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In this article, the role of the restoring stiffness, as one of the basic parameters in ship hydroelastic analysis, is brought
out. It is formulated using the variational principle and the method of virtual displacements. It is shown that asymmetry
of the restoring stiffness is a physical reality. Moreover, it is confirmed that modal variation, still disputed in the relevant
literature, has to be taken into account to satisfy the ship’s stability. Consistent stiffness is formulated here by regarding
stiffness definition as relation between forces and displacements. Hybrid stiffness known from the literature is wrong since
some terms are specified as relation between forces and displacement gradient. Influence of the consistent and symmetrized
stiffness matrix, and the hybrid one, on dynamic response is illustrated for a prismatic pontoon and a large container ship.
It is found that the latter two matrices do not assure convergence of transfer functions of sectional forces to zero value
as the wave frequency approaches zero. The rigid body and elastic responses are compared, and pertinent conclusions are drawn.
It is also shown that it is not necessary to use the unified geometric and restoring stiffness for ordinary hydroelastic analysis
of ship structures. The consistent formulation of the restoring stiffness matrix will be useful for extending linear potential
theory hydrodynamic codes for rigid body analysis to deformable bodies. 相似文献
93.
Ervin Kamenar Saša Zelenika David Blažević Senka Maćešić Goran Gregov Kristina Marković Vladimir Glažar 《Microsystem Technologies》2016,22(7):1557-1574
River courses play a vital role in preserving unpolluted ecosystems. On the other hand, networks of sensor nodes can be used to measure characteristic parameters in the environment such as temperature, pressure, humidity or the concentration of pollutants. In the framework of the EU FP7 project “GOLDFISH”, technical competences of a consortium of 11 institutions are hence employed in designing, manufacturing, validating and operating wireless sensors nodes for tracking pollution in remote rivers. The sensor network is composed of sensor clusters located underwater and gateways on the riverbank with long-distance communication links to the central management and monitoring station. Each sensor node is composed of active electronic devices that have to be constantly powered. Batteries can generally be used for this purpose, but problems may occur when they are to be recharged or replaced, especially in the case of large networks placed in scarcely accessible locations. State-of-the-art energy harvesting technologies can hence constitute a viable powering solution. The possibility to use different small-scale river flow energy harvesting principles is thoroughly studied in this work by the University of Rijeka GOLDFISH team: a miniaturized hydro-generator, a ‘piezoelectric eel’ and a hybrid solution of a rotating shaft plucking a piezoelectric beam. The first two concepts are validated experimentally in a flow channel and in real river conditions. The miniaturized hydro-generator with suitable power management electronics is finally embedded into the wireless sensor node deployed into the river, allowing the GSM transmission of collected data to be successfully performed. 相似文献
94.
Srećko Manasijević Natalija Dolić Zdenka Zovko Brodarac Mile Djurdjević Radomir Radiša 《Metallurgical and Materials Transactions A》2014,45(10):4580-4587
This paper presents the results of an analysis of the formation of an intermetallic bond between a ring carrier and an aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist) to increase the wear resistance of the first ring groove and is applied in highly loaded diesel engines. The most important thing is that the Ni-Resist (ferrous) must be bonded with a non-ferrous piston material during the casting of the piston. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that if the proper conditions are met, then the preparation of the ring carrier can be made successfully, as can the formation of the metal connection between the two materials of different qualities. 相似文献
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Dragan Aleksendrić Pierpaolo Carlone Velimir Ćirović 《Applied Composite Materials》2016,23(5):1047-1063
An intelligent optimization model aiming at off-line or pre-series optimization of the thermal curing cycle of polymer matrix composites is proposed and discussed. The computational procedure is based on the coupling of a finite element thermochemical process model, dynamic artificial neural networks and genetic algorithms. Objective of the optimization routine is the maximization of the composite degree of cure by the definition of the autoclave temperature. Obtained outcomes evidenced the capability of the method as well as its efficiency with respect to hard computing or experimental procedures. 相似文献
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