Relevant bibliographies by topics / Discretization time varying system

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Discretization time varying system'

Author: Grafiati
Published: 6 September 2023

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Journal articles on the topic "Discretization time varying system"

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Song, Xiao, Yaofei Ma, Wei Zhang, and Jiangyun Wang. "Quantized State Based Simulation of Time Invariant and Time Varying Continuous Systems." Mathematical Problems in Engineering 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/141607.

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Continuous system can be discretized for computer simulation. Quantized state systems (QSS) method has been used to discretize time invariant systems based on the discretization of the state space. A HLA based QSS method is proposed in this paper to address issues of real-time advancements in simulation and an aircraft control example was introduced to illustrate our method. Moreover, to simulate time varying systems, a novel approach is also proposed and exemplified with a practical case.
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Jiang, Xiefu, Zongming Yin, and Jinjing Wu. "Stability Analysis of Linear Systems under Time-Varying Samplings by a Non-Standard Discretization Method." Electronics 7, no. 11 (October 27, 2018): 278. http://dx.doi.org/10.3390/electronics7110278.

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This paper is concerned with the stability of linear systems under time-varying sampling. First, the closed-loop sampled-data system under study is represented by a discrete-time system using a non-standard discretization method. Second, by introducing a new sampled-date-based integral inequality, the sufficient condition on stability is formulated by using a simple Lyapunov function. The stability criterion has lower computational complexity, while having less conservatism compared with those obtained by a classical input delay approach. Third, when the system is subject to parameter uncertainties, a robust stability criterion is derived for uncertain systems under time-varying sampling. Finally, three examples are given to show the effectiveness of the proposed method.
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Camlibel, Kanat, and Aneel Tanwani. "A discretization algorithm for time-varying composite gradient flow dynamics." IFAC-PapersOnLine 54, no. 9 (2021): 558–63. http://dx.doi.org/10.1016/j.ifacol.2021.06.116.

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GRÜNE, LARS. "ROBUST ASYMPTOTIC CONTROLLABILITY UNDER TIME-VARYING PERTURBATIONS." Stochastics and Dynamics 04, no. 03 (September 2004): 297–316. http://dx.doi.org/10.1142/s0219493704001085.

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We investigate the effect of time-varying perturbations on the dynamical behavior of nonlinear control systems. More specifically, we study the effect of such perturbations on the controlled equivalent of asymptotically stable sets, i.e. asymptotically controllable sets. In the first part of this paper we illustrate by a simple example how different types of perturbations affect this dynamical behavior and use concepts from dynamical game theory in order to identify classes of perturbations which allow to model the effects of numerical discretization errors both in time and space. In the second part we introduce appropriate robustness properties and prove that these are inherent properties for asymptotically controllable sets under these classes of perturbations.
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Okoniewski, Piotr, and Jacek Piskorowski. "Short Transient Parameter-Varying IIR Filter Based on Analog Oscillatory System." Applied Sciences 9, no. 10 (May 16, 2019): 2013. http://dx.doi.org/10.3390/app9102013.

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This paper presents a concept for digital infinite impulse response (IIR) lowpass filter with reduced transient response. The proposed digital filtering structure is based on an analog oscillatory system. In order to design the considered digital filter, the analog prototype is subjected to a discretization process and, then, the parameters describing the dynamical properties of the oscillatory system are temporarily varied in time, so as to suppress the transient response of the designed filter. An optimization method, aimed at reducing the settling time by proper parameter manipulation, is presented. Simulation results, along with a real-life application proving the usefulness of the proposed concept, are also shown and discussed.
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KO, Jeong-Wan, and PooGyeon PARK. "Delay-Dependent Stability Criteria for Systems with Time-Varying Delays: State Discretization Approach." IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E92-A, no. 4 (2009): 1136–41. http://dx.doi.org/10.1587/transfun.e92.a.1136.

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Shao, Chenhui, Shuang Li, Haitao Li, and Jie Sheng. "Control for Time‐Varying Delay Systems by Integrating Semi‐Discretization and Hysteresis‐Based Switching." Asian Journal of Control 21, no. 5 (August 8, 2018): 2181–92. http://dx.doi.org/10.1002/asjc.1829.

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De la Sen, M. "About a Class of Positive Hybrid Dynamic Linear Systems and an Associate Extended Kalman-Yakubovich-Popov Lemma." Discrete Dynamics in Nature and Society 2017 (2017): 1–22. http://dx.doi.org/10.1155/2017/3928970.

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This paper formulates an “ad hoc” robust version under parametrical disturbances of the discrete version of the Kalman-Yakubovich-Popov Lemma for a class of positive hybrid dynamic linear systems which consist of a continuous-time system coupled with a discrete-time or a digital one. An extended discrete system, whose state vector contains both the digital one and the discretization of the continuous-time one at sampling instants, is a key analysis element in the formulation. The hyperstability and asymptotic hyperstability properties of the studied class of positive hybrid systems under feedback from any member of a nonlinear (and, eventually, time-varying) class of controllers, which satisfies a Popov’s-type inequality, are also investigated as linked to the positive realness of the associated transfer matrices.
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WANG, JINJIE, GUOHUA CAO, YANDONG WANG, and RONGHUA WU. "A NOVEL DRIVING STRATEGY FOR DYNAMIC SIMULATION OF HOISTING ROPE WITH TIME-VARYING LENGTH." International Journal of Modeling, Simulation, and Scientific Computing 04, no. 03 (August 19, 2013): 1350009. http://dx.doi.org/10.1142/s1793962313500098.

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A simulation method for investigating the vibration behavior of hoisting rope with time-varying length is improved. By previously creating markers in the MSC.ADAMS software package, the parametric model of the rope wound along helix is established based on the concentrated-mass theory with multi-degree of freedom (multi-DOF). A novel driving strategy, cooperating fixed joints with angle sensors under the control of driving script, is proposed to substitute conventional contact force. Researching on the hoisting rope in the sinking winch mechanism, an equivalent discretization model is obtained with complicated boundary conditions considered. The differential equations of motion of the hoisting system are formulated employing Lagrange's equation and numerically solved using Runge–Kutta method. The simulation indicates that the horizontal swing is decreased in principle and the simulation with 800 discrete ropes is not performed more than 61 min. Therefore, this feasible strategy could not only guarantee the accuracy but also promote simulation efficiency and stability. The motion curves exported from ADAMS simulation coincide with one in numerical simulation, which validates both the numerical model and the driving strategy.
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Bürger, Raimund, Julio Careaga, and Stefan Diehl. "A method-of-lines formulation for a model of reactive settling in tanks with varying cross-sectional area." IMA Journal of Applied Mathematics 86, no. 3 (May 20, 2021): 514–46. http://dx.doi.org/10.1093/imamat/hxab012.

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Abstract Reactive settling denotes the process of sedimentation of small solid particles dispersed in a viscous fluid with simultaneous reactions between the components that constitute the solid and liquid phases. This process is of particular importance for the simulation and control of secondary settling tanks (SSTs) in water resource recovery facilities (WRRFs), formerly known as wastewater treatment plants. A spatially 1D model of reactive settling in an SST is formulated by combining a mechanistic model of sedimentation with compression with a model of biokinetic reactions. In addition, the cross-sectional area of the tank is allowed to vary as a function of height. The final model is a system of strongly degenerate parabolic, nonlinear partial differential equations that include discontinuous coefficients to describe the feed, underflow and overflow mechanisms, as well as singular source terms that model the feed mechanism. A finite difference scheme for the final model is developed by first deriving a method-of-lines formulation (discrete in space, continuous in time) and then passing to a fully discrete scheme by a time discretization. The advantage of this formulation is its compatibility with common practice in development of software for WRRFs. The main mathematical result is an invariant-region property, which implies that physically relevant numerical solutions are produced. Simulations of denitrification in SSTs in WRRFs illustrate the model and its discretization.
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Dissertations / Theses on the topic "Discretization time varying system"

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Wang, Bin, and s3115026@student rmit edu au. "On Discretization of Sliding Mode Control Systems." RMIT University. Electrical and Computer Engineering, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080822.145013.

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Sliding mode control (SMC) has been successfully applied to many practical control problems due to its attractive features such as invariance to matched uncertainties. The characteristic feature of a continuous-time SMC system is that sliding mode occurs on a prescribed manifold, where switching control is employed to maintain the state on the surface. When a sliding mode is realized, the system exhibits some superior robustness properties with respect to external matched uncertainties. However, the realization of the ideal sliding mode requires switching with an infinite frequency. Control algorithms are now commonly implemented in digital electronics due to the increasingly affordable microprocessor hardware although the essential conceptual framework of the feedback design still remains to be in the continuous-time domain. Discrete sliding mode control has been extensively studied to address some basic questions associated with the sliding mode control of discrete-time systems with relatively low switching frequencies. However, the complex dynamical behaviours due to discretization in continuous-time SMC systems have not yet been fully explored. In this thesis, the discretization behaviours of SMC systems are investigated. In particular, one of the most frequently used discretization schemes for digital controller implementation, the zero-order-holder discretization, is studied. First, single-input SMC systems are discretized, stability and boundary conditions of the digitized SMC systems are derived. Furthermore, some inherent dynamical properties such as periodic phenomenon, of the discretized SMC systems are studied. We also explored the discretization behaviours of the disturbed SMC systems. Their steady-state behaviours are discussed using a symbolic dynamics approach under the constant and periodic matched uncertainties. Next, discretized high-order SMC systems and sliding mode based observers are explored using the same analysis method. At last, the thesis investigates discretization effects on the SMC systems with multiple inputs. Some conditions are first derived for ensuring the
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Eckstein, Sarah [Verfasser], and Michael [Akademischer Betreuer] Růžička. "On the full space-time discretization of the generalized Stokes system: the Dirichlet case = On the full space-time discretization of the generalized Stokes equations: The Dirichlet case." Freiburg : Universität, 2016. http://d-nb.info/1122743491/34.

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Hosoe, Yohei. "Discrete-Time Noncausal Linear Periodically Time-Varying Scaling for Robustness Analysis and Controller Synthesis." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180502.

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Mongol, Bayarpurev, Takaya Yamazato, Hiraku Okada, and Masaaki Katayama. "Channel Estimation for BFDM/OQAM System in Dispersive Time-Varying Channels." IEEE, 2006. http://hdl.handle.net/2237/7762.

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Grigoriadis, Karolos M. "On the robust stabilization of a linear time-varying uncertain system." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/45976.

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In recent years the problem of designing a feedback control law to stabilize a linear, time-varying uncertain system has received considerable attention. However, the problem is usually limited to the case of systems which satisfy the "matching" assumptions. Moreover, the question of the existence of a linear stabilizing control, if a nonlinear stabilizing control exists, is still unanswered. In the present work an attempt is made to design a stabilizing, linear, feedback control law for a specific second order, linear system which contains time-varying uncertainties into both the state and input matrices and does not satisfy the matching conditions. For specific values of the uncertainty bounds this system is quadratically stabilizable but not quadratically stabilizable via linear control.


Master of Science
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Reber, David Patrick. "Exponential Stability of Intrinsically Stable Dynamical Networks and Switched Networks with Time-Varying Time Delays." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7136.

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Dynamic processes on real-world networks are time-delayed due to finite processing speeds and the need to transmit data over nonzero distances. These time-delays often destabilize the network's dynamics, but are difficult to analyze because they increase the dimension of the network.We present results outlining an alternative means of analyzing these networks, by focusing analysis on the Lipschitz matrix of the relatively low-dimensional undelayed network. The key criteria, intrinsic stability, is computationally efficient to verify by use of the power method. We demonstrate applications from control theory and neural networks.
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Huang, Rui. "OUTPUT FEEDBACK TRACKING CONTROL OF NONLINEAR TIME-VARYING SYSTEMS BY TRAJECTORY LINEARIZATION." Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1178906759.

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Benner, Peter, and Sabine Hein. "Model predictive control based on an LQG design for time-varying linearizations." Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-201000221.

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We consider the solution of nonlinear optimal control problems subject to stochastic perturbations with incomplete observations. In particular, we generalize results obtained by Ito and Kunisch in [8] where they consider a receding horizon control (RHC) technique based on linearizing the problem on small intervals. The linear-quadratic optimal control problem for the resulting time-invariant (LTI) problem is then solved using the linear quadratic Gaussian (LQG) design. Here, we allow linearization about an instationary reference trajectory and thus obtain a linear time-varying (LTV) problem on each time horizon. Additionally, we apply a model predictive control (MPC) scheme which can be seen as a generalization of RHC and we allow covariance matrices of the noise processes not equal to the identity. We illustrate the MPC/LQG approach for a three dimensional reaction-diffusion system. In particular, we discuss the benefits of time-varying linearizations over time-invariant ones.
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Xiong, Dapeng. "Stability analysis and controller synthesis of linear parameter varying systems /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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Jalinous, R. "The use of time-varying magnetic fields to stimulate the human nervous system : theory and practice." Thesis, University of Sheffield, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285543.

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Books on the topic "Discretization time varying system"

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Bogdan, Marinescu, ed. Linear time-varying systems: Algebraic-analytic approach. Berlin: Springer-Verlag, 2011.

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Dewilde, P. Time-Varying Systems and Computations. Boston, MA: Springer US, 1998.

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der, Veen Alle-Jan van, ed. Time-varying systems and computations. Boston: Kluwer Academic Publishers, 1998.

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Santos, Paulo Lopes dos. Linear parameter-varying system identification: New developments and trends. Singapore: World Scientific, 2012.

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Paulo, Ribeiro, ed. Time-varying waveform distortions in power systems. Chichester, West Sussex, U.K: Wiley, 2009.

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1949-, Banks Stephen P., ed. Linear, time-varying approximations to nonlinear dynamical systems: With applications in control and optimization. Berlin: Springer, 2010.

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Mukherjee, Animesh. Dynamics On and Of Complex Networks, Volume 2: Applications to Time-Varying Dynamical Systems. New York, NY: Springer New York, 2013.

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Checketts, D. G. Performance degradation of a synthetic aperture sonar imaging system due to a time varying towed-array orientation and trajectory. Birmingham: University of Birmingham, 1987.

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Harley, Cudney, Sinha S. C. 1947-, American Society of Mechanical Engineers. Design Engineering Division., and Conference on Mechanical Vibration and Noise (15th : 1995 : Boston, Mass.), eds. Vibration of nonlinear, random, and time-varying systems: Presented at the 1995 ASME Design Engineering Technical Conferences--the 15th Biennial Conference on Mechanical Vibration and Noise, September 17-20, 1995, Boston, Massachusetts. New York: American Society of Mechanical Engineers, 1995.

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Richards, John A. Analysis of Periodically Time-Varying Systems. Springer, 2011.

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Book chapters on the topic "Discretization time varying system"

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Rabbath, C. A., and N. Léchevin. "Discretization." In Discrete-Time Control System Design with Applications, 31–50. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-9290-0_3.

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Huang, Weizhang, and Robert D. Russell. "Discretization of PDEs on Time-Varying Meshes." In Adaptive Moving Mesh Methods, 137–76. New York, NY: Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-7916-2_3.

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Bourlès, Henri, and Bogdan Marinescu. "Modeling: Choice of the Input Variables of an LTV System." In Linear Time-Varying Systems, 515–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-19727-7_9.

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Zhang, Yunong, and Dongsheng Guo. "System of Time-Varying Linear Equations." In Zhang Functions and Various Models, 49–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-47334-4_4.

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Wang, Qian, Wei Xiong, and Ya Shuang Deng. "Time-Varying Impulsive Anticontrol of Discrete-Time System." In Applications and Techniques in Information Security, 326–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-48683-2_29.

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Deb, Anish, Srimanti Roychoudhury, and Gautam Sarkar. "Time Varying System Analysis: State Space Approach." In Analysis and Identification of Time-Invariant Systems, Time-Varying Systems, and Multi-Delay Systems using Orthogonal Hybrid Functions, 221–39. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-26684-8_9.

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Sladký, Karel. "Stability analysis of time—varying discrete interval systems." In System Modelling and Optimization, 179–86. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-0-387-34897-1_19.

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Hunter, I., and R. Kearney. "System Identification in Motor Control: Time-Varying Techniques." In Motor Control, 189–95. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4615-7508-5_33.

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Xin, Yu, Hong Hao, and Jun Li. "Using Novel Time Frequency Analysis Method for Time-Varying System Identification." In Lecture Notes in Civil Engineering, 239–46. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-8079-6_23.

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Frunzete, Madalin, Adrian Luca, Adriana Vlad, and Jean-Pierre Barbot. "Statistical Behaviour of Discrete-Time Rössler System with Time Varying Delay." In Computational Science and Its Applications - ICCSA 2011, 706–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-21928-3_52.

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Conference papers on the topic "Discretization time varying system"

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Meena, Gagan Deep, and S. Janardhanan. "Discretization of Linear Time-Varying Systems." In 2020 International Conference on Emerging Frontiers in Electrical and Electronic Technologies (ICEFEET). IEEE, 2020. http://dx.doi.org/10.1109/icefeet49149.2020.9186982.

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Braga, Marcio F., Cecilia F. Morais, Eduardo S. Tognetti, Ricardo C. L. F. Oliveira, and Pedro L. D. Peres. "Discretization and discrete-time output feedback control of linear parameter varying continuous-time systems." In 2014 IEEE 53rd Annual Conference on Decision and Control (CDC). IEEE, 2014. http://dx.doi.org/10.1109/cdc.2014.7040132.

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Insperger, Tamás, and Gábor Stépán. "Semi-Discretization of Delayed Dynamical Systems." In ASME 2001 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/detc2001/vib-21446.

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Abstract An efficient numerical method is presented for the stability analysis of linear retarded dynamical systems. The method is based on a special kind of discretization technique with respect to the past effect only. The resulting approximate system is delayed and time-periodic in the same time, but still, it can be transformed analytically into a high dimensional linear discrete system. The method is especially efficient for time varying delayed systems, including the case when the time delay itself varies in time. The method is applied to determine the stability charts of the delayed Mathieu equation with damping.
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Zhang, Yunong, Guofu Wu, Xuyun Yang, Huihui Gong, and Min Yang. "Discrete Getz-Masden dynamic system 2 via Taylor-Zhang discretization formula solving for time-varying complex matrix inverse." In 2017 Chinese Automation Congress (CAC). IEEE, 2017. http://dx.doi.org/10.1109/cac.2017.8243924.

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Insperger, Tamás, Gábor Stépán, and Sri N. Namachchivaya. "Comparison of the Dynamics of Low Immersion Milling and Cutting With Varying Spindle Speed." In ASME 2001 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/detc2001/vib-21616.

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Abstract The stability properties of cutting processes are strongly limited by the so-called regenerative effect. This effect is originated in the presence of a time-delay in the dynamical system of the machine tool. This delay is inversely proportional to the cutting speed. Consequently, conventional cutting with a single-edge tool is modeled by an autonomous delay-differential equation (DDE). In case of milling, the varying number of cutting edges results in a kind of parametric excitation, and the corresponding mathematical model is a non-autonomous DDE. In case of low-immersion milling, this affects the stability boundaries in a substantial way. Cutting with varying spindle speed results non-autonomous DDEs where the time delay itself depends on the time periodically. A new semi-discretization method is proposed to handle the stability of these non-autonomous systems. The stability properties and corresponding bifurcations are compared in the above different cases of machining.
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Wang, S. Y., and S. C. Sinha. "Parametric Instability in a Gear Train System Due to Stiffness Variation." In ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-13388.

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The excitation from mesh stiffness variation in a tunnel gear driving system can cause excessive noise and vibrations. Since the stiffness variation may induce parametric instability, the system could be damaged on a permanent-basis. Therefore, the study of parametric instability in such system is of paramount importance. In this work, a rigid-elastic model is developed using the energy method, where the ring gear is treated as a rotating thin ring having radial and tangential deflections, whereas the pinions are assumed to be rigid bodies having translational motion relative to the radial directions of the ring gear as well as rotational motions around their centers. All gear meshes are modeled as interactions caused by time-varying springs, and the supports of the pinions are modeled as linear springs in the radial direction relative to the ring gear. The modeling leads to a set of partial-ordinary linear differential equations with time-varying coefficients. For an N planet system, the discretization process yields 2N+2 ordinary differential equations. Stability boundaries are determined using Floque’t theory for a wide range of parameter values. Specifically, the effects of mesh stiffness on the parametric instability are examined. The results show that the instability behaviors are closely related to the basic parameters when considering the time-varying excitation. This could be a serious consideration in the preliminary design of such systems.
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Hagiwara, Tomomichi, and Hiroaki Umeda. "Robust stability analysis of sampled-data systems with noncausal periodically time-varying scaling: Optimization of scaling via approximate discretization and error bound analysis." In 2007 46th IEEE Conference on Decision and Control. IEEE, 2007. http://dx.doi.org/10.1109/cdc.2007.4434441.

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Luo, Albert C. J., and Siyuan Xing. "On Time-Delay Effects on Period-1 Motions in a Periodically Forced, Time-Delayed, Duffing Oscillator." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66198.

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In recent decades, nonlinear time-delay systems were often applied in controlling nonlinear systems, and the stability of such time-delay systems was very actively discussed. Recently, one was very interested in periodic motions in nonlinear time-delay systems. Especially, the semi-analytical solutions of periodic motions in time-delay systems are of great interest. From the semi-analytical solutions, the nonlinearity and complexity of periodic motions in the time-delay systems can be discussed. In this paper, time-delay effects on periodic motions of a periodically forced, damped, hardening, Duffing oscillator are analytically discussed through a semi-analytical method. The semi-analytical method is based on discretization of the differential equation of such a Duffing oscillator to obtain the corresponding implicit discrete mappings. Through such implicit mappings and mapping structures of periodic motions, period-1 motions varying with time-delay are discussed, and the corresponding stability and bifurcation analysis of periodic motions are carried out through eigenvalue analysis. Numerical results of periodic motions are illustrated to verify analytical predictions. The corresponding harmonic amplitude spectrums and harmonic phases are presented for a better understanding of periodic motions in such a nonlinear oscillator.
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Cho, Jihyun, and Samuel F. Asokanthan. "Dynamic Stability of Ring-Based MEMS Gyroscopes." In ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-85321.

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Dynamic stability of ring-based MEMS gyroscopes subjected to harmonic perturbations in input angular rate is examined using an asymptotic approach. The governing equations that represent the transverse and tangential in-plane motion of the ring are derived via Hamilton’s principle. The equations of motion, after discretization and suitable linearization, represent a two-degree-of-freedom time-varying linear gyroscopic system. Such a system can exhibit instability behaviour characterized by exponential growth in response amplitudes. Employing the method of averaging, conditions for instability are obtained in closed-form. Instability boundaries for the ring in the excitation intensity-frequency space are then established for small excitation amplitudes. In addition, effects of damping, input angular rate variations, and the effect of imperfection due to the ring asymmetry are discussed.
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Zaman, M. Hasanat. "Suppression of Ocean Waves by Uniform Forced Currents." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57370.

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Ocean current might be a useful tool to suppress ocean waves that approach a particular region of interest. A reliable short term sheltering approach might be enough in some areas where a heavy and/or permanent protection system is impractical, considering its usage, duration of deployment and money involved. This study is carried out using a 3D finite difference numerical model. The model is presently developed for long crested waves and uniform current by the vertical integration of the continuity equation and the equations of motion. A semi-implicit finite difference technique is employed for the discretization of the governing equations in time and space. Results are shown in terms of wave height distributions, reflection and transmission coefficients for varying currents, incident wave and current angles.
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Reports on the topic "Discretization time varying system"

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Hernandez, O. A linear, time-varying simulation of the respiratory tract system. Office of Scientific and Technical Information (OSTI), November 1992. http://dx.doi.org/10.2172/6944005.

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Hernandez, Oscar. A linear, time-varying simulation of the respiratory tract system. Office of Scientific and Technical Information (OSTI), November 1992. http://dx.doi.org/10.2172/10110476.

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Gearhart, Jared Lee, and Nolan Scot Kurtz. Time-Varying, Multi-Scale Adaptive System Reliability Analysis of Lifeline Infrastructure Networks. Office of Scientific and Technical Information (OSTI), September 2014. http://dx.doi.org/10.2172/1259845.

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Kularatne, Dhanushka N., Subhrajit Bhattacharya, and M. Ani Hsieh. Computing Energy Optimal Paths in Time-Varying Flows. Drexel University, 2016. http://dx.doi.org/10.17918/d8b66v.

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Autonomous marine vehicles (AMVs) are typically deployed for long periods of time in the ocean to monitor different physical, chemical, and biological processes. Given their limited energy budgets, it makes sense to consider motion plans that leverage the dynamics of the surrounding flow field so as to minimize energy usage for these vehicles. In this paper, we present two graph search based methods to compute energy optimal paths for AMVs in two-dimensional (2-D) time-varying flows. The novelty of the proposed algorithms lies in a unique discrete graph representation of the 3-D configuration space spanned by the spatio-temporal coordinates. This enables a more efficient traversal through the search space, as opposed to a full search of the spatio-temporal configuration space. Furthermore, the proposed strategy results in solutions that are closer to the global optimal when compared to greedy searches through the spatial coordinates alone. We demonstrate the proposed algorithms by computing optimal energy paths around the Channel Islands in the Santa Barbara bay using time-varying flow field forecasts generated by the Regional Ocean Model System. We verify the accuracy of the computed paths by comparing them with paths computed via an optimal control formulation.
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Di Campli San Vito, Patrizia, Stephen Brewster, Satvik Venkatesh, Eduardo Miranda, Alexis Kirke, David Moffat, Sube Banerjee, Alex Street, Jorg Fachner, and Helen Odell-Miller. RadioMe: Supporting Individuals with Dementia in Their Own Home... and Beyond? CHI '22 Workshop - Designing Ecosystems for Complex Health Needs, 2022. http://dx.doi.org/10.36399/gla.pubs.267520.

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Dementia is an illness with complex health needs, varying between individuals and increasing in severity over time. Approaches to use technology to aid people with dementia are often designed for a specific environment and/or purpose, such as the RadioMe system, a system designed to detect agitation in people with mild dementia living in their own home and calming them with music when agitation is detected. Both the monitoring and intervention components could potentially be beneficially used outside of the own home to aid people with dementia and carers in everyday life. But the adaptation could put additional burdens on the carer, as many decisions and the handling of the data and software could rely on their input. In this paper we discuss thoughts on the potential role of the carer for adaptations of specified system’s expansion to a larger ecosystem on the example of RadioMe.
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Singh, Niranjan. A Method of Sound Wave Diffusion in Motor Vehicle Exhaust Systems. Unitec ePress, April 2017. http://dx.doi.org/10.34074/ocds.072.

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It is common practice among young vehicle owners to modify the exhaust system of their vehicle to reduce exhaust backpressure with the perception that the output power increases. In the process of backpressure reduction, the output noise (Whakapau) of the vehicle also increases correspondingly. The conflict of interest that arises from modified vehicle exhaust systems and the general public is well publicised. This prototype was designed to meet the demands of exhaust back pressure reduction while at the same time mitigate the sound output of the vehicle. The design involves lining a cylindrical pipe with common glass marbles which is normally used for playing. The marbles are made of a sustainable material as it does not erode when exposed to exhaust gases and it is easily recycled. The prototype muffler is much smaller in size when compared to conventional mufflers. All tests were done in a simulated controlled environment and data collated using approved New Zealand Transport Agency testing regime. It has to be noted that the test focus was noise mitigation and not comprehensive engine performance testing. The results of the test prove a reduction of sound levels, however more testing needs to be undertaken with varying annulus depth, marble sizes and arrangements and engine loads.
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Miles, Gaines E., Yael Edan, F. Tom Turpin, Avshalom Grinstein, Thomas N. Jordan, Amots Hetzroni, Stephen C. Weller, Marvin M. Schreiber, and Okan K. Ersoy. Expert Sensor for Site Specification Application of Agricultural Chemicals. United States Department of Agriculture, August 1995. http://dx.doi.org/10.32747/1995.7570567.bard.

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In this work multispectral reflectance images are used in conjunction with a neural network classifier for the purpose of detecting and classifying weeds under real field conditions. Multispectral reflectance images which contained different combinations of weeds and crops were taken under actual field conditions. This multispectral reflectance information was used to develop algorithms that could segment the plants from the background as well as classify them into weeds or crops. In order to segment the plants from the background the multispectrial reflectance of plants and background were studied and a relationship was derived. It was found that using a ratio of two wavelenght reflectance images (750nm and 670nm) it was possible to segment the plants from the background. Once ths was accomplished it was then possible to classify the segmented images into weed or crop by use of the neural network. The neural network developed for this work is a modification of the standard learning vector quantization algorithm. This neural network was modified by replacing the time-varying adaptation gain with a constant adaptation gain and a binary reinforcement function. This improved accuracy and training time as well as introducing several new properties such as hill climbing and momentum addition. The network was trained and tested with different wavelength combinations in order to find the best results. Finally, the results of the classifier were evaluated using a pixel based method and a block based method. In the pixel based method every single pixel is evaluated to test whether it was classified correctly or not and the best weed classification results were 81% and its associated crop classification accuracy is 57%. In the block based classification method, the image was divided into blocks and each block was evaluated to determine whether they contained weeds or not. Different block sizes and thesholds were tested. The best results for this method were 97% for a block size of 8 inches and a pixel threshold of 60. A simulation model was developed to 1) quantify the effectiveness of a site-specific sprayer, 2) evaluate influence of diffeent design parameters on efficiency of the site-specific sprayer. In each iteration of this model, infected areas (weed patches) in the field were randomly generated and the amount of required herbicides for spraying these areas were calculated. The effectiveness of the sprayer was estimated for different stain sizes, nozzle types (conic and flat), nozzle sizes and stain detection levels of the identification system. Simulation results indicated that the flat nozzle is much more effective as compared to the conic nozzle and its relative efficiency is greater for small nozzle sizes. By using a site-specific sprayer, the average ratio between the spraying areas and the stain areas is about 1.1 to 1.8 which can save up to 92% of herbicides, especially when the proportion of the stain areas is small.
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Prusky, Dov, Nancy P. Keller, and Amir Sherman. global regulation of mycotoxin accumulation during pathogenicity of Penicillium expansum in postharvest fruits. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7600012.bard.

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Background to the topic- Penicilliumas a postharvest pathogen and producer of the mycotoxin PAT. Penicilliumspp. are destructive phytopathogens, capable of causing decay in many deciduous fruits, during postharvest handling and storage; and the resulting losses can amount to 10% of the stored produce and the accumulation of large amounts of the mycotoxinpatulin. The overall goal of this proposal is to identify critical host and pathogen factors that modulate P. expansummycotoxin genes and pathways which are required for PAT production and virulence. Our preliminary results indicated that gluconic acid are strongly affecting patulin accumulation during colonization. P. expansumacidifies apple fruit tissue during colonization in part through secretion of gluconic acid (GLA). Several publications suggested that GLA accumulation is an essential factor in P. expansumpathogenicity. Furthermore, down regulation of GOX2 significantly reduced PAT accumulation and pathogenicity. PAT is a polyketide and its biosynthesis pathway includes a 15-gene cluster. LaeA is a global regulator of mycotoxin synthesis. It is now known that patulin synthesis might be subjected to LaeA and sometimes by environmental sensing global regulatory factors including the carbon catabolite repressor CreA as well as the pH regulator factor PacC and nitrogen regulator AreA. The mechanisms by which LaeA regulates patulin synthesis was not fully known and was part of our work. Furthermore, the regulatory system that controls gene expression in accordance with ambient pH was also included in our work. PacC protein is in an inactive conformation and is unable to bind to the promoter sites of the target genes; however, under alkaline growth conditions activated PacC acts as both an activator of alkaline-expressed genes and a repressor of acid-expressed genes. The aims of the project- This project aims to provide new insights on the roles of LaeA and PacC and their signaling pathways that lead to GLA and PAT biosynthesis and pathogenicity on the host. Specifically, our specific aims were: i) To elucidate the mechanism of pH-controlled regulation of GLA and PAT, and their contribution to pathogenesis of P. expansum. We are interested to understanding how pH and/or GLA impact/s under PacC regulation affect PAT production and pathogenesis. ii) To characterize the role of LaeA, the global regulator of mycotoxin production, and its effect on PAT and PacC activity. iii) To identify the signaling pathways leading to GLA and PAT synthesis. Using state- of-the-art RNAseq technologies, we will interrogate the transcriptomes of laeAand pacCmutants, to identify the common signaling pathways regulating synthesis of both GLA and PAT. Major conclusions, solutions, achievements- In our first Aim our results demonstrated that ammonia secreted at the leading edge of the fungal colony induced transcript activation of the global pH modulator PacC and PAT accumulation in the presence of GLA. We assessed these parameters by: (i) direct exogenous treatment of P. expansumgrowing on solid medium; (ii) direct exogenous treatment on colonized apple tissue; (iii) growth under self-ammonia production conditions with limited carbon; and (iv) analysis of the transcriptional response to ammonia of the PAT biosynthesis cluster. Ammonia induced PAT accumulation concurrently with the transcript activation of pacCand PAT biosynthesis cluster genes, indicating the regulatory effect of ammonia on pacCtranscript expression under acidic conditions. Transcriptomic analysis of pH regulated processes showed that important genes and BARD Report - Project 4773 Page 2 of 10 functionalities of P. expansumwere controlled by environmental pH. The differential expression patterns of genes belonging to the same gene family suggest that genes were selectively activated according to their optimal environmental conditions to enable the fungus to cope with varying conditions and to make optimal use of available enzymes. Concerning the second and third Aims, we demonstrated that LaeA regulates several secondary metabolite genes, including the PAT gene cluster and concomitant PAT synthesis invitro. Virulence studies of ΔlaeAmutants of two geographically distant P. expansumisolates (Pe-21 from Israel and Pe-T01 from China) showed differential reduction in disease severity in freshly harvested fruit ranging from no reduction for Ch-Pe-T01 strains in immature fruit to 15–25% reduction for both strains in mature fruit, with the ΔlaeAstrains of Is-Pe-21 always showing a greater loss in virulence. Results suggest the importance of LaeA regulation of PAT and other secondary metabolites on pathogenicity. Our work also characterized for the first time the role of sucrose, a key nutritional factor present in apple fruit, as a negative regulator of laeAexpression and consequent PAT production in vitro. This is the first report of sugar regulation of laeAexpression, suggesting that its expression may be subject to catabolite repression by CreA. Some, but not all of the 54 secondary metabolite backbone genes in the P. expansumgenome, including the PAT polyketide backbone gene, were found to be regulated by LaeA. Together, these findings enable for the first time a straight analysis of a host factor that potentially activates laeAand subsequent PAT synthesis.
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Global Education Monitoring Report - Non-state actors in education: Who chooses? Who loses? UNESCO, December 2021. http://dx.doi.org/10.54676/ytjt5864.

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Non-state actors’ role extends beyond provision of schooling to interventions at various education levels and influence spheres. Alongside its review of progress towards SDG 4, including emerging evidence on the COVID-19 pandemic’s impact, the 2021/2 Global Education Monitoring Report urges governments to see all institutions, students and teachers as part of a single system. Standards, information, incentives and accountability should help governments protect, respect and fulfil the right to education of all, without turning their eyes away from privilege or exploitation. Publicly funded education does not have to be publicly provided but disparity in education processes, student outcomes and teacher working conditions must be addressed. Efficiency and innovation, rather than being commercial secrets, should be diffused and practised by all. To that end, transparency and integrity in the public education policy process need to be maintained to block vested interests. The report’s rallying call – Who chooses? Who loses? – invites policymakers to question relationships with non-state actors in terms of fundamental choices: between equity and freedom of choice; between encouraging initiative and setting standards; between groups of varying means and needs; between immediate commitments under SDG 4 and those to be progressively realized (e.g. post-secondary education); and between education and other social sectors. Supporting the fifth Global Education Monitoring Report are two online tools: PEER, a policy dialogue resource describing non-state activity and regulations in the world’s education systems; and VIEW, a new website consolidating sources and providing new completion rate estimates over time.
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Event-Triggered Adaptive Robust Control for Lateral Stability of Steer-by-Wire Vehicles with Abrupt Nonlinear Faults. SAE International, July 2022. http://dx.doi.org/10.4271/2022-01-5056.

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Because autonomous vehicles (AVs) equipped with active front steering have the features of time varying, uncertainties, high rate of fault, and high burden on the in-vehicle networks, this article studies the adaptive robust control problem for improving lateral stability in steer-by-wire (SBW) vehicles in the presence of abrupt nonlinear faults. First, an upper-level robust H∞ controller is designed to obtain the desired front-wheel steering angle for driving both the yaw rate and the sideslip angle to reach their correct values. Takagi-Sugeno (T-S) fuzzy modeling method, which has shown the extraordinary ability in coping with the issue of nonlinear, is applied to deal with the challenge of the changing longitudinal velocity. The output of the upper controller can be calculated by a parallel distributed compensation (PDC) scheme. Then an event-triggered adaptive fault-tolerant lower controller (ET-AFTC) is proposed to drive the whole SBW system driving the desired steering angle offered by the upper controller with fewer communication resources and strong robustness. By employing a backstepping technique, the tracking performance is improved. The dynamic surface control (DSC) approach is used to avoid the problem of repeated differentiations, and Nussbaum function is adopted to overcome the difficulty of unknown nonlinear control gain. Both the stability of the upper and lower controllers can be guaranteed by Lyapunov functions. Finally, the simulations of Matlab/Simulink are given to show that the proposed control strategy is effectively able to deal with the abrupt nonlinear fault via less communication resources and perform better in ensuring the yaw stability of the vehicle.
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