The Moore bound m(d, k) = 1 + d ∑k−1 i=0 (d − 1)i is a lower bound for the number of vertices of a graph by given girth g = 2k + 1 and minimal degree d. Hoffmann and Singleton [5], Bannai and Ito [1], Damerell [4] showed that graphs with d > 2 tight to this bound can only exist for girth 5 and degree 3, 7, 57. The difference to the Moore bound by given girth is called the excess of a graph. In ...

Terwilliger [15] has given the diameter bound d < (s 1)(k 1) + 1 for distance-regular graphs with girth 2s and valency k. We show that the only distance-regular graphs with even girth which reach this bound are the hypercubes and the doubled Odd graphs. Also we improve this bound for bipartite distance-regular graphs. Weichsel [17] conjectures that the only distance-regular subgraphs of a hyper...

The girth is the length of shortest cycle in a graph. Recently, the problem for computing the girth of a graph have been studied well. Itai and Rodeh developed the first non trivial algorithm for computing girth in general graphs. Their algorithm runs in O (nm) time in the worst case and it runs in O(n) time on average case. For unweighted planer graphs, Djidjev gave a O ( n log n ) time algori...

Lasers have been employed in a variety of welding applications for many years. And, as laser technology further develops and diversifies, its uses in welding continue to expand. This article provides an overview of high power lasers in keyhole welding. It then examines the characteristics and advantages of fiber laser sources for welding from Coherent | Rofin, in particular, and review a specif...

Although solidification cracking is not usually regarded as a serious problem when welding ferritic steels, improvements in the submerged arc welding process, using higher deposition rates and faster welding speeds, have led to welding conditions more likely to give cracking. Furthermore, the need to weld stronger tougher steels, where the inspection requirements are more stringent, has led to ...

This paper gives a review on the applications of artificial neural network in friction stir welding. Friction stir welding is a fairly new solid state joining process and has found numerous applications including in aerospace, marine, automotive, railway and many more. Artificial neural network (ANN) is a valued research area. Study has been done on mechanical properties of weldements. Keywords...

The fibrogenic potential of 11 different welding fumes and metallic aerosols, considered to be reference standard surrogates for the commonly used welding technologies and applications responsible for 70% of welders exposure, is screened by using the rat peritoneal macrophage (RPM) in vitro bioassay. Only one class of fumes, that from the manual metal are welding of stainless steel, shows disti...

D. Bajic, University of Montenegro, Faculty of Mechanical Engineering, G. Vladimirovich Kuzmenko, E.O. Paton Electric Welding Institute, National Academy of Sciences Ukraine, I. Samardžić, J.J.Strossmayer university of Osijek, Mechanical Engineering Faculty in Slavonski Brod, Croatia The paper presents up-to-date achievements in application of a new method of arc welding of various rail profi l...