Дисертації з теми "Particle dynamic"
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1
Kim, JaeMo. "Dynamic simulation of suspended particles and drops at finite Reynolds numbers by dissipative particle dynamics /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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2
Wang, Ge 1965. "Particle modeling of dynamic fragmentation." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102230.
Повний текст джерелаАнотація:
In this paper, we first theoretically revise the traditional particle modeling (PM) by means of mathematical derivation in that, adopting of Lennard Jones (LJ) format equations, four conservative rules are satisfied in order to determine the four unknown in a LJ equation, such as the mass, the elastic energy, the Young's modulus and the tensile strength conservations in the PM and molecular dynamic (MD) models. This enables the new developed PM to uniquely define a material's properties to be studied and promisingly become a predictive tool in mining industries. A safe time increment scheme is also defined and a new modification to the model to avoid giving a pseudo-dynamic solution.Consequently, we test this new PM by simulating fracture response of an elastic-brittle material---epoxy, with randomly distributed holes, in tension and then comparing the model results with the experiments.
Then, we use this developed PM to many applications, such as (i) simulating dynamic fragmentation of minerals encountered in comminution and blasting processes in the mining industry. In particular, we simulate single as well as multi-phase materials in two dimensions (2-D) and 3-D. We redefine the interactive particle relationship by which material impact-collision problems are realistically simulated and computational time is saved as well; (ii) investigating cracking propagation of a plate with crack-tip under mode-I loading.
3
Rafferty, Thomas. "Dynamic properties of condensing particle systems." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/91746/.
Повний текст джерелаАнотація:
Condensation transitions are observed in many physical and social systems, ranging from Bose-Einstein condensation to traffic jams on the motorway. The understanding of the critical phenomena prevalent in these systems presents many interesting mathematical challenges. We are interested in understanding the various definitions of condensation which are suitable in the field of stochastic particle systems and how they are related. Furthermore, we are also interested in dynamic properties of processes that undergo the condensation transition, such as typical convergence time scales and monotonicity properties. Condensation can be defined in many different ways; considering the thermodynamic limit, a weak law of large numbers for the maximum occupation number, and an infinite particle limit on fixed finite lattices. For the latter definition, and processes that exhibit a family of stationary product measures, we prove an equivalent characterisation in terms of sub-exponential distributions generalising previous known results. All known examples of condensing processes that exhibit homogeneous stationary product measures are non-monotone, i.e. the dynamics do not preserve a partial ordering of the state space. This non-monotonicity is typically characterised by an overshoot of the canonical current, which on a heuristic level is related to metastability. We prove that these processes with a finite critical density are necessarily non-monotone confirming a previous conjecture. If the critical density is infinite, condensation can still occur on finite lattices. We present partial evidence that there also exist monotone condensing processes. We also study the typical convergence time scales of condensing inhomogeneous zero-range processes. Our results represent a first rigours calculation of the relaxation time of a condensing zero-range process, where we prove a dynamic transition in the order of the relaxation time as the density crosses a critical value. We also derive bounds for homogeneous condensing models and obtain results consistent with known metastable time scales.
4
Urade, Hemlata S., and Rahila Patel. "Performance Evaluation of Dynamic Particle Swarm Optimization." IJCSN, 2012. http://hdl.handle.net/10150/283597.
Повний текст джерелаАнотація:
Optimization has been an active area of research for
several decades. As many real-world optimization
problems become increasingly complex, better
optimization algorithms are always needed.
Unconstrained optimization problems can be formulated
as a D-dimensional minimization problem as follows:
Min f (x) x=[x1+x2+……..xD]
where D is the number of the parameters to be optimized.
subjected to: Gi(x) <=0, i=1…q
Hj(x) =0, j=q+1,……m
Xε [Xmin, Xmax]D, q is the number of inequality
constraints and m-q is the number of equality constraints.
The particle swarm optimizer (PSO) is a relatively new
technique. Particle swarm optimizer (PSO), introduced by
Kennedy and Eberhart in 1995, [1] emulates flocking
behavior of birds to solve the optimization problems.In this paper the concept of dynamic particle swarm optimization is introduced. The dynamic PSO is different from the existing PSO’s and some local version of PSO in terms of swarm size and topology. Experiment conducted for benchmark functions of single objective optimization problem, which shows the better performance rather the basic PSO. The paper also contains the comparative analysis for Simple PSO and Dynamic PSO which shows the better result for dynamic PSO rather than simple PSO.
5
Devarakonda, SaiPrasanth. "Particle Swarm Optimization." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1335827032.
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6
Cavallo, Antonio. "Four dimensional particle tracking in biological dynamic processes." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964904667.
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Li, Changhe. "Particle swarm optimization in stationary and dynamic environments." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10284.
Повний текст джерелаАнотація:
Inspired by social behavior of bird flocking or fish schooling, Eberhartand Kennedy first developed the particle swarm optimization (PSO) algorithm in 1995. PSO, as a branch of evolutionary computation, has been successfully applied in many research and application areas in the past several years, e.g., global optimization, artificial neural network training, and fuzzy system control, etc… Especially, for global optimization, PSO has shown its superior advantages and effectiveness. Although PSO is an effective tool for global optimization problems, it shows weakness while solving complex problems (e.g., shifted, rotated, and compositional problems) or dynamic problems (e.g., the moving peak problem and the DF1 function). This is especially true for the original PSO algorithm. In order to improve the performance of PSO to solve complex problems, we present a novel algorithm, called self-learning PSO (SLPSO). In SLPSO, each particle has four different learning strategies to deal with different situations in the search space. The cooperation of the four learning strategies is implemented by an adaptive framework at the individual level, which can enable each particle to choose the optimal learning strategy according to the properties of its own local fitness landscape. This flexible learning mechanism is able to automatically balance the behavior of exploration and exploitation for each particle in the entire search space during the whole running process. Another major contribution of this work is to adapt PSO to dynamic environments, we propose an idea that applies hierarchical clustering techniques to generate multiple populations. This idea is the first attempt to solve some open issues when using multiple population methods in dynamic environments, such as, how to define the size of search region of a sub-population, how many individuals are needed in each sub-population, and how many sub-populations are needed, etc. Experimental study has shown that this idea is effective to locate and track multiple peaks in dynamic environments.
8
Sharma, Samvaran. "DARTPIV : Dynamic Adaptive Real-Time Particle Image Velocimetry." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85496.
Повний текст джерелаАнотація:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 65-67).
Particle Image Velocimetry (PIV) is a technique that allows for the detailed visualization of fluid flow. By performing computational analysis on images taken by a high-sensitivity camera that monitors the movement of laser-illuminated tracer particles over time, PIV is capable of producing a vector field describing instantaneous velocity measurements of the fluid captured in the field of view. Nearly all PIV implementations perform offline processing of the collected data, a feature that limits the scope of the applications of this technique. Recently, however, researchers have begun to explore the possibility of using FPGAs or PCs to greatly improve the efficiency of these algorithms in order to obtain real-time speeds for use in feedback loops. Such approaches are very promising and can help expand the use of PIV into previously unexplored fields, such as high performance Unmanned Aerial Vehicles (UAVs). Yet these real-time algorithms have the potential to be improved even further. This thesis outlines an approach to make real-time PIV algorithms more accurate and versatile in large part by applying principles from another emerging technique called adaptive PIV, and in doing so will also address new issues created from the conversion of traditional PIV to a real-time context. This thesis also documents the implementation of this Dynamic Adaptive Real- Time PIV (DARTPIV) algorithm on a PC with CUDA parallel computing, and its performance and results analyzed in the context of normal real-time PIV.
by Samvaran Sharma.
M. Eng.
9
Wu, Yadong Carleton University Dissertation Mathematics. "Dynamic particle systems and multilevel measure branching processes." Ottawa, 1991.
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10
Bao, Yanyao. "Smoothed Particle Hydrodynamics Simulations for Dynamic Capillary Interactions." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19592.
Повний текст джерелаАнотація:
Complex interactions in porous media play an important role on many industrial and geotechnical applications, such as groundwater treatment, porous catalysts, carbon geosequestration, and oil recovery. Rate-dependent wetting effects are of great significance in understanding the multiphase behaviours of porous media thus further throw light on engineering solutions to the above problems. In this thesis, a modified smoothed particle hydrodynamics (SPH) model is applied to simulate (1) the contact angle dynamics and (2) stretching of liquid bridge at meso-scale. This SPH model adopted an inter-particle force formulation with short-range repulsive force and long-range attractive force to take into account single-phase and multiphase interactions. Particularly, a newly-introduced viscous force is imposed at the liquid-solid interface to capture the rate-dependent behaviours of contact angle without prescribing additional arbitrary condition or force. After identification of model parameters, the rate-dependent contact angle behaviours are studied for both wetting and dewetting phenomena. By analysing the contact angle results of fluid at triple-line region with different moving speeds, the dynamic contact angles and corresponding capillary numbers can be correlated by power law functions. The derived correlation and constants are compared with different forms of empirical power law functions and the results are satisfactory. Moreover, we investigated the properties of stretching liquid bridges, including shape evolution, liquid transfer ratio and flow condition under dynamic loading. Different stretching rates are applied, and the shapes of liquid bridge at same breakup distance is presented. By differentiating the wettability of top and bottom substrates, the liquid transfer ratio regarding wettability difference and substrate moving speed is studied.
11
Song, Yongxin. "Study of the dynamic behavior of tablet movement in a rotating drum using discrete element modeling (DEM) method." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4681.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 110 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 105-110).
12
Robinson, Craig David. "Particle simulations on parallel computers with dynamic load balancing." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269198.
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Said, Mohd Farid bin Muhamad. "Development of particle sizing based on dynamic image analysis." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10246.
Повний текст джерелаАнотація:
Dispersion of particles in multiphase-flows can be both quantitatively and qualitatively characterised using modern optical or nonintrusive devices. The development of a nonintrusive particle sizer (NPS) is performed. This device employs a high intensity pulsed laser as a light source and a digital camera to capture the particle images. The dynamic image analysis (DIA) software is designed to analyse the captured images and control the inputs and outputs of the data. The NPS has the ability to operate using shadow sizing, direct illumination (DI) and particle mixture shadow (PMS) techniques. The architecture and working principles of each technique are described in detail. A novel technique, which is Particle Mixture Shadow has been developed for the characterisation of solid/liquid mixture dispersed in air. The capability of the technique to distinguish and size the solid and liquid particles is demonstrated. The sensitivities of laser intensity, image magnification factor and scattering angle on the accuracy of particle size have been investigated. In order to evaluate the repeatability and the accuracy of the NPS device, the measurements of certified microsphere particle sizes are repeated several times. The results are then validated against proprietary particles with specification data provided by the manufacturer. The particle size error of the developed device confirms that it has a good repeatability in sizing the particles. The device is applied to solid and liquid particles dispersed in fluid media using shadow and DI techniques. The results comparison between these techniques is also demonstrated.
14
Brackstone, Mark Andrew. "Dynamic properties of models of modulated systems in condensed matter." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.255764.
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15
Botero, Cristina, Heiko Kremer, Andreas P. Fröba, and Alfred Leipertz. "Particle diffusion coefficient and dynamic viscosity in non-ideal liquid mixtures by dynamic light scattering." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196233.
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Botero, Cristina, Heiko Kremer, Andreas P. Fröba, and Alfred Leipertz. "Particle diffusion coefficient and dynamic viscosity in non-ideal liquid mixtures by dynamic light scattering." Diffusion fundamentals 2 (2005) 67, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14401.
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Thornton, Stuart C. "Computational volume dynamic analysis of a particle beam cluster source." Thesis, University of Leicester, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.552750.
Повний текст джерелаАнотація:
This thesis is an investigation using the finite volume method to examine the flow of carrier gas and nanoparticles through a particle beam cluster machine. Nanoparticle clusters are a relatively new material, which often have novel properties due to the ratio of the number of atoms at their surface compared to number of atoms within their volume. Although two dimensional, it offers an insight into the characteristic sonic/supersonic expansion of a free gas jet into a partial vacuum. Tests were performed with different geometry and pressure, to view changes of the nanoparticle trajectory through the cluster machine. The aim is to use this greater understanding, to examine how the efficiency of a particle beam cluster machine can be improved.
18
Ab, Wahab M. N. "Self-limitation, dynamic and flexible approaches for particle swarm optimisation." Thesis, University of Salford, 2017. http://usir.salford.ac.uk/42351/.
Повний текст джерелаАнотація:
Swarm Intelligence (SI) is one of the prominent techniques employed to solve optimisation problems. It has been applied to problems pertaining to engineering, schedule, planning, networking and design. However, this technique has two main limitations. First, the SI technique may not be suitable for the online applications, as it does not have the same aspects of limitations as an online platform. Second, setting the parameter for SI techniques to produce the most promising outcome is challenging. Therefore, this research has been conducted to overcome these two limitations. Based on the literature, Particle Swarm Optimisation (PSO) was selected as the main SI for this research, due to its proven performances, abilities and simplicity. Five new techniques were created based on the PSO technique in order to address the two limitations. The first two techniques focused on the first limitation, while the other three techniques focused on the latter. Three main experiments (benchmark problems, engineering problems, path planning problems) were designed to assess the capabilities and performances of these five new techniques. These new techniques were also compared against several other well-established SI techniques such as the Genetic Algorithm (GA), Differential Equation (DE) and Cuckoo Search Algorithm (CSA). Potential Field (PF), Probabilistic Road Map (PRM), Rapidly-explore Random Tree (RRT) and Dijkstra’s Algorithm (DA) were also included in the path planning problem in order to compare these new techniques’ performances against Classical methods of path planning. Results showed all five introduced techniques managed to outperform or at least perform as good as well-established techniques in all three experiments.
19
Silwal, Shrawani. "A Dynamic Taxi Ride Sharing System Using Particle Swarm Optimization." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1588198872893409.
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20
Goel, Ashish. "Dynamic loading of structures by high speed granular media." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277444.
Повний текст джерелаАнотація:
This thesis analyses the impact of granular aggregates with structures using experiments and numerical simulations. Original contributions include an insight into multiple factors affecting the loading and damage to the structures, along with study of numerical parameters important for realistic prediction of the interaction between the granular media and structures. It extends the current understanding related to such interactions, with an underlying motivation to guide strategies in order to reduce the structural damage. The response of structures impacted by granular media (sand or soil) is of significant research interest for many applications. One of the applications is for landmine explosions which causes ejection of soil from ground and damage to structures impacted by this ejected soil. Experimentation is done in a laboratory setting where the cylindrical sand slugs are generated at high speed using an impulse provided by a piston. This induces a velocity gradient along the slug, because of which the slug expands during the flight before impacting the target. Deformable as well as rigid flat targets are considered in two orientations relative to the incoming slug: perpendicular (i.e. normal orientation) and inclined at an angle of 45°. The targets are supported by force transducers to capture the loading from the slug. Simulations are performed using a combination of discrete particle and finite element schemes, which enables the analysis of the fully coupled interaction between the flowing granular media and the structure. A contact model involving multiple parameters is used for inter-particle and particle-target contact. Firstly, a numerical analysis is performed to characterise the temporal evolution of slugs and their impact on monolithic beams constrained at the ends. Out of all the parameters used for inter-particle contact definition in discrete particle method, only the contact stiffness is found to effect the velocity gradient in the slug before it impacts the target. Other factor influencing the gradient is the acceleration provided by the piston. A strong dependence of beam deflection on the stand-off distance is observed due to the velocity gradient in the slugs. As the second step, the effect of target surface properties on the transmitted momentum is analysed. Experiments are done by applying coatings of different hardness and roughness on the target surface impacted by sand slugs. For normally oriented targets, the transmitted momentum is observed to be insensitive to the change in surface coating. In contrast, for inclined targets, a significant influence of coatings is observed. Additionally, the momentum transmitted to the inclined targets is always less than that for normal targets. Numerical analysis of this surface effect reveals that assuming the slug particles to be spherical shape in simulations does not capture the particle/target interactions accurately and under-predicts the frictional loading on the target. Following this, a detailed numerical study is done to understand the effect of the shape of particles in the slug. Simple shaped non-spherical particles are constructed by combining spherical sub-particles. With increasing angularity of particles in the slug, the frictional loading on the target is shown to increase. This results in an increase of momentum transmitted to inclined targets. For normally oriented targets however, the particle shape does not affect the overall transmitted momentum, which is a behaviour similar to that observed when studying the effect of target surface properties. In addition, effect of fracture of particles in the slug is analysed by using beam connections between sub-particles that break during the impact with the target. If the fracture results in increasing particle angularity, the transmitted momentum increases, whereas the situation reverses if fracture results on more spherical shaped particles. Lastly, a strategy to reduce the loading on the targets is analysed by using sacrificial coating on the target surface. In experiments, this coating is placed on the rigid target surface using a lubricant at their interface. When impacted by the slug, this coating slides on the target surface, resulting in a reduction of frictional loading on the target. If the friction at the coating/target interface vanishes, the transmitted momentum approaches the theoretical minimum value. Simulations are used to first validate the experimental observations and then to extend the concept of sliding coatings using deformable targets. Both the transmitted momentum and deflections depended on the thickness of the target and coating. When a coating is used, the deflections increase due to reduction in target thickness. It is found that the best strategy to reduce the damage to the target is to use least possible thickness of the coating and minimise the friction at the interface between the coating and the target. The presented work examines many of the factors that affect the loading on the target impacted by granular slugs, in addition to characterising the expansion of slugs before the target impact. The analysed factors include those already known such as target stand-off distance, inclination and unveils others such as target surface properties and granular properties. The numerical analysis discloses important parameters and shows the effect of particle shape, highlighting the shortcomings of widely used spherical particle assumption in the numerical studies. A strategy using a sacrificial coating to reduce damage to the target is also analysed.
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Alshammery, Anas Obeed Adras. "Modelling sintering at particle scale using variational and molecular dynamic methods." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42879.
Повний текст джерелаАнотація:
Sintering is the thermal process that uses powders to form a new dense product by increasing temperature but holding it under the melting point of the material in use. Modelling the sintering process is important for fundamental understanding the behaviour of the particles during the sintering process instead of through empirical experimental work. In the first part of this thesis, a simplified method is developed to model the solid state sintering process which depends on the coupling between grain boundary and surface diffusion. A curve fitting method was developed to create a new relationship that relates the chemical potential at the junction of the grain-boundary and free surface to the neck size and the ratio of grain-boundary diffusivity over surface diffusivity. This relationship enables the de-coupling between the two diffusional processes when modelling the sintering process. The sintering process can, therefore, be separately modelled from the surface diffusion process, which greatly simplified the model for problems involving many particles such as those in a discrete element model. The results of the curve fitting method were first compared with the analytical Coblenz equations to allow for the validation and proofing of the new method in terms of modelling the sintering process; thereafter, comparisons were made with the full finite difference model using two parameters, namely diffusion coefficient ratio and applied stress. The curve fitting model matched well with the full finite difference model for the two parameters. In the second part of this thesis, two stages were undertaken: firstly, the new method was used in a variational model to simulate the two copper particles, and was compared with a new curve fitting-finite difference method for two sintering ratios. The variational model results were in good agreement with the new curve fitting-finite difference method. Secondly, multiple particles of copper were used in a variational model to simulate selective laser sintering for 27 copper particles. Laser scan speed, laser power, and particle temperature were collected from the COMSOL model, after which the particle temperature was used in the variational model to calculate the neck growth and shrinkage ratios between particles for different particle sizes. In the third part of this thesis, a molecular dynamics simulation code, LAMMPS, was used to investigate and understand the behaviour of nano-copper in the sintering process. Firstly, the melting temperature of nano-copper for different nanoparticle sizes was calculated and compared to four analytical models, after which neck size and shrinkage ratios were determined and compared with different diffusion mechanisms. The melting temperature numerical results matched well with the analytical nano-copper model. The hollow nano-copper improved the sintering process compared to solid nano-copper. Nanoparticle sintering has different behaviours comparing to micro-particle sintering. The nanoparticle sintering process is faster than for microparticle sintering; moreover, the melting temperature of the nanoparticles changed depending on size, when compared with microparticles where the melting point was constant.
22
Zhu, Ting. "Color-Based Fingertip Tracking Using Modified Dynamic Model Particle Filtering Method." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306863054.
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Schön, Thomas B. "Estimation of Nonlinear Dynamic Systems : Theory and Applications." Doctoral thesis, Linköpings universitet, Reglerteknik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7124.
Повний текст джерелаАнотація:
This thesis deals with estimation of states and parameters in nonlinear and non-Gaussian dynamic systems. Sequential Monte Carlo methods are mainly used to this end. These methods rely on models of the underlying system, motivating some developments of the model concept. One of the main reasons for the interest in nonlinear estimation is that problems of this kind arise naturally in many important applications. Several applications of nonlinear estimation are studied. The models most commonly used for estimation are based on stochastic difference equations, referred to as state-space models. This thesis is mainly concerned with models of this kind. However, there will be a brief digression from this, in the treatment of the mathematically more intricate differential-algebraic equations. Here, the purpose is to write these equations in a form suitable for statistical signal processing. The nonlinear state estimation problem is addressed using sequential Monte Carlo methods, commonly referred to as particle methods. When there is a linear sub-structure inherent in the underlying model, this can be exploited by the powerful combination of the particle filter and the Kalman filter, presented by the marginalized particle filter. This algorithm is also known as the Rao-Blackwellized particle filter and it is thoroughly derived and explained in conjunction with a rather general class of mixed linear/nonlinear state-space models. Models of this type are often used in studying positioning and target tracking applications. This is illustrated using several examples from the automotive and the aircraft industry. Furthermore, the computational complexity of the marginalized particle filter is analyzed. The parameter estimation problem is addressed for a relatively general class of mixed linear/nonlinear state-space models. The expectation maximization algorithm is used to calculate parameter estimates from batch data. In devising this algorithm, the need to solve a nonlinear smoothing problem arises, which is handled using a particle smoother. The use of the marginalized particle filter for recursive parameterestimation is also investigated. The applications considered are the camera positioning problem arising from augmented reality and sensor fusion problems originating from automotive active safety systems. The use of vision measurements in the estimation problem is central to both applications. In augmented reality, the estimates of the camera’s position and orientation are imperative in the process of overlaying computer generated objects onto the live video stream. The objective in the sensor fusion problems arising in automotive safety systems is to provide information about the host vehicle and its surroundings, such as the position of other vehicles and the road geometry. Information of this kind is crucial for many systems, such as adaptive cruise control, collision avoidance and lane guidance.
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Johansson, Henrik. "Road-constrained target tracking using particle filter." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11562.
Повний текст джерелаАнотація:
In this work a particle filter (PF) that uses a one-dimensional dynamic model to estimate the position of vehicles traveling on a road is derived. The dynamic model used in the PF is a second order linear-Gaussian model. To be able to track targets traveling both on and off road two different multiple model filters are proposed. One of the filters is a modified version of the Efficient Interacting Multiple Model (E-IMM) and the other is a version of the Multiple Likelihood Models (MLM). Both of the filters uses two modes, one for the on road motion and one for the off road motion. The E-IMM filter and the MLM filter are compared to the standard PF to be able to see the performance gain in using multiple models. This result indicates that the multiple model filters have better performance, at least when the true mode switching probabilities are used.
Den här arbetet presenterar ett partikelfilter som använder sig av en endimensionell dynamisk modell för att skatta positionen på fordon som befinner sig på någon väg. Den dynamiska modellen som används i partikelfiltret är en andra ordningens linjär-gaussisk modell. För att kunna spåra fordon som befinner sig både på och utanför vägen så föreslås två olika multipla filter. Ena filtret är en modifierad
variant av Efficient Interacting Multiple Model (E-IMM) och den andra är en version a Multiple Likelihood Models (MLM). Båda filtren använder sig av två moder, en för rörelse på vägen och en för rörelse utanför vägen. E-IMM filtret och MLM filtret jämförs med ett standard partikelfilter för att kunna se förbättringen vid använding av multipla modeller. Resultatet visar att båda multipla modell filtren ger bättre resultat, i varje fall då rätt sannolikheter för modbyte används.
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Thompson, Ian. "Dynamic phase transitions in biased ensembles of particle systems with repulsive interactions." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665407.
Повний текст джерелаАнотація:
We study dynamic phase transitions in the constant-volume and constant- pressure ensembles of two different systems: a one-dimensional system of diffusive hard particles and a three-dimensional glass-former of nearly-hard repulsive particles. The dynamic transitions are observed using ensembles of trajectories biased with respect to their dynamic activity, biasing to greater or lower activities than equilibrium allows us to sample different dynamic phases. We perform finite-size scaling of the transitions with respect to sys- tem size and observation time, and compare them to first-order phase tran- sitions. The two ensembles are not equivalent in the one-dimensional model. We compare our results to analytic predictions for diffusive systems in both the active and inactive phases, there are structural signatures for both dy- namic regimes. The active phases show hyperuniform ordering and the inac- tive regimes show jamming behaviour, local jamming in the constant-volume ensemble is achieved through phase separation. In the three-dimensional sys- tem we observe a dynamic transition to a glassy inactive phase, there is no obvious structural change and the structural relaxation time increases sig- nificantly. We take configurations from the active and inactive phases and subject them to a jamming protocol in order to compare the final density of the jammed packings. Previous work shows that the inactive phase of glass-forming systems have a different distribution of vibrational modes and a higher compressibility, this suggests that the jamming behaviour should differ between the two phases. We show that jammed packings generated from inactive configurations are denser than those generated from active configurations.
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Gaunt, Adam P. "Towards micro-imaging with dissolution dynamic nuclear polarisation." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51219/.
Повний текст джерелаАнотація:
Nuclear magnetic resonance (NMR) of small samples and nuclei with a low gyromagnetic ratio is intrinsically insensitive due to the received signal dependence on Boltzmann's statistics. This insensitivity can be partially overcome through the application of hyper polarisation techniques such as Dissolution Dynamic Nuclear Polarisation (D-DNP). It is hoped that the hyper polarised 13C signal received from labelled small molecules could facilitate imaging of metabolic and transporter processes in biological systems. In order to realise this, appropriate molecules and experimental hardware must be used. A detailed description of the experimental set-up used for carrying out DDNP is given and the system is characterised. the advantageous use of a dual iso-centre magnet system is elucidated with optimisation of acquisition of fast relaxing molecules. such a system allows for interrogation of processes with short relaxation times, not possible with traditional, stand-alone polarisers. To acquire the maximum amount of hyper-polarised 13C signal in an imaging experiment, parallel acquisition techniques have been implemented and the hardware designed with such goals in mind. Multiple coils have been used to allow accelerated image acquisition. As such this work has validated the SENSE algorithm for artefact free, image reconstruction on the micro-scale. These techniques require an array of coils which add to the complexity of the design of the probehead. Decoupling methods and array coil construction must be considered the methods used to ensure well isolated coils, such as geometric decoupling, are presented. The novel fabrication and implementation of micro-coils for imaging and spectroscopy of nL scale samples is presented this will help facilitate the acquisition of images showing metabolic processes in active transport in cells. By placing the coils close to the sample it is possible to gain sensitivity relative to the mass of the sample in question. To achieve signal detection on the order of nL a novel, exible micro-coil array has been fabricated and the results of NMR experiments carried out on both protons and 13C are shown. This is the final stage before integrating the coils with the D-DNP system. The acquisition of 13C signal with the micro-coils displays optimal electronic characteristics when compared with other detectors presented in the literature. The final goal of the work is to produce a system that is capable of micro imaging in small biological samples such as the Xenopus Oocyte with a view to monitoring metabolic processes and transportation without the need for the use of the large fluorescing proteins (GFP's) that have been used in previous work (1). The need for GFP's attached to metabolites results in the measured data being non-physical as the fluorescing protein is often much larger than the molecule being transported. It is hoped that the use of hyperpolarised small molecules (such as pyruvic acid) may be able to remove this need for GFP's in the study of metabolite transportation.
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Müller, Alexandra [Verfasser]. "Dynamic Refinement and Coarsening for the Smoothed Particle Hydrodynamics Method / Alexandra Müller." Aachen : Shaker, 2017. http://d-nb.info/1124366555/34.
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Rakitianskaia, A. S. (Anastassia Sergeevna). "Using particle swarm optimisation to train feedforward neural networks in dynamic environments." Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/28618.
Повний текст джерелаАнотація:
The feedforward neural network (NN) is a mathematical model capable of representing any non-linear relationship between input and output data. It has been succesfully applied to a wide variety of classification and function approximation problems. Various neural network training algorithms were developed, including the particle swarm optimiser (PSO), which was shown to outperform the standard back propagation training algorithm on a selection of problems. However, it was usually assumed that the environment in which a NN operates is static. Such an assumption is often not valid for real life problems, and the training algorithms have to be adapted accordingly. Various dynamic versions of the PSO have already been developed. This work investigates the applicability of dynamic PSO algorithms to NN training in dynamic environments, and compares the performance of dynamic PSO algorithms to the performance of back propagation. Three popular dynamic PSO variants are considered. The extent of adaptive properties of back propagation and dynamic PSO under different kinds of dynamic environments is determined. Dynamic PSO is shown to be a viable alternative to back propagation, especially under the environments exhibiting infrequent gradual changes. Copyright 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Rakitianskaia, A 2011, Using particle swarm optimisation to train feedforward neural networks in dynamic environments, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02132012-233212 / > C12/4/406/gmDissertation (MSc)--University of Pretoria, 2011.
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Bilgen, Suheyla. "Dynamic pressure in particle accelerators : experimental measurements and simulation for the LHC." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP020.
Повний текст джерелаАнотація:
L’obtention de très faible pression (UHV) est une condition essentielle pour les accélérateurs de particules de haute énergie et de hautes performances. Par conséquent, la compréhension de l'évolution de la pression dynamique pendant le fonctionnement des accélérateurs est fondamentale afin de trouver des solutions qui permettent de minimiser les hausses de pression induites par de multiples phénomènes présents dans les lignes faisceaux. Pour le LHC, l'apparition d'instabilités peut être due à la succession de plusieurs processus. Tout d’abord, le faisceau de protons de haute intensité ionise le gaz résiduel, produisant des ions positifs (principalement H₂⁺ et CO⁺) ainsi que des électrons qui sont accélérés et qui impactent la paroi en cuivre des tubes de faisceaux. Ensuite, ces interactions induisent : (i) une désorption des gaz absorbés sur les parois, conduisant à des élévations de pression ; (ii) la création de particules secondaires (ions et électrons). Dans ce dernier cas, la production d'électrons secondaires entraîne, par effet d’avalanche, la formation de nuages d’électrons, dont la limitation est l'un des enjeux majeurs de l'anneau de stockage du LHC. Ces nuages génèrent des montées de pression et des dépôts de chaleur sur les parois du collisionneur pouvant conduire à des « quench » d’aimants supraconducteurs. Tous ces phénomènes limitent l'intensité maximale et augmentent l’émittance des faisceaux et donc la luminosité ultime atteignable dans un accélérateur de protons. Ce travail de thèse a pour but d’étudier certains phénomènes fondamentaux qui contrôlent la pression dynamique dans le LHC, à savoir les effets induits par les électrons et les ions, d’une part, et l'influence de la chimie de surface du cuivre constituant les écrans faisceaux, d’autre part. Dans un premier temps, les courants d’électrons et d’ions ainsi que la pression ont été mesurés in situ dans le Secteur Pilote Vide (VPS) situé sur l'anneau du LHC pendant la deuxième période d’exploitation du collisionneur. En analysant ces résultats, une quantité d’ion plus importante que prévu a été détectée et la relation entre les électrons, les ions et les variations de pression a été étudiée. D’autre part, la désorption stimulée par les ions a été mesurée au laboratoire au CERN en utilisant un bâti expérimental dédié. L'influence de la nature, de la masse et de l'énergie des ions incidents interagissant avec les surfaces sur les rendements de désorption ionique a été discutée. De plus, des analyses approfondies de la surface de cuivre constituant l'écran faisceau ont été réalisées dans le laboratoire IJCLab pour identifier le rôle joué par la chimie de surface du cuivre sur le rendement d’émission électronique, les processus de conditionnement de surface et la désorption de gaz stimulée. Le rôle fondamental de composés chimiques sur la surface (contaminants, présence de carbone et d'oxydes natifs) sur le rendement de production des électrons secondaires a été mis en évidence. Enfin, nous avons proposé un code de simulation permettant de prédire les profils de pression dans les chambres à vide des accélérateurs de particules ainsi que leur évolution temporelle. Ce nouveau code de simulation appelé DYVACS (DYnamic VACuum Simulation) est une amélioration du code VASCO développé par le CERN. Il a été appliqué pour simuler la pression dynamique dans le VPS. L'évolution du nuage d'électrons a été implémentée dans le code via des « maps » permettant de calculer l'évolution de la densité des nuages d'électrons. L'ionisation du gaz résiduel par les électrons a également été prise en compte. Finalement, les résultats obtenus avec DYVACS ont été comparés aux mesures de pression enregistrées dans le LHC. Les résultats obtenus à l’issu de ces travaux de thèse, ainsi que les développements expérimentaux et de simulation réalisés, pourront permettre l’étude de la stabilité du vide de futurs accélérateurs de particules tels que HL-LHC ou FCC(ee et hh)Ultra-High Vacuum is an essential requirement to achieve design performances and high luminosities in high-energy particle colliders. Consequently, the understanding of the dynamic pressure evolution during accelerator operation is fundamental to provide solutions to mitigate pressure rises induced by multiple-effects occurring in the vacuum chambers and leading to beam instabilities. For the LHC, the appearance of instabilities may be due to the succession of several phenomena. First, the high intensity proton beams ionize the residual gas producing positive ions (mainly H₂⁺ or CO⁺) as well as accelerated electrons which impinge the copper wall of the beam pipe. Then, these interactions induce: (i) the desorption of gases adsorbed on the surfaces leading to pressure rises; (ii) the creation of secondary particles (ions, electrons). In this latter case, the production of secondary electrons leads to the so-called “Electron Cloud” build-up by multipacting effect, the mitigation of which being one of the major challenges of the LHC storage ring. Electron clouds generate beam instabilities, pressure rises and heat loads on the walls of beam pipe and can lead to “quench” of the superconducting magnets. All these phenomena limit the maximum intensity of the beams and thus the ultimate luminosity achievable in a proton accelerator. This work aims to investigate some fundamental phenomena which drive the dynamic pressure in the LHC, namely the effects induced by electrons and ions interacting with the copper surface of the beam screens on the one hand and the influence of the surface chemistry of copper on the other hand. First, in-situ measurements were performed. Electron and ion currents as well as pressure were recorded in situ in the Vacuum Pilot Sector (VPS) located on the LHC ring during the RUN II. By analyzing the results, more ions than expected were detected and the interplay between electrons, ions and pressure changes was investigated. Then, the ion-stimulated desorption was studied, using a devoted experimental set-up at the CERN vacuum Lab. The influence of the nature, mass, and energy of the incident ions interacting with the copper surface on the ion-desorption yields was discussed. In addition, extensive surface analyses were performed in the IJCLab laboratory to identify the role played by the surface chemistry on the electron emission yield, surface conditioning processes and the stimulated gas desorption. The fundamental role of the surface chemical components (contaminants, presence of carbon and native oxide layers) on the secondary electron yield was evidenced. Finally, we proposed a simulation code allowing to predict the pressure profiles in the vacuum chambers of particle accelerators as well as their evolution under dynamic conditions (i.e. as a function of time). This new simulation code called DYVACS (DYnamic VACuum Simulation) is an upgrade of the VASCO code developed at CERN. It was applied to simulate the dynamic pressure in the VPS when proton beams circulate into the ring. The electron cloud build-up was implemented in the code via electron cloud maps. The ionization of the residual gas by electrons was also considered. Results obtained with the DYVACS code are compared to pressure measurements recorded during typical fills for physics and a good agreement is obtained. This PhD study has provided interesting results and has allowed the development of new experimental and simulation tools that will be useful for further investigations on the vacuum stability of future particle accelerators such as HL-LHC or FCC (ee and hh)
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Helbig, Marde. "Solving dynamic multi-objective optimisation problems using vector evaluated particle swarm optimisation." Thesis, University of Pretoria, 2012. http://hdl.handle.net/2263/28161.
Повний текст джерелаАнотація:
Most optimisation problems in everyday life are not static in nature, have multiple objectives and at least two of the objectives are in conflict with one another. However, most research focusses on either static multi-objective optimisation (MOO) or dynamic singleobjective optimisation (DSOO). Furthermore, most research on dynamic multi-objective optimisation (DMOO) focusses on evolutionary algorithms (EAs) and only a few particle swarm optimisation (PSO) algorithms exist. This thesis proposes a multi-swarm PSO algorithm, dynamic Vector Evaluated Particle Swarm Optimisation (DVEPSO), to solve dynamic multi-objective optimisation problems (DMOOPs). In order to determine whether an algorithm solves DMOO efficiently, functions are required that resembles real world DMOOPs, called benchmark functions, as well as functions that quantify the performance of the algorithm, called performance measures. However, one major problem in the field of DMOO is a lack of standard benchmark functions and performance measures. To address this problem, an overview is provided from the current literature and shortcomings of current DMOO benchmark functions and performance measures are discussed. In addition, new DMOOPs are introduced to address the identified shortcomings of current benchmark functions. Guides guide the optimisation process of DVEPSO. Therefore, various guide update approaches are investigated. Furthermore, a sensitivity analysis of DVEPSO is conducted to determine the influence of various parameters on the performance of DVEPSO. The investigated parameters include approaches to manage boundary constraint violations, approaches to share knowledge between the sub-swarms and responses to changes in the environment that are applied to either the particles of the sub-swarms or the non-dominated solutions stored in the archive. From these experiments the best DVEPSO configuration is determined and compared against four state-of-the-art DMOO algorithms.Thesis (PhD)--University of Pretoria, 2012.
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McGeorge-Henderson, Ben P. "Novel acquisition strategies for dissolution dynamic nuclear polarisation." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43266/.
Повний текст джерелаАнотація:
Dynamic Nuclear Polarisation (DNP) produced molecules with spin polarisation levels that are up to three orders of magnitude larger than their thermal equilibrium values. Most DNP mechanisms work at temperatures of 2 K and lower, meaning that the sample is stored in the solid-state. Combining DNP with a rapid temper- ature jump to room temperature allows liquid-state NMR analysis with a signal that is ve orders of magnitude higher than observed with thermal polarisation. However, the information obtained during a dissolution experiment is limited by the intrinsic liquid-state longitudinal relaxation of the spins of interest. is thesis looks to increase the information acquired in a number of ways. First, by devel- oping a new dissolution system for the dual iso-centre magnet it was possible to reproducibly perform enhanced NMR acquisition 600 ms following sample disso- lution. is has allowed the observation of hyperpolarised 13C spins with T1 times as low as 200 ms. Complimentary information can be obtained following sample dissolution by observing multiple spin species simultaneously. 13C and 15N spins are both polarised by microwave irradiation of the same frequency, so both can be analysed during a single dissolution DNP experiment. A novel probe has been used that contains six individual 13C microcoils. ese coils are separated in space and operate independently. is probe, in conjunction with dissolution DNP, can be used for observing dynamic molecular information on the time scale of 200 ms, however with further development this time scale should drop to less than 100 ms while maintaining a required minimum spectral resolution. Initial tests have been performed with both thermally polarised and hyperpolarised samples.
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Zhang, Fangli. "A particle-set distributed hydrological model for the dynamic simulation of surface runoff." HKBU Institutional Repository, 2017. https://repository.hkbu.edu.hk/etd_oa/472.
Повний текст джерелаАнотація:
1.1\xThis study proposed a particle-set distributed hydrological model for the dynamic simulation of rainfall-runoff process. With the supports of remote sensing, GIS, terrain analysis and distributed computing techniques, a representation-simplified and physically-based high-performance watershed framework has been developed. It simplifies the underlying watershed with a flow path network model, and represents the moving surface flow with independent runoff particles.;1.2\xThe original idea was to investigate a real-time modeling system for the space-time dynamics of increasingly frequent extreme rainfall events. Short-term heavy rains may cause further damages by spawning floods and landslides. It is quite essential to understand how the rainfall water moves across the watershed surface as early as possible. A modelling system with high-performance in simulation efficiency and space-time prediction accuracy would be very desirable.;1.3\xWatershed modeling is the primary way to explore the hydrological cycle at a local scale. Existing models are classified as empirical lumped, conceptual semi-distributed and physically-based distributed models. The first two types of models have focused more on predicting outlet discharges rather than estimating spatiotemporal flow dynamics. The application of physically-based models has always been hampered by some common shortcomings like over-parameterization, inflexibility and computational burden. With the increasing support from terrain analysis and parallel computing techniques, a number of previous studies have made some efforts to improve the performance in dynamic and real-time simulation. However, research gaps still exist in realistic representation, physical description and real-time simulation.;1.4\xThis study, therefore, developed the particle-set modeling system on the basis of flow path network model. This one-dimensional topological structure was created beforehand to represent the three-dimensional watershed, and a series of particle beams were dynamically generated to simulate the surface flow. Under the control of flow velocities, these runoff particles would keep on moving along with the flow paths, which can represent the spatial distributions of surface water in time.;1.5\xTo validate the proposed particle-set framework, a prototype of particle-set system was implemented by programming methods with the assistance of third-party platforms. Three experiments were undertaken to respectively evaluate the performance in prediction accuracy, simulation efficiency and parameter sensitivity. More specifically, a total of 10 rainfall events and up to 128 computer processors were tested. In addition, the influences of underlying spatial scale and source sampling density on hydrological responses were explored with comparative tests.;1.6\xThe accuracy validation comes in two parts, the representation loss in terrain analysis, and the discharge error in hydrological modeling. The experimental results indicate that the TIN-based flow path network has maintained the terrain features at a very high level with much less data storage, and the particle-set framework has achieved quite acceptable predictions of outlet discharges. Besides, the efficiency evaluation concerns with two aspects, parallel portion and parallel efficiency. The speed-up results indicate that about 99% of the computational workloads can be computed in parallel, and the particle-based scheme can achieve almost the ideal parallel efficiency. In addition, the sensitivity test focuses also on two parameters, underlying spatial scale and source sampling density. The preliminary results show that the particle-set model has shown a good reliability and stability as scale gets coarser or density becomes sparser.;1.7\xThis study will contribute to the understanding of short-term rainfall-runoff events at a basin scale. The particle-set distributed hydrological model has been proven to provide real-time spatio-temporal dynamics of surface flow. Further studies would still be required to apply it to real world scenarios.;1.8\xKeywords: terrain analysis, watershed hydrology, rainfall-runoff process, flow path network, particle system, parallel computing
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Abbaspour-Fard, Mohammad Hossein. "Discrete element modelling of the dynamic behaviour of non-spherical particulate materials." Thesis, University of Newcastle Upon Tyne, 2000. http://hdl.handle.net/10443/970.
Повний текст джерелаАнотація:
A numerical model based on the discrete element (DE) method, for modelling the flow of irregularly shaped, smooth-surfaced particles in a 3-D system is presented. An existing DE program for modelling the contact between spherical particles in periodic space (without real walls or boundaries) was modified to model non-spherical particles in a system with containing walls. The new model was validated against analytical calculations of single particle movements and also experimentally against data from physical experiments using synthetic non-spherical particles at both a particle and bulk scale. It was then used to study the effect of particle shape on the flow behaviour of assemblies of particles with various aspect ratios discharging from a flat-bottomed hopper. The particles were modelled using the Multi-Sphere Method (MSM) which is based on the CSG (Constructive Solid Geometry) technique for construction of complex solids by combining primitive shapes. In this method particle geometry is approximated using overlapping spheres of arbitrary diameter which are fixed in position relative to each other. The contact mechanics and contact detection method are the same as those used for spheres, except that translation and rotation of element spheres are calculated with respect to the motion of the whole particle. Numerical simulations of packing and flow of particles from a flat-bottomed hopper with a range of aspect ratios were performed to investigate the effect of particle shape on packing and flow behaviour of a particulate assembly. It was found that the particle shape influenced both bed structure and flow characteristics such as flow pattern, shear band strength and the occurrence of bridging. The flow of the bed of spherical particles was smoother than the flow of beds of elongated particles in which flow was fluctuating and there was more resistance to shear.
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Blom, Andrej. "Comparing FumeFx with Autodesk Maya Dynamic System." Thesis, University of Gävle, Department of Mathematics, Natural and Computer Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-610.
Повний текст джерелаАнотація:
One of the main problem areas within computer graphics is simulating natural phenomena’s, working with fluid solvers, and particle systems. In the special effects industry, there is a demand for mimicking appearance of common special effect such as fire, smoke, and water. Autodesk Maya and FumeFx are used for exploring those methods in creating smoke and fire simulations and implementing those into a
large dynamic system, while researching the possibility to efficiently control and modify an entire dynamic system on a per object level. Final production renders results are from both Maya and FumeFx.
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Lavis, Benjamin Mark Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Spatially reconfigurable and non-parametric representation of dynamic bayesian beliefs." Publisher:University of New South Wales. Mechanical & Manufacturing Engineering, 2008. http://handle.unsw.edu.au/1959.4/41468.
Повний текст джерелаАнотація:
This thesis presents a means for representing and computing beliefs in the form of arbitrary probability density functions with a guarantee for the ongoing validity of such beliefs over indefinte time frames. The foremost aspect of this proposal is the introduction of a general, theoretical, solution to the guaranteed state estimation problem from within the recursive Bayesian estimation framework. The solution presented here determines the minimum space required, at each stage of the estimation process, to represent the belief with limited, or no, loss of information. Beyond this purely theoretical aspect, a number of numerical techniques, capable of determining the required space and performing the appropriate spatial reconfiguration, whilst also computing and representing the belief functions, are developed. This includes a new, hybrid particle-element approach to recursive Bayesian estimation. The advantage of spatial reconfiguration as presented here is that it ensures that the belief functions consider all plausible states of the target system, without altering the recursive Bayesian estimation equations used to form those beliefs. Furthermore, spatial reconfiguration as proposed in this dissertation enhances the estimation process since it allows computational resources to be concentrated on only those states considered plausible. Autonomous maritime search and rescue is used as a focus application throughout this dissertation since the searching-and-tracking requirements of the problem involve uncertainty, the use of arbitrary belief functions and dynamic target systems. Nevertheless, the theoretical development in this dissertation has been kept general and independent of an application, and as such the theory and techniques presented here may be applied to any problem involving dynamic Bayesian beliefs. A number of numerical experiments and simulations show the efficacy of the proposed spatially reconfigurable representations, not only in ensuring the validity of the belief functions over indefinite time frames, but also in reducing computation time and improving the accuracy of function approximation. Improvements of an order of magnitude were achieved when compared with traditional, spatially static representations.
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Wisniewski, Daniel. "Simulations of Dynamic Nuclear Polarization pathways in large spin ensembles." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39045/.
Повний текст джерелаАнотація:
Dynamic Nuclear Polarization (DNP) is a method for signal enhancement in NMR, with numerous applications ranging from medicine to spectroscopy. Despite the success of applications of DNP, the understanding of the underlying theory is still limited. Much of the work on the theory of DNP has been carried out on small spin systems; this is a restriction due to the exponential growth of the Liouville space in quantum simulations. In the work described in this thesis, a methodology is presented by which this exponential scaling can be circumvented. This is done by mathematically projecting the DNP dynamics at resonance onto the Zeeman subspace of the density operator. This has successfully been carried out for the solid effect, cross effect and recently for the Overhauser effect in the solid state (see appendix A.4). The results are incoherent state-dependent dynamics, resembling classical behaviour. Such form of effective dynamics allows the use of kinetic Monte Carlo algorithms to simulate polarization dynamics of very large spin systems; orders of magnitude larger than has previously been possible. We verify the accuracy of the mathematical treatment of SE-DNP and CE-DNP, and illustrate the insight large spin-system simulations provide into the mechanism of DNP. For SE-DNP the mechanism of polarization to the bulk of spin systems is determined to be spin diffusion, and we carried out studies into the efficiency and performance of radicals, with an outlook on radical design. We also show that the Zeeman projection can be applied to heteronuclear spin systems if the nuclear species are close in frequency, and we present a formalism for simulating C-13 nuclear spin systems based on a linear rate approach, enabling simulations of thousands of spins in a matter of minutes. A study into the scaling of the kinetic Monte Carlo algorithm error, and the simulation run time, with respect to an increasing number of spins is also presented. For CE-DNP the error analysis led to establishing a parameter regime in which the effective dynamics are accurate. We show that spin diffusion is the mechanism of transfer of polarization to bulk nuclei. We also show how the effective rates for CE-DNP can be used to understand the efficiency of bi-radicals, point to optimisation possibilities, and hold a potential to aid in bi-radical design. We finally show large scale simulations for CE-DNP bi-radical systems with improved parameters; leading to very rapid build-up of nuclear polarization.
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Currie, T. D. G. "Application of particle image velocimetry to the investigation of gas dynamic flow in pipes." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411093.
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Chao, Chien-Wei. "An Improved Dynamic Particle Packing Model for Prediction of the Microstructure in Porous Electrodes." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5632.
Повний текст джерелаАнотація:
The goal of this work is to develop a model to predict the microstructure of Li-ion batteries, specifically focusing on the cathode component of the batteries. This kind of model has the potential to assist researchers and battery manufacturers who are trying to optimize the capacity, cycle life, and safety of batteries. Two dynamic particle packing (DPP) microstructure models were developed in this work. The first is the DPP1 model, which simulates the final or dried electrode structure by moving spherical particles under periodic boundaries using Newton's laws of motion. The experience derived from developing DPP1 model was beneficial in making the final model, called DPP2. DPP2 is an improved version of DPP1 that includes solvent effects and is used to simulate the slurry-coating, drying, and calendering processes. Two type of properties were used to validate the DPP1 and DPP2 models in this work, although not every property was used with the DPP1 model. First are the structural properties, which include volume fraction, and electronic and ionic conductivities. Experimental structural properties were determined by analyzing 2D cross sectional images of the battery cathodes. These images were taken through focused ion beam (FIB) planarization and scanning electron microscopy (SEM). The second category are the mechanical properties, which include film elasticity and slurry viscosity. These properties were measured through experiments executed by our group. The DPP2 model was divided into two submodels : active-free and active-composite. The 2D cross sectional images of the simulated structure of the models have a similar particle arrangements as the experimental structures. The submodels show reasonable agreement with the experimental values for liquid and solid mass density, shrink ratio, and elasticity. For the viscosity, both models show shear-thinning behavior, which is a characteristic of slurries. The volume fractions of the simulated structures of the active-free and active-composite models have better agreement with the experimental values, which is also reflected in the 2D cross sectional images of the structure.
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Pérez, Linde Angel Joaquin. "Application of cross polarisation techniques to dynamic nuclear polarisation dissolution experiments." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11417/.
Повний текст джерелаАнотація:
Dynamic Nuclear Polarisation (DNP) was suggested for the first time by Albert Overhauser in early 1950s. In DNP experiments the polarisation from electrons can be transferred to nuclei by irradiation of the electron resonance line. There are several possible mechanisms for polarisation transfer that involve DNP in solid state depending on the width of the electron line in respect to the nuclear Larmor frequency. In this thesis, the efficiency of TEMPO radical (2,2,6,6 tetramethilpiperidine, 1 oxyl) for DNP is demonstrated in combination with nuclear polarisation transfer techniques for dissolution experiments. New cryo-probes were developed for DNP and cross polarisation (CP) for operation temperatures as low as 1.5 K. Two of them were designed for dissolution experiments. Some published sequences of nuclear polarisation transfer were tested at low temperatures and compared. Novel sequences were implemented for efficient CP in organic samples doped with TEMPO to allow for a consecutive dissolution experiment. The combination of DNP with new CP sequences at low temperatures, achieved at least twice the 13C polarisation obtained with DNP and in a substantially shorter time (between 5 to 10 minutes) in samples doped with TEMPO. The polarisation levels obtained in samples of [13C-1] labelled Na acetate in a few minutes was comparable to the polarisation obtained with trityl radicals in a few hours. In addition, another strategy was investigated by using brute force polarisation as a mechanism for achieving large levels of nuclear spin order. The problem presented by this method is the long relaxation time required to obtain the thermal equilibrium polarisation. By doping with lanthanides samples of [13C-1] labelled Na acetate in 1:1 glycerol-water, it was possible to obtain thermal equilibrium for a 13C spin system in less than one hour.
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Miguel, López María del Carmen. "Dynamic Properties of Magnetic Colloidal Particles and Holes." Doctoral thesis, Universitat de Barcelona, 1985. http://hdl.handle.net/10803/667638.
Повний текст джерелаАнотація:
Our main goal is to study certain aspects of the dynamics of fluids with magnetic particles in suspension, based on their promising practical applications as new materials as welI as on its fundamental scientific interest.
In the introduction we brief the reader on the most essential properties of the system. We have characterized the monodomain magnetic particles and the time scales inherent to magnetic fluids. Having introduced the rotational diffusion equation as the most convenient tool to take into account the different mechanism inftuencing the dynamics of the particles, we have also proposed a fruitful approach for solving it in any general situation. We have also highlighted the macroscopic properties of the magnetic fluid treated now as a continuous medium and showed up the different phenomena associated with the lack of stability in the system.
In Chapter I we concentrate on two limit cases whose analysis is easier but very illustrative. The first part of the chapter is devoted to the study of a suspension of rigid dipoles, in which the magnetic moments are rigidly attached to the body of the particles themselves. In these conditions, if we apply an external magnetic field both the magnetic moment and the particle move together so that the magnetic torque acting upon it becomes zero. Thermal fluctuations tends to disrupt this order, and it turns out that, for instance, that the effective viscosity of the suspension depends on the dimensionless parameter comparing magnetic and thermal energies. In the second part we consider magnetic materials with finite anisotropy energy at high magnetic fields. For such monodomain particles the magnetic moments rapidly orient along the direction of the external field, and then as a second step the mechanical rotation of the particles takes place. In this case, the effective viscosity of the suspension is a function of the magnetic anisotropy constant of the material, of the volume of the particles as well as the thermal energy. Our results are compared to experimental measurements.
The second chapter is concerned with the determination of the viscosity and of some magnetic and optical properties of magnetic fluids in the whole range of possible experimental situations. The magnetic moments and the particles inside the liquid reorient separately but their dynamics are coupled thus giving rise to a more intricate relaxation process. We have compared part of our results with available experimental data for different ferrofluids showing quite a good agreement.
In Chapter III we joint to our discussion of magnetic fluids the presence of nonmagnetic particles of micrometer size and study their motion through the ferrofluid. The ferrofluid is considered now as a continuous medium with new transport coefficients already determined in the previous sections. Under the action of a rotating external magnetic field, we study the rotational motion of the nonmagnetic particles and compare our expressions to sorne measurements carried out in these composite systems. In this chapter we are also con cerned with the characterization of the hydrodynamic interactions among these particles in a carrier ferrofluid.
Chapter IV is intended as a brief introduction to the multiple problems which arise when one handle the aggregation phenomena which may take place in these systerns. We study the kinetics of the forrnation of the aggregates by rneans of the Smoluchowski theory of coagulation in colloids. But we account for hydrodynarnic interactions which are not usually considered when studying such process and that gives rise to sorne corrections for high concentrations of particles. In addition, the rheology of the chains that are usually observed in systerns with dipolar interactions is given for a rather simplified situation in order to elucidate the effects of the dipolar magnetic interactions.
Finally, we sum up our main conclusions and indicate some of the perspectives stimulated by the contents of this monograph and in which we plan to pursue work in the near future.A lo largo de esta monografía nos hemos ocupado del estudio de sistemas fluidos, tanto con monodominios magnéticos como con dos tipos distintos de partículas, magnéticas y no magnéticas, en dispersión en un líquido newtoniano en situaciones fuera del equilibrio. El comportamiento de estos sistemas se ve influenciado en gran medida por la presencia de un campo magnético externo, lo que da lugar a nuevos fenómenos que han sido el fundamento de muchas aplicaciones prácticas. Sin embargo, esta influencia depende de los diferentes procesos de relajación que tienen lugar dentro las partículas, con respecto a sus ejes cristalinos, así como fuera de ellas, con respecto al fluido portador. Hemos descrito cuáles son estos procesos y obtenido la dependencia con respecto de los parámetros que describen las partículas y el fluido, de algunos coeficientes que caracterizan las propiedades reológicas, magnéticas y ópticas de la suspensión coloidal.
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Hobbs, Andrew M. "Design and optimization of a vortex particle separator for a hot mix asphalt plant using computational fluid dynamics." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04192004-101304/unrestricted/hobbs%5Fandrew%5Fm%5F200312%5Fms.pdf.
Повний текст джерела
42
MANFREDOTTI, CRISTINA ELENA. "Modeling and inference with relational dynamic bayesian networks." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/7829.
Повний текст джерелаАнотація:
Many domains in the real world are richly structured, containing a diverse set of agents characterized by different set of features and related to each other in a variety of ways. Moreover, uncertainty both on the objects observations and on their relations can be present. This is the case of many problems as, for example, multi-target tracking, activity recognition, automatic surveillance and traffic monitoring.
The common ground of these types of problems is the necessity of recognizing and understanding the scene, the activities that are going on, who are the actors, their role and estimate their positions. When the environment is particularly complex, including several distinct entities
whose behaviors might be correlated, automated reasoning becomes particularly challenging. Even in cases where humans can easily recognize activities, current computer programs fail because they lack of commonsense reasoning, and because the current limitation of automated reasoning systems. As a result surveillance supervision is so far mostly delegated to humans. The explicit representation of the interconnected behaviors of agents can provide better models for capturing key elements of the activities in the scene. In this Thesis we propose the use of relations to model particular correlations between agents features, aimed at improving the inference task. We propose the use of relational Dynamic Bayesian Networks, an extension of Dynamic Bayesian Networks with First Order Logic, to represent the dependencies between an agent’s attributes, the scene’s elements and the evolution of state variables over time. In this way, we can combine the advantages of First Order Logic (that can compactly represent structured environments), with those of probabilistic models (that provide a mathematically sound framework for inference in face of uncertainty).
In particular, we investigate the use of Relational Dynamic Bayesian Networks to represent the dependencies between the agents’ behaviors in the context of multi-agents tracking and activity recognition. We propose a new formulation of the transition model that accommodates for relations and present a filtering algorithm that extends the Particle Filter algorithm in order to directly track relations between the agents.
The explicit recognition of the relationships between interacting objects can improve the understanding of their dynamic domain. The inference algorithm we develop in this Thesis is able to take into account relations between interacting objects and we demonstrate with experiments
that the performance of our relational approach outperforms those of standard non-relational methods.
While the goal of emulating human-level inference on scene understanding is out of reach for the current state of the art, we believe that this work represents an important step towards better algorithms and models to provide inference in complex multi-agent systems.
Another advantage of our probabilistic model is its ability to make inference online, so that the appropriate cause of action can be taken when necessary (e.g., raise an alarm). This is an important requirement for the adoption of automatic surveillance systems in the real world, and avoid the common problems associated with human surveillance.
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Kim, Yeonsu. "Probabilistic Estimation of River Discharge Considering Channel Characteristics Uncertainty with Particle Filters." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180482.
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PANTALEI, CLAUDIA. "Single-particle dynamics of helium mixtures and 4He in nanometric confinement." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/473.
Повний текст джерелаАнотація:
Scopo di questa tesi e' lo studio, tramite Deep Inelastic Neutron Scattering, della
dinamica microscopica di due differenti sistemi di elio, a bassa temperatura (circa 2
K): una miscela isotopica (nella fase fluida e vicino al punto di melting) e 4He in in
confinamento nanometrico.
L'interesse per l'elio, gia' dai primi decenni del `900, nasce dalla sua unica proprieta':
e' l'unico elemento in natura a non avere una fase solida allo zero assoluto. A basse
temperature, quindi, presenta effetti quantistici, normalmente trascurabili in altri
sistemi fisici, che nelle stesse condizioni solidificano. l'elio e' quindi l'unico banco di
prova per i modelli teorici quantistici, in particolare per lo studio di bosoni e fermioni
interagenti.
In questo contesto, molti esperimenti sono stati effettuati sull'elio, sia nella fase liquida che solida. Misure su 3He e 4He hanno mostrato che l'energia cinetica dei liquidi
puri dipende dalla densita' del sistema, crescendo con una diminuzione del volume
molare. D'altra parte, la dinamica microscopica delle miscele mostra un differente
comportamento rispetto al 3He e 4He puri: l'energia cinetica media dell'isotopo piu'
leggero, a volumi molari maggiori di 25cm3/mole, sembra essere indipendente dal
volume molare e dalla concentrazione. Questo andamento potrebbe essere spiegato
da effetti quantistici, come gli effetti di scambio. Nella prima parte del presente
lavoro si e' investigata la dinamica delle miscele per volumi molari tra 22cm3/mole
e 25cm3/mole, e gli esperimenti compiuti hanno mostrato che in questo range di
volumi molari l'energia cinetica media degli atomi di 3He risulta dipendente dal volume molare, aumentando fino ad avere un valore corrispondente a quello del 3He
puro.
Recentemente sono state compiute anche misure per studiare l'influenza di un confinamento sull'elio. Esperimenti su 4He, adsorbito in superfici piane o substrati
porosi, hanno rivelato un elevato aumento nel valore dell'energia cinetica. Questo
comportamento e' stato attribuito alla localizzazione degli atomi di He dovuta al
potenziale di interazione He-substrato, che influenza fortemente i primi due o tre layers. Questi tipi di effetti possono essere studiati confinando 4He in pori cilindrici con
differenti diametri dei pori. Scopo della seconda parte di questa tesi e' stata appunto
quella di determinare l'energia cinetica media degli atomi di 4He adsorbiti in sistemi
nanoporosi a geometria cilindrica (Xerogel) con due diametri medi dei pori, di 24ºA
160ºA, per valutare la dipendenza della dinamica a singola particella con la dimensione dei pori e con il tipo di geometria. Le misure sono state effettuate a T=2.5K, a
pressione di vapor saturo e con un riempimento dei pori del 95%. L'esperimento ha
mostrato che l'energia cinetica del 4He nei pori e' maggiore rispetto a quella del 4He
liquido nelle stesse condizioni. I risultati sono stati interpretati tramite un modello
teorico, secondo il quale gli atomi si posizionano in anelli concentrici, stratificando
layer per layer, e con un'energia cinetica dipendente dal rapporto tra il diametro del
poro e quello dell'atomo di elio.The aim of this thesis work is the study, by means of Deep Inelastic Neutron Scatter- ing, of the microscopic dynamics of two different helium systems at low temperature (T=2K): an isotopic helium mixture (in the fluid phase and near the melting point) and a system of 4He in nanometric confinement. The interest in the helium, from the first decades of 1900, is due to its unique features: it is the only element in nature that doesn't have a solid phase at absolute zero. Thus, at low temperatures it presents quantum effects, usually negligible in other physical systems that in this condition crystallise. The helium is thus the unique test-bed for theoretical quantum models, in particular for studying the interacting boson (4He) and fermion (3He) systems. Moreover, if in 4He are added some atoms of 3He it is possible to derive important information about the interplay of these two statistics. In this context, several experiments on liquid and solid helium have been performed. Measurements on pure 3He and 4He have shown that the mean kinetic energy of pure liquids depends on the density of the system and increases decreasing the molar volume. On the other hand, the microscopic dynamics of helium mixtures reveals quite a different picture with respect to pure 3He and 4He: the mean kinetic energy of the light isotope, above a molar volume of 25cm3/mole, shows a remarkable independence from molar volume and concentration. This behaviour could be explained by quantum effects, such as exchange effects. The first part of the present work deals with the experiments performed to investigate the dynamics of the mixtures from 22cm3/mole to 25cm3/mole and shows how, at these low molar volumes, the mean kinetic energy of 3He starts again to be strongly dependent on the molar volume, increasing until reaching, at 22.7cm3/mole, the corresponding value of pure helium. Recent measurements have been also performed to investigate the influence of confinement on helium. Experiments on 4He, adsorbed in flat surface or slit geometry porous substrates, have shown a large increase in helium mean kinetic energy. This has been attributed to the strong localisation effects induced by the helium-substrate interaction potential, which mainly influence the firsts two or three adsorbed layers. Such effects can be also investigated by confining 4He atoms in cylindrical pore geometries and by studying their dynamics as function of pore size. Aim of the second part of the thesis has been the determination of the single particle mean kinetic energy of 4He adsorbed in cylindrical silica nanopores (Xerogel) having two different pore diameters, namely, 24 ºAand 160 ºA, and to evaluate the dependence of single- particle dynamics on pore sizes, layer coverage, and confining system geometry. The measurements have been performed at a temperature of T=2.5K, saturated vapour pressure, and 95% volume filling. Significant changes in the values of the single particle mean kinetic energy are found: they are remarkably higher than the value of normal liquid 4He at the same conditions. The results are interpreted in terms of a model in which 4He atoms are arranged in concentric annuli along the cylindrical pore axis, growing layer-by-layer and with the mean kinetic energy mainly dependent on the ratio between the atomic diameter and the pore diameter.
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Stanhope, Austin. "A control architecture for dynamic execution of robot tasks trained in real-time using particle filters." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1472980.
Повний текст джерела
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Bohne, W., D. Polster, H. G. Ortlepp, D. Hilscher, and Guntram Pausch. "Particle identification in a wide dynamic range based on pulse-shape analysis with solid-state detectors." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-32464.
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Yin, Shu-Chen, and 殷淑貞. "Particle Swarm Optimization for Dynamic Clustering." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/34944364571653171729.
Повний текст джерелаАнотація:
碩士大同大學
資訊經營學系(所)
96
Data clustering, one of the major research technologies of data mining, is the process of grouping together similar multi-dimensional data vectors into a number of clusters. The process of data clustering needs to consider the number of clusters and the result of clusters. The natural number of clusters will influence the final clustering result. How to find the optimal number of clusters becomes an important issue. In this research, the author develops a novel dynamic clustering method, called Particle Swarm Optimization for Dynamic Clustering (PSODC), to cluster a dataset without setting the cluster number in advance. PSODC consists of two stages: evolution of optimal cluster numbers and data clustering in each sub-swarm representing a specified cluster number. In the first stage, the particles in a sub-swarm randomly move toward one of other sub-swarms based on the so-far-best cluster number. In the second stage, the particle swarm algorithm is used to cluster the data items. After that, a clustering validity index is applied to evaluate the clustering result of each sub-swarm. The above procedure is repeated until the clustering computation converges. To test the proposed algorithm and compare it with other dynamic clustering algorithms, thirteen test problems, including artificial data sets and UCI data sets, are used. The experimental results show that PSODC has outstanding performance in dynamic data clustering.
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Lin, Wei-Hsun. "Dynamic Characterization of Micro-Particle Systems." Thesis, 2016. https://thesis.library.caltech.edu/9054/55/lin_wei-hsun_2015_thesis.pdf.
Повний текст джерелаАнотація:
Ordered granular systems have been a subject of active research for decades. Due to their rich dynamic response and nonlinearity, ordered granular systems have been suggested for several applications, such as solitary wave focusing, acoustic signals manipulation, and vibration absorption. Most of the fundamental research performed on ordered granular systems has focused on macro-scale examples. However, most engineering applications require these systems to operate at much smaller scales. Very little is known about the response of micro-scale granular systems, primarily because of the difficulties in realizing reliable and quantitative experiments, which originate from the discrete nature of granular materials and their highly nonlinear inter-particle contact forces.
In this work, we investigate the physics of ordered micro-granular systems by designing an innovative experimental platform that allows us to assemble, excite, and characterize ordered micro-granular systems. This new experimental platform employs a laser system to deliver impulses with controlled momentum and incorporates non-contact measurement apparatuses to detect the particles’ displacement and velocity. We demonstrated the capability of the laser system to excite systems of dry (stainless steel particles of radius 150 micrometers) and wet (silica particles of radius 3.69 micrometers, immersed in fluid) micro-particles, after which we analyzed the stress propagation through these systems.
We derived the equations of motion governing the dynamic response of dry and wet particles on a substrate, which we then validated in experiments. We then measured the losses in these systems and characterized the collision and friction between two micro-particles. We studied wave propagation in one-dimensional dry chains of micro-particles as well as in two-dimensional colloidal systems immersed in fluid. We investigated the influence of defects to wave propagation in the one-dimensional systems. Finally, we characterized the wave-attenuation and its relation to the viscosity of the surrounding fluid and performed computer simulations to establish a model that captures the observed response.
The findings of the study offer the first systematic experimental and numerical analysis of wave propagation through ordered systems of micro-particles. The experimental system designed in this work provides the necessary tools for further fundamental studies of wave propagation in both granular and colloidal systems.
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李金紋. "A particle-based cloth dynamic behavior simulation." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/85022844194024505693.
Повний текст джерелаАнотація:
碩士國立成功大學
工程科學系
89
A mass-spring system was employed to model cloth. The mass particles, arranged in a rectilinear grid, are connected with three types of springs. These are 1)structural springs that connect nearest-neighbor particles along thread lines, 2)shear springs that connect nearest-neighbor particles along diagonals, and 3)bending springs that connect a particle with its second neighbor along thread lines. The dynamic behaviors of the springs are considered in order to simulate a cloth hanging from to points and a tablecloth draping over a table. Two-step method was used to handle collision detection and response problems. Several examples were given to show the results. It is shown that the proposed cloth simulation system is useful for simulating the dynamic behavior of cloth.
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Bellissima, Stefano. "Single particle dynamics in liquid systems." Doctoral thesis, 2017. http://hdl.handle.net/2158/1088719.
Повний текст джерелаАнотація:
The subject of this PhD work is the microscopic dynamics in fluids, that is, a study of the behavior of these fluids at an atomic level, where the ps and nm time and length scales, respectively, are involved. The objects of the analysis are fundamental space/time autocorrelation functions of microscopic
variables describing either collective or single-particle (self) properties of the system. In particular, in this thesis we exploited molecular dynamics simulation data-sets to describe the self dynamics of fluids belonging to different categories: Lennard-Jones (LJ) model fluids, semi-quantum fluids, liquid metals and hydrogen-bonded molecular liquids. A substantial step forward in the comprehension of single-particle dynamics has been possible i) by applying a new method, not attempted so far, for the description of self functions, which is based on the recently presented multi-exponential expansion theory that accounts for time autocorrelation functions in many-body Hamiltonian systems, and ii) by deepening the relationship between self and collective properties.