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Cooperation-induced Criticality in Neural Networks

Description: The human brain is considered to be the most complex and powerful information-processing device in the known universe. The fundamental concepts behind the physics of complex systems motivate scientists to investigate the human brain as a collective property emerging from the interaction of thousand agents. In this dissertation, I investigate the emergence of cooperation-induced properties in a system of interacting units. I demonstrate that the neural network of my research generates a series o… more
Date: August 2013
Creator: Zare, Marzieh
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Partner: UNT Libraries
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Emergence of Cooperation and Homeodynamics as a Result of Self Organized Temporal Criticality: From Biology to Physics

Description: This dissertation is an attempt at establishing a bridge between biology and physics leading naturally from the field of phase transitions in physics to the cooperative nature of living systems. We show that this aim can be realized by supplementing the current field of evolutionary game theory with a new form of self-organized temporal criticality. In the case of ordinary criticality, the units of a system choosing either cooperation or defection under the influence of the choices done by thei… more
Date: August 2018
Creator: Mahmoodi, Korosh
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Partner: UNT Libraries
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How Cooperative Systems Respond to External Forces

Description: Cooperative interactions permeate through nature, bringing about emergent behavior and complexity. Using a simple cooperative model, I illustrate the mean field dynamics that occur at the critical point of a second order phase transition in the framework of Langevin equations. Through this formalism I discuss the response, both linear and nonlinear, to external forces. Emphasis is placed on how information is transferred from one individual to another in order to facilitate the collective resp… more
Date: May 2014
Creator: Svenkeson, Adam
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Partner: UNT Libraries
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Fractional Calculus and Dynamic Approach to Complexity

Description: Fractional calculus enables the possibility of using real number powers or complex number powers of the differentiation operator. The fundamental connection between fractional calculus and subordination processes is explored and affords a physical interpretation for a fractional trajectory, that being an average over an ensemble of stochastic trajectories. With an ensemble average perspective, the explanation of the behavior of fractional chaotic systems changes dramatically. Before now what ha… more
Date: December 2015
Creator: Beig, Mirza Tanweer Ahmad
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Partner: UNT Libraries
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A Precise Few-nucleon Size Difference by Isotope Shift Measurements of Helium

Description: We perform high precision measurements of an isotope shift between the two stable isotopes of helium. We use laser excitation of the 2^3 S_1-2^3 P_0 transition at 1083 nm in a metastable beam of 3He and 4He atoms. A newly developed tunable laser frequency selector along with our previous electro-optic frequency modulation technique provides extremely reliable, adaptable, and precise frequency and intensity control. The intensity control contributes negligibly to overall experimental uncertai… more
Date: August 2015
Creator: Hassan Rezaeian, Nima
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Partner: UNT Libraries
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Electrostatic Effects in III-V Semiconductor Based Metal-optical Nanostructures

Description: The modification of the band edge or emission energy of semiconductor quantum well light emitters due to image charge induced phenomenon is an emerging field of study. This effect observed in quantum well light emitters is critical for all metal-optics based light emitters including plasmonics, or nanometallic electrode based light emitters. This dissertation presents, for the first time, a systematic study of the image charge effect on semiconductor–metal systems. the necessity of introducing … more
Date: May 2012
Creator: Gryczynski, Karol Grzegorz
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Partner: UNT Libraries
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Temporal Properties Of Dynamic Processes On Complex Networks

Description: Many social, biological and technological systems can be viewed as complex networks with a large number of interacting components. However despite recent advancements in network theory, a satisfactory description of dynamic processes arising in such cooperative systems is a subject of ongoing research. In this dissertation the emergence of dynamical complexity in networks of interacting stochastic oscillators is investigated. In particular I demonstrate that networks of two and three state stoc… more
Date: December 2011
Creator: Turalska, Malgorzata A.
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Partner: UNT Libraries
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A Non-equilibrium Approach to Scale Free Networks

Description: Many processes and systems in nature and society can be characterized as large numbers of discrete elements that are (usually non-uniformly) interrelated. These networks were long thought to be random, but in the late 1990s, Barabási and Albert found that an underlying structure did in fact exist in many natural and technological networks that are now referred to as scale free. Since then, researchers have gained a much deeper understanding of this particular form of complexity, largely by comb… more
Date: August 2012
Creator: Hollingshad, Nicholas W.
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Partner: UNT Libraries
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Theoretical and Experimental Investigations Concerning Microgels of Varied Spherical Geometries

Description: Polymer gels have been studied extensively due to their ability to simulate biological tissues and to swell or collapse reversibly in response to external stimuli. This work presents a variety of studies using poly-N-isopropylacrylamide (PNIPA) hydrogels. The projects have been carried out both in the lab of Dr. Zhibing Hu and in collaboration with others outside of UNT: (1) an analysis of the swelling kinetics of microgel spherical shells prepared using a novel design of microfluidic devices; … more
Date: August 2012
Creator: Wahrmund, Joshua Joseph
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Partner: UNT Libraries
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Temporal Complexity and Stochastic Central Limit Theorem

Description: Complex processes whose evolution in time rests on the occurrence of a large and random number of intermittent events are the systems under study. The mean time distance between two consecutive events is infinite, thereby violating the ergodic condition and activating at the same time a stochastic central limit theorem that explains why the Mittag-Leffler function is a universal property of nature. The time evolution of these complex systems is properly generated by means of fractional differen… more
Date: August 2014
Creator: Pramukkul, Pensri
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Partner: UNT Libraries
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Interacting complex systems: theory and application to real-world situations

Description: The interest in complex systems has increased exponentially during the past years because it was found helpful in addressing many of today's challenges. The study of the brain, biology, earthquakes, markets and social sciences are only a few examples of the fields that have benefited from the investigation of complex systems. Internet, the increased mobility of people and the raising energy demand are among the factors that brought in contact complex systems that were isolated till a few years … more
Date: August 2017
Creator: Piccinini, Nicola
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Partner: UNT Libraries
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EEG, Alpha Waves and Coherence

Description: This thesis addresses some theoretical issues generated by the results of recent analysis of EEG time series proving the brain dynamics are driven by abrupt changes making them depart from the ordinary Poisson condition. These changes are renewal, unpredictable and non-ergodic. We refer to them as crucial events. How is it possible that this form of randomness be compatible with the generation of waves, for instance alpha waves, whose observation seems to suggest the opposite view the brain is … more
Date: May 2010
Creator: Ascolani, Gianluca
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Partner: UNT Libraries
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Renewal and Memory Approaches to Study Biological and Physiological Processes

Description: In nature we find many instances of complex behavior for example the dynamics of stock markets, power grids, internet networks, highway traffic, social networks, heartbeat dynamics, neural dynamics, dynamics of living organisms, etc. The study of these complex systems involves the use of tools of non-linear dynamics and non-equilibrium statistical physics. This dissertation is devoted to understanding two different sources of complex behavior – non-poissonian renewal events also called crucial… more
Date: May 2019
Creator: Tuladhar, Rohisha
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Partner: UNT Libraries
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Electromagnetically Modulated Sonic Structures

Description: Phononic crystals are structures composed of periodically arranged scatterers in a background medium that affect the transmission of elastic waves. They have garnered much interest in recent years for their macro-scale properties that can be modulated by the micro-scale components. The elastic properties of the composite materials, the contrast in the elastic properties of the composite materials, and the material arrangement all directly affect how an elastic wave will behave as it propagates … more
Date: May 2014
Creator: Walker, Ezekiel Lee
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Partner: UNT Libraries
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Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures

Description: III-V nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solid-state white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thin-films on InGaN/GaN… more
Date: May 2012
Creator: Llopis, Antonio
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Partner: UNT Libraries
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Physical Boundary as a Source of Anomalies in Transport Processes in Acoustics and Electrodynamics

Description: Various anomalous effects that emerge when the interfaces between media are involved in sound-matter or light-matter interactions are studied. The three specific systems examined are a fluid channel between elastic metal plates, a linear chain of metallic perforated cylindrical shells in air, and a metal-dielectric slab with the interfaces treated as finite regions of smoothly changing material properties. The scattering of acoustic signals on the first two is predicted to be accompanied by the… more
Date: December 2018
Creator: Bozhko, Andrii
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Partner: UNT Libraries

Manipulation of Light-Matter Interactions in Molybdenum Disulfide (MoS2) Monolayer through Dressed Phonons (DP) and Plasmons

Description: The performance of electrical and optical devices based on two-dimensional semiconductors (2D) such as molybdenum disulfide is critically influenced due to very poor light absorption in the atomically thin layers. In this study, the phonon mediated optical absorption and emission properties in single atomic layers of MoS2 have been investigated. The electronic transitions in MoS2 due to near-field optical interaction and the influence of interface phonons due to the dielectric substrate GaN on … more
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Date: December 2019
Creator: Poudel, Yuba R
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves

Description: With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the disser… more
Date: May 2012
Creator: Nagaraj, Nagaraj
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Criticality in Cooperative Systems

Description: Cooperative behavior arises from the interactions of single units that globally produce a complex dynamics in which the system acts as a whole. As an archetype I refer to a flock of birds. As a result of cooperation the whole flock gets special abilities that the single individuals would not have if they were alone. This research work led to the discovery that the function of a flock, and more in general, that of cooperative systems, surprisingly rests on the occurrence of organizational collap… more
Date: May 2012
Creator: Vanni, Fabio
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Partner: UNT Libraries
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Theoretical and Experimental Investigations of Peg Based Thermo Sensitive Hydro Microgel

Description: Poly ethylene glycol (PEG) based microgels were synthesized and investigated. The PEG microgel has the same phase transition as the traditional poly N-isopropylacrylamide (PNIPAM). As a good substitute of PNIPAM, PEG microgel exhibits many advantages: it is easier to control the lower critical solution temperature (LCST) of the microgel by changing the component of copolymers; it has a more solid spherical core-shell structure to have a double thermo sensitivity; it is straightforward to add ot… more
Date: December 2012
Creator: Chi, Chenglin
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Partner: UNT Libraries
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