Dissertations / Theses on the topic 'Bistable'
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1
Ye, Hua. "Bistable cylindrical space frames." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613062.
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Muñoz, Aaron A. "Developments toward a micro Bistable Aerial Platform : analysis of the Quadrantal Bistable Mechanism." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002742.
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Muñoz, Aaron A. "Developments Toward a Micro Bistable Aerial Platform: Analysis of the Quadrantal Bistable Mechanism." Scholar Commons, 2008. https://scholarcommons.usf.edu/etd/419.
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The Bistable Aerial Platform (BAP) has been developed in order to further enlarge the repertoire of devices available at the microscale. This novel device functions as a switch in that its platform can lock in two positions, up or down. Herein, it will be examined and explained, but a true understanding of its workings requires a better understanding of its compliant constituent parts. The Helico-Kinematic Platform (HKP), which serves as an actuator for the BAP, is currently under investigation by another researcher and will be merely touched upon here. The focus, therefore, will rest on the analysis of the Quadrantal Bistable Mechanism (QBM), the principle component of the BAP. A preliminary pseudo-rigid-body model, an aid for the understanding of compliant mechanisms, will also be examined for the QBM. The models developed for these two devices, the HKP and QBM, can later be combined to form a full model of the Bistable Aerial Platform.
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Van, Dommelen Ronnie Francis. "Bistable distributed feedback laser diodes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/MQ48293.pdf.
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Harris, Peter. "Bistable laminates for energy harvesting." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760884.
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This thesis presents novel research in the area of energy harvesting from broadband vibra-tions. The aim of energy harvesting is to recover energy wasted or unused in the environmentto power low-consumption devices on the order of hundreds of microwatts to milliwatts. The motivation is twofold. In providing a localized, self-contained power source, device reliability, flexibility of installation location can be improved, and maintenance costs can be reduced. Furthermore, reduced reliance on batteries will mitigate the environmental impact associated with resource extraction, and disposal. To this end, this thesis investigates bistable laminates with piezoelectric transduction as broadband energy harvesters. Hitherto, a wealth of literature exists in which narrowband energy harvesters have been studied and optimized to operate over a small frequency interval. While these have been successful to the point of having devices commercially available, many situations exist where the dominant frequencies from which energy is to be harvested change with respect to time, or may be dominated by noise, thus not having a truly dominating frequency. Energy harvesters with nonlinear frequency responses have attracted substantial research interest because of their ability to respond over a broaderfrequency band. Due to complexities of the response of these harvesters, particularly when the intensity of the vibrational input is high, modeling their behavior is difficult. Designing these harvesters is therefore challenging as the relationships between the various design parameters and power output can be highly involved, or require numerical solutions as analytical solutions may not be possible. This thesis helps to address this knowledge gap. Bistable laminates ofboth cantilever and plate configuration are studied. Parametric studies are undertaken to empirically demonstrate the relationship between power output and parameters such as resistance load, proof mass addition, operation orientation, different shapes, ply angles, and introduction of adjustable magnetic compression. Modeling work is also undertaken to capture the mainfeatures of the nonlinear response such as subharmonics, superharmonics, and snap-through. A study is also carried out to quantify the differences of performance between a linear harvester and an equivalent bistable counterpart. As a practical demonstration, some plate-type harvesters are subjected to excitation patterns based on measured train data. Ultimately, thisthesis provides an in depth understanding of bistable shape, layup, and design on harvesting performance.
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Brinkmeyer, Alex. "Time-dependent bistable morphing structures." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629647.
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An investigation into the time-dependent effects of bistable morphing and deployable structures is presented, showing how the stability of these structures is influenced by viscoelastic effects and how these effects can be used as an advantage to engineer novel morphing concepts. In the context of space applications, significant relaxation effects appear in structures that have been stored for a long duration, e.g. in a space vehicle prior to launch. Here, the deployment of an ultra-thin CFRP tape spring is first studied, with the aim of understanding how long-duration stowage causes changes in its stability and how it affects its deployment behaviour. Analytical modelling and experiments show that the deployment time increases predictably with stowage time and temperature, and that analytical predictions compare well with experiments. For cases where stress relaxation become high, the structure is shown to lose its ability to deploy autonomously. Next , structures that exhibit a time-dependent effect called pseudo-bistability are considered. A pseudo-bistable structure is one that is able to gain a new stable state during relaxation and therefore becomes temporarily bist able. This is exploited to yield a novel structure which, once actuated to its second stable state, can return dynamically to its initial state after a certain recovery time without further actuation. The concept of pseudo-bistability is first demonstrated using an analytical spring-and-dashpot model, then is studied in an isotropic spherical dome through numerical modelling and experimental validation. It is shown, in particular, that a well-known geometrical parameter can be used to correlate the geometry of the dome to its recovery time. The pseudo-bistable effect is then demonstrated in a prestressed panel, and the use of composite reinforcement is considered to improve the stiffness of the structure. Results show that a limiting volume fraction exists at which the pseudo-bistable behaviour is lost. Finally, an application is proposed, whereby a pseudo-bist able structure acts as a flow controller in an air duct. Using a fluid- structure simulation, fluctuations in the outlet pressure are shown to be selectively damped by the pseudo-bistable device. In the last chapter, various other conceptual applications using time-dependent bistable devices are also explored, in the hope that this work is taken further.
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Cinti, Eleonora <1982>. "Bistable elliptic equations with fractional diffusion." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/3073/.
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This work concerns the study of bounded solutions to elliptic
nonlinear equations with fractional diffusion. More precisely, the aim of this
thesis is to investigate some open questions related to a conjecture of De Giorgi about the one-dimensional symmetry of bounded monotone solutions in all
space, at least up to dimension 8.
This property on 1-D symmetry of monotone solutions for
fractional equations was known in dimension n=2. The question remained open for n>2. In this work we establish new sharp energy estimates and one-dimensional symmetry property in dimension 3 for certain solutions of fractional equations. Moreover we study a particular type of solutions, called saddle-shaped solutions, which are the candidates to be global minimizers not one-dimensional in dimensions bigger or equal than 8. This is an open problem and it is expected to be true from the classical theory of minimal surfaces.
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Sprague, Robert Wendell 1957. "THERMALLY EVAPORATED BISTABLE THIN FILM ETALONS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276517.
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Passive intrinsic bistability is of great interest. Our Fabry-Perot interference filters exhibit bistability due to a temperature dependent refractive index. Operating across the entire viable spectrum permits wide application to the demonstration and development of concepts for optical computing. Thermal evaporation of zinc sulfide and chiolite is used to produce Fabry-Perot interference filters. The effect of the thickness of the spacer, and reflectivities of the mirrors, on the nonlinear characteristics of these devices is investigated. The mathematic description of these etalon's linear, as well as their nonlinear, behavior is presented. The experimental apparatus is described. Measured values of the minimum critical detuning and minimum observed power are presented.
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andrews, George A. "Spontaneous pulse formation in bistable systems." W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539623432.
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This thesis considers localized spontaneous pulse formation in nonlinear, dissipative systems that are far from equilibrium and which exhibit bistability. It is shown that such pulses can form in systems that are dominated by the combined effects of: (1) a saturable amplifying or gain region, (2) a saturable absorbing or loss region, and (3) cavity effects. Analysis is based upon novel models for both an inertialess material in which the absorber responds instantaneously and inertial material in which there is temporal delay in the response. Additionally, we include the situation where the material does not fully relax between pulses, i.e. memory effects. The results are shown to be generic but direct application is made to pulse formation and stability as observed and exploited in a colliding pulse mode-locked (CPM) dye laser in which the saturable gain and absorber are spatially localized. Bifurcation from a steady, pulsing state to one of several possible other states (laser dropout phenomena) is observed to occur in these systems and will also be addressed. Key results arising from the inclusion of memory effects are as follows: the existence of highly degenerate bifurcation scenarios, implying hysteresis-like behavior in drop-out/drop-in transitions; damped period-two oscillations; and much lower frequency damped oscillations---reminiscent of breathing modes.
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García, Rodríguez Pedro Ernesto. "Noise-induced reversals in bistable visual perception." Doctoral thesis, Universitat Pompeu Fabra, 2012. http://hdl.handle.net/10803/83867.
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In this thesis, a set of some prevailing rate-based models for bistable perception have been considered in order to find the implications of the novel results reported in Pastukhov & Braun (2011). These authors have quantified not only salient aspects of bistable perception (mean and dispersion of dominance distributions), but also some hidden hysteresis effects ignored up to now. Extensive computational simulations of different prevailing models rigorously demonstrate that the history-dependence of the perceptual process shown by Pastukhov & Braun (2011), effectively constrains the region of the parameter space able to replicate the empirical data. Concretely, that just small regions residing inside a bistable or two-attractor region of the whole parameter space are actually adequate to reproduce the experimental results, both for BR and KDE displays. Remarkably, the results remain valid across all the different classes of models considered, regardless the details of the neuronal implementation. The biological plausibility of the parameter region found for each of the models considered, is further stressed with respect to the widely known Levelt’s propositions. To that end, we make use of weighted sums across the parameter regions computed for each subject in the first part of this Thesis, an algorithm that constitutes an important improvement to the methodology proposed by Shpiro et al. (2007) to fit behavioral data by rate-based models. It is shown how different neuronal mechanisms clearly differ in their suitability to replicate Levelt’s propositions. For instance, models with a slow fatiguing process given by spike-frequency adaptation Wilson (2003); Shpiro et al. (2007), no matter if they are being described by linear Shpiro et al. (2007) or nonlinear Curtu et al. (2008)) functions of the activity, replicate quite well Levelt’s second law. Oppositely, a notable discrepancy between model and empirical results is found when such negative feedback is described as a long-term depression affecting the synapses between the competing neurons representing the two alternative interpretations Laing & Chow (2002); Shpiro et al. (2007). The present work finishes with a study about the capability of the mentioned models to reproduce the resonance effects happening when varying external frequencies, as shown by Kim et al. (2006). Importantly, a resonance respect to the noise dispersion (i.e., a true stochastic resonance ) is clearly demonstrated here for the first time. Previous estimations of noise dispersion (20 − 30% of the input) and its locus (adaptation variables) are questioned, by demonstrating that increased sensitivity to even weak signals of the order of less than 10% can be obtained with the models considered, with the noise variable simply entering as part of the net input feeding the neuron.En este trabajo, son considerados una serie de modelos para frecuencia neuronal ampliamente aceptados en percepción bi-estable, con el objetivo de evaluar las implicaciones de los resultados recientemente reportados en Pastukhov & Braun (2011). Estos autores han cuantificado no solamente aspectos más conocidos sobre el fenómeno (media y dispersión de las distribuciones de dominancia), sino también efectos de historia que habían sido ignorados hasta el presente. Por medio de simulaciones computacionales, se demuestra rigurosamente que la dependencia de la historia del proceso perceptual encontrada por Pastukhov & Braun (2011) efectivamente restringe la región válida de parámetros que es adecuada para reproducir los datos empíricos. Concretamente, que solamente pequeñas regiones del espacio de parámetros disponible, y que se encuentran dentro de una región dinámica bi-estable caracterizada por dos atractores, son realmente adecuadas, tanto para rivalidad binocular (BR) como para estímulos de estructura por movimiento (KDE). Resulta importante destacar que los resultados permanecen válidos de un modelo a otro, independientemente de los detalles de implementación neuronal. La plausibilidad biológica de la región de parámetros encontrada para cada modelo es entonces considerada, en el contexto de las ampliamente conocidas proposiciones de Levelt. Con tal objetivo, hacemos uso de un algoritmo de suma pesada para extraer valores medios de la regiones de parámetros correspondientes a cada sujeto. Este algoritmo constituye una importante mejora a la metodología propuesta por Shpiro et al. (2007) para ajustar modelos de frecuencia neuronal a datos comportamentales de percepción bi-estable. Es entonces mostrado como cada mecanismo neuronal considerado es clara- mente diferente en su capacidad para reproducir las proposiciones de Levelt. Por ejemplo, modelos conteniendo procesos lentos de retroalimentación negativa da- dos por adaptación de frecuencia de disparo Wilson (2003); Shpiro et al. (2007), sin importar si están descritos por funciones lineales Shpiro et al. (2007) or no lineales Curtu et al. (2008)) de la actividad, consiguen reproducir de modo razonable la segunda proposición de Levelt. Por el contrario, una notable discrepancia entre modelo y resultados empíricos es encontrada cuando tales procesos están dados por la presencia de depresión sináptica de larga duración. El presente trabajo culmina con un estudio sobre la capacidad de los mencionados modelos para reproducir los efectos de resonancia que ocurren al variar la frecuencia externa de modulación Kim et al. (2006). Es de destacar que en nuestro caso, un efecto de resonancia es encontrado respecto a la dispersión del ruido, lo cual indica la presencia de una verdadera resonancia del tipo estocástico. Este efecto es claramente demostrado para estos modelos, por primera vez, en el presente trabajo. Previas estimaciones de la dispersión del ruido (20 − 30 % de la señal de entrada) y su localización (variables de adaptación) son analizadas. Se demuestra que un incremento de la sensibilidad a incluso muy pequeñas señales de menos del 10% puede ser encontrada en estos modelos, con sólo incluir la variable de ruido como parte de la corriente neta que alimenta la neurona.
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Au, Ping Tong. "Mechanically stabilized bistable FLCD on flexible substrates /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ECED%202006%20AU.
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Anderson, Jeffrey K. "Piezoresistive Sensing of Bistable Micro Mechansim State." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1074.pdf.
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Syvertsson, Simon. "Bistable differentiation in an isogenic cell population." Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/3002.
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Single-cell organisms such as bacteria have traditionally been regarded as discrete units, which in turn has been reflected by the bulk-level methods used to study them. A growing culture of the bacterium Bacillus subtilis will exhibit a range of heterogeneous genetic developmental programmes such as motility, competence, and finally sporulation. As a popular choice for production of compounds in bioreactors, the bistable behaviours of B. subtilis may be undesirable traits, as they divert resources from their intended activity of synthesising a product. This thesis investigates a novel observation that expression of a ribosomal subunit gene (rpsD) is elevated in the non-motile state of B. subtilis, using unstable GFP reporter constructs. The implications of using a proteolytically unstable protein as a reporter are also investigated with regard to the effect of protein degradation rates on the reporter construct, as well as presenting evidence for modulation of ClpXP activity in a pnpA background. Investigation of the motile/non-motile heterogeneous phenotype of B. subtilis posed a challenge for automated analysis pipelines. This thesis addresses this problem by developing and testing microscopy analysis pipelines designed to circumvent the traditional requirement for physically separated objects in a phase contrast channel, and instead using nucleoid or membrane stains to identify cells in a microscopy image. Other factors impacting the activity of a proteolytically unstable PrpsD reporter construct were investigated, including the rate of degradation of the reporter, and integration locus of the reporter construct. To assess the impact of locus positioning, a genetic tool was also created to survey changes in noise and overall expression levels from two homogeneously expressed promoters across different positions on the chromosome.
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Yuan, Guohui. "Switching characteristics of bistable semiconductor ring lasers." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492549.
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Semiconductor ring lasers (SRLs) have been considered as an attractive element in the integrated photonic circuits since their first demonstration. They are increasingly regarded as a promising candidate for integrated all optical functional devices due to their unique feature of directional bistability. Switching which can be triggered by external optical injection between the two directions represents a truly 'digital' optical response.
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Betts, David. "Modelling and optimisation of bistable composite laminates." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549838.
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Asymmetric composite laminates can have a bistable response to loading. The potentially large structural deformations which can be achieved during snap-through from one stable state to another with small and removable energy input make them of interest for a wide range of engineering applications. After 30 years of research effort the shapes and response to applied loads of laminates of general layup can be quantitatively predicted. With attention switching to the incorporation of bistable laminates for practical applications, tools for the design and optimisation of actuated bistable devices are desirable. This thesis describes the analytical and experimental studies undertaken to develop novel modelling and optimisation techniques for the design of actuated asymmetric bistable laminates. These structures are investigated for practical application to morphing structures and the developing technology of piezoelectric energy harvesting. Existing analytical models are limited by the need for a numerical solver to determine stable laminate shapes. As the problem has multiple equilibria, convergence to the desired solution cannot be guaranteed and multiple initial guesses are required to identify all possible solutions. The approach developed in this work allows the efficient and reliable prediction of the stable shapes of laminates with off-axis ply orient at ions in a closed form manner. This model is validated against experimental data and finite element predictions, with an extensive sensitivity study presented to demonstrate the effect of uncertainty and imperfections in the laminate composition. This closed-form solution enables detailed optimisation studies to tailor the design of bistable devices for a range of applications. The first study considers tailoring of the directional stiffness properties of bistable laminates to provide resistance to externally applied loads while allowing low energy actuation. The optimisation formulation is constrained to guarantee bistability and to ensure a useful level of deformation. It is demonstrated that 'cross-symmetric' layups can provide stiffness in an arbitrary loading direction which is five times greater than in a chosen actuation direction.
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Zhang, Boshu. "Bistable and multi-stable thin-walled structures." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:05e0e48f-2da6-4d53-914a-cc1b46b9e87d.
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This study aims to comprehend the bistable and multi-stable behaviour of flexible straws with the intention of utilising it for future engineering applications. This behaviour is achieved by the multiple inversions of conical frustum shells within the corrugation of a flexible straw. This study examined the effects of various material models, geometry variables and loading methods on the inversion of close-top and open-top conical frustum shells via experiments and FEM simulations. This thesis consists of three main parts, and the second and the third parts are complementary to each other: First, we investigated the effects of applying a uniform vertical load to the upper rim of open-top frustum shells via FEM simulations. A reference model was simulated based on the measurements of an ordinary polypropylene flexible straw specimen, using two material models - linear elastic and elastically perfectly plastic. The effects of the interactions between frusta of the corrugated segment of a flexible straw were also studied by evaluating the difference in responses between an individual frustum and conjugated models of two or three frusta. It was found that by constraining the rotation of its bottom rim, an individual frustum can fairly reproduce the complex bistable behaviour of the shorter frustum within the corrugated part of a flexible straw. Furthermore, detailed parametric studies that focused on the effects of various geometric parameters were conducted and generalised formulas that predicted the critical force were derived. A comparison between the simulated results and the analytical model in predicting progressive inversion was made to distinguish the geometric boundaries that separate the one-off snap-through to the progressive inversion of frustum shells. Next, the behaviour of close-top frustum shells in response to vertical point loading at various locations on the top surface was evaluated. A hyperelastic material was used to fabricate the physical specimens. During the experiments, the corresponding deformed shapes were recorded by 3D scanning in addition to measurements of the displacement and reaction force. We observed a close resemblance between the experimental and FEM simulated results, which validated the FEM models. Two local peaks were observed before the structure was fully inverted into its secondary stable state and the overall critical force of the structure was defined by the higher one of the two. The relationship between their magnitudes and the loading locations was analysed and an optimal loading location which gave the minimum critical force was proposed and verified by additional simulations. Furthermore, generalised formulas in predicting critical force were also acquired based on parametric studies. The optimal loading location was found to be constant in spite of variations in height and thickness. The third part of this thesis discussed the effects of lateral point loading on both close-top and open-top frustum shells at various locations on the side surface and supplemented the second part. It is found that the removal of the top surface could cause the critical force to decrease if a point load was applied laterally. Moreover, we were able to fully invert the structure with a lower critical force through lateral loading in comparison to vertical loading.
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Kim, Sukkeun. "Stochastic chaos and resonance in bistable systems /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Knott, Geoffrey. "New forms of bistable composite slit tube." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/848818/.
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In recent years extremely small satellites have been developed in response to trends in the space industry to achieve more for less cost. Extremely lightweight and efficiently packaged deployable structures are essential for achieving large-scale applications including communication antennas, solar arrays, and in recent years, deorbiting drag-sails. This thesis is motivated for developing novel deployable helical antennas for space-based maritime surveillance. The helical antenna technology provides packaging efficiency and radio frequency characteristics superior to the latest efforts of international research groups. To achieve this, the research presented focuses on developing the proven bistable composite slit tube (BCST) deployable technology. These are open-section tubular structures which can be deployed and rolled up into a compact coil, analogous to a tape measure, but do not require constraint to remain stowed. This behaviour is referred to as bistability and enables lightweight and relatively simple deployable structures for spacecraft applications. New forms of BCST are modelled through the introduction of additional curvatures, manufactured and described in this work with two new subcategorisations established: toroidal and helical. Toroidal BCSTs are doubly curved with both principal curvatures initially non-zero in the deployed stress-free state. Helical BCSTs are doubly curved and twisted out-of-plane. Investigations into the effects of geometrical parameters and laminated composite material properties on the bistable coils of both types are presented. The results provide an understanding of bistable behaviour in new forms of BCST previously neglected in the literature, which is almost exclusively focused on straight forms. As a consequence of this research, new deployable structure technologies are envisaged in the areas of compact terrestrial shelters and small satellite communications.
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Masters, Nathan D. "A Self-Retracting Fully-Compliant Bistable Micromechanism." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/86.
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The purpose of this research is to present a class of Self-Retracting Fully-compliant Bistable Micromechanisms (SRFBM). Fully-compliant mechanisms are needed to overcome the inherent limitations of microfabricated pin joints, especially in bistable mechanisms. The elimination of the clearances associated with pin joints will allow more efficient bistable mechanisms with smaller travel. Small travel, in a linear path facilitates integration with efficient on-chip actuators. Tensural pivots are developed and used to deal with the compressive loading to which the mechanism is subject. SRFBM are modeled using the Pseudo-Rigid-Body Model and finite element analysis. Suitable configurations of the SRFBM concept have been identified and fabricated using the MUMPs process. Complete systems, including external actuators and electrical contacts are 1140 μm by 625 μm (individual SRFBM are less than 300 μm by 300 μm). These systems have been tested, demonstrating on-chip actuation of bistable mechanisms. Power requirements for these systems are approximately 150 mW. Testing with manual force testers has also been completed and correlates well with finite element modeling. Actuation force is approximately 500 μN for forward actuation. Return actuation can be achieved either by external actuators or by thermal self-retraction of the mechanism. Thermal self-retraction is more efficient, but can result in damage to the mechanism. Fatigue testing has been completed on a single device, subjecting it to approximately 2 million duty cycles without failure. Based on the SRFBM concept a number of improvements and adaptations are presented, including systems with further power and displacement reductions and a G-switch for LIGA fabrication.
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Gomm, Troy Alan. "Development of In-Plane Compliant Bistable Microrelays." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/81.
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Bistable microrelays have many possible applications and have the potential to reduce the size, weight, power consumption, and cost of products in which they are used. This research outlines the current state of microrelays, presents three new compliant bistable micromechanisms, and characterizes their performance as microrelays. The characterization includes a treatment of a new force-tester, a preliminary contact resistance study, contact-force measurements, switching time measurements, insertion loss, AC isolation, breakdown voltage, and DC isolation. This document also includes recommendations for further research.
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Mairesse, Benjamin. "Robustness of Bistable Switches in Gene Regulatory Networks." Thesis, KTH, Reglerteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-106248.
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Gene expression often reacts to intra- and extra-cellular signals in an ”on-off” switchlike manner. These switches, which display hysteresis, correspond to multiple steady-state solutions of the gene regulatory network and are created through saddle-node bifurcations at which a single real eigenvalue of the local Jacobian crosses the imaginary axis for changes in some system parameter. From control theory, it is well known that such an instability can be induced by a single positive feedback loop, possibly involving only a single gene and its corresponding mRNA. However, experimental results have suggested that bistable switches often involve several interlinked feedback loops. Since such a design is relatively costly, it is reasonable to assume that the excessive loops serve a purpose. A standing hypothesis is that the existence of multiple loops improves both the performance and the robustness of the switches. With performance is here understood the speed of switching, while robustness usually refers to the sensitivity of the switch with respect to noisy signals. The aim of this project is to consider these claims, and in particular the one concerning robustness, from a control theoretic perspective. First, an analysis of some specific biological examples will be performed, considering robustness both with respect to noise and with respect to model (systems) perturbations. In the second part, the aim is to propose a multiple loop design that provides optimal robustness.
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Alqasimi, Ahmad. "Design Of Shape Morphing Structures Using Bistable Elements." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5897.
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This dissertation presents new concepts and methodology in designing shape-morphing structures using bistable elements. Developed using the Pseudo-Rigid-Body Model (PRBM), linear bistable compliant mechanism elements produce predictable and controllable length changes. Step-by-step design procedures are developed to guide the design process of these bistable elements. Two different examples of Shape-Morphing Space Frames (SMSFs) were designed and prototyped utilizing the bistable linear elements in a single-layer grid, in addition to flexures and rigid links, to morph a cylindrical space frame into both a hyperbolic and a spherical space frame. Moreover, bistable unit-cell compliant-mechanism elements were also developed to morph a compact structure from a specific initial shape to a final specific shape. The detailed design of those unit cells were done using Computer-aided design (CAD) software following a novel design procedure to transform a one-degree-of-freedom mechanism into a structure with sufficient compliance within its links to toggle between two chosen stable positions. Two different design examples were investigated in this research and prototyped to demonstrate the ability to morph disks into a hemisphere or a sphere with the structure being stable in both states (disk and sphere).
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Li, Bei. "All-optical functions using bistable semiconductor ring lasers." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508062.
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Neilson, Matthew. "Flow effects in bistable nematic liquid crystal devices." Thesis, University of Strathclyde, 2008. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21943.
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We consider a nematic liquid crystal device in which a bistable surface anchoring term produces two stable states, a Vertical State (i. e. all molecules are homeotropically aligned) and a Hybrid Aligned Nematic (HAN) State (i. e. the molecules are homeotropically aligned on one boundary and homogeneously aligned on the other). Our one-dimensional model determines the director profile throughout a nematic cell by minimizing its free energy. The free energy in this model contains dielectric, elastic, flexoelectric and anchoring terms. This constitutes what we denote the 'no-flow' model. An expanded, so-called 'flow model', also includes a flow equation that we couple with our system of director equations. We then introduce three time integration methods for our numerical simulations, namely an explicit method, a semi-implicit method and a fully-implicit method, each of which employs an adaptive time-stepping algorithm to control the size of each time-step. Numerical simulations also employ a moving mesh algorithm to control the positioning and quantity of node points used at each time-step. We then compare each simulation method to determine which provides the optimal balance of speed and accuracy. We investigate switching for voltage pulses of different magnitude and duration in order to graph standard rV-plots. Each switching region is determined by the interaction between the bistable surface and bulk equations once the applied voltage is removed, which is a relatively complex process. We develop and present a powerful algorithm for automatically generating rV-plots corresponding to any given parameter set. Using this algorithm, we then investigate the effect of each parameter on the switching characteristics of our cell, using both the standard model and the expanded 'flow' model. The effects of flow are investigated by comparing the results of each model via numerical simulation. We show that flow-induced kickback in the director can significantly affect the results obtained using a no-flow model.
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Galbraith, Ian. "Diffractive and diffusive phenomena in optically bistable devices." Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1614.
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Mullings, Jason Andrew. "Spatio-temporal behaviour of optically bistable InSb etalons." Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/1337.
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Iurasov, Volodymyr. "Contrôle passif en vibroacoustique avec absorbeur dynamique bistable." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0034.
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Le travail présenté dans cette thèse est dédié à l’étude d’un absorbeur bistable continu basé sur le principe du "Nonlinear Energy Sink" (NES) et son utilisation pour l’atténuation des vibrations d’un système mécanique à plusieurs degrés de liberté sous excitation acoustique. Le modèle analytique du comportement linéaire de l’absorbeur ainsi que le modèle numérique complet ont été présentés, analysés et validés par des séries d’expériences. Le complexité du transfert énergétique ciblé ("Targeted Energy Transfer" ou TET) entre l'absorbeur et le système primaire à contrôler n’a pas permis une description analytique simple. Nous avons donc choisi de concentrer cette étude sur l’exploration expérimentale et numérique de l’absorbeur couplé à des systèmes mécaniques sous excitations harmonique et aléatoire ainsi que sur l’identification des mécanismes de transfert d’énergie. Le système couplé a montré une dynamique très riche du fait de différents régimes de TET qui ont été décrits dans la littérature pour d’autres types de NES. Ce projet a été financé par Saint-Gobain. L’absorbeur a été adapté pour l’application prévue par la direction industrielle de la thèse: contrôle des vibrations de la double paroi sous excitation acoustique afin d’améliorer l’isolation acoustique fournie par le système.Les connaissances qualitatives sur la dynamique de l’absorbeur obtenues à partir des résultats expérimentaux et numériques, ainsi que l’analogie avec les autres types de NES, ont permis la création d’un absorbeur qui répond à la problématique posée. Les moyens pour l’optimisation et le développement de l’absorbeur ont été identifiés et les simulations préliminaires ont été fourniesThe work presented in this thesis is dedicated to the study of a continuous bistable absorber based on the principle of Nonlinear Energy Sink (NES) and its use for the vibration mitigation of a many-degree-offreedom mechanical systems under acoustic excitation. The analytical model of the linear behavior of the absorber and its complete numerical model were presented, analyzed and validated by series of experiments. The complexity of the Targeted Energy Transfer (TET) between the absorber and the primary system did not allow a simple analytical description. We have chosen to concentrate this study on the experimental and numerical exploration of the absorber coupled to mechanical systems under harmonic and random excitations, as well as on the identification of the mechanisms of energy transfer. The coupled system have shown very rich dynamics as it possessed different regimes of TET, which were earlier described in literature for other types of NES. This project was funded by Saint-Gobain. The absorber was adapted for the application foreseen by the industrial supervisors of the PhD: the vibration control of partitioning double walls under acoustic excitation so that to improve the acoustic isolation provided by the system. The qualitative knowledge on the absorber dynamics obtained from the experimental and numerical results, as well as the analogy with the other types of NES, permitted the creation of an absorber which corresponds to the problematic. The ways for the further optimization and development of the absorber were identified and preliminary simulations were provided
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Giddings, Peter F. "Piezoelectrically actuated bistable composite laminates for structural morphing." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538161.
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Ekström, Lars Johan. "Welding of bistable fibre-reinforced thermoplastic composite pipelines." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614933.
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Kaplan, David Louis. "Characterizing chaos in a hybrid optically bistable device." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184440.
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Turbulence and periodic oscillations are easily seen with an optically bistable device with a delay in the feedback. The device is a hybrid, having both optical and electronic components. The details of the time-dependent output are investigated. In particular, as the input intensity is increased, the device output goes through a series of second-order nonequilibrium phase transitions or bifurcations. A truncated period-doubling sequence is observed prior to the onset of turbulence or chaos. The truncation is shown to be due to a noise-induced bifurcation gap. Within the chaotic regime, the device largely follows the reverse bifurcation scheme of Lorenz. In addition, there is a small domain of frequency-locked behavior that exists within the chaotic domain. These frequency-locked waveforms represent an alternate path to chaos. With the route to choas well understood, it remained to characterize the erratic motion itself. Dimension and correlation entropy are measured for various settings of our hybrid device. The measured dimension is found to be significantly less than dimensions consistent with a conjecture due to Kaplan and Yorke. The standard method of determining correlation entropy is shown to yield more than one value.
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Pirrera, Alberto. "Bistable structures for morphing applications using anisotropic shells." Thesis, University of Bristol, 2011. http://hdl.handle.net/1983/2ca5dda6-993e-45c0-8378-40a10aa489a0.
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An investigation into the thermally-induced bistability of composite plates and shells is presented. The principal aim is to provide novel capabilities for analytical modelling and optimum design for potential morphing applications. One possible mechanism for obtaining bistability is by tailoring the thermal expansion coefficient of plies within a laminate. For instance, unsymmetric laminates may warp and assume two stable configurations upon cooling down from cure to room temperature. Such behaviour is inherently nonlinear in nature and presents complex details that, despite being crucial for the feasibility of potential morphing applications, are not captured in sufficient fidelity by the models available in the literature. In the current approach, the equilibrium equations are discretised using polynomial bases, and solved following a Ritz approach. As a novelty, use is made of suitably derived, non-dimensional lamination theories. This ameliorated the inher- ently poor conditioning properties of Ritz discretisations and, as a consequence, to use high-order approximations. The increased degrees of freedom within the models are shown to be the first analytical solutions to accurately reflect the underlying mechanics and several characteristic details. Furthermore, Ritz discretisations are complemented by numerical continuation routines based on pseudo-arclength algorithms. This approach provides the means for a systematic and parametric exploration of the design space. Subsequently, a tool for optimal design is obtained that offers key advantages over the more conventional natural continuation method or commercial FE software. Since bistable laminates feature very large displacements, a further aim was to assess whether the Lagrangian equilibrium equations on which the models are based were adequate or whether a Eulerian description would be necessary. Undertaking this study required a detailed understanding of the strain descriptors. With regard to shells, this led to the formulation of a consistent first-order shear deformation theory, which gives novel insight into the structural mechanics of curved panels.
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Volte, Alix. "Photo-induced cooperativity in bistable volume-changing materials." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S037.
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Le domaine des transitions de phase ultra-rapides est fondé sur de remarquables développements des sources d’impulsion disponibles, des THz aux rayons X. Actuellement, les techniques pompe-sonde atteignent le régime temporel de la femtoseconde, i.e. une échelle de temps plus courte que celle des déplacements atomiques. Typiquement, un laser de pompe porte un système dans un état électroniquement excité, tandis que l’évolution temporelle de la dynamique structurale est suivie grâce à une impulsion de sonde retardée temporellement. De plus, les sources laser peuvent générer des impulsions intenses, avec un nombre de photons approchant le nombre d’entités potentiellement excitées. De telles impulsions peuvent induire des états hautement excités, impliquant un nombre macroscopique d’atomes ou molécules et portant le système loin de son état d’équilibre. Ces effets précurseurs peuvent être suivis par l’établissement d’un nouvel ordre électronique et structural, et peuvent donc amener à une transition de phase du système excité. Cette approche représente une nouvelle opportunité de modifier les fonctionnalités d’un matériau : agir temporellement sur un état atomique ou moléculaire excité, plutôt qu’effectuer la commutation d’un état d’équilibre à un autre en jouant sur un paramètre de contrôle statique. De plus, les déplacements atomiques peuvent advenir selon un mouvement collectif et cohérent, d’une façon fondamentalement différente de ce qui se passe lors d’une excitation thermique incohérente. L’objectif de cette thèse était d’explorer, à l’aide de la diffraction ultrarapide de rayons X, les aspects de la dynamique couplée entre contrainte et transformation, dans le cadre des transitions de phase induite par impulsion laser dans les matériaux à changement de volume. Ce projet se situe à la croisée du domaine des transitions de phase photo-induites, de la physique des phénomènes photo-acoustiques et non-linéaires, ainsi que de l’étude des effets élastiques dans les matériaux à électrons corrélés. Nous nous attendons à ce que cet effet élastique coopératif photo-induit soit particulièrement efficace dans les matériaux bistables, montrant un changement de volume significatif à la transition. C’est le cas des composés étudiés ici, notamment dans les matériaux à transition de spin, où la coopérativité est gouvernée par le champ élastique à longue portée, émergeant du gonflement des molécules lors du passage d’un état de spin à l’autre. D’autres candidats prometteurs dans le cadre de l’exploration de l’universalité de la coopérativité élastique photo-induite, sont les isolants de Mott, qui présentent une commutation de l’état de résistivité, ainsi que les nano-cristaux d’oxydes de métaux, montrant un régime bistable à température ambianteThe field of ultrafast structural dynamics is based on remarkable developments of available pulse sources, from THz to x-rays. Currently, pump-probe techniques operate on the femtosecond time scales, i.e. faster than atomic motions. Typically, a laser pump pulse drives a system onto an electronically excited state, while the structural dynamics temporal evolution is tracked with a delayed probe pulse. Moreover, laser light sources can generate intense pulses with a number of photons approaching the number of potentially photo-excited species. Such pulses can induce highly excited states, involving a macroscopic number of atoms or molecules and driving the system far from equilibrium. These precursor effects may be followed by the establishment of a new electronic and structural order and thus may bring about a phase transition of the excited system. This represents a new approach to direct materials functionalities: timely acting on an atomic or molecular excited state, rather than switching from an equilibrium state to another by tuning a static control parameter. Moreover, such induced atomic displacements may occur in a collective coherent motion, in a fundamentally different way from incoherent thermal excitation.The goal of this PhD was to explore through ultrafast x-ray diffraction some aspects of the coupled strain-transformation dynamics, in the frame of phase transitions induced by a laser pulse in volume-changing materials. This project stands between the field of photo-induced phase transitions, the physics of photo-acoustics and non-linear wave phenomena, as well as the study of the elastic field effects in correlated electrons materials. We expect this photo-induced elastic cooperative process to be particularly efficient in bistable materials showing significant volume change at the transition, as those investigated here. It is the case of spin crossover materials, where cooperativity is governed by long-range elastic field arising from the swelling of molecules between the two spin states. Other promising candidate materials to explore the universality of photo-induced elastic cooperativity are Mott insulators exhibiting resistive switching, and metal oxide nano-crystals with a bistable regime at room temperature
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Axelrod, Kevin Connor. "Bistable dynamics in microbial ecology and systems biology." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493470.
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Bistability, in which a system has two stable states, is a common property of many dynamic systems. This thesis explores the properties of such systems across a range of length scales, from gene circuits to ecosystems. Cells often store memories of environmental stimuli using bistable gene circuits. High fidelity memory storage requires that a state has a long lifetime. However, an underappreciated aspect of stable memory is that the distance from a bifurcation could determine how sensitive a state is to perturbations in the extracellular environment. We predict that cell memory should become increasingly sensitive to perturbations near a bifurcation and test this idea in three different gene circuits: a toggle switch, the yeast galactose utilization network, and the E. coli lactose utilization network.
In a second study, we explore how the environmental context in which two species interact can influence their mode of interaction. Two species in nature often form reciprocally beneficial partnerships termed mutualisms, but in certain environmental regimes the species might shift to competing with one another for resources. This mutualism-competition transition has been understudied in experimental ecosystems. Using a synthetic yeast cross-feeding mutualism, we modulate the degree to which two partners rely on each other by supplementing the cells with variable amounts of nutrients. Surprisingly, we find that as the amount of supplemented nutrients is increased, the system passes through eight qualitatively distinct dynamic regimes: extinction, obligatory mutualism, obligatory/facultative mutualism, facultative mutualism, parasitism, amensalism, competition, and competitive exclusion.
In a third study, we probe how population growth dynamics can influence the probability of evolutionary rescue. Natural populations frequently face harsh environments in which their death rate exceeds their birth rate and population size tends toward zero. In such scenarios, populations can either go extinct, migrate to a better habitat, or adapt to the harsh environment. Natural populations often exhibit an “Allee effect,” in which populations grow slowly at low density due to struggles with such behaviors as finding a mate or collective hunting. We hypothesize that the presence of an Allee effect could impede evolutionary rescue and confirm this hypothesis in a model laboratory yeast ecosystem.Biophysics
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Cherry, Brian B. "Characterizing the Three-Dimensional Behavior of Bistable Micromechanisms." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2274.pdf.
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Tawfik, Samer Anwar. "Stability and morphing characteristics of bistable composite laminates." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24702.
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Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Erian Armanios; Committee Member: D. Stefan Dancila; Committee Member: Juan R. Cruz; Committee Member: Massimo Ruzzene; Committee Member: Rami Haj-Ali
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Manrique, Juarez Maria Dolores. "Micro and nanoactuators based on bistable molecular materials." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30244/document.
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Les systèmes microélectromécaniques (MEMS) sont des dispositifs de taille micrométrique capables de transformer un signal mécanique en un signal électrique et vice-versa. Ils sont aujourd'hui largement répandus dans notre vie quotidienne pour la détection, la transformation de l'énergie et l'actionnement de dispositifs grâce à leur faible dissipation énergétique, leur réponse ultra-rapide et leur grande sensibilité. Même si depuis plusieurs décennies, les progrès technologiques ont entraîné la miniaturisation des ces dispositifs, il reste nombreux challenges à surmonter dont l'un des plus importantes est l'intégration à l'échelle nanométrique d'actionneurs à base des matériaux dit " intelligents " (à ces dimensions, les matériaux habituellement utilisés perdent leurs propriétés d'actionnement). Dans ce contexte, ce travail de thèse avait pour objectif d'explorer l'utilisation des matériaux moléculaires à transition de spin pour le développement d'actionneurs électromécaniques. Dans ce but, nous avons conçu des microleviers en silicium que nous avons recouvert par différentes molécules à transition de spin soit par sublimation, soit par " spray-coating ". Les MEMS ont été caractérisés à température et pression variables en modes dynamique et statique à l'aide d'un unique dispositif expérimental. Les résultats obtenus démontrent que les molécules à transition de spin peuvent être intégrées, à l'aide de différents procédés de fabrication, dans des dispositifs MEMS et qu'il est possible de réaliser l'actionnement à l'aide d'une source d'énergie thermique (chauffage et refroidissement) et/ou lumineuse. Simultanément, cette étude a également permis d'évaluer les propriétés mécaniques des matériaux à transition de spin (module de Young, coefficient de Poisson) qui restent mal connuesMicroelectromechanical systems (MEMS) are micrometric devices able to transform a mechanical signal into an electrical one and vice-versa. In the past years they have been successfully employed in different fields of our everyday life for sensing, transducing different forms of energy and for actuating purposes thanks to their low energy dissipation, fast response and high sensibility. Even if recent technological progress has allowed a considerable miniaturization of these devices, several challenges remain. In particular the integration of smart actuating materials at the nanometric scale remains arduous because in most cases they lose their actuating properties at reduced sizes. In this context, this thesis work aimed for exploring the possibility of using molecular spin crossover materials for the development of electromechanical actuators. To this aim we have conceived silicon microcantilevers, which have been coated by various spin crossover molecules using either thermal evaporation or spray-coating methods. The MEMS have been characterized at variable temperature and pressure both in dynamical and static modes using a single experimental setup. The results prove that spin crossover molecules can be successfully integrated into silicon MEMS devices using different fabrication processes and their actuation can be achieved using either a thermal energy source or light irradiation. In parallel, this work has allowed us to extract relevant mechanical properties of spin crossover materials (Young's modulus, Poisson's ratio), which have been largely unknown previously
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Hanna, Brandon Holbrook. "Modeling and Testing of Bistable Waterbomb Base Configurations." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4336.
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Origami is making an impact in engineering as solutions to problems are being found by applying origami principles (eg. flat-foldability) and using specific crease patterns as inspiration. This thesis presents an in-depth analysis of a particular origami fold -- the waterbomb base -- to facilitate its use in future engineering problems. The watebomb base is of interest due to its familiarity to the origami community, simple topology (can be made by folding a single sheet of paper four times), scalability, generalizability, and interesting kinetic behavior. It can behave as a nonlinear spring as well as a one- or two-way bistable mechanism. This thesis presents models of the kinetic behavior of the traditional waterbomb base as well as some non-traditional variants to be used as tools in future development of waterbomb-base-inspired mechanisms. In all cases considered here, developability as well as rotational symmetry in both the geometry and motion of the mechanisms are assumed. The thesis provides an introduction to origami and reviews some of the ways in which it has been studied and applied in engineering fields. The waterbomb base is also presented as a specific origami fold with practical application potential. Models for the behavior of the traditional waterbomb base are introduced and its potential usefulness as a testbed for actuation methods is discussed. Models are developed for its kinematic and bistable behavior, including the forces needed to transition between stable states. These models are validated by comparison to physical prototype testing and finite element analysis. The thesis introduces the generalized waterbomb base (WB) and generalized split-fold waterbomb base (SFWB). The WB maintains the pattern of alternating mountain and valley folds around the vertex but in this generalized case any even number of folds greater than or equal to 6 is allowed. An SFWB is created by splitting each fold of a WB into two “half folds”, effectively doubling the number of folds and links but halving the deflection at each fold. The same models that were developed for the traditional waterbomb base are developed for the WB and the SFWB and a few potential applications are discussed.
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Baker, Michael S. "On-Chip Actuation of Compliant Bistable Micro-Mechanisms." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/52.
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Two compliant bistable micro-mechanisms have been developed which can be switched in either direction using on-chip thermal actuation. The energy storage and bistable behavior of the mechanisms are achieved through the elastic deflection of compliant segments. The pseudo-rigid-body model was used for the compliant mechanism design, and for analysis of the large-deflection flexible segments. To achieve on-chip actuation, the mechanism designs were optimized to reduce their required rotation, allow them to be switched using linear-motion thermal actuators. The modeling theory and analysis are presented for several design iterations. Each iteration was successfully fabricated and tested using either the MUMPs or SUMMiT surface micromachining technology.
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Jasaitis, Valdas. "Computer modeling of self-ordered fronts under oscillating zero-mean forces." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120302_090624-00150.
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Spatio-temporal control of the self-ordered structures by use of the time-dependent oscillatory fields of zero-time average, either deterministic (temporally regular) or noisy (temporally irregular) ones, has today become a fundamental field of multidisciplinary research in a wide variety of the highly nonlinear systems of the different physical origin. The self-ordered bistable fronts in the essentially dissipative systems of the reaction-diffusion type, that are formulated by parabolic partial differential equations, are investigated in the dissertation. The objective of the research is to investigate new possibilities of controlling the directed net motion of the self-ordered bistable fronts by the deterministic and stochastic zero-mean ac forces using computer modeling and analytic tools. In order to achieve the objective mathematical and numerical models were applied, computer software was created and new possibilities of controlling the directed net motion of bistable fronts by use of the zero-average periodic, quasi-periodic and bounded noise fields were investigated.Savaime susidarančių lokalizuotų struktūrų valdymas deterministiškai (reguliariai) arba stochastiškai (atsitiktinai) osciliuojančiais laukais, kurių vidutinė vertė yra nulis, yra plačiai paplitęs įvairiose terpėse. Disertacijoje nagrinėjami savame susidarantys bistabilūs frontai disipatyviose sistemose, kurios aprašomos netiesinėmis parabolinėmis diferencialinėmis lygtimis su dalinėmis išvestinėmis. Disertacijos tikslas yra ištirti kryptingo bistabilių frontų dreifo valdymo nuliniais laukais galimybes, taikant kompiuterinį modeliavimą bei analitinius metodu. Tikslui pasiekti buvo sudaryti matematinis bei skaitinis modeliai, sukurta programinė įranga ir skaitiškai ištirtos savaiminių bistabilių frontų valdymo galimybės, naudojant periodinius, kvaziperiodinius ir stochastinius nulinius laukus.
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Jasaitis, Valdas. "Savaiminių frontų osciliuojančiuose nuliniuose laukuose kompiuterinis modeliavimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120302_090834-15056.
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Savaime susidarančių lokalizuotų struktūrų valdymas deterministiškai (reguliariai) arba stochastiškai (atsitiktinai) osciliuojančiais laukais, kurių vidutinė vertė yra nulis, yra plačiai paplitęs įvairiose terpėse. Disertacijoje nagrinėjami savame susidarantys bistabilūs frontai disipatyviose sistemose, kurios aprašomos netiesinėmis parabolinėmis diferencialinėmis lygtimis su dalinėmis išvestinėmis. Disertacijos tikslas yra ištirti kryptingo bistabilių frontų dreifo valdymo nuliniais laukais galimybes, taikant kompiuterinį modeliavimą bei analitinius metodu. Tikslui pasiekti buvo sudaryti matematinis bei skaitinis modeliai, sukurta programinė įranga ir skaitiškai ištirtos savaiminių bistabilių frontų valdymo galimybės, naudojant periodinius, kvaziperiodinius ir stochastinius nulinius laukus.Spatio-temporal control of the self-ordered structures by use of the time-dependent oscillatory fields of zero-time average, either deterministic (temporally regular) or noisy (temporally irregular) ones, has today become a fundamental field of multidisciplinary research in a wide variety of the highly nonlinear systems of the different physical origin. The self-ordered bistable fronts in the essentially dissipative systems of the reaction-diffusion type, that are formulated by parabolic partial differential equations, are investigated in the dissertation. The objective of the research is to investigate new possibilities of controlling the directed net motion of the self-ordered bistable fronts by the deterministic and stochastic zero-mean ac forces using computer modeling and analytic tools. In order to achieve the objective mathematical and numerical models were applied, computer software was created and new possibilities of controlling the directed net motion of bistable fronts by use of the zero-average periodic, quasi-periodic and bounded noise fields were investigated.
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Johansen, Sigurd Hagen. "Modelling and Analysis of a Synthetic Bistable Genetic Switch." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12652.
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In the field of systems and synthetic biology there has been an increasing interest for the use of genetic circuits during the last decade. Several circuits have been successfully put together, many of which were based on models. During this thesis a model for a toggle switch was analysed both deterministically and stochastically.The HOM2-circuit approximation for a bistable tuneable switch from Ghim and Almaas (2009) was re-derived in order to make it asymmetrical. Deterministic analysis was conducted yielding stability diagrams, describing the phase plane showing bistability for the genetic switch. Furthermore, stochastic simulations of the approximation were conducted. This gave a somewhat narrower bistable area than the deterministic analysis, possibly due to the nature of saddle-node bifurcations. Parameter values for a switch based on experiments were estimated for the approximation, and these were used in a stochastic simulation. The result from this simulation was in correspondencewith the deterministic analysis. A stochastic simulation of the complete circuit was conducted based on parameter values found in literature. For this simulation bistability was not shown.In order to further explore the circuit, and validity of the approximation, experimental investigation is needed. This has been planned together with Rahmi Lale, PhD, and Professor Eivind Almaas at the Department of Biotechnology, NTNU.
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Choueifati, Joseph Georges. "Design and modeling of a bistable spherical compliant micromechanism." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002290.
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Creyts, Don Stafford IV. "Design and fabrication of a MEMS magnetic bistable valve." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17950.
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Smith, Chester. "Modeling and Parameter Study of Bistable Spherical Compliant Mechanisms." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3356.
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The bistable spherical compliant mechanism (BSCM) is a novel device capable of large, repeatable, out-of-plane motion, characteristics that are somewhat difficult to achieve with surface micromachined microelectromechanical systems. An improved pseudo-rigid-body model (PRBM) to predict the behavior of the BSCM is presented. The new model was used to analyze seven different versions of the device, each with a different compliant joint length. The new model, which adds torsion, is compared with a finite element analysis (FEA) beam model. The new model more closely approximates the results yielded by FEA than previous models used to analyze the BSCM. Future work is needed to quantify stress-stiffening interactions between bending and torsion. Both FEA and the current models show that increasing the length of the compliant segment decreases the amount of force required to actuate the device.
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Richardson, Harvey John. "Theoretical studies of cross talk between InSb bistable elements." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/942.
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Qiu, Jin 1974. "An electrothermally-actuated bistable MEMS relay for power applications." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/8002.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. 91-92).
This thesis first develops a bistable mechanism that does not rely on internal stress or hinges for its bistability, which is then combined with transient electrothermal actuation and contact structure to develop a MEMS relay for power switching. The relay components, fabricated by a through etch of a silicon wafer using deep reactive ion etch (DRIE), move laterally in the plane of the wafer. The synthesis, analysis, design, fabrication and testing of the relay are all described in this thesis. The bistable mechanism comprises two parallel cosine curved clamped-clamped beams that are also clamped together at their centers. If designed properly it exhibits a second stable deflected shape that is nearly a mirror image of its as-fabricated shape mirrored through the centerline connecting its clamped ends. Both theoretical and finite-element analyses are applied to the modeling, design and optimization of the force-displacement characteristic of the curved beam mechanism. The analyses results agree well with experimental measurement after accounting for fabrication variations. If fabricated properly, the mechanism is mechanically robust; some mechanisms have been switched between their bistable states one million times without sign of failure. The bistable mechanism is combined with two contacts to form a crossbar relay. The contact structure is designed with flat shape and additional compliance; and proper metalization process is developed for its DRIE etched sidewalls; both contributing to a more reliable and low resistance contact. Because of bistability this relay requires no actuation power in either its on or off states. Therefore, transient electrothermal actuators to switch its states are designed, partially with a mechanical model developed for cantilevers subjected to both lateral and axial forces.
(cont.) These actuators typically require 1-ms 50-V pulses to switch the relay. In the off state, the relay contacts stand off more than 200 V. In the on state the best relay contacts exhibit a total resistance of 60 mfQ and a current carrying capacity of 3 A. The relay can switch at a maximum 5 Hz rate. These characteristics make it a good candidate for power protection applications.
by Jin Qiu.
Ph.D.
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Choi, Jang Wook Heath James R. "Bistable [2]rotaxane based molecular electronics : fundamentals and applications /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05242007-194737.
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Yeung, Fion Sze Yan. "Bistable twisted nematic liquid crystal display using photoalignment technology /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20YEUNG.
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Vigreux, Caroline. "Résonance Magnétique Electronique Bistable dans les solides : recherche de nouveaux matériaux et premiers pas vers la réalisation d'ensembles de systèmes bistables couplés." Paris 6, 1999. http://www.theses.fr/1999PA066521.
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La Résonance Magnétique Electronique Bistable (RMEB) est un des rares exemples de bistabilité d’une transition dans un système quantique à deux niveaux. Elle se traduit par une hystérésis du spectre RPE des électrons de conduction suivant le sens de variation du champ magnétique extérieur. Ce phénomène, lié à une bistabilité de l’interaction entre un rayonnement microonde et les spins des électrons de conduction (ou de donneurs) dans des matériaux conducteurs électroniques, a été mis en évidence au laboratoire il y a une dizaine d’années, dans Ga2O3 puis dans InP. Cependant, la théorie indique que c’est une propriété générale des solides conducteurs. Le premier objectif de ce travail a donc consisté à rechercher d’autres matériaux bistables afin de vérifier la généralité de ce phénomène. L’étude des solutions solides Ga2-2xIn2xO3, pour lesquelles la RMEB est faible voire inexistante, a montré que le phénomène dépend étroitement de la cristallinité, de l’homogénéité et de la structure électronique du solide. Et l’étude des particules de lithium métallique a confirmé que le phénomène peut exister dans les métaux purs et non pas seulement dans des semi-conducteurs, et montré que les spectres RPE sont très sensibles à l’état d’agrégation du lithium. Une autre partie de mon travail de thèse a consisté à étudier des ensembles de systèmes bistables couplés, afin d’explorer la possibilité de propriétés nouvelles dérivant de la RMEB. Des manifestations des couplages ont pu être prédites et observées dans deux cas, celui d’un couple de systèmes bistables provenant d’un cristal de Ga2O3 maclé et celui d’un ensemble continu de systèmes couplés obtenu par application d’un gradient de champ magnétique à un monocristal de Ga2O3
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Jensen, Brian D. "Identification of Macro- and Micro-Compliant Mechanism Configurations Resulting in Bistable Behavior." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/83.
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The purpose of this research is to identify the configurations of several mechanism classes which result in bistable behavior. Bistable mechanisms have use in many applications, such as switches, clasps, closures, hinges, and so on. A powerful method for the design of such mechanisms would allow the realization of working designs much more easily than has been possible in the past. A method for the design of bistable mechanisms is especially needed for micro-electro-mechanical systems (MEMS) because fabrication and material constraints often prevent the use of simple, well-known bistable mechanism configurations. In addition, this knowledge allows designers to take advantage of the many benefits of compliant echanisms, especially their ability to store and release energy in their moving segments. Therefore, an analysis of a variety of mechanism classes has been performed to determine the configurations of compliant segments or rigid-body springs in a mechanism which result in bistable behavior. The analysis revealed a relationship between the placement of compliant segments and the stability characteristics of the mechanism which allows either analysis or synthesis of bistable mechanisms to be performed very easily. Using this knowledge, a method of type synthesis for bistable mechanisms has been developed which allows bistable mechanisms to be easily synthesized. Several design examples have been presented which demonstrate the method. The theory has also been applied to the design of several bistable micromechanisms. In the process of searching for usable designs for micro-bistable mechanisms, a mechanism class was defined, known as "Young" mechanisms, which represent a feasible and useful way of achieving micro-mechanism motion similar to that of any four-bar mechanism. Based on this class, several bistable micro-mechanisms were designed and fabricated. Testing demonstrated the ability of the mechanisms to snap between the two stable states. In addition, the mechanisms showed a high degree of repeatability in their stable positions.