To understand the smoke level and NO_(x)emission characteristics of in-use construction machinery in Beijing,we selected 905 construction machines in Beijing from August 2022 to April 2023 to monitor the emission leve...To understand the smoke level and NO_(x)emission characteristics of in-use construction machinery in Beijing,we selected 905 construction machines in Beijing from August 2022 to April 2023 to monitor the emission level of smoke and NO_(x).The exhaust smoke level and excessive emission situation of different machinery types were identified,and their NO_(x)emission levels were monitored according to the free acceleration method.We investigated the correlation of NO_(x)and smoke emission,and proposed suggestions for controlling pollution discharge from construction machinery in the future.The results show that the exhaust smoke level was 0–2.62 m^(−1),followed a log-normal distribution(μ=-1.73,δ=1.09,R^(2)=0.99),with a 5.64%exceedance rate.Differenceswere observed amongmachinery types,with low-power engine forklifts showing higher smoke levels.The NO_(x)emission range was 71–1516 ppm,followed a normal distribution(μ=565.54,δ=309.51,R^(2)=0.83).Differences among machinery types were relatively small.Engine rated net power had the most significant impact on NO_(x)emissions.Thus,NO_(x)emissions from construction machinery need further attention.Furthermore,we found a weak negative correlation(p<0.05)between the emission level of smoke and NO_(x),that is the synergic emission reduction effect is poor,emphasizing the need for NO_(x)emission limits.In the future,the oversight in Beijing should prioritize phasing out ChinaⅠand ChinaⅡmachinery,and monitor emissions from highpower engine ChinaⅢmachinery.展开更多
To improve the catalytic performance of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3)(LSCF)towards carbon soot,we utilized the impregnation method to incorporate Ag into the prepared LSCF catalyst.We conducted a series of cha...To improve the catalytic performance of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3)(LSCF)towards carbon soot,we utilized the impregnation method to incorporate Ag into the prepared LSCF catalyst.We conducted a series of characterization tests and evaluated the soot catalytic activity of the composite catalyst by comparing it with the LaCoO_(3) group,LaFeO_(3) group,and catalyst-free group.The results indicate that the Ag-LSCF composite catalyst exhibits the highest soot catalytic activity,with the characteristic temperature values of 376.3,431.1,and 473.9℃at 10%,50%,and 90%carbon soot conversion,respectively.These values are 24.8,20.2,and 23.1℃lower than those of the LSCF group.This also shows that LSCF can improve the catalytic activity of soot after compounding with Ag,and reflects the necessity of using catalysts in soot combustion reaction.XPS characterization and BET test show that Ag-LSCF has more abundant surface-adsorbed oxygen species,larger specific surface area and pore volume than LSCF,which also proves that Ag-LSCF has higher soot catalytic activity.展开更多
BACKGROUND Smoking is a leading cause of carcinogenesis in the head and neck region,representing a critical public health issue.Identifying genotoxic damage in smokers can provide valuable insights for developing prev...BACKGROUND Smoking is a leading cause of carcinogenesis in the head and neck region,representing a critical public health issue.Identifying genotoxic damage in smokers can provide valuable insights for developing preventive interventions.AIM To assess genotoxic damage through the micronucleus assay in exfoliated buccal mucosa cells from users of conventional tobacco,reverse smoking,cannabis,electronic cigarettes,and non-smokers.METHODS A cross-sectional study was conducted with 100 participants divided into five groups:20 conventional tobacco smokers,20 reverse smokers,20 electronic cigarette users,20 cannabis users,and 20 non-smokers.Exfoliated buccal mucosa cells were analyzed using Giemsa and Papanicolaou staining to identify micronuclei(MN)as markers of genotoxic damage.RESULTS MN were present in 86%of the samples.Statistically significant differences were observed in the median micronucleus count between conventional,reverse,and electronic cigarette smokers compared to non-smokers(P<0.001),while no significant difference was found for cannabis smokers(P=0.89).A significant correlation was identified between the presence of oral lesions and micronucleus count(P=0.03).Regression analysis ruled out alcohol as a confounding factor.CONCLUSION This study identified genotoxic damage associated with various smoking habits,except for cannabis use,highlighting the need for public health interventions to reduce smoking and mitigate its genotoxic effects.These findings provide a foundation for future research and the implementation of preventive policies.展开更多
In rapid urban development,outdoor parking lots have become essential components of urban transportation systems.However,the increasing number of parking lots is accompanied by a rising risk of vehicle fires,posing a ...In rapid urban development,outdoor parking lots have become essential components of urban transportation systems.However,the increasing number of parking lots is accompanied by a rising risk of vehicle fires,posing a serious challenge to public safety.As a result,there is a critical need for fire warning systems tailored to outdoor parking lots.Traditional smoke detection methods,however,struggle with the complex outdoor environment,where smoke characteristics often blend into the background,resulting in low detection efficiency and accuracy.To address these issues,this paper introduces a novel model named Dynamic Contextual Transformer YOLO(DCT-YOLO),an advanced smoke detection method specifically designed for outdoor parking lots.We introduce an innovative Dynamic Channel-Spatial Attention(DCSA)mechanism to improve the model’s focus on smoke features,thus improving detection accuracy.Additionally,we incorporate Contextual Transformer Networks(CoTNet)to better adapt to the irregularity of smoke patterns,further enhancing the accuracy of smoke region detection in complex environments.Moreover,we developed a new dataset that includes a wide range of smoke and fire scenarios,improving the model’s generalization capability.All baseline models were trained and evaluated on the same dataset to ensure a fair and consistent comparison.The experimental results on this dataset demonstrate that the proposed algorithm yields a mAP@0.5 of 85.1%and a mAP@0.5:0.95 of 55.7%,representing improvements of 15.0%and 14.9%,respectively,over the baseline model.These results highlight the effectiveness of the proposed method in accurately detecting smoke in challenging outdoor environments.展开更多
The corrosion behavior and life of Sn−3.0Ag−0.5Cu solder joints were investigated through fire smoke exposure experiments within the temperature range of 45−80℃.The nonlinear Wiener process and Arrhenius equation wer...The corrosion behavior and life of Sn−3.0Ag−0.5Cu solder joints were investigated through fire smoke exposure experiments within the temperature range of 45−80℃.The nonlinear Wiener process and Arrhenius equation were used to establish the probability distribution function and prediction model of the solder joint’s average life and individual remaining useful life.The results indicate that solder joint resistance shows a nonlinear growth trend with time increasing.After 24 h,the solder joint transforms from spherical to rose-like shapes.Higher temperatures accelerate solder joint failure,and the relationship between failure time and temperature conforms to the Arrhenius equation.The predicted life of the model is in good agreement with experimental results,demonstrating the effectiveness and accuracy of the model.展开更多
With rapid urbanization,fires pose significant challenges in urban governance.Traditional fire detection methods often struggle to detect smoke in complex urban scenes due to environmental interferences and variations...With rapid urbanization,fires pose significant challenges in urban governance.Traditional fire detection methods often struggle to detect smoke in complex urban scenes due to environmental interferences and variations in viewing angles.This study proposes a novel multimodal smoke detection method that fuses infrared and visible imagery using a transformer-based deep learning model.By capturing both thermal and visual cues,our approach significantly enhances the accuracy and robustness of smoke detection in business parks scenes.We first established a dual-view dataset comprising infrared and visible light videos,implemented an innovative image feature fusion strategy,and designed a deep learning model based on the transformer architecture and attention mechanism for smoke classification.Experimental results demonstrate that our method outperforms existing methods,under the condition of multi-view input,it achieves an accuracy rate of 90.88%,precision rate of 98.38%,recall rate of 92.41%and false positive and false negative rates both below 5%,underlining the effectiveness of the proposed multimodal and multi-view fusion approach.The attention mechanism plays a crucial role in improving detection performance,particularly in identifying subtle smoke features.展开更多
Poly(vinyl chloride)(PVC)materials are produced with high smoke and toxic gases during combustion,when commercial flame-retardant additives are incorporated.Here,rare-earth yttrium stannate(Y_(2)Sn_(2)O_(7)),which is ...Poly(vinyl chloride)(PVC)materials are produced with high smoke and toxic gases during combustion,when commercial flame-retardant additives are incorporated.Here,rare-earth yttrium stannate(Y_(2)Sn_(2)O_(7)),which is superior to commercial flame retardants,was designed to enhance the smoke suppression and toxicity reduction performance of PVC materials without damaging their mechanical properties.After the addition of 15 wt%Y_(2)Sn_(2)O_(7)(PVC/Y_(2)Sn_(2)O_(7)),the PVC composites achieved a V-0 rating,whereas the pure PVC material achieved a V-2 rating.The peak heat release rate of PVC/Y_(2)Sn_(2)O_(7) composite was reduced from 282.7 kW/m^(2)(pure PVC)to 243.6 kW/m^(2).In addition,the maximum smoke density(Ds-max)of PVC/Y_(2)Sn_(2)O_(7) was 263 m^(2)/m^(2),a decrease of 48.5%compared to pure PVC materials(511 m^(2)/m^(2)),indicating its outstanding ability for smoke suppression.Compared to Sb_(2)O_(3),Y_(2)Sn_(2)O_(7) can effectively reduce the release of the toxic gas CO(decreasing by 37.5%).Furthermore,the tensile strength of PVC can reach as high as 16.1 MPa.Compared with five widely used commercial flame retardants,Y_(2)Sn_(2)O_(7) demonstrates superior performance,positioning it as a promising alternative to prospective candidates.Therefore,this study developed a rare-earth flame retardant and offers a promising design to improve the fire safety of PVC composites.展开更多
This study proposes a multi-scene smoke detection algorithm based on a multi-feature extraction method to address the problems of varying smoke shapes in different scenes,difficulty in locating and detecting transluce...This study proposes a multi-scene smoke detection algorithm based on a multi-feature extraction method to address the problems of varying smoke shapes in different scenes,difficulty in locating and detecting translucent smoke,and variable smoke scales.First,the convolution module of feature extraction in YOLOv5s backbone network is replaced with asymmetric convolution block re-parameterization convolution to improve the detection of different shapes of smoke.Then,coordinate attention mechanism is introduced in the deeper layer of the backbone network to further improve the localization of translucent smoke.Finally,the detection of smoke at different scales is further improved by using the feature pyramid convolution module instead of the standard convolution module of the feature pyramid in the model.The experimental results demonstrate the feasibility and superiority of the proposed model for multi-scene smoke detection.展开更多
Atrium spaces,common in modern construction,provide significant fire safety challenges due to their large vertical openings,which facilitate rapid smoke spread and reduce sprinkler effectiveness.Traditional smoke mana...Atrium spaces,common in modern construction,provide significant fire safety challenges due to their large vertical openings,which facilitate rapid smoke spread and reduce sprinkler effectiveness.Traditional smoke management systems primarily rely on make-up air to replace the air expelled through vents.Inadequate calibration,particularly with air velocity,can worsen fire conditions by enhancing oxygen supply,increasing soot production,and reducing visibility,so endangering safe evacuation.This study investigates the impact of make-up air velocity on smoke behaviour in atrium environments through 24 simulations performed using the FireDynamics Simulator(FDS).Scenarios include various fire intensities(1,3,5 MW)and make-up air velocities(1–3.5 m/s),with fire sources located at the centre,northeast,and southwest corners.The simulation model was validated using updated full-scale fire test data with polystyrene fuel,leading to heightened soot density and reduced smoke clear height.This Research design diverges from other studies that predominantly utilized propane pool fires and concentrated on axisymmetric(Fire at the center of the atrum),Northeast and Southeast corners of the atrium scenarios by using polystyrene-a widely accessible construction material and examining several asymetric fire sites,so providing a more authentic depiction of atrium fire settings.Research reveals that increased air velocities,especially when directed at the fire,result in greater soot density and reduced smoke clearance due to intensified combustion.The northeastern region consistently displayed high temperature readings,highlighting the importance of fire source positioning in smoke behaviour.The study recommends limiting make-up air velocity to 1 m/s to avert turbulence and guarantee safety.This research provides critical insights for fire safety design and aligns with the United Nations Sustainable Development Goals,namely SDG 9 and SDG 11,by promoting safer and more resilient construction practices in urban environments.展开更多
The present study monitored bacterial succession,physicochemical properties,and volatile organic compounds(VOCs)changes in smoked chicken legs with modified atmosphere packaging(MAP,60% CO_(2) and 40%N_(2))during a 25...The present study monitored bacterial succession,physicochemical properties,and volatile organic compounds(VOCs)changes in smoked chicken legs with modified atmosphere packaging(MAP,60% CO_(2) and 40%N_(2))during a 25-day storage period at 4℃.After 15 days of storage,S erratia proteamaculans and Pseudomonas fragi became the predominant bacteria.Furthermore,physicochemical properties changed significantly,as evidenced by an increase in thiobarbituric acid reactive substances and b*(yellowness)value,and a decrease in hardness.A total of 65 VOCs were identified during storage.Correlation between bacterial succession and quality indicators(including VOCs and physicochemical properties)allowed the identification of 26 core dominant bacteria,including S.proteamaculans,Psychrobacter alimentarius,Pseudomonas putida,and Pseudomonas poae,which were positively related to spoilage VOCs(e.g.,1-octen-3-ol,1-pentanol,and 3-methyl-1-butanol)and could be defined as specific spoilage organisms(SSOs).The results of this study provide a systematic approach to predict SSOs in smoked chicken legs during storage,which can also provide a basis for product safety.展开更多
Objective Cigarette smoking exacerbates the progression of pulmonary tuberculosis(TB).The role of tertiary lymphoid structures(TLS)in chronic lung diseases has gained attention;however,it remains unclear whether smoki...Objective Cigarette smoking exacerbates the progression of pulmonary tuberculosis(TB).The role of tertiary lymphoid structures(TLS)in chronic lung diseases has gained attention;however,it remains unclear whether smoking-exacerbated lung damage in TB is associated with TLS.This study aimed to analyze the characteristics of pulmonary TLS in smokers with TB and to explore the possible role of TLS in smoking-related lung injury in TB.Methods Lung tissues from 36 male patients(18 smokers and 18 non-smokers)who underwent surgical resection for pulmonary TB were included in this study.Pathological and immunohistological analyses were conducted to evaluate the quantity of TLS,and chest computed tomography(CT)was used to assess the severity of lung lesions.The correlation between the TLS quantity and TB lesion severity scores was analyzed.The immune cells and chemokines involved in TLS formation were also evaluated and compared between smokers and non-smokers.Results Smoker patients with TB had significantly higher TLS than non-smokers(P<0.001).The TLS quantity in both the lung parenchyma and peribronchial regions correlated with TB lesion severity on chest CT(parenchyma:r=0.5767;peribronchial:r=0.7373;both P<0.001).Immunohistochemical analysis showed increased B cells,T cells,and C-X-C motif chemokine ligand 13(CXCL13)expression in smoker patients with TB(P<0.001).Conclusion Smoker TB patients exhibited increased pulmonary TLS,which was associated with exacerbated lung lesions on chest CT,suggesting that cigarette smoking may exacerbate lung damage by promoting TLS formation.展开更多
Fire detection has held stringent importance in computer vision for over half a century.The development of early fire detection strategies is pivotal to the realization of safe and smart cities,inhabitable in the futu...Fire detection has held stringent importance in computer vision for over half a century.The development of early fire detection strategies is pivotal to the realization of safe and smart cities,inhabitable in the future.However,the development of optimal fire and smoke detection models is hindered by limitations like publicly available datasets,lack of diversity,and class imbalance.In this work,we explore the possible ways forward to overcome these challenges posed by available datasets.We study the impact of a class-balanced dataset to improve the fire detection capability of state-of-the-art(SOTA)vision-based models and propose the use of generative models for data augmentation,as a future work direction.First,a comparative analysis of two prominent object detection architectures,You Only Look Once version 7(YOLOv7)and YOLOv8 has been carried out using a balanced dataset,where both models have been evaluated across various evaluation metrics including precision,recall,and mean Average Precision(mAP).The results are compared to other recent fire detection models,highlighting the superior performance and efficiency of the proposed YOLOv8 architecture as trained on our balanced dataset.Next,a fractal dimension analysis gives a deeper insight into the repetition of patterns in fire,and the effectiveness of the results has been demonstrated by a windowing-based inference approach.The proposed Slicing-Aided Hyper Inference(SAHI)improves the fire and smoke detection capability of YOLOv8 for real-life applications with a significantly improved mAP performance over a strict confidence threshold.YOLOv8 with SAHI inference gives a mAP:50-95 improvement of more than 25%compared to the base YOLOv8 model.The study also provides insights into future work direction by exploring the potential of generative models like deep convolutional generative adversarial network(DCGAN)and diffusion models like stable diffusion,for data augmentation.展开更多
The smoke spreading law of urban transportation tunnels with multiple shafts under natural ventilation is studied.A full-scale burning experiment is conducted in an actual tunnel.The study shows that smoke temperature...The smoke spreading law of urban transportation tunnels with multiple shafts under natural ventilation is studied.A full-scale burning experiment is conducted in an actual tunnel.The study shows that smoke temperatures below the tunnel ceiling reduce rapidly along the longitudinal towards the tunnel exits. A noticeable temperature stratification is observed near the fire source.Most fire smoke is exhausted out of the shafts while the number of the smoke shafts in the downstream is more than that in the upstream.Large eddy simulation LES based on computational fluid dynamics CFD is carried out using the fire dynamics simulator FDS software with parallel processing in which the grid size of the fire-domain is set to be 0.083 m.The simulation results of temperatures under the ceiling the smoke fronts and the shafts＇smoke exhaust or air supply agree reasonably with the experimental data. Further simulations indicate that the decreasing ambient temperature or shaft spacing might reduce smoke temperatures under the tunnel ceiling and increase mass flow rates out of the shafts.This study provides technical scientific evidence and supports for the design and construction of such kinds of tunnels.展开更多
Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tra...Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tracers.This study comprehensively investigates chemical composition of PM_(2.5),including both inorganic and organic compounds throughout haze and post-haze periods in 2019 at a rural site of Northern Thailand.Average PM_(2.5) concentrations during haze and post-haze period were 87±36 and 21±11μg/m^(3),respectively.Organic matter was the dominant contributor in PM_(2.5) mass,followed by water soluble inorganic ions and mineral dust.Molecular markers,including levoglucosan,dehydroabietic acid,and 4-nitrocatechol,and ions(Cl^(-),and K^(+)),were used to characterize low haze(PM_(2.5)<100μg/m^(3))and episodic haze(PM_(2.5)>100μg/m^(3)).Low haze is associated with local aerosols from agricultural waste burning,while episodic haze is linked to aged aerosols from mixed agricultural waste,softwood,and hardwood burning.Source apportionment incorporating these molecular markers in receptor modelling(Positive matrix factorization),identified three distinct biomass burning sources:mixed,local,and aged biomass burnings,contributing 31,19 and 13%of PM_(2.5) during haze period.During post-haze period,contributions shifted,with local biomass burning(32%)comparable to secondary sulfate(34%)and mixed dust and traffic sources(26%).These findings demonstrate that both regional and local sources con-tribute to severe haze,highlighting the need for integrated policies for cross-border cooperation as well as stricter regulations to reduce biomass burning in Northern Thailand and Southeast Asia.展开更多
基金supported by the Energy Foundation(No.G-2203-33693).
文摘To understand the smoke level and NO_(x)emission characteristics of in-use construction machinery in Beijing,we selected 905 construction machines in Beijing from August 2022 to April 2023 to monitor the emission level of smoke and NO_(x).The exhaust smoke level and excessive emission situation of different machinery types were identified,and their NO_(x)emission levels were monitored according to the free acceleration method.We investigated the correlation of NO_(x)and smoke emission,and proposed suggestions for controlling pollution discharge from construction machinery in the future.The results show that the exhaust smoke level was 0–2.62 m^(−1),followed a log-normal distribution(μ=-1.73,δ=1.09,R^(2)=0.99),with a 5.64%exceedance rate.Differenceswere observed amongmachinery types,with low-power engine forklifts showing higher smoke levels.The NO_(x)emission range was 71–1516 ppm,followed a normal distribution(μ=565.54,δ=309.51,R^(2)=0.83).Differences among machinery types were relatively small.Engine rated net power had the most significant impact on NO_(x)emissions.Thus,NO_(x)emissions from construction machinery need further attention.Furthermore,we found a weak negative correlation(p<0.05)between the emission level of smoke and NO_(x),that is the synergic emission reduction effect is poor,emphasizing the need for NO_(x)emission limits.In the future,the oversight in Beijing should prioritize phasing out ChinaⅠand ChinaⅡmachinery,and monitor emissions from highpower engine ChinaⅢmachinery.
文摘To improve the catalytic performance of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3)(LSCF)towards carbon soot,we utilized the impregnation method to incorporate Ag into the prepared LSCF catalyst.We conducted a series of characterization tests and evaluated the soot catalytic activity of the composite catalyst by comparing it with the LaCoO_(3) group,LaFeO_(3) group,and catalyst-free group.The results indicate that the Ag-LSCF composite catalyst exhibits the highest soot catalytic activity,with the characteristic temperature values of 376.3,431.1,and 473.9℃at 10%,50%,and 90%carbon soot conversion,respectively.These values are 24.8,20.2,and 23.1℃lower than those of the LSCF group.This also shows that LSCF can improve the catalytic activity of soot after compounding with Ag,and reflects the necessity of using catalysts in soot combustion reaction.XPS characterization and BET test show that Ag-LSCF has more abundant surface-adsorbed oxygen species,larger specific surface area and pore volume than LSCF,which also proves that Ag-LSCF has higher soot catalytic activity.
文摘BACKGROUND Smoking is a leading cause of carcinogenesis in the head and neck region,representing a critical public health issue.Identifying genotoxic damage in smokers can provide valuable insights for developing preventive interventions.AIM To assess genotoxic damage through the micronucleus assay in exfoliated buccal mucosa cells from users of conventional tobacco,reverse smoking,cannabis,electronic cigarettes,and non-smokers.METHODS A cross-sectional study was conducted with 100 participants divided into five groups:20 conventional tobacco smokers,20 reverse smokers,20 electronic cigarette users,20 cannabis users,and 20 non-smokers.Exfoliated buccal mucosa cells were analyzed using Giemsa and Papanicolaou staining to identify micronuclei(MN)as markers of genotoxic damage.RESULTS MN were present in 86%of the samples.Statistically significant differences were observed in the median micronucleus count between conventional,reverse,and electronic cigarette smokers compared to non-smokers(P<0.001),while no significant difference was found for cannabis smokers(P=0.89).A significant correlation was identified between the presence of oral lesions and micronucleus count(P=0.03).Regression analysis ruled out alcohol as a confounding factor.CONCLUSION This study identified genotoxic damage associated with various smoking habits,except for cannabis use,highlighting the need for public health interventions to reduce smoking and mitigate its genotoxic effects.These findings provide a foundation for future research and the implementation of preventive policies.
基金supported by the Major Scientific and Technological Special Project of Guizhou Province([2024]014).
文摘In rapid urban development,outdoor parking lots have become essential components of urban transportation systems.However,the increasing number of parking lots is accompanied by a rising risk of vehicle fires,posing a serious challenge to public safety.As a result,there is a critical need for fire warning systems tailored to outdoor parking lots.Traditional smoke detection methods,however,struggle with the complex outdoor environment,where smoke characteristics often blend into the background,resulting in low detection efficiency and accuracy.To address these issues,this paper introduces a novel model named Dynamic Contextual Transformer YOLO(DCT-YOLO),an advanced smoke detection method specifically designed for outdoor parking lots.We introduce an innovative Dynamic Channel-Spatial Attention(DCSA)mechanism to improve the model’s focus on smoke features,thus improving detection accuracy.Additionally,we incorporate Contextual Transformer Networks(CoTNet)to better adapt to the irregularity of smoke patterns,further enhancing the accuracy of smoke region detection in complex environments.Moreover,we developed a new dataset that includes a wide range of smoke and fire scenarios,improving the model’s generalization capability.All baseline models were trained and evaluated on the same dataset to ensure a fair and consistent comparison.The experimental results on this dataset demonstrate that the proposed algorithm yields a mAP@0.5 of 85.1%and a mAP@0.5:0.95 of 55.7%,representing improvements of 15.0%and 14.9%,respectively,over the baseline model.These results highlight the effectiveness of the proposed method in accurately detecting smoke in challenging outdoor environments.
基金National Natural Science Foundation of China (No. 52206180)Fundamental Research Funds for the Central Universities,China (No. WK2320000050)。
文摘The corrosion behavior and life of Sn−3.0Ag−0.5Cu solder joints were investigated through fire smoke exposure experiments within the temperature range of 45−80℃.The nonlinear Wiener process and Arrhenius equation were used to establish the probability distribution function and prediction model of the solder joint’s average life and individual remaining useful life.The results indicate that solder joint resistance shows a nonlinear growth trend with time increasing.After 24 h,the solder joint transforms from spherical to rose-like shapes.Higher temperatures accelerate solder joint failure,and the relationship between failure time and temperature conforms to the Arrhenius equation.The predicted life of the model is in good agreement with experimental results,demonstrating the effectiveness and accuracy of the model.
基金supported by the National Natural Science Foundation of China(32171797)Chunhui Project Foundation of the Education Department of China(HZKY20220026).
文摘With rapid urbanization,fires pose significant challenges in urban governance.Traditional fire detection methods often struggle to detect smoke in complex urban scenes due to environmental interferences and variations in viewing angles.This study proposes a novel multimodal smoke detection method that fuses infrared and visible imagery using a transformer-based deep learning model.By capturing both thermal and visual cues,our approach significantly enhances the accuracy and robustness of smoke detection in business parks scenes.We first established a dual-view dataset comprising infrared and visible light videos,implemented an innovative image feature fusion strategy,and designed a deep learning model based on the transformer architecture and attention mechanism for smoke classification.Experimental results demonstrate that our method outperforms existing methods,under the condition of multi-view input,it achieves an accuracy rate of 90.88%,precision rate of 98.38%,recall rate of 92.41%and false positive and false negative rates both below 5%,underlining the effectiveness of the proposed multimodal and multi-view fusion approach.The attention mechanism plays a crucial role in improving detection performance,particularly in identifying subtle smoke features.
基金financially supported by the Science and Technology Breakthrough Project of Inner Mongolia(Nos.2024KJTW0006 and 2023B2551)Central Guiding Science and Technology Development Fund of Inner Mongolia(No.2022ZY0100)+3 种基金Natural Science Foundation of Anhui Province(No.2408085ME140)National Key Laboratory of Baiyunobo Rare Earth Resource Research and Comprehensive UtilizationExperimental Center of Engineering and Material Science from the University of Science and Technology of ChinaInstruments Center for Physical Science,University of Science and Technology of China。
文摘Poly(vinyl chloride)(PVC)materials are produced with high smoke and toxic gases during combustion,when commercial flame-retardant additives are incorporated.Here,rare-earth yttrium stannate(Y_(2)Sn_(2)O_(7)),which is superior to commercial flame retardants,was designed to enhance the smoke suppression and toxicity reduction performance of PVC materials without damaging their mechanical properties.After the addition of 15 wt%Y_(2)Sn_(2)O_(7)(PVC/Y_(2)Sn_(2)O_(7)),the PVC composites achieved a V-0 rating,whereas the pure PVC material achieved a V-2 rating.The peak heat release rate of PVC/Y_(2)Sn_(2)O_(7) composite was reduced from 282.7 kW/m^(2)(pure PVC)to 243.6 kW/m^(2).In addition,the maximum smoke density(Ds-max)of PVC/Y_(2)Sn_(2)O_(7) was 263 m^(2)/m^(2),a decrease of 48.5%compared to pure PVC materials(511 m^(2)/m^(2)),indicating its outstanding ability for smoke suppression.Compared to Sb_(2)O_(3),Y_(2)Sn_(2)O_(7) can effectively reduce the release of the toxic gas CO(decreasing by 37.5%).Furthermore,the tensile strength of PVC can reach as high as 16.1 MPa.Compared with five widely used commercial flame retardants,Y_(2)Sn_(2)O_(7) demonstrates superior performance,positioning it as a promising alternative to prospective candidates.Therefore,this study developed a rare-earth flame retardant and offers a promising design to improve the fire safety of PVC composites.
基金the Natural Science Foundation of Zhejiang Province(Nos.LY20F020015 and LY21F020015)the National Natural Science Foundation of China(Nos.61972121 and 61902099)。
文摘This study proposes a multi-scene smoke detection algorithm based on a multi-feature extraction method to address the problems of varying smoke shapes in different scenes,difficulty in locating and detecting translucent smoke,and variable smoke scales.First,the convolution module of feature extraction in YOLOv5s backbone network is replaced with asymmetric convolution block re-parameterization convolution to improve the detection of different shapes of smoke.Then,coordinate attention mechanism is introduced in the deeper layer of the backbone network to further improve the localization of translucent smoke.Finally,the detection of smoke at different scales is further improved by using the feature pyramid convolution module instead of the standard convolution module of the feature pyramid in the model.The experimental results demonstrate the feasibility and superiority of the proposed model for multi-scene smoke detection.
文摘Atrium spaces,common in modern construction,provide significant fire safety challenges due to their large vertical openings,which facilitate rapid smoke spread and reduce sprinkler effectiveness.Traditional smoke management systems primarily rely on make-up air to replace the air expelled through vents.Inadequate calibration,particularly with air velocity,can worsen fire conditions by enhancing oxygen supply,increasing soot production,and reducing visibility,so endangering safe evacuation.This study investigates the impact of make-up air velocity on smoke behaviour in atrium environments through 24 simulations performed using the FireDynamics Simulator(FDS).Scenarios include various fire intensities(1,3,5 MW)and make-up air velocities(1–3.5 m/s),with fire sources located at the centre,northeast,and southwest corners.The simulation model was validated using updated full-scale fire test data with polystyrene fuel,leading to heightened soot density and reduced smoke clear height.This Research design diverges from other studies that predominantly utilized propane pool fires and concentrated on axisymmetric(Fire at the center of the atrum),Northeast and Southeast corners of the atrium scenarios by using polystyrene-a widely accessible construction material and examining several asymetric fire sites,so providing a more authentic depiction of atrium fire settings.Research reveals that increased air velocities,especially when directed at the fire,result in greater soot density and reduced smoke clearance due to intensified combustion.The northeastern region consistently displayed high temperature readings,highlighting the importance of fire source positioning in smoke behaviour.The study recommends limiting make-up air velocity to 1 m/s to avert turbulence and guarantee safety.This research provides critical insights for fire safety design and aligns with the United Nations Sustainable Development Goals,namely SDG 9 and SDG 11,by promoting safer and more resilient construction practices in urban environments.
基金funded by the National Natural Science Foundation of China(U22A20547)the Major Science and Technology Projects of Heilongjiang Province(2021ZX12B05 and 2020ZX07B02)。
文摘The present study monitored bacterial succession,physicochemical properties,and volatile organic compounds(VOCs)changes in smoked chicken legs with modified atmosphere packaging(MAP,60% CO_(2) and 40%N_(2))during a 25-day storage period at 4℃.After 15 days of storage,S erratia proteamaculans and Pseudomonas fragi became the predominant bacteria.Furthermore,physicochemical properties changed significantly,as evidenced by an increase in thiobarbituric acid reactive substances and b*(yellowness)value,and a decrease in hardness.A total of 65 VOCs were identified during storage.Correlation between bacterial succession and quality indicators(including VOCs and physicochemical properties)allowed the identification of 26 core dominant bacteria,including S.proteamaculans,Psychrobacter alimentarius,Pseudomonas putida,and Pseudomonas poae,which were positively related to spoilage VOCs(e.g.,1-octen-3-ol,1-pentanol,and 3-methyl-1-butanol)and could be defined as specific spoilage organisms(SSOs).The results of this study provide a systematic approach to predict SSOs in smoked chicken legs during storage,which can also provide a basis for product safety.
基金supported by the Peking University Medicine Fund of Fostering Young Scholars'Scientific&Technological Innovation[grant number BMU2024YFJHPY014]the Fundamental Research Funds for the Central Universities+1 种基金the Key Clinical Projects of Peking University Third Hospital[grant number BYSYZD2022014]the Capital’s Funds for Health Improvement and Research[grant number 2022-2G-40910]。
文摘Objective Cigarette smoking exacerbates the progression of pulmonary tuberculosis(TB).The role of tertiary lymphoid structures(TLS)in chronic lung diseases has gained attention;however,it remains unclear whether smoking-exacerbated lung damage in TB is associated with TLS.This study aimed to analyze the characteristics of pulmonary TLS in smokers with TB and to explore the possible role of TLS in smoking-related lung injury in TB.Methods Lung tissues from 36 male patients(18 smokers and 18 non-smokers)who underwent surgical resection for pulmonary TB were included in this study.Pathological and immunohistological analyses were conducted to evaluate the quantity of TLS,and chest computed tomography(CT)was used to assess the severity of lung lesions.The correlation between the TLS quantity and TB lesion severity scores was analyzed.The immune cells and chemokines involved in TLS formation were also evaluated and compared between smokers and non-smokers.Results Smoker patients with TB had significantly higher TLS than non-smokers(P<0.001).The TLS quantity in both the lung parenchyma and peribronchial regions correlated with TB lesion severity on chest CT(parenchyma:r=0.5767;peribronchial:r=0.7373;both P<0.001).Immunohistochemical analysis showed increased B cells,T cells,and C-X-C motif chemokine ligand 13(CXCL13)expression in smoker patients with TB(P<0.001).Conclusion Smoker TB patients exhibited increased pulmonary TLS,which was associated with exacerbated lung lesions on chest CT,suggesting that cigarette smoking may exacerbate lung damage by promoting TLS formation.
基金supported by a grant from R&D Program Development of Rail-Specific Digital Resource Technology Based on an AI-Enabled Rail Support Platform,grant number PK2401C1,of the Korea Railroad Research Institute.
文摘Fire detection has held stringent importance in computer vision for over half a century.The development of early fire detection strategies is pivotal to the realization of safe and smart cities,inhabitable in the future.However,the development of optimal fire and smoke detection models is hindered by limitations like publicly available datasets,lack of diversity,and class imbalance.In this work,we explore the possible ways forward to overcome these challenges posed by available datasets.We study the impact of a class-balanced dataset to improve the fire detection capability of state-of-the-art(SOTA)vision-based models and propose the use of generative models for data augmentation,as a future work direction.First,a comparative analysis of two prominent object detection architectures,You Only Look Once version 7(YOLOv7)and YOLOv8 has been carried out using a balanced dataset,where both models have been evaluated across various evaluation metrics including precision,recall,and mean Average Precision(mAP).The results are compared to other recent fire detection models,highlighting the superior performance and efficiency of the proposed YOLOv8 architecture as trained on our balanced dataset.Next,a fractal dimension analysis gives a deeper insight into the repetition of patterns in fire,and the effectiveness of the results has been demonstrated by a windowing-based inference approach.The proposed Slicing-Aided Hyper Inference(SAHI)improves the fire and smoke detection capability of YOLOv8 for real-life applications with a significantly improved mAP performance over a strict confidence threshold.YOLOv8 with SAHI inference gives a mAP:50-95 improvement of more than 25%compared to the base YOLOv8 model.The study also provides insights into future work direction by exploring the potential of generative models like deep convolutional generative adversarial network(DCGAN)and diffusion models like stable diffusion,for data augmentation.
基金The National Natural Science Foundation of China(No.51178217)the Natural Science Foundation of Jiangsu Province(No.BK2011804)
文摘The smoke spreading law of urban transportation tunnels with multiple shafts under natural ventilation is studied.A full-scale burning experiment is conducted in an actual tunnel.The study shows that smoke temperatures below the tunnel ceiling reduce rapidly along the longitudinal towards the tunnel exits. A noticeable temperature stratification is observed near the fire source.Most fire smoke is exhausted out of the shafts while the number of the smoke shafts in the downstream is more than that in the upstream.Large eddy simulation LES based on computational fluid dynamics CFD is carried out using the fire dynamics simulator FDS software with parallel processing in which the grid size of the fire-domain is set to be 0.083 m.The simulation results of temperatures under the ceiling the smoke fronts and the shafts＇smoke exhaust or air supply agree reasonably with the experimental data. Further simulations indicate that the decreasing ambient temperature or shaft spacing might reduce smoke temperatures under the tunnel ceiling and increase mass flow rates out of the shafts.This study provides technical scientific evidence and supports for the design and construction of such kinds of tunnels.
文摘Annual haze in Northern Thailand has become increasingly severe,impacting health and the environment.How-ever,the sources of the haze remain poorly quantified due to limited observational data on aerosol molecular tracers.This study comprehensively investigates chemical composition of PM_(2.5),including both inorganic and organic compounds throughout haze and post-haze periods in 2019 at a rural site of Northern Thailand.Average PM_(2.5) concentrations during haze and post-haze period were 87±36 and 21±11μg/m^(3),respectively.Organic matter was the dominant contributor in PM_(2.5) mass,followed by water soluble inorganic ions and mineral dust.Molecular markers,including levoglucosan,dehydroabietic acid,and 4-nitrocatechol,and ions(Cl^(-),and K^(+)),were used to characterize low haze(PM_(2.5)<100μg/m^(3))and episodic haze(PM_(2.5)>100μg/m^(3)).Low haze is associated with local aerosols from agricultural waste burning,while episodic haze is linked to aged aerosols from mixed agricultural waste,softwood,and hardwood burning.Source apportionment incorporating these molecular markers in receptor modelling(Positive matrix factorization),identified three distinct biomass burning sources:mixed,local,and aged biomass burnings,contributing 31,19 and 13%of PM_(2.5) during haze period.During post-haze period,contributions shifted,with local biomass burning(32%)comparable to secondary sulfate(34%)and mixed dust and traffic sources(26%).These findings demonstrate that both regional and local sources con-tribute to severe haze,highlighting the need for integrated policies for cross-border cooperation as well as stricter regulations to reduce biomass burning in Northern Thailand and Southeast Asia.
