Comparative studies of localized buckling in sandwich struts with different core bending models

Analytical models with geometric non-linearities accounting for interactions between local and global instability modes leading to localized buckling in sandwich struts are formulated. For the core material response, two increasingly sophisticated bending models are compared against each other: Timoshenko beam theory (TBT) and Reddy-Bickford beam theory (RBT). Numerical solutions of the analytical models are validated with the commercial finite element code ABAQUS. It is found that there is a small but significant difference in the critical load between the two models and that the previously obtained solution slightly underestimates the linear buckling strength. More importantly, it is found that the RBT model predicts the onset of interactive buckling before the TBT model and, according to the results from the finite element study, matches the actual behaviour of a strut in both its initial and advanced post-buckling states with excellent correlation.     

Investigation of the presence of KCl in the structure and morphology of V-amylose–inclusion complexes

Amylose–fatty acid inclusion complexes were prepared using amylose extracted from pea starch and fatty acids with different chain length. To form the complexes, amylose, dissolved in aqueous alkaline solution (0.1 Ν ΚΟΗ), was mixed with fatty acid potassium soap solution and after neutralization the complex was obtained as precipitate. To investigate the structure and morphology of V-amylose–inclusion complexes, a series of techniques such as X-ray diffraction, SEM-microscopy combined with elemental microanalysis, Differential scanning calorimetry and Fourier transform infrared spectroscopy were employed. XRD analysis of complexes, revealed that the complexes displayed the typical V-form pattern, with an extra peak at 2θ?=?28.2°. To identify the origin of that peak the complexes were examined by SEM microscopy combined with elemental microanalysis. The results indicated that the peak was due to the presence of potassium chloride, formed during the preparation of the complexes. Washing the complexes with water was sufficient to remove the salt.     

Influence of the cocatalyst structure on the statistical copolymerization of methyl methacrylate with bulky methacrylates using the zirconocene complex Cp2ZrMe2

Statistical copolymers of methyl methacrylate with cyclohexyl and trimethylsilyloxy ethyl methacrylate were synthesized with two different catalytic systems based on the zirconocene complex Cp₂ZrMe₂. The reactivity ratios of methyl methacrylate and these methacrylates were calculated with the Finemann–Ross, inverted Finemann–Ross, and Kelen–Tüdos graphical methods. The structural parameters of these copolymers were estimated from the calculation of the dyad monomer sequence fractions. Two different borate cocatalysts were employed, and their effect on the copolymerization process is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3305–3314, 2005     

Lévy-statistics for partially equilibrated systems

We examine deviations from Boltzmann-Gibbs statistics for a certain class of partially equilibrated systems of finite size. We find that such systems are characterized by the Lévy distribution whose non-extensivity parameter is related to the number of internally equilibrated subsystems and to correlations among them. This concept is applicable to relativistic heavy ion collisions.     

Discussion: “On interactive buckling in a sandwich structure” by C. D. Coman

A recent article by Coman (Z Angew Math Phys 2009) on the response of compression sandwich struts made some claims on the quality of the simplified version of the interactive buckling model presented in Hunt and Wadee (Proc R Soc A 454(1972):1197–1216, 1998). Some of these claims are examined in detail herein; it is concluded that great care must be exercised when performing parametric studies with equations that have been derived from simplifying a mechanical model. This is because the resulting system of equations does not necessarily describe the original mechanical system in full, since the key assumptions necessarily change.     

New proofs of Plünnecke-type estimates for product sets in groups

We present a new method to bound the cardinality of product sets in groups and give three applications. A new and unexpectedly short proof of the Plünnecke-Ruzsa sumset inequalities for commutative groups. A new proof of a theorem of Tao on triple products, which generalises these inequalities when no assumption on commutativity is made. A further generalisation of the Plünnecke-Ruzsa inequalities in general groups.     

Interaction between magnetic agglomerates and an extended free radicals network studied by magnetic resonance

Solids containing an extended network of free radicals have been prepared and studied by magnetic resonance techniques in the 4–290 K temperature range. One solid contained additionally a small amount of magnetic γ-Fe₂O₃ in the form of nanoparticle agglomerates. The solid without agglomerates displayed only a narrow, single resonance line centered at g _eff = 2.0043. The magnetic resonance measurements of the solid with γ-Fe₂O₃ agglomerates gave a spectrum composed of two lines attributed to two different magnetic centers: a narrow line due to free radicals and a broad line arising from magnetic iron oxide agglomerates. In the high temperature range the integrated intensities of both lines decreased with decreasing temperature. The resonance field of the broad line shifted to lower magnetic fields upon lowering the temperature with the gradient ΔH _r /ΔT = 2.3 G/K, while the narrow line shifted towards higher magnetic fields. The linewidth of the broader line increased with decreasing temperature while for the narrow lines in both samples this change was small. The magnetic iron oxide clusters produce a magnetic field which acts on the free radicals network and its strength depends essentially on the concentration of clusters. The reorientation process in the free radicals network is more intense in the sample without magnetic clusters.     

The synthesis of n‐substituted isothiazol‐3(2h)‐ones from nsubstituted 3‐benzoylpropionamides

N‐Substituted isothiazol‐3(2H)‐ones can be easily prepared from N‐substituted 3‐benzoylpropi‐onamides in two experimentally simple steps, in satisfactory overall yields. Reaction of the amides with excess thionyl chloride results in the formation of N‐substituted 5‐benzoylisothiazol‐3(2H)‐ones, which are readily debenzoylated with alkali to the corresponding N‐substituted isothiazol‐3(2H)‐ones. This method has now been successfully applied to the synthesis of isothiazolones N‐substituted with a bulky alkyl group, such as the tert‐butyl group, and with a phenyl group bearing either a strong electron‐withdrawing substituent, such as the 3‐nitrophenyl and 4‐nitrophenyl group, or an electron‐releasing substituent, such as the 4‐methylphenyl and 4‐methoxyphenyl group.