FRP-Confined Concrete Model

A uniaxial model for concrete confined with fiber-reinforced polymers (FRP), but also with steel jackets or conventional transverse reinforcement, is presented. The model, which is suitable to be inserted into fiber-type beam-column models, explicitly accounts for the continuous interaction with the confining device due to the lateral strain of concrete, through an incremental-iterative approach. The relation between the axial and lateral strains is implicitly derived through equilibrium between the (dilating) confined concrete and the confining device. This relation allows one to trace the state of strain in the jacket and to detect its failure. The model is compared with a set of experimental tests and shows very good agreement in both the stress-strain and the stress-lateral strain response. Evidence of the main aspects of the behavior of FRP-confined concrete is given that points out differences in the response when using fiberglass or carbonfiber. Predictive equations to determine the ultimate strength and strain of concrete confined with FRP are derived and tested on a number of experimental data.     

Abstract Interpretation based Verification of Logic Programs

This paper is an overview of our results on the application of abstract interpretation concepts to various problems related to the verification of logic programs. These include the systematic design of semantics modeling various proof methods and the characterization of assertions as abstract domains.     

On the compressive elasticity of epoxy resins filled with hollow glass microspheres

The mechanical properties of a hollow glass microsphere-filled epoxy resin composite system were investigated in air as a function of the weight content of particles ranging from 0 to 15.38% (wt/wt). The analysis based on necessarily modified classical models together with structural observations enabled explanation of the composition dependencies of elastic moduli of the blends studied. It was found that, together with a presumption of no interfacial adhesion between the filler and matrix, an interlayer of immobilized matrix with changed mechanical properties compared to the formal matrix seems to strongly affect the mechanical behavior of the composite. © 1996 John Wiley & Sons, Inc.     

Structural Characterization of Nitrosomonas europaea Cytochrome c‐552 Variants with Marked Differences in Electronic Structure

Nitrosomonas europaea cytochrome c‐552 (Ne c‐552) variants with the same His/Met axial ligand set but with different EPR spectra have been characterized structurally, to aid understanding of how molecular structure determines heme electronic structure. Visible light absorption, Raman, and resonance Raman spectroscopy of the protein crystals was performed along with structure determination. The structures solved are those of Ne c‐552, which displays a “HALS” (or highly anisotropic low‐spin) EPR spectrum, and of the deletion mutant Ne N64Δ, which has a rhombic EPR spectrum. Two X‐ray crystal structures of wild‐type Ne c‐552 are reported; one is of the protein isolated from N. europaea cells (Ne c‐552n, 2.35 Å resolution), and the other is of recombinant protein expressed in Escherichia coli (Ne c‐552r, 1.63 Å resolution). Ne N64Δ crystallized in two different space groups, and two structures are reported [monoclinic (2.1 Å resolution) and hexagonal (2.3 Å resolution)]. Comparison of the structures of the wild‐type and mutant proteins reveals that heme ruffling is increased in the mutant; increased ruffling is predicted to yield a more rhombic EPR spectrum. The 2.35 Å Ne c‐552n structure shows 18 molecules in the asymmetric unit; analysis of the structure is consistent with population of more than one axial Met configuration, as seen previously by NMR. Finally, the mutation was shown to yield a more hydrophobic heme pocket and to expel water molecules from near the axial Met. These structures reveal that heme pocket residue 64 plays multiple roles in regulating the axial ligand orientation and the interaction of water with the heme. These results support the hypothesis that more ruffled hemes lead to more rhombic EPR signals in cytochromes c with His/Met axial ligation.     

Efficient feature selection using shrinkage estimators

Machine Learning - Information theoretic feature selection methods quantify the importance of each feature by estimating mutual information terms to capture: the relevancy, the redundancy and the...     

Improving die casting processes through optimization of lubrication

Lubrication plays a significant role among the processes that affect aesthetic quality in die casting. Nevertheless, comprehensive investigations are still missing in literature. In this paper, the effect of lubrication is investigated and optimized, by focusing on its influence on the die temperature. Indeed, since the surface quality of castings is related to the interaction between melt and die, lubrication allows ejection of castings without generating defects and cooling of the die, by preserving its surface. Hence, the die temperature should be accurately selected and spraying should be improved to achieve the optimal temperature. In the experimentation proposed, the lubricant release agent percentage and the lubrication duration have been varied to trade-off between some conflicting effects, while making the die temperature approach the ‘Nukiyama point’. At the same time, reduction of the cycle time has been obtained. The results corroborate the approach, since defects are reduced after optimization.