Ping Zhang's research while affiliated with Tsinghua University and other places

Despite controlled experiments and computer-based simulations are important tools to studying pedestrian behaviour, the pedestrian data collected by both have limitations. These limitations are manifested in the disconnect between the behavioural characteristics of real-world pedestrians and the way they are represented in these simulated environments. Recent developments in mixed reality and live, virtual, and constructive (LVC) simulation have the potential to make up these limitations. This paper reports on a study and project prototypes for building a client-server system using simulation modelling software tools and mixed reality headsets. We set up a mixed reality space containing real pedestrians and holographic-projection virtual pedestrians in a real building environment. The virtual pedestrians move according to a pedestrian dynamics model and interact with real pedestrians and environments in real-time. Taking evacuation in high risk as an example, we demonstrate how interactions between pedestrians, even pedestrians and environments can be achieved in the space while collecting data on the entire process. This study introduces a new approach to study pedestrian behaviour in buildings: mixed reality LVC simulation.

Surveillance cameras are widely applied for indoor occupancy measurement and human movement perception, which benefit for building energy management and social security. To address the challenges of limited view angle of single camera as well as lacking of inter-camera collaboration, this study presents a non-overlapping multi-camera system to enlarge the surveillance area and devotes to retrieve the same person appeared from different camera views. The system is deployed in an office building and four-day videos are collected. By training a deep convolutional neural network, the proposed system first extracts the appearance feature embeddings of each personal image, which detected from different cameras, for similarity comparison. Then, a stochastic inter-camera transition matrix is associated with appearance feature for further improving the person re-identification ranking results. Finally, a noise-suppression explanation is given for analyzing the matching improvements. This paper expands the scope of indoor movement perception based on non-overlapping multiple cameras and improves the accuracy of pedestrian re-identification without introducing additional types of sensors.

In order to improve the efficiency of occupant evacuation in high-rise and intelligent buildings, this paper analyzes the disadvantages of traditional emergency evacuation in high-rise buildings and conducts the feasibility analysis of using an elevator as the evacuation tool. With the help of evacuation software, Pathfinder, simulation experiments are given to study the collaborative strategies among stairs and elevators under partial and total building evacuation. Results show that with the guarantee of safety and reliability, an elevator is a very efficient tool to evacuate occupants in high-rise buildings, especially those mobility impaired occupants. Combination of stairs and elevator can not only reduce the evacuation time but also shorten the occupants’ travel distance.

Inclined ceiling jet fire may occur in a low-pressure aircraft cargo, which poses a great threat to airplane safety. To simulate an inaccessible area in cargo compartment, investigate the effects of pressure on the combustion characteristics of inclined ceiling jet fire, a series of fire experiments under an inclined ceiling (0°,15°,30°,45°) in different pressure environments (50 kPa, 76 kPa, 101 kPa) were carried out in a full-size simulated cargo compartment. N-heptane square pool fires (20 × 20 × 5 cm), as radiation-controlled oil pool fires, were used as fire sources. The burning rate, heat radiation feedback, flame temperature, and ceiling temperature were measured and analyzed. The experiments showed that the heat radiation to pool surface had a significantly positive correlation with ambient pressure, and the penetration of thermal radiation made up a large proportion of heat radiation feedback, which should not be neglected for thin-layer oil burning. When the inclination angle was θ=0° or θ=15°, owing to the effects of ceiling, no significant differences existed on the rate of the axial flame temperature decrease in different pressure environments. Moreover, there were some fluctuations when flame was close to the ceiling. Based on previous models, new correlations to predict ceiling temperature in the upward direction and downward direction in different pressure environments were proposed, respectively.

Evacuation indicator is an important factor affecting evacuation efficiency during emergency evacuation. In order to study the relationship between the distribution of human's points of regard and evacuation indicators during building evacuation, this paper carried out two groups of building emergency evacuation experiments, to get the data of human's points of regard, one of the experimenters was selected to put on eye tracker during the experiment. This paper presents a method to preprocess the data of eye tracker and further analyzes the pretreatment results. The results show that evacuation indicators in different areas are suitable for different placement, which based on the position distribution of human's points of regard. For example, evacuation indicators in the corridor are suitable for higher placement, and evacuation indicators in the staircase are suitable for lower placement.

This paper presents an emergency-oriented procedure to recognize trajectory patterns by analyzing GPS data collected from intelligent sensor devices. An overall description, including design architecture and system modules, is presented. The primary issues are devoted to satisfying the requirements of key group identification and surveillance under normal and emergency circumstance. For the sake of panoramic understanding of human distribution and movement, semantic trajectory information is extracted from dynamic transportation data and static human distribution data. The sequential Monte Carlo method in conjunction with a state-transition model is employed to predict the updating real-time locations. The proposed algorithm selects particles from time-stamped sequential historical data sets. Simultaneously, a resampling strategy is developed to replace low-weight particles. A curve similarity measurement called Fréchet distance is employed to compare trajectories and city roads. Afterward, human daily location and significant locations are identified based on the clustering method. To evaluate the proposed procedure and methods, sequential trajectory data sets come from the GeoLife project along with human distribution logs from smartphone application EMAPP are utilized. Finally, we demonstrate the potential of dealing location information for promoting emergency management.

Seismic disaster can cause severe damage to the urban system like infrastructure breakdown, residential isolation and corresponding secondary disasters. Dealing with the impact of these damages at the urban area requires a better understanding of city vulnerability and corresponding emergency management. Meanwhile, accurate damage simulation integrated with geographic information system is able to improve emergency response level. In this paper, Chaoyang district, a densely and populated region of Beijing, is studied as a scenario area. Falling debris from tall buildings is considered as one of the most destructive elements to the traffic, which can cause severe road blockage. In particular, risk-rating scheme is depicted by incorporating building vulnerability and city fire hazard. In order to optimize emergency transportation system for post-earthquake, a vehicle routing problem is developed to decrease the total travelling route for dispatching commodities. According to the problem's property, the Tabu search method based on heuristic algorithm is used. Furthermore, rescue from the inner city and exterior zone are discussed. For promoting emergency response, this study aims to give a brief description of the circumstance that may be encountered during and after seismic disaster.

This article presents a social network based methodology for improving urban traffic evacuation capability in emergency response by using smart phones. Considering destructive and unexpected characteristics of natural hazards or man-made disasters, the effected people cannot evacuate efficiently when they face the unknown impacts of these events. Therefore, a smart phone application, called EMAPP, is developed to tackle this difficulty. An overall description including design architecture and system modules is provided. Optimal shelter choice strategy is given by using the modified Dijkstra’s algorithm. The Nagel-Schreckenberg model loaded by vehicle arrival rate is implemented to produce the spatio-temporal diagrams of the vehicles. Both traffic congestion and cascading failure during real-time emergency evacuation are analyzed. The main issues are devoted to link the affected people, geographic information and traffic conditions through the smartphone application. Therefore, in emergency evacuation, the affected people can receive mutual help and urban resilience can be enhanced.

Evacuation shelter and route selection are indispensable parts of emergency planning. An efficient plan can effectively evacuate people from a dangerous place to a safer location. Meanwhile, it is crucial to improve risk management. This article presents a multi-objective optimization algorithm based on social media and GIS to optimize shelter usage and personnel distribution considering social relationship. The proposed algorithm is examined using a case study for the Zhongguancun district in Beijing. The district is modeled by the graph theory. Traffic route data and population distribution are synthesized to form a risk map. Furthermore, the Floyd-Warshall algorithm is adopted to find a shortest path route in order to relocate evacuees to a safer place effectively. Efficiency, fairness and social relation are taken into consideration in this context.