A bilinear differential forms approach to parametric structured state-space modelling

We use one-variable Loewner techniques to compute polynomial-parametric models for MIMO systems from vector-exponential data gathered at various points in the parameter space. Instrumental in our approach are the connections between vector-exponential modelling via bilinear differential forms and the Loewner framework.     

三株芽孢杆菌的生防特性研究

为明确贝莱斯芽孢杆菌（Bacillus velezensis）GY1、解淀粉芽孢杆菌（Bacillus amyloliquefaciens）GY10和枯草芽孢杆菌（Bacillus subtilis）GY12的生防特性,采用平板试验法、对扣法、盆栽试验等,对三株生防菌的抑菌谱、次生代谢产物、挥发性物质、根际定殖能力和促生能力等进行了研究。结果表明,GY1、GY10、GY12培养液可以显著促进烟草种子的萌发和烟株的生长;三株生防菌抑菌谱广,对烟草赤星病菌、黑胫病菌及花生镰刀菌等9种病原具有显著的抑制作用,并且都具有分泌嗜铁素和蛋白酶的能力;三株生防菌发酵上清液和挥发性物质对链格孢菌（Alternaria alternata）和烟草疫霉菌（Phytophthora parasitica var.nicotianae）具有显著抑制作用;菌株的分泌蛋白热稳定性好,对烟草赤星病菌具有显著的体外抑菌活性,并对酸性环境具有较高的耐受性;根际定殖结果表明,GY1-GY10-GY12复配与单菌株相比能增加各生防菌在烟草根际的定殖。以上结果对于菌株GY1、GY10、GY12生防特性的深入挖掘和产业化开发具有一定的指导作用。     

The structure and magnetic properties of magnesium-substituted LaFeO3 perovskite negative electrode material by citrate sol-gel

Perovskite-type composite oxide is a material as high-energy-density Ni-MH batteries. Due to the perovskite type oxide has a special crystal structure, and exhibits a rich variety of physicochemical properties, we study the affect of the Mg²⁺ doping amount, calcination temperature and calcination time for the microstructure, sample composition and magnetic properties of LaFeO₃. XRD patterns showed that all the samples are perovskite orthogonal structure and the space group is Pnma (No. 62). When the calcination temperature is in the range of 400 °C–600 °C, the samples are a single phase, no other impurities generated. When the temperature of 800 °C and 1000 °C, 2θ between 30° and 40° detected the second phase MgFe₂O₄ and miscellaneous phase peak intensity increases with the increase of calcination temperature and strengthen, and the calcination temperature had a direct effect on the grain size of the powder. When the calcination temperature is higher, the grain shape is better and the grain size is larger. The saturation magnetization of samples increases with the increase of Mg²⁺ concentration. The coercive force is decreased with the increase in Mg²⁺ concentration. The saturation magnetization and the residual magnetization of the sample are reduced when the sintering temperature from 400 °C rises to 600 °C. When the sintering temperature is 800 °C, the MgFe₂O₄ impurity phase appear. The iron oxide composition is increased, and the magnetic enhancement of the sample is enhanced. Magnetic studies show that when the calcination temperature is 600 °C, the magnetic parameters of the sample are the best.     

国外学生营养餐的发展对我国的启示

学生营养状况体现了国家的综合实力水平。国外学生营养餐开始较早,已经形成了基本成熟规范的运作模式,而我国尚处于学生营养餐发展的初始阶段。本文对国外学生营养餐的发展历史进行了回顾和介绍,通过对多个国家经典案例的分析,归纳和总结了国外在实施推广学生营养餐过程中的经验教训,旨在为我国开展学生营养餐计划提供参考和借鉴。     

基于卡口上下文和深度置信网络的车辆轨迹预测模型研究

针对车辆轨迹预测中节点序列的时序特性和实际路网中的空间关联性,该文提出一种基于深度置信网络和SoftMax (DBN-SoftMax)轨迹预测方法。首先,考虑到轨迹在节点集合中的强稀疏性和一般特征学习方法对新特征的泛化能力不足,该文利用深度置信网络(DBN)较强的无监督特征学习能力,达到提取轨迹局部空间特性的目的;然后,针对轨迹的时序特性,该文采用逻辑回归的预测思路,用当前轨迹集在路网特征空间中的线性组合来预测轨迹;最后,结合自然语言处理领域中的词嵌入的思想,基于实际轨迹中节点存在的上下文关系,运用节点的向量集表征了节点间的交通时空关系。实验结果表明该模型不仅能够有效地提取轨迹特征,并且在拓扑结构复杂的路网中也能得到较好的预测结果。     

2-(咪唑并[1,2-a]吡啶-3-基)乙酸的制备

研究了一种用于治疗骨质疏松症药物的关键中间体米诺膦酸的制备方法。实验以二乙氧基膦酰乙酸乙酯和2,2-二甲氧基乙醛为起始原料,经维蒂希-霍纳反应、水解、环合、水解4步制备得到标题化合物。其熔点与1HNMR和文献报道的结果一致,总收率87.5%(以2-氨基吡啶计)。该方法克服了文献报道的工艺缺陷,与现有技术相比,后处理更简单,更适合工业化生产。     

Enhanced photoelectric properties of CdSe/graphene composites with various contents of graphene

CdSe/graphene composites with different contents of graphene were prepared by the solvothermal method. The composites were characterized by X-ray diffraction, scanning electron microscope and further investigated by transient photocurrent responses and electrochemical impedance spectroscopy. Compared with pure CdSe particles, CdSe/graphene composites show improved photocurrent responses and decreased electron-transfer resistance due to the presence of graphene, which acts as an electron collector and transporter as well as the supporting matrix for CdSe particles. The composites were synthesized by varying the graphene content from 0.5 wt% to 6 wt%, which has been experienced to exert great influence on the photoelectric characteristics of CdSe/graphene composites. A higher photocurrent density and smaller arc radius can be observed for 0.5% CdSe/graphene composites.     

Synthesis of novel halloysite@YF3:Ce3+,Tb3+ nanocomposite for enhanced luminescent properties

A novel halloysite@YF₃: Ce³⁺, Tb³⁺ anocomposite with strong luminescent properties was designed and synthesized by a facile direct precipitation strategy. Owing to the halloysite as a support, it can significantly prevent the aggregation of YF₃:Ce³⁺,Tb³⁺ and the distribution of YF₃:Ce³⁺,Tb³⁺ on halloysite was highly uniform. Importantly, due to the unique surface-interface-dielectric multiple confinement (SIDMC) effects, the as-harvested halloysite@YF₃:Ce³⁺,Tb³⁺ nanocomposite exhibited excellent luminescent performance. Compared with YF₃:Ce³⁺,Tb³⁺, the luminescence intensity of halloysite@YF₃:Ce³⁺,Tb³⁺ nanocomposite is significantly enhanced by about 6 times under 255 nm excitation. However, the fluorescence lifetime of halloysite@YF₃:Ce³⁺,Tb³⁺ nanocomposite (7.21 ms) is shorter than that of YF₃:Ce³⁺,Tb³⁺ nanoparticles (8.34 ms). This finding indicated that halloysite can change the luminescent properties of YF₃:Ce³⁺,Tb³⁺ nanoparticles through an SIDMC effect. The combination of halloysite and YF₃:Ce³⁺,Tb³⁺ nanoparticles not only endowed halloysite with special properties, and effectively tuned the luminescent properties of YF₃:Ce³⁺,Tb³⁺ nanoparticles, thereby improving the utility of halloysite and YF₃:Ce³⁺,Tb³⁺ nanoparticles. The research supplies an insight on the development of natural mineral-based luminescent materials, and hopefully it could promote them application in many fields.     

基于Packet Tracer构建计算机网络教学实验平台

近年来本专科院校计算机网络实验室建设速度远远跟不上招生规模的扩大,导致计算机网络实验课程教学与实践脱节。该文以VLAN划分及路由实验为例,演示使用Packet Tracer 5.3构建计算机网络教学实验平台,解决计算机网络实验室或实验设备无法满足实验教学的问题。