Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between...Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between supply and exhaust air volumes.The door gap is the channel of air flow between rooms,so its height has an important influence on the pressure difference and infiltration air volume of the room.There is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the building.In this study,model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM,and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases department.The results show that in a building with ventilation system divided by functional area,the difference in the height of the door gaps requires different active infiltration air volumes.Pressure fluctuations in the medical and patient corridors are greater than in other rooms.The significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 patients.It is also instructive for the design of pressure gradients in clean workshops,biological laboratories,and other similar buildings.展开更多
Osteochondral(OC)repair is an extremely challenging topic due to the complex biphasic structure and poor intrinsic regenerative capability of natural osteochondral tissue.In contrast to the current surgical approaches...Osteochondral(OC)repair is an extremely challenging topic due to the complex biphasic structure and poor intrinsic regenerative capability of natural osteochondral tissue.In contrast to the current surgical approaches which yield only short-term relief of symptoms,tissue engineering strategy has been shown more promising outcomes in treating OC defects since its emergence in the 1990s.In particular,the use of multizonal scaffolds(MZSs)that mimic the gradient transitions,from cartilage surface to the subchondral bone with either continuous or discontinuous compositions,structures,and properties of natural OC tissue,has been gaining momentum in recent years.Scrutinizing the latest developments in the field,this review offers a comprehensive summary of recent advances,current hurdles,and future perspectives of OC repair,particularly the use of MZSs including bilayered,trilayered,multilayered,and gradient scaffolds,by bringing together onerous demands of architecture designs,material selections,manufacturing techniques as well as the choices of growth factors and cells,each of which possesses its unique challenges and opportunities.展开更多
Natural ventilation is particularly important for residential high-rise buildings as it maintains indoor human comfort without incurring the energy demands that air-conditioning does.To improve a building’s natural v...Natural ventilation is particularly important for residential high-rise buildings as it maintains indoor human comfort without incurring the energy demands that air-conditioning does.To improve a building’s natural ventilation,it is essential to develop models to understand the relationship between wind flow characteristics and the building's design.Significantly more effort is still needed for developing such reliable,accurate,and computationally economical models instead of currently the most popular physics-based models such as computational fluid dynamics(CFD)simulation.This paper,therefore,presents a novel model developed based on physics-based modelling and a data-driven approach to evaluate natural ventilation in residential high-rise buildings.The model first uses CFD to simulate wind pressures on the exterior surfaces of a high-rise building.Once the surface pressures have been obtained,multizone modelling is used to predict the air change per hour(ACH)for different flats in various configurations.Data-driven prediction models are then developed using data from the simulation and deep neural networks that are based on mean absolute error,mean absolute percentage error,and a fusion algorithm respectively.These data-driven models are used to predict the ACH of 25 flats.The results from multizone modelling and data-driven modelling are compared.The results imply a high accuracy of the data-driven prediction in comparison with physics-based models.The fusion algorithm-based neural network performs best,achieving 96%accuracy,which is the highest of all models tested.This study contributes a more efficient and robust method for predicting wind-induced natural ventilation.The findings describe the relationship between building design(e.g.,plan layout),distribution of surface pressure,and the resulting ACH,which serve to improve the practical design of sustainable buildings.展开更多
A piecewise-smooth second-order singularly perturbed differential equation whose right-hand side is a nonlinear function with a discontinuity on some curve is investigated. This is a new class of problems in the case ...A piecewise-smooth second-order singularly perturbed differential equation whose right-hand side is a nonlinear function with a discontinuity on some curve is investigated. This is a new class of problems in the case where the degenerate equation has a multiple root on the left-hand side of the curve which separates the domain and an isolated root on the right-hand side of that curve. The asymptotics of a solution with an internal layer near a point on the discontinuous curve and the transition point is constructed. The method to construct the internal layer function is proposed. The behavior of the solution in the internal layer consisting of four zones essentially differs from the case of isolated roots. For sufficiently small parameter values, the existence of a smooth solution with an internal layer from the multiple root of the degenerate equation to the isolated root in the neighborhood of a point on the discontinuous curve is proved. The method can be shown to be effective in the given example.展开更多
文摘Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between supply and exhaust air volumes.The door gap is the channel of air flow between rooms,so its height has an important influence on the pressure difference and infiltration air volume of the room.There is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the building.In this study,model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM,and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases department.The results show that in a building with ventilation system divided by functional area,the difference in the height of the door gaps requires different active infiltration air volumes.Pressure fluctuations in the medical and patient corridors are greater than in other rooms.The significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 patients.It is also instructive for the design of pressure gradients in clean workshops,biological laboratories,and other similar buildings.
文摘Osteochondral(OC)repair is an extremely challenging topic due to the complex biphasic structure and poor intrinsic regenerative capability of natural osteochondral tissue.In contrast to the current surgical approaches which yield only short-term relief of symptoms,tissue engineering strategy has been shown more promising outcomes in treating OC defects since its emergence in the 1990s.In particular,the use of multizonal scaffolds(MZSs)that mimic the gradient transitions,from cartilage surface to the subchondral bone with either continuous or discontinuous compositions,structures,and properties of natural OC tissue,has been gaining momentum in recent years.Scrutinizing the latest developments in the field,this review offers a comprehensive summary of recent advances,current hurdles,and future perspectives of OC repair,particularly the use of MZSs including bilayered,trilayered,multilayered,and gradient scaffolds,by bringing together onerous demands of architecture designs,material selections,manufacturing techniques as well as the choices of growth factors and cells,each of which possesses its unique challenges and opportunities.
基金supported by the Hong Kong University of Science and Technology Research Grant(project no.IGN17EG04).
文摘Natural ventilation is particularly important for residential high-rise buildings as it maintains indoor human comfort without incurring the energy demands that air-conditioning does.To improve a building’s natural ventilation,it is essential to develop models to understand the relationship between wind flow characteristics and the building's design.Significantly more effort is still needed for developing such reliable,accurate,and computationally economical models instead of currently the most popular physics-based models such as computational fluid dynamics(CFD)simulation.This paper,therefore,presents a novel model developed based on physics-based modelling and a data-driven approach to evaluate natural ventilation in residential high-rise buildings.The model first uses CFD to simulate wind pressures on the exterior surfaces of a high-rise building.Once the surface pressures have been obtained,multizone modelling is used to predict the air change per hour(ACH)for different flats in various configurations.Data-driven prediction models are then developed using data from the simulation and deep neural networks that are based on mean absolute error,mean absolute percentage error,and a fusion algorithm respectively.These data-driven models are used to predict the ACH of 25 flats.The results from multizone modelling and data-driven modelling are compared.The results imply a high accuracy of the data-driven prediction in comparison with physics-based models.The fusion algorithm-based neural network performs best,achieving 96%accuracy,which is the highest of all models tested.This study contributes a more efficient and robust method for predicting wind-induced natural ventilation.The findings describe the relationship between building design(e.g.,plan layout),distribution of surface pressure,and the resulting ACH,which serve to improve the practical design of sustainable buildings.
基金supported by National Natural Science Foundation of China(Grant No.11871217)the Science and Technology Commission of Shanghai Municipality(Grant No.18dz2271000)。
文摘A piecewise-smooth second-order singularly perturbed differential equation whose right-hand side is a nonlinear function with a discontinuity on some curve is investigated. This is a new class of problems in the case where the degenerate equation has a multiple root on the left-hand side of the curve which separates the domain and an isolated root on the right-hand side of that curve. The asymptotics of a solution with an internal layer near a point on the discontinuous curve and the transition point is constructed. The method to construct the internal layer function is proposed. The behavior of the solution in the internal layer consisting of four zones essentially differs from the case of isolated roots. For sufficiently small parameter values, the existence of a smooth solution with an internal layer from the multiple root of the degenerate equation to the isolated root in the neighborhood of a point on the discontinuous curve is proved. The method can be shown to be effective in the given example.
