Simulation study on cooperation behaviors and crowd dynamics in pedestrian evacuation

Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton(CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.     

气相色谱法测定饮用水中碘代消毒副产物碘代三卤甲烷的研究

对比研究了吹扫捕集/气相色谱-质谱法(PT/GC-MS)和液液萃取-气相色谱/电子捕获检测器(LLE-GC/ECD)检测饮用水中碘代三卤甲烷(I-THMs)的分析方法。结果表明,采用甲基叔丁基醚(MTBE)作为萃取剂直接液液萃取,LLE-GC/ECD检测更适于I-THMs的分析。在选定条件下,内标法定量,6种ITHMs在0.5~1 000μg/L范围内线性关系良好,相关系数均大于0.99,相对标准偏差(RSD,n=7)为3.9%~6.4%,方法检出限为0.05~0.11μg/L。0.5,2.0,10.0μg/L加标水平下,分别对某地表水、水厂滤后水和自来水进行I-THMs的加标回收实验,平均回收率为81.2%~108.6%,RSD为2.6%~7.7%。结果表明,该方法简便、快速、灵敏,适用于饮用水中新兴消毒副产物I-THMs的检测。     

硝酸根接枝诱导组装金红石相TiO2纳米束以增强光催化产氢（英文）

化石燃料的快速消耗加速了全球能源危机和环境污染等问题.光催化产氢直接利用清洁和可持续的太阳能实现向化学燃料的转化,因而成为一种有前景的技术.众多半导体光催化剂中,二氧化钛因其高光催化活性、稳定的化学性质、低成本和无毒等优势而被广泛用作分解水产氢的光催化剂.最近,金红石相TiO2纳米晶体在某些情况下被证明具有光催化的潜力,然而其光生电子-空穴对的快速复合显著抑制了光催化效率.表面修饰、构建异质结和负载助催化剂等策略被用来提高光生载流子的分离效率以减少复合损失,从而提升光催化活性.由于光催化反应通常发生在光催化剂的表面活性位点上,因此通过改善表面性质改变电荷转移途径对光催化活性具有重要影响.磷酸、硫酸、硼酸和盐酸等无机酸的修饰可以改变光催化剂的表面基团,分别通过促进表面羟基的形成和氧气的吸附以及改变表面电荷性质更有效地捕获空穴,实现光生电子和空穴的分离,有助于光催化降解有机污染物.然而,这种影响机制显然不适用于光催化产氢体系,目前对无机酸修饰用于分解水产氢的研究鲜有报道.因此,通过酸改性策略制备高效产氢的光催化剂仍然是一个相当大的挑战.本文利用硝酸诱导策略合成纺锤状金红石相二氧化钛纳米束(R-TiO2).首先,制备层状质子化钛酸盐(LPT)作为TiO2的前体,随后,加入浓硝酸以诱导向金红石相TiO2的转变,并组装形成纺锤状纳米束.对照实验显示,硝酸的酸化可以诱导LPT向金红石相TiO2的转变,而相同条件下浓硝酸后处理不会引起晶相的转变.纺锤形纳米束的形成源于,硝酸诱导R-TiO2沿(110)方向生长并彼此粘附,硝酸诱导组装过程成功在TiO2表面修饰上硝酸根,同时扩大了光吸收范围,有效减少了电荷复合损失.光催化产氢测试证明了R-TiO2光催化剂具有高效的产氢性能,产氢速率为402.4μmol h-1,是Degussa P25的3.1倍,并且显著高于未经浓硝酸处理的锐钛矿(52.0μmol h^-1)或金红石相(110.8μmol h^-1)光催化剂.为了说明表面硝酸根的影响,分别从晶体和化学结构、形态以及表面电荷性质方面比较了光催化反应前后的变化,结果表明,R-TiO2增强的光催化效率可归因于硝酸根基团的负场效应,有利于在表面上捕获带正电的质子以促进载流子分离,提高光催化产氢的效率.总之,本工作不仅对于发展表面修饰策略制备高效产氢光催化剂的研究具有重要意义,而且提出了一种不同于文献报道的无机酸影响机制.     

Electronic and optical properties of 3N-doped graphdiyne/MoS2 heterostructures tuned by biaxial strain and external electric field

The construction of van der Waals (vdW) heterostructures by stacking different two-dimensional layered materials have been recognised as an effective strategy to obtain the desired properties. The 3N-doped graphdiyne (N-GY) has been successfully synthesized in the laboratory. It could be assembled into a supercapacitor and can be used for tensile energy storage. However, the flat band and wide forbidden bands could hinder its application of N-GY layer in optoelectronic and nanoelectronic devices. In order to extend the application of N-GY layer in electronic devices, MoS₂ was selected to construct an N-GY/MoS₂ heterostructure due to its good electronic and optical properties. The N-GY/MoS₂ heterostructure has an optical absorption range from the visible to ultraviolet with a absorption coefficient of 10⁵ cm^-1. The N-GY/MoS₂ heterostructure exhibits a type-Ⅱ band alignment allows the electron-hole to be located on N-GY and MoS₂ respectively, which can further reduce the electron-hole complexation to increase exciton lifetime. The power conversion efficiency of N-GY/MoS₂ heterostructure is up to 17.77%, indicating it is a promising candidate material for solar cells. In addition, the external electric field and biaxial strain could effectively tune the electronic structure. Our results provide a theoretical support for the design and application of N-GY/MoS₂ vdW heterostructures in semiconductor sensors and photovoltaic devices.     

全固态单纵模脉冲Nd:YVO_4环形激光器

设计并研制了全固态调Q脉冲单纵模Nd:YVO4环形激光器。利用880nm激光二极管端面抽运Nd:YVO4晶体,通过四镜环形谐振腔中插入声光调Q晶体、标准具,并优化激光谐振腔的结构,获得了重复频率为200Hz、脉宽为26.6ns的单纵模脉冲1.064μm激光输出。当泵浦功率为15 W时,单纵模激光输出的单脉冲能量为570μJ、脉冲能量稳定性优于3%。     

N掺杂对α-石墨炔表面吸附H_2O,H,O和OH的电子性质和磁性的影响

石墨炔是一种新型的二维(2D)碳的同素异形体,炔键单元的高活性使其在小分子吸附方面相比石墨烯更具优势.本文基于密度泛函理论(DFT),研究了H_2O和H、O及OH分别在原始的和掺杂了N原子的α-石墨炔上的相互作用.研究结果表明,N掺杂和小分子吸附能够改变α-石墨炔的电子结构和磁性. N原子掺杂后α-石墨炔对小分子的吸附能力明显增强. H、O原子和OH吸附在N原子掺杂体系前后表现出明显的磁性差异:H原子和OH吸附在纯净的α-石墨炔上体系显示磁性,N原子掺杂后,磁性消失;而O原子则是吸附在纯净的α-石墨炔上未表现出磁性,N原子掺杂后,体系出现磁性.此外,α-石墨炔对水分子的吸附作用较弱,受范德瓦耳斯作用影响较大,属于物理吸附.本研究将为α-石墨炔中N杂质检测以及α-石墨炔基气体传感器的设计研究提供新的思路.     

连续变量1.34 μm量子纠缠态光场的实验制备

设计研制了连续单频671 nm/1342 nm双波长激光器,并通过模式清洁器降低了激光器额外噪声.利用该低噪声连续单频激光器抽运由Ⅱ类准相位匹配晶体构成的双共振非简并光学参量放大器,实验制备出纠缠度达3 dB的光通信波段1.34μm连续变量量子纠缠态光场.该波段量子纠缠态光场在光纤中传输损耗低且相散效应小,与现有的光纤通信系统相兼容,可用于实现基于光纤的实用化连续变量量子通信.     

Ge@C82结构及性质的理论研究

采用密度泛函理论方法,对Ge@C82的结构及性质进行计算研究.结果表明,由于包合Ge,C82碳笼平均键长增长,碳笼增大,而且Ge原子略微偏离碳笼中心.三重态的C2Ge@C82为能量最低结构.自然布居分析表明,C2C82与Ge之间未发生电子转移,可以用C2Ge@C82来表示它的结构.C2C82和C2Ge@C82的红外光谱计算结果显示,二者的主要区别为C2Ge@C82在1100～1200 cm-1区间的吸收峰变得更尖锐.     

双集中荷载下一次超静定梁的加载过程分析

对双集中荷载作用下一次超静定梁的弹塑性加载全过程进行了分析．根据变形特点可把加载过程分成四个阶段．第一阶段是常规的弹性阶段,第二阶段是固支端附近单个塑性变形区扩展的阶段,第三阶段是固支端和一个集中荷载附近两个塑性变形区同时扩展的阶段,第四阶段是固支端保持为塑性铰从而引起固支端附近区域卸载而梁中间的塑性变形区继续扩展直至形成第二个塑性铰的阶段．在第一阶段,弯矩内力和挠度与外荷载均是线性比例递增关系;在第二、第三两个阶段,弯矩和挠度与外荷载是不同的非线性关系;在第四阶段,弯矩与外荷载是非比例的线性关系,但挠度与外荷载却是复杂的非线性关系．给出了加载各阶段的弯矩及挠度计算公式,具有理论意义,也可供对应的结构设计应用．     

Au_n团簇催化水煤气变换反应机理的密度泛函理论研究

利用密度泛函理论(DFT)研究了Au10、Au13和Au20三类团簇的稳定性和对水煤气变换(WGSR)反应的催化活性,考察了各物质在Aun团簇上的吸附行为和微观反应机理。结果表明,三类Aun团簇的稳定性顺序为Au10Au13Au20,而Aun团簇中电子离域性及吸附能力大小趋势为Au13Au10Au20。在三类Aun团簇上,水煤气变换反应的控速步骤均为H2O的解离,但其反应机理路径有所不同。Au10团簇上为羧基机理,COOH*中间体直接解离;Au13团簇上为氧化还原机理,两个OH*发生歧化反应;Au20团簇上为羧基机理,COOH*和OH*发生歧化反应。通过对三类团簇上的最佳反应路径进行比较发现,Au13团簇在低温下具有较好的催化活性。