Temperature dependence of stress–fatigue life data of FRP composites

Polymer-matrix composites are viscoelastic materials, and their mechanical properties are significantly influenced by temperature. The present study develops a power-law stress–fatigue life relation which takes into account the effect of temperature on the fatigue strength of fibre-reinforced polymer (FRP) composites. The validity of the relation is evaluated on the basis of various sets of experimental data found in the literature, and the estimated fatigue lives obtained are found to be in good agreement with the experiments.     

Finite element simulation of the poling process in BaTiO3–CoFe2O4 multiferroic composites

The theoretical background of nonlinear constitutive magneto-ferroelectric behavior as well as the Finite Element implementation are presented. On this basis the polarization in the ferroelectric matrix (BaTiO₃) with embedded dielectric-magnetostrictive particels (CoFe2O₄) is simulated and the resulting effects are analyzed. Numerical simulations focus on the prediction of local crystal orientations and residual stress going along with the poling process, in the future supplying information on favorable electric-magnetic loading sequences. Further, multifield homogenization procedures enable the prediction of the electromagnetomechanical properties of smart multiferroic composites and supply useful means for their optimization. The resulting final state of a poling simulation can be implemented as a starting condition for approximate linear simulations. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of the crop mix of a rubber and oil palm plantation—A programming approach

This paper sets out a multi-period multi-objective linear programming model developed to capture as accurate as possible, the complex relationship between factors of production and the constraints operating on these factors of production for a perennial crop plantation. The primary objective is to provide a tool to determine the optimal crop mix under conditions of price uncertainty. Information necessary for the firm's capital budgeting can be simultaneously derived. Uncertainty is accomodated in a linear risk constraint in the model and the level of uncertainty is parametrised to obtain the efficiency frontier.To illustrate the methodology developed, the paper analyses investment alternatives in a Malaysian plantation. Sensitivity analyses were performed on the usage of factors of production as well as rate of export duty the firm has to pay. Such analyses are useful for intertemporal production planning under conditions of uncertainty.     

Track–Monitoring of Wheel–Rail–Systems

Inspection and maintenance of railway networks is a complex and expensive task. Special measurement vehicles are used to record the geometrical properties of railway lines within required time intervals. Due to the extent of measurement data the quality of railway track is evaluated considering only a few parameters. Although safety and comfort of wheel–rail–systems depend on the dynamical behavior, current inspection vehicles are not equipped to measure dynamic properties. In this paper, we will discuss a novel approach to evaluate the quality of railway tracks based on wheel–rail dynamics: Wheelset dynamics of subway trains are analyzed by Karhunen–Loève Transformation to extract the principal dynamics from the collected measurement data. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cases of equality in certain multilinear inequalities of Hardy–Riesz–Rogers–Brascamp–Lieb–Luttinger type

Cases of equality in certain Hardy–Riesz–Rogers–Brascamp–Lieb–Luttinger rearrangement inequalities are characterized.     

Realisations of Kummer–Chern–Eisenstein-motives

Inspired by work of G. Harder we construct via the motive of a Hilbert modular surface an extension of a Tate motive by a Dirichlet motive. We compute the realisation classes and indicate how this is linked to the Hodge-1-motive of the given Hilbert modular surface.     

Cardinality of the Set of Delta–Closed Classes of Functions of Multi–Valued Logic

A closure under composition operation and weak version of inversion operation is considered on the set of functions of k–valued logic. The cardinality of the set of all such closed classes is calculated.     

Construction of Runge–Kutta methods of Crouch–Grossman type of high order

An approach is described to the numerical solution of order conditions for Runge–Kutta methods whose solutions evolve on a given manifold. This approach is based on least squares minimization using the Levenberg–Marquardt algorithm. Methods of order four and five are constructed and numerical experiments are presented which confirm that the derived methods have the expected order of accuracy.     

Physicomechanical properties of composites containing “thermocell” microcrystalline cellulose as filler

We have developed a thermocatalytic method for obtaining Thermocell microcrystalline cellulose. Our method is simpler than the conventional acid hydrolysis method and allows us to use less concentrated acids at lower temperatures. The microcrystalline cellulose Thermocell has homogeneous granulation and consists of spherical particles, 90% of which have a diameter of 20–50 mm. Depending on the area of application and the required chemical purity, Thermocell can be obtained from bleached or unbleached wood pulp and also wastes of the paper and pulp industry, such as newsprint waste.Institute of Wood Chemistry, Latvian Academy of Sciences, Riga, Latvia LV-1006. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 4, pp. 549–557, 1996.     

A generalization of the category O of Bernstein–Gelfand–Gelfand

In the study of simple modules over a simple complex Lie algebra, Bernstein, Gelfand and Gelfand introduced a category of modules which provides a natural setting for highest weight modules. In this note, we define a family of categories which generalizes the BGG category. We classify the simple modules for some of these categories. As a consequence we show that these categories are semisimple.     

Orderings of Witzel–Zaremsky–Thompson groups

We prove the orderability of the Witzel-Zaremsky-Thompson group for a direct system of orderable groups under a certain compatibility assumption.     

Approximation Properties of Bivariate Extension of q-Bernstein–Schurer–Kantorovich operators

Results in Mathematics - In this paper, we introduce a bivariate generalization of the Bernstein–Schurer–Kantorovich operators based on q-integers and get a Bohmann–Korovkin type...     

Identifiability issues of age–period and age–period–cohort models of the Lee–Carter type

The predominant way of modelling mortality rates is the Lee–Carter model and its many extensions. The Lee–Carter model and its many extensions use a latent process to forecast. These models are estimated using a two-step procedure that causes an inconsistent view on the latent variable. This paper considers identifiability issues of these models from a perspective that acknowledges the latent variable as a stochastic process from the beginning. We call this perspective the plug-in age–period or plug-in age–period–cohort model. Defining a parameter vector that includes the underlying parameters of this process rather than its realizations, we investigate whether the expected values and covariances of the plug-in Lee–Carter models are identifiable. It will be seen, for example, that even if in both steps of the estimation procedure we have identifiability in a certain sense it does not necessarily carry over to the plug-in models.     

A Criterion of Convergence of Lagrange–Sturm–Liouville Processes in Terms of One-Sided Module of Variation

We obtain a criterion of uniform convergence inside the interval (0, π) of interpolation processes determined by eigenfunctions of the regular Sturm–Liouville problem with a continuous potential of bounded variation. The criterion is formulated in terms of one-sided modulus of variation.