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Fei Peng

Bio: Fei Peng is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Heat flux & Ignition system. The author has an hindex of 6, co-authored 21 publications receiving 129 citations. Previous affiliations of Fei Peng include Changsha University of Science and Technology.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a feedback method was utilized to generate a time-dependent heat flux by controlling the output power of radiative heater, which is more reasonable in fire-like environment.

30 citations

Journal ArticleDOI
TL;DR: It is found that the random slowdown process and lock-step have significant influence on the curve configuration and the characteristic parameters, including the concavity–convexity, the inflection point, the maximum flow rate and the critical density etc.

26 citations

Journal ArticleDOI
TL;DR: In this article, side-edge effects on downward flame spread over two parallel polymethyl methacrylate (PMMA) slabs under different pressure environments were investigated. But the results showed that the flame spread rate is controlled by ignition along the side-Edge, rather than at the center of the samples, for experiments with both single and two parallel slabs.

26 citations

Journal ArticleDOI
TL;DR: It is shown that in a higher density corridor, the individual velocity can be significantly affected by the trolleys, and in low densities, trolley case has almost no effect on the velocity.
Abstract: High proportion of pedestrians with trolley case during peak hours is a general phenomenon in comprehensive transportation hubs. This study focuses on the impact of trolley cases on unidirectional pedestrian flow. Nine combinations of exit widths and different ratios of pedestrians carrying trolleys are considered and pedestrian trajectories are extracted by using UWB equipment. Layer distribution is observed from the trajectories of the mixed pedestrian flow formed by the pedestrians with trolley cases and those without trolley cases. With the increase of the ratio of pedestrians with trolleys, the scatter plot of the data will move toward the lower density area of the fundamental diagram, and the maximum specific flow rate will decrease as well. In addition, Greenberg’s logarithmic model is effective for identifying velocity–density relationship. By comparing the individual velocities of pedestrians with trolleys to those without trolleys, it is shown that in a higher density corridor, the individual velocity can be significantly affected by the trolleys. In contrast, in low densities, trolley case has almost no effect on the velocity. The gender of pedestrians is found to have a little impact on their velocities whether or not pedestrians are carrying luggage in the study. The outcomes could be helpful to set the parameters of the crowds with trolleys in simulation and support the optimizing of pedestrian facilities.

18 citations

Journal ArticleDOI
TL;DR: Results show that flame spread rate increases exponentially with pressure, and the exponent of pressure further shows an increasing trend with the thickness of the sample, which indicates a steady-burning stage.
Abstract: The present study is aimed at predicting downward flame spread characteristics over poly(methyl methacrylate) (PMMA) with different sample dimensions in different pressure environments. Three-dimensional (3-D) downward flame spread experiments on free PMMA slabs were conducted at five locations with different altitudes, which provide different pressures. Pressure effects on the flame spread rate, profile of pyrolysis front and flame height were analyzed at all altitudes. The flame spread rate in the steady-state stage was calculated based on the balance on the fuel surface and fuel properties. Results show that flame spread rate increases exponentially with pressure, and the exponent of pressure further shows an increasing trend with the thickness of the sample. The angle of the pyrolysis front emerged on sample residue in the width direction, which indicates a steady-burning stage, varies clearly with sample thicknesses and ambient pressures. A global non-dimensional equation was proposed to predict the variation tendency of the angle of the pyrolysis front with pressure and was found to fit well with the measured results. In addition, the dependence of average flame height on mass burning rate, sample dimension and pressure was proposed based on laminar diffusion flame theory. The fitted exponent of experimental data is 1.11, which is close to the theoretical value.

14 citations


Cited by
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Book ChapterDOI
28 Jan 2005
TL;DR: The Q12-40 density: ρ ((kg/m) specific heat: Cp (J/kg ·K) dynamic viscosity: ν ≡ μ/ρ (m/s) thermal conductivity: k, (W/m ·K), thermal diffusivity: α, ≡ k/(ρ · Cp) (m /s) Prandtl number: Pr, ≡ ν/α (−−) volumetric compressibility: β, (1/K).
Abstract: Geometry: shape, size, aspect ratio and orientation Flow Type: forced, natural, laminar, turbulent, internal, external Boundary: isothermal (Tw = constant) or isoflux (q̇w = constant) Fluid Type: viscous oil, water, gases or liquid metals Properties: all properties determined at film temperature Tf = (Tw + T∞)/2 Note: ρ and ν ∝ 1/Patm ⇒ see Q12-40 density: ρ ((kg/m) specific heat: Cp (J/kg ·K) dynamic viscosity: μ, (N · s/m) kinematic viscosity: ν ≡ μ/ρ (m/s) thermal conductivity: k, (W/m ·K) thermal diffusivity: α, ≡ k/(ρ · Cp) (m/s) Prandtl number: Pr, ≡ ν/α (−−) volumetric compressibility: β, (1/K)

636 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a systematic review of fundamental diagrams of pedestrian flow characteristics developed by using various approaches such as field, experimental and simulation, and identify certain research gaps which provide an opportunity to enhance the understanding of pedestrian flows.
Abstract: The dimensionality of pedestrian infrastructure facilities have a great influence on pedestrian movements and a considerable impact on natural environment of the facility. Understanding the pedestrian movements are crucial to estimate the capacity of the system accurately, especially in the transportation terminals such as railway stations, bus terminals, airports and so forth, where large crowd gathers and transfers. To have a safe and comfortable movement in normal situation and also a quick evacuation in emergency situation, pedestrian movement patterns should be analysed and modelled properly. Once the behaviour of pedestrians is established in terms of speed and density with respect to the environment, even for the colossal systems, the pedestrian flow characteristics can be modelled by applying extremely efficient simulations. The main modelling element in the context of flow models is the fundamental relationship among speed, flow and density. The objective of this study is to review the fundamental diagrams of pedestrian flow characteristics developed for various flow types and geometric elements. This paper also discusses the design values of flow parameters and walking speeds of pedestrians at various facilities. In order to achieve the goal of this paper, we presented a systematic review of fundamental diagrams of pedestrian flow characteristics developed by using various approaches such as field, experimental and simulation. After a thorough review of literature, this paper identifies certain research gaps which provides an opportunity to enhance the understanding of fundamental diagrams of pedestrian flow characteristics.

75 citations

Journal ArticleDOI
TL;DR: A multi-velocities floor field cellular automaton model, established in this paper, shows that a dense crowd evacuation simulation with tiny varied velocity can be conducted very well and that faster evacuees make the evacuation system easily approaching to the jam.
Abstract: It has been hard to model a crowd evacuation process considering different walking abilities using a synchronous cellular automaton. That is because the cross and the overlaps of routes have to be taken into consideration and the conflicts resolution between pedestrians is more complex. However, the desired velocities of evacuees might be quite different due to the discrepancies of the physiological function, including age, gender, physical state, and the psychological behavior, such as the perception and reflection to the dangers. Additionally, an evacuee might change his desired velocity constantly to adapt to the changing evacuation environment. Thus, a multi-velocities floor field cellular automaton model was established in this paper. Using little CPU time, a dense crowd evacuation simulation with tiny varied velocity can be conducted very well. Significant discrepancies between the single-velocity evacuation and the multi-velocities evacuation were observed. The plateaus, where the exit flow rate is rather low, can be well predicted by a dimensionless parameter describing the congestion level of the evacuation system. The crowd evacuation time almost depends on the low desired velocity evacuees, though the proportion is not high. We also observed that faster evacuees make the evacuation system easily approaching to the jam.

67 citations

Journal ArticleDOI
TL;DR: The proposed model is advantageous in terms of flexibility, higher spatial accuracy, wider speed range, relatively low computational cost, and elaborated conflict resolution with synchronous update scheme.
Abstract: This paper proposes a discrete field cellular automaton (CA) model that integrates pedestrian heterogeneity, anisotropy, and time-dependent characteristics. The pedestrian movement direction, moving/staying, and steering are governed by the transfer equations. Compared with existing studies on fine-discretized CA models, the proposed model is advantageous in terms of flexibility, higher spatial accuracy, wider speed range, relatively low computational cost, and elaborated conflict resolution with synchronous update scheme. Three different application scenarios are created by adjusting the definite conditions of the model: (1) The first one is a unidirectional pedestrian movement in a channel, where a complete jam in the high-density region is observed from the proposed model, which is missing from existing floor field CA models. (2) The second one is evacuation from a room, where the evacuation time is independent of the discretization factor, which is different from previous work. (3) The third one is an ascending evacuation through a 21-storey stair system, where pedestrians move with constant speed or with fatigue. The evacuation time in the latter case is nearly twice of that in the former.

49 citations

Journal ArticleDOI
TL;DR: In this paper, a brief overview of the challenges in developing lithium anode-based batteries for low temperature ( 60°C) operation is provided followed by electrolyte design strategies involving Li salt modification, solvation structure optimization, additive introduction, and solid-state electrolyte utilization for LBs.
Abstract: Lithium anode-based batteries (LBs) are highly demanded in society owing to the high theoretical capacity and low reduction potential of metallic lithium. They are expected to see increasing deployment in performance critical areas including electric vehicles, grid storage, space, and sea vehicle operations. Unfortunately, competitive performance cannot be achieved when LBs operating under extreme temperature conditions where the lithium-ion chemistry fail to perform optimally. In this review, a brief overview of the challenges in developing LBs for low temperature ( 60 °C) operation are provided followed by electrolyte design strategies involving Li salt modification, solvation structure optimization, additive introduction, and solid-state electrolyte utilization for LBs are introduced. Specifically, the prospects of using lithium metal batteries (LMBs), lithium sulfur (Li-S) batteries, and lithium oxygen (Li-O2 ) batteries for performance under low and high temperature applications are evaluated. These three chemistries are presented as prototypical examples of how the conventional low temperature charge transfer resistances and high temperature side reactions can be overcome. This review also points out the research direction of extreme temperature electrolyte design toward practical applications.

49 citations