In order to promote convenient strategies for the utilization of wood wastes from aucoumea klaineana pierre(okoume)timber industry,various chemical analysis were carried out on samples from different origins.Total ext...In order to promote convenient strategies for the utilization of wood wastes from aucoumea klaineana pierre(okoume)timber industry,various chemical analysis were carried out on samples from different origins.Total extractives content of the bark,sapwood and heartwood of okoume were evaluated.thermogravimetric analyses were performed and the stiasny number was calculated.it was found that the bark was richer in fatty acid of high molecular weight while the sapwood was rich in fatty acid of low molecular weight.the condensed tannins content varied according to the origin and the part of the tree.these new findings should be useful for green okoume based tannin adhesives.展开更多
This paper examines the use of proper orthogonal decomposition (POD) and singular value decomposition (SVD) to identify zones on the surface of the source that contribute the most to the sound power the source radiate...This paper examines the use of proper orthogonal decomposition (POD) and singular value decomposition (SVD) to identify zones on the surface of the source that contribute the most to the sound power the source radiates. First, computational fluid dynamics (CFD) is used to obtain the pressure field at the surface of the blade in a subsonic regime. Then the fluctuation of this pressure field is used as the input for the loading noise in the Ffowcs Williams and Hawkings (FW&H) acoustic analogy. The FW&H analogy is used to calculate the sound power that is radiated by the blade. Secondly, the most important acoustic modes of POD and SVD are used to reconstruct the radiated sound power. The results obtained through POD and SVD are similar to the acoustic power directly obtained with the FW&H analogy. It was observed that the importance of the modes to the radiated sound power is not necessarily in ascending order (for the studied case, the seventh mode was the main contributor). Finally, maps of the most contributing POD and SVD modes have been produced. These maps show the zones on the surface of the blade, where the dipolar aeroacoustic sources contribute the most to the radiated sound power. These identifications are expected to be used as a guide to design and shape the blade surface in order to reduce its radiated noise.展开更多
The purpose of the study is to assess what the influence of the distance of the gap is between the wing and slotted flap on the aerodynamic characteristics of ultra-light aircraft wing when the flap is retracted. It h...The purpose of the study is to assess what the influence of the distance of the gap is between the wing and slotted flap on the aerodynamic characteristics of ultra-light aircraft wing when the flap is retracted. It has been elected numerical approach to the study and it is been realized through applied numerical model of the wing airfoil NACA 2412 for three different lengths of slotted gap size, whose length is expressed as percentages of the airfoil chord. The code ANSYS FLUENT has been applied, as it has been determined RANS （Reynolds-averaged Navier-Stokes） equations and DES （detached-eddy simulation） turbulent model has been used.展开更多
The problematic of energy management, particularly in terms of resources control and efficiency, has become in the space of a few years an eminently strategic subject. Its implementation is both complex and exciting a...The problematic of energy management, particularly in terms of resources control and efficiency, has become in the space of a few years an eminently strategic subject. Its implementation is both complex and exciting as the prospects are promising, especially in relation with smart grids technologies. The deregulation of the electricity market, the high cost of storage, and the new laws on energy transition incite some significant users (collectivities, cities, regions, etc.) to form themselves into local producers in order to gain autonomy and reduce their energy bills. Thus, they may have their own sources (classic and/or renewable energy sources) to satisfy their needs and sell their excess production instead of storing it. In this idea, the territorial interconnection principle offers several advantages (energy efficiency, environmental protection, better economic balance). The main challenge of such systems is to ensure good energy management. Therefore, power distribution strategy must be implemented by matching the supply and the demand. Such systems have to be financially viable and environmentally sustainable. This allows among others to reduce the electricity bill and limit the systematic use of the national power network, typically using non-renewable sources, and thereby support sustainable development. This paper presents an original model for aid-decision in terms of grid configurations and control powers exchanged between interconnected territories. The model is based on Petri nets. Therefore, an iterative algorithm for power flow management is based on instantaneous gap between the production capability (photovoltaic, wind) and the demand of each user. So, in order to validate our model, we selected three French regions: the PACA region, the Champagne-Ardenne region and the Lorraine region. Due to their policy, their geographical and climatic features, we opted for two renewable sources: “wind” and “photovoltaic”. The numerical simulations are performed using the instantaneous productions of each region and their energy demand for a typical summer day. A detailed economic analysis is performed for two scenarios (with or without interconnections). The results show that the use of renewable energy in an interconnection context (i.e. pooling), offers serious economic and technical advantages.展开更多
Complexity is commonly summarized as‘the actions of the whole are more than the sum of the actions of the parts’.Understanding how the coherence emerges from these natural and artificial systems provides a radical s...Complexity is commonly summarized as‘the actions of the whole are more than the sum of the actions of the parts’.Understanding how the coherence emerges from these natural and artificial systems provides a radical shift in the process of thought,and brings huge promises for controlling and fostering this emergence.The authors define the term‘Complex System Engineering’to denote this approach,which aims at transferring the radical insights from Complex System Science to the pragmatic world of engineering,especially in the Computing System Engineering domain.A theoretical framework for Complex System Engineering is built by the morphogenetic engineering framework,which identifies a graduation of models,in growing order of generative power.The implementation of Complex System Engineering requires a portfolio of operational solutions:The authors therefore provide a classification of Complex System application approaches to answer this challenge and support the emergence of Complex System Engineers capable of addressing the issues of an ever more connected world.展开更多
This paper deals with a design methodology of permanent magnets(PM)generators used for fixed-pitch tidal turbines in a marine renewable energy context.In the case of underwater turbines,fixed-pitch tidal turbines coul...This paper deals with a design methodology of permanent magnets(PM)generators used for fixed-pitch tidal turbines in a marine renewable energy context.In the case of underwater turbines,fixed-pitch tidal turbines could be very attractive and interesting to reduce maintenance operation by avoiding using such a complex electromechanical system for blade-pitching.In this technological case,one of the main control challenges is to ensure power limitation at high tidal current velocities.This control mode can be achieved using the generator flux-weakening.In this context,this paper proposes an original and systemic design methodology to optimize the generator design taking into account the tidal turbine power limitation for high tidal currents velocities.展开更多
文摘In order to promote convenient strategies for the utilization of wood wastes from aucoumea klaineana pierre(okoume)timber industry,various chemical analysis were carried out on samples from different origins.Total extractives content of the bark,sapwood and heartwood of okoume were evaluated.thermogravimetric analyses were performed and the stiasny number was calculated.it was found that the bark was richer in fatty acid of high molecular weight while the sapwood was rich in fatty acid of low molecular weight.the condensed tannins content varied according to the origin and the part of the tree.these new findings should be useful for green okoume based tannin adhesives.
文摘This paper examines the use of proper orthogonal decomposition (POD) and singular value decomposition (SVD) to identify zones on the surface of the source that contribute the most to the sound power the source radiates. First, computational fluid dynamics (CFD) is used to obtain the pressure field at the surface of the blade in a subsonic regime. Then the fluctuation of this pressure field is used as the input for the loading noise in the Ffowcs Williams and Hawkings (FW&H) acoustic analogy. The FW&H analogy is used to calculate the sound power that is radiated by the blade. Secondly, the most important acoustic modes of POD and SVD are used to reconstruct the radiated sound power. The results obtained through POD and SVD are similar to the acoustic power directly obtained with the FW&H analogy. It was observed that the importance of the modes to the radiated sound power is not necessarily in ascending order (for the studied case, the seventh mode was the main contributor). Finally, maps of the most contributing POD and SVD modes have been produced. These maps show the zones on the surface of the blade, where the dipolar aeroacoustic sources contribute the most to the radiated sound power. These identifications are expected to be used as a guide to design and shape the blade surface in order to reduce its radiated noise.
文摘The purpose of the study is to assess what the influence of the distance of the gap is between the wing and slotted flap on the aerodynamic characteristics of ultra-light aircraft wing when the flap is retracted. It has been elected numerical approach to the study and it is been realized through applied numerical model of the wing airfoil NACA 2412 for three different lengths of slotted gap size, whose length is expressed as percentages of the airfoil chord. The code ANSYS FLUENT has been applied, as it has been determined RANS （Reynolds-averaged Navier-Stokes） equations and DES （detached-eddy simulation） turbulent model has been used.
文摘The problematic of energy management, particularly in terms of resources control and efficiency, has become in the space of a few years an eminently strategic subject. Its implementation is both complex and exciting as the prospects are promising, especially in relation with smart grids technologies. The deregulation of the electricity market, the high cost of storage, and the new laws on energy transition incite some significant users (collectivities, cities, regions, etc.) to form themselves into local producers in order to gain autonomy and reduce their energy bills. Thus, they may have their own sources (classic and/or renewable energy sources) to satisfy their needs and sell their excess production instead of storing it. In this idea, the territorial interconnection principle offers several advantages (energy efficiency, environmental protection, better economic balance). The main challenge of such systems is to ensure good energy management. Therefore, power distribution strategy must be implemented by matching the supply and the demand. Such systems have to be financially viable and environmentally sustainable. This allows among others to reduce the electricity bill and limit the systematic use of the national power network, typically using non-renewable sources, and thereby support sustainable development. This paper presents an original model for aid-decision in terms of grid configurations and control powers exchanged between interconnected territories. The model is based on Petri nets. Therefore, an iterative algorithm for power flow management is based on instantaneous gap between the production capability (photovoltaic, wind) and the demand of each user. So, in order to validate our model, we selected three French regions: the PACA region, the Champagne-Ardenne region and the Lorraine region. Due to their policy, their geographical and climatic features, we opted for two renewable sources: “wind” and “photovoltaic”. The numerical simulations are performed using the instantaneous productions of each region and their energy demand for a typical summer day. A detailed economic analysis is performed for two scenarios (with or without interconnections). The results show that the use of renewable energy in an interconnection context (i.e. pooling), offers serious economic and technical advantages.
文摘Complexity is commonly summarized as‘the actions of the whole are more than the sum of the actions of the parts’.Understanding how the coherence emerges from these natural and artificial systems provides a radical shift in the process of thought,and brings huge promises for controlling and fostering this emergence.The authors define the term‘Complex System Engineering’to denote this approach,which aims at transferring the radical insights from Complex System Science to the pragmatic world of engineering,especially in the Computing System Engineering domain.A theoretical framework for Complex System Engineering is built by the morphogenetic engineering framework,which identifies a graduation of models,in growing order of generative power.The implementation of Complex System Engineering requires a portfolio of operational solutions:The authors therefore provide a classification of Complex System application approaches to answer this challenge and support the emergence of Complex System Engineers capable of addressing the issues of an ever more connected world.
文摘This paper deals with a design methodology of permanent magnets(PM)generators used for fixed-pitch tidal turbines in a marine renewable energy context.In the case of underwater turbines,fixed-pitch tidal turbines could be very attractive and interesting to reduce maintenance operation by avoiding using such a complex electromechanical system for blade-pitching.In this technological case,one of the main control challenges is to ensure power limitation at high tidal current velocities.This control mode can be achieved using the generator flux-weakening.In this context,this paper proposes an original and systemic design methodology to optimize the generator design taking into account the tidal turbine power limitation for high tidal currents velocities.
