Relevant bibliographies by topics / Invariance to external perturbations

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  2. Dissertations / Theses
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Academic literature on the topic 'Invariance to external perturbations'

Author: Grafiati
Published: 30 May 2022
Last updated: 31 May 2022

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Journal articles on the topic "Invariance to external perturbations"

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Shu, Hai, and Hongtu Zhu. "Sensitivity Analysis of Deep Neural Networks." Proceedings of the AAAI Conference on Artificial Intelligence 33 (July 17, 2019): 4943–50. http://dx.doi.org/10.1609/aaai.v33i01.33014943.

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Deep neural networks (DNNs) have achieved superior performance in various prediction tasks, but can be very vulnerable to adversarial examples or perturbations. Therefore, it is crucial to measure the sensitivity of DNNs to various forms of perturbations in real applications. We introduce a novel perturbation manifold and its associated influence measure to quantify the effects of various perturbations on DNN classifiers. Such perturbations include various external and internal perturbations to input samples and network parameters. The proposed measure is motivated by information geometry and provides desirable invariance properties. We demonstrate that our influence measure is useful for four model building tasks: detecting potential ‘outliers’, analyzing the sensitivity of model architectures, comparing network sensitivity between training and test sets, and locating vulnerable areas. Experiments show reasonably good performance of the proposed measure for the popular DNN models ResNet50 and DenseNet121 on CIFAR10 and MNIST datasets.
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Bruhn, B., and B. P. Koch. "Heteroclinic Bifurcations and Invariant Manifolds in Rocking Block Dynamics." Zeitschrift für Naturforschung A 46, no. 6 (June 1, 1991): 481–90. http://dx.doi.org/10.1515/zna-1991-0603.

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Abstract A simple model of rigid block motion under the influence of external perturbations is discussed. For periodic forcings we prove the existence of Smale horseshoe chaos in the dynamics. For slender blocks a heteroclinic bifurcation condition is calculated exactly, i.e. without using perturbation methods. That means that our results are valid for arbitrary excitation amplitudes. Furthermore, analytical formulas for the first pieces of the stable and unstable manifolds are derived not only for periodically but also for transiently driven systems. In the case of small excitation and damping the Melnikov method is used to treat the full nonlinear problem
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Meng, Bo, Cun Chen Gao, and Shu Hong Tang. "Adaptive Variable Structure Control for Uncertain Linear Time-Invariant Delay Singular Systems." Advanced Materials Research 433-440 (January 2012): 3734–40. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.3734.

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This paper discusses the control problems of singular linear time-invariant delay systems with uncertainties. A new adaptive variable structure control strategy is given by Lyapunov stability theory. The invariance of sliding mode is proved in the circumstances of the external disturbance and parameter perturbation with matching conditions. Through memory and memoryless of the linear state feedback, the control strategy ensure that system reaches sliding mode in finite time and the closed-loop system is global asymptotic stable. Simulation results further show that the strategy is feasible and effective.
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PARESCHI, FABIO, RICCARDO ROVATTI, and GIANLUCA SETTI. "PERIODICITY AS CONDITION TO NOISE ROBUSTNESS FOR CHAOTIC MAPS WITH PIECEWISE CONSTANT INVARIANT DENSITY." International Journal of Bifurcation and Chaos 16, no. 11 (November 2006): 3391–400. http://dx.doi.org/10.1142/s0218127406016872.

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Chaotic maps represent an effective method of generating random-like sequences, that combines the benefits of relying on simple, causal models with good unpredictability. However, since chaotic maps behavior is generally strongly dependent on unavoidable implementation errors and external perturbations, the possibility of guaranteeing map statistical robustness is of great practical concern. Here we present a technique to guarantee the independence of the first-order statistics of external perturbations, modeled as an additive, map-independent random variable. The developed criterion applies to a quite general class of maps.
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Omrani, Mohsen, J. Andrew Pruszynski, Chantelle D. Murnaghan, and Stephen H. Scott. "Perturbation-evoked responses in primary motor cortex are modulated by behavioral context." Journal of Neurophysiology 112, no. 11 (December 1, 2014): 2985–3000. http://dx.doi.org/10.1152/jn.00270.2014.

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Corrective responses to external perturbations are sensitive to the behavioral task being performed. It is believed that primary motor cortex (M1) forms part of a transcortical pathway that contributes to this sensitivity. Previous work has identified two distinct phases in the perturbation response of M1 neurons, an initial response starting ∼20 ms after perturbation onset that does not depend on the intended motor action and a task-dependent response that begins ∼40 ms after perturbation onset. However, this invariant initial response may reflect ongoing postural control or a task-independent response to the perturbation. The present study tested these two possibilities by examining if being engaged in an ongoing postural task before perturbation onset modulated the initial perturbation response in M1. Specifically, mechanical perturbations were applied to the shoulder and/or elbow while the monkey maintained its hand at a central target or when it was watching a movie and not required to respond to the perturbation. As expected, corrective movements, muscle stretch responses, and M1 population activity in the late perturbation epoch were all significantly diminished in the movie task. Strikingly, initial perturbation responses (<40 ms postperturbation) remained the same across tasks, suggesting that the initial phase of M1 activity constitutes a task-independent response that is sensitive to the properties of the mechanical perturbation but not the goal of the ongoing motor task.
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Wexler, Mark, Marianne Duyck, and Pascal Mamassian. "Persistent states in vision break universality and time invariance." Proceedings of the National Academy of Sciences 112, no. 48 (November 16, 2015): 14990–95. http://dx.doi.org/10.1073/pnas.1508847112.

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Studies of perception usually emphasize processes that are largely universal across observers and—except for short-term fluctuations—stationary over time. Here we test the universality and stationarity assumptions with two families of ambiguous visual stimuli. Each stimulus can be perceived in two different ways, parameterized by two opposite directions from a continuous circular variable. A large-sample study showed that almost all observers have preferred directions or biases, with directions lying within 90 degrees of the bias direction nearly always perceived and opposite directions almost never perceived. The biases differ dramatically from one observer to the next, and although nearly every bias direction occurs in the population, the population distributions of the biases are nonuniform, featuring asymmetric peaks in the cardinal directions. The biases for the two families of stimuli are independent and have distinct population distributions. Following external perturbations and spontaneous fluctuations, the biases decay over tens of seconds toward their initial values. Persistent changes in the biases are found on time scales of several minutes to 1 hour. On scales of days to months, the biases undergo a variety of dynamical processes such as drifts, jumps, and oscillations. The global statistics of a majority of these long-term time series are well modeled as random walk processes. The measurable fluctuations of these hitherto unknown degrees of freedom show that the assumptions of universality and stationarity in perception may be unwarranted and that models of perception must include both directly observable variables as well as covert, persistent states.
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Meinshausen, Nicolai, Alain Hauser, Joris M. Mooij, Jonas Peters, Philip Versteeg, and Peter Bühlmann. "Methods for causal inference from gene perturbation experiments and validation." Proceedings of the National Academy of Sciences 113, no. 27 (July 5, 2016): 7361–68. http://dx.doi.org/10.1073/pnas.1510493113.

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Inferring causal effects from observational and interventional data is a highly desirable but ambitious goal. Many of the computational and statistical methods are plagued by fundamental identifiability issues, instability, and unreliable performance, especially for large-scale systems with many measured variables. We present software and provide some validation of a recently developed methodology based on an invariance principle, called invariant causal prediction (ICP). The ICP method quantifies confidence probabilities for inferring causal structures and thus leads to more reliable and confirmatory statements for causal relations and predictions of external intervention effects. We validate the ICP method and some other procedures using large-scale genome-wide gene perturbation experiments in Saccharomyces cerevisiae. The results suggest that prediction and prioritization of future experimental interventions, such as gene deletions, can be improved by using our statistical inference techniques.
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Lebedeva, Т. Т., N. V. Semenova, and T. I. Sergienko. "Stability by the vector criterion of a mixed integer optimization problem with quadratic criterial fun ctions." Reports of the National Academy of Sciences of Ukraine, no. 10 (October 2020): 15–21. http://dx.doi.org/10.15407/dopovidi2020.10.015.

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The article is devoted to the study of qualitative characteristics of different concepts of stability of vector problems of mixed-integer optimization, namely, to identifying the conditions under which the set of Pareto-optimal solutions of the problem possesses some property of invariance defined in advance in relation to the external influences on initial data of the problem. We investigate the questions of stability with respect to data perturbations in a vector criterion of mixed-integer optimization problem. The necessary and sufficient conditions of stability of three types for a problem of finding the solutions of the Pareto set are found. Such conditions guarantee that the small variations of initial data of vector criterion: 1) do not result in new Paretooptimal solutions, 2) save all Pareto-optimal solutions of the problem and can admit new solutions, 3) do not change the set of Pareto-optimal solutions of the initial problem.
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van der Kooij, Herman, and Erwin de Vlugt. "Postural Responses Evoked by Platform Pertubations Are Dominated by Continuous Feedback." Journal of Neurophysiology 98, no. 2 (August 2007): 730–43. http://dx.doi.org/10.1152/jn.00457.2006.

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Is human balance control dominated by time invariant continuous feedback mechanisms or do noncontinuous mechanisms play a significant role like intermittent control? The goal of this paper is to quantify how much of the postural responses evoked by pseudorandom external periodic perturbations can be explained by continuous time invariant feedback control. Nine healthy subjects participated in this study. Center of mass and ankle torque responses were elicited by periodic platform perturbations in forward-backward directions containing energy in the 0.06- to 4.5-Hz frequency band. Subjects had their eyes open (EO) or eyes closed (EC). Responses were decomposed into a periodic component and a remnant (stochastic) component using spectral analysis. It is concluded that periodic responses can explain most of the evoked responses, although the remnant power spectral densities (PSDs) were significant especially for slow responses (<0.2 Hz) and largest for EC. The found remnant PSD did depend on the sensory condition but not on the platform perturbation amplitude. The ratio of the body sway and ankle torque remnant PSD reflects the body dynamics. Both findings are consistent with the idea that estimation of body orientation is part of a continuous feedback loop and that (stochastic) estimation errors increase when one source of sensory information is removed. The findings are not consistent with the idea that discrete or discontinuous intermittent feedback mechanisms significantly shape postural responses.
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Vignoni, Alejandro, Fabricio Garelli, and Jesús Picó. "Sliding Mode Reference Coordination of Constrained Feedback Systems." Mathematical Problems in Engineering 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/764348.

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This paper addresses the problem of coordinating dynamical systems with possibly different dynamics (e.g., linear and nonlinear, different orders, constraints, etc.) to achieve some desired collective behavior under the constraints and capabilities of each system. To this end, we develop a new methodology based on reference conditioning techniques using geometric set invariance and sliding mode control: the sliding mode reference coordination (SMRCoord). The main idea is to coordinate the systems references. Starting from a general framework, we propose two approaches: a local one through direct interactions between the different systems by sharing and conditioning their own references and a global centralized one, where a central node makes decisions using information coming from the systems references. In particular, in this work we focus in implementation on multivariable systems like unmanned aerial vehicles (UAVs) and robustness to external perturbations. To show the applicability of the approach, the problem of coordinating UAVs with input constraints is addressed as a particular case of multivariable reference coordination with both global and local configuration.
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Dissertations / Theses on the topic "Invariance to external perturbations"

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Лазаренко, Артем Александрович. "Синтез и разработка инвариантных систем стабилизации основного вооружения танков." Thesis, НТУ "ХПИ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22727.

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Диссертация на соискание ученой степени кандидата технических наук по специальности 05.13.03 – системы и процессы управления. – Национальный технический университет "Харьковский политехнический институт", Харьков – 2016. Диссертация посвящена разработке аналоговых и цифровых инвариантных систем наведения и стабилизации основного вооружения танков на основе создания математических моделей возмущенного движения танковой пушки относительно оси цапф и танковой башни с пушкой относительно оси поворота, а также имитационных моделей внешних возмущений, действующих на основное вооружение в каналах вертикального и горизонтального наведения. Показано, что повышение степени инвариантности замкнутой системы стабилизации к действию внешних возмущений, за счет объединения в стабилизаторе двух основных принципов управления – принципа управления по отклонению и принципа управления по возмущению, приводит к снижению запаса устойчивости замкнутой системы. Для сохранения требуемого запаса устойчивости предложено введение в систему дополнительного контура обратной связи по угловому ускорению объекта стабилизации. С использованием метода гармонической линеаризации нелинейностей решена задача отыскания амплитуд и частот автоколебаний рамок гироскопической платформы, используемой в качестве гироскопического датчика углов отклонения оси канала ствола танковой пушки от линии прицеливания, а также автоколебаний давления рабочей жидкости в гидросистеме стабилизатора канала вертикального наведения. Показано, что причиной возмущения автоколебаний в первом случае является нелинейная характеристика системы разгрузки гироплатформы и "сухое" трение в осях кардановых подвесов, а во втором случае – нелинейные характеристики предохранителей гидроклапанов. Сделан вывод о том, что такие автоколебания являются высокочастотной помехой, приводящей к снижению помехозащищенности замкнутой системы наведения и стабилизации. Рассмотрены особенности цифровой инвариантной системы стабилизации наведения и стабилизации танковой пушки, в частности, необходимость использование цифровых низкочастотных фильтров Баттеруорта и Ланцоша для фильтрации высокочастотных помех выходных сигналов датчиков. Доказано, что при построении цифрового стабилизатора танковой пушки целесообразно последовательно-параллельное использование цифровых фильтров Баттеруорта и Ланцоша. Разработана структура и осуществлен выбор варьируемых констант алгоритмов стабилизации, обеспечивающих инвариантность замкнутой системы наведения и стабилизации без существенного снижения её запаса устойчивости. Моделирование процессов наведения и стабилизации в замкнутой системе с последующим анализом этих процессов позволяет сделать вывод о значительном повышении точности отработки внешнего возмущения (в 1.8 – 1.9 раз) по сравнению со штатной.
The thesis for the degree of candidate of technical sciences, specialty 05.13.03 – Systems and management processes. – National Technical University "Kharkov Polytechnic Institute", Kharkov – 2016. The thesis is dedicated to development analog and digital invariant guidance systems and stabilize the main armament of tanks through the creation of mathematical models perturbed motion tank gun relative to the axis of the pins and the tank tur ret gun relative to the axis of rotation, as well as simulation models of external disturbances acting on the main armament channels vertical and horizontal guidance. It is shown that increasing the degree of invariance closed stabilization system to external perturbations lead to lower stability margin closed system. To maintain the desired stability margin suggested the introduction of the system of additional feedback path for the angular acceleration of the object of stabilization. The features invariant digital stabilization system tank gun, including the need to use a digital low-pass filter Batteruorta and Lanczos filtering high frequency noise output signals of sensors. It is proved that the construction of a digital stabilizer tank cannon appropriate series-parallel use of digital filters Batteruorta and Lanczos. The structure created and the choice of variable constants stabilization algorithms was made that provide an invariance closed system of guidance and stabilization without significantly reducing its stability margin. Modeling of guidance and stabilization in a closed system with subsequent analysis of these processes suggests a significant increase in accuracy working off of external perturbation (at 1.8 – 1.9 times) compared with the standard.
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Лазаренко, Артем Олександрович. "Синтез і розробка інваріантних систем керування наведенням та стабілізацією основного озброєння танків." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22726.

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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.03 – системи і процеси керування. – Національний технічний університет "Харківський політехнічний інститут", Харків, – 2016. Дисертація присвячена розробці аналогових і цифрових інваріантних систем наведення і стабілізації основного озброєння танків на основі створення математичних моделей збуреного руху танкової гармати відносно вісі цапф і танкової башти з гарматою відносно вісі повороту, а також імітаційних моделей зовнішніх збурень, що діють на основне озброєння в каналах вертикального і горизонтального наведення. Показано, що підвищення ступеня інваріантності замкненої системи стабілізації до дії зовнішніх збурень приводить до зниження запасу стійкості замкненої системи. Для збереження потрібного запасу стійкості запропоновано введення до системи додаткового контуру зворотнього зв'язку за кутовим прискоренням об'єкту стабілізації. Розглянуті особливості цифрової інваріантної системи стабілізації танкової гармати, зокрема необхідність використання цифрових низькочастотних фільтрів Баттеруорта і Ланцоша для фільтрації високочастотних завад вихідних сигналів датчиків. Доведено, що при побудові цифрового стабілізатора танкової гармати доцільне послідовно-паралельне використання цифрових фільтрів Баттеруорта і Ланцоша. Розроблена структура і здійснений вибір варійованих констант алгоритмів стабілізації, які забезпечують інваріантність замкненої системи наведення і стабілізації без суттєвого зниження її запасу стійкості. Моделювання процесів наведення і стабілізації в замкненій системі з подальшим аналізом цих процесів дозволяє зробити висновок про значне підвищення точності відробки зовнішнього збурення (в 1.8 – 1.9 рази) у порівнянні зі штатною.
The thesis for the degree of candidate of technical sciences, specialty 05.13.03 – Systems and management processes. – National Technical University "Kharkov Polytechnic Institute", Kharkov – 2016. The thesis is dedicated to development analog and digital invariant guidance systems and stabilize the main armament of tanks through the creation of mathematical models perturbed motion tank gun relative to the axis of the pins and the tank tur ret gun relative to the axis of rotation, as well as simulation models of external disturbances acting on the main armament channels vertical and horizontal guidance. It is shown that increasing the degree of invariance closed stabilization system to external perturbations lead to lower stability margin closed system. To maintain the desired stability margin suggested the introduction of the system of additional feedback path for the angular acceleration of the object of stabilization. The features invariant digital stabilization system tank gun, including the need to use a digital low-pass filter Batteruorta and Lanczos filtering high frequency noise output signals of sensors. It is proved that the construction of a digital stabilizer tank cannon appropriate series-parallel use of digital filters Batteruorta and Lanczos. The structure created and the choice of variable constants stabilization algorithms was made that provide an invariance closed system of guidance and stabilization without significantly reducing its stability margin. Modeling of guidance and stabilization in a closed system with subsequent analysis of these processes suggests a significant increase in accuracy working off of external perturbation (at 1.8 – 1.9 times) compared with the standard.
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Zhang, Lei. "Rapid motor responses to external perturbations during reaching movements." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-184803.

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Pollock, Courtney L. "Motor control of response to external perturbations in people post-stroke." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51595.

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Mechanisms underpinning motor control of standing balance post-stroke remain unclear. Following stroke, ankle plantarflexor muscles demonstrate impairment associated with asymmetrical postural control and decreased balance. Stroke also results in increased attentional demands during challenges to standing balance. This thesis examined motor control impairment post-stroke from medial gastrocnemius motor units to the tri-muscle plantarflexor complex. Investigation of motor, kinematic and kinetic parameters of postural control during external perturbations in standing and associated levels of physiological arousal have furthered understanding of balance impairment post-stroke. Methods: Medial gastrocnemius motor units were recorded in controls (Chapter 2) and people post-stroke (Chapter 3) in standing as perturbations were sequentially applied at the pelvis under conditions of increased anteriorly-directed challenge. In both studies, motor unit firing rate was calculated during dynamic response to perturbation, and maintenance of steady state between perturbations. Joint kinematics, surface electromyography and movements of the centre of pressure were assessed. In Chapter 4, this methodology was expanded to cross-correlation analysis of electromyography activity of the three plantarflexor muscles with anterior-posterior centre of pressure during steady state. In Chapter 5, attentional demands surrounding timing of external perturbation were manipulated to investigate effects of stroke on physiological arousal and postural reactions. Results: In healthy subjects, medial gastrocnemius utilized primarily motor unit recruitment to maintain standing with a modest increase in motor unit firing rate only during the dynamic response to external perturbations. The paretic medial gastrocnemius also primarily used motor unit recruitment; however, lacked firing rate modulation during the dynamic response, albeit firing rate was related to kinematic variables of postural control. In people post-stroke, the three plantarflexors demonstrated asymmetrical motor control of postural sway between-legs but symmetry was improved under conditions of increased challenge to standing balance. Finally, knowledge of timing of perturbations did not decrease the heightened anticipatory postural strategy and level of physiological arousal exhibited post-stroke. Conclusions: This dissertation provides new understanding of motor control of standing balance post-stroke and reveals anticipatory postural strategies adopted post-stroke under conditions challenging balance. These findings implicate the importance of introducing challenge to standing balance post-stroke in the assessment and rehabilitation of postural control post-stroke.
Medicine, Faculty of
Graduate
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Cervantes, Chia Carlos Andres, and Weronika Maria Lewandowska. "Optical Characterization of Quantum-Dots-in-a-Well Infrared Photodetectors Under External Perturbations." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-1659.

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In this project we have used Fourier transform infrared spectroscopy to study the photoresponse of two different types of quantum dot-in-a-well infrared photodetectors (DWELL QDIPs). The basic task was to compare the photoresponse of these two detectors, and to study the influence of external resonant laser pumping on the photoresponse. Series of measurements were done at 77K. In the first measurements we investigated the photoresponse for different applied voltages at 77K.

In a second run of experiments, we used a 1064 nm infrared semiconductor laser to resonantly

pump the fundamental transition of the quantum dots. The results show that by using this

additional illumination the photoresponse was dramatically increased by creating additional

charge carriers in the quantum dots. This could be used to increase the sensitivity of infrared

detectors based on QDs.

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Asfaw, Teffera Mekonnen. "Topological Degree and Variational Inequality Theories for Pseudomonotone Perturbations of Maximal Monotone Operators." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4433.

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Let X be a real reflexive locally uniformly convex Banach space with locally uniformly convex dual space X* . Let G be a bounded open subset of X. Let T:X⊃ D(T)⇒ 2X* be maximal monotone and S: X ⇒ 2X* be bounded pseudomonotone and such that 0 notin cl((T+S)(D(T)∩partG)). Chapter 1 gives general introduction and mathematical prerequisites. In Chapter 2 we develop a homotopy invariance and uniqueness results for the degree theory constructed by Zhang and Chen for multivalued (S+) perturbations of maximal monotone operators. Chapter 3 is devoted to the construction of a new topological degree theory for the sum T+S with the degree mapping d(T+S,G,0) defined by d(T+S,G,0)=limepsilondarr 0+ dS+(T+S+ J,G,0), where dS+ is the degree for bounded (S+)-perturbations of maximal monotone operators. The uniqueness and homotopy invariance result of this degree mapping are also included herein. As applications of the theory, we give associated mapping theorems as well as degree theoretic proofs of known results by Figueiredo, Kenmochi and Le. In chapter 4, we consider T:X D(T)⇒ 2X* to be maximal monotone and S:D(S)=K⇒ 2X* at least pseudomonotone, where K is a nonempty, closed and convex subset of X with 0isinKordm. Let Phi:X⇒ ( infin, infin] be a proper, convex and lower-semicontinuous function. Let f* isin X* be fixed. New results are given concerning the solvability of perturbed variational inequalities for operators of the type T+S associated with the function f. The associated range results for nonlinear operators are also given, as well as extensions and/or improvements of known results by Kenmochi, Le, Browder, Browder and Hess, Figueiredo, Zhou, and others.
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Rainone, Corrado. "Following the evolution of metastable glassy states under external perturbations : compression and shear-strain." Thesis, Paris, Ecole normale supérieure, 2015. http://www.theses.fr/2015ENSU0051/document.

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On considère l'évolution adiabatique des états vitreux sous perturbations extérieures. Bien que le formalisme que nous utilisons soit très général, nous nous concentrons ici sur les sphères dures en dimension infinie où une analyse exacte est possible. Nous considérons perturbations de la frontière, notamment compression ou cisaillement simple et nous calculons la réponse des états vitreux à ces perturbations : pression et contrainte de cisaillement. Nous constatons un dépassement des deux quantités avant que l'état vitreux ne devienne instable à un point spinodal, où il fond dans le liquide (ou cède). Nous estimons également la limite d'élasticité du verre. Enfin, nous étudions la stabilité des bassins vitreux vers la rupture en sous-bassins, correspondant à une transition de Gardner. Nous constatons que près de la transition dynamique, les verres subissent une transition de Gardner après une perturbation infinitésimale. Nous étudions ensuite le régime de haute pression et haut cisaillement au-delà de la transition de Gardner
We consider the adiabatic evolution of glassy states under external perturbations. Although the formalism we use is very general, we focus here on infinite-dimensional hard spheres where an exact analysis is possible. We consider perturbations of the boundary, i. e. compression or (volume preserving) shear-strain, and we compute the response of glassy states to such perturbations: pressure and shear-stress. We find that both quantities over shoot before the glass state becomes unstable at a spinodal point where it melts into a liquid (or yields). We also estimate the yield stress of the glass. Finally, we study the stability of the glass basins towards breaking into sub-basins, corresponding to a Gardner transition. We find that close to the dynamical transition, glasses undergo a Gardner transition after an infinitesimal perturbation. We then study the high-pressure and high-strain regime beyond the Gardner transition
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TRABUCO, DOREA Carlos Eduardo. "Sur l'(A,B)-invariance de polyèdres convexes ; application à la commande sous contraintes et au problème l1." Phd thesis, Université Paul Sabatier - Toulouse III, 1997. http://tel.archives-ouvertes.fr/tel-00010088.

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Ce travail porte sur l'étude de la propriété d'(A,B)-invariance de polyèdres convexes et son application à la commande sous contraintes et au problème l 1. D'abord, nous proposons une caractérisation explicite de l'(A,B)-invariance de polyèdres convexes pour des systèmes en temps discret. Cette caractérisation se traduit par des conditions nécessaires et suffisantes sous la forme de relations matricielles linéaires, et présente deux avantages majeurs vis-à-vis de celles rencontrées dans la littérature : elle s'applique à tous les polyèdres convexes et elle ne nécessite pas le calcul de sommets. Ces avantages se font sentir notamment dans le calcul du domaine (A,B)-invariant suprémal inclus dans un polyèdre donné, pour lequel nous proposons une méthode numérique. Le problème de calculer une loi de commande rendant positivement invariant en boucle fermée un polyèdre (A,B)-invariant est également traité. Les relations d'(A,B)-invariance sont alors généralisées à des systèmes soumis à des contraintes linéaires sur la commande et à des systèmes soumis à des perturbations additives bornées. Puis, les résultats obtenus en temps discret sont étendus aux systèmes en temps continu. Ensuite, le problème d'atténuation de perturbations additives persistantes, connu dans la littérature comme problème l 1, est étudié. Les domaines (A,B)-invariants intérieurement stabilisables sont d'abord caractérisés. Puis, nous proposons une approche décomposée pour le calcul du domaine intérieurement stabilisable suprémal inclus dans le polyèdre défini par les contraintes de performance l 1. Un niveau de performance donné est atteignable si et seulement si ce domaine suprémal n'est pas vide. Cette approche géométrique permet notamment de déterminer directement la solution du problème l 1 pour une classe importante de systèmes. Enfin, nous étendons l'étude de l'(A,B)-invariance de polyèdres à des systèmes dont le modèle est soumis à des incertitudes d u type structuré.
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Zhang, Lei [Verfasser], and Andreas [Akademischer Betreuer] Straube. "Rapid motor responses to external perturbations during reaching movements : experimental results and modelling / Lei Zhang. Betreuer: Andreas Straube." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1076242987/34.

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Tokur, Dario Sinan [Verfasser], Andre [Akademischer Betreuer] Seyfarth, and David [Akademischer Betreuer] Lee. "Responses to External Perturbations in Selected Human Motor Tasks - A Systematic Review and Analysis. / Dario Sinan Tokur ; Andre Seyfarth, David Lee." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1201820480/34.

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Books on the topic "Invariance to external perturbations"

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Rainone, Corrado. Metastable Glassy States Under External Perturbations. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7.

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Rainone, Corrado. Metastable Glassy States Under External Perturbations: Monitoring the Effects of Compression and Shear-strain. Springer, 2017.

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Rainone, Corrado. Metastable Glassy States Under External Perturbations: Monitoring the Effects of Compression and Shear-strain. Springer, 2018.

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Deruelle, Nathalie, and Jean-Philippe Uzan. Matter in curved spacetime. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198786399.003.0043.

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This chapter is concerned with the laws of motion of matter—particles, fluids, or fields—in the presence of an external gravitational field. In accordance with the equivalence principle, this motion will be ‘free’. That is, it is constrained only by the geometry of the spacetime whose curvature represents the gravitation. The concepts of energy, momentum, and angular momentum follow from the invariance of the solutions of the equations of motion under spatio-temporal translations or rotations. The chapter shows how the action is transformed, no longer under a modification of the field configuration, but instead under a displacement or, in the ‘passive’ version, under a translation of the coordinate grid in the opposite direction.
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Taylor, Kenneth A. Referring to the World. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780195144741.001.0001.

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Our words and ideas refer to objects and properties in the external world; this phenomenon is central to thought, language, communication, and science. But great works of fiction are full of names that don’t seem to refer to anything! This book explores the myriad of problems that surround the phenomenon of reference. How can words in language and perturbations in our brains come to stand for external objects? Reference is essential to truth, but which is more basic: reference or truth? How can fictional characters play such an important role in imagination and literature, and how does this use of language connect with more mundane uses? The book develops a framework for understanding reference, and the theories that other thinkers—past and present—have developed about it. But it doesn’t simply tell us what others thought; the book is full of new ideas and analyses, making for a vital final contribution from a seminal philosopher.
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Launay, Jean-Pierre, and Michel Verdaguer. The localized electron: magnetic properties. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198814597.003.0002.

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After preliminaries about electron properties, and definitions in magnetism, one treats the magnetism of mononuclear complexes, in particular spin cross-over, showing the role of cooperativity and the sensitivity to external perturbations. Orbital interactions and exchange interaction are explained in binuclear model systems, using orbital overlap and orthogonality concepts to explain antiferromagnetic or ferromagnetic coupling. The phenomenologically useful Spin Hamiltonian is defined. The concepts are then applied to extended molecular magnetic systems, leading to molecular magnetic materials of various dimensionalities exhibiting bulk ferro- or ferrimagnetism. An illustration is provided by Prussian Blue analogues. Magnetic anisotropy is introduced. It is shown that in some cases, a slow relaxation of magnetization arises and gives rise to appealing single-ion magnets, single-molecule magnets or single-chain magnets, a route to store information at the molecular level.
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Glazov, M. M. Electron Spin Decoherence by Nuclei. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198807308.003.0007.

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The discussion of the electron spin decoherence and relaxation phenomena via the hyperfine interaction with host lattice spins is presented here. The spin relaxation processes processes limit the conservation time of spin states as well as the response time of the spin system to external perturbations. The central spin model, where the spin of charge carrier interacts with the bath of nuclear spins, is formulated. We also present different methods to calculate the spin dynamics within this model. Simple but physically transparent semiclassical treatment where the nuclear spins are considered as largely static classical magnetic moments is followed by more advanced quantum mechanical approach where the feedback of electron spin dynamics on the nuclei is taken into account. The chapter concludes with an overview of experimental data and its comparison with model calculations.
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Book chapters on the topic "Invariance to external perturbations"

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Álvarez, Miguel Dovale. "Isolation from External Perturbations." In Optical Cavities for Optical Atomic Clocks, Atom Interferometry and Gravitational-Wave Detection, 63–89. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-20863-9_3.

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Kita, Takafumi. "Responses to External Perturbations." In Statistical Mechanics of Superconductivity, 159–74. Tokyo: Springer Japan, 2015. http://dx.doi.org/10.1007/978-4-431-55405-9_11.

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Sólyom, Jenő. "Electronic Response to External Perturbations." In Fundamentals of the Physics of Solids, 61–138. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-04518-9_2.

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Osborn, Hugh. "Conformal Invariance with Boundaries." In Quantum Field Theory Under the Influence of External Conditions, 24–33. Wiesbaden: Vieweg+Teubner Verlag, 1996. http://dx.doi.org/10.1007/978-3-663-01204-7_2.

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Rainone, Corrado. "Introduction." In Metastable Glassy States Under External Perturbations, 1–18. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7_1.

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Rainone, Corrado. "From Supercooled Liquids to RFOT." In Metastable Glassy States Under External Perturbations, 19–47. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7_2.

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Rainone, Corrado. "Metastable Glasses." In Metastable Glassy States Under External Perturbations, 49–83. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7_3.

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Rainone, Corrado. "The State Following Construction." In Metastable Glassy States Under External Perturbations, 85–97. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7_4.

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Rainone, Corrado. "The Replica Symmetric Ansatz." In Metastable Glassy States Under External Perturbations, 99–125. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7_5.

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Rainone, Corrado. "The Full Replica Symmetry Breaking Ansatz." In Metastable Glassy States Under External Perturbations, 127–43. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60423-7_6.

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Conference papers on the topic "Invariance to external perturbations"

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Han, Qinkai, and Fulei Chu. "Unbalanced Response of Cracked Rotor-Bearing System Under Time-Dependent Base Movements." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62637.

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Unbalanced response of cracked rotor-bearing system under time-dependent base movements is studied in this paper. Three base angular motions, including the rolling, pitching and yawing motions, are assumed to be sinusoidal perturbations superimposed upon constant terms. Both the open and breathing transverse cracks are considered in the analysis. The finite element model is established for the base excited rotor-bearing system with open or breathing cracks. Considering the time-varying base movements and transverse cracks, the second order differential equations of the system will not only have time-periodic gyroscopic and stiffness coefficients, but also the multi-frequency external excitations. An improved harmonic balance method is introduced to obtain the steady-state response of the system under both base and unbalance excitations. The whirling frequencies of the equivalent time-invariant system, orbits of shaft center, response spectra and frequency response characteristics, are analyzed accordingly. The effects of various base angular motions, frequency and amplitude of base excitations, and crack depths on the system dynamic behaviors are considered in the discussions.
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Okulov, A. Yu. "Spiral cold atomic ensemble under external perturbations." In Conference on Coherence and Quantum Optics. Washington, D.C.: OSA, 2019. http://dx.doi.org/10.1364/cqo.2019.th2a.5.

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Redkar, Sangram, and S. C. Sinha. "Order Reduction of Nonlinear Systems Subjected to an External Periodic Excitation." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82354.

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In this work, the basic problem of order reduction nonlinear systems subjected to an external periodic excitation is considered. This problem deserves attention because the modes that interact (linearly or nonlinearly) with the external excitation dominate the response. A linear approach like the Guyan reduction does not always guarantee accurate results, particularly when nonlinear interactions are strong. In order to overcome limitations of the linear approach, a nonlinear order reduction methodology through a generalization of the invariant manifold technique is proposed. Traditionally, the invariant manifold techniques for unforced problems are extended to the forced problems by ‘augmenting’ the state space, i.e., forcing is treated as an additional degree of freedom and an invariant manifold is constructed. However, in the approach suggested here a nonlinear time-dependent relationship between the dominant and the non-dominant states is assumed and the dimension of the state space remains the same. This methodology not only yields accurate reduced order models but also explains the consequences of various ‘primary’ and ‘secondary resonances’ present in the system. Following this approach, various ‘reducibility conditions’ are obtained that show interactions among the eigenvalues, the nonlinearities and the external excitation. One can also recover all ‘resonance conditions’ commonly obtained via perturbation or averaging techniques. These methodologies are applied to some typical problems and results for large-scale and reduced order models are compared. It is anticipated that these techniques will provide a useful tool in the analysis and control of large-scale externally excited nonlinear systems.
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Gabale, Amit P., and S. C. Sinha. "A Direct Analysis of Nonlinear Systems With External Periodic Excitations Via Normal Forms." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-35062.

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This study presents a direct methodology for the analysis of nonlinear dynamic systems with external periodic forcing via an application of the theory of normal forms. Rather than introducing a new state variable to reduce the problem to a homogenous one, we apply a set of time-dependant near-identity transformations to construct the normal forms. The proposed method can be applied to time-invariant as well as time varying systems. After discussing the time-invariant case, the methodology is extended to systems with time-periodic coefficients. The time periodic case is handled through an application of the Lyapunov-Floquet (L-F) transformation. It has been shown that all resonance conditions can be obtained in a closed form. Further, for time invariant case, if the superharmonic response is dominant, a simple modification can be made to yield accurate results. An example for each type of system, viz., constant coefficients and time-varying coefficients is included to demonstrate effectiveness of the method. It is observed that the linear parametric excitation term need not be small as generally assumed in perturbation and averaging techniques. The results obtained by proposed method are compared with numerical solutions.
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Xia, Guang-Qiong, Tao Deng, and Zheng-Mao Wu. "Nonlinear dynamics of 1550nm VCSELs under external perturbations." In 2013 12th International Conference on Optical Communications and Networks (ICOCN). IEEE, 2013. http://dx.doi.org/10.1109/icocn.2013.6617203.

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Redkar, Sangram, and S. C. Sinha. "Order Reduction of Parametrically Excited Nonlinear Systems Subjected to External Periodic Excitations." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86886.

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In this work, some techniques for order reduction of nonlinear systems with periodic coefficients subjected to external periodic excitations are presented. The periodicity of the linear terms is assumed to be non-commensurate with the periodicity of forcing vector. The dynamical equations of motion are transformed using the Lyapunov-Floquet (L-F) transformation such that the linear parts of the resulting equations become time-invariant while the forcing and/or nonlinearity takes the form of quasiperiodic functions. The techniques proposed here; construct a reduced order equivalent system by expressing the non-dominant states as time-varying functions of the dominant (master) states. This reduced order model preserves stability properties and is easier to analyze, simulate and control since it consists of relatively small number of states in comparison with the large scale system. Specifically, two methods are outlined to obtain the reduced order model. First approach is a straightforward application of linear method similar to the ‘Guyan reduction’, the second novel technique proposed here, utilizes the concept of ‘invariant manifolds’ for the forced problem to construct the fundamental solution. Order reduction approach based on invariant manifold technique yields unique ‘reducibility conditions’. If these ‘reducibility conditions’ are satisfied only then an accurate order reduction via ‘invariant manifold’ is possible. This approach not only yields accurate reduced order models using the fundamental solution but also explains the consequences of various ‘primary’ and ‘secondary resonances’ present in the system. One can also recover ‘resonance conditions’ associated with the fundamental solution which could be obtained via perturbation techniques by assuming weak parametric excitation. This technique is capable of handing systems with strong parametric excitations subjected to periodic and quasi-periodic forcing. These methodologies are applied to a typical problem and results for large-scale and reduced order models are compared. It is anticipated that these techniques will provide a useful tool in the analysis and control system design of large-scale parametrically excited nonlinear systems subjected to external periodic excitations.
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Krasnova, Svetlana A. "Cascade Synthesis of External Perturbations Observers Based on Virtual Models." In 2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE). IEEE, 2018. http://dx.doi.org/10.1109/apeie.2018.8545125.

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Le Duigou, J. M., M. Barillot, Jean-Michel Réess, F. Hénault, G. Morinaud, J. P. Amans, M. Ollivier, et al. "PERSEE: a nulling interferometer with dynamic correction of external perturbations." In International Conference on Space Optics 2008, edited by Josiane Costeraste, Errico Armandillo, and Nikos Karafolas. SPIE, 2017. http://dx.doi.org/10.1117/12.2308245.

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Huusom, Jakob Kjobsted, Hakan Hjalmarsson, Niels Kjolestad Poulsen, and Sten Bay Jorgensen. "Improving convergence of Iterative Feedback Tuning using optimal external perturbations." In 2008 47th IEEE Conference on Decision and Control. IEEE, 2008. http://dx.doi.org/10.1109/cdc.2008.4738785.

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Kochetkov, Sergey A., Svetlana A. Krasnova, and Victor A. Utkin. "Tracking problem for electromechanical system under influence of external perturbations." In ICNPAA 2016 WORLD CONGRESS: 11th International Conference on Mathematical Problems in Engineering, Aerospace and Sciences. Author(s), 2017. http://dx.doi.org/10.1063/1.4972671.

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Reports on the topic "Invariance to external perturbations"

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Park, Jong-Kyu, Allen H. Boozer, Jonathan E. Menard, Stefan P. Gerhardt, and Steve A. Sabbagh. Shielding of External Magnetic Perturbations By Torque In Rotating Tokamak Plasmas. Office of Scientific and Technical Information (OSTI), August 2009. http://dx.doi.org/10.2172/963532.

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