Survey study and experimental investigation on the local behavior of pedestrian groups

Current research on pedestrian dynamics mainly focuses on the interactions among isolated individuals, the impact of the presence of groups is not fully considered. In recent 5 years, researchers have started to investigate pedestrian group movement. The aim of this work is to explore the local behavior of pedestrian groups by questionnaires and field observation. Survey study focused on pedestrians' psychology when walking in groups, which included five parts: group size, interpersonal distance, spatial relationship among group members, speed adjustment of group members, information transmission, and acid action among group members. Meantime a field observation was carried out to study group movement characteristics, which contained speed, step frequency, offset angle and interpersonal distance. The survey results show that group members have a closer interpersonal distance, faster information transmission and plenty of acid action. Conversely, group walking has a negative influence on pedestrian's speed, step frequency by comparing with the way isolated pedestrian walks. In addition, it is found that for a certain group, the group members are able to keep movement consistent. Also there exists obvious movement diversity among different group types (male dyads, female dyads, couple groups, and ordinary‐friend groups) because of different gender and social relationship. Ultimately the results will be more promising for helping to model the movement of pedestrian groups. © 2014 Wiley Periodicals, Inc. Complexity 20: 87–97, 2015     

台湾地区高校基础物理教育见闻和一些感想

值台湾地区2015年物理学年会之际,应新竹清华大学邀请,作者一行4人于2015年1月27日至2015年2月5日赴新竹清华大学观摩物理学年会教育分会,并参观考察了台北东吴大学、新竹清华大学、新竹交通大学、高雄中山大学、台中中兴大学和桃园中央大学等校的物理系物理基础教育的情况.文章就10天来的所见所闻以及对有关问题的深入交流介绍给读者,并谈一下自己的感想,谨供同仁参考.     

液体表面张力系数的实验研究

改变液体的浓度可以调控液体的表面张力系数,各种形状膜架的挂膜时间与液体表面张力系数存在着一定的关系,本文对于这两个方面进行了实验研究,得出了相应的结果.此外,溶液的温度和空气的流动对挂膜时间都会产生影响.     

Characterization of Cr‐doped Sb2Te3 films and their application to phase‐change memory

Phase‐change memory (PCM) is regarded as one of the most promising candidates for the next‐generation nonvolatile memory. Its storage medium, phase‐change material, has attracted continuous exploration. Along the traditional GeTe–Sb₂Te₃ tie line, the binary compound Sb₂Te₃ is a high‐speed phase‐change material matrix. However, the low crystallization temperature prevents its practical application in PCM. Here, Cr is doped into Sb₂Te₃, called Cr–Sb₂Te₃ (CST), to improve the thermal stability. We find that, with increase of the Cr concentration, grains are obviously refined. However, all the CST films exhibit a single hexagonal phase as Sb₂Te₃ without phase separation. Also, the Cr helps to inhibit oxidation of Sb atoms. For the selected film CST_10.5, the resistance ratio between amorphous and crystalline states is more than two orders of magnitude; the temperature for 10‐year data retention is 120.8 °C, which indicates better thermal stability than GST and pure Sb₂Te₃. PCM cells based on CST_10.5 present small threshold current/voltage (4 μA/0.67 V). In addition, the cell can be operated by a low SET/RESET voltage pulse (1.1 V/2.4 V) with 50 ns width. Thus, Cr–Sb₂Te₃ with suitable composition is a promising novel phase‐change material used for PCM with high speed and good thermal stability performances. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

带空间机械臂航天器姿态运动规划的数值算法研究

自由漂浮空间机械臂系统在无外力矩作用时,系统的动量矩守恒而成为非完整系统。利用这一特性本文研究了自由漂浮空间机械臂系统的三维姿态运动规划问题。导出带空间机械臂的航天器三维姿态运动数学模型,将系统的非完整运动规划问题转化为非线性系统最优控制问题,在最优控制中利用小波逼近控制输入规律,提出基于遗传算法的最优控制数值算法。通过数值仿真,表明该方法对带空间机械臂航天器系统的非完整姿态运动规划是有效的。     

Half-metallicity modulation of zigzag BC2N nanoribbons by transverse electric fields: A first principles study

We performed density functional theory calculations to investigate the electronic and magnetic properties of H-terminated zigzag BC₂N nanoribbons (ZBC₂NNRs) with the atoms arranged as B-C-N-C along zigzag lines. The ribbons can be classified into three groups according to the profiles of band structures and edge atoms: BN-BN, CC-CC and BN-CC. Among them, CC-CC and BN-CC ZBC₂NNRs behave magnetic ground states. The results show that the CC-CC ZBC₂NNR is an antiferromagnetic (AFM) semiconductor. Under the transverse electric field, the half-metallicity of 16-CC-CC ZBC₂NNR can be achieved with electric field in the range of $0.2～0.45$ VÅ^?1. Interestingly, the intrinsic half-metallicity exists in BN-CC ZBC₂NNRs when the ribbon width is smaller than ～29.2 Å. For larger ribbon width (～33.5 Å), the system could be converted from ferromagnetic metal to half-metals at a very low critical field of $E=0.02$ VÅ^?1. Meanwhile, it is also shown that the I–V characteristic of BN-BN ZBC₂NNRs shows a negative differential resistance (NDR) effect. These ample electronic and magnetic properties might open great opportunities for BC₂N materials in spintronics and nanoscale device in the future.     

One‐pot synthesis of benzimidazole‐pyrazines and their anticancer activities

The skeleton of fused benzimidazole‐pyrazine was constructed via an Ugi/deprotection/cyclization (UDC) and hydroamination cascade reaction. This four‐step reaction was carried out in a one‐pot procedure with only one‐time column chromatography purification. The representative compound 7b exhibited 67% cell growth inhibitory activity against human breast cancer cell line MDA‐MB‐453 at the concentration of 10μM.     

Two interesting derivatives of 1-amino-1-hydrazino-2,2-dinitroethylene (AHDNE): synthesis and thermal properties

Journal of Thermal Analysis and Calorimetry - Two new interesting compounds, ethanedial-1,2-bis-(2-(1-amino-2,2-dinitroethenyl))hydrazone (EDNH) and 3-dinitromethyl-1,2,4-triazine (DNTA), were...