Search

Copyright of Fire Safety Science is the property of Fire Safety Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a Laplace transform model for an urban tunnel ventilation system. This model allows one to witness higher performance for supervisory control and data acquisition (SCADA) in terms of monitoring and control of an urban area tunnel based on measurement systems. This proposed model illustrates the ventilation control system framework as well as the emergency response system for urban area tunnels such that smoother controllability and higher security in the operation of tunnels can be envisioned. The salient contributions of this work can be stated as a novel method for modeling tunnel ventilation systems and the implementation of an emergency response plan for a futuristic intelligent transportation system. The simulation results exhibit that the proposed model outperforms the ventilation system in the high-density traffic jams and further the efficient operation of the tunnel. Likewise, comparison results and experimental results are addressed to emphasize the validation of this method and to be helpful in proving the reliability of the results obtained in this study. These results show that the ventilation control system reaches the desired CO value either in high-traffic volume conditions or in normal traffic conditions. [ABSTRACT FROM AUTHOR]

Coal dust in continuous mining tunnels is extremely hazardous to drivers and other workers. In order to solve this problem, a continuous mining tunnel model is built based on computational fluid dynamics and gas–solid two-phase flow theory. Fluent 19.2 software is used to analyze the effects of air pipe outlet location (d) and external air curtain (EAC) outlet air velocity (vvent) on dust dispersion. The effects on the characteristics of dust dispersion are analyzed separately, and it is concluded that d=7 m is optimal. At this distance, the average dust concentration at the breathing zone height is low, and there is no significant fluctuation or rebound in the dust concentration during the dispersion process. When vvent=6 m/s , the highest dust separation efficiency of 89.3% occurs at a breathing height of y=1.6 m and x=5.82 m (133 mg/m3). The driver's position is protected with a dust separation efficiency of 79.2%. As the vvent value increases, the dust separation efficiency increases slowly. The cost of generating airflow should be considered for dust reduction efficiency, and an optimal vvent of 6 m/s is recommended. The findings of this study can provide a theoretical basis for the selection of ventilation parameters for air curtain dust reduction in continuous mining tunnels with rectangular cross section. [ABSTRACT FROM AUTHOR]

In this paper, the temperature rise in the longitudinal direction, the heat release rate (HRR), the endless area temperature under the ceiling of the utility tunnel, and the root of HRR (oil and fuel type), cable type, number of cable layers and and cables per layer. The effects of airtightness, natural ventilation, and longitudinal ventilation on the fire characteristics of cable compartments were compared. The results showed that the effects of enclosed cable tunnels and natural ventilation on fire behavior near walls in cable tunnels were compared. Compared with the natural ventilation state, when placing RVVR type cables, the fire duration of the enclosed cable compartment was shorter, the ceiling temperature rise was greater. And the time that was necessary to increase the ceiling temperature to its maximum value was shorter. The HRR inside the enclosed cable compartment was very high and could almost reach its peak quickly. The contribution of this article is to reduce the social and economic costs of utility tunnels by preventing tunnel fires. [ABSTRACT FROM AUTHOR]

Thermoacoustic instability in turbulent combustion systems emerges from the complex interplay among the flame, flow, and acoustic subsystems. While the onset of thermoacoustic instability exhibits a global order, the characteristics of local interactions between subsystems responsible for this order are not well understood. Here, we utilize the framework of synchronization to elucidate the spatiotemporal interactions among heat release rate fluctuations in the flame, velocity fluctuations in the flow, and acoustic pressure fluctuations in a turbulent combustor, across the bluff-body stabilized flame. We examine two forms of thermoacoustic instability, characterized by phase synchronization and generalized synchronization of the acoustic pressure and global heat release rate oscillations. Despite the presence of global synchrony, we uncover a coexistence of frequency synchrony and desynchrony in the local interaction of these oscillations within the reaction field. In regions of frequency-locked oscillations, various phase-locking patterns occur, including phase synchrony and partial phase synchrony. We observe that the local formation of small pockets of phase synchrony and strong amplitude correlation between these oscillations is sufficient to trigger the state of global phase synchronization. As the global dynamics approach generalized synchronization, these local regions of synchrony expand in the reaction field. Additionally, through coupled analysis of acoustic pressure and local flow velocity fluctuations, we infer that the spatial region of flow–acoustic synchrony plays a significant role in governing thermoacoustic instabilities. Our findings imply that, in turbulent combustors, an intrinsic local balance between order, partial order, and disorder within the coupled subsystems sustains the global order during thermoacoustic instability. [ABSTRACT FROM AUTHOR]

Early fire identification is critical to saving lives and property. One viable strategy for improving fire detection systems' efficacy and precision is the use of Internet of Things (IoT) technology. This article details research into the conception and development of an IoT, ESP32-based, Arduino MEGA-connected smart pre-alert detection system for fires. Because of its flexible nature, the Arduino microcontroller can easily exchange data with various sensors for real-time monitoring and analysis. This study surveys the existing literature to provide insight into many approaches to early fire detection (forecasting), such as sensor fusion methods and the use of the intelligence concept as a pre-predictor. The research highlights the need to set up sophisticated fire monitoring and alarm systems and to develop predictive models based on sensor data. This study illustrates how embedded systems via IoT technology and the ESP32 architecture may improve the efficiency and dependability of very early fire detection systems. This research adds to the expanding corpus of information that may be used to improve fire safety in contemporary settings. The proposal's sensors include an Arduino MEGA, an ESP32, a MAX6675 module, an MQ-Smoke, and an MQ-Natural Gas for collecting data, which are then processed using Cloud Firebase and a sleek mobile interface that can be reached overseas at any time. [ABSTRACT FROM AUTHOR]

In recent years, there have been reports of gas leakage accidents during the transportation of gas tankers in tunnels, potentially leading to destructive explosions. However, the overall distribution of gas concentration in the entire tunnel has not been experimentally investigated. This study presents a series of brine-water experiments to explore the characteristics of buoyant gas flow in tunnel leakage accidents. The gas distribution is categorized into a stably stratified longitudinal current and a source region. Gas concentration in the tunnel is correlated with the dimensionless reduced gravity, which increases with the source buoyancy flux but decreases with the source release velocity. A model is proposed to estimate the maximum gas concentration of the longitudinal current. The spatial range of the explosive region is influenced by the source buoyancy flux and the leakage velocity. However, the propagation velocity of the longitudinal current is primarily controlled by the source buoyancy flux, with the source momentum having a negligible effect. The thickness of the longitudinal gas flow, δ, linearly decreases from the source region to the tunnel ends. A dimensionless parameter, λ, is introduced to characterize δ. When λ < 1.25, δ rapidly increases with λ and then remains approximately constant when λ exceeds 1.25. This study contributes to a better understanding of buoyant gas flow in tunnel leakage accidents. [ABSTRACT FROM AUTHOR]

Wild and forest fires pose a threat to forests and thereby, in extension, to wild life and humanity. Recent history shows an increase in devastating damages caused by fires. Traditional fire detection systems, such as video surveillance, fail in the early stages of a rural forest fire. Such systems would see the fire only when the damage is immense. Novel low-power smoke detection units based on gas sensors can detect smoke fumes in the early development stages of fires. The required proximity is only achieved using a distributed network of sensors interconnected via 5G. In the context of battery-powered sensor nodes, energy efficiency becomes a key metric. Using AI classification combined with XAI enables improved confidence regarding measurements. In this work, we present both a low-power gas sensor for smoke detection and a system elaboration regarding energy-efficient communication schemes and XAI-based evaluation. We show that leveraging edge processing in a smart way combined with buffered data samples in a 5G communication network yields optimal energy efficiency and rating results. [ABSTRACT FROM AUTHOR]

Forest fires represent a significant menace to both the ecological equilibrium of forests and the safety of human life and property. Upon ignition, fires frequently generate billowing smoke. The prompt identification and management of fire sources and smoke can efficiently avert the occurrence of extensive forest fires, thereby safeguarding both forest resources and human well-being. Although drone patrols have emerged as a primary method for forest-fire prevention, the unique characteristics of forest-fire images captured from high altitudes present challenges. These include remote distances, small fire points, smoke targets with light hues, and complex, ever-changing background environments. Consequently, traditional target-detection networks frequently exhibit diminished accuracy when handling such images. In this study, we introduce a cutting-edge drone-based network designed for the detection of forest fires and smoke, named FSNet. To begin, FSNet employs the YOCO data-augmentation method to enhance image processing, thereby augmenting both local and overall diversity within forest-fire images. Next, building upon the transformer framework, we introduce the EBblock attention module. Within this module, we introduce the notion of "groups", maximizing the utilization of the interplay between patch tokens and groups to compute the attention map. This approach facilitates the extraction of correlations among patch tokens, between patch tokens and groups, and among groups. This approach enables the comprehensive feature extraction of fire points and smoke within the image, minimizing background interference. Across the four stages of the EBblock, we leverage a feature pyramid to integrate the outputs from each stage, thereby mitigating the loss of small target features. Simultaneously, we introduce a tailored loss function, denoted as L f o r e s t , specifically designed for FSNet. This ensures the model's ability to learn effectively and produce high-quality prediction boxes. We assess the performance of the FSNet model across three publicly available forest-fire datasets, utilizing mAP, Recall, and FPS as evaluation metrics. The outcomes reveal that FSNet achieves remarkable results: on the Flame, Corsican, and D-Fire datasets, it attains mAP scores of 97.2%, 87.5%, and 94.3%, respectively, with Recall rates of 93.9%, 87.3%, and 90.8%, respectively, and FPS values of 91.2, 90.7, and 92.6, respectively. Furthermore, extensive comparative and ablation experiments validate the superior performance of the FSNet model. [ABSTRACT FROM AUTHOR]

The construction of multiple tunnels across inland rivers has had a significant influence on the improvement of the transportation infrastructure. The technology for constructing tunnels is progressing towards the development of larger cross-sections, longer distances, and the ability to withstand high hydraulic pressure in complex hydrogeological conditions, including high-permeability strata. In order to ensure the face stability of shield tunnels under high hydraulic pressure that crosses a fault fracture zone, it is necessary to study the progressive failure mechanism of shield tunnel faces induced by high hydraulic pressure seepage. This paper employs finite element numerical simulation software to methodically examine the variation in the characteristics of the water seepage field, limiting support force, and face stability failure mode of shield tunnels passing through fault fracture zones with high hydraulic pressure under varying fault fracture width zones. The results show that the formation hydraulic gradient will progressively widen when the tunnel face is located within the undisturbed rock mass and is advanced towards the area of fault fracture. This will raise the likelihood of instability in the shield tunnel and progressively raise the limiting support force on the tunnel face. Moreover, as the tunnel face nears the region of fault fracture within the undisturbed rock mass, the damage range increases gradually. In addition, due to the increase in seepage force, the angle between the failure area and the horizontal plane becomes more and more gentle. On the contrary, as the tunnel's face moves closer to the undisturbed rock mass from the region of the fault fracture, the damage range gradually decreases, and the dip angle between the damage area and the horizontal plane becomes steeper and steeper due to the decreasing seepage force in the process. The study findings presented in this work are highly significant, both theoretically and practically, for the design and management of safety. [ABSTRACT FROM AUTHOR]

Featured Application: Thermal Storage in Off-Grid Industrial Applications has provided a reliable energy supply solution for high solar potential areas, such as mining and production processes that require stable energy consumption. This paper presents a numerical model for thermal energy storage systems' design, development, and feasibility. The energy storage was composed of a tank that stores phase change material (AlSi12) and internal pipes with heat transfer fluid (Cerrolow 117), coupled to a power block to dispatch electrical energy on a small scale for off-grid industrial applications. Subsequently, the evolution of the temperature in charge/discharge cycles, temperature degradation, and storage efficiency was determined with the appropriate magnitudes and behavior through the resolution of a numerical model. In addition, for the proposed electric power generation plant for an off-grid pumping system in the mining industry of Chile, a numerical model was developed using the finite volumes method to simulate the thermocline performance. As a result, the temperature history reflects stable thermal behavior, low degradation, and high efficiency of approximately 92%, with a storage time increasing up to 13 [h] and 384.8 [kWh] capacity. Also, implementation was feasible on a small scale due to its compact, modular, and economically competitive characteristics in a concentrated solar power plant. Finally, the proposed design was proven to be an accurate and reliable alternative for small-scale off-grid mining applications. [ABSTRACT FROM AUTHOR]

Capturing laparoscopic videos helps physicians to conduct minor surgeries and treatments effectively. But the problem is that these videos are easily affected by environmental conditions and various distortions that diminish the overall clarity. This reduces the possibility for physicians to complete the treatments successfully. To deal with this, video enhancement techniques are introduced, which require the help of effective distortion-type classification strategies. This work presents a compelling and accurate distortion classification technique based on transfer learning. The proposed work includes three main stages: feature extraction, fine-tuning and classification. The DenseNet-65 convolutional neural network (DDCNN) model has been chosen as the baseline, where the DenseNet-65 is pre-trained on the Imagenet dataset. The pre-trained model is used for feature extraction using the zero-shot transfer learning (ZSTL) technique, where only the first few layers of a model are engaged to extract the crucial spatial features. Then, the fine-tuning process was carried out using the flow direction algorithm (FDA) that tunes the parameters of the top layers. Finally, classification has been done using the softmax classifier, where the model classifies five different distortions in videos such as smoke, AWGN noise, motion blur, defocus blur and uneven illumination. The work has been implemented in Python, and the ICIP2020 challenge dataset is used for evaluations. The achieved accuracy outcomes of different distortion classes are smoke (97.8%), AWGN noise (100%), Motion blur (95.83%), Defocus blur (98.65%) and uneven illumination (99.01%). Moreover, the performance of a proposed scheme is examined in terms of different performance measures accuracy (98.8%), F1-score (96.9%), processing time (0.037 s), Spearman rank order correlation coefficient SROCC (0.995), Pearson linear correlation coefficient (PLCC) (0.995), and Kendall rank order correlation coefficient (KROCC) (0.857). The performance evaluations proved the efficacy of the proposed method compared to other techniques. [ABSTRACT FROM AUTHOR]

During the actual construction of tunnel sidewall lining, construction workers often use only one or two windows per layer for pouring in order to reduce the construction sequence, which often leads to a reduction in the quality of tunnel sidewall concrete pouring. Therefore, this study analysed the necessity of the window-by-window pouring of sidewall lining through the study of concrete flow characteristics of the tunnel sidewall lining pouring process, and the reasonable spacing of pouring windows was analysed. This study firstly verified the accuracy of the simulation parameters and the feasibility of the simulation method of the lining pouring process through indoor experiments and simulation analyses, and then it numerically simulated and analysed the flow of concrete during the lining pouring process of tunnel sidewalls. The following conclusions were made: the smaller the slump of the freshly mixed concrete, the higher the pumping flow rate; additionally, the shorter the one-time pouring distance, the smaller the spacing of the trolley feeding window should be. Furthermore, this study makes suggestions for the reasonable spacing of pouring trolleys under several working conditions. [ABSTRACT FROM AUTHOR]

In mines, tunnel ventilation is monitored using wind speed sensors to measure the stability of the mine ventilation system. However, opening and closing the air door will cause violent fluctuations in the monitoring data of the wind speed sensors. When false alarms are triggered, the staff can diagnose only the mine ventilation system based on their experience. A numerical simulation method is adopted to explore the changes in the flow field during the opening and closing of the air door to address this issue. In addition, a method that is based on the wind speed data of a single sensor is proposed to identify the time and divide the stages of air door opening and closing. The experimental results showed that the proposed method can successfully identify the air door opening and closing time and apply stage division when needed. [ABSTRACT FROM AUTHOR]

When a tunnel fire occurs, due to the difference of tunnel width and slope, both smoke countercurrent length distribution law and critical velocity will become different, and these two are very important parameters in tunnel longitudinal ventilation design. Therefore, for the design of smoke control and longitudinal ventilation of the tunnel, based on actual highway tunnel size, this paper established and ran a series of numerical simulations through FDS simulation software to study tunnel width and slope's effect on smoke countercurrent length and critical velocity. The results of this paper show that smoke countercurrent length decreases with tunnel slope's increase and increases with tunnel width's increase. Through dimensionless analysis, the prediction formulas of smoke countercurrent length and critical wind speed of large cross-section tunnel about tunnel width, slope and height are modified and established. The research conclusions can provide a theoretical basis for the longitudinal ventilation design, smoke prevention and exhaust measures and personnel evacuation in large cross-section tunnel fires. [ABSTRACT FROM AUTHOR]

The urban utility tunnel is an indispensable part of modern engineering construction. However, the fire risk cannot be ignored due to the narrow space and limited ventilation of the utility tunnel. A study of smoke filling is performed in a 1/8-scaled utility tunnel (25 m × 0.5 m × 0.45 m). Five heat release rates (5, 10, 15, 20 and 25 kW) and four positions of fire sources are used for tests. The initial position of the one-dimensional smoke movement of strong plume is determined. Based on the traditional model, the longitudinal temperature attenuation model of tunnel smoke is established with consideration of radiation and convection heat losses. The theoretical value of the longitudinal temperature rise of smoke is in good agreement with the experimental value. A one-dimensional spreading velocity model is established that coincides well with the experimental value, and the relative error is less than 20%. The spreading velocity of smoke is increased by the heat release rate. The velocity of the smoke spreading at the near end is smaller than that at the center, due to the long spreading route. The current conclusions disclosed in this study provide important guidance for the ventilation design of utility tunnels for fire smoke scenarios. [ABSTRACT FROM AUTHOR]

This paper explores the temperature distribution (TD) and maximum temperature (MT) below the ceiling induced by the ceiling jet of an asymmetric dual fire sources in a naturally ventilated tunnel. Considering strong plumes, this study investigates the effects of fire size and spacing of asymmetric dual fire sources on TD and MT. With the same power of fire source, when the size of one of the fire sources increases, the corresponding maximum temperature beneath ceiling decreases. Additionally, the temperature peak below the ceiling shifts from one to two, and the peak temperature of the larger fire source is lower compared to that of smaller one. When the fire sources distance increases, the maximum temperature initially decreases and then increases. Beyond a certain distance, the maximum temperature no longer changes with increasing distance. In this study, we investigated the effect of fire source size and spacing on the MT of the tunnel ceiling for asymmetric dual fire sources. A new model for predicting the MT underneath the tunnel ceiling was developed, taking into account the factors as fire spacing and fire size. The model is able to make effective predictions of the simulation results. [ABSTRACT FROM AUTHOR]

In the ventilation management of urban traffic tunnels, to improve the efficiency of ventilation system and environmental quality, an intelligent tunnel fan control method based on real-time monitoring was proposed in this paper. This method can predict pollutant concentration trends using an embedded semi -empirical physical model and carry out fuzzy control over tunnel fan operations, including opening, closing, and frequency adjustments. Additionally, by continuously refines the embedded model忆s parameters through machine learning, the control strategies can be optimized, providing more accurate data support and intelligent control strategies for fan regulation. Firstly, the content and working process of the intelligent tunnel fan control method were described in detail. Subsequently, combined with the measured PM2.5 data from representative highway tunnels in Dalian, the economic analysis of this control method was conducted using the Dalian Bay Immersed Tunnel Project as a case study. The results show that this method can reduce the ventilation system operational costs and has great energy-saving potential. [ABSTRACT FROM AUTHOR]

An understanding of the rheological characteristics of surrounding rock is key to predicting the large deformations of tunnels in soft rock in cold regions, particularly due to freeze–thaw (F–T) damage of the surrounding rock. Therefore, in this study, a series of F–T cycle and triaxial creep tests of surrounding rocks were conducted on the basis of typical tunnel projects in cold regions, and the parameters of the test data were identified by the fractional-order creep damage constitutive equation. Then, a constitutive model was embedded into the Fast Lagrangian Analysis of Continua in 3 Dimensions software to analyze the coupled creep deformations of the surrounding rock and supporting structure in response to F–T cycles while excavating the Ningchan tunnel. The calculated results accurately reflected the creep deformation characteristics of the surrounding monitoring points after tunnel excavation under different numbers of F–T cycles. Finally, a tunnel operation model was derived and used to analyze the creep deformation characteristics of a tunnel during operation in a cold area. The calculation results showed that with increasing time, the lining structure and surrounding rock at different monitoring points in the tunnel underwent various degrees of creep deformation. Additionally, the creep deterioration effect of the surrounding rock was more severe after the F–T cycles, which endangered traffic safety. [ABSTRACT FROM AUTHOR]

The first step in current methodologies for the (probabilistic) performance-based fire safety design and assessment of structures is characterizing fire hazard scenario(s). Next, structural response analysis is performed to estimate hazard consequences in terms of damage or loss metrics of interest. These metrics are eventually appraised to verify whether various performance objectives are achieved and design iterations are needed. Nevertheless, such approaches rely on preliminary assumptions on the structural configuration and features characterizing scenarios used as thermal inputs. Consequently, they do not fully exploit the fire–structure coupling effect, where fire affects a structure, and the characteristics of the structure also affect the combustion process and fire dynamics. Indeed, the structural design choices define the fire scenarios that could potentially affect the structural and nonstructural performance. This paper introduces a consequence-oriented fire intensity optimization (CFO) approach to the fire safety design of structures to address such limitations. The proposed approach considers fire scenarios as additional design variables and delivers them as procedure outputs, optimizing the balance between increasing structural capacity and decreasing fire intensity. Furthermore, it evaluates the effect of input uncertainties through Monte Carlo sampling. A single-span bridge subject to a car fire is used to showcase the proposed approach. For this case study, it is shown that fire scenario characteristics (fuel bed and traffic load positions, heat release rate history) maximizing consequences are strongly correlated to the structural features and cannot be set a priori. Finally, design decisions exploiting the described coupling effect to achieve various performance objectives are discussed. Overall, the proposed approach highlights the benefits of enhancing the fire and heat transfer model's capability to capture the fire–structure coupling effect for achieving more optimized design solutions. [ABSTRACT FROM AUTHOR]

Despite management efforts, like the implementation of escape panels and openings, unwanted catch remains a challenge in demersal trawl fisheries. Studies report that selectivity in escape panels and openings can be low. We explore the selective potential of a large escape opening placed at the aft of the trawl. We then examine if adding a dark tunnel behind the escape opening can increase the escape efficiency of fish by triggering a station-holding behaviour. Our results showed limited escapement through the large escape opening; however, significant for narrow length ranges of some species. Adding the dark tunnel significantly increased the escapement for all analysed species, with escapement up to 70% (40%–83%) and 63% (8%–93%) for roundfish and flatfish, respectively. As target species, a loss of crustaceans up to 85% (60%–96%) highlighted the importance of optimising the integration of the dark tunnel in demersal trawls. Providing the dark tunnel is integrated correctly, our results suggest that currently implemented escape panels and openings with low selective efficiency could be substantially improved by simple means like the dark tunnel. [ABSTRACT FROM AUTHOR]

The article presents the discussion on contribution to innumerable learning and expanding the network of constructive meanings as a learning strategy. Topics include encompassing project planning and studying, applying the Ventsim software, and the design of a teaching laboratory with sensors and microcontrollers using the Internet of Things (IoT); and propose the creation of a modular underground mine ventilation laboratory to facilitate engineering teaching.

The Generalised Hoek-Brown (GHB) failure criterion is one of the most used criteria to study the behaviour of the rocks; affected parameters of the Hoek-Brown equation are Geological Strength Index (GSI), intact rock constant (mi), and Disturbance factor (D). GSI is one of the rock classification systems used to evaluate jointed rocks. In light of this equation, this paper studies the stability of unsupported twin tunnels in a weak rock by changing the mentioned parameters (GSI, mi) to find the relation between the stability and these parameters under different distances between the centres of the tunnels (L). The tunnels have a circular cross-section with a diameter (B), and they have been modelled in three dimensions using Rocscience software package (RS3). The results showed that the stability of the tunnels, which was represented by the strength reduction factor (SRF), increased as a result of increasing L/B or GSI in the studied range; for mi, the modelling results showed that the SRF value increased while mi value was increased. [ABSTRACT FROM AUTHOR]

The special large-slope V-shaped structure of underwater tunnels changes the ventilation characteristics during tunnel construction, making the traditional experience limited. Therefore, it is urgent to study the influence of the special structure on the safety of the air environment during construction. In this paper, a series of small-scale experiments were conducted to investigate the ventilation characteristics of V-shaped tunnels. The coupled effects of ventilation parameters (distance of duct outlet from working face  L 0 , air velocity at the duct outlet  u 0 ) and structural characteristics (digging length  L d , slope of the uphill section  θ) were considered. The extreme slope of the V-shaped tunnel of 8% was considered. The flow field and pollutant transport law were determined by using CO as a tracer in the experiments. The results show that  u 0  has a positive impact on the air return velocity, while  L d  has a negative impact, and neither of the other two factors has a significant effect. The transport characteristics of CO in V-shaped tunnels differ from those in flat tunnels, with the former tending to cause unconventional areas of high pollutant concentrations in the horizontal sections. Furthermore, the correlations between CO concentration and distance, ventilation time, and the influence factors discussed in this paper are derived from the experimental results. The conclusions provide guidance for the construction of V-shaped tunnels to prevent air pollution in the construction environment and to improve the working conditions of laborers. Additionally, it can also enrich the ventilation experience in tunnel construction. [ABSTRACT FROM AUTHOR]

In shield construction, the limit support pressure of the tunnel face has an important influence on ground settlement and construction safety. In this study, MIDAS GTS NX software was used to conduct a series of three-dimensional finite element simulations to investigate variations in excavation face support pressure under different layered ground conditions. By changing the shear strength parameters of the top or bottom layers, the influence of composite layers with different formation boundaries on the support pressure of the excavation face was studied. It was observed that when the formation boundary is placed above the axis, the support pressure of the excavation face is more sensitive to a change in the parameters in the lower part of the formation than in the upper part. Conversely, when the formation boundary lies below the axis, this sensitivity becomes reversed. Additionally, we derived a robust and accurate equation to estimate the limiting face support pressure in layered soft ground based on numerical modeling. [ABSTRACT FROM AUTHOR]

To characterize the failure of rock mass surrounding underground tunnels, biaxial compression tests were conducted on a real sandstone model with a straight-walled arched hole. The acoustic emission (AE) system and digital image correlation (DIC) optical inspection equipment were used to investigate the crack evolution process and failure precursors of the tunnel. A two-dimensional particle flow code (PFC2D) was used to conduct numerical simulations on the sample, so as to investigate the mesoscopic failure mechanism of rock mass. The results show that the failure of the single tunnel constructed in sandstone occurs mainly in the walls on both sides (between the spandrels and arch feet), showing slabbing failure characteristics and a certain abruptness. The crack initiation in sandstone in early stage is not obvious, and the crack propagation in rock mass is rapid when acoustic emissions are enhanced. The small increments in the AE count and amplitude and the continuous reduction in the b-value can be used as precursors for the failure of rock mass. When the height–span ratio is 0.8 and 1.0, the stress distribution around the chamber is more uniform, and when the height–span ratio is greater than 1.0, the stress is mainly concentrated in the vault and arch bottom. In the PFC simulations, tensile fractures firstly initiate in the middle of walls and at the arch feet, arcuate fracture concentration zones are then formed, in which shear fractures appear and a few particles spall from the surfaces. When approaching the ultimate bearing capacity, rock masses on both sides of the tunnel are fractured over large areas, and the slender coalesced fractured zone develops to the deep part of rock mass, causing failure of the sample. [ABSTRACT FROM AUTHOR]

Swelling of anhydrite rock causes serious damage to the tunnel and generates high additional costs in the process of tunnel construction and operation and has gradually become one of the main factors that threaten the safety of the tunnel. It is extremely difficult to predict swelling pressures and deformations accurately based on conventional swelling constitutive models. Thus, a new practical swelling constitutive model of anhydrite for tunnel engineering has been developed. First, swelling tests of natural anhydrite samples focusing on the time effect have been designed and conducted, whose test results show that swelling strain-time can be described by the S-curve model and that swelling stress-strain can be described by the quadratic model. Second, a swelling constitutive model with considering the time effect has been developed to reproduce the swelling behavior of anhydrite observed in swelling tests. This model can track the evolution of swelling activity in tunneling, which has practical significance for process simulation and process control of swelling disaster. Then, this model has been implemented within ANSYS for numerical simulation of the Lirang tunnel. Based on simulation results, useful measures have been proposed. Satisfactory results have been achieved according to the feedback from the site. [ABSTRACT FROM AUTHOR]

Featured Application: (1) A gas explosion simulation combining the chemical reaction mechanism and tunnel structure is described; (2) the shock wave flow fields in tunnels with uneven walls and smooth walls are compared; and (3) the dynamic responses in tunnels with uneven walls and smooth walls are analyzed. A numerical simulation method combining the detailed chemical reaction mechanism of methane deflagration with an approximate real tunnel structure was proposed to confirm whether the unevenness of the tunnel wall during a coal mine gas explosion can be ignored. The approximate real tunnel model and smooth wall tunnel model were developed using 3D modeling methods. The propagation and attenuation processes of shock waves in the two tunnel models, as well as the different dynamic responses of the two tunnel walls, were compared and analyzed. Research results show that the non-uniformity of the tunnel wall decreases the shock wave overpressure and propagation velocity. The peak overpressure reduction value of the shock wave reaches 81.91 kPa, and the shock wave overpressure reaches its peak at an extended maximum time of 7.4 ms. The stress distribution on the approximate real tunnel wall is discontinuous, the propagation speed of stress waves in the bend tunnel is slower, and the duration of high load is relatively low. The displacement of the approximate real tunnel after gas explosion is lower than that of tunnels with smooth walls, and the displacement of most measuring points on the tunnel on the right is only 1/3–1/2 that of the smooth tunnel. [ABSTRACT FROM AUTHOR]

Conventional data acquisition systems face challenges in achieving high acquisition speeds and rapid storage of large data volumes using microcontrollers. In contrast, field-programmable gate arrays (FPGAs) offer numerous advantages, including high clock frequencies, minimal internal delays, fast operational speeds, abundant internal RAM resources, and simplified control of complex peripheral circuits. This study presents the design of an FPGA-based multimedia remote monitoring system for information technology server rooms. The proposed system utilizes an FPGA as the primary controller and incorporates environmental sensors, electrical energy sensors, carbon monoxide sensors, smoke sensors, and A/D converter modules to monitor multiple locations within the server room. Simultaneously, the FPGA transmits the collected data from each monitoring point via a serial port to an LCD serial screen for display. An alarm is triggered if any environmental anomalies are detected, indicating abnormal statuses. Additionally, the system employs the fast Fourier transform algorithm and butterfly operations to derive voltage and current AC quantities, while utilizing relative temperature differences to identify equipment faults within the server room. The system is evaluated in terms of functionality, user-friendliness, and reliability. Experimental results demonstrate that all performance measures align with expectations, fulfilling the initial design objectives and highlighting the potential applicability and relevance of FPGA technology in the monitoring field. In addition, a comparison between FPGA and traditional microcontroller systems is performed, showcasing the superior processing speed and performance of the FPGA-based system. This comparative analysis further validates the advantages of using FPGA technology in high-speed data acquisition and monitoring applications. [ABSTRACT FROM AUTHOR]

In a long and narrow corridor, the installation of roof smoke blocking structures is a measure to slow down the spread of fire smoke. When employing multiple smoke blocking structures, the spacing between these structures is a critical parameter that needs to be considered for optimal effectiveness. This paper analyzes the smoke blocking performance of double structures at different spacing and measures the smoke flow velocity both upstream and downstream of the double structures. According to the analysis of the smoke velocity vector obtained from numerical simulation, the smoke can be divided into three zones based on the flow state of the smoke after passing through the front smoke screen structure, namely the vortex zone, surge wave zone, and steady flow zone. When the rear smoke screen is located in the surge zone, the smoke blocking effect is optimal. Analysis of the morphology of the smoke layer indicates that the length of the vortex region is directly proportional to the upstream smoke flow velocity. The numerical and experimental results both indicate that an excessively large or small spacing between the structures fails to achieve optimal smoke control effectiveness. When the spacing is within an optimal range, the smoke velocity is the lowest. Finally, using a real architectural corridor as a case background, this paper presents a design example of roof smoke blocking structures. In order to arrange as many smoke blocking structures as possible, an appropriate spacing between the structures should be slightly larger than the vortex region. The smoke control effectiveness of multiple roof structures was validated through numerical simulation. As a result, the time required for smoke to pass through the corridor increases by 110 s. [ABSTRACT FROM AUTHOR]

Fire is a major disaster event that can have a significant effect on public safety and social development. In a college or university, fire can seriously threaten the safety, lives, and property of those there due to the compact layout of apartment buildings and high population density. The ecological safety and sustainable development of buildings are also affected. In this study, PyroSim and Pathfinder software (version 2019) were used to simulate and analyze fire-spreading characteristics based on a multi-story university student apartment building. Additionally, the most effective safe evacuation plan from four fire evacuation drill schemes was identified by analyzing and comparing their performance. Results show that the spreading of fire smoke on different floors is significantly affected by the roof structure and the vertical and horizontal diffusion characteristics of smoke. While the smoke layer at the evacuation stairways has little effect on a safe evacuation, poor visibility due to smoke and ceiling temperatures has a significant effect. Safe evacuation becomes progressively more difficult at different floor levels from the top to the bottom of the building. The optimal safety scheme involves orderly evacuation through two open emergency exits. The number of emergency exits has a significant impact on the evacuation effectiveness. Measures and suggestions have been proposed to deal with apartment fires that address pre-event prevention, emergency loss reduction during the event, and post-event report-back. These proposals form an important theoretical reference for emergency evacuation and student apartment fire safety, providing important guidance for ecological safety protection of buildings and sustainable development. [ABSTRACT FROM AUTHOR]

Mortality from respiratory and cardiovascular health conditions contributes largely to the total mortality that has been associated with exposure to PM2.5 in epidemiology studies. A mode of action (MoA) for these underlying morbidities has not been established, but it has been proposed that some effects of PM2.5 occur through activation of neural reflexes. We critically reviewed the experimental studies of PM2.5 (including ambient PM2.5, diesel exhaust particles, concentrated ambient particles, diesel exhaust, and cigarette smoke) and neural reflex activation, and applied the principles of the International Programme on Chemical Safety (IPCS) MoA/human relevance framework to assess whether they support a biologically plausible and human-relevant MoA by which PM2.5 could contribute to cardiovascular and respiratory causes of death. We also considered whether the evidence from these studies supports a non-threshold MoA that operates at low, human-relevant PM2.5 exposure concentrations. We found that the proposed MoA of neural reflex activation is biologically plausible for PM2.5-induced respiratory effects at high exposure levels used in experimental studies, but further studies are needed to fill important data gaps regarding the relevance of this MoA to humans at lower PM2.5 exposure levels. A role for the proposed MoA in PM2.5-induced cardiovascular effects is plausible for some effects but not others. Further studies are needed to determine whether neural reflex activation is the MoA by which PM2.5 could cause either respiratory or cardiovascular morbidities in humans, particularly at the ambient concentrations associated with total mortality in epidemiology studies. [ABSTRACT FROM AUTHOR]

Agricultural centrifugal fans play a pivotal role in agricultural machinery, particularly in the context of combine harvesters. The performance of these fans significantly impacts the overall operational efficiency of the machine. Given the absence of robust performance testing and evaluation methodologies for agricultural centrifugal fans, this study assesses fan performance by examining the actual air–flow dynamics in a certain space at its outlet. Subsequently, the effects of various structural parameters on airflow smoothness and attenuation are investigated by computational fluid dynamics simulation analysis. The optimal detection air duct is developed, and the measured fan performance parameters and evaluation indexes are discussed and analysed using bench tests. The obtained results indicate that the arc connection section exhibits reduced interference with the air outlet of the agricultural centrifugal fan. Additionally, the attenuation section, characterised by a diffusion angle of 4°, effectively captures air attenuation properties. Minimal wind speed fluctuation is observed at the measuring point equidistant from the inlet and outlet of the steady flow section. Consequently, optimised structural parameters for the detection air duct and the specified location of the measuring point are determined. Furthermore, the performance parameters of the agricultural centrifugal fan are measured, and dimensional and dimensionless performance evaluation curves are generated based on bench testing. The fan's efficiency increases with higher air volume and flow coefficient but tends to change gradually due to the rate of increase, aligning with the expected performance of the agricultural centrifugal fan. The proposed performance detection device and evaluation method for agricultural cleaning can accurately detect the operational performance of the agricultural centrifugal fan. • A detection air duct for agricultural cleaning fans has been designed. • The variation and attenuation characteristics of airflow in air duct were obtained. • A parameter detection system for agricultural centrifugal fan was developed. • The measured performance parameters of the fan were visualised and evaluated. [ABSTRACT FROM AUTHOR]

The Influence of the Physical and Chemical Properties of Hardened Cement Paste on the Fire‐induced Spalling of Concrete A number of major fire incidents in recent decades, particularly in tunnels and indoor car parks, have increased the awareness among construction designers towards the potential susceptibility of concrete to fire‐induced explosive spalling. In some fields of application, this violent breaking‐off of concrete layers may reduce the fire resistance time of fire‐exposed construction elements. The mechanisms causing explosive spalling are not yet fully understood and discussed controversially among scientists.Fire tests of concrete specimens have shown that the type of cement may have a marked influence on the susceptibility of concrete to explosive spalling. Three common characteristics of those concretes that were found to have an increasedsusceptibility of spalling were identified. For each of the three common characteristics, acorresponding hypothesis describing its possible contribution to the fire‐induced concretespalling was proposed. This second part of the article describes the experiments to verify the hypotheses using a dedicated test programme. The evaluation of the tests identified the main mechanisms by which spalling is caused. [ABSTRACT FROM AUTHOR]

This study investigates the particle dispersion characteristics in the turbulent wake of a simplified vehicle model (Ahmed body) for two values of the rear slant angle ϕ (25 ° and 40 °) to study the effect of flow separation. In the experiments (Reynolds number Rel=1.90 × 10 5 ), smoke particles were released from a source and visualized with a laser sheet. Concentration fields were analyzed to calculate the vertical (Sy) and lateral (Sz) smoke spread. The findings indicate that the flow topology and concentration fields in the wake are highly dependent on ϕ. In the ϕ = 40 ° case, separation on the rear slant disrupts the trailing vortices originating on the rear slant edges and significantly alters the wake topology. The growth of vertical smoke spread saturates after the recirculation region. The uniform mixing and absence of trailing vortices concentrate the smoke particles in the model midplane. In the ϕ = 25 ° case, the signatures of trailing vortices were observed in the concentration fields behind the model. The vertical smoke spread is less, and the lateral smoke spread is more compared to the ϕ = 40 ° case. The growth of the smoke spread ( S y , S z ) driven by the trailing vortices persists for a long distance, even after the recirculation region. The disruption of trailing vortices brought about by the flow separation appears to be an important effect driving the vertical smoke spread in the wake. The connection between the turbulent velocity structures and concentration structures will need to be explored with combined velocity and concentration measurements in the wake. [ABSTRACT FROM AUTHOR]

With the rapid development of large‐capacity hydraulic turbines and pumped‐storage power stations, hydraulic vibration analysis attracts increasing attention nowadays. To explore the influence of torque and speed variation on hydraulic vibration characteristics during transient processes and ensure the stability of hydropower stations, an improved analytical formula of turbine impedance involving the torque and speed variation was then derived. The free vibration analysis and forced vibration analysis using the transfer matrix method and the hydraulic impedance method were carried out. According to the numerical simulations, the obtained attenuation factors show differences in magnitude which illustrates that the torque variation and speed variation in transients do affect the damping rate of the vibration. In addition, the results indicated the natural angular frequencies of hydropower system were mainly dependent on the length of water conveyance system and pipe characteristics. It can be inferred form vibration mode shapes that for some specific frequencies, the magnitude of oscillatory pressure head and flow rate along the downstream tail tunnel are influenced by the hydraulic turbine. The correlation between the turbine impedance and guide vane openings tells that the hydraulic impedance is getting smaller as the opening increases. What's more, the corresponding free vibration analysis shows that the absolute value of the damping rate is closely related to the value of the flow rate. [ABSTRACT FROM AUTHOR]

How to evaluate the reliability of deep soft rock tunnels under high stress is a very important problem to be solved. In this paper, we proposed a practical stochastic reliability method based on the third-generation non-dominated sorting genetic algorithm (NSGA–III) and eXtreme Gradient Boosting (XGBoost). The proposed method used the Latin hypercube sampling method to generate the dataset samples of geo-mechanical parameters and adopted XGBoost to establish the model of the nonlinear relationship between displacements and surrounding rock mechanical parameters. And NSGA–III was used to optimize the surrogate model hyper-parameters. Finally, the failure probability was computed by the optimized surrogate model. The proposed approach was firstly implemented in the analysis of a horseshoe-shaped highway tunnel to illustrate the efficiency of the approach. Then, in comparison to the support vector regression method and the back propagation neural network method, the feasibility, validity and advantages of XGBoost were demonstrated for practical problems. Using XGBoost to achieve Monte Carlo simulation, a surrogate solution can be provided for numerical simulation analysis to overcome the time-consuming reliability evaluation of initial support structures in soft rock tunnels. The proposed method can evaluate quickly the large deformation disaster risks of non-circular deep soft rock tunnels. [ABSTRACT FROM AUTHOR]

Currently, double-hole complementary ventilation is a mature ventilation method for operating tunnels, but how to carry out it in the construction tunnel poses a new challenge. Due to the desynchronization in the construction period of the double-hole tunnel, there is an instantaneous difference in the air flow demand between the two working faces. The study analyzes the impact of geometric parameters, specifically Lt (the distance from the traffic cross passage to the working face of the advance side tunnel), Lp (the distance between the pedestrian cross passage and the working face of the advance side tunnel), Ht (height of the upper step), and Lw (safe step distance of the double-hole working face) on ventilation network stability. The results show that with the increase of Lt and Lp, the Rm resistance of each branch changes non-uniformly, and the stability of the ventilation network is significantly different. Then, when Lt, Lp = 80 and 180 m, the air flow directions of the double-hole tunnel are the same. Finally, when Lt and Lp = 130 m, the air flow directions are inconsistent, which indicates that in the range of 80 m < Lt or Lp < 180 m, the cross-section size of the cross passage affects the stability of the ventilation network. However, when 2.5 m < Ht < 3 m, or 30 m < Lw < 50 m, the stability of the ventilation network is not affected, and the flow field of the double-holes does not interfere with each other. The conclusions obtained confirm that the double-hole complementary ventilation method is available in construction tunnels, and has potential for implementation. [ABSTRACT FROM AUTHOR]

During the drilling and blasting excavation of neighborhood tunnels, blast-induced vibrations negatively affect the stability of the interlaid rock, particularly for the following tunnel. This paper presents a case study of neighborhood tunnels with small clearance in Shenzhen, China, where the minimum thickness of interlaid rock is only 0.5 m. Therefore, the tunnelling method of the following tunnel should be precisely designed to ensure the safety of surrounding rock. Initially, we investigated the damage mechanism of the interlaid rock under the blasting load from the following tunnel using LS-DYNA R11.1 software. To control the damage of the interlaid rock caused by the following tunnel blasting, the four-part excavation method with a reserved vibration-cushioning layer for the following tunnel is proposed. Subsequently, the analytical stress of the surrounding rock for neighborhood tunnels was obtained by the Schwarz alternating method (SAM). By analyzing the variation patterns with different thicknesses of the cushioning layer, the optimal thickness of the cushioning layer was determined to be 3.0 m. Consequently, a safety excavation partition scheme was implemented for the following tunnel. As a result of this case study, suggestions were identified for the safe excavation of neighborhood tunnels with small clearance. [ABSTRACT FROM AUTHOR]

Investigating the construction mechanics of a ventilation tunnel using the TBM (Tunnel Boring Machine) pilot and enlargement method with reliable rock mechanics parameters ensures the safety of on-site excavation operations. Leveraging the construction project of the ventilation tunnel at the Wuhai Pumped Storage Power Station, TGP sidewall forecasting was employed to explore the geological conditions within a 50 m range of the tunnel's side. A systematic study of the construction mechanics of the TBM pilot and enlargement method was conducted, along with corresponding construction recommendations and engineering applications. This research indicates that sidewall forecasting can supplement the deficiencies in geological exploration reports, with excavation revealing conditions consistent with the forecast. Deformation at the interface, including the arch crown and sidewall, mainly concentrates during the construction phase from the completion of full-section excavation to the beginning of expansion. As the working face advances, the upper rock mass within the ventilation tunnel outline experiences tension, with stress concentration in the shoulder and bottom corner rock masses. The plastic zone before expansion primarily concentrates within the ventilation tunnel outline, shifting to the sidewall after expansion, with the left shoulder's plastic zone depth slightly exceeding that of the right. The proposed method effectively ensures construction safety, and the research findings have valuable implications for similar projects. [ABSTRACT FROM AUTHOR]

To address the current difficulties in fire detection algorithms, including inadequate feature extraction, excessive computational complexity, limited deployment on devices with limited resources, missed detections, inaccurate detections, and low accuracy, we developed a highly accurate algorithm named YOLOFM. We utilized LabelImg software to manually label a dataset containing 18644 images, named FM-VOC Dataset18644. In addition, we constructed a FocalNext network, which utilized the FocalNextBlock module from the CFnet network. This improves the integration of multi-scale information and reduces model parameters. We also proposed QAHARep-FPN, an FPN network that integrates the structure of quantization awareness and hardware awareness. This design effectively reduces redundant calculations of the model. A brand-new compression decoupled head, named NADH, was also created to enhance the correlation between the decoupling head structure and the calculation logic of the loss function. Instead of using the CIoU loss for bounding box regression, we proposed a Focal-SIoU loss. This promotes the swift convergence of the network and enhances the precision of the regression. The experimental results showed that YOLOFM improved the baseline network's accuracy, recall, F1, mAP50, and mAP50-95 by 3.1%, 3.9%, 3.0%, 2.2%, and 7.9%, respectively. It achieves an equilibrium that combines performance and speed, resulting in a more dependable and accurate solution for detection jobs. [ABSTRACT FROM AUTHOR]

The Baiyunshan tunnel of Chengdu-Zigong high-speed railway has a total length of 13 340 m. The ventilation problem of multi-work area and multi-stage construction of long high gas tunnel seriously restricts the tunnel operation and construction and personnel safety. The ventilation of different working areas was calculated through the maximum air volume, maximum air supply volume and air pressure loss along the way. The ventilation scheme of single working area and the overall tunneling sequence were designed. The water and air separation method was used to treat groundwater and the automatic safety monitoring system was used to monitor the gas concentration in the tunnel in real time. The analysis shows that during most of the construction time, the gas concentration of the 2# ~ 6# inclined shaft is low, which indicates that the reasonable ventilation scheme and the penetrating sequence of the working area can effectively reduce the gas concentration of the tunnel. The water gas separation method is used to treat the groundwater and discharge the groundwater and gas respectively, which can further reduce the gas concentration in the tunnel. The monitoring system timely alarms the abnormal gas emission of 2#, 3# and 6# inclined wells and power off protection, which ensures the progress of tunnel construction and personnel safety. A set of complete ventilation monitoring design method is established based on tunnel ventilation scheme, through sequence, water and gas separation treatment and gas monitoring for multi-area and multi-stage construction ventilation of long high gas tunnel to provide guidance for similar projects. [ABSTRACT FROM AUTHOR]

During the construction of a highway in northwest China, large deformation of mudstone caused severe deformation of and damage to side walls, initial support, and secondary lining to various extents. To reveal the causes of mudstone's large deformation in the tunnels of this highway, a comprehensive study was conducted by using engineering geological survey, on-site monitoring and measurement, indoor rock mechanics test, numerical simulation, and macroscopic analysis. For the problem of large deformation of this highway's tunnel section from YK209 + 500 m to YK210 + 030 m, the 3D finite difference method FLAC3D was used to simulate the large deformation of the wall rock and compare the deformation of the tunnel and the mechanical characteristics of the lining structure under different conditions by means of inverse analysis of the rheological characteristics of the mudstone and simulation of the softening of the mudstone in water. The research results provide a reference and basis for the construction design of similar mudstone tunnel projects. For the management of tunnel deformation, it is recommended to enhance the tunnel's drainage measures, thereby mitigating the intensification of mudstone softening when exposed to water. [ABSTRACT FROM AUTHOR]

Introduction: Humans and robots are increasingly collaborating on complex tasks such as firefighting. As robots are becoming more autonomous, collaboration in human-robot teams should be combined with meaningful human control. Variable autonomy approaches can ensure meaningful human control over robots by satisfying accountability, responsibility, and transparency. To verify whether variable autonomy approaches truly ensure meaningful human control, the concept should be operationalized to allow its measurement. So far, designers of variable autonomy approaches lack metrics to systematically address meaningful human control. Methods: Therefore, this qualitative focus group (n = 5 experts) explored quantitative operationalizations of meaningful human control during dynamic task allocation using variable autonomy in human-robot teams for firefighting. This variable autonomy approach requires dynamic allocation of moral decisions to humans and non-moral decisions to robots, using robot identification of moral sensitivity. We analyzed the data of the focus group using reflexive thematic analysis. Results: Results highlight the usefulness of quantifying the traceability requirement of meaningful human control, and how situation awareness and performance can be used to objectively measure aspects of the traceability requirement. Moreover, results emphasize that team and robot outcomes can be used to verify meaningful human control but that identifying reasons underlying these outcomes determines the level of meaningful human control. Discussion: Based on our results, we propose an evaluation method that can verify if dynamic task allocation using variable autonomy in humanrobot teams for firefighting ensures meaningful human control over the robot. This method involves subjectively and objectively quantifying traceability using human responses during and after simulations of the collaboration. In addition, the method involves semi-structured interviews after the simulation to identify reasons underlying outcomes and suggestions to improve the variable autonomy approach. [ABSTRACT FROM AUTHOR]

Determining fire source in underground commercial street fires is critical for fire analysis. This paper proposes a method based on temperature and machine learning to determine information about fire source in underground commercial street fires. Data was obtained through consolidated fire and smoke transport (CFAST) software, and a fire database was established based on the sampling to ascertain fire scenarios. Temperature time series were chosen for feature processing, and three machine learning models for fire source determination were established: decision tree, random forest, and LightGBM. The results indicated that the trained models can determine fire source information based on processed features, achieving a precision exceeding 95%. Among these, the LightGBM model exhibited superior performance, with macro averages of precision, recall, and F1 score being 99.01%, 98.45%, and 99.04%, respectively, and a kappa value of 98.81%. The proposed method for determining the fire source provides technical support for grasping the fire situation in underground commercial streets and has good application prospects. [ABSTRACT FROM AUTHOR]

Simple Summary: The aim of this review is to provide researchers with a guide to simulating the environment of poultry houses using computational fluid dynamics. Through an extensive review of the literature in this area, it provides comprehensive insights into the common challenges encountered when applying this method, as well as a discussion of planned future research efforts. In recent years, computational fluid dynamics (CFD) has become increasingly important and has proven to be an effective method for assessing environmental conditions in poultry houses. CFD offers simplicity, efficiency, and rapidity in assessing and optimizing poultry house environments, thereby fueling greater interest in its application. This article aims to facilitate researchers in their search for relevant CFD studies in poultry housing environmental conditions by providing an in-depth review of the latest advancements in this field. It has been found that CFD has been widely employed to study and analyze various aspects of poultry house ventilation and air quality under the following five main headings: inlet and fan configuration, ventilation system design, air temperature–humidity distribution, airflow distribution, and particle matter and gas emission. The most commonly used turbulence models in poultry buildings are the standard k-ε, renormalization group (RNG) k-ε, and realizable k-ε models. Additionally, this article presents key solutions with a summary and visualization of fundamental approaches employed in addressing path planning problems within the CFD process. Furthermore, potential challenges, such as data acquisition, validation, computational resource requirements, meshing, and the selection of a proper turbulence model, are discussed, and avenues for future research (the integration of machine learning, building information modeling, and feedback control systems with CFD) are explored. [ABSTRACT FROM AUTHOR]

Recent observations of tree regeneration failures following large and severe disturbances, particularly under warm and dry conditions, have raised concerns about the resilience of forest ecosystems and their recovery dynamics in the face of climate change. We investigated the recovery of temperate forests in Europe after large and severe disturbance events (i.e., resulting in more than 70% canopy loss in patches larger than 1 ha), with a range of one to five decades since the disturbance occurred. The study included 143 sites of different forest types and management practices that had experienced 28 disturbance events, including windthrow (132 sites), fire (six sites), and bark beetle outbreaks (five sites). We focused on assessing post‐disturbance tree density, structure, and composition as key indicators of forest resilience. We compared post‐disturbance height‐weighted densities with site‐specific pre‐disturbance densities to qualitatively assess the potential for structural and compositional recovery, overall and for dominant tree species, respectively. Additionally, we analyzed the ecological drivers of post‐windthrow tree density, such as forest management, topography, and post‐disturbance aridity, using a series of generalized additive models. The descriptive results show that European temperate forests have been resilient to past large and severe disturbances and concurrent climate conditions, albeit with lower resilience to high‐severity fire compared with other disturbance agents. Across sites and disturbance agents, the potential for structural recovery was greater than that of compositional recovery, with a large proportion of plots becoming dominated by early‐successional species after disturbance. The models showed that increasing elevation and salvage logging negatively affect post‐windthrow regeneration, particularly for late‐successional species, while pioneer species are negatively affected by increasing summer aridity. These findings provide a key baseline for assessing future recovery and resilience following the recent occurrence of widespread disturbance in the region and in anticipation of future conditions characterized by increasing heat and drought stress. [ABSTRACT FROM AUTHOR]