Search results for "Mechanics of Material"

Contrasting probabilistic and anti-optimization approaches in an applied mechanics problem

2003

Probabilistic and non-probabilistic, anti-optimization analyses of uncertainty are contrasted in this study. Specifically, the comparison of these two competing approaches is conducted for an uniform column, with initial geometric imperfection, subjected to an impact axial load. The reliability of the column is derived for the cases when the initial imperfections posses either (a) uniform probability density, (b) truncated exponential density or (c) generic truncated probability density. The problem is also analyzed in the context of an interval analysis. It is shown that in, the most important near-unity reliability range these two approaches tend to each other. Since the interval analysis…

Itô calculus extended to systems driven by -stable Lévy white noises (a novel clip on the tails of Lévy motion)

2007

Abstract The paper deals with probabilistic characterization of the response of non-linear systems under α -stable Levy white noise input. It is shown that, by properly selecting a clip in the probability density function of the input, the moments of the increments of Levy motion process remain all of the same order ( d t ) , like the increments of the Compound Poisson process. It follows that the Ito calculus extended to Poissonian input, may also be used for α -stable Levy white noise input processes. It is also shown that, when the clip on the tails of the probability of the increments of the Levy motion approaches to infinity, the Einstein–Smoluchowsky equation is restored. Once these c…

Mößbauer- und ESCA-Untersuchungen zur Bildung oxidischer Eisenphasen in wäßrigen Medien unter der Einwirkung organischer Korrosionsinhibitoren

1982

Korrosionsschichten auf Stahl nach Exposition in Wasser mit bestimmter Harte und Chloridgehalt wurden hinsichtlich der Wirksamkeit beigefugter organischer Inhibitoren mittels Mosbauer- und ESCA-Spektroskopie untersucht. Es entstehen relativ dicke Schichten mit einem unerwartet niedrigen Eisengehalt in Form von FeOOH. Die Schichten enthalten merkliche Mengen von Ionen aus der Testlosung und auch Abbauprodukte der Inhibitormolekule. Letztere werden anscheinend in dem korrosiven Medium zersetzt. Es ist anzunehmen, das das Gesamtmolekul zwar den Transport des Inhibitors zum Metall beeinflust, die eigentliche Inhibierung aber allein durch funktionelle Gruppen erfolgt. Mossbauer and ESCA investig…

Mesoporous iron phosphate/phosphonate hybrid materials

2014

Abstract Relatively high surface area pure mesoporous iron-phosphorus oxide-based derivatives have been synthesized through an S + I − surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from iron atrane complexes and phosphoric and phosphonic acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from iron phosphate up to hybrids involving approximately 30% of organophosphorus entities (phosphonates or diphosphonates). X-ray powder diffraction, transmission elect…

Synthesis and Enhanced Capture Properties of a New BioMOF@SWCNT‐BP: Recovery of the Endangered Rare‐Earth Elements from Aqueous Systems

2021

Synthesis and Enhanced Capture Properties of a New BioMOF@SWCNT‐BP: Recovery of the Endangered Rare‐Earth Elements from Aqueous Systems (Adv. Mater. …

2021

Structural and Vibrational Study of a New Mixed Dipotassium Hydrogenselenate Dihydrogenphosphate K2(HSeO4)1.5 (H2PO4)0.5.

2006

Abstract Ongoing studies of the KHSeO4–KH2PO4 system, aimed at developing novel proton conducting solids, resulted in the new compound K2(HSeO4)1.5(H2PO4)0.5 (dipotassium hydrogenselenate dihydrogenphosphate). The crystals have been prepared by slow evaporation of an aqueous solution at room temperature. The structural properties of the crystals were characterized by X-ray single analysis (performed at room temperature), which revealed that K2(HSeO4)1.5(H2PO4)0.5 (KHSeP) crystallizes in space group P 1 ¯ with lattice parameters: a = 7.417(3) A, b = 7.668(2) A, c = 7.744(5) A, α = 71.59(3)°, β = 87.71(4)° and γ = 86.04(6)°. The compound has a unit cell volume 416.8(3) A3 and two formula unit…

Novel pathways for the preparation of mesoporous MCM-41 materials: control of porosity and morphology

1999

Two novel synthesis routes for the preparation of mesoporous MCM-41 materials are introduced. Both methods use tetra-n-alkoxysilanes such as tetraethoxysilane (TEOS) or tetra-n-propoxysilane (TPS) as a silica source which are added to an aqueous solution of a cationic surfactant in the presence of ammonia as catalyst. In this study, n-alkyltrimethylammonium bromides and n-alkylpyridinium chlorides were employed as templates. The addition of an alcohol (e.g. ethanol or isopropanol) leads to a homogeneous system which allows the formation of spherical MCM-41 particles. The main advantages of these methods are short reaction times, excellent reproducibility and easy preparation of large batche…

ON THE EFFECTS OF A CRACK PROPAGATING TOWARD THE INTERFACE OF A BIMATERIAL SYSTEM

2006

This paper deals with the influence of matrix cracks on the failure mode of bimaterial systems and composite materials. In order to investigate such an influence, the stress field near a crack embedded into the more yielding material and propagating perpendicularly to the interface, has been analyzed by using systematic numerical simulations. Such analysis has shown that the crack propagation give rises to transversal stresses that can damage the reinforcing materials when this has low modulus, as glass fibers, or low transversal strength, such as carbon fibers. Moreover, the longitudinal stress concentration can damage the reinforcing material only if this has high stiffness, as in the cas…

Bone diagenesis of archaeological human remains from Apulia (Italy) investigated by ATR-FTIR and XRF spectroscopy

2023

The analysis of the organic and mineral content of biological samples allows to define post-mortem alterations and the preservation status of ancient human remains. Here, we report a physical-chemical characterization of bone specimens from some skeletal remains found in Apulia (Italy) dating back to the prehistoric, classic-hellenistic, and medieval periods. Specific infrared band ratios from Attenuated Total Reflectance-Fourier Transform InfraRed and X-ray fluorescence spectroscopies were considered to evaluate the extent of the diagenetic process and the elemental composition of bone.Physical-chemical post-mortem transformations were related to the soil composition and specificity of tis…