TOTAL EDGE IRREGULAR LABELING FOR TRIANGULAR GRID GRAPHS AND RELATED GRAPHS

Let  be a graph with  and  are the set of its vertices and edges, respectively. Total edge irregular -labeling on  is a map from  to  satisfies for any two distinct edges have distinct weights. The minimum  for which the  satisfies the labeling is spoken as its strength of total edge irregular labeling, represented by . In this paper, we discuss the tes of triangular grid graphs, its spanning subgraphs, and Sierpiński gasket graphs

On The Edge Irregularity Strength of Firecracker Graphs F2,m

Let  be a graph and k be a positive integer. A vertex k-labeling  is called an edge irregular labeling if there are no two edges with the same weight, where the weight of an edge uv is . The edge irregularity strength of G, denoted by es(G), is the minimum k such that  has an edge irregular k-labeling. This labeling was introduced by Ahmad, Al-Mushayt, and Bacˇa in 2014.  An (n,k)-firecracker is a graph obtained by the concatenation of n k-stars by linking one leaf from each. In this paper, we determine the edge irregularity strength of fireworks graphs F2,m

Antarctic Ice from EPICA Dronning Maud Land and artificial creep test Ice

Ice, microstructures, subgrain boundaries, recrystallization, flow, deformation. - The primary objective of this thesis is the investigation of microstructures obtained from samples from the EPICA Dronning Maud Land ice core from Antarctica. The goal is to gain understanding of deformation processes an deformation-related recrystallization mechanisms using these structures. The structures are visualized with the new microstructure mapping method using the preferred sublimation along defect regions in the crystal. This method enables observation in high resolution as well as overview over a significant sample volume. In order to provide unambiguous proof of their deformational origin and to offer interpretation and characterization, experimental reproduction of the microstructural features are performed using creep tests. Subgrain boundaries and grain-boundary morphology are identified as the most direct effects of deformation and recrystallization processes, which are still easily observable. They can be used additionally to the conventional parameters (grain size, crystal-orientation distribution) to determine these mechanisms. Different sbugrain-boundary types observed in experimentally deformed samples as well as in natural ice indicate several formation processes. Results obtained from this new and novel data suggest a profound reconsideration of the classical tripartition of recrystallization regimes described in the literature in ice sheets. Instead, dynamic recrystallization in two of its forms (rotation recrystallization and strain-induced migration recrystallization) dominates the microstructure evolution in all depth regions of the EDML ice core. Results of systematic microstructure analysis of creep-test samples demonstrate ...thesi

SEQUIN: An imaging and analysis platform for quantification and characterization of synaptic structures in mouse

Synapses are crucial to brain function and frequent disease targets, but current analysis methods cannot report on individual synaptic component

Electrosharpening of Tungsten Probes for Arc Discharge Assembly of Carbon Nanotubes

Ultra-sharp tungsten probes fill a key role in science for allowing measurements and interactions at the nanoscale. However, their current method of fabrication is outdated, fundamentally limited in length, sharpness and consistency, and often referred to as an ‘art’. A new process of fabricating ultra-sharp tungsten probes known as ‘Tungstate Sharpening’ was invented. This electrochemical process utilises solely the WO42- by-product to create a gradient of etching which results in a sharpening effect. It was shown to electrochemically etch probes controllably over lengths from 0.5 – 4.5 mm with tip radii of 10 nm via a fully automated process. Tungstate sharpening overcomes many of the limitations of the previous methods as well as creating new opportunities for further research into electrosharpening. Tungstate sharpening was improved to use bulk coulometry analysis which allows users to select specific probe lengths. The process was also modified to allow etching of five probes simultaneously, which is fundamentally impossible with conventional techniques. Furthermore, this batch process was improved with the application of a magnetic field that reduced fabrication time and inconsistencies. Flow simulations were conducted to confirm experimental observations of the electrode separation influence on turbulence within the electrochemical system, supporting the underlying theory and observations of the tungstate layer. Finally, this processing technique was expanded with various materials and shapes to demonstrate versatility. Razor blades with edge radii of 40 nm were produced demonstrating that electrosharpening is no longer limited to ‘1D’ objects. Another process was developed to fabricate carbon nanotubes (CNTs) as a macroscopic material. ‘Arc Assembly’ was invented to explore the possibility of forming long chains of CNTs whilst maintaining the sp2 crystalline bonding within and between individual CNTs. For the first time, dielectrophoresis was combined with arc discharges to form ‘threads’ of CNTs using the tungsten probes produced. The tungsten probes were applied as electrodes for dielectrophoresis of CNT chains and simultaneous arcing between them. Multiple high voltage circuits with outputs ranging from beneath the breakdown threshold and negative K(ω) up to 1000 V and 8 MHz were constructed and tested. Dispersed carbon nanotube mixtures for a variety of dielectric organic fluids, solvents and polymers were placed between the electrodes. The resulting phenomenon was the assembly of dielectrophoretic chains with arc-induced adhesion between nanotubes: termed as “Arc Assembly”. As Arc Assembly was developed, the CNT threads were analysed using scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and Raman analysis. Observations were made of both amorphous and crystalline links between the CNTs, as well as embedded CNT chains within in-situ formed polymer composites. The process produced threads of carbon nanotubes up to 5 mm length, indicating that this may be a viable means of exploiting CNTs in every-day life

Manufacturing of continuous flow equipment

For the work of this thesis a proof of concept microreactor and pump have been designed. Open source technology was used where possible to reduce the manufacturing cost. The pump is a pseudo HPLC/Syringe pump hybrid which adopts designs from both pumping systems. It works by charging two volumes of liquid into the primary chamber while the secondary chamber discharges. When the charge of the primary chamber is complete half of the liquid is pumped into the secondary chamber and the other half gets discharged. This has the benefit of sharing a common drive to reduce cost. The pump did function; however, the 3D printed parts did not have sufficient rigidity to offset mechanical stress, thus flexing occurred. The micro-reactor that was developed, was unique to commercial units. It was not chemically or thermally bonded but clamped with a gasket sealing the channels. This provides the advantage of unblocking inert material in the reactor. The reactor disk that was clamped was a super alloy, namely, Hastelloy C276. The reactor was tested against two commonly used reactors, namely, Chemtrix3227 and Little Things Factory (MS+VS). A simple synthesis of ethyl acetate has been used as a model reaction for comparing. The test reactor did not perform as well as the commercial counterparts, however probable causes have been identified for potential future work. Both the pump and the reactor worked as a proof of concept system, however further development is required for commercialisation

Memory-Efficient and Parallel Simulation of Super Carbon Nanotubes

Carbon nanotubes (CNTs) received much attention since their description in Nature in 1991. In principle, a carbon nanotube is a rolled up sheet of graphene, which can be imagined as a honeycomb grid of carbon atoms. This allotrope of carbon has many interesting properties like high tensile strength at very low weight or its high temperature resistance. This motivates the application of CNTs in material science to create new carbon nanotube enforced materials. They also possess interesting electronic properties since CNTs show either metallic or semiconducting behavior, depending on their configuration. The synthesis of branched carbon nanotubes allows the connection of straight CNTs to carbon nanotubes networks with branched tubes employed as junction elements. One of these networks are the so-called super carbon nanotubes (SCNTs) that were proposed in 2006. In that case, each carbon-carbon bond within the honeycomb grid is replaced by a CNT of equal size and each carbon atom by a Y-branched tube with three arms of equal length and a regular angle of 120° between the arms. This results in a structure that originates from tubes and regains the outer shape of a tube. It is also possible to repeat this process, replacing carbon-carbon bonds not with CNTs but with SCNTs, leading to very regular and self-similar structures of increasingly higher orders. Simulations demonstrate that the SCNTs also exhibit very interesting mechanical properties. They are even more flexible than CNTs and thus are good candidates for high strength com- posites or actuators with very low weight. Other applications arise again in microelectronics because of their configurable electronic behavior and in biology due to the biocompatibility of SCNTs. Despite progress in synthesizing processes for straight and branched CNTs, the production of SCNTs is still beyond current technological capabilities. In addition, real experiments at nanoscale are expensive and complex and hence, simulations are important to predict properties of SCNTs and to guide the experimental research. The atomic-scale finite element method (AFEM) already provides a well-established approach for simulations of CNTs at the atomic level. However, the model size of SCNTs grows very fast for larger tubes and the arising n-body and linear equation systems quickly exceed the memory capacity of available computer systems. This renders infeasible the simulation of large SCNTs on an atomic level, unless the regular structure of SCNTs can be taken into account to reduce the memory footprint. This thesis presents ways to exploit the symmetry and hierarchy within SCNTs enabling the simulation of higher order SCNTs. We develop structure-tailored and memory-saving data struc- tures which allow the storage of very large SCNTs models up to several billions of atoms while providing fast data access. We realize this with a novel graph data structure called Compressed Symmetric Graphs which is able to dynamically recompute large parts of structural information for tubes instead of storing them. We also present a new structure-aware and SMP-parallelized matrix-free solver for the linear equation systems involving the stiffness matrix, which employs an efficient caching mechanism for the data during the sparse matrix-vector multiplication. The matrix-free solver is twice as fast as a compressed row storage format-based reference solver, requiring only half the memory while caching all contributions of the matrix employed. We demonstrate that this solver, in combination with the Compressed Symmetric Graphs, is able to instantiate equation systems with matrices of an order higher than 5∗10^7 on a single compute node, while still fully caching all matrix data

Mechanical and Failure Properties of Rigid Polyurethane Foam Under Tension

Ph.DDOCTOR OF PHILOSOPH

Strategies in 3 and 5-axis abrasive water jet machining of titanium alloys

L'alliage de titane est généralement utilisé pour les pièces structurelles aéronautiques ayant une taille importante et ainsi que des parois minces tout en devant résister à des efforts considérables. L'usinage de ces pièces est difficile avec les méthodes classiques telles que le fraisage, car les forces de coupe sont élevées et les parois minces peuvent être facilement déformées. L'usinage de l'alliage de titane (Ti6Al4V) par un procédé utilisant un jet d'eau abrasif (AWJ) peut potentiellement être utilisé pour remplacer les méthodes d'usinage conventionnelles. Cependant, la compréhension des différents aspects de ce procédé est insuffisante pour autoriser son industrialisation. Cette thèse présente un modèle de prévision de la profondeur usinée dans deux cas de direction du jet : un jet perpendiculaire à la surface de la pièce et un jet incliné. Dans un premier temps, la compréhension du processus d'enlèvement de matière et de la qualité de surface obtenue est étudiée à travers l'observation de l'influence des paramètres du processus. Dans un second temps, un modèle basé sur la distribution gaussienne des particules abrasives dans le jet d'eau est proposé pour caractériser un passage élémentaire et pour prédire le profil du fond de poche obtenu par une succession de passages élémentaires. Ensuite, une méthodologie d'usinage des coins de poche utilisant un contrôle adaptatif de la vitesse d'avance est présentée. Enfin un nouveau modèle du profil du fond de poche prenant en compte l'angle d'inclinaison du jet est présenté. Tout au long de ce travail de thèse, la validation expérimentale a montré un bon accord entre les valeurs mesurées et modélisées et a ainsi démontré la capacité du jet d'eau abrasif à usiner à une profondeur contrôlée.Titanium alloy is generally used for aeronautical structural parts having a large size and as thin walls while having to withstand considerable effort. Machining these parts is difficult with conventional methods such as milling, because the high cutting forces can easily deform the part. Machining of titanium alloy (Ti6Al4V) by an abrasive water jet (AWJ) process can potentially be used to replace conventional machining methods. However, the understanding of the different aspects of this process is insufficient to allow its industrialization. This thesis presents a model of prediction of the machined depth in two cases of direction of the jet: a jet perpendicular to the surface of the part and an inclined jet. At first, the understanding of the removal material process and the obtained surface quality is studied through the observation of the influence of the process parameters. In a second step, a model based on the Gaussian distribution of abrasive particles in the water jet is proposed to characterize an elementary pass and to predict the pocket bottom profile obtained by a succession of elementary passes. Then, a method to machine pocket corners using an adaptive control of the feed rate is presented. Finally, a new model of the pocket bottom profile taking into account the angle of inclination of the jet is presented. Throughout this thesis work, the experimental validation showed a good agreement between the measured and modeled values and thus demonstrated the ability of the abrasive water jet milling to machine to a controlled depth