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Compliant multistable structures are presented which exhibit a large geometric change when actuated between their stable states. It is demonstrated how asymmetric-bistability is achieved through the combination of linear and nonli...
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Compliant multistable structures are presented which exhibit a large geometric change when actuated between their stable states. It is demonstrated how asymmetric-bistability is achieved through the combination of linear and nonlinear springs. Finite element analytical techniques are provided which enable the design of such structures, and which illustrate how the presence of imperfections can substantially alter their structural performance. A multistable structure is developed which consists of four connected bistable tetrahedral units. The validity of the analytical techniques is confirmed through observation of several physical models. (C) 2008 Elsevier Ltd. All rights reserved.
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As technologies evolve, academia must follow suit to best use these technological strides to advance structures for better reliability and overall safety. One such advancement is subsumed under the title "smart structures," which ...
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As technologies evolve, academia must follow suit to best use these technological strides to advance structures for better reliability and overall safety. One such advancement is subsumed under the title "smart structures," which use smart materials possessing unique qualities to collectively generate an adaptive structural system. Although the smart structure concept is widely used in the mechanical and aerospace engineering industries, the civil engineering community has been slow to adopt it because of system complexity and high cost. In addition, many universities still do not include smart structures in their curricula, which has hindered their broad implementation into modern structures. This paper presents a specialized course on smart structures designed to further the use of smart technologies in engineering education and ultimately the real-world. Included in the background is a look at institutions that already provide classes on the subject and a description of how one school (i.e., Texas A&M University) organized the class, including lab demonstrations, homework, projects, and lecture outline, as well as student evaluations of the class.
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This paper presents a morphing blade design for wind turbine application with flexibility in chord-wise bending while providing sufficient stiffness to carry the aerodynamic loads. The NACA64 profile is selected for the camber mor...
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This paper presents a morphing blade design for wind turbine application with flexibility in chord-wise bending while providing sufficient stiffness to carry the aerodynamic loads. The NACA64 profile is selected for the camber morphing blade demonstrator. A corrugation concept is chosen because it is relatively easy to manufacture and provides sufficient stiffness to resist deformation due to the aerodynamic loads (through the provision of effective stringers) while providing the required flexibility for chord-wise bending. A mechanical actuation mechanism is employed to achieve the desired morphing angle and increase the stiffness of the morphing airfoil section to resist aerodynamic loading. The design of a morphing blade demonstrator is presented together with the manufacturing process. Finally, an experimental study is conducted where the morphing angle is measured for increasing actuation load and compared with FE analysis showing good agreement between the experimental results and results from the finite element analysis in addition to achieving the desired morphing angle.
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This article presents a novel bistable structural element that has high stiffness in stable configurations, but requires only a small amount of energy to be switched from one configuration to the other. The element is based on a p...
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This article presents a novel bistable structural element that has high stiffness in stable configurations, but requires only a small amount of energy to be switched from one configuration to the other. The element is based on a planar linkage of four bars connected by revolute joints, braced by tape-spring diagonals. A description of the concept is presented, along with a detailed theoretical analysis of its mechanical behaviour. Experimental measurements obtained from a prototype structure are found to be in very good agreement with the predictions from this analytical model.
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The article presents a review of recent research carried out in the Department of Intelligent Technologies of Institute of Fundamental Technological Research, dedicated to application of systems for adaptive impact absorption to a...
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The article presents a review of recent research carried out in the Department of Intelligent Technologies of Institute of Fundamental Technological Research, dedicated to application of systems for adaptive impact absorption to adaptive aircraft landing gears, novel concept of protective MFM structures, flow-control based airbags, maritime applications of inflatable structures, and development of adaptive wind turbine blade _ hub connections.
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Collisions with small service ships are serious danger for offshore wind turbines. Installing torus-shaped adaptive inflatable structure that surrounds a wind turbine tower at water level is one method of effective protection. Pro...
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Collisions with small service ships are serious danger for offshore wind turbines. Installing torus-shaped adaptive inflatable structure that surrounds a wind turbine tower at water level is one method of effective protection. Proposed pneumatic structure contains several separate air chambers equipped with devices for fast inflation and pressure release. The system can be adapted to various impact scenarios by adjusting the level of initial pressure in each chamber and by controlling the release of compressed air during collision. The paper presents finite element simulation of ship collision with wind turbine tower protected by pneumatic structure, conducted using ABAQUS software. Introduced methods of pressure adjustment are aimed at mitigating tower and ship response. The performed feasibility study proves that inflatable structure can effectively protect the wind turbine tower and the ship against serious damage.
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This paper addresses the formulation of adaptive morphological filters based on spatially variant structuring elements. The adaptivity of these filters is achieved by modifying the shape and orientation of the structuring elements...
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This paper addresses the formulation of adaptive morphological filters based on spatially variant structuring elements. The adaptivity of these filters is achieved by modifying the shape and orientation of the structuring elements according to a multiple orientation vector field. This vector field is provided by means of a bank of directional openings which can take into account the possible multiple orientations of the contours in the image. After reviewing and formalizing the definition of the spatially-variant dilation, erosion, opening and closing, the proposed structuring elements are described. These spatially variant structuring elements are based on ellipses which vary over the image domain adapting locally their orientation according to the multiple orientation vector field and their shape (the eccentricity of the ellipses) according to the distance to relevant contours of the objects. The proposed adaptive morphological filters are used on gray-level images and are compared with spatially-invariant filters, with spatially-variant filters based on a single orientation vector field, and with adaptive morphological bilateral filters. Results show that the morphological filters based on a multiple orientation vector field are more adept at enhancing and preserving structures which contains more than one orientation. (C) 2017 Elsevier B.V. All rights reserved.
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Applying adaptronics to helicopters has a high potential to significantly suppress noise, reduce vibration, and increase the overall aerodynamic efficiency. This paper presents recent investigations o a very promising specific con...
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Applying adaptronics to helicopters has a high potential to significantly suppress noise, reduce vibration, and increase the overall aerodynamic efficiency. This paper presents recent investigations o a very promising specific concept described as Adaptive Blade Twist (ABT). This concept allows us to directly control the twist of the helicopter blades by smart adaptive elements. This influences positively the main rotor area which is the primary source for helicopter noise and vibration. Since the interaction of non-stationary helicopter aerodynamics and elastomechanical structural characteristics f the helicopter blades causes flight envelope limitations, vibration and noise, a good comprehension of the aerodynamics is essential for the development of structural solutions to effectively influence the local airflow conditions and finally develop the structural concept. With respect to these considerations, the ABT concept will be presented.
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Empirical works have shown rising urban floods in Ghana and the associated household vulnerabilities. However, the flood response mechanisms by households remain inadequately understood. This paper, therefore, analyses the dynamic...
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Empirical works have shown rising urban floods in Ghana and the associated household vulnerabilities. However, the flood response mechanisms by households remain inadequately understood. This paper, therefore, analyses the dynamics of urban floods and the response mechanisms of flood-prone community-dwelling households in Greater Kumasi, Ghana using a concurrent triangulation mixed method design. The quantitative data were analysed using descriptive statistical tools in IBM SPSS (Version 21) while the qualitative data were analysed using NVivo 12 analytical software. The results showed that households employed different flood coping strategies including bailing out of the water, placing valuable items above the ground level, and seeking support from neighbours. Adaptation took the form of massive use of concrete flood defence walls and elevated entrances, the use of sandbags as embarkments, and reinforced building foundations with concrete work. The uncoordinated nature of these individual strategies coupled with overdependence on the structural defence mechanisms made these response mechanisms less effective. For effective flood control, a site-specific mix of structural and non-structural flood control mechanisms is recommended. Crucially, it demands strict enforcement of land use regulations, land use, and development control, and sustained community sensitisation on the risks of non-adherence to land use regulations.
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