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第24届中国控制与决策会议

作者： Shravan Mohan Gaurav raina the Department of Electrical Engineering Indian Institute of Technology Madras the Faculty of the Department of Electrical Engineering Indian Institute of Technology Madras

A key focus of this paper is on understanding stability in a non-linear circuit design subject to delayed feedback. The system we consider is an autonomous first order rC circuit, coupled with a non-linear element, with a fixed feedback delay. With time delays, stability is a key concern. So for the non-linear circuit model we first establish a sufficient condition for local stability. We then establish necessary and sufficient conditions for local stability. Additionally we also exhibit that when local stability is just lost, a Hopf type bifurcation would occur. For the non-linear system, this bifurcation signifies the emergence of limit cycles which can degrade performance. Practically, it is useful to obtain an estimate of the amplitude and frequency of the bifurcating periodic solutions. Such estimates are calculated using the method of harmonic balance. In addition to the local stability analysis, we also establish some global stability results and some conditions to ensure that the solutions of the governing non-linear system are bounded. Some of the theoretical insights obtained are complemented with numerical simulations and also with experiments which are carried out using off-the-shelf components. The combination of theory, both local and global, simulations and experiments serve to enhance our understanding of the underlying model.

关键词： Non-linear Circuit Time-delayed Feedback Stability Hopf Bifurcation Experiments.

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Local Hopf bifurcation analysis of logistic population dynamics models with two delays 26th

Local Hopf bifurcation analysis of logistic population dynam...

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第26届中国控制与决策会议

作者： Sreelakshmi Manjunath Gaurav raina Department of Electrical Engineering Indian Institute of Technology Madras

ISBN: (纸本)9781479937097

Multiple time lags can occur very naturally in the study of population dynamics. In this paper, we study two forms of the delay logistic equation with two discrete time *** both the models, we identify the condition for the first local Hopf bifurcation. For our analysis, we employ a non-dimensional bifurcation parameter. Using Poincar′e normal forms and the center manifold theory, we also conduct the requisite analysis to determine the type of the Hopf bifurcation. This enables us to determine the asymptotic orbital stability of the bifurcating periodic solutions. The analysis is complemented with some numerical examples and bifurcation diagrams.

关键词： Population dynamics logistic growth two delays stability Hopf bifurcation.

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Stability and Hopf bifurcation analysis of the Mackey-Glass and Lasota equations

Stability and Hopf bifurcation analysis of the Mackey-Glass ...

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第26届中国控制与决策会议

作者： Sreelakshmi Manjunath Gaurav raina Department of Electrical Engineering Indian Institute of Technology Madras

Time delays are an integral part of various physiological processes. In this paper, we analyse two models for physiological systems: the Mackey-Glass and Lasota equations. We first exhibit a sufficient condition to ensure local stability, and then outline the associated necessary and sufficient condition for stability. Using a non-dimensional bifurcation parameter, we then highlight that stability will be lost via a Hopf bifurcation. We also explicitly characterise the type of the Hopf bifurcation using Poincar′e normal forms and the center manifold theory. The theoretical analysis is complemented with some numerical examples, stability charts and bifurcation diagrams.

关键词： Physiological processes Mackey-Glass equation Lasota equation stability Hopf bifurcation

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Fragmentation Prediction in Different rock Masses Characterised by Drilling Index

Fragmentation Prediction in Different Rock Masses Characteri...

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The Seventh International Symposium on rock Fragmentation by Blasting

作者： raina A.k. ramulu M. Choudhury P.B. Dudhankar A. Chakraborty A.k. Central Mining research Institute Regional Centre 54-B Shankar Nagar Nagpur-440 010. India

rock mass has been characterised for many purposes like for drilling, blasting and support design. The characterisation has been normally done to indicate the overall rock mass behaviour against failure. The main objective is to have a simple method to characterise the rock mass including various properties and conditions and subsequently to develop indices or ratings that can be used to predict the failure condition. As rock mass failure in drilling strongly resembles to that in blasting, many researchers have used drilling parameters for rock mass characterisation in blasting. This paper discusses use of Drilling Index to calculate rock factor used in prediction of mean fragment size. An approach with this method has been discussed in light of the existing criteria.

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Non-linear oscillations in TCP networks with Drop-Tail buffers 25th

Non-linear oscillations in TCP networks with Drop-Tail buffe...

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第25届中国控制与决策会议

作者： Nizar Malangadan Haseen rahman Gaurav raina India-Uk Advanced Technology Centre of Excellence in Next Generation Networks Department of Electrical Engineering Indian Institute of Technology Madras

ISBN: (纸本)9781467355339

Our focus is on a non-linear, time delayed, fluid model for Compound TCP （C-TCP） which is widely implemented in the current Internet. We couple this model with a Drop-Tail queue policy, currently deployed in routers, in two different limiting regimes: a small buffer and an intermediate buffer regime. We consider a topology where two distinct sets of long lived Compound flows, each regulated by separate edge routers, merge at a common core network router. For both the small and the intermediate router buffer regimes, we derive explicit analytical conditions under which synchronisation would occur between the two competing sets of TCP flows. The conditions are made explicit in terms of a coupling strength, which depends on Compound parameters and on network parameters like the feedback delay, link capacity and router buffer sizes. Variations in the coupling strength can lead to the emergence of deterministic, nonlinear, oscillations in the form of limit cycles in the queue size. Our analytical results are corroborated with packet-level simulations. With Drop-Tail, small buffers were found to be preferable over intermediate buffers;they can ensure both low latency and stable queues, at least in high speed networks.

关键词： Compound TCP Drop-Tail queues congestion control delayed feedback synchronisation.

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Stability analysis of Compound TCP with Adaptive Virtual Queues

Stability analysis of Compound TCP with Adaptive Virtual Que...

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第25届中国控制与决策会议

作者： Anand rao Amit Warrier Gaurav raina India-Uk Advanced Technology Centre of Excellence in Next Generation Networks Department of Electrical Engineering Indian Institute of Technology Madras

ISBN: (纸本)9781467355339

Compound TCP （C-TCP） is currently the default transport layer protocol in the Windows operating system. We study a non-linear fluid model of Compound along with Virtual Queue （VQ） management schemes in network routers. One can implement virtual queue policies either non-adaptively or adaptively. The Adaptive Virtual Queue （AVQ）, in particular, has the objective of driving the link utilisation to a desired level. The stability analysis of non-adaptive virtual queues reveals that smaller virtual buffer sizing rules help stability. Small virtual buffers would quite naturally reduce queueing delays in routers. Some guidelines for Compound and network parameters to ensure local stability are outlined. Analysis of the AVQ policy shows that the system is prone to losing local stability with large feedback delays, high link capacities, and with variations in the AVQ damping factor. We further show that the loss of local stability would occur via a Hopf bifurcation. Based on the analysis, our recommendation is that a virtual queue, with small buffer sizes, could be an attractive queue management scheme.

关键词： Compound TCP virtual queue management non-linear systems local stability Hopf bifurcation.

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Probabilistic Fuzzy Approach to Assess rDS Vulnerability and Plan Corrective Action Using Feeder reconfiguration

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Energy and Power Engineering 2012年第5期4卷 330-338页

作者： Mini S Thomas rakesh ranjan roma raina Director IITB Sonepat India Faculty Manipal University Dubai Professor JamiaMilliaIslamiaUniversity New Delhi

Two common problems for a typical Power distribution system are voltage collapse & instability. Challenge is to identify the vulnerable nodes and apply the effective corrective actions. This paper presents a probabilistic fuzzy approach to assess the node status and proposes feeder reconfiguration as a method to address the same. Feeder reconfiguration is altering the topological structures of distribution feeders by changing the open/closed states of the sectionalizing and ties switches. The solution is converge using a probabilistic fuzzy modeled solution, which defines the nodal vulnerability index (VI) as a function of node voltage and node voltage stability index and predicts nodes critical to voltage collapse. The information is further used to plan best combination of feeders from each loop in distribution system to be switched out such that the resulting configuration gives the optimal performance i.e. best voltage profile and minimal kW losses. The proposed method is tested on established radial distribution system and results are presented.

关键词： Branch Voltage Three Phase Load Flow Voltage Stability Index (SI) radial Distribution System (rDS) Monte Carlo Probability Distributions Fuzzy Set Node Vulnerability Index(VI) Feeder reconfiguration

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A kaldor-kalecki model of business cycles:stability and limit cycles

A Kaldor-Kalecki model of business cycles:stability and limi...

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第26届中国控制与决策会议

作者： Sreelakshmi Manjunath Debayani Ghosh Gaurav raina Department of Electrical Engineering Indian Institute of Technology Madras

Combining ideas proposed by kaldor and kalecki leads to a non-linear, time delayed, model for business cycle dynamics. In this paper, we analyse the stability and the local Hopf bifurcation properties of a kaldor-kalecki type model. In the analysis of such models, it is common to assume that the time delay continuously varies, and hence it is treated as a bifurcation parameter. However, this may not be a realistic assumption in various economic *** use an exogeneous, and non-dimensional, parameter as the bifurcation parameter to show that the underlying system undergoes a local Hopf bifurcation. Further, as this parameter gradually varies beyond the Hopf condition, we expect limit cycles to emerge from the stable equilibrium. We then, using Poincar′e normal forms and the center manifold theory, outline the analysis to verify the type of the Hopf bifurcation and determine the stability of the limit cycles. The theoretical analysis is illustrated with some numerical examples.

关键词： kaldor-kalecki models business cycles delay equations stability Hopf bifurcation limit cycles.

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Back-stepping Control Strategy for Stabilization of a Tilt-rotor UAV

Back-stepping Control Strategy for Stabilization of a Tilt-r...

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第24届中国控制与决策会议

作者： Arindam Bhanja Chowdhury Anil kulhare Gaurav raina the Department of Electrical Engineering Indian Institute of Technology Madras the faculty of the Department of Electrical Engineering Indian Institute of Technology Madras

In today’s world, the study and applications of Vertical Take-Off and Landing （VTOL） capable Unmanned Aerial Vehicles （UAVs） have increased vastly. A wide variety of UAVs are currently being employed in both civilian and military sectors. In this paper, our focus will be on the Tilt-rotor UAV. The Tilt-rotor has a rotor on each side of its airframe, tilted to provide both lift and forward thrust to the rotor-craft. We develop a model that aims to enable the Tilt-rotor UAV to hover in one specific position. Because of the under-actuated property of the Tilt-rotor, we design a back-stepping based proportional- derivative （PD） controller. The controller was able to achieve the desired objective of stabilization.

关键词： tilt-rotor Lagrangian back-stepping PD controller.

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Aorto-Pulmonary Artery Fistula Following Aortic Valve replacement: A Diagnostic Dilemma

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World Journal of Cardiovascular Surgery 2016年第3期6卷 40-43页

作者： Tarun raina ramman Shyamveer khangarot Sunil kumar M. A. Geelani D. k. Satsangi Department of Cardiothoracic and Vascular Surgery GIPMER Hospital New Delhi India

Aorto-pulmonary artery fistula is a rare and lethal occurrence after thoracic surgery and aortic aneurysms. Here we present a rare occurrence of acute aorto-pulmonary artery fistula in outpatient department in a follow up patient of aortic valve replacement and discuss challenges faced in diagnosis, etiopathogenesis and management.

关键词： Aorto-Pulmonary Fistula Aortic Valve replacement rare Complications

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