Comparing Boolean Operation Methods on 3D Solids

Geometric engines are developed to give answers on geometrical queries, such as, what is the volume of a shape? Developing, testing and maintaining a geometric engine which can be used generically to answer arbitrary geometric queries is a tedious and time consuming task. Thousands of work hours are being spent towards this purpose. A very important element of such geometric engines is the Boolean operations on 3D objects. Boolean operations can be used to develop powerful tools for CAD/CAM applications, by which, end users can save thousands of work hours during modeling. While robust Boolean operations on 3D objects are difficult to implement, once available, many geometric queries can be reduced to a collection of Boolean operations. This reduction would save thousands of hours for the developers of such CAD/CAM applications. The goal of this thesis is to compare the Boolean implementation of Tekla Structures with the Boolean implementation of CGAL and a recently introduced method, EMBER. Using the results of this thesis, Tekla Structures’ currently unidentified vulnerabilities in its Boolean implementation can be identified and thus, improved. Quantitative results showed that Tekla Structures’ Boolean implementation, while being fast, suffered in terms of robustness during the union and difference operations with respect to CGAL and EMBER while doing remarkably well in the intersection operations

Extended P-I diagram method

The pressure-impulse (P-I) diagram method is used in practice (for civilian and military applications) for predicting the level of damage sustained by structures when subjected to blast loads and for assessing the imposed loading regime. Each P-I curve is associated with a certain structural configuration as well as a specific form of blast load and level of damage sustained. When assessing the effect of different parameters (associated with the form of the imposed load and the design of the structure considered) on structural performance, a series of new P-I curves need to be derived. This paper presents an extended P-I diagram method, which is based on derivation of complementary diagrams that can define the effect of two parameters (e.g., the level of axial loading imposed onto a column and the level of damage sustained) on the quasi-static and impulsive asymptotes, thus governing the positions of P-I curves in the diagram plane. The extended P-I diagram method is presented in dimensional and normalised forms. The dimensional form simplifies the derivation of new P-I curves, while the normalised form simplifies the procedure adopted for assessing the behaviour of a certain structure when subjected to a new set of loads. The application of the proposed method is demonstrated in both forms using a typical reinforced concrete (RC) column subjected to a blast load. The column is modelled using finite element analysis capable of accounting for the nonlinear behaviour of concrete and steel. A novel method is proposed for material modelling of concrete. The new material model is validated at both material and structural levels against relevant experimental data. P-I diagrams are initially derived for the axially unloaded column, while complementary diagrams are derived for the column loaded by different axial forces. The framework of the extended P-I diagram method employed for the derivation of new P-I curves and the assessment of the level of damage sustained by the column when subjected to different loading conditions is provided herein.</p

Simulation of carbon nanostructures with a vacancy present

Carbon is a very special element given it can take part in millions of different chemical compounds due to its 4 valence electrons and its compact size to fit in larger molecules. Further, carbon forms allotropes. Most familiar allotropes of carbon are diamond and graphite. Graphene and carbon nanotube will be the two allotropes of carbon which will be the subject in this project. Both graphene and carbon nanotubes have unique mechanical, thermal, optic and electrical properties. Therefore, they are either in use, or can potentially be used, in myriad different applications in industries or research. Consequently, it is important for future development to understand the behavior of these allotropes in diverse settings. Main task of this project was to investigate the behavior and effect of vacancy defects (point defects) in graphene sheet and carbon nanotube of different sizes as a function of temperature. In order to study these behavior and effects, computer simulations on molecular dynamics were employed. This report will introduce the necessary chemistry and material science concepts as well as tools used in simulation of the structures. As a result of the simulations, diffusion of vacancies in the structures was observed. The simulations ran with a resolution of 1 femtoseconds in which the structures were heated from 0K to upwards of 4500K.The diffusions took place at high temperatures for both graphene and carbon nanotube