Cellular Automata

Modelling and simulation are disciplines of major importance for science and engineering. There is no science without models, and simulation has nowadays become a very useful tool, sometimes unavoidable, for development of both science and engineering. The main attractive feature of cellular automata is that, in spite of their conceptual simplicity which allows an easiness of implementation for computer simulation, as a detailed and complete mathematical analysis in principle, they are able to exhibit a wide variety of amazingly complex behaviour. This feature of cellular automata has attracted the researchers' attention from a wide variety of divergent fields of the exact disciplines of science and engineering, but also of the social sciences, and sometimes beyond. The collective complex behaviour of numerous systems, which emerge from the interaction of a multitude of simple individuals, is being conveniently modelled and simulated with cellular automata for very different purposes. In this book, a number of innovative applications of cellular automata models in the fields of Quantum Computing, Materials Science, Cryptography and Coding, and Robotics and Image Processing are presented

In-situ synchrotron X-ray imaging and tomography studies of the evolution of solidification microstructures under pulse electromagnetic fields

This research studies the dynamic evolution of dendritic structures and intermetallic phases of four Al based alloys during the solidification under pulse electromagnetic fields (PMFs). An advanced PMF solidification device was upgraded, built, commissioned for the research. The alloys used were Al-15Cu, Al-35Cu, Al-15Ni and Al-5Cu-1.5Fe-1Si. Systematic in-situ and real-time observation and studies were carried out at the TOMCAT beamline of Swiss Light Source, I13-2 beamline of Diamond Light Source and ID19 beamline of European Synchrotron Radiation Facility in the duration of this project. Synchrotron X-ray radiography and tomography were used primarily to observe and study the influence of PMFs on the nucleation and growth of primary dendritic structures and intermetallic phases under different magnetic flux and solidification conditions for the four alloys. More than 20 TB images and tomography datasets have been obtained throughout this research. Much effort and time was spent on segmenting, visualising and analysing these huge datasets using the Hull University supercomputer cluster, Viper, and the software, Avizo, ImageJ (Fiji), etc to explore and extract new insights and new science from those datasets. In particular, the skeletonisation function available from Avizo was customised and used to quantify the complex 3D microstructures and interconnected networks of different phases for the alloys. The important new findings of the research are:(1) Fragmentation of primary Al dendrites in the Al-15%Cu alloy was found when the magnetic flux of PMF applied is above 0.75 T; similarly, the fragmentation of Al3Ni intermetallic phases in the Al-15%Ni alloy was also observed when the magnetic flux of PMF applied is above 0.8 T. The clear and real-time observation of the fragmentation events in both dendritic and intermetallic phases provide unambiguous evidence to demonstrate that PMFs play a dominant role in structure fragmentation and multiplication, which is one important mechanism for structure (grain) refinement.(2) PMFs also produces pinch pressure gradient inside the semi-solid melt. Due to the different magnetic anisotropic properties between the liquid and solid phases, shear stresses due to the pinch pressure gradient may be produced. In the case of Al-15%Ni alloy, shear stresses of up to 30 MPa is created, which is sufficient to fracture Al3Ni phases. For the first time, such fragmentation mechanism for the Al3Ni phases in the Al-15%Ni alloy was revealed in this research.(3) The transition (or change of growth modes) of Al columnar dendrites to seaweed type dendrites in Al-15Cu alloy; and the facet growth to dendritic growth of the Al3Ni phases in the Al-15%Ni alloy were also observed in real-time when the magnetic flux is in the range of 0.75~0.8 T. Again, such dynamic changes in structure growth under PMFs are due to the enhanced melt flow caused by the applied fields.(4) In-situ tomography observation of PMF processing of the Al-5Cu-1.5Fe-1Si alloy also shows the effect of PMF on the refinement of the Chinese script type Fe intermetallic phases. In addition, the true 3D morphologies of three different types of Fe intermetallic phases in this alloy were clarified, again for the first time, in this research

Computer-Generated Holography for Areal Additive Manufacture

With a market of approximately $10B, additive manufacture (AM) is an exciting next-generation technology with the promise of significant environmental and societal impact. AM promises to help reduce emissions and waste during manufacture while improving sustainability. Widely used in applications from hip implants to jet engines, AM remains the domain of experts due to the material and thermal challenges encountered. AM in metals is dominated by Laser Powder Based Fusion (L-PBF). Powder is spread in layers 10s of microns thick and selectively melted by scanning a small laser spot heat source over the bed. Traditional AM systems have limited ability to manage or compensate for heat generated. The rapidly moving heat source spot results in high thermal cycling and is a major influence on residual stress and distortion. Mechanical limitations in the galvoscanner mean that over or under-heating is common and can lead to voids, boiling and spatter. The scale difference between the part size and the spot size means that predictive modelling is beyond the scope of even today’s best computing clusters. These factors have led to frequent inability to ensure part quality without physical prototyping and destructive testing. This thesis sets out initial research into creating a radically new AM process that uses computer-generated holography (CGH) to produce complex light patterns in a single pulse. Projecting power to the whole layer at once will mean that the thermal properties of the powders before and after writing can be factored into the processed hologram and part design. It will also significantly reduce thermal gradients and melt-pool instability. The fields of additive manufacture and computer-generated holography are introduced in Chapter 1. Chapters 2 and 3 then provide more detail on CGH and AM modelling respectively. The first deliverable, a reusable software package capable of generating holograms, is presented in Chapter 4. Algorithms developed for the project are introduced in Chapter 4.3. The first project demonstrator, an AM machine capable of printing in resins using holographic projection is discussed in Section 6.2. This shows performance comparable to modern 3D printing machines and highlights the applicability of computer-generated holography to areal processes. Section 6.3 then discusses the ongoing development of a metal powder demonstrator. As this PhD forms the first stage of a larger project, only preliminary work on the powder demonstrator is discussed. Chapter 7 then draws conclusions and outlines the way forward for future research. The thesis appendices then discuss an in-depth discussion of algorithm performances in Appendices A and B. Appendices C and D then discuss digressions into the implementation. Appendices E and F present a laser induced damage threshold (LIDT) measurement system developed. Finally, Appendices G and H provide more detail on the software developed and Appendix I gives links to additional project resources.EP/T008369/1; EP/L016567/1; EP/V055003/

Optimization of Secondary Cooling Parameters of Continuous Steel Casting

Plynulé odlévání je dominantní způsob výroby oceli, pomocí kterého je v současné době vyráběno více než 95 % veškeré celosvětové produkce oceli. Matematické modelování a optimální řízení provozu licího stroje patří mezi klíčové úlohy při plynulém odlévání oceli, které významným způsobem ovlivňují produktivitu a kvalitu vyráběné oceli, konkurenceschopnost ocelárny, bezpečnost při provozu licího stroje a jeho dopad na životní prostředí. Tato práce se zabývá vývojem a implementací numerického modelu teplotního pole plynule odlévaného sochoru a jeho využitím při optimálním řízení dynamického provozu licího stroje. Počítačový model byl vytvořen a implementován v MATLABu. Z důvodu vysoké výpočetní náročnosti byl model paralelizován pomocí výpočtu na grafických kartách NVIDIA s využitím architektury CUDA. Ověření modelu bylo provedeno na základě provozních dat z Třineckých železáren. Vyvinutý model byl následně použit jako základ prediktivního řídícího systému pro řízení dynamických změn při provozu licího stroje. Činnost vyvinutého řídícího systému byla ověřena na modelových dynamických situacích, které potvrdily schopnost navrženého řídícího systému optimálně řídit dynamický provoz licího stroje. Počítačový model teplotního pole a prediktivní řídící systém byly vytvořeny tak, že je lze modifikovat pro libovolný licí stroj, což umožňuje jejich případné komerční použití.Continuous casting is a dominant production technology of steelmaking which is currently used for more that 95% of the world steel production. Mathematical modelling and optimal control of casting machine are crucial tasks in continuous steel casting which directly influence productivity and quality of produced steel, competitiveness of steelworks, safety of casting machine operation and its impact on the environment. This thesis concerns with the development and implementation of the numerical model of temperature field for continuously cast steel billets and its use for optimal control of the casting machine. The numerical model was developed and implemented in MATLAB. Due to computational demands the model was parallelized by means of the computation on graphics processing units NVIDIA with the computational architecture CUDA. Validation and verification of the model were performed with the use of operational data from Trinecke zelezarny steelworks. The model was then utilized as a part of the developed model-based predictive control system for the optimal control of dynamic situations in the casting machine operation. The behaviour of the developed control system was examined by means of dynamic model situations that have confirmed the ability of the implemented system to optimally control dynamic operations of the continuous casting machine. Both the numerical model of the temperature field and the model-based predictive control system have been implemented so that they can be modified for any casting machine and this allows for their prospective commercial applications.

Development and application of real-time and interactive software for complex system

Soft materials have attracted considerable interest in recent years for predicting the characteristics of phase separation and self-assembly in nanoscale structures. A popular method for demonstrating and simulating the dynamic behaviour of particles (e.g. particle tracking) and to consider effects of simulation parameters is cell dynamic simulation (CDS). This is a cellular computerisation technique that can be used to investigate different aspects of morphological topographies of soft material systems. The acquisition of quantitative data from particles is a critical requirement in order to obtain a better understanding and of characterising their dynamic behaviour. To achieve this objective particle tracking methods considering quantitative data and focusing on different properties and components of particles is essential. Despite the availability of various types of particle tracking used in experimental work, there is no method available to consider uniform computational data. In order to achieve accurate and efficient computational results for cell dynamic simulation method and particle tracking, two factors are essential: computing/calculating time-scale and simulation system size. Consequently, finding available computing algorithms and resources such as sequential algorithm for implementing a complex technique and achieving precise results is critical and rather expensive. Therefore, it is highly desirable to consider a parallel algorithm and programming model to solve time-consuming and massive computational processing issues. Hence, the gaps between the experimental and computational works and solving time consuming for expensive computational calculations need to be filled in order to investigate a uniform computational technique for particle tracking and significant enhancements in speed and execution times. The work presented in this thesis details a new particle tracking method for integrating diblock copolymers in the form of spheres with a shear flow and a novel designed GPU-based parallel acceleration approach to cell dynamic simulation (CDS). In addition, the evaluation of parallel models and architectures (CPUs and GPUs) utilising the mixtures of application program interface, OpenMP and programming model, CUDA were developed. Finally, this study presents the performance enhancements achieved with GPU-CUDA of approximately ~2 times faster than multi-threading implementation and 13~14 times quicker than optimised sequential processing for the CDS computations/workloads respectively

Microdroplet Impact onto Topographies of Commensurate Size

As inkjet technology develops to produce smaller droplets, substrate features such as accidental scratches or manufacturing defects can potentially affect the outcome of printing, particularly for printed electronics where continuous tracks are required. Here, the deposition of micro--droplets onto an idealised scratch of commensurate size is studied using a GPU--accelerated 3D multiphase lattice Boltzmann model validated against published experiments and theoretical models. The scratch is considered as a groove of rectangular cross--section, with rectangular side ridges representing material displaced from the substrate, and seven equilibrium morphologies are identified as a result of inertial spreading, contact line pinning, imbibition into the scratch and capillary flow. A regime map is constructed in terms of scratch depth and width, and theoretical estimates of the regime boundaries are developed by adapting droplet spreading laws for flat surfaces to account for liquid entering the scratches. Good agreement with the numerical results is seen, and the influences of Reynolds number, Weber number and advancing and receding contact angles are explored. Negative and positive implications of the results for printing applications are discussed and illustrated via multiple--droplet simulations of printing across and along scratches

Defect-characterized phase transition kinetics

Phase transitions are a common phenomenon in condensed matter and act as a critical degree of freedom that can be employed to tailor the mechanical or electronic properties of materials. Understanding the fundamental mechanisms of the thermodynamics and kinetics of phase transitions is, thus, at the core of modern materials design. Conventionally, studies of phase transitions have, to a large extent, focused on pristine bulk phases. However, realistic materials exist in a complex form; their microstructures consist of different point and extended defects. The presence of defects impacts the thermodynamics and kinetics of phase transitions, but has been commonly ignored or treated separately. In recent years, with the significant advances in theoretical and experimental techniques, there has been an increasing research interest in modeling and characterizing how defects impact or even dictate phase transitions. The present review systematically discusses the recent progress in understanding the kinetics of defect-characterized phase transitions, derives the key mechanisms underlying these phase transitions, and envisions the remaining challenges and fruitful research directions. We hope that these discussions and insights will help to inspire future research and development in the field

Numerical Simulations of Shock and Rarefaction Waves Interacting With Interfaces in Compressible Multiphase Flows

Developing a highly accurate numerical framework to study multiphase mixing in high speed flows containing shear layers, shocks, and strong accelerations is critical to many scientific and engineering endeavors. These flows occur across a wide range of scales: from tiny bubbles in human tissue to massive stars collapsing. The lack of understanding of these flows has impeded the success of many engineering applications, our comprehension of astrophysical and planetary formation processes, and the development of biomedical technologies. Controlling mixing between different fluids is central to achieving fusion energy, where mixing is undesirable, and supersonic combustion, where enhanced mixing is important. Iron, found throughout the universe and a necessary component for life, is dispersed through the mixing processes of a dying star. Non-invasive treatments using ultrasound to induce bubble collapse in tissue are being developed to destroy tumors or deliver genes to specific cells. Laboratory experiments of these flows are challenging because the initial conditions and material properties are difficult to control, modern diagnostics are unable to resolve the flow dynamics and conditions, and experiments of these flows are expensive. Numerical simulations can circumvent these difficulties and, therefore, have become a necessary component of any scientific challenge. Advances in the three fields of numerical methods, high performance computing, and multiphase flow modeling are presented: (i) novel numerical methods to capture accurately the multiphase nature of the problem; (ii) modern high performance computing paradigms to resolve the disparate time and length scales of the physical processes; (iii) new insights and models of the dynamics of multiphase flows, including mixing through hydrodynamic instabilities. These studies have direct applications to engineering and biomedical fields such as fuel injection problems, plasma deposition, cancer treatments, and turbomachinery.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133458/1/marchdf_1.pd

Fracture, Fatigue, and Structural Integrity of Metallic Materials and Components Undergoing Random or Variable Amplitude Loadings

Most metallic components and structures are subjected, in service, to random or variable amplitude loadings. There are many examples: vehicles subjected to loadings and vibrations caused by road irregularity and engine, structures exposed to wind, off-shore platforms undergoing wave-loadings, and so on. Just like constant amplitude loadings, random and variable amplitude loadings can make fatigue cracks initiate and propagate, even up to catastrophic failures. Engineers faced with the problem of estimating the structural integrity and the fatigue strength of metallic structures, or their propensity to fracture, usually make use of theoretical, numerical, or experimental approaches. This reprint collects a series of recent scientific contributions aimed at providing an up-to-date overview of approaches and case studies—theoretical, numerical or experimental—on several topics in the field of fracture, fatigue strength, and the structural integrity of metallic components subjected to random or variable amplitude loadings

Simulated Annealing

The book contains 15 chapters presenting recent contributions of top researchers working with Simulated Annealing (SA). Although it represents a small sample of the research activity on SA, the book will certainly serve as a valuable tool for researchers interested in getting involved in this multidisciplinary field. In fact, one of the salient features is that the book is highly multidisciplinary in terms of application areas since it assembles experts from the fields of Biology, Telecommunications, Geology, Electronics and Medicine