大学生研究性教学实践——以芳香烃核磁共振的理论计算为例

为提高本科生自主学习和探究性学习的能力,指导学生开展了芳香烃体系核磁共振的理论计算研究。在问题引出、文献调研总结、体系建模及模拟、结果分析讨论等研究性教学实践中,学生不仅深入认识了取代基、分子结构、存在状态对化学位移和自旋耦合常数的影响,增进了对微观结构及宏观性质关系的认识,也提高了自主学习、知识应用和解决问题的能力。此外,这种教学活动还提升了学生深入挖掘、不断求证的探究精神和科研素养,有助于创新型人才的培养。

Structural Evolution of D5h(1)-C90 under High Pressure:A Mediate Allotrope of Nanocarbon from Zero-Dimensional Fullerene to One-Dimensional Nanotube

The hybridization of fullerene and nanotube structures in newly isolated C;with the D;symmetric group(D;(1)-C;)provides an ideal model as a mediating allotrope of nanocarbon from zero-dimensional(OD)fullerene to one-dimensional nanotube.Raman and infrared spectroscopy combined with classical molecular dynamics simulation were used to investigate the structural evolution of D;(1)-C;at ambient and high pressure up to35.1 GPa.Interestingly,the high-pressure transformations of D;(1)-C;exhibit the features of both fullerene and nanotube.At around 2.5 GPa,the D;(1)-C;molecule in the crystal undergoes an orientational transition to a restricted rotation.At 6.6 GPa,the tubular hexagonal part occurs and transforms into a dumbbell-like structure at higher pressure.The material starts to amorphize above 13.9 GPa,and the transition is reversible until the pressure exceeds 25 GPa.The amorphization is probably correlated with both the intermolecular bonding and the morphology change.Our results enrich our understanding of structural changes in nano carbon from 0 D to1 D.

发达国家农村金融发展的经验与启示

我国是一个农业大国,农业经济的发展关系到整个国民经济的发展。农业生产过程中存在很多风险。金融服务可以有效改善农业生产的经济不稳定性,降低农业生产中的风险,保障农民收入,从而实现乡村振兴。发达国家由于政府拥有有效的政治干预能力以及财政扶持能力,同时发达国家组织结构层级分明,基层之间遵循属地原则的特性,各国逐渐形成了具有自己特色的金融体系。本文从信贷、保险、金融体系构建等多方面对发达国家的农村金融体系进行探讨,这将对我国农村金融的发展具有启示作用。

Low-power soft transistors triggering revolutionary electronics

Transistors have been reshaping our lives since their initial appearance in the 1940s.As the central element of logic gates and integrated circuits(chips),they undoubtedly play an incomparable role in promoting the development of computers,smartphones,flat panel displays,Internet of Things,and even all electronic or electrical systems.The past decades have witnessed dominant transistors usually made from inorganic semiconductors such as silicon materials and metal oxides,which are advantageous to achieve high mobility,fast switching speed,and excellent stability.Thus,silicon transistors and metal oxide semiconductor field-effect transistors have been broadly used for electronic applications.However,these transistors are rigid and nearly approaching the fundamental limits on speed and power consumption,despite being manufactured at a much smaller scale to meet the projection of Moore’s law.As future transistors with mechanical flexibility/robustness and low-power consumption are demanded,innovation in functional materials,device configurations,and integrated processing techniques to facilitate the evolution from rigid devices to soft,durable,and biocompatible devices is imperative.

Comparisons on methods for identifying accident black spots using vehicle kinetic parameters collected from road experiments

Identification of accident black spots has gained tremendous popularity among road agencies and safety specialists for evaluating and subsequently enhancing road traffic safety.However,there is still limited understanding of the internal relationship between black spots and microscopic vehicle kinetic parameters.To address this gap,this paper describes a project that was undertaken using the real-time tire force data(kinetic response)obtained from road experiments on Wenli Expressway.First,factor analysis was applied to extracted three independent indicators(power-braking,handling stability,and ride comfort)from seven original kinetic indicators with multiple collinearities.Afterward,the main indicators were given vehicle kinetic meaning by analyzing the characteristics of original indicators associated with them.A compelling correlation was established among kinetic parameters,vehicle running qualities,and accident risk.Additionally,an integrated evaluation framework was established to identify accident black spots based on applying ordered logit models and PLS-entropy-TOPSIS approaches.The recognition results exhibited that the overall recognition accuracy obtained by the latter was found to be comparable to that achieved using the previous one.The compound evaluation model proposed in this paper has been proven to present many advantages for black spot identification.It is evidently clear from the findings that the vehicle kinetic parameters have significant correlations with road accident risk.This paper could provide some insightful knowledge for identifying and preventing the black spots from ameliorating traffic safety.

Single-cell transcriptomics of immune cells in lymph nodes reveals their composition and alterations in functional dynamics during the early stages of bubonic plague

Bubonic plague caused by Yersinia pestis is highly infectious and often fatal.Characterization of the host immune response and its subsequent suppression by Y.pestis is critical to understanding the pathogenesis of Y.pestis.Here,we utilized single-cell RNA sequencing to systematically profile the transcriptomes of immune cells in draining lymph nodes(d LNs)during the early stage of Y.pestis infection.Dendritic cells responded to Y.pestis within 2 h post-infection(hpi),followed by the activation of macrophages/monocytes(Mφs/Mons)and recruitment of polymorphonuclear neutrophils(PMNs)to d LNs at 24 hpi.Analysis of cell-to-cell communication suggests that PMNs may be recruited to lymph nodes following the secretion of CCL9 by Mφs/Mons stimulated through CCR1-CCL9 interaction.Significant functional suppression of all the three innate immune cell types occurred during the early stage of infection.In summary,we present a dynamic immune landscape,at single-cell resolution,of murine d LNs involved in the response to Y.pestis infection,which may facilitate the understanding of the plague pathogenesis of during the early stage of infection.

An MPC-based manoeuvre stability controller for full drive-by-wire vehicles

Aiming at the actuator time delay caused by the drive-by-wire technology,a novel manoeuvre stability controller based on model predictive control is proposed for full drive-by-wire vehicles.Firstly,the future vehicle dynamics are predicted by a twodegree-of-freedom vehicle model with input delay.Secondly,in order to prevent the vehicle from destabilizing due to excessive side slip angles,the determined ideal yaw rate and side slip angle are tracked simultaneously by optimizing the front wheel angle and additional yaw moment.Moreover,in order to improve the trajectory tracking ability,a side slip angle constraint determined by phase plane stability boundaries is added to the cost function.The results of Matlab and veDYNA co-simulation show that the regulated yaw rate can track the reference value well and the side slip angle decreases.Meanwhile,the trajectory tracking ability is improved obviously by compensating the time delay.

基于薄绝缘层和强电子受体的协同效应实现近似欧姆接触的高效空穴注入策略

有效的电荷注入是发展低电压、高效率有机发光二极管(OLEDs)的关键.然而,目前应用最广泛的空穴注入材料(HATCN)的注入效率仅约10%,无法满足高清显示和照明的需要.因此,我们基于薄绝缘层(特氟龙(Teflon))和强电子受体(HATCN)的协同效应设计了一种高效、通用的空穴注入技术.研究表明特氟龙诱导形成的纳米岛状结构有助于增强界面电场局域化,搭配HATCN可以实现高效的电荷产生和空穴注入.新型的注入层(Teflon/HATCN)可实现近似欧姆接触的高效空穴注入,其注入效率高达80%以上.基于该方法制备的红色磷光OLED的启亮电压仅为2.4 V,最大外量子效率高达33.1%.本文关于薄绝缘层和强电子受体的协同效应的研究为发展高性能电荷注入材料提供了新策略.

Effect of ligand initial conformation and counteranion on complexation behaviors of R-BTBP toward Pd(Ⅱ)contained in highly active liquid waste

Soft N-donor bis-triazin bipyridines derives(R-BTBP)are a type of very promising extratant for extraction and complexation with long-lived trivalent minor actinides over lanthanides from highly active liquid waste(HLW).In addition to minor actinides,R-BTBP also holds very strong complexation ability toward fission palladium.However,few studies have been focused on the separation and complexation with the fission product Pd(Ⅱ)by R-BTBP.Herein,the complexation behaviors of Pd(Ⅱ)with four typical R-BTBP ligands were systematically studied by single crystal X-ray diffraction,1H NMR titration and theoretical calculation.The effects of R-BTBP initial conformation and nitrate anions on the complexation behaviors of R-BTBP with Pd(Ⅱ)were thoughtfully analyzed.Both the 1:1 and 2:1 binuclear complexes could be formed between Pd(Ⅱ)and R-BTBP with initialⅡconformation in the presence of nitrate anions,while only one 1:1 type Pd(Ⅱ)complex could be formed for those with initial OO conformation.Without nitrate anion,only one 1:1 type complex was formed in solution.The structure of the 1:1 Pd(Ⅱ)/R-BTBP complex was firstly characterized by single crystal crystallography.DFT calculation results showed that a significant large rotational energy barrier(21.8~22.6 kcal/mol)must be overcome to form theⅡtype 2:1Pd(Ⅱ)complex for those OO type R-BTBP ligands,however which would not prevent them from forming the 1:1 type complex.

Incorporating element doping and quantum dot embedding effects to enhance the thermoelectric properties of higher manganese silicides

Element doping and nano-inclusion embedding are effective approaches to enhance the electrical conductivities and decrease the lattice thermal conductivities of thermoelectric(TE)materials,respectively.However,the intrinsic low electrical thermal conductivities and high electrical properties are severely sacrificed,and the final figure of merit(ZT)is usually restricted.In this study,Ag doping and Pt quantum dot(QD)embedding were synchronously achieved via embedding Ag/Pt alloy QDs into the higher manganese silicides to avoid the conventional single-element doping strategy.The power factor(at 823 K)was enhanced from 1.57×10^(-3) W m^(-1) K^(-2) to 1.82×10^(-3) W m^(-1) K^(-2)(-16%)due to the-18%increase in carrier concentration that was derived from the Ag doping effect.Simultaneously,the lattice thermal conductivity(at 823 K)decreased from 2.65 W m^(-1) K^(-1) e1.92 W m^(-1) K^(-1)(-28%)because of the broadband phonon scattering effect that resulted from the residual Pt QDs inclusions.Synthetically,the optimal ZT value increased by-52%from 0.42 to 0.64 at 823 K.This study demonstrated that incorporating metastable alloy QDs to obtain element doping and nano-inclusion embedding effects is a novel and feasible means to enhance the ZT value of HMS.This method is also possibly applicable to other alloy QD/TE composites.

Charge transport behavior in gamma‐ray irradiated poly(ethylene terephthalate)estimated by surface potential decay

This study reports on the variation in charge transport behaviour of poly(ethylene terephthalate)(PET)caused by gamma‐ray irradiation estimated by means of surface potential decay(SPD)measurement.The 100μm‐thick PET specimens were exposed to 60Co gamma rays to a maximum total dose of 1000 kGy.The SPD test was carried out to obtain charge transport related parameters via various models,and the effect of gamma‐ray on the transport behaviour was examined.Furthermore,Fourier trans-form infrared spectrum,gel content,ultraviolet‐visible spectroscopy,X‐ray photo-electron spectroscopy,differential scanning calorimetry and polarized optical microscope were employed to characterize the change in material structure induced by the irradiation.The test results indicated that with the growth in the total dose,the deep trap centre was basically unchanged,whereas the shallow trap centre became shallower.In addition,the trap density tended to decrease.The carrier mobility in PET increased with the total dose,and the charge transport manner conformed well to the hopping model.It is suggested that the formation of oxygen‐based groups from the irradiation induced oxidation reaction tends to encourage the charge transport,while the decrease of amorphous region gives rise to the reduction in trap density.

Suppressing Competitive Coordination Reaction for Ohmic Cathode Contact Using Amino-Substituted Organic Ligands and Air-Stable Metals

Ohmic cathode contact can be formed readily via coordination-activated n-doping(CAN),by co-evaporating air-stable metals(e.g.,silver)and organic ligands with coordination sites.It has been proposed that increasing the nucleophilicity of the main binding site of a ligand is essential for reducing the work function of the doped films.

A Solution-Processed n-Type Conducting Polymer Without Side Chains Formed via Nonmetal-Participated Polymerization and in Situ n-Doping

Solution-processed conducting polymers(CPs)are emerging as promising multifunctional materials and are motivating the development of several electronic applications.However,there are fewer highperformance electron conduction-dominated n-type CPs than p-types.Thus,the exploration of other material designs and synthesis methods is required.Accordingly,we developed a facile metal catalystfree method by combining polymerization and in situ n-doping to produce an n-type conducting polymer,poly(benzodithiophenedione)(PBTDO).The doping procedure enabled interaction between the charged conjugated backbones and solvent,dimethyl sulfoxide,making the doped conducting polymer soluble without the assistance of side chains or surfactants.PBTDO exhibited an extremely low-lying reduction level,moderate conductivity,and good air stability with potential applications in n-type organic thermoelectric devices.Moreover,it was found that the in situ doping efficiency in the reaction was highly dependent on the energy level and backbone planarity.Doping cannot occur for polymers with a high lowest unoccupied molecular orbital level and distorted conjugated chains prevent a high doping efficiency from being obtained.This study gains deeper insight into the n-doping mechanisms of conjugated polymers,with guidance for the design of highperformance n-type CPs.