In this paper, the preparation and characterisation of polymer materials suitable for single point incremental forming (SPIF) technology were performed. Three different kinds of mixtures were selected: a mixture of neat polyamide 12 (PA12), a nanocomposite with PA12 matrix and 1% clay (Cloisite 93A), and a nanocomposite with PA12 matrix and 3% clay (Cloisite 93A). Materials were produced using a melt intercalation method followed by compression moulding. According to the needs of SPIF technology, morphological and mechanical properties were investigated in the obtained mixtures. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize morphological properties. It was determined that the most desired obtained exfoliated structure of clay in the polymer matrix was achieved. Static tensile testing and dynamic mechanical analysis as well as the determination of glass transition temperature and crystallinity of all analysed materials were used to obtain mechanical and thermal properties of the mixtures. The results obtained for each mixture were compared with respect to the content of clay. The content of clay (Cloisite 93A) showed a strong influence on the properties of the obtained materials. The presence of clay (Cloisite 93A) affected the increase of tensile strength and Young's modulus, while its influence on the attained elongation was not unique.
COBISS.SI-ID: 16803611
The metallographic analysis of polycrystalline gadolinium cylinders revealed a microstructural anisotropy of some included phases in the extrusion and extrusion transversal directions. The amount of those phases in the material is not significant. However, the macroscopic anisotropy of mechanical properties needs to be verified. The strain distribution during compression loading was analyzed using finite element model (FEM) simulations. A FEM for the simulation of the elasto-plastic response of the Gd cylinders was performed. For this purpose, the experimentally obtained typical flow curve in the extrusion direction was used as the input data for the FEM model. Based on the dimensional similarity of the FEM model and the measured specimens, the potential appearance of macroscopic anisotropy is evaluated. Mechanical testing using compression cigar tests, as well as FEM, did not confirm any obvious effect of the elongated inclusions on the mechanical anisotropy of the gadolinium specimens.
COBISS.SI-ID: 1509034
Let ?(D) denote the domination number of a digraph D and let Cm?Cn denote the Cartesian product of Cm and Cn , the directed cycles of length n?m?3 . Liu et al. obtained the exact values of ?(Cm?Cn) for m up to 6 [Domination number of Cartesian products of directed cycles, Inform. Process. Lett. 111 (2010) 36–39]. Shao et al. determined the exact values of ?(Cm?Cn) for m=6,7 [On the domination number of Cartesian product of two directed cycles, Journal of Applied Mathematics, Volume 2013, Article ID 619695]. Mollard obtained the exact values of ?(Cm?Cn) for m=3k+2 [M. Mollard, On domination of Cartesian product of directed cycles: Results for certain equivalence classes of lengths, Discuss. Math. Graph Theory 33(2) (2013) 387–394.]. In this paper, we extend the current known results on Cm?Cn with m up to 21. Moreover, the exact values of ?(Cn?Cn) with n up to 31 are determined.
COBISS.SI-ID: 24462088
3D-printing technology is opening up new possibilities for the co-printing of sensory elements. While quasi-static research has shown promise, the dynamic performance has yet to be researched. This study researched smart 3D structures with embedded and printed sensory elements. The embedded strain sensor was based on the conductive PLA (Polylactic Acid) material. The research was focused on dynamic measurements of the strain and considered the theoretical background of the piezoresistivity of conductive PLA materials, the temperature effects, the nonlinearities, the dynamic range, the electromagnetic sensitivity and the frequency range. A quasi-static calibration used in the dynamic measurements was proposed. It was shown that the temperature effects were negligible, the sensory element was linear as long as the structure had a linear response, the dynamic range started at % 30 %% and broadband performance was in the range of few kHz (depending on the size of the printed sensor). The promising results support future applications of smart 3D-printed systems with embedded sensory elements being used for dynamic measurements in areas where currently piezo-crystal-based sensors are used.
COBISS.SI-ID: 16662555
Retail supply chains operate in a constantly changing environment and need to adapt to different situations in order to increase their reliability, flexibility and convenience. Holding and transportation costs can amount to up to 40 per cent of the product value, so that the proper coordination of interrelated activities plays an essential role when managing retail flows. In order to provide a relevant model we first focus on future demand satisfaction, whereas pricing policies, perishability factors, etc., are subjected to a complementary model for operative planning. The idea is to obtain a preferable distribution plan with minimal expected distribution costs, as well as minimal supply risks. The used methodology produces a set of solutions and quality estimates which can be used in order to find a desired distribution plan which is near-optimal. While considering stochasticity on the demand side, a multi-objective optimisation approach is introduced to cope with the minimisation of transport and warehouse costs, the minimisation of overstocking effects and the maximisation of customer's service level. The optimisation problem that arises is a computationally hard problem. A computational experiment has shown that the version of the problem where the weighted sum of costs is minimised can be handled sufficiently well by some well-known simple heuristics.
COBISS.SI-ID: 512976701