To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex conf...To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex configuration features and abrupt cross-sectional transitions was fabricated by liquid-solid extrusion following vacuum pressure infiltration process(LSEVI).Near-net forming schemes of both the special-shaped fiber preform and composite part were proposed.The effect of process parameters on the forming quality of the composite part was discussed.Meanwhile,the microstructures and compressive properties in different regions of the part were analyzed.The results show that the forward forming scheme provides the special-shaped fiber preform with no surface defects.For the C_(sf)/AZ91D part,its internal microstructures show that the infiltration of liquid magnesium is sufficient and uniform.The compressive strength of the composite part can reach up to 487 MPa,corresponding to~40%increase compared to 335 MPa of the AZ91D alloy.The average compressive strain of composites is less than 10%,which is about 50%of that of the AZ91D alloy.When the fiber orientation is parallel to the shear direction on the shear plane,the load-bearing capacity of the fiber is much higher than that of the fiber perpendicular to the shear direction.This work not only provides a convenient approach to fabricate special-shaped preform with high fiber volume fraction,but also gives a demonstration for the near-net forming of C_(sf)/Mg parts with excellent material isotropy and compressive properties.展开更多
Specially shaped permanent magnet structures can satisfy the requirements of equipment with limited space or unique shapes.Thereby,these optimize the distribution of magnetic fields.However,traditional manufacturing m...Specially shaped permanent magnet structures can satisfy the requirements of equipment with limited space or unique shapes.Thereby,these optimize the distribution of magnetic fields.However,traditional manufacturing methods are limited by the mold design and insufficient material utilization.In this study,a polymer-based Nd_(2)Fe_(14)B(NdFeB)magnetic slurry was developed based on direct ink writing(DIW)3D printing technology.A rapidly volatilizable magnetic slurry was used to achieve 3D oriented controllable layering,thus realizing the direct molding fabrication of NdFeB permanent magnets with complex structures.By exploring and optimizing the 3D printing process parameters,specially shaped bonded NdFeB permanent magnet structures with high precision and shape fidelity were prepared.The test results indicated that the remnant magnetization of the printed magnets was proportional to the NdFeB content in the slurry,the coercivity closely matched that of the original powder,and the mechanical properties of the printed magnets were favorable.Building on this,a magnetically driven helical-structure robot was designed and printed to achieve stable motion in low-Reynolds-number fluids.This paper presents a new,low-cost solution for the room-temperature preparation of shape-bonded NdFeB permanent magnets.展开更多
Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of...Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of integrating ceiling fans with higher air conditioning setpoints on thermal comfort and energy efficiency in office environments.Field measurements and questionnaire surveys were conducted to evaluate thermal comfort and energysaving potential under varying conditions.Results show that increasing the AC setpoint from 25○C to 27○C,combined with ceiling fan operation,reduced power consumption by 10%,achieving significant energy savings.Survey data confirmed that 85%of participants reported consistent thermal sensations across all conditions,with ceiling fans effectively compensating for higher setpoints through enhanced air circulation.CFDsimulations revealed that mediumspeed ceiling fan operation produced the most uniformairflowdistribution,with an average air velocity of 0.45 m/s,and minimized temperature variations,ensuring balanced thermal conditions.Temperature analysis showed a reduction in hotspots and cold zones,maintaining an average temperature deviation of less than±0.5○C.Predicted Mean Vote(PMV)evaluations at a 27○C setpoint indicated improved thermal comfort,with average PMV values around−0.3,corresponding to a“neutral”thermal sensation.These findings demonstrate the effectiveness of integrating ceiling fans with HVAC systems in achieving energy efficiency and occupant comfort,offering a sustainable approach to reducing AC energy consumption in office environments.展开更多
Severe damage to suspended ceilings of metal grids and lay-in panels was observed in public buildings during the 2013 M7.0 Lushan earthquake in China. Over the past several years, suspended ceilings have been widely u...Severe damage to suspended ceilings of metal grids and lay-in panels was observed in public buildings during the 2013 M7.0 Lushan earthquake in China. Over the past several years, suspended ceilings have been widely used practice in public buildings throughout China, including government offices, schools and hospitals. To investigate the damage mechanism of suspended ceilings, a series of three-dimensional shake table tests was conducted to reproduce the observed damage. A full-scale reinforced concrete frame was constructed as the testing frame for the ceiling, which was single-story and infilled with brick masonry walls to represent the local construction of low-rise buildings. In general, the ceiling in the tests exhibited similar damage phenomena as the field observations, such as higher vulnerability of perimeter elements and extensive damage to the cross runners. However, it exhibited lower fragility in terms of peak ground/roof accelerations at the initiation of damage. Further investigations are needed to clarify the reasons for this behavior.展开更多
A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, consider...A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.展开更多
In this paper,we present a novel algorithm for odometry estimation based on ceiling vision.The main contribution of this algorithm is the introduction of principal direction detection that can greatly reduce error acc...In this paper,we present a novel algorithm for odometry estimation based on ceiling vision.The main contribution of this algorithm is the introduction of principal direction detection that can greatly reduce error accumulation problem in most visual odometry estimation approaches.The principal direction is defned based on the fact that our ceiling is flled with artifcial vertical and horizontal lines which can be used as reference for the current robot s heading direction.The proposed approach can be operated in real-time and it performs well even with camera s disturbance.A moving low-cost RGB-D camera（Kinect）,mounted on a robot,is used to continuously acquire point clouds.Iterative closest point（ICP） is the common way to estimate the current camera position by registering the currently captured point cloud to the previous one.However,its performance sufers from data association problem or it requires pre-alignment information.The performance of the proposed principal direction detection approach does not rely on data association knowledge.Using this method,two point clouds are properly pre-aligned.Hence,we can use ICP to fne-tune the transformation parameters and minimize registration error.Experimental results demonstrate the performance and stability of the proposed system under disturbance in real-time.Several indoor tests are carried out to show that the proposed visual odometry estimation method can help to signifcantly improve the accuracy of simultaneous localization and mapping（SLAM）.展开更多
Numerous investigations have been conducted to understand the wall effects on rotors.The purpose of this study is to further investigate the aerodynamic performance of revolving wings,especially when it is very close ...Numerous investigations have been conducted to understand the wall effects on rotors.The purpose of this study is to further investigate the aerodynamic performance of revolving wings,especially when it is very close to the ground and ceiling(i.e.,less than half the wingspan)at low Reynolds numbers.Hence,the ground and ceiling effect for hovering micro revolving wings at low Reynolds numbers are investigated by improving the theoretical models.The theoretical model for the ground effect is established based on the wall-jet assumption,and that for the ceiling effect is improved by considering the uneven spanwise distribution of induced velocity.These two models are validated by comparing the results of experiments and CFD simulations with the Lattice-Boltzmann Method(LBM).Both ground and ceiling effects are found helpful to enhance the thrust,especially with small wing-wall distances,by making a difference to the induced velocity and the pressure distribution.By comparing the thrust generation and aerodynamic efficiency between the ground and ceiling effects,the former is found more helpful to the thrust augmentation,and the latter is more beneficial for the aerodynamic efficiency promotion.展开更多
This paper proposes modifications to the tradional Ceiling Bounce Model and uses it to characterize diffuse indoor optical wireless channel by analyzing the effect of transceiver position on signal propagation propert...This paper proposes modifications to the tradional Ceiling Bounce Model and uses it to characterize diffuse indoor optical wireless channel by analyzing the effect of transceiver position on signal propagation properties. The modified approach uses a combination of the tradional ceiling bounce method and a statistical approach. The effects of different transmitter-receiver separations and height of the ceiling on path loss and delay spread are studied in detail.展开更多
The architectural?complexes?of Hasan Basha Tahir?were suffering from many damages and deformation in different elements as load bearing walls, arches and wooden ceiling. Ground water, salt weathering, air pollution, b...The architectural?complexes?of Hasan Basha Tahir?were suffering from many damages and deformation in different elements as load bearing walls, arches and wooden ceiling. Ground water, salt weathering, air pollution, biological colonization and environmental aspects were the main degradation factors which caused a lot of damage and deterioration phenomena in the complexes. Horizontal and vertical cracks, salts, loss of decorations, and featured dark of the stone surface were noticed at the complexes elements. In addition, the celling of the complex was in a very bad condition;?it had lost a lot of decoration elements, cracking, soot deposition, insects’ holes, and fungi growth. This research will discuss the various deterioration phenomena that?have?effect on the main building materials and cause the damages and discuss the general scientific methodology of the architectural and structural conservation project which was?carried out.展开更多
One quarter scale experiment device of a typical L-shape architecture structure including a burning room and an adjacent hallway is established to carry out the research.The smoke characteristics at the sampling point...One quarter scale experiment device of a typical L-shape architecture structure including a burning room and an adjacent hallway is established to carry out the research.The smoke characteristics at the sampling points below the ceiling of the burning compartment and the roof of the hallway are studied systematically to find out the effects of different ceilings on the local fire origin compartment and the smoke transportation to a remote area.A series of tests is reported and the smoke residence time,the concentration peak and the concentration build up rate are investigated as functions of the type of the ceiling.The smoke residence time,the most important factor concerning smoke toxicity,is described by a novel concept,wavelength,in this study.Furthermore,it is worth emphasizing that the PVC ceiling exhibits a phenomenon of frequent collapse during the fire developing period.The single heat action is conducted to judge the smoke and the heat effect on the fire risk.展开更多
Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack...Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.展开更多
This paper presents an image-based mobile robot guidance system in an indoor space with installed artificial ceiling landmarks. The overall system, including an omni-directional mobile robot motion control, landmark i...This paper presents an image-based mobile robot guidance system in an indoor space with installed artificial ceiling landmarks. The overall system, including an omni-directional mobile robot motion control, landmark image processing and image recognition, is implemented on a single FPGA chip with one CMOS image sensor. The proposed feature representation of the artificial ceiling landmarks is invariant with respect to rotation and translation. One unique feature of the proposed ceiling landmark recognition system is that the feature points of landmarks are determined by topological information from both the foreground and background. To enhance recognition accuracy, landmark classification is performed after the mobile robot is moved to a position such that the ceiling landmark is located in the upright- top corner position of the robot’s camera image. The accuracy of the proposed artificial ceiling landmark recognition system using the nearest neighbor classification is 100% in our experiments.展开更多
Driven by the rapid economic development,the development of transportation in China has begun to move towards mountainous areas.The climate environment,topography and landform of mountainous cities are different from ...Driven by the rapid economic development,the development of transportation in China has begun to move towards mountainous areas.The climate environment,topography and landform of mountainous cities are different from those of plain areas.In mountainous cities,the area of opposite interchanges between expressways and urban roads is generally large,which has a certain contradiction with the topographic conditions of mountainous cities.Therefore,it is necessary to reasonably design the opposite interchanges between expressways and urban roads in mountainous cities.The author explores and analyzes the factors restricting the special-shaped interchange between expressway and urban road in mountainous cities and the main fbnns of special-shaped interchange,and puts forward a reasonable design scheme,hoping to make a smooth development of the special-shaped interchange in mountainous cities.展开更多
For special-shaped parts, the clamping and processing are very difficult. Based on this, a part with high precision and special shape is selected as a case. In-depth analysis of its structure and accuracy, scientific ...For special-shaped parts, the clamping and processing are very difficult. Based on this, a part with high precision and special shape is selected as a case. In-depth analysis of its structure and accuracy, scientific and reasonable formulation of the processing technology, at the same time, the complete involvement of special tooling and fixtures, so as to ensure the simplification of parts processing, and thus ensure the processing progress. At the same time, in order to effectively control the quality based on the accuracy and shape requirements of the parts themselves, if ordinary inspection equipment is applied, the purpose of inspection cannot be achieved. Therefore, according to the actual situation, special inspection tools should be designed to ensure the reliability and efficiency of the inspection. Based on this, this paper mainly analyzes and discusses the NC machining process analysis and testing of precision special-shaped parts.展开更多
Due to the vigorous development of the market, the demands of urban residents for interior decoration of buildings are increasing day by day. In the actual building decoration process, as the indoor suspended ceiling ...Due to the vigorous development of the market, the demands of urban residents for interior decoration of buildings are increasing day by day. In the actual building decoration process, as the indoor suspended ceiling and ceiling of the building are the key decoration parts, its construction quality will also directly affect the decoration quality in the building. Based on this, this chapter focuses on discussing and expounding the construction and handling skills of indoor suspended ceiling and ceiling decoration of buildings, with a view to promoting the development of China's architectural decoration industry.展开更多
This work focuses on the estimation of a duty cycle of a radiant ceiling heating system with a panel surface temperature of 35℃and a heat flux of 65 W/m2 that corresponds to a thermal comfort for sedentary occupants....This work focuses on the estimation of a duty cycle of a radiant ceiling heating system with a panel surface temperature of 35℃and a heat flux of 65 W/m2 that corresponds to a thermal comfort for sedentary occupants.The results obtained are based on the theoretical heat transfer equations that govern the radiant and natural convection heat exchange mechanisms,and experimental heat transfer coefficients available in the literature.The results of the examined radiant heating system with specific conditions showed that a duty cycle of 6.46 min alternated by 13.36 min in shutting-down position is required to assure an acceptable thermal comfort for the enclosure space occupants.In addition,the study showed that for extremely cold-temperature conditions the heating system requires a daily operating load of about 61.2%which clearly proves the efficiency of these radiant heating systems in terms of energy consumption.展开更多
基金support from the National Natural Science Foundation of China (No.52231004,52175365,51972271)Dr.Jiawei Fu appreciates the support from The Young Talents Plan in Shaanxi Province of China (No.00121)。
文摘To meet the increased demand for light-weight and high-performance special-shaped load bearing parts in automotive industry,the short carbon fiber reinforced magnesium matrix composite(C_(sf)/Mg)part with complex configuration features and abrupt cross-sectional transitions was fabricated by liquid-solid extrusion following vacuum pressure infiltration process(LSEVI).Near-net forming schemes of both the special-shaped fiber preform and composite part were proposed.The effect of process parameters on the forming quality of the composite part was discussed.Meanwhile,the microstructures and compressive properties in different regions of the part were analyzed.The results show that the forward forming scheme provides the special-shaped fiber preform with no surface defects.For the C_(sf)/AZ91D part,its internal microstructures show that the infiltration of liquid magnesium is sufficient and uniform.The compressive strength of the composite part can reach up to 487 MPa,corresponding to~40%increase compared to 335 MPa of the AZ91D alloy.The average compressive strain of composites is less than 10%,which is about 50%of that of the AZ91D alloy.When the fiber orientation is parallel to the shear direction on the shear plane,the load-bearing capacity of the fiber is much higher than that of the fiber perpendicular to the shear direction.This work not only provides a convenient approach to fabricate special-shaped preform with high fiber volume fraction,but also gives a demonstration for the near-net forming of C_(sf)/Mg parts with excellent material isotropy and compressive properties.
基金supported by National Natural Science Foundation of China(Grant Nos.52375348,52175331)National Natural Science Foundation of Shandong Province(Grant Nos.ZR2022ME014,ZR2020ZD04).
文摘Specially shaped permanent magnet structures can satisfy the requirements of equipment with limited space or unique shapes.Thereby,these optimize the distribution of magnetic fields.However,traditional manufacturing methods are limited by the mold design and insufficient material utilization.In this study,a polymer-based Nd_(2)Fe_(14)B(NdFeB)magnetic slurry was developed based on direct ink writing(DIW)3D printing technology.A rapidly volatilizable magnetic slurry was used to achieve 3D oriented controllable layering,thus realizing the direct molding fabrication of NdFeB permanent magnets with complex structures.By exploring and optimizing the 3D printing process parameters,specially shaped bonded NdFeB permanent magnet structures with high precision and shape fidelity were prepared.The test results indicated that the remnant magnetization of the printed magnets was proportional to the NdFeB content in the slurry,the coercivity closely matched that of the original powder,and the mechanical properties of the printed magnets were favorable.Building on this,a magnetically driven helical-structure robot was designed and printed to achieve stable motion in low-Reynolds-number fluids.This paper presents a new,low-cost solution for the room-temperature preparation of shape-bonded NdFeB permanent magnets.
基金support by the National Science and Technology Council under Grant No.NSTC 112-2221-E-167-017-MY3.
文摘Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of integrating ceiling fans with higher air conditioning setpoints on thermal comfort and energy efficiency in office environments.Field measurements and questionnaire surveys were conducted to evaluate thermal comfort and energysaving potential under varying conditions.Results show that increasing the AC setpoint from 25○C to 27○C,combined with ceiling fan operation,reduced power consumption by 10%,achieving significant energy savings.Survey data confirmed that 85%of participants reported consistent thermal sensations across all conditions,with ceiling fans effectively compensating for higher setpoints through enhanced air circulation.CFDsimulations revealed that mediumspeed ceiling fan operation produced the most uniformairflowdistribution,with an average air velocity of 0.45 m/s,and minimized temperature variations,ensuring balanced thermal conditions.Temperature analysis showed a reduction in hotspots and cold zones,maintaining an average temperature deviation of less than±0.5○C.Predicted Mean Vote(PMV)evaluations at a 27○C setpoint indicated improved thermal comfort,with average PMV values around−0.3,corresponding to a“neutral”thermal sensation.These findings demonstrate the effectiveness of integrating ceiling fans with HVAC systems in achieving energy efficiency and occupant comfort,offering a sustainable approach to reducing AC energy consumption in office environments.
基金Research fund for earthquake engineering of China Earthquake Administration(201508023)a project of the National Science&Technology Support Program during the Twelfth Five-year Plan Period of China(2015BAK17B03)a general program of National Natural Science Foundation of China(51578515)
文摘Severe damage to suspended ceilings of metal grids and lay-in panels was observed in public buildings during the 2013 M7.0 Lushan earthquake in China. Over the past several years, suspended ceilings have been widely used practice in public buildings throughout China, including government offices, schools and hospitals. To investigate the damage mechanism of suspended ceilings, a series of three-dimensional shake table tests was conducted to reproduce the observed damage. A full-scale reinforced concrete frame was constructed as the testing frame for the ceiling, which was single-story and infilled with brick masonry walls to represent the local construction of low-rise buildings. In general, the ceiling in the tests exhibited similar damage phenomena as the field observations, such as higher vulnerability of perimeter elements and extensive damage to the cross runners. However, it exhibited lower fragility in terms of peak ground/roof accelerations at the initiation of damage. Further investigations are needed to clarify the reasons for this behavior.
基金Projects(51278170,U1134207)supported by the National Natural Science Foundation of ChinaProject(B13024)supported by the Program of Introducing Talents of Discipline to Universities,China
文摘A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.
文摘In this paper,we present a novel algorithm for odometry estimation based on ceiling vision.The main contribution of this algorithm is the introduction of principal direction detection that can greatly reduce error accumulation problem in most visual odometry estimation approaches.The principal direction is defned based on the fact that our ceiling is flled with artifcial vertical and horizontal lines which can be used as reference for the current robot s heading direction.The proposed approach can be operated in real-time and it performs well even with camera s disturbance.A moving low-cost RGB-D camera（Kinect）,mounted on a robot,is used to continuously acquire point clouds.Iterative closest point（ICP） is the common way to estimate the current camera position by registering the currently captured point cloud to the previous one.However,its performance sufers from data association problem or it requires pre-alignment information.The performance of the proposed principal direction detection approach does not rely on data association knowledge.Using this method,two point clouds are properly pre-aligned.Hence,we can use ICP to fne-tune the transformation parameters and minimize registration error.Experimental results demonstrate the performance and stability of the proposed system under disturbance in real-time.Several indoor tests are carried out to show that the proposed visual odometry estimation method can help to signifcantly improve the accuracy of simultaneous localization and mapping（SLAM）.
基金supported by the National Natural Science Foundation of China(No.11902017)the China Postdoctoral Science Foundation(Nos.2020T130043,2019M650418).
文摘Numerous investigations have been conducted to understand the wall effects on rotors.The purpose of this study is to further investigate the aerodynamic performance of revolving wings,especially when it is very close to the ground and ceiling(i.e.,less than half the wingspan)at low Reynolds numbers.Hence,the ground and ceiling effect for hovering micro revolving wings at low Reynolds numbers are investigated by improving the theoretical models.The theoretical model for the ground effect is established based on the wall-jet assumption,and that for the ceiling effect is improved by considering the uneven spanwise distribution of induced velocity.These two models are validated by comparing the results of experiments and CFD simulations with the Lattice-Boltzmann Method(LBM).Both ground and ceiling effects are found helpful to enhance the thrust,especially with small wing-wall distances,by making a difference to the induced velocity and the pressure distribution.By comparing the thrust generation and aerodynamic efficiency between the ground and ceiling effects,the former is found more helpful to the thrust augmentation,and the latter is more beneficial for the aerodynamic efficiency promotion.
文摘This paper proposes modifications to the tradional Ceiling Bounce Model and uses it to characterize diffuse indoor optical wireless channel by analyzing the effect of transceiver position on signal propagation properties. The modified approach uses a combination of the tradional ceiling bounce method and a statistical approach. The effects of different transmitter-receiver separations and height of the ceiling on path loss and delay spread are studied in detail.
文摘The architectural?complexes?of Hasan Basha Tahir?were suffering from many damages and deformation in different elements as load bearing walls, arches and wooden ceiling. Ground water, salt weathering, air pollution, biological colonization and environmental aspects were the main degradation factors which caused a lot of damage and deterioration phenomena in the complexes. Horizontal and vertical cracks, salts, loss of decorations, and featured dark of the stone surface were noticed at the complexes elements. In addition, the celling of the complex was in a very bad condition;?it had lost a lot of decoration elements, cracking, soot deposition, insects’ holes, and fungi growth. This research will discuss the various deterioration phenomena that?have?effect on the main building materials and cause the damages and discuss the general scientific methodology of the architectural and structural conservation project which was?carried out.
文摘One quarter scale experiment device of a typical L-shape architecture structure including a burning room and an adjacent hallway is established to carry out the research.The smoke characteristics at the sampling points below the ceiling of the burning compartment and the roof of the hallway are studied systematically to find out the effects of different ceilings on the local fire origin compartment and the smoke transportation to a remote area.A series of tests is reported and the smoke residence time,the concentration peak and the concentration build up rate are investigated as functions of the type of the ceiling.The smoke residence time,the most important factor concerning smoke toxicity,is described by a novel concept,wavelength,in this study.Furthermore,it is worth emphasizing that the PVC ceiling exhibits a phenomenon of frequent collapse during the fire developing period.The single heat action is conducted to judge the smoke and the heat effect on the fire risk.
文摘Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.
文摘This paper presents an image-based mobile robot guidance system in an indoor space with installed artificial ceiling landmarks. The overall system, including an omni-directional mobile robot motion control, landmark image processing and image recognition, is implemented on a single FPGA chip with one CMOS image sensor. The proposed feature representation of the artificial ceiling landmarks is invariant with respect to rotation and translation. One unique feature of the proposed ceiling landmark recognition system is that the feature points of landmarks are determined by topological information from both the foreground and background. To enhance recognition accuracy, landmark classification is performed after the mobile robot is moved to a position such that the ceiling landmark is located in the upright- top corner position of the robot’s camera image. The accuracy of the proposed artificial ceiling landmark recognition system using the nearest neighbor classification is 100% in our experiments.
文摘Driven by the rapid economic development,the development of transportation in China has begun to move towards mountainous areas.The climate environment,topography and landform of mountainous cities are different from those of plain areas.In mountainous cities,the area of opposite interchanges between expressways and urban roads is generally large,which has a certain contradiction with the topographic conditions of mountainous cities.Therefore,it is necessary to reasonably design the opposite interchanges between expressways and urban roads in mountainous cities.The author explores and analyzes the factors restricting the special-shaped interchange between expressway and urban road in mountainous cities and the main fbnns of special-shaped interchange,and puts forward a reasonable design scheme,hoping to make a smooth development of the special-shaped interchange in mountainous cities.
文摘For special-shaped parts, the clamping and processing are very difficult. Based on this, a part with high precision and special shape is selected as a case. In-depth analysis of its structure and accuracy, scientific and reasonable formulation of the processing technology, at the same time, the complete involvement of special tooling and fixtures, so as to ensure the simplification of parts processing, and thus ensure the processing progress. At the same time, in order to effectively control the quality based on the accuracy and shape requirements of the parts themselves, if ordinary inspection equipment is applied, the purpose of inspection cannot be achieved. Therefore, according to the actual situation, special inspection tools should be designed to ensure the reliability and efficiency of the inspection. Based on this, this paper mainly analyzes and discusses the NC machining process analysis and testing of precision special-shaped parts.
文摘Due to the vigorous development of the market, the demands of urban residents for interior decoration of buildings are increasing day by day. In the actual building decoration process, as the indoor suspended ceiling and ceiling of the building are the key decoration parts, its construction quality will also directly affect the decoration quality in the building. Based on this, this chapter focuses on discussing and expounding the construction and handling skills of indoor suspended ceiling and ceiling decoration of buildings, with a view to promoting the development of China's architectural decoration industry.
文摘This work focuses on the estimation of a duty cycle of a radiant ceiling heating system with a panel surface temperature of 35℃and a heat flux of 65 W/m2 that corresponds to a thermal comfort for sedentary occupants.The results obtained are based on the theoretical heat transfer equations that govern the radiant and natural convection heat exchange mechanisms,and experimental heat transfer coefficients available in the literature.The results of the examined radiant heating system with specific conditions showed that a duty cycle of 6.46 min alternated by 13.36 min in shutting-down position is required to assure an acceptable thermal comfort for the enclosure space occupants.In addition,the study showed that for extremely cold-temperature conditions the heating system requires a daily operating load of about 61.2%which clearly proves the efficiency of these radiant heating systems in terms of energy consumption.
