A new heuristics model of simulating pedestrian dynamics based on Voronoi diagram

A new heuristics model based on the Voronoi diagram is presented to simulate pedestrian dynamics with the noncrowded state, in which these mechanisms of preference demand evading and surpassing, microscopic anti-deadlock, and site-fine-tuning are considered. The preference demand describes the willingness determination of detouring or following other pedestrians. In the evading and surpassing mechanisms, in order to achieve a balance between avoiding conflicts and minimizing detour distances, a new pair of concepts: "allow-areas and denial-areas" are introduced to divide the feasible region for pedestrians detour behaviors, in which the direction and magnitude of detour velocity are determined.A microscopic anti-deadlock mechanism is inserted to avoid deadlock problem of the counter-directional pedestrian. A site-fine-tuning mechanism is introduced to describe the behavior of avoiding getting too close to the neighbors in pedestrian movement. The presented model is verified through multiple scenarios, including the uni-or bi-direction pedestrian flow in the corridor without obstacles, the uni-direction pedestrian flow in the corridor with obstacles, and the pedestrian evacuation from a room with single-exit. The simulation results show that the velocity–density relationship is consistent with empirical data. Some self-organizing phenomena, such as lanes formation and arching are observed in the simulation.When pedestrians detour an obstacle, the avoiding area before the obstacle and the unoccupied area after the obstacle can be observed. When pedestrians evacuate through a bottleneck without panic, the fan-shaped crowd can be found, which is consistent with the actual observation. It is also found that the behavior of following others in an orderly manner is more conducive to the improvement of the overall movement efficiency when the crowd moves in a limited space.     

串联超导单元失超特性改善方法的仿真研究(英文)

为承受高电压与高电流等级,电阻型超导限流器的各个无感超导单元间不可避免地要进行串并联,由此会带来单元间失超不同步的问题.本文以单根344S超导带材在100ms的故障时间内,带材温度由92K升至300K时,失超电阻随温度的变化为基础,对两者间的关系进行了拟合.之后,以拟合函数为核心,利用Simulink的库中元件构建了单位长度344S带材的失超电阻模型并将其封装为模块.最后,搭建仿真电路模拟了故障时间内两个串联失超模块不同步失超的过程,仿真了分流电阻对失超不同步的改善并对分流电阻的选取进行了优化分析.结论证实,较小阻值的分流电阻更有利于改善失超特性.     

ZIF-8@Fe_3O_4磁性固相萃取结合高效液相色谱法测定果汁中3种苯甲酰脲杀虫剂

发展了磁性沸石咪唑酯骨架材料(ZIF-8@Fe_3O_4)磁性固相萃取结合高效液相色谱-二极管阵列检测器,测定果汁中氟幼脲、四螨嗪和氟啶脲3种苯甲酰脲杀虫剂(BUs)的新方法。利用X射线衍射仪、傅立叶变换红外光谱仪、扫描电子显微镜和振动样品磁强计对合成的ZIF-8@Fe_3O_4吸附剂进行表征,考察了溶液pH值、吸附剂用量、吸附时间、洗脱溶剂种类和体积(单次洗脱体积×洗脱次数)对BUs萃取效率的影响。在最优实验条件下,氟幼脲和四螨嗪在2.0～200 ng/mL、氟啶脲在3.5～350 ng/mL范围内线性关系良好(相关系数r=0.999),检出限(S/N=3)和定量下限(S/N=10)分别为0.6～1.0 ng/mL和2.0～3.5 ng/mL。3个加标水平下的回收率为82.7%～98.6%,日内和日间(n=3)相对标准偏差(RSD)分别为1.2%～6.1%和1.3%～9.0%。当上样体积为10 mL时,ZIF-8@Fe_3O_4对果汁中3种BUs的富集倍数为43.4～48.1倍,吸附剂重复使用10次后,3种BUs回收率的RSD不大于8.8%。该方法灵敏、高效,可用于果汁样品中BUs的分析。     

步行通道内行人流拉链现象的生成机理与仿真研究

以步行通道内的单向行人流为研究对象,分析研究行人拉链现象的生成机理,并建立基于Voronoi图的速度修正模型对其仿真研究.首先,从行人追求视野最佳和步行舒适的角度分析拉链现象的生成机理,以行人的视野关注和视野遮挡描述影响行人移动过程中产生拉链偏移的因素;以行人局部密度描述行人的步行舒适度;引入拉链敏感系数描述行人客观偏移的意愿程度;提出单个行人侧向偏移的机制,获得行人最佳的偏移位置.然后,构建基于Voronoi图的行人速度修正仿真模型,考虑行人是否有偏移倾向的主观意愿,并嵌入偏移规则,模拟再现行人的拉链现象.仿真发现:行人的拉链层数与通道宽度成正比,该模型速度密度关系图与实证数据吻合较好;与不考虑拉链效应相比,倾向主动进行侧向偏移的行人占比越大,越有助于提高通道内行人的移动速度、舒适度和空间利用率.     

光谱法研究夜蓝与牛血清白蛋白的相互作用

研究了有机染料夜蓝(NB)与牛血清白蛋白(BSA)相互作用后的荧光光谱特性。结果表明:NB对BSA的荧光产生了有规律的猝灭,并且猝灭类型属于静态猝灭;得到了二者相互作用后的结合常数和结合位点数,结合位点数大约为1,说明二者为1:1结合;经计算得到了二者反应的热力学参数,通过判断得NB与BSA之间主要靠静电和疏水作用力相结合;同步荧光光谱显示了NB更接近与BSA的色氨酸残基结合;又按照Forster非辐射能量转移的理论,得到了授体(BSA)-受体(NB)的能量转移效率和结合距离,分别为0.270和2.75 nm,说明二者之间发生了非辐射能量转移。     

荧光素衍生物水杨醛荧光素腙的合成及对铜(Ⅱ)离子的检测

以荧光素酰肼与5-溴水杨醛反应合成了一种新型荧光素衍生物5-溴水杨醛荧光素腙(BSFH),采用红外、核磁、质谱、元素分析等技术手段对其进行了表征。 通过吸收光谱考察了在水溶液中BSFH对常见金属离子的选择性响应,发现BSFH在可见光区几乎无吸收,当加入常见金属离子时,吸收光谱上除了Cu²⁺之外的其它金属离子在496 nm处出现非常弱的吸收,而当Cu²⁺存在时,可以裸眼看到溶液颜色迅速从无色变为黄色,吸收光谱上在496 nm处出现了相对很强的吸收峰,并且随着Cu²⁺浓度的增加溶液的吸收强度不断增强,说明在水溶液中BSFH对Cu²⁺有很好的选择性。 实验结果表明,该化合物与Cu²⁺的化学计量比为1:1,Cu²⁺浓度线性范围为0.30~10 μmol/L,许多常见的金属离子不干扰Cu²⁺的测定,检测限为0.30 μmol/L,说明在水溶液中BSFH对铜离子具有很高的灵敏度。 据此,BSFH可以简单、快速、灵敏地在水溶液中识别和检测低浓度的铜离子。