22 research outputs found
Vortex motion behind a circular cylinder
Vortex motion behind a circular cylinder moving through water is discussed. It is shown that a pair of vortices form behind a moving cylinder and that their centers will move along a predictable curve. This curve represents an equilibrium condition which, however, is subject to perturbation. The stability of the vortex pair is investigated. Movement of the vortex pair away from the cylinder is calculated as an explanation of the resistance of the cylinder. Finally, the principles elaborated are applied to the flow around a flat plate
Development of innovative hybrid sandwich panel slabs: Experimental results
The authors appreciate the collaboration of the following labs: Civitest for developing DHCC materials, PIEP for conducting VARTM process (Eng. Luis Oliveira) and Department of Civil Engineering of Minho University to perform the tests (Mr. Antonio Matos and Eng. Marco Jorge).In this paper, a new generation of composite sandwich slab is proposed as a solution for the rehabilitation
of slabs in old masonry buildings. An innovative solution was developed during this research formed by
four components: a Deflection Hardening Cement Composite (DHCC) layer on the top compression skin, a
glass fiber reinforced polymer (GFRP) skin at the bottom tension surface, GFRP ribs to transfer shear from
top to bottom layers, and foam core for thermal-insolation purposes. The DHCC layer contributes significantly
for the load carrying and deflection capacity due to its stiffness, compressive strength and toughness,
offers resistance to the occurrence of buckling phenomena in the GFRP ribs, improves the
performance of this structural concept against impact and fire, and constitutes an excellent medium
for the application of finishing materials, like ceramics or timber. Two different hybrid composite slabs
were developed and tested, and their behavior was assessed under flexural loading. The results showed
that the developed hybrid sandwich slabs accomplish all design requisites for serviceability and ultimate
limit states, and assure a stiffness/dead-weight and load-capacity/dead-weight ratios much higher than
conventional structural slab systems.FCT - Fundação para a Ciência e Tecnologi
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Structural complexity in indium selenides prepared using bicyclic amines as structure-directing agents
The synthesis and characterization of five new indium selenides, [C9H17N2]3[In5Se8+x(Se2)1−x] (1–2), [C6H12N2]4[C6H14N2]3[In10Se15(Se2)3] (3), [C6H14N2][(C6H12N2)2NaIn5Se9] (4) and [enH2][NH4][In7Se12] (5), are described. These materials were prepared under solvothermal conditions, using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,4-diazabicyclo[2.2.2]octane (DABCO) as structure-directing agents. Compounds 1–4 represent the first examples of ribbons in indium selenides, and 4 is the first example of incorporation of an alkali metal complex. Compounds 1, 2 and 4 contain closely related [In5Se8+x(Se2)1−x]3− ribbons which differ only in their content of (Se2)2− anions. These ribbons are interspaced by organic countercations in 1 and 2, while in 4 they are linked by highly unusual [Na(DABCO)2]+ units into a three-dimensional framework. Compound 3 contains complex ribbons, with a long repeating sequence of ca. 36 Å, and 4 is a non-centrosymmetric three-dimensional framework, formed as a consequence of the decomposition of DABCO into ethylenediamine (en) and ammonia