The paper is motivated by the previous research concerning the heat transfer in a heat accumulation device. The device had been explored, built up and tested with the aim of utilization of cheap solar energy and its storage. In this heat storage system, a vacuum-like gap between two concentric containers acts as an insulating layer, radiation being the predominant heat transfer type in the gap. The better knowledge and understanding of the heat exchange by radiation, the more effectiveness of the insulation of the layer can be reached. Heat transfer by radiation is explored in the paper, mathematical model is set up, the algorithm of non-linear transient computation is introduced, and some illustrative results of this computation are performed.
The paper deals with rheological models and creep and relaxation tests on matters which are represented by models. Three models based on two fundamental components (Hooke’s elastic and Newton’s viscous compounds) are performed. The models originated from several fundamental matters by their parallel or serial connections. The corresponding constitutive equations are derived. The behavior of the models under the creep and relaxation tests is observed and is expressed by corresponding stress - strain formulas and illustrated in the figures.
Phenomenological models of continuum mechanics applied on the rigid body are more or less idealized. Experimental measuring showed there is a plastic flow, respectively relaxation in real rigid bodies, i.e. stress is the function of strain, strain velocity and the higher time derivatives. The paper deals with the rheological models based on the Hook elastic and Newton viscous masses. The corresponding constitutive equations are described.
The paper deals with mathematical modeling of the structural materials representing their rheological properties. The materials are modeled by more complex models (enhancement of Voigt and Maxwell models). The constitutive equations are derived; the relationships within the creep and relaxation process are developed. The rheological behavior of the materials is introduced.
The tasks involving repeated integral occur from time to time in technical practice. This paper introduces the research of authors in the field of repeated integrals within the required class of functions. Authors focus on the definite integral over repeated integral and they develop a tool for its computation. It involves two principal steps, analytical and numerical step.
In the analytical step, the definite integral over a repeated integral is decomposed into n integrals and then the Cauchy form is used for further rearrangement. Numerical step involves Gauss type integration slightly modified by the authors. Several examples illustrating the operation of both analytical and numerical steps of the method are provided in the paper.
The paper deals with the biomechanical investigation on the motion segment - basic part of the human lumbar spine focused on the intervertebral disc response to the various types of load. It contains the description and the reason of the simplification of the model, the biomechanical laws; the mathematical treatment with the computational implementation added. The results are presented and discussed especially for the intervertebral disc.