THE concept of HNN-extensions of groups was introduced by Higman, Neumann and Neumann in 1949. HNN-extensions and amalgamated free products have played a crucial role in combinatorial group theory, especially for algorithmic problems. In inverse semigroup theory there are many ways of constructing HNNextension in order to ensure the embeddability of the original inverse semigroup in the new one...

background: a comprehensive database, comprising geometry and properties of human teeth, is needed for dentistry education and dental research. the aim of this study was to create a three-dimensional model of human teeth to improve the dental e-learning and dental research.   methods: in this study, a cross-section picture of the three-dimensional model of the teeth was used. ct-scan images wer...

in this paper, an experimental and numerical investigation into the effect of the hoop welding in metallic pressure vessel is presented. in the experimental manufacturing, hoop welding was used to attach the cylindrical body of the vessel, and the effect of welding into stress and strain distribution is carried out. experimental strains are obtained by using the strain gauges attached to predet...

there are many parameters that affect the sheet hydroforming process such as fluid pressure, material properties, interfacial friction between blank and tool surfaces, etc. in this paper, a fem-based taguchi method is used to determine the effects of forming parameters on the quality of part formability in the process of hydrodynamic deep drawing assisted by radial pressure. four important form...

statement of problem: currently there are three recognized theories about the diameter of prepared dowel space in endodontically treated teeth. diameter of the dowel is commonly contributed to the root fracture. purpose: this study used a 3 dimensional (3d) finite element method to predict stress distribution in endodontically treated central maxillary tooth with cast post and core with various...

stability of foundations near slopes is one of the important and complicated problems in geotechnical engineering, which has been investigated by various methods such as limit equilibrium, limit analysis, slip-line, finite element and discrete element. the complexity of this problem is resulted from the combination of two probable failures: foundation failure and overall slope failure. the curr...

loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. one of the most important durability problems in diesel engines is due to the cracks valves bridge area. the purpose of this study is a thermo-mechanical analysis of cylinder heads of diesel engines using a two-layer viscoplasticity model. in this article, mechanical prope...

permanent magnet synchronous motors are efficient motors, which have widespread applications in electric industry due to their noticeable features. one of the interesting applications of such motors is in underwater vehicles. in these cases, reaching to minimum volume and high torque of the motor are the major concern. design optimization can enhance their merits considerably, thus reduce volum...