Role of the Bridge in Photoinduced Electron Transfer in Porphyrin–Fullerene Dyads

The role of π‐conjugated molecular bridges in through‐space and through‐bond electron transfer is studied by comparing two porphyrin–fullerene donor–acceptor (D–A) dyads. One dyad, ZnP–Ph–C₆₀ (ZnP=zinc porphyrin), incorporates a phenyl bridge between D and A and behaves very similarly to analogous dyads studied previously. The second dyad, ZnP–EDOTV–C₆₀, introduces an additional 3,4‐ethylenedioxythienylvinylene (EDOTV) unit into the conjugated bridge, which increases the distance between D and A, but, at the same time, provides increased electronic communication between them. Two essential outcomes that result from the introduction of the EDOTV unit in the bridge are as follows: 1) faster charge recombination, which indicates enhanced electronic coupling between the charge‐separated and ground electronic states; and 2) the disappearance of the intramolecular exciplex, which mediates photoinduced charge separation in the ZnP–Ph–C₆₀ dyad. The latter can be interpreted as a gradual decrease in electronic coupling between locally excited singlet states of D and A when introducing the EDOTV unit into the D–A bridge.     

波形钢板-UHPC组合桥面板结构截面优化

对实腹式波形顶板-UHPC(超高性能混凝土)组合桥面板进行了改进, 采用空腹式结构建立波形钢板-UHPC组合桥面板有限元模型, 研究UHPC层厚度、波形钢板厚度、波形长度、下缘板宽度和波形高度等截面参数变化对组合桥面板受力特性的影响, 并确定其合理取值范围. 在此基础上, 通过理想点法对参数组合进行优化, 得到合理的参数匹配. 研究结果表明 相较于实腹式组合桥面板, 优化后的组合桥面板自重减小35%, 钢板弯折处应力减小16%; 相较于正交异性钢桥面板, 桥面板用钢量减小7%, 顶板与U肋连接位置应力减小47%.     

沙丘背风侧不同铁路结构形式对风沙环境的适应性分析

当铁路穿越大风沙漠地区时,风沙灾害会对铁路工程及其正常运营产生严重威胁,而设计一种合理的铁路结构形式能够减小风沙沉积对铁路工程的危害. 在本文中,以敦煌至格尔木铁路沙山沟段落为研究对象,采用多相流的方法对越过沙丘的风沙运动过程进行数值模拟,分别讨论了风沙运动对位于沙丘背风坡的铁路路基工程和桥梁工程的影响. 主要的模拟结果显示:路基工程明显降低了风速并且将沙丘后的回流区分成了两部分,而桥梁工程的导流效应则压缩了沙丘背风坡的回流区;轨道间的道碴增大了铁路表面的粗糙度,在轨道间有少量沙粒沉积,而路基工程两侧则有大量积沙;铁路表面的积沙量与摩阻风速呈现出非线性关系,随着摩阻风速的增大,路基工程沙粒沉积的增加速度大于风蚀能力的增加速度,而桥梁工程则正好相反. 在防止风沙危害铁路方面,设置桥梁工程明显优于路基工程. 本研究为风沙运动对铁路工程的影响提供了理论支持,也为今后的铁路工程设计提供了新的思路与研究工具.      

The Effect of Calcium-Silicate Cements on Reparative Dentinogenesis Following Direct Pulp Capping on Animal Models

Dental pulp vitality is a desideratum for preserving the health and functionality of the tooth. In certain clinical situations that lead to pulp exposure, bioactive agents are used in direct pulp-capping procedures to stimulate the dentin-pulp complex and activate reparative dentinogenesis. Hydraulic calcium-silicate cements, derived from Portland cement, can induce the formation of a new dentin bridge at the interface between the biomaterial and the dental pulp. Odontoblasts are molecularly activated, and, if necessary, undifferentiated stem cells in the dental pulp can differentiate into odontoblasts. An extensive review of literature was conducted on MedLine/PubMed database to evaluate the histological outcomes of direct pulp capping with hydraulic calcium-silicate cements performed on animal models. Overall, irrespective of their physico-chemical properties and the molecular mechanisms involved in pulp healing, the effects of cements on tertiary dentin formation and pulp vitality preservation were positive. Histological examinations showed different degrees of dental pulp inflammatory response and complete/incomplete dentin bridge formation during the pulp healing process at different follow-up periods. Calcium silicate materials have the ability to induce reparative dentinogenesis when applied over exposed pulps, with different behaviors, as related to the animal model used, pulpal inflammatory responses, and quality of dentin bridges.     

素养导向的项目教学研究——以盐桥概念为例

以盐桥概念教学为项目,从“桥”的概念出发,根据桥的作用、桥的选择依据以及实际电池中桥的成分与功能设立了3个项目任务;从“盐”的概念出发,根据盐的种类与浓度对原电池电流的影响设立了4个项目任务。通过项目任务,把盐桥概念与实际生活中的电池关联起来,让学生学会运用实验方法解决问题,培养学生将理论知识与实际的工程技术整合的能力,以及跨学科知识整合与模型构建的能力。     

桥连对嵌段共聚物自组装的调控

通过嵌段共聚物自组装形成“桥连”是制备具有优异力学性能的网络结构的有效途经, 具有重要的应用价值. 但是, 过去的研究工作很少讨论“桥连”对嵌段共聚物自组装行为本身的影响. 该研究评论主要总结了最近几年利用“桥连”对嵌段自组装行为进行调控的工作进展. 作者设计了BABCB三组分线性多嵌段共聚物, 当其自组装形成二元“介观晶体”(球、柱)结构时, 中间B嵌段连接A和C相区(嵌段聚集成的“大原子”), 自然地形成桥连; 减小中间桥连B嵌段的相对长度, 就可以增加其拉伸程度, 从而降低介观晶体的配位数; 另外, 两个末端B嵌段的相对长度可以直接调控A和C“大原子”之间的相对配位数. 基于这两个机理, 自洽场理论计算预测了各种配位数相等和不相等的二元介观晶体结构. 进一步, 将“拉伸桥连”概念拓展到AB型嵌段共聚物体系中, 并且通过多臂星型嵌段共聚物分子结构中的“组合构型熵效应”在AB型嵌段共聚物中形成高比率的桥连构型, 使传统的六角柱状结构转变为了四配位的四方柱状和三配位的石墨烯类柱状结构. 未来, 在ABC三组分嵌段共聚物体系的设计中引入拓扑结构以及使用共混等方法, 有望在介观尺度重铸大多数已知的原子/离子二元晶体结构, 甚至超越原子/离子晶体结构.     

供/吸电子基团共轭桥联的双BODIPY衍生物的合成及性能

设计合成了4种对称的以不同供/吸电子基团为共轭桥、两端连接meso位苯或噻吩取代的新型氟化硼二吡咯甲川(BODIPY)衍生物;通过1H NMR,13C NMR和MS等手段对其进行了结构表征;并采用紫外吸收光谱、荧光发射光谱及循环伏安(CV)等方法研究了其光电性能.紫外光谱数据表明,BODIPY结构具有明显的特征吸收,中间的桥联基团无论是强供电子的苯并二噻吩(BDT)还是强吸电子的苯并噻二唑(BT)均不能使整个分子产生明显的分子内电子迁移(ICT).另一方面,meso位的取代基可与BODIPY核产生微弱的ICT,且meso位噻吩取代的分子比meso位苯环取代的分子表现出更强的ICT.紫外光谱数据和电化学测试结果表明,meso位噻吩取代的分子比meso位苯环取代的分子具有更低的氧化电位和更窄的能隙.     

参数灵敏度分析的神经网络方法及其工程应用

在系统分析中，参数灵敏度分析不仅为判断各系统参数的重要性大小提供了依据，量化的灵敏度指标也是后续参数估计的前提。然而，在多效实际系统中，系统参数与系统状态间的显式函数关系不易得到，导致一阶灵敏度指标无法直接求取。简化的单因素分析方法亦存在模型粗糙、精度不高的缺点。本文研究采用人工神经网络的高精度泛化映射，通过少量样本的训练，建立复杂系统中多个系统参数与系统状态间的近似映射关系，继而推导得到统一的灵敏度计算列式。简单结构的神经网络方法和解析方法的对比计算显示了方法的有效性和可靠性。最后，应用该法对某斜拉桥结构的荷载参数和刚度参数进行了考查，得到一般性结论。     

Non-linear interactions in imperfect beams at veering

Non-linear interactions in a hinged-hinged uniform moderately curved beam with a torsional spring at one end are investigated. The two-mode interaction is a one-to-one autoparametric resonance activated in the vicinity of veering of the frequencies of the lowest two modes and results from the non-linear stretching of the beam centerline. The excitation is a base acceleration that is involved in a primary resonance with either the first mode only or with both modes. The ensuing non-linear responses and their stability are studied by computing force- and frequency-response curves via bifurcation analysis tools. Both the sensitivity of the internal resonance detuning—the gap between the veering frequencies—and the linear modal structure are investigated by varying the rise of the beam half-sinusoidal rest configuration and the torsional spring constant. The internal and external resonance detunings are varied accordingly to construct the non-linear system response curves. The beam mixed-mode response is shown to undergo several bifurcations, including Hopf and homoclinic bifurcations, along with the phenomenon of frequency island generation and mode localization.     

斜交连续梁桥数值分析研究

在分析了矩阵位移法和传递矩阵法的理论基础上，将二者组合而成矩阵混合法。矩阵混合法的实质就是将结构物的一端未知向量通过矩阵的简单乘法传递到另一端，再将已知条件代入求解的过程。在矩阵传递的过程中引入位移法中的前进代入的概念，即将未知向量不断地以新的未知向量替换，可以防止误差的传递和积累。将矩阵混合法运用于斜交连续梁桥内力计算，完成了矩阵混合法在斜交连续梁桥内力计算中的理论推导和程序的设计，给出了实际算例并与有限元法进行了比较。