Experimental study and numerical simulation of evacuation from a dormitory

The evacuation process of students from a dormitory is investigated by both experiment and modeling. We investigate the video record of pedestrian movement in a dormitory, and find some typical characteristics of evacuation, including continuous pedestrian flow, mass behavior and so on. Based on the experimental observation, we found that simulation results considering pre-movement time are closer to the experimental results. With the model considering pre-movement time, we simulate the evacuation process and compare the simulation results with the experimental results, and find that they agree with each other closely. The crowd massing phenomenon is conducted in this paper. It is found that different crowd massing phenomena will emerge due to different desired velocities. The crowd massing phenomenon could be more serious with the increase of the desired velocity. In this study, we also found the faster-is-slower effect. When the positive effect produced by increasing the desired velocity is not sufficient for making up for its negative effect, the phenomenon of the greater the desired velocity the longer the time required for evacuation will emerge. From the video record, it can be observed that the mass behavior is obvious during the evacuation process. And the mass phenomenon could also be found in simulation. The results obtained from our study are also suitable to all these buildings in which both living and resting areas occupy the majority space, such as dormitories, residential buildings, hotels (restaurants) and so on.     

超临界二氧化碳萃取磷脂的工艺研究

建立了用超临界二氧化碳萃取法从粗磷脂中萃取纯化磷脂的方法。考察了影响油脂萃取率的因素,采用正交实验确定了最佳萃取条件:萃取压力为30MPa,萃取温度为55℃,萃取时间为2h。大豆、葵花和胡麻三种磷脂得率分别为:88.5%、76.5%及79.2%,含磷量分别为:3.83%、2.62%及2.90%。     

圆柱形霍尔推进器的三维刻蚀模拟与实验研究

通过使用数值模拟和实验相结合的方法研究圆柱形霍尔等离子体推进器。应用蒙特卡洛方法和Particle In Cell (PIC)方法对放电通道内等离子体碰撞和行为进行模拟。建立圆柱形霍尔推进器的物理和数值模型;通过对放电和加速区等离子体的产生和输运进行模拟,掌握了等离子体放电和加速机理以及内磁极的刻蚀
情况。结果表明：随着电压的升高,内磁极刻蚀较为严重;推进器内部离子能量值约为放电电压值的50%左右。同时通过实验方法测定不同放电电压情况下推进器的放电性能。     

苯乙烯阴离子聚合仿真实验软件的研究

烯类单体的阴离子聚合是高分子化学课程中主要理论内容之一,为了使学生更好地掌握和运用理论知识,通常需要配合实验教学加以验证。而传统的烯类单体的阴离子聚合实验由于受各方面条件限制,实验效果欠佳。本文以苯乙烯阴离子聚合实验的开展为背景,介绍了聚合实验软件平台的设计、开发、硬件系统和实验的内容。经过验证,该实验软件平台功能完善,界面简洁,运行稳定,可以结合实际硬件设备以及具体需求进行实验教学。     

A model for vibration transmission of light-heavy structures

The vibration transmission of light-heavy structures is investigated in this paper. The light-heavy structure consists of a thin beam and a mass block. Based on numerical simulations with the finite element method and experiments, the block's effect on the thin beam is defined. A theoretical model for this beam-block structure is successfully developed, which is validated and agrees very well with the numerical and experimental models. Two kinds of transfer functions of velocities between any two points on the beam-block structure are studied experimentally and theoretically. The theoretical transfer functions agree well with the experimental results. There are peaks and valleys in the transfer functions, where the peaks occur at the anti-resonant frequencies of the second point and the valleys at the anti-resonant frequencies of the first point. Away from these peaks and valleys the magnitude of the transfer functions are about 0 dB for two points on the beam, and about 20 dB in our experiments for a point on the beam and another point on the block (close to the theoretical prediction of 18 dB determined by the mass ratio of the beam and the block). With these transfer functions, new techniques might be developed for indirect measurement of the vibration of the thin beam by measuring the vibration of the block.     

流体力学实验教学改革的探讨

在传统的实验教学工作中，存在着不少与学生综合能力培养相脱节的问题。为了克服这些不足，本根据我院的特点，对流体力学实验教学改革中应做的工作和相应的措施进行了探讨。     

Overcoming the Trade-Off between C2H2 Sorption and Separation Performance by Regulating Metal-Alkyne Chemical Interaction in Metal-Organic Frameworks

Designing porous materials for C₂H₂ purification and safe storage is essential research for industrial utilization. We emphatically regulate the metal-alkyne interaction of Pd^II and Pt^II on C₂H₂ sorption and C₂H₂/CO₂ separation in two isostructural NbO metal–organic frameworks (MOFs), Pd/Cu-PDA and Pt/Cu-PDA . The experimental investigations and systematic theoretical calculations reveal that Pd^II in Pd/Cu-PDA undergoes spontaneous chemical reaction with C₂H₂, leading to irreversible structural collapse and loss of C₂H₂/CO₂ sorption and separation. Contrarily, Pt^II in Pt/Cu-PDA shows strong di-σ bond interaction with C₂H₂ to form specific π-complexation, contributing to high C₂H₂ capture (28.7 cm³ g⁻¹ at 0.01 bar and 153 cm³ g⁻¹ at 1 bar). The reusable Pt/Cu-PDA efficiently separates C₂H₂ from C₂H₂/CO₂ mixtures with satisfying selectivity and C₂H₂ capacity (37 min g⁻¹). This research provides valuable insight into designing high-performance MOFs for gas sorption and separation.     

Development of some hypersonic benchmark flows using CFD and experiment

Abstract. This paper presents a set of test cases in high speed aerodynamics that describe our perceived relationship between experiment and computation. Computational fluid dynamics, with sensible interpretation, can guide experimental design, so that wind tunnel studies can focus better on fundamental ‘benchmark’ studies. Likewise experimental data may be used as feed back to evaluate codes and to improve their physical modelling. Here we present several test cases, developed in our laboratory, that we regard as basic ‘building blocks’ for high speed aerodynamics. These include: design for boundary-layer/pressure-gradient interaction; cavity flows; shock-wave/boundary-layer interactions; techniques for a graduated and controlled study of three-dimensional separated flows. Received 10 October 2001/ Accepted 19 November 2002 Published online 4 February 2003 Correspondence to: R. Hillier (r.hillier@ic.ac.uk) An abridged version of this paper was presented at the 23rd Int. Symposium on Shock Waves at Fort Worth, Texas, from July 22 to 27, 2001     

Sequential generation ofD-optimal input designs for linear dynamic systems

This paper considers the problem of sequentially generating test signals for parameter estimation in linear, single-input, single-output, discrete-time systems using a frequency-domain approach based on the theory of optimal experiments in regression analysis. The input signals are power constrained and are optimal in the sense that system information is maximized, where the criterion employed is the determinant of the Fisher information matrix (D-optimality). A class of algorithms is investigated, each member of which generates a sequence of input designs converging to aD-optimum. A number of these algorithms are compared computationally.     

分析化学在线课堂引入实验视频教学模式改革

The current situation of analytical chemistry teaching and reform, as well as some problems in micro-videos of online classroom was analyzed. In order to solve these problems, short experimental videos were introduced to the online classroom to demonstrate experimental methods. The new teaching mode achieves mutual integration and promotion of the classroom teaching and laboratory teaching, providing opportunities and challenges for the teaching reform of chemistry online course. The results of the teaching reform were investigated and analyzed by questionnaire.