Stability and Bifurcations of Nonlinear Multibody Systems

1993 ◽  
Vol 46 (11S) ◽  
pp. S156-S159
Author(s):  
Edwin J. Kreuzer
Keyword(s):  
Multibody Systems ◽  
Qualitative Behavior ◽  
State Behavior ◽  
Bifurcation Phenomena ◽  
Nonlinear Mathematical Models ◽  
Mechanical Models ◽  
Stability And Bifurcations ◽  
Local And Global Bifurcations ◽  
Dynamics Problems

Many technical systems are adequately described only by means of nonlinear mathematical models. Multibody systems became the most important mechanical models for analyzing engineering dynamics problems. The long-term or steady-state behavior of such systems can have a periodic, quasi-periodic, or chaotic character. Changes of the qualitative behavior are characterized by local and global bifurcations. This paper deals with stability problems in multibody system dynamics and explains different bifurcation phenomena as well as methods for analyzing them. Results from a simple oscillator prove the applicability of the methods.

Knowing the Adversary

2014 ◽  
Author(s):  
Keren Yarhi-Milo
Keyword(s):  
Cold War ◽  
Decision Makers ◽  
Organizational Dynamics ◽  
Crucial Importance ◽  
State Behavior ◽  
Affective Factors ◽  
Cognitive And Affective Factors ◽  
The Cold War ◽  
The Military

States are more likely to engage in risky and destabilizing actions such as military build-ups and preemptive strikes if they believe their adversaries pose a tangible threat. Yet despite the crucial importance of this issue, we don’t know enough about how states and their leaders draw inferences about their adversaries’ long-term intentions. This book draws on a wealth of historical archival evidence to shed new light on how world leaders and intelligence organizations actually make these intentions assessments. The book examines three cases: Britain’s assessments of Nazi Germany’s intentions in the 1930s, America’s assessments of the Soviet Union’s intentions during the Carter administration, and the Reagan administration’s assessments of Soviet intentions near the end of the Cold War. The book advances a new theoretical framework—called selective attention—that emphasizes organizational dynamics, personal diplomatic interactions, and cognitive and affective factors. It finds that decision makers don’t pay as much attention to those aspects of state behavior that major theories of international politics claim they do. Instead, they tend to determine the intentions of adversaries on the basis of preexisting beliefs, theories, and personal impressions. The book also shows how intelligence organizations rely on very different indicators than decision makers, focusing more on changes in the military capabilities of adversaries. The book provides a clearer picture of the historical validity of existing theories, and broadens our understanding of the important role that diplomacy plays in international security.

High-State/Low-State Behavior in the Long-Term Light Curve of V Sagittae

1997 ◽  
Vol 113 ◽  
pp. 787 ◽  
Author(s):  
Jeff W. Robertson ◽  
R. Kent Honeycutt ◽  
Jeffrey R. Pier
Keyword(s):  
Light Curve ◽  
High State ◽  
State Behavior

Fore-arc building and destruction: a critical interplay between fluid flow, megathrust strength and tectonic underplating

2020 ◽  
Author(s):  
Armel Menant ◽  
Samuel Angiboust ◽  
Taras Gerya ◽  
Robin Lacassin ◽  
Martine Simoes ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Fluid Distribution ◽  
Plate Interface ◽  
Erosion Processes ◽  
Active Margins ◽  
Mechanical Models ◽  
Mass Transfers ◽  
High Topography ◽  
Critical Process

<p>Subduction zones are the loci of huge mass transfers, including accretion and erosion processes responsible for the long-term formation (and destruction) of fore-arc margins. Study of now-exhumed deep portions of the fore-arc crust revealed km-scale tectonic units of marine sediments and oceanic crust, which have been underplated (i.e. basally accreted) to the overriding plate. However, geophysical observations of this deep process in active subduction zones are unclear and the dynamics of tectonic underplating, as well as its existence, along most of active margins remain controversial. We attempt to shed light on this critical process from the plate interface where tectonic slicing is triggered, to the surface where topographic variations are expected in response to such a mass transfer.</p><p>Using high-resolution visco-elasto-plastic thermo-mechanical models, we present with unprecedented details the dynamics of formation, preservation and destruction of underplated crustal nappes at 10-40-km depth in subductions zones. Our results show that subduction segments exhibiting an increasing frictional behaviour control deep accretionary dynamics and that the long-term frictional zonation of the plate interface is stable due to a positive feedback between fluid distribution and effective stress. As a result, discrete underplating events follow one after another for tens of Myr, leading to the formation of a thick duplex structure supporting a coastal topographic high. The rise of this high topography is cadenced by Myr-scale uplift-then-subsidence cycles, characterising each underplating event and the subsequent period of wedge re-equilibration. This periodical evolution is significantly modified by changing the rheological properties of the material entering the subduction zone, suggesting that tectonic underplating is likely a transient process active along most of active margins, depending on severe variations of the hydro-mechanical properties of the plate interface at Myr timescale.</p>

Conclusion

2019 ◽  
pp. 157-170
Author(s):  
Yelena Biberman
Keyword(s):  
South Asian ◽  
Unintended Consequences ◽  
Policy Implications ◽  
Future Research ◽  
Humanitarian Law ◽  
State Behavior ◽  
Asian Security ◽  
Military Commanders ◽  
Scholarly Attention

This chapter summarizes the book’s key findings. It then considers the policy implications, directions for future research, and lessons for South Asian security. The chapter makes a recommendation to military commanders to abstain from outsourcing violence. Weaponizing civilians and former combatants is unethical and violates international humanitarian law. It is also of questionable long-term value. In all of the cases examined in this book, the victories states achieved with the help of nonstate allies were either ephemeral or incomplete. The chapter also calls for greater scholarly attention to changes in actors’ motivations, covert and illicit state behavior, and the problem of chance. It concludes by highlighting three powerful narratives the book challenges about South Asian security: (1) Pakistan’s uniqueness in outsourcing violence; (2) India as a model great power; and (3) the ability of powerful states to manage their allies in foreign-led counterinsurgencies while avoiding serious backlash and unintended consequences.

scholarly journals Hybrid Methods for Studying Stability and Bifurcations in Delayed Feedback Systems

2019 ◽  
Vol 29 (12) ◽  
pp. 1950167
Author(s):  
Griselda R. Itovich ◽  
Franco S. Gentile ◽  
Jorge L. Moiola
Keyword(s):  
System Approach ◽  
Hybrid Methods ◽  
Polynomial Equation ◽  
Feedback System ◽  
Feedback Systems ◽  
Bifurcation Phenomena ◽  
Classical Technique ◽  
Stability And Bifurcations ◽  
The Time Domain ◽  
Delay Differential

The dynamics of two related models of second order delay differential equations with four bifurcating parameters are analyzed. Through a classical technique in the time domain which involves the location of the roots of an exponential polynomial equation, the areas of stability of the equilibrium are set. A frequency-domain methodology is applied to study the Hopf bifurcation phenomena and to describe the behavior of the emerging cycles completely via a feedback system approach. Certain types of singularities, which provoke fold bifurcations of cycles are detected precisely. Also, a complete picture of parameter configurations to produce resonances is established for both models. All results are checked with the software DDE-Biftool.

scholarly journals Fine-Tune Robust Optimization

2020 ◽  
Author(s):  
Alexandre Cesar Balbino Barbosa Filho ◽  
Sergio Mauro da Silva Neiro
Keyword(s):  
Robust Optimization ◽  
Statistical Treatment ◽  
Mathematical Approach ◽  
Optimization Framework ◽  
Nonlinear Mathematical Models ◽  
Wide Range ◽  
Linear And Nonlinear ◽  
And Performance ◽  
Fine Tune

A Robust Optimization framework with original concepts and fundamentals also admitting a fusion of ideals from relative regret models and static robust optimization, containing conservatism concepts is disclosed. The algorithm uses a fine-tune strategy to tune the model so the robustness and a target ideality can be mutually achieved with a specified risk. The framework comprises original concepts, a mathematical approach and an algorithm. The statistical treatment of the data with the original concepts from the framework make it able to make short, middle or long-term decision-making setting. The framework has high tractability since the algorithm forces the creation of a setting that makes a robust optimization with the specified risk. The framework can be applied in linear and nonlinear mathematical models since that the objective function is monotonic in the domain of the active convex region. Several examples are solved to best understand the framework and all results demonstrated high tractability and performance. There is a wide range of applications. Along all the text, there is a profound discussion about its philosophy, objective, original concepts, fields of application, statistical and probabilistic fundamentals.

The Sliding Velocity Flow of Rough Collisions in Multibody Systems

1996 ◽  
Vol 63 (3) ◽  
pp. 804-809 ◽  
Author(s):  
J. A. Batlle
Keyword(s):  
Multibody Systems ◽  
Single Point ◽  
Nonlinear Flow ◽  
Qualitative Behavior ◽  
Sliding Velocity ◽  
Collision Point ◽  
Coulomb’S Friction ◽  
Tangential Stiffness ◽  
Velocity Flow ◽  
Phase Space Geometry

Single-point rough collisions in multibody systems with perfect constraints, under the assumptions of Coulomb’s friction and infinite tangential stiffness at the collision point, require usually an integration over the normal impulse. The evolution of the sliding velocity, which is needed in the integration, is determined by an autonomous nonlinear flow. The phase-space geometry of this flow depends upon five parameters associated with the system collision configuration and the friction coefficient μ, and gives a global picture of the system behavior in collisions with the configuration considered and arbitrary initial velocities. This geometry is studied using μ, as a control parameter, and a set of threshold values of μ, associated with changes in qualitative behavior are determined.

scholarly journals Modelling of Coupled Shrinkage and Creep in Multiphase Formulations for Hardening Concrete

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1745
Author(s):  
Peter Gamnitzer ◽  
Andreas Brugger ◽  
Martin Drexel ◽  
Günter Hofstetter
Keyword(s):  
Viscous Flow ◽  
Effective Stress ◽  
Drying Shrinkage ◽  
Shrinkage Strain ◽  
Viscoelastic Creep ◽  
Limit Value ◽  
Shrinkage And Creep ◽  
Mechanical Models ◽  
Term Response

The durability and serviceability of concrete structures is influenced by both the early-age behavior of concrete as well as its long-term response in terms of shrinkage and creep. Hygro-thermo-chemo-mechanical models, as they are used in the present publication, offer the possibility to consistently model the behavior of concrete from the first hours to several years. However, shortcomings of the formulation based on effective stress, which is usually employed in such multiphase models, were identified. As a remedy, two alternative formulations with a different coupling of shrinkage and creep are proposed in the present publication. Both assume viscous flow creep to be driven by total stress instead of effective stress, while viscoelastic creep is driven either by total or effective stress. Therefore, in contrast to the formulation based on effective stress, they predict a limit value for shrinkage as observed in long-term drying shrinkage tests. Shrinkage parameters for the new formulations are calibrated based on drying shrinkage data obtained from thin slices. The calibration process is straightforward for the new formulations since they decouple shrinkage and viscous flow creep. The different formulations are compared using results from shrinkage tests on sealed and unsealed cylindrical specimens. Shrinkage strain predictions are significantly improved by the new formulations.

Transient Thermal Creep at Moderate Temperature

2016 ◽  
Vol 711 ◽  
pp. 885-891 ◽  
Author(s):  
Hugo Cagnon ◽  
Thierry Vidal ◽  
Alain Sellier ◽  
Jean Michel Torrenti
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Thermal Creep ◽  
Nuclear Wastes ◽  
National Agency ◽  
In Situ Conditions ◽  
Deep Geological Disposal ◽  
Mechanical Models ◽  
Transient Thermal

The Cigéo project initiated by Andra (the French national agency for nuclear wastes management) concerns a deep geological disposal situated in an impermeable layer of clay approximately 500 m under ground. The High Performance Concrete (HPC) galleries will allow Intermediate Level Long-Life Nuclear Wastes to be stored. These exothermic radioactive wastes will induce a temperature rise which may reach 70°C. The very few studies that have investigated the effect of temperatures below 100°C on concrete behaviour have shown that temperature amplifies long-term deformations more than instantaneous ones. The present paper deals with the dimensional variations of HPC when subjected to temperature changes in sealed conditions. The aim is to provide accurate data to understand the causes of transient thermal creep. These experimental data may allow Thermo-Hydro-Mechanical models to be improved and thus provide accurate prediction of concrete long term behavior in such in situ conditions.

scholarly journals Qualitative effects of introducing nonlinear birth and death rates for the predator in a predator-prey type model

BIOMATH ◽  
2017 ◽  
Vol 6 (1) ◽  
pp. 1703167
Author(s):  
Tihomir B. Ivanov ◽  
Neli S. Dimitrova
Keyword(s):  
Equilibrium Points ◽  
Classical Model ◽  
Uniform Boundedness ◽  
Prey Type ◽  
Type Model ◽  
Qualitative Behavior ◽  
Death Rates ◽  
Predator Prey ◽  
Stability And Bifurcations ◽  
Predator Behavior

In this paper, we study how introducing nonlinear birth and death rates for the predator might affect the qualitative behavior of a mathematical model, describing predator-prey systems. We base our investigations on a known model, exhibiting anti-predator behavior. We propose a generalization of the latter by introducing generic birth and death rates for the predator and study the dynamics of the resulting system. We establish existence and uniqueness of positive model solutions, their uniform boundedness, existence, local stability and bifurcations of equilibrium points as well as global stability properties of the solutions. Most of the solution properties are demonstrated numerically and graphically by various numerical examples. Based on the obtained results, we show that the model with nonlinear birth and death rates can describe a much more complex behavior of the predator-prey system than the classical model (i.e., with linear rates) does.

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