The impact sensitivity assessment of spacecraft is to obtain the probability of spacecraft encountering the OD/M(orbital debris or meteoroid),which is a prerequisite for survivability assessment of on-orbit spacecraft...The impact sensitivity assessment of spacecraft is to obtain the probability of spacecraft encountering the OD/M(orbital debris or meteoroid),which is a prerequisite for survivability assessment of on-orbit spacecraft.An impact sensitivity assessment method of spacecraft based on virtual exterior wall was proposed to improve the computational efficiency.This method eliminates determination of the outermost surface elements of the spacecraft before generating the debris rays,which are assumed to originate from a non-concave virtual wall that completely wraps the spacecraft.The Dist Mesh method was adopted for the generating of the virtual wall to ensure its mesh quality.The influences of the sizes,mesh densities,shapes of the virtual wall on the efficiency and accuracy were considered to obtain the best combination of the size and mesh density of the wall and spacecraft.The results of this method were compared with those of S3DE(Survivability of Spacecraft in Space Debris Environment),BUMPER,MDPANTO,ESABASE2/Debris to verify the feasibility of the method.The PCHIP(Piecewise Cubic Hermite Interpolating Polynomial)was used to fit the size vs.flux relationship of the space debris to acquire the impact probability of OD/M with arbitrary size on the spacecraft.展开更多
This research will develop a set of assessment techniques and proce-dures for exterior wall deterioration detection.The proposed method is mainly based on equipped with high-resolution photographic equipment for unman...This research will develop a set of assessment techniques and proce-dures for exterior wall deterioration detection.The proposed method is mainly based on equipped with high-resolution photographic equipment for unmanned aerial vehicle(UAV).To overcome the problems of visual inspection difficulties due to diferent angles and height,the proposed method provides a safer and more efficient detection way to get the buildings'exterior status.After using the pro-posed method to analyze the images taken from UAV,the size of the damaged area can be evaluated more accurately,and the accuracy rate of visual assessment will be significantly improved.The results of the proposed method can reduce the accidents caused by the inspection process in the critical environment and the costs incured by the temporary facilities without sacrificing the quality of the inspection results.Then,the research will implement the existing visual assessment method because of the characteristics of rapid detection,however,the assessment results will be different from different inspectors due to subjectivity.Thus,the research will present an improved visual inspection method by using UAV and Forward Looking Infred Thermal technology (FLIR).The result will be presented by Condition Index(CI-Level)instead to improve the subjectivity of the personnel.展开更多
This paper mainly uses the method of numerical simulation, and study thermal insulation and energy saving characteristics on the exterior walls of the building and analyze the optimal layout scheme of building exterio...This paper mainly uses the method of numerical simulation, and study thermal insulation and energy saving characteristics on the exterior walls of the building and analyze the optimal layout scheme of building exterior wall and thermal insulation system. Finally, the paper study optimal thickness of insulation materials. The paper elaborate scheme of the existing building energy-saving for exterior wall and the scope of application, the system structure and the construction technology. The results showed that： extruded benzene board that can be used for exterior insulation, frame structure filled with wall preferred ceramsite hollow block. The paper can provides reference selection of insulation for building external wall energy-saving transformation scheme.展开更多
Existing fire test methods reply on measurement of the energy released rate to identify the combustion properties of a material. However, they are inadequate when assessing combustion characteristics of a composite ma...Existing fire test methods reply on measurement of the energy released rate to identify the combustion properties of a material. However, they are inadequate when assessing combustion characteristics of a composite material characterized by vertical flame spread and different inside/outside combustion behaviors. In addition, major factors that affect the flame spread outside the building include the combustion characteristics of materials used as well as air flow around a skyscraper. However, since it is highly difficult to analyze and forecast the air flow from a fire engineering viewpoint, an investigation of the flame spread characteristics of exterior walls of a building depends primarily on the combustion characteristics of materials. Hence, this study examined, using ISO 13785-2 testing method, the temperature changes and vertical flame spread behaviors of one of the finishing materials for exterior walls--（generic ＆ fire-resistant） aluminium panels by a real-scale combustion experiment. According to the results of real-scale experiment, the maximum heat temperature of 987.7 ℃ was recorded seven minutes after the fire test was initiated while the fire-resistant aluminium panels showed the maximum heat temperature of 850.2℃ after exposed for approximately 12 min. The vertical flame spread properties put more emphasis on the time required to reach the maximum temperature rather than its magnitude and there was a five minutes difference between the materials.展开更多
The present paper proposes a detection method for building exterior wall cracks since manual detection methods have high risk and low efficiency.The proposed method is based on Unmanned Aerial Vehicle(UAV)and computer...The present paper proposes a detection method for building exterior wall cracks since manual detection methods have high risk and low efficiency.The proposed method is based on Unmanned Aerial Vehicle(UAV)and computer vision technology.First,a crack dataset of 1920 images was established using UAV to collect the images of a residential building exterior wall under different lighting conditions.Second,the average crack detection precisions of different methods including the Single Shot MultiBox Detector,You Only Look Once v3,You Only Look Once v4,Faster Regional Convolutional Neural Network(R-CNN)and Mask R-CNN methods were compared.Then,the Mask R-CNN method with the best performance and average precision of 0.34 was selected.Finally,based on the characteristics of cracks,the utilization ratio of Mask R-CNN to the underlying features was improved so that the average precision of 0.9 was achieved.It was found that the positioning accuracy and mask coverage rate of the proposed Mask R-CNN method are greatly improved.Also,it will be shown that using UAV is safer than manual detection because manual parameter setting is not required.In addition,the proposed detection method is expected to greatly reduce the cost and risk of manual detection of building exterior wall cracks and realize the efficient identification and accurate labeling of building exterior wall cracks.展开更多
Reflective and insulative composite coatings are a new energy-saving material with high solar reflectance and extremely low thermal conductivity for buildings.The optimization and impact of high solar reflectance and ...Reflective and insulative composite coatings are a new energy-saving material with high solar reflectance and extremely low thermal conductivity for buildings.The optimization and impact of high solar reflectance and low thermal conductivity on the insulating capacity of walls remain uncertain.This work investigates the dynamic thermal performance and energy efficiency of a reflective and insulative composite coating in regions with hot summer and warm winter.A simplified thermal resistance-heat capacitance model of an exterior building wall is established to predict thermal performance.The dynamic temperature and heat flow of the wall are predicted to reduce heat loss through the interior surface of the wall and compared to the conventional coating.The specific impact of the thermal conductivity and solar reflectance of the coating on the heat loss is further investigated to minimize heat loss of the wall.This research shows that the composite coating shows better performance on adjusting outdoor climate change than the other coating.Compared with cement,it reduces the maximum temperature of the exterior surface of the wall by 7.45°C,and the heat loss through the interior surface of the wall by 38%.The heat loss is reduced with the increase of solar reflectance and the reduction of thermal conductivity.The results can provide a useful reference and guidance for the application of reflective and insulative composite coating on building exterior wall to promote their energy-saving use on building envelopes.展开更多
文摘The impact sensitivity assessment of spacecraft is to obtain the probability of spacecraft encountering the OD/M(orbital debris or meteoroid),which is a prerequisite for survivability assessment of on-orbit spacecraft.An impact sensitivity assessment method of spacecraft based on virtual exterior wall was proposed to improve the computational efficiency.This method eliminates determination of the outermost surface elements of the spacecraft before generating the debris rays,which are assumed to originate from a non-concave virtual wall that completely wraps the spacecraft.The Dist Mesh method was adopted for the generating of the virtual wall to ensure its mesh quality.The influences of the sizes,mesh densities,shapes of the virtual wall on the efficiency and accuracy were considered to obtain the best combination of the size and mesh density of the wall and spacecraft.The results of this method were compared with those of S3DE(Survivability of Spacecraft in Space Debris Environment),BUMPER,MDPANTO,ESABASE2/Debris to verify the feasibility of the method.The PCHIP(Piecewise Cubic Hermite Interpolating Polynomial)was used to fit the size vs.flux relationship of the space debris to acquire the impact probability of OD/M with arbitrary size on the spacecraft.
文摘This research will develop a set of assessment techniques and proce-dures for exterior wall deterioration detection.The proposed method is mainly based on equipped with high-resolution photographic equipment for unmanned aerial vehicle(UAV).To overcome the problems of visual inspection difficulties due to diferent angles and height,the proposed method provides a safer and more efficient detection way to get the buildings'exterior status.After using the pro-posed method to analyze the images taken from UAV,the size of the damaged area can be evaluated more accurately,and the accuracy rate of visual assessment will be significantly improved.The results of the proposed method can reduce the accidents caused by the inspection process in the critical environment and the costs incured by the temporary facilities without sacrificing the quality of the inspection results.Then,the research will implement the existing visual assessment method because of the characteristics of rapid detection,however,the assessment results will be different from different inspectors due to subjectivity.Thus,the research will present an improved visual inspection method by using UAV and Forward Looking Infred Thermal technology (FLIR).The result will be presented by Condition Index(CI-Level)instead to improve the subjectivity of the personnel.
文摘This paper mainly uses the method of numerical simulation, and study thermal insulation and energy saving characteristics on the exterior walls of the building and analyze the optimal layout scheme of building exterior wall and thermal insulation system. Finally, the paper study optimal thickness of insulation materials. The paper elaborate scheme of the existing building energy-saving for exterior wall and the scope of application, the system structure and the construction technology. The results showed that： extruded benzene board that can be used for exterior insulation, frame structure filled with wall preferred ceramsite hollow block. The paper can provides reference selection of insulation for building external wall energy-saving transformation scheme.
文摘Existing fire test methods reply on measurement of the energy released rate to identify the combustion properties of a material. However, they are inadequate when assessing combustion characteristics of a composite material characterized by vertical flame spread and different inside/outside combustion behaviors. In addition, major factors that affect the flame spread outside the building include the combustion characteristics of materials used as well as air flow around a skyscraper. However, since it is highly difficult to analyze and forecast the air flow from a fire engineering viewpoint, an investigation of the flame spread characteristics of exterior walls of a building depends primarily on the combustion characteristics of materials. Hence, this study examined, using ISO 13785-2 testing method, the temperature changes and vertical flame spread behaviors of one of the finishing materials for exterior walls--（generic ＆ fire-resistant） aluminium panels by a real-scale combustion experiment. According to the results of real-scale experiment, the maximum heat temperature of 987.7 ℃ was recorded seven minutes after the fire test was initiated while the fire-resistant aluminium panels showed the maximum heat temperature of 850.2℃ after exposed for approximately 12 min. The vertical flame spread properties put more emphasis on the time required to reach the maximum temperature rather than its magnitude and there was a five minutes difference between the materials.
基金This work was supported in part by the National Natural Science Foundation of China under Grant 51408063,author W.C,http://www.nsfc.gov.cn/in part by the Outstanding Youth Scholars of the Department of Hunan Provincial under Grant 20B031,author W.C,http://kxjsc.gov.hnedu.cn/.
文摘The present paper proposes a detection method for building exterior wall cracks since manual detection methods have high risk and low efficiency.The proposed method is based on Unmanned Aerial Vehicle(UAV)and computer vision technology.First,a crack dataset of 1920 images was established using UAV to collect the images of a residential building exterior wall under different lighting conditions.Second,the average crack detection precisions of different methods including the Single Shot MultiBox Detector,You Only Look Once v3,You Only Look Once v4,Faster Regional Convolutional Neural Network(R-CNN)and Mask R-CNN methods were compared.Then,the Mask R-CNN method with the best performance and average precision of 0.34 was selected.Finally,based on the characteristics of cracks,the utilization ratio of Mask R-CNN to the underlying features was improved so that the average precision of 0.9 was achieved.It was found that the positioning accuracy and mask coverage rate of the proposed Mask R-CNN method are greatly improved.Also,it will be shown that using UAV is safer than manual detection because manual parameter setting is not required.In addition,the proposed detection method is expected to greatly reduce the cost and risk of manual detection of building exterior wall cracks and realize the efficient identification and accurate labeling of building exterior wall cracks.
基金the National Natural Science Foundation of China(No.52078144)the National Natural Science Foundation of China(No.52108073)the Innovation Research for Postgraduates of Guangzhou University(No.2021GDJC-D15).
文摘Reflective and insulative composite coatings are a new energy-saving material with high solar reflectance and extremely low thermal conductivity for buildings.The optimization and impact of high solar reflectance and low thermal conductivity on the insulating capacity of walls remain uncertain.This work investigates the dynamic thermal performance and energy efficiency of a reflective and insulative composite coating in regions with hot summer and warm winter.A simplified thermal resistance-heat capacitance model of an exterior building wall is established to predict thermal performance.The dynamic temperature and heat flow of the wall are predicted to reduce heat loss through the interior surface of the wall and compared to the conventional coating.The specific impact of the thermal conductivity and solar reflectance of the coating on the heat loss is further investigated to minimize heat loss of the wall.This research shows that the composite coating shows better performance on adjusting outdoor climate change than the other coating.Compared with cement,it reduces the maximum temperature of the exterior surface of the wall by 7.45°C,and the heat loss through the interior surface of the wall by 38%.The heat loss is reduced with the increase of solar reflectance and the reduction of thermal conductivity.The results can provide a useful reference and guidance for the application of reflective and insulative composite coating on building exterior wall to promote their energy-saving use on building envelopes.
