For a finite dimensional complex normed space , we say that it has the simultaneous zero inclusion property if an invertible linear operator S on has zero in its spatial numerical range if and only if zero is in the spatial numerical range of the inverse , as well. We show that beside Hilbert spaces there are some other normed spaces with this property. On the other hand, space does not have this property. Since not every normed space has the simultaneous zero inclusion property, we explore the class of invertible operators at which this property holds. In the end, we consider a property which is stronger than the simultaneous zero inclusion property and is related to the question when it is possible, for every invertible operator S, to control the distance of 0 to the spatial numerical range of by the distance of 0 to the spatial numerical range of S.
COBISS.SI-ID: 18028633
Reinforcement with geocells, represents a new and innovative way of reinforcing the pavement structure. Research project on the effectiveness of geocell reinforced pavement, which included theoretical work with analytical solutions, numerical analyses with parametric study and experimental analyses with laboratory experimental tests and test field experiment have been carried out. Mathematical model for analysis geocell reinforced pavement was derived. The models for FEM analyses includes un-reinforced pavement structure and geocells reinforced pavement, with different position and different strength and thickness of geocells. The output of model includes the expected life of the pavement. Testing apparatus, named Traffic Load Simulator was manufactured for testing the flexible pavement structure subjected to vertical and horizontal cyclic load and causes the rotation of principal stress axis. Experimental and theoretical analysis shows a significant improvement in pavement capacity and reduce of deformation, using geocells. With geocells, the bearing capacity of pavement structure is increased and permanent deformation of the pavement structure is reduced. The reinforcement method has been tested on the field, by carrying out field investigations on models geocell reinforcement pavement structure, compared with un-reinforcement pavement structure. First results show that geocells embedded in the unbound bearing layer provides flexibility and sufficient capacity of pavement structure. The investigation will take several years and will give significant results of time effect of geocell reinforced pavement.
COBISS.SI-ID: 2322535
A failure analysis of a belt conveyor at the place of impact was carried out. Different numbers of carrying idlers were tested to observe their effect at this critical site. A higher number of idlers reduces the size of deformation energy carried by the belt. With a higher number of idlers the transport belt is subject to less strain due to material landing. Longer life of transport belts is ensured.
COBISS.SI-ID: 1666911
The primary benefit of fuzzy systems theory is to approximate system behavior where analytic functions or numerical relations do not exist. In this paper, heuristic fuzzy rules were used with the intention of improving the performance of optimization models, introducing experiential rules acquired from experts and utilizing recommendations. The aim of this paper was to define soft constraints using an adaptive network-based fuzzy inference system (ANFIS). This newly-developed soft constraint was applied to discrete optimization for obtaining optimal solutions. Even though the computational model is based on advanced computational technologies including fuzzy logic, neural networks and discrete optimization, it can be used to solve real-world problems of great interest for design engineers. The proposed computational model was used to find the minimum weight solutions for simply-supported laterally-restrained beams.
COBISS.SI-ID: 20691222
In order to remain competitive to powder metallurgy and spray forming, further improvements of a classical production route are needed and desired. This paper describes the means by which the intrinsic hot deformability may be improved and the temperature range of the safe hot working extended for AISI M42 super high speed steel, one of the most challenging materials with respect to hot deformability. A special hot compression procedure is described to determine appropriate soaking temperatures of as-cast and semi-wrought states. Moreover, conventional hot compression tests in the extended temperature range (850–1150 °C) and strain rates range 0.001–5 s−1 were carried out. The complex behaviour of carbides is discussed, which depends on the soaking temperature and time, deformation temperature and strain rate. Deformation conditions for improved crushing of initial eutectic carbides networks during the first stages of hot working are identified. Apparent activation energies for hot working in two temperature ranges and constants of the hyperbolic sine function are determined. The microstructure and respective carbides are characterised by field emission scanning electron microscope, optical microscopy, X-ray diffraction and the results compared to equilibrium thermodynamic calculations using ThermoCalc.
COBISS.SI-ID: 1349982