Based on the testing restult of character of forest fire, with the aid mold of flameextinguishing and mathematical method, the combustion of the forest fuels and the energy transtfer under the convention condition wer...Based on the testing restult of character of forest fire, with the aid mold of flameextinguishing and mathematical method, the combustion of the forest fuels and the energy transtfer under the convention condition were studied and the mechanism and interrelated elements of flameextinguishing with high velocity airflow were given. The energy formulae is given:Nz =Ka0 L0 (15)GH/102η through combustion calculation and test revision This formula was checked through simulated testing for extinguishing low, medial and high intensity fires with high velocity airflow.展开更多
Mechanical characterization of steel frame structure after fire are ana- lyzed based on fire dynamics, heat transfer theory, structural mechanics, and finite element theory. We study the temperature characteristics an...Mechanical characterization of steel frame structure after fire are ana- lyzed based on fire dynamics, heat transfer theory, structural mechanics, and finite element theory. We study the temperature characteristics and mechanical prop- erties of steel flame structure under different fire locations and propose a safety evaluation method. We also analyze damage level of main flame components, maximum temperature of fire, thermal characteristics of flame components, fir- ing duration, etc. to provide useful information for fire resistance design of the steel frame structure and post-disaster safety evaluation.展开更多
This study deals with the physico-chemical, mineralogical and geotechnical characterization of alluvial clays from Batchenga in Cameroon with a view to their use as building materials for housing. The alluvial clay (A...This study deals with the physico-chemical, mineralogical and geotechnical characterization of alluvial clays from Batchenga in Cameroon with a view to their use as building materials for housing. The alluvial clay (Arg.All) was collected in the locality of Batchenga at the village Natchigal (4˚20'40''N and 11˚37'40''E at 378 m altitude) and was fired between 900˚C and 1100˚C. Characterization was performed by XRD, XRF, DTA/DTG, and firing tests. XRD, XRF, DTA/DTG infrared analysis methods were performed on these clays. The linear shrinkage, mechanical strengths, water absorption, porosity and density were measured on the fired products. The results obtained show that the major oxides are for the Arg.Lat SiO<sub>2</sub> (72.13%), Al<sub>2</sub>O<sub>3 </sub>(14.1%), Fe<sub>2</sub>O<sub>3</sub> (4.45%) and for the Arg.All: SiO<sub>2</sub> (48.91%), Al<sub>2</sub>O<sub>3</sub> (23.79%), Fe<sub>2</sub>O<sub>3</sub> (9.54%). The fired products based on alluvial clay, present the flexural strength of 4.45 MPa at 900˚C and 6.80 MPa at 1100˚C. As for those based on lateritic clay, the flexural strength is 0.53 and 0.76 MPa respectively at 900 and 1100˚C. The porosity is 33.69% at 900˚C and 22.93% at 1100˚C for the alluvial clay and 39.55% at 900˚C and 36.01% for the lateritic clay at 1100˚C. Water absorption is 18% to 11.16% for alluvial clay and 22.43% to 21.16% for lateritic clay at 900˚C and 1100˚C respectively. These results suggest that alluvial clay and its firing products have better physico-chemical, geotechnical and mechanical characteristics regardless of the firing temperature of the manufactured products. The addition of degreaser is recommended to improve the mechanical performance of lateritic clay.展开更多
This present research work is on the characterization of bauxite red mud (waste material) from Ngaoundal for the manufacture of ceramic products. After the extraction process, the raw material was characterized using ...This present research work is on the characterization of bauxite red mud (waste material) from Ngaoundal for the manufacture of ceramic products. After the extraction process, the raw material was characterized using Scanning Electron Microscopy (SEM). Morphology, mineral phases and chemical composition were determined by using energy-dispersive X-ray (EDX) analysis, X-ray diffractometer (XRD), X-ray fluorescence (XRF). Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA), Infra-Red (IR), Particle size (PS) were also used. Results of red mud analysis show that major oxides were Fe<sub>2</sub>O<sub>3</sub> (37.21%), Al<sub>2</sub>O<sub>3</sub> (19.6%), SiO<sub>2</sub> (7.68%), TiO<sub>2</sub> (1.07%), Na<sub>2</sub>O (4.71%), and CaO (2.75%). These last oxides require low temperature to melt and act as binders which link particles of red mud during the sintering process. Presence of alkaline oxides is an appeal to reduce energy consumption during ceramic manufacture process and to protect our environment for sustainable development. Physical and mechanical properties of fired red mud showed that the firing shrinkage, bulk density, and flexural strength increase with firing temperature. Porosity and water absorption had the same pattern and they decreased with the increase of temperature. Chemical stability reveals that 10% material loss is obtained after 7 days of treatment under acid-base conditions.展开更多
Lots of factors have influence on the firing accuracy of automatic weapon. During firing,the movement state of gun-shoulder system can be varied due to the impulsion of powder gases and the impact of moving parts,resu...Lots of factors have influence on the firing accuracy of automatic weapon. During firing,the movement state of gun-shoulder system can be varied due to the impulsion of powder gases and the impact of moving parts,resulting in a gunpoint being deviated from initial value to decrease the firing accuracy of weapon. The development of intelligent controlling gun carriage for weapon system is necessary for reflect its automatic firing accuracy objectively. An electronic measuring system for measuring the receiving force and movement of gun-shoulder system under initiative state is built based on the characteristics of standing non-rest automatic weapon. The constitutes of measuring system and the correction method of shoulder receiving force are described,and the mechanical admittance function of gun-shoulder system is obtained using electronically measured data,the modal identification of admittance functions of gun-shoulder system is made by adopting the orthogonal component method,and the key difference between the passive state and initiative state of standing non-rest automatic weapon is discussed.展开更多
The Pine Barrens in New York State are dominated by pitch pine(Pinus ridgida) and scrub oaks(Quercus ilicifolia and Q. prinoides). With fire suppression over the last 90 years or so, P. rigida regeneration has become ...The Pine Barrens in New York State are dominated by pitch pine(Pinus ridgida) and scrub oaks(Quercus ilicifolia and Q. prinoides). With fire suppression over the last 90 years or so, P. rigida regeneration has become sparse, even in areas set aside to preserve this type of vegetation. We evaluated the effects of fire and an alternative disturbance(mechanical removal of vegetation)for increasing P. rigida regeneration in the Albany Pine Bush Preserve in eastern New York State. By comparing cover, diameter and height of P. rigida, Q. ilicifolia, Q.prinoides, and Vaccinium spp.(blueberry) growing on the sites with a known fire history, we documented structural and compositional changes in the vegetation since its establishment. We also compared sites on which Quercus sprouts were controlled through mechanical removal. In the years following a disturbance, height and cover of Q. ilicifolia increased continuously and the species became increasingly competitive. Both the density of P. rigida seedlings and Vaccinium cover decreased significantly as the diameter and height of Quercus increased. Our results confirmed that the dominance by P. rigida could be attributed to periodic fires at intervals of 20–25 years. We conclude that removing Q. ilicifolia can favor P. rigida dominance on the barren without fire by releasing pine seedlings from competition.展开更多
To improve the performance of the forest fire smoke detection model and achieve a better balance between detection accuracy and speed, an improved YOLOv4 detection model (MoAm-YOLOv4) that combines a lightweight netwo...To improve the performance of the forest fire smoke detection model and achieve a better balance between detection accuracy and speed, an improved YOLOv4 detection model (MoAm-YOLOv4) that combines a lightweight network and attention mechanism was proposed. Based on the YOLOv4 algorithm, the backbone network CSPDarknet53 was replaced with a lightweight network MobilenetV1 to reduce the model’s size. An attention mechanism was added to the three channels before the output to increase its ability to extract forest fire smoke effectively. The algorithm used the K-means clustering algorithm to cluster the smoke dataset, and obtained candidate frames that were close to the smoke images;the dataset was expanded to 2000 images by the random flip expansion method to avoid overfitting in training. The experimental results show that the improved YOLOv4 algorithm has excellent detection effect. Its mAP can reach 93.45%, precision can get 93.28%, and the model size is only 45.58 MB. Compared with YOLOv4 algorithm, MoAm-YOLOv4 improves the accuracy by 1.3% and reduces the model size by 80% while sacrificing only 0.27% mAP, showing reasonable practicability.展开更多
文摘Based on the testing restult of character of forest fire, with the aid mold of flameextinguishing and mathematical method, the combustion of the forest fuels and the energy transtfer under the convention condition were studied and the mechanism and interrelated elements of flameextinguishing with high velocity airflow were given. The energy formulae is given:Nz =Ka0 L0 (15)GH/102η through combustion calculation and test revision This formula was checked through simulated testing for extinguishing low, medial and high intensity fires with high velocity airflow.
基金supported by the National Basic Research Program of China(2012CB719703)University of Anhui Provincial Natural Science Fund Project(J2013A068)
文摘Mechanical characterization of steel frame structure after fire are ana- lyzed based on fire dynamics, heat transfer theory, structural mechanics, and finite element theory. We study the temperature characteristics and mechanical prop- erties of steel flame structure under different fire locations and propose a safety evaluation method. We also analyze damage level of main flame components, maximum temperature of fire, thermal characteristics of flame components, fir- ing duration, etc. to provide useful information for fire resistance design of the steel frame structure and post-disaster safety evaluation.
文摘This study deals with the physico-chemical, mineralogical and geotechnical characterization of alluvial clays from Batchenga in Cameroon with a view to their use as building materials for housing. The alluvial clay (Arg.All) was collected in the locality of Batchenga at the village Natchigal (4˚20'40''N and 11˚37'40''E at 378 m altitude) and was fired between 900˚C and 1100˚C. Characterization was performed by XRD, XRF, DTA/DTG, and firing tests. XRD, XRF, DTA/DTG infrared analysis methods were performed on these clays. The linear shrinkage, mechanical strengths, water absorption, porosity and density were measured on the fired products. The results obtained show that the major oxides are for the Arg.Lat SiO<sub>2</sub> (72.13%), Al<sub>2</sub>O<sub>3 </sub>(14.1%), Fe<sub>2</sub>O<sub>3</sub> (4.45%) and for the Arg.All: SiO<sub>2</sub> (48.91%), Al<sub>2</sub>O<sub>3</sub> (23.79%), Fe<sub>2</sub>O<sub>3</sub> (9.54%). The fired products based on alluvial clay, present the flexural strength of 4.45 MPa at 900˚C and 6.80 MPa at 1100˚C. As for those based on lateritic clay, the flexural strength is 0.53 and 0.76 MPa respectively at 900 and 1100˚C. The porosity is 33.69% at 900˚C and 22.93% at 1100˚C for the alluvial clay and 39.55% at 900˚C and 36.01% for the lateritic clay at 1100˚C. Water absorption is 18% to 11.16% for alluvial clay and 22.43% to 21.16% for lateritic clay at 900˚C and 1100˚C respectively. These results suggest that alluvial clay and its firing products have better physico-chemical, geotechnical and mechanical characteristics regardless of the firing temperature of the manufactured products. The addition of degreaser is recommended to improve the mechanical performance of lateritic clay.
文摘This present research work is on the characterization of bauxite red mud (waste material) from Ngaoundal for the manufacture of ceramic products. After the extraction process, the raw material was characterized using Scanning Electron Microscopy (SEM). Morphology, mineral phases and chemical composition were determined by using energy-dispersive X-ray (EDX) analysis, X-ray diffractometer (XRD), X-ray fluorescence (XRF). Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA), Infra-Red (IR), Particle size (PS) were also used. Results of red mud analysis show that major oxides were Fe<sub>2</sub>O<sub>3</sub> (37.21%), Al<sub>2</sub>O<sub>3</sub> (19.6%), SiO<sub>2</sub> (7.68%), TiO<sub>2</sub> (1.07%), Na<sub>2</sub>O (4.71%), and CaO (2.75%). These last oxides require low temperature to melt and act as binders which link particles of red mud during the sintering process. Presence of alkaline oxides is an appeal to reduce energy consumption during ceramic manufacture process and to protect our environment for sustainable development. Physical and mechanical properties of fired red mud showed that the firing shrinkage, bulk density, and flexural strength increase with firing temperature. Porosity and water absorption had the same pattern and they decreased with the increase of temperature. Chemical stability reveals that 10% material loss is obtained after 7 days of treatment under acid-base conditions.
文摘Lots of factors have influence on the firing accuracy of automatic weapon. During firing,the movement state of gun-shoulder system can be varied due to the impulsion of powder gases and the impact of moving parts,resulting in a gunpoint being deviated from initial value to decrease the firing accuracy of weapon. The development of intelligent controlling gun carriage for weapon system is necessary for reflect its automatic firing accuracy objectively. An electronic measuring system for measuring the receiving force and movement of gun-shoulder system under initiative state is built based on the characteristics of standing non-rest automatic weapon. The constitutes of measuring system and the correction method of shoulder receiving force are described,and the mechanical admittance function of gun-shoulder system is obtained using electronically measured data,the modal identification of admittance functions of gun-shoulder system is made by adopting the orthogonal component method,and the key difference between the passive state and initiative state of standing non-rest automatic weapon is discussed.
文摘The Pine Barrens in New York State are dominated by pitch pine(Pinus ridgida) and scrub oaks(Quercus ilicifolia and Q. prinoides). With fire suppression over the last 90 years or so, P. rigida regeneration has become sparse, even in areas set aside to preserve this type of vegetation. We evaluated the effects of fire and an alternative disturbance(mechanical removal of vegetation)for increasing P. rigida regeneration in the Albany Pine Bush Preserve in eastern New York State. By comparing cover, diameter and height of P. rigida, Q. ilicifolia, Q.prinoides, and Vaccinium spp.(blueberry) growing on the sites with a known fire history, we documented structural and compositional changes in the vegetation since its establishment. We also compared sites on which Quercus sprouts were controlled through mechanical removal. In the years following a disturbance, height and cover of Q. ilicifolia increased continuously and the species became increasingly competitive. Both the density of P. rigida seedlings and Vaccinium cover decreased significantly as the diameter and height of Quercus increased. Our results confirmed that the dominance by P. rigida could be attributed to periodic fires at intervals of 20–25 years. We conclude that removing Q. ilicifolia can favor P. rigida dominance on the barren without fire by releasing pine seedlings from competition.
文摘To improve the performance of the forest fire smoke detection model and achieve a better balance between detection accuracy and speed, an improved YOLOv4 detection model (MoAm-YOLOv4) that combines a lightweight network and attention mechanism was proposed. Based on the YOLOv4 algorithm, the backbone network CSPDarknet53 was replaced with a lightweight network MobilenetV1 to reduce the model’s size. An attention mechanism was added to the three channels before the output to increase its ability to extract forest fire smoke effectively. The algorithm used the K-means clustering algorithm to cluster the smoke dataset, and obtained candidate frames that were close to the smoke images;the dataset was expanded to 2000 images by the random flip expansion method to avoid overfitting in training. The experimental results show that the improved YOLOv4 algorithm has excellent detection effect. Its mAP can reach 93.45%, precision can get 93.28%, and the model size is only 45.58 MB. Compared with YOLOv4 algorithm, MoAm-YOLOv4 improves the accuracy by 1.3% and reduces the model size by 80% while sacrificing only 0.27% mAP, showing reasonable practicability.
