Long-Term Behavior of PBO FRCM and Comparison with Other Inorganic-Matrix Composites

Fabric-reinforced cementitious matrix (FRCM) composites, comprising high-strength fiber textiles embedded within inorganic matrices, represent an effective, cost-efficient, and low-invasive solution for strengthening and retrofitting existing masonry and reinforced concrete structures. Among different textiles employed in FRCM composites, polyparaphenylene benzo-bisoxazole (PBO) textiles are adopted due to their high tensile strength and good adhesion with the matrix. Although several experimental, numerical, and analytical works were performed to investigate the mechanical properties of PBO FRCM composites, limited information is available on their long-term behavior, as well as in the case of exposure to aggressive environments. This paper presents and discusses the results of a wide experimental campaign aimed at investigating the effect of different environmental conditions on the long-term tensile behavior of a PBO FRCM composite. Tests are performed using a clamping-grip tensile test set-up. The effect of various aggressive environments on the composite matrix cracking stress, composite tensile strength, ultimate strain, and fully cracked stage slope is investigated by comparing the results of nominally equal conditioned and unconditioned (control) specimens. These results are also compared with those of other FRCM composites comprising glass and carbon textiles subjected to the same conditionings, collected from the literature. The results show only limited reductions in the tensile properties, even after long exposure to aggressive environments

War and dissociation : the case of futurist aesthetics

Thanks to their deliberate engagement in state propaganda Italian Futurists deserved a prominent spot in the history of military aesthetics in the 20th century. However, under what looked like an unequivocal expression of support for war, lied a deep philosophical disagreement concerning its existential and epistemological value. The bone of contention concerned the effects of warfare on perception and, consequently, the means of its depiction. The author analyses this intellectual disagreement within the group and focuses, in particular, on its philosophical implications

The impact of columnar file formats on SQL‐on‐hadoop engine performance: A study on ORC and Parquet

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Bending and shear behavior of historic walls strengthened with composite reinforced mortar

Composite reinforced mortar (CRM) is a relatively new solution for the strengthening of existing masonry members that comprises fiber-reinforced polymer (FRP) grids reinforcing inorganic mortar overlays. CRMs were proven to be effective in strengthening masonry members against in- and out-of- plane loads. In this paper, a glass FRP-CRM is employed to strengthen 5-leaf historic masonry walls cut from an existing building located in Milan, Italy. The walls were strengthened and then subjected to three-point bending and diagonal compression tests. Results were compared with those of corresponding non-strengthened walls and showed the CRM effectiveness also in the case of thick masonry members

Updating DL-Lite ontologies through first-order queries

In this paper we study instance-level update in DL-LiteA, the description logic underlying the OWL 2 QL standard. In particular we focus on formula-based approaches to ABox insertion and deletion. We show that DL-LiteA, which is well-known for enjoying first-order rewritability of query answering, enjoys a first-order rewritability property also for updates. That is, every update can be reformulated into a set of insertion and deletion instructions computable through a nonrecursive datalog program. Such a program is readily translatable into a first-order query over the ABox considered as a database, and hence into SQL. By exploiting this result, we implement an update component for DLLiteA-based systems and perform some experiments showing that the approach works in practice.Peer ReviewedPostprint (author's final draft

Effect of cyclic load on the tensile behavior of a PBO FRCM composite

The use of externally bonded fiber-reinforced cementitious matrix (FRCM) composites represents a valid alternative to traditional techniques for the strengthening and retrofitting of existing reinforced concrete and masonry structures. FRCM composites are comprised of high strength textiles embedded within inorganic matrices and can be directly applied to the external surface of the existing structural element to increase its displacement and load capacity (i.e., axial, flexural, and shear strength). Thus, FRCM have a low invasiveness and a high strength-to-weight ratio. Recently, investigations on the bond behavior of FRCM composites showed that the presence of friction between the textile and matrix can induce damage to the fiber, which in turn determines possible reductions in the strengthened element capacity. This effect appears particularly critical in the case of cyclic and dynamic loads. In this paper, the cyclic behavior of a PBO FRCM composite is experimentally investigated using low-cycle tensile tests on composite specimens. Namely, FRCM rectangular coupons are subjected to clamping- and clevis-grip tensile tests. These tests provide important information on the effect of low-frequency dynamic loading on the composite tensile properties under different test configurations

Pattern formation and localization in the forced-damped FPU lattice

We study spatial pattern formation and energy localization in the dynamics of an anharmonic chain with quadratic and quartic intersite potential subject to an optical, sinusoidally oscillating field and a weak damping. The zone-boundary mode is stable and locked to the driving field below a critical forcing that we determine analytically using an approximate model which describes mode interactions. Above such a forcing, a standing modulated wave forms for driving frequencies below the band-edge, while a ``multibreather'' state develops at higher frequencies. Of the former, we give an explicit approximate analytical expression which compares well with numerical data. At higher forcing space-time chaotic patterns are observed.Comment: submitted to Phys.Rev.

Peeling of Long, Straight Carbon Nanotubes from Surfaces

The adhesion of long, straight, single-walled carbon nanotubes to surfaces is examined usingmultidimensional force spectroscopy. We observed characteristic signatures in the deflection and frequency response of the cantilever indicative of nanotube buckling and slip-stickmotion as a result of compression and subsequent adhesion and peeling of the nanotube fromthe surface.The spring constant and the elastic modulus of the SWNT were estimated from the frequency shifts under tension. Using elastica modeling for postbuckled columns, we have determined the static coefficient of friction for the SWNT on alkanethiol-modified gold surfaces and showed that it varies with the identity of the monolayer terminal group.Fil: Barker, Kane M.. Georgia Institute of Technology. School of Chemistry and Biochemistry; Estados UnidosFil: Poggi, Mark A.. Georgia Institute of Technology. School of Chemistry and Biochemistry; Estados UnidosFil: Lizarraga, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Georgia Institute of Technology. School of Chemistry and Biochemistry; Estados UnidosFil: Lillehei, Peter T.. NASA Langley Research Center. Advanced Materials and Processing Branch; Estados UnidosFil: Ferri, Aldo. Georgia Institute of Technology. George W. Woodruff School of Mechanical Engineering; Estados UnidosFil: Bottomley, Lawrence A.. Georgia Institute of Technology. School of Chemistry and Biochemistry; Estados Unido

Expression of a Barhl1a reporter in subsets of retinal ganglion cells and commissural neurons of the developing zebrafish brain

Promoting the regeneration or survival of retinal ganglion cells (RGCs) is one focus of regenerative medicine. Homeobox Barhl transcription factors might be instrumental in these processes. In mammals, only barhl2 is expressed in the retina and is required for both subtype identity acquisition of amacrine cells and for the survival of RGCs downstream of Atoh7, a transcription factor necessary for RGC genesis. The underlying mechanisms of this dual role of Barhl2 in mammals have remained elusive. Whole genome duplication in the teleost lineage generated the barhl1a and barhl2 paralogues. In the Zebrafish retina, Barhl2 functions as a determinant of subsets of amacrine cells lineally related to RGCs independently of Atoh7. In contrast, barhl1a expression depends on Atoh7 but its expression dynamics and function have not been studied. Here we describe for the first time a Barhl1a reporter line in vivo showing that barhl1a turns on exclusively in subsets of RGCs and their post-mitotic precursors. We also show transient expression of barhl1a:GFP in diencephalic neurons extending their axonal projections as part of the post-optic commissure, at the time of optic chiasm formation. This work sets the ground for future studies on RGC subtype identity, axonal projections and genetic specification of Barhl1a-positive RGCs and commissural neurons

On the succinctness of query rewriting over shallow ontologies

We investigate the succinctness problem for conjunctive query rewritings over OWL2QL ontologies of depth 1 and 2 by means of hypergraph programs computing Boolean functions. Both positive and negative results are obtained. We show that, over ontologies of depth 1, conjunctive queries have polynomial-size nonrecursive datalog rewritings; tree-shaped queries have polynomial positive existential rewritings; however, in the worst case, positive existential rewritings can be superpolynomial. Over ontologies of depth 2, positive existential and nonrecursive datalog rewritings of conjunctive queries can suffer an exponential blowup, while first-order rewritings can be superpolynomial unless NP �is included in P/poly. We also analyse rewritings of tree-shaped queries over arbitrary ontologies and note that query entailment for such queries is fixed-parameter tractable