For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boun...For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boundary element method(BEM) were adopted in numerical calculations,and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function,the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example,the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective.展开更多
To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blas...To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blast loading.First,the dynamic strain response and morphology of impact damage of the new pre-separation panel were measured in an impact damage test.Second,the commercial software LS-DYNA was used to calculate the propagation of the blast shock wave,and the results were compared with empirical equations to verify the rationality of the numerical calculation method.Finally,the fluid–structure coupling method was used to calculate the damage process of the pre-separation panel structure under the impact of an explosion wave and an impact block.The calculated results were in good agreement with the test results,which showed the rationality of the calculation method and the model.The residual strength of the damaged pre-separation panel was significantly higher than that of the original damaged panel.The results show that the new pre-separation panel structure is reasonable and has certain significance for guiding the design of plenum chambers with strong resistance to implosion for aircraft fuselages.展开更多
The factors that influence the economic growth are various and complicated.This paper has especially probed into calculating and impact on regional economic growth of the human capital structure. First, on the basis o...The factors that influence the economic growth are various and complicated.This paper has especially probed into calculating and impact on regional economic growth of the human capital structure. First, on the basis of considering human capital quality, we use Gini coefficient law to calculate human capital structure coefficient of our country＇s each province （municipal or district）; Second, according to the result of calculating of human capital structure coefficient, considering input of material capital, average education level and so on at the same time, we set up regional economic growth model and use the panel data to examine the model. The result indicates the human capital structure coefficient of each province （municipal or district）in inverse proportion to economic growth （- 0. 108）. The last is the conclusion of this text.展开更多
Flutter is a self‐excited vibration under the interaction of the inertial force,aero-dynamic force,and elastic force of the structure.After the flutter occurs,the aircraft structures will exhibit limit cycle oscillat...Flutter is a self‐excited vibration under the interaction of the inertial force,aero-dynamic force,and elastic force of the structure.After the flutter occurs,the aircraft structures will exhibit limit cycle oscillation,which will cause catastrophic accidents or fatigue damage to the structures.Therefore,it is of great theoretical and practical significance to study the aeroelastic characteristics and flutter control for improving the aeroelastic stability of aircraft structures.This paper reviews the recent advances in aeroelastic analysis and flutter control of wings and panel structures.The me-chanism of aeroelastic flutter of wings and panels is presented.The research methods of aeroelastic flutter for different structures developed in recent years are briefly summarized.Various control strategies including the linear and nonlinear control algorithms as well as the active flutter control results of wings and panels are presented.Finally,the paper ends with conclusions,which highlight challenges of the development in aeroelastic analysis and flutter control,and provide a brief outlook on the future investigations.This study aims to present a comprehensive under-standing of aeroelastic analysis and flutter control.It can also provide guidance on the design of new wings and panel structures for improving their aeroelastic stability.展开更多
The use of structural insulated panels(SIPs)for wall and roof assemblies in residential and commercial buildings is a well-known construction technique.SIPs typically use a combination of either expanded polystyrene f...The use of structural insulated panels(SIPs)for wall and roof assemblies in residential and commercial buildings is a well-known construction technique.SIPs typically use a combination of either expanded polystyrene foam(EPS)or polyurethane foam(PUR)as the core material.The covering or skin is predominantly oriented strand board(OSB).The OSB is either bonded to the foam with adhesive in the case of EPS,while polyurethane is used to provide adhesion with PUR SIPs.This paper presents the results of research that investigated the use of industrial hemp mat used as a skin for soy-based polyurethane foam panels.A series of tests were conducted to investigate moisture resistance and flexural behaviour on hemp mat foam panels.Moisture absorption behaviour was evaluated on three specimen types:uncoated,earth plaster and tung oil treated hemp mat.The absorption coefficient Aw was determined for all specimens.The tung oil treated specimens exhibited a water absorption coefficient that was 5.3%of that for untreated hemp mat panel specimens.Flexural tests were conducted on dry specimens with earth-plastered hemp mat,tung oil coated hemp mat,OSB and,untreated hemp mat skins.Tung oil provided resistance to tension failure and increased capacity to withstand considerable deformation without tensile failure in flexural specimens.Compared with pure foam specimens,untreated hemp mat improved flexural performance by 16.3%.展开更多
Acoustic structure study always is the academic research interest. Diffusion ab？sorbing structure（DiflFsorber） has good research value because it has both diflFusion property and sound absorption property. Quadrati...Acoustic structure study always is the academic research interest. Diffusion ab？sorbing structure（DiflFsorber） has good research value because it has both diflFusion property and sound absorption property. Quadratic residue diffusers（QRD） structure which had good diffusion property was combined with the perforated panel which had good sound absorption property in this study. According to standard AES-4id-2001, the diffusion experiments were carried out to study QRD structure and ones composited with perforated-panels which had1 mm-thickness and perforated percentage of 3%, 5%, 8% respectively. The polar coordinate diagrams of different structure were analyzed to derive the diffusion coefficients. Results showed that the composite structure still had good diffusion performance in the frequency range from100 Hz to 800 Hz. The reflection sound energy of composite structure reduced obviously in the perforated panel resonance frequency range where there was about 2 dB reduction averagely.The study result can provide the reference for the design and development of diifsorber.展开更多
The energy efficiency of a building depends on building envelope performance.The results presented in this paper are the first of a long-term building envelope research project at the Alternative Village at the Univer...The energy efficiency of a building depends on building envelope performance.The results presented in this paper are the first of a long-term building envelope research project at the Alternative Village at the University of Manitoba in Winnipeg,Manitoba,Canada.Five test buildings were constructed using the following systems:two wood frames with fiberglass batt insulation and dense pack cellulose,one polyurethane structural insulated panels(PUR SIP),and two with the Stay in place PVC concrete form building system using 102mm and 204mm of concrete externally insulated with 102mm of expanded polystyrene foam.All of the buildings had a common foundation and roof system with a footprint of 23.8 m2.Blower door tests were conducted to determine air tightness.Each structure was heated with an electrical resistance heater and maintained at a constant internal temperature.The thermal gradient through the wall and power consumption were monitored.The study period discussed in this report represents the main heating season from October 2011 to April 2012 consisting of 209 days.Based on the power consumption,the PUR SIP consumed the least at 2498 kWh,while the 204 mm Stay in place PVC concrete form building used the most at 2898 kWh for the same time period.The thermal gradient through the cross section of the wood frame structures was compared through the cavity insulation and at the stud.It was found that the cellulose building provided better thermal resistance along the stud when compared to the fiberglass batt insulation.展开更多
文摘For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boundary element method(BEM) were adopted in numerical calculations,and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function,the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example,the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective.
文摘To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blast loading.First,the dynamic strain response and morphology of impact damage of the new pre-separation panel were measured in an impact damage test.Second,the commercial software LS-DYNA was used to calculate the propagation of the blast shock wave,and the results were compared with empirical equations to verify the rationality of the numerical calculation method.Finally,the fluid–structure coupling method was used to calculate the damage process of the pre-separation panel structure under the impact of an explosion wave and an impact block.The calculated results were in good agreement with the test results,which showed the rationality of the calculation method and the model.The residual strength of the damaged pre-separation panel was significantly higher than that of the original damaged panel.The results show that the new pre-separation panel structure is reasonable and has certain significance for guiding the design of plenum chambers with strong resistance to implosion for aircraft fuselages.
文摘The factors that influence the economic growth are various and complicated.This paper has especially probed into calculating and impact on regional economic growth of the human capital structure. First, on the basis of considering human capital quality, we use Gini coefficient law to calculate human capital structure coefficient of our country＇s each province （municipal or district）; Second, according to the result of calculating of human capital structure coefficient, considering input of material capital, average education level and so on at the same time, we set up regional economic growth model and use the panel data to examine the model. The result indicates the human capital structure coefficient of each province （municipal or district）in inverse proportion to economic growth （- 0. 108）. The last is the conclusion of this text.
基金National Natural Science Foundation of China,Grant/Award Numbers:12072083,11761131006German Research Foundation,Grant/Award Number:ZH 15/30‐1。
文摘Flutter is a self‐excited vibration under the interaction of the inertial force,aero-dynamic force,and elastic force of the structure.After the flutter occurs,the aircraft structures will exhibit limit cycle oscillation,which will cause catastrophic accidents or fatigue damage to the structures.Therefore,it is of great theoretical and practical significance to study the aeroelastic characteristics and flutter control for improving the aeroelastic stability of aircraft structures.This paper reviews the recent advances in aeroelastic analysis and flutter control of wings and panel structures.The me-chanism of aeroelastic flutter of wings and panels is presented.The research methods of aeroelastic flutter for different structures developed in recent years are briefly summarized.Various control strategies including the linear and nonlinear control algorithms as well as the active flutter control results of wings and panels are presented.Finally,the paper ends with conclusions,which highlight challenges of the development in aeroelastic analysis and flutter control,and provide a brief outlook on the future investigations.This study aims to present a comprehensive under-standing of aeroelastic analysis and flutter control.It can also provide guidance on the design of new wings and panel structures for improving their aeroelastic stability.
文摘The use of structural insulated panels(SIPs)for wall and roof assemblies in residential and commercial buildings is a well-known construction technique.SIPs typically use a combination of either expanded polystyrene foam(EPS)or polyurethane foam(PUR)as the core material.The covering or skin is predominantly oriented strand board(OSB).The OSB is either bonded to the foam with adhesive in the case of EPS,while polyurethane is used to provide adhesion with PUR SIPs.This paper presents the results of research that investigated the use of industrial hemp mat used as a skin for soy-based polyurethane foam panels.A series of tests were conducted to investigate moisture resistance and flexural behaviour on hemp mat foam panels.Moisture absorption behaviour was evaluated on three specimen types:uncoated,earth plaster and tung oil treated hemp mat.The absorption coefficient Aw was determined for all specimens.The tung oil treated specimens exhibited a water absorption coefficient that was 5.3%of that for untreated hemp mat panel specimens.Flexural tests were conducted on dry specimens with earth-plastered hemp mat,tung oil coated hemp mat,OSB and,untreated hemp mat skins.Tung oil provided resistance to tension failure and increased capacity to withstand considerable deformation without tensile failure in flexural specimens.Compared with pure foam specimens,untreated hemp mat improved flexural performance by 16.3%.
基金supported by the National Natural Science Foundation of China(11004133)open project of China communication and transportation industry key laboratory of environmental technology
文摘Acoustic structure study always is the academic research interest. Diffusion ab？sorbing structure（DiflFsorber） has good research value because it has both diflFusion property and sound absorption property. Quadratic residue diffusers（QRD） structure which had good diffusion property was combined with the perforated panel which had good sound absorption property in this study. According to standard AES-4id-2001, the diffusion experiments were carried out to study QRD structure and ones composited with perforated-panels which had1 mm-thickness and perforated percentage of 3%, 5%, 8% respectively. The polar coordinate diagrams of different structure were analyzed to derive the diffusion coefficients. Results showed that the composite structure still had good diffusion performance in the frequency range from100 Hz to 800 Hz. The reflection sound energy of composite structure reduced obviously in the perforated panel resonance frequency range where there was about 2 dB reduction averagely.The study result can provide the reference for the design and development of diifsorber.
文摘The energy efficiency of a building depends on building envelope performance.The results presented in this paper are the first of a long-term building envelope research project at the Alternative Village at the University of Manitoba in Winnipeg,Manitoba,Canada.Five test buildings were constructed using the following systems:two wood frames with fiberglass batt insulation and dense pack cellulose,one polyurethane structural insulated panels(PUR SIP),and two with the Stay in place PVC concrete form building system using 102mm and 204mm of concrete externally insulated with 102mm of expanded polystyrene foam.All of the buildings had a common foundation and roof system with a footprint of 23.8 m2.Blower door tests were conducted to determine air tightness.Each structure was heated with an electrical resistance heater and maintained at a constant internal temperature.The thermal gradient through the wall and power consumption were monitored.The study period discussed in this report represents the main heating season from October 2011 to April 2012 consisting of 209 days.Based on the power consumption,the PUR SIP consumed the least at 2498 kWh,while the 204 mm Stay in place PVC concrete form building used the most at 2898 kWh for the same time period.The thermal gradient through the cross section of the wood frame structures was compared through the cavity insulation and at the stud.It was found that the cellulose building provided better thermal resistance along the stud when compared to the fiberglass batt insulation.
