A commercial woodcutting circular sawblade was analysed in this work. The lateral stiffness on the periphery was measured, and the natural frequencies were determined by modal analyses. The sawblade was modelled by the finite element method, where the influence of the internal stresses caused by roll-tensioning of the sawblade was considered. The roll-tensioning force was determined based on the measurement of the sawblade rolling profile, where it was established that the sawblade had been rolled with a force of 7800 N. The analysis showed that at the aforementioned force, the lateral stiffness was a maximum; here, the calculated and measured stiffnesses were 81 and 60 N/mm, respectively. The calculated natural frequencies agree well with the measured ones, where in the most important vibrational modes there is only a 7% difference. The maximum rotational speed for the sawblade was determined to be 85% of the critical speed. Because the sawblade was clamped with a ratio of clamping of only 0.25, the maximum rotational speed was amounted to 6630 rpm. Increasing the rolling force would increase the critical speed but greatly reduce the lateral stiffness.
COBISS.SI-ID: 2783625
The rapid worldwide evolution of LEDs as light sources has brought new challenges, which means that new methods are needed and new algorithms have to be developed. Since the majority of LED luminaries are of the multi-source type, established methods for the design of light engines cannot be used in the design of LED light engines. This is because in the latter case what is involved is not just the design of a good reflector or projector lens, but the design of several lenses which have to work together in order to achieve satisfactory results. Since lenses can also be bought off the shelf from several manufacturers, it should be possible to combine together different off the shelf lenses in order to design a good light engine. However, with so many different lenses to choose from, it is almost impossible to find an optimal combination by hand, which means that some optimization algorithms need to be applied. In order for them to work properly, it is first necessary to describe the input data (i.e. spatial light distribution) in a functional form using as few as possible parameters. In this paper the focus is on the approximation of the input data, and the implementation of the well-known mathematical procedure for the separation of linear and nonlinear parameters, which can provide a substantial increase in performance.
COBISS.SI-ID: 15491355
Broadcasting is the process of dissemination of a message from one vertex (called originator) to all other vertices in the graph. This task is accomplished by placing a sequence of calls between neighboring vertices, where one call requires one unit of time and each call involves exactly two vertices. Each vertex can participate in one call per one unit of time. Determination of the broadcast time of a vertex x in arbitrary graph G is NP-complete. Problem can be solved in polynomial time for trees and some subclasses of cactus graphs. In this paper broadcasting in cactus graphs is studied. An algorithm that determines broadcast time of any originator with time complexity O(n) in k-restricted cactus graph (where k is constant) is given. Furthermore, another algorithm which calculates broadcast time for all vertices in k-restricted cactus graph within the same time complexity is outlined. The algorithm also provides an optimal broadcast scheme for every vertex. As a byproduct, broadcast center of a k-restricted cactus graph is computed.
COBISS.SI-ID: 14221851
Given a positive integer $t$ and a graph $F$, the goal is to assign a subset of the color set $\{1,2, \dots , t\}$ to every vertex of $F$ such that every vertex with the empty set assigned has all $t$ colors in its neighborhood. Such an assignment is called the $t$-rainbow dominating function ($t$RDF) of the graph $F$. A $t$RDF is independent ($It$RDF) if vertices assigned with non-empty sets are pairwise non-adjacent. The weight of a ($t$RDF) $g$ of a graph $F$ is the value $w(g)=\sum_{v \in V(F)} |g(v)|$. The independent $t$-rainbow domination number $i_{rt}(F)$ is the minimum weight over all $It$RDFs of $F$. In this article, it is proved that the independent $t$-rainbow domination problem is NP-complete even if the input graph is restricted to a bipartite graph or a planar graph, and the results of the study provide some bounds for the independent $t$v-rainbow domination number of any graph for a positive integer v$t$. Moreover, the exact values and bounds of the independent $t$-rainbow domination numbers of some Petersen graphs and torus graphs are given.
COBISS.SI-ID: 18014809
An analysis of a product line of small and medium-sized enterprises (SME) shows that products (component parts or assemblies) are quite similar in terms of design and technology, thus clusters of products are formed. For each cluster a production cell can be organized. According to the product line of a company a certain number of individual production cells is organized, while workshop production is retained for the remaining product line. The paper shows how clusters of products are designed on the basis of a product line data and how an ideal layout optimization is determined on the basis of the intensity of material flow. Layout optimization of a production cell is based on a combination of Schmigalla modified triangular method and the Schwerdfeger circular process. The method was applied on a cluster of 20 orders similar in design and technology that are processed at 10 workplaces. At the end of the article a transition from a theoretical O-cell to a real U-cell is suggested.
COBISS.SI-ID: 15898139