Rainflow analysis in Coastal Engineering using switching second order Markov models

The paper deals with the use of Markov and switching Markov chain models of turning points to reproduce random sets of sea states. The advantages of these models are emphasized and compared with existing models based on wave height records, indicating that long and short range and period cycles are included, while the wave height records ignore this important information from the point of view of damage accumulation. Existing models for first order Markov processes are extended to the case of second order processes and closed formulas are given to derive the rainflow matrices of these processes. Finally, one illustrative example of application is given.     

A new approach to relative asymptotic behavior for discrete Sobolev-type orthogonal polynomials on the unit circle

In Foulquié et al. (1999) [2], Li and Marcellán (1996) [4], Marcellán and Moral (2002) [5], the relative asymptotic behavior of orthogonal polynomials with respect to a discrete Sobolev-type inner product on the unit circle was studied. In this paper, we propose an alternative approach to this problem based on the Uvarov spectral transformation.     

Globally optimized packings of non-uniform size spheres in $$\mathbb {R}^{d}$$: a computational study

In this work we discuss the following general packing problem: given a finite collection of d-dimensional spheres with (in principle) arbitrarily chosen radii, find the smallest sphere in \(\mathbb {R}^{d}\) that contains the given d-spheres in a non-overlapping arrangement. Analytical (closed-form) solutions cannot be expected for this very general problem-type: therefore we propose a suitable combination of constrained nonlinear optimization methodology with specifically designed heuristic search strategies, in order to find high-quality numerical solutions in an efficient manner. We present optimized sphere configurations with up to \(n = 50\) spheres in dimensions \(d = 2, 3, 4, 5\). Our numerical results are on average within 1% of the entire set of best known results for a well-studied model-instance in \(\mathbb {R}^{2}\), with new (conjectured) packings for previously unexplored generalizations of the same model-class in \(\mathbb {R}^{d}\) with \(d= 3, 4, 5.\) Our results also enable the estimation of the optimized container sphere radii and of the packing fraction as functions of the model instance parameters n and 1 / n, respectively. These findings provide a general framework to define challenging packing problem-classes with conjectured numerical solution estimates.     

A series of new high‐performance materials based on poly[4′‐fluorophenyl‐bis(4‐phenyl)phosphine oxide]

A new series of high‐performance poly(arylene phosphine oxide) (PAPO) materials were synthesized postpolymerization from fluorinated poly(arylene phosphine oxide) (f‐PAPO). The new materials had increased solubility and film‐forming ability over the parent f‐PAPO. With the careful choice of the nucleophile, the thermal stability was also increased. The parent polymer f‐PAPO was synthesized via Ni(0) coupling from aromatic chloride and mesylate monomers. Both monomers were polymerized successfully to create polymers with intrinsic viscosities of 0.235 and 0.123 dL/g, respectively. The higher molecular weight f‐PAPO gave a glass transition of 320 °C and a char yield of 54% at 650 °C in air. The substitution of f‐PAPO via nucleophilic aromatic substitution produced PAPO thermoplastics with significant changes in the properties. The largest increase in the thermal stability relative to f‐PAPO was from 563 to 600 °C 10% weight‐loss values in nitrogen after the displacement of fluoride by 4‐aminophenol, which yielded poly[4‐(4‐aminopheonxyphenyl)bis(4′‐phenyl)phosphine oxide]. Additionally, the char yield increased from 54 to 71% in air at 650 °C. The solubility of the parent polymer was improved after substitution with 3‐tert‐butylphenol, n‐nonylamine, and poly(ethylene glycol)monomethyl ether. All of these became soluble in chloroform, N,N‐dimethylacetamide, and dimethyl sulfoxide. Copolymers were synthesized with 2,5‐dichloro‐4′‐fluorobenzophenone to improve the solubility of f‐PAPO without the loss of thermal stability. These copolymers also underwent nucleophilic aromatic substitution to create an epoxy cure agent that was used with the DEN 431 resin. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2277–2287, 2003     

Chemistry of dithiocarbamate derivatives of amino acids. Part III. X-ray photoelectron spectroscopy of Ba(S2CNHCH2CO2)·3H2O. I.r. and e.s.r. studies of α-amino acid-dithiocarbamate complexes of copper(II)

Summary Coordination compounds [Cu(S₂CNHCHRCO₂H)₂], were obtained by reaction of dithiocarbamate derivatives of amino acids with copper(II), and the products were characterized by i.r. and e.s.r. spectroscopy. The xps spectrum of Ba(S₂CNHCH₂CO₂)·3H₂O is reported.     

A two-phase method to produce gel beads

A method for producing entrapped whole cell biocatalyst is described. The procedure consists of the direct mixing of a gel suspension with an oily phase. Three biopolymers are used: gelatin, agar, and carrageenan using K. fragilis cells containing β-galactosidase activity as a design model. For a given gel type and concentration, the bead’s particle size is a direct function of the agitation rate and the type of impeller, as well as the geometry of the system. Therefore, the particle size distribution is obtained as a function of the impeller’s Reynolds number in order to define a scale-up criteria. The β-galactosidase biocatalyst is characterized considering the effect of particle size and substrate concentration on the effectiveness factor. This method does not require the usual extrusion equipment and, as shown here, is adequate for scaling up.

     

Low-pressure DC air plasmas. investigation of neutral and ion chemistry

The neutral and charged species present in a direct current (dc) hollow cathode, gas flow, air reactor are experimentally studied by quadrupole mass spectrometry. The degree of ionization of the plasma and the electron mean temperature with decreasing air pressure, for constant discharge current, are measured with a double Langmuir probe. The chemical composition of the plasma changes appreciably over the 3 x 10(-3) to 5 x 10(-2) mbar range investigated: at the lowest pressures studied, O2 dissociation is up to 60% and the concentration of NO is half that of N2; concerning ions, NO+ and N2+ are dominant for the whole pressure range. A kinetic model of the plasma including electrons, neutrals, and positive ions is developed to account for the experimental observations; it is consistent with energy balance and predicts that heterogeneous processes are the main source of NO and that the contribution of ions to the global chemistry of neutrals is of minor significance even for the lowest pressures.     

Three approaches to the development of selective bilayer amperometric biosensors for glucose by in situ electropolymerization

Three different glucose oxidase biosensors for the enzymatic determination of glucose, based on bilayer polymer coatings consisting of polypyrrole (PPy) and poly(o-phenylenediamine), were developed. The electrode substrates are Pt metal, carbon paste and an organic conducting salt (tetrathiafulvalene-tetracyanoquinodimethane), which introduces appreciable variability in the electrode construction process. The three sensors were compared with one another and with bare and PPy monolayer-coated sensors in terms of performance in the determination of glucose in a synthetic serum sample. These configurations provide improved selectivity against the interferences of electroactive species such as ascorbic acid and uric acid, frequently present in biological samples, and the differences between them can be taken advantage of in application to different kinds of samples.     

Synthesis and fasciolicidal activity of 5-chloro-2-methylthio-6-(1-naphthyloxy)-1H-benzimidazole

The synthesis and fasciolicidal activity of 5-chloro-2-methylthio-6-(1-naphthyloxy)-1H-benzimidazole (6) is described. Compound 6 showed 100% activity in vitro at 146.70 and 29.34 microM concentrations. It also completely removed 3-d and 10-week-old Fasciola hepatica in sheep at a dose of 15 mg/kg.