On the Application of Mixed Models of Probability and Convex Set for Time-Variant Reliability Analysis

In time-variant reliability problems,there are a lot of uncertain variables from different sources.Therefore,it is important to consider these uncertainties in engineering.In addition,time-variant reliability problems typically involve a complexmultilevel nested optimization problem,which can result in an enormous amount of computation.To this end,this paper studies the time-variant reliability evaluation of structures with stochastic and bounded uncertainties using a mixed probability and convex set model.In this method,the stochastic process of a limit-state function with mixed uncertain parameters is first discretized and then converted into a timeindependent reliability problem.Further,to solve the double nested optimization problem in hybrid reliability calculation,an efficient iterative scheme is designed in standard uncertainty space to determine the most probable point(MPP).The limit state function is linearized at these points,and an innovative random variable is defined to solve the equivalent static reliability analysis model.The effectiveness of the proposed method is verified by two benchmark numerical examples and a practical engineering problem.

智能时代中小学教师人工智能伦理培养策略研究——基于科尔伯格道德发展理论

人工智能为中小学教育带来无限可能的同时,也引发了一系列的伦理道德风险和挑战。中小学生正处于伦理认知发展的重要阶段,因此,提升中小学教师人工智能伦理对于中小学生、教师自身、学校乃至中小学教育的发展都具有关键作用。但是,现阶段关于中小学教师群体人工智能伦理的研究相对较少且缺乏明确的理论指导。在综述中小学教师面临的人工智能伦理挑战的基础上,基于科尔伯格三水平六阶段伦理发展框架,有针对性地提出不同阶段中小学教师人工智能伦理的培养策略。这些伦理培养策略由低水平到高水平、初级阶段到高级阶段演进,包括培养中小学教师人工智能伦理意识、推动中小学教师自身建构人工智能伦理知识、发展中小学教师社会化协同构建、构建中小学教师人工智能伦理外部约束机制、构建民主化的人工智能伦理决策机制、培养中小学教师共同体的人工智能伦理责任。

Genetic analysis and QTL mapping of stalk cell wall components and digestibility in maize recombinant inbred lines from B73 × By804

The cell wall composition and structure of the maize stalk directly affects its digestibility and in turn its feed value.Previous studies of stem quality have focused mostly on common maize germplasm,and few studies have focused on high-oil cultivars with high grain and straw quality.Investigation of the genetic basis of cell wall composition and digestibility of maize stalk using high-oil maize is desirable for improving maize forage quality.In the present study,a high-oil inbred line(By804)was crossed as male parent with the maize inbred line B73 to construct a population of 188 recombinant inbred lines(RILs).The phenotypes of six cell-wall-related traits were recorded,and QTL analysis was performed with a genetic map constructed with SNP markers.All traits were significantly correlated with one another and showed high broad-sense heritability.Of 20 QTLs mapped,the QTL associated with each trait explained 10.0%–41.1%of phenotypic variation.Approximately half of the QTL each explained over 10%of the phenotypic variation.These results provide a theoretical basis for improving maize forage quality by marker-assisted selection.

Nonlinear oscillation characteristics of magnetic microbubbles under acoustic and magnetic fields

Microbubbles loaded with magnetic nanoparticles(MMBs) have attracted increasing interests in multimode imaging and drug/gene delivery and targeted therapy. However, the dynamic behaviors generated in diagnostic and therapeutic applications are not clear. In the present work, a novel theoretical model of a single MMB was developed, and the dynamic responses in an infinite viscous fluid were investigated under simultaneous exposure to magnetic and acoustic fields. The results showed that the amplitude reduces and the resonant frequency increases with the strength of the applied steady magnetic field and the susceptibility of the magnetic shell. However, the magnetic field has a limited influence on the oscillating. It is also noticed that the responses of MMB to a time-varying magnetic field is different from a steady magnetic field. The subharmonic components increase firstly and then decrease with the frequency of the magnetic field and the enhanced effect is related to the acoustic driving frequency. It is indicated that there may be a coupling interaction effect between the acoustic and magnetic fields.

Osiers-sprout-like heteroatom-doped carbon nanofibers as ultrastable anodes for lithium/sodium ion storage

We report an in situ carbothermic reduction process to prepare osiers-sprout-like heteroatom-doped carbon nanofibers. The dosage of copper salts and a unique annealing process have a crucial effect on the development of this unique carbon structure. A systematic analysis is performed to elucidate the possible mechanism of synthesis of the carbon nanofibers decorated with carbon bubbles. As anodes for rechargeable lithium/sodium ion batteries, the heteroatom-doped nanofibers exhibit high reversible capacities and satisfactory long-term cycling stabilities. The osiers-sprout-like heteroatom-doped carbon nanofiber electrodes deliver an ultrastable cycling performance with reversible capacities of 480 and 160 mAh·g^-1 for lithium-ion and sodium-ion batteries after 900 cycles at a current density of 800 mA·g^-1, respectively.