Experiment and analysis on microscopic characteristics of pedestrian movement in building bottleneck

In this paper, evacuation experiments are carried out to study pedestrian movement behaviors in building bottleneck. An image processing method based on mean-shift algorithm is used to extract pedestrian movement trajectory. Based on the extracted trajectory, we analyze the microscopic movement characteristics of pedestrians such as lane formation, change of velocity and distance between two sequential pedestrians. A pedestrian lane is a group of pedestrians moving in a column. The lane formation is verifie...     

Bonding W and W–Cu composite with an amorphous W–Fe coated copper foil through hot pressing method

A new method to bond W and W–Cu composite was developed. W and W–Cu composite were bonded by hot pressing method with an amorphous W–Fe coated copper foil as the interlayer. Effects of the interlayer on the microstructure and thermal conductivity of the bonded specimen were investigated. The results showed that bonding quality was improved by using the interlayer. First, metallurgical bonding between W and W–Cu composite was obtained owing to the diffusion of Fe and the crystallization of amorphous W in the coating of the interlayer. Furthermore, both the thermal conductivity and relative thermal conductivity of the bonded specimen were increased because of the malleability of the interlayer.     

Bamboo fibre reinforced biocomposites: A review

The reduction in harmful destruction of ecosystem and to produce low cost polymeric reinforced composites, the researchers are emerging with policies of manufacturing the composites using natural fibres which are entirely biodegradable. These policies had generated safe strategies to protect our environment. The utilization of bamboo fibres as reinforcement in composite materials has increased tremendously and has undergone high-tech revolution in recent years as a response to the increasing demand for developing biodegradable, sustainable, and recyclable materials. The amalgamation of matrix and natural fibres yield composite possessing best properties of each component. Various matrices used currently are soft and flexible in comparison to natural fibres their combination leads to composite formation with high strength-to-weight ratios. The rapid advancement of the technology for making industry products contributes consumer the ease of making a suitable choice and own desirable tastes. Researchers have expanded their expertise in the product design by applying the usage of raw materials like bamboo fibre which is stronger as well as can be utilized in generating high end quality sustainable industrial products. Thereby, this article gives critical review of the most recent developments of bamboo fibre based reinforced composites and the summary of main results presented in literature, focusing on the processing methodology and ultimate properties of bamboo fibres with polymeric matrices and applications in well designed economical products.     

Mechanical and thermal properties of phenolic/glass fiber foam modified with phosphorus‐containing polyurethane prepolymer

Phenolic foam exhibits outstanding flame, smoke and toxicity properties, good insulation properties and low production costs. However, the brittleness and pulverization of phenolic foam have severely limited its application in many fields. In this study, a novel phosphorus‐containing polyurethane prepolymer (DOPU) modifier was firstly synthesized, and then the foaming formula and processing of toughening phenolic foam modified with DOPU and glass fiber were explored. The structure and reactive behavior of prepolymer and phenolic resin were investigated using Fourier transform infrared spectroscopy. The effects of DOPU and glass fiber on the apparent density, compressive strength, bending strength and water absorption were investigated. The results suggested that the apparent density, compressive strength and bending strength of modified phenolic foam tended to increase irregularly with increasing content of DOPU. The addition of DOPU led to lower water absorption of glass fiber‐filled foam. Thermal stability and flame retardancy were examined using thermogravimetric analysis and limiting oxygen index (LOI) tests. It was found that foam with 3% DOPU and 0.5% glass fiber added exhibited good thermal stability and high char yields. The LOI value of modified phenolic foams decreased with increasing DOPU content, but it still remained at 41.0% even if the amount of modifier loaded was 10 wt%. © 2012 Society of Chemical Industry     

Experimental and numerical study on premixed hydrogen/air flame propagation in a horizontal rectangular closed duct

Hydrogen is a promising energy in the future, and it is desirable to characterize the combustion behavior of its blends with air. The premixed hydrogen/air flame microstructure and propagation in a horizontal rectangular closed duct were recorded using high-speed video and Schlieren device. Numerical simulation was also performed on Fluent CFD code to compare with the experimental result. A tulip flame is formed during the flame propagating, and then the tulip flame formation mechanism was proposed based on the analysis. The induced reverse flow and vortex motion were observed both in experiment and simulation. The interactions among the flame, reverse flow and vortices in the burned gas change the flame shape and ultimately it develops into a tulip flame. During the formation of the tulip flame, the tulip cusp slows down and stops moving after its slightly forward moving, and then, it starts to move backward and keeps on a longer time, after that, it moves forward again. The structure of the tulip flame is becoming less stable with its length decreasing in flame propagation direction. The flame thickness increases gradually which is due to turbulence combustion.     

Preparation of UV-curable functionalized graphene/polyurethane acrylate nanocomposite with enhanced thermal and mechanical behaviors

Functionalized graphene nanosheets (f-GNSs) were synthesized by a simple covalent functionalization of graphene with 3-methacryloxypropyl trimethoxysilane (MPTES). The results from FTIR, XPS and XRD showed that MPTES was successfully attached onto the surface of graphene. Functionalized graphene/polyurethane acrylate (f-GNS/PUA) nanocomposites were prepared by UV radiation of PUA with f-GNS. The onset thermal degradation temperature of f-GNS/PUA nanocomposite was increased by 16 °C, at an f-GNS content of 1 wt%. Meanwhile, the storage modulus and glass transition temperature of the nanocomposites were enhanced by incorporating f-GNS into the PUA. This is believed to be attributed to that the covalent functionalization of graphene can improve both the dispersion of f-GNSs in the polymer matrix and the interfacial interactions between f-GNSs and PUA.     

The use of Petri nets and a two-zone model for fire scene reconstruction

Fire scene investigation relies on in situ investigation (observations that take place where the fire occurred) and laboratory analysis. Nowadays the role and place of fire modelling in fire forensic investigation are debated within the forensic community. The main objective of this work is to propose a methodology to consider the stochastic aspect of fire development in a specific case by using fire modelling. Therefore, a stochastic fire safety engineering tool so-called SCHEMA-SI (Stochastic Computation and Hybrid Event Modelling Approach-Sécurité Incendie) developed at the CSTB (French Scientific and Technical Construction Centre) has been used to reconstruct a fire scene that occurred in 2007 in a senior care facility situated in the Paris suburb (France). In this case study, several fire scenarios were generated with SCHEMA-SI from probabilistic data in order to perform fire scene investigation. Each scenario is composed on one hand by a succession of dated events and on the other hand by physical quantities time-evolution at different locations in the building (heat release rate, temperature, interface height…). The objective of this work was to find the scenarios which allow getting an acceptable agreement between the calculated values and the observations from the real situation in the fire scene. Among the thousands of fire scenarios generated, 20% were compliant with the fire scene observations. The analysis of these compliant scenarios gave a better idea of what might have happened in the care facility. At the end, the contribution of numerical simulation in a fire scene analysis is discussed.     

A simplified approach for predicting temperature in reinforced concrete members exposed to standard fire

For evaluating fire resistance of a reinforced concrete member, temperature profile in the cross section of the member is required. Current simplified approaches and design graphs do not yield reliable temperature predictions in rebar and concrete. In this paper, a simplified approach is proposed for evaluating cross-sectional temperatures in fire-exposed reinforced concrete members. The approach is derived through statistical nonlinear regression analysis, utilizing data generated from finite element analysis. The parameters that were varied in the finite element analysis include sectional geometry, concrete characteristics and fire exposure conditions. The validity of the approach for different types of concrete is established by comparing predictions from the proposed equation with data from fire tests and finite element analysis. Through these comparisons it is shown that the proposed equation gives better predictions of temperatures in reinforced concrete members. The applicability of the proposed approach in design situations is illustrated though a numerical example. The simplicity of the proposed method makes it attractive for use in design situations and for incorporation in design standards.     

Effect of fuel soaked time and fuel ratio on the flame spread rate over a porous bed wetted with liquid fuel

An experimental investigation was conducted to explore the rate of flame spread over an unconsolidated porous bed of sand wetted with 2-propanol under a range of operating conditions. Video cinematography was employed to determine the rate of flame spread and characterise the combustion behaviour of the system. The rate of flame spread strongly correlated with: (i) the ratio of fuel volume to the weight of the sand bed, referred to as FR, and (ii) the flame initiation delay, referred to as FID. The rates of flame spread associated with no initiation delay cases were found to rise with increasing FR while for cases associated with any given flame initiation delay the rate of flame spread was found to decrease with increasing FR. In addition, the rate of change in flame spread was observed to be different for beds containing finer particles in comparison to those containing coarser ones.     

Electrical and Acoustic Emissions in cement mortar beams subjected to mechanical loading up to fracture

The application of mechanical loading on cement-based materials generates weak electrical currents due to the formation and propagation of microfractures. This paper introduces the simultaneous recording of electrical signal emissions know as Pressure Stimulated Currents (PSCs) and Acoustic Emissions (AEs) detected in cement mortar beams of rectangular cross-section subjected to mechanical loading using the Three Point Bending tests. The rate of the applied load during the experiments was constant up to the fracture of the specimen. The characteristics of the AE and PSC were put in contrast in order to better understand the evolution of the microfracture processes up to fracture. Specifically, the recorded PSC and AE were studied in terms of their time series, cumulative energy along with AE rate and AE interevent times that may provide information about the upcoming specimen fracture. Moreover, non-extensive statistical physics modeling was attempted in terms of studying the Tsallis entropy. Specifically, the entropic index q was calculated and its dependence on the applied mechanical load was investigated.