ni2O3, Co2O3, and AI（OH）3 under an oxygen stream, were characterized by TG-DTA, XRD, SEM, and electrochemical tests. Simultaneous doping of cobalt and aluminum at the Ni-site in LiNiO2 was tried to improve the cathode performance for lithium-ion batteries. The results showed that co-doping （especially, 5 at.% A1 and 10 at.% Co） definitely had a large beneficial effect in increasing the capacity （186.2 mA.h/g of the first discharge capacity for LiNio.s.42OoaoAlo.0502） and cycling behavior （180.1 mA-h/g after 10 cycles for LiNio.85CooaoAlo.osO2） compared with 180.7 mA.h/g of the first discharge capacity and 157.7 mA.h/g of the tenth discharge capacity for LiNiO2, respectively. Differen- tial capacity versus voltage curves showed that the co-doped LiNio.95_xCoxmlo.osO2 had less intensity of the phase transitions than the pristine LiNiO2.

高气压直流辉光CH4/H2等离子体放电过程中的占空比效应

对高气压下直流均匀辉光放电的脉冲占空比效应进行了研究。在1.7 kHz脉冲放电条件下,当占空比高于73%时,脉冲间隔后电压需要经过10~20μs的上升时间至稳定;而电流增长明显地滞后于电压的上升,整个增长过程需要的时间约是电压上升时间的10倍。减小占空比,表示电流增长快慢程度的时间常数τ几乎线性增加。这是因为小占空比时,上升通道开始时刻的等离子体电子密度低,放电电流需要更长时间才能稳定。在高气压条件下,粒子碰撞效应显著增强,增加的放电功率被更多地被用于加热中性粒子,表现为Hα、Hβ等发射光谱强度随占空比降低而增加。进一步减小占空比,电子密度n_e衰减到过低,时间常数τ增加到一定值时,放电就难以维持,表现为放电不稳定乃至熄灭。

Effect of Constituent Core-sizes on Microstructure and Dielectric Properties of BaTiO_3@(0.6BaTiO_3-0.4BiAlO_3) Core-Shell Material

The fundamental characteristics of varied initial core-sizes of Ba Ti O3（BT） and its influential role on the morphology and dielectric properties of Ba Ti O3@0.6 Ba Ti O3-0.4 Bi Al O3（BT@0.6 BT-0.4 BA） ceramic samples were studied. Alkoxide sol-precipitation method was adopted as revised chemical route to synthesize the constituent ＂core＂ BT powders in a dispersed phase, whereas the distinctive initial nano-sized particles were affected by the pre-calcination temperatures（600-900 ℃）.The microstructure of the uncoated BT ceramics revealed an exaggerated grain growth with an optimized dielectric constant（ε（max） 〉9 000） whilst the coated ceramics behaved otherwise（grain growth inhibited） when sintered at an elevated temperature. Regardless of the previously studied solubility limit（about 0.1%） of BT-BA samples, BT@0.6 BT-0.4 BA maintained a maximum dielectric constant（ε（max）） ranging from 1 592 to 1 708 and tan δ less than 2% under a unit mole ratio at room temperature. In view of all these analyses, the initial nanometer sizes of the as-prepared BT-core powders combined with the increase effect of cation substitutions of Bi^（3＋） and Al^（3＋） in the shell content, induced the diffuse transition phase of BT@0.6 BT-0.4 BA composition.

单腔和双腔气管导管插管在手汗症患者胸腔镜下胸交感神经切断术中的应用

目的:比较单腔和双腔气管导管插管在手汗症患者胸腔镜下胸交感神经切断术中的应用效果。方法:2013年10月-2019年8月收治手汗症患者70例,均接受胸腔镜下胸交感神经切断术治疗。随机分为两组,各35例。对照组行双腔气管导管插管;观察组行单腔气管导管插管。比较两组相关指标。结果:两组患者同一时间心率和平均动脉压比较,差异无统计学意义(P>0.05);两组患者手术结束时心率低于麻醉前,且膨肺维持正压时、另一侧膨肺维持正压时的平均动脉压明显低于麻醉前,差异有统计学意义(P<0.05)。观察组患者气管插管时间短于对照组,术后疼痛程度轻于对照组,并发症发生率低于对照组,差异有统计学意义(P<0.05)。结论:手汗症患者在胸腔镜下胸行交感神经切断术中应用单腔和双腔气管导管插管均有一定的临床价值,采用单腔气管导管插管的操作时间更短、患者耐受性更强、安全性更高。

Synthesis and characterization of LiNi_(0.95-x)Co_xAl_(0.05)O_2 for lithium-ion batteries

Samples of LiNi0.95-xCoxAl0.05O2（x=0.10 and 0.15） and LiNiO2,synthesized by the solid-state reaction at 725?℃ for 24?h from LiOH·H2O,Ni2O3,Co2O3,and Al（OH）3 under an oxygen stream,were characterized by TG-DTA,XRD,SEM,and electrochemical tests. Simultaneous doping of cobalt and aluminum at the Ni-site in LiNiO2 was tried to improve the cathode performance for lithium-ion batteries. The results showed that co-doping （especially,5% Al and 10% Co in atomic fraction） definitely had a large beneficial effect in increasing the capacity （186.2?mA·h/g of the first discharge capacity for LiNi 0.85 Co 0.1 0Al 0.05 O2） and cycling behavior (180.1?mA·h/g after 10 cycles for LiNi0.95-xCoxAl0.05O2) compared with 180.7?mA·h/g of the first discharge capacity and 157.7?mA·h/g of the tenth discharge capacity for LiNiO2,respectively. Differential capacity versus voltage curves showed that the co-doped LiNi0.95-xCoxAl0.05O2 had less intensity of the phase transitions than the pristine LiNiO2.

Ab Initio Study of Doping Mechanisms in BaTiO3-BiYO3

A density functional plane-wave pseudopotential method is used to study the doping mechanisms of impurity defects（BiBa, YTi） in BaTiO3- BiYO3. Single BiBa and YTi impurities have little structure distortion. Bi forms ionic bond with nearby O atom in single Bi impurity, Y formed [YO6] octahedral in single Y impurity. However, in the co-doped BiB~ and Yr~ structure, Bi formed three valence bonds with nearby O atom, which causes the large structure distortion. The doped ion makes the mobile of Ti4~ difficult and loss local ferroelectricity, which will broaden the dielectric constant temperature curve and increase the temperature stability of BaTiO3 ceramic matrix.

Preparation and Properties of Epoxy Piezoelectric Vibration Reduction Composites

The epoxy resin (E-51) was used as polymer matrix,conductive carbon black (CB) as conductive filler,and PZT was used to prepare a composite by curing.The effects of PZT and CB content on the properties of PZT/ CB/ EP piezoelectric composite were studied.When the PZT content reaches 40 wt%,the optimized vibration attenuation properties of PZT/CB/EP materials could be achieved with a loss factor of 0.9 from room temperature to 60 ℃.With the increase of PZT content,the bending strength of PZT/CB/EP piezoelectric composite vibration reduction material firstly increased from 45 MPa to 65 MPa and then decreased to 38 MPa.At room temperature,the dielectric constant increased from 7 to 50,and the dielectric loss increased from 0.1 to 0.5.

Synthesis and Characterization of Layered Perovskite-type Organic-inorganic Hybrids(CnH2n+1NH3)2(CH3NH3)m-1PbmI3m+1(n=5-10,m=1,2)

Layered organic-inorganic hybrids（CnH2n＋1NH3）2（CH3NH3）m-1PbmI3m＋1 containing monolayer（m=1） and bilayer（m=2） perovsikte were synthesized by reactions in solution.The influences of the reactant ratio,solvent,reaction temperature,and reaction time on the structures of the products were investigated.The structures and the properties of the hybrids were characterized using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and ultraviolet and visible（UV） absorption spectroscopy.The XRD patterns and the SEM images demonstrate that the pure bilayer perovskite hybrids are obtained.The UV-vis spectra indicate that the number of the inorganic perovskite layer（m） has greater impact on the band gap than the number of the carbon atoms（n）.The band gap of bilayer hybrids（around 1.9 eV） is significantly less than that of monolayer hybrids（around 2.2 eV）.

两种不同材料环抱器在多根肋骨骨折中的应用

目的探讨两种不同材料环抱器在多根肋骨骨折中的应用效果。方法回顾性分析2016年1月至2021年4月于本院行环抱器治疗的74例多根肋骨骨折患者的临床资料,并根据环抱器材质的不同分为记忆合金组(n=32)与钛合金组(n=42)。比较两组围手术期指标、随访情况、临床疗效及术后并发症发生情况。结果两组手术时间、住院时间比较差异无统计学意义;记忆合金组视觉模拟评分法(VAS)评分低于钛合金组,差异有统计学意义(P<0.05)。两组切口愈合不佳、不吸氧SaO2<95%、胸廓畸形及环抱器固定在位发生率比较差异无统计学意义。两组总优良率、术后并发症发生率比较差异无统计学意义。结论记忆合金环抱器与钛合金环抱器应用于多根肋骨骨折中均具有显著疗效,记忆合金环抱器虽术后疼痛较轻,但不能塑性,使用受限;钛合金环抱器虽术后疼痛较重,但可塑形,适用于肋骨各个部位,临床治疗中可根据患者情况及需求选择合适的环抱器。

无监督学习探索高介电常数的ABO_(3)型钙钛矿材料

机器学习已成为新材料研发的重要变革性手段,但材料数据样本量少、噪音高等特点为数据驱动的研发模式带来巨大挑战。本工作将无监督学习应用于挖掘高介电常数的钙钛矿材料。针对标签数据少的问题,通过聚类学习的方法不断优化迭代来缩小搜索空间,最终筛选出了BaHfO_(3)和BiFeO_(3)等20种具有高介电常数潜力的钙钛矿材料,并通过降维分析等手段从元素种类、晶体结构和容忍因子等方面展开规律分析,挖掘钙钛矿材料结构与介电常数之间的关联。该方法为解决材料性能数据标签的缺失提供了一种思路,可应用于筛选和挖掘其他新型功能材料。

中亚七河地区公元前3世纪-公元3世纪考古遗存的发现与研究

20世纪50-70年代,由苏联考古学家对中亚七河地区的古墓葬进行了大量的考古发掘工作。在占有考古基础材料之上,对外伊犁河流域、楚河流域、塔拉兹河流域的时代属于公元前3世纪-公元3世纪的墓葬进行了纵向和横向的比较研究,以期找出这三处不同流域内的考古学文化遗存上的统一性与差异性,以及与域外不同考古学文化之间的交流与互动,并指出社会组织结构是造成此种文化类型的主要原因。