scholarly journals The color change analysis of historic wooden remains after fire-suppression by fluorinated chemical gases

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Wei Ke ◽  
Wanyu Yang ◽  
Biao Zhou ◽  
Kai Wang ◽  
Jiazhi Sun ◽  
...  
Keyword(s):  
Color Change ◽  
Early Stage ◽  
Fire Suppression ◽  
Fire Risk ◽  
Potential Method ◽  
Historic Buildings ◽  
Change Analysis ◽  
Gaseous Products ◽  
Secondary Damage ◽  
Wooden Surface

AbstractMany wooden Chinese historic buildings are destroyed due to the ravages of frequent fire disasters. The fire risk of historic buildings are highly enlarged since a long-time weathered wooden structures in the natural environment. The clean fire-extinguishing technology using fluorinated chemical gases to put out a historic building fire rapidly at the initial stage is highly recommended and widely used. However, the gaseous hydrogen fluoride (HF) yielded during the fire suppression process could be a potential method to result in secondary damage due to its corrosiveness. Nowadays, experiments were employed to clarify the effect of fire suppression on the surface of historic wooden buildings. Five traditional fluorinated chemical gases, H-37, FK-5-1-12, H-1323, H-2402, and H-1301, are used to suppress a fixed flame. The wooden samples, including a Dao Talisman board, a painting paper, and wooden chips, are placed in a chamber. Wooden chips consist of traditional and weathered samples (acting as the Chinese historic buildings). The concentration of gaseous products yielded from fire suppression are monitored by a gas-FTIR from ABB, and the surface analysis is conducted by a Quanta FEG SEM–EDX from FEI. It is observed that flame enhancement happens at the early stage of fire suppression and varies with fire agents. The amount of F-deposited on the wooden surface is positively correlated with a total amount of gaseous HF. The color change mechanism of the wooden surface is comprehensive, although the amount of HF is a leading factor. The influence of HF on color change depends on the amount of both gaseous H2O and HF. It is concluded that the value of L* of the traditional chip is much easier to be reduced comparing with weathered samples with the same wood grain. The reduction of $${\mathrm{b}}^{*}$$ b ∗ value of weathered samples is much larger than the traditional ones. It suggests the weathered chips show a color shift toward blue because of fire suppression. The present study hopes to provide a basic acknowledgment for the comprehensive understanding of secondary damage caused by fire suppression.

scholarly journals Semiquantitative Fire Risk Grade Model and Response Plans on a National Highway Bridge

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Hojune Ann ◽  
Youngjin Choi ◽  
Jin Hyuk Lee ◽  
Young Ik Jang ◽  
Jung Sik Kong
Keyword(s):  
Large Scale ◽  
Fire Suppression ◽  
Fire Risk ◽  
Surface Damage ◽  
Dynamics Simulation ◽  
Damage State ◽  
Effective Response ◽  
Surface Temperatures ◽  
Secondary Damage ◽  
Risk Grade

For the last ten years, the number of cases of large-scale fires which occur on bridges, tunnels, and underpasses has increased. Such fires cause primary and secondary damage, including loss of human life, traffic congestion, and extensive financial damage. Therefore, a risk grade model and effective response plan need to be established for such cases in order to minimize the social and economic costs of bridge fires. In this study, the hazard factors contributing to bridge fires were selected to apply a risk grade model. A total of 144 bridge fire simulations were performed to calculate a surface temperature based on time by using Fire Dynamics Simulation (FDS). A risk grade in accordance with the degree of surface damage state caused by temperature of bridges was presented, and the mobilization time criteria for fire suppression were proposed. The surface temperatures based on time can be classified according to the vertical clearance and mobilization time criteria for fire suppression. Through the classified maximum surface temperatures based on time for bridges, the risk grade can be estimated according to the degree of surface damage state caused by temperature. In order to evaluate the applicability of the established risk grade model to the actual bridge, the arrival time taken from the bridge to the fire station was calculated through a Geographic Information System (GIS) network analysis, and the grades for actual bridge cases were assessed. The purpose of this bridge fire risk grade model is to establish a disaster prevention strategy based on risk grades and to minimize the subsequent social damage by determining a priori the disaster scale.

Damage indication of 2′, 7′-dichlorofluorescein for epoxy polymer and the effect of water on its damage indicating ability

e-Polymers ◽  
2017 ◽  
Vol 17 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Yakun Guo ◽  
Pengxiang Zhao ◽  
Xiaofang Wang ◽  
Duigong Xu ◽  
Jingrong Zhong ◽  
...  
Keyword(s):  
Epoxy Polymer ◽  
Color Change ◽  
Molecular Form ◽  
Early Stage ◽  
Mechanical Damage ◽  
Gravimetric Analysis ◽  
Structure Transition ◽  
Effect Of Water ◽  
Damage Indicator ◽  
Epoxy Amine

AbstractEpoxy polymer with damage indicating ability was very usable for ships and bridges to detect the cracks at an early stage and to prevent corrosion. 2′, 7′-dichlorofluorescein (DCF), as a damage indicator, was used to report the mechanical damage of epoxy-amine polymer by a strong color change from a light yellow to bright red due to the molecular structure transition from the acid molecular form to the base ion form. The effect of water on damage indicator and damaged epoxy-amine polymer film was evaluated by an immersion test and the properties were characterized by ultraviolet-visible spectrophotometry (UV-Vis), scanning electronic microscopy (SEM), energy dispersive X-ray spectrometer (EDS), zeta potential and thermal gravimetric analysis (TGA). The results showed that DCF was an easy, stable and permanent indicator for epoxy-amine polymer and the water only had a slight influence on the indication stability of damaged epoxy polymer.

QUANTITATIVE MUELLER MATRIX POLARIMETRY TECHNIQUES FOR BIOLOGICAL TISSUES

2012 ◽  
Vol 05 (03) ◽  
pp. 1250017 ◽  
Author(s):  
HONGHUI HE ◽  
NAN ZENG ◽  
DONGZHI LI ◽  
RAN LIAO ◽  
HUI MA
Keyword(s):  
Early Stage ◽  
Structural Characteristics ◽  
Potential Method ◽  
Biological Tissues ◽  
Anisotropic Scattering ◽  
Mueller Matrix ◽  
Matrix Transformation ◽  
Scattering Media ◽  
Tissue Samples ◽  
The Media

We propose and conduct both the rotating linear polarization imaging (RLPI) and Mueller matrix transformation (MMT) measurements of different biological tissue samples, and testify the capability of the Mueller matrix polarimetry for the anisotropic scattering media. The independent parameters extracted from the RLPI and MMT techniques are compared and analyzed. The tissue experimental results show that the parameters are closely related to the structural characteristics of the turbid scattering media, including the sizes of the scatterers, the angular distribution and order of alignment of the fibers. The results and conclusions in this paper may provide a potential method for the detection of precancerous and early stage cancerous tissues. Also, such studies represent the Mueller matrix transformation procedure which results in a set of parameters linking up the Mueller matrix elements to the structural and optical properties of the media.

scholarly journals Understanding Potential-dependent Competition Between Electrocatalytic Dinitrogen and Proton Reduction Reactions

2021 ◽  
Author(s):  
Changhyeok Choi ◽  
Geun Ho Gu ◽  
Juhwan Noh ◽  
Hyun S. Park ◽  
Yousung Jung
Keyword(s):  
Charge Transfer ◽  
Heterogeneous Catalysts ◽  
Early Stage ◽  
Side Reaction ◽  
Potential Method ◽  
Reaction Rates ◽  
Reduction Reaction ◽  
Metal Catalyst ◽  
Proton Reduction ◽  
Catalyst Surfaces

Abstract One of the key challenges to practical electrochemical N2 reduction reaction (NRR) is to lower the overpotential and suppression of the side reaction known as the hydrogen evolution reaction (HER) during the NRR. The experimental NRR activity has been consistently shown to reach a maximum at early stage before reaching the mass-transfer limit and decreases with large overpotentials for many heterogeneous catalysts. Though the volcano-type current-potential relationship shown for NRR is unusual with limited reaction rates at higher overpotentials, the mechanistic origin has not been clearly explained, making the design principles for practical NRR still lacking. Herein, we investigate the potential-dependent reaction activity of NRR and HER using the constant electrode potential method and microkinetic modeling. It manifests the dominating proton adsorption over dinitrogen at small overpotentials leading to the inadequate reaction selectivity towards NRR at many metal catalyst surfaces. A clear potential-dependent competition between the N2 adsorption and *H formation is characterized by the degree of charge transfer in the adsorption process. It is also demonstrated that the larger charge transfer in *H formation is a general phenomenon applied to all heterogeneous catalyst surfaces considered here, that poses a fundamental challenge to realize practical electrochemical NRR. We suggest several strategies to overcome the latter challenges based on the present understandings.

scholarly journals Designing of Fire Extinguisher Based on Sound Waves

2020 ◽  
Vol 9 (4) ◽  
pp. 927-930
Keyword(s):  
Response Time ◽  
Sound Wave ◽  
Early Stage ◽  
Fire Suppression ◽  
Quick Response ◽  
Sound Waves ◽  
Fire Extinguisher ◽  
Incipient Stage ◽  
Initial Stage ◽  
Expected Outcome

The project titled Designing of Fire Extinguisher Based on Sound Waves is associated with new technique of fire extinguisher. Deals with the fire fighting operations with a quick response time. The purpose of sound wave extinguisher is to find out the range of frequency within which fire can be extinguished. It helps the fire fighter to fight the fire at early stage. Fire can be extinguished between 40Hz to 60Hz and the sound wave can extinguish the fire of all types of flames. The fire suppression needs to be done at the incipient stage where the heat and flame produced by the fire is at the minimum point. The expected outcome of the project will be, to counter the fire at its initial stage for better human safety and protection.

scholarly journals Assessing wildland–urban interface fire risk

2020 ◽  
Vol 7 (8) ◽  
pp. 201183
Author(s):  
Hussam Mahmoud ◽  
Akshat Chulahwat
Keyword(s):  
Fire Suppression ◽  
Fire Risk ◽  
The United States ◽  
Fire Frequency ◽  
Policy Makers ◽  
Wildfire Risk ◽  
The Usa ◽  
Calculated Risk ◽  
Reduce Risk ◽  
First Time

Recent wildfire events, in the United States (USA) and around the world, have resulted in thousands of homes destroyed and many lives lost, leaving communities and policy makers, once again, with the question as to how to manage wildfire risk. This is particularly important given the prevalent trend of increased fire frequency and intensity. Current approaches to managing wildfires focus on fire suppression and managing fuel build-up in wildlands. However, reliance on these strategies alone has clearly proven inadequate. As such, focus should be shifted towards minimizing potential losses to communities. Achieving this goal, however, requires detailed understanding of the factors that contribute to community vulnerability and the interplay between probability of ignition, vulnerability and calculated risk. In this study, we evaluate wildfire risk for four different communities across the USA for the duration of May to September to communicate a different perspective of risk assessment. We show, for the first time, that community risk is closely related to wind speed and direction, pattern of surrounding wildland vegetation, and buildings layout. The importance of the findings lies in the need for exploring unique viable solutions to reduce risk for every community independently as opposed to embracing a generalized approach as is currently the case.

scholarly journals Surface Rust Detection Using Ultrasonic Waves in a Cylindrical Geometry by Finite Element Simulation

2018 ◽  
Vol 3 (3) ◽  
pp. 29 ◽  
Author(s):  
Qixiang Tang ◽  
Cong Du ◽  
Jie Hu ◽  
Xingwei Wang ◽  
Tzuyang Yu
Keyword(s):  
Finite Element ◽  
Early Stage ◽  
Steel Corrosion ◽  
Steel Structures ◽  
Potential Method ◽  
Ultrasonic Waves ◽  
Steel Plates ◽  
Fiber Optic Sensor ◽  
Surface Corrosion ◽  
Steel Members

Detection of early-stage corrosion on slender steel members is crucial for preventing buckling failures of steel structures. An active photoacoustic fiber optic sensor (FOS) system is reported herein for the early-stage steel corrosion detection of steel plates and rebars using surface ultrasonic waves. The objective of this study is to investigate a potential method for detecting surface corrosion/rust of steel rods using numerically simulated surface ultrasonic waves. The finite element method (FEM) was applied in the simulation of propagating ultrasonic waves on steel rod models. The pitch-catch mode of damage detection was adopted, in which one source (transmitter) and one sensor (receiver) were considered. In this research, radial displacements at the receiver were simulated and analyzed by short-time Fourier transform (STFT) for detecting, locating, and quantifying surface rust located between the transmitter and the receiver. From our time domain and frequency domain analyses, it was found that the presence, location, and dimensions (length, width, and depth) of surface rust can be estimated by ultrasonic wave propagation.

scholarly journals Using cellular automata to simulate wildfire propagation and to assist in fire management

2019 ◽  
Vol 19 (1) ◽  
pp. 169-179 ◽  
Author(s):  
Joana Gouveia Freire ◽  
Carlos Castro DaCamara
Keyword(s):  
Cellular Automata ◽  
Hot Spots ◽  
Fire Suppression ◽  
Fire Risk ◽  
Added Value ◽  
Southern Portugal ◽  
Management Policies ◽  
Mean Square Difference ◽  
Propagation Rule ◽  
In Fire

Abstract. Cellular automata have been successfully applied to simulate the propagation of wildfires with the aim of assisting fire managers in defining fire suppression tactics and in planning fire risk management policies. We present a cellular automaton designed to simulate a severe wildfire episode that took place in Algarve (southern Portugal) in July 2012. During the episode almost 25 000 ha burned and there was an explosive stage between 25 and 33 h after the onset. Results obtained show that the explosive stage is adequately modeled when introducing a wind propagation rule in which fire is allowed to spread to nonadjacent cells depending on wind speed. When this rule is introduced, deviations in modeled time of burning (from estimated time based on hot spots detected from satellite) have a root-mean-square difference of 7.1 for a simulation period of 46 h (i.e., less than 20 %). The simulated pattern of probabilities of burning as estimated from an ensemble of 100 simulations shows a marked decrease out of the limits of the observed scar, indicating that the model represents an added value to help decide locations of where to allocate resources for fire fighting.

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