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Qualitative study for the system of waste plastic management in the ocean: A discrete-time deterministic model

COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION 2025年 143卷

作者： Parsamanesh, Mahmood Gumus, Mehmet Natl Univ Skills NUS Dept Math Tehran Iran Zonguldak Bulent Ecevit Univ Fac Sci Dept Math TR-67100 Zonguldak Turkiye

Ocean waste is a serious environmental problem affecting marine ecosystems and marine life. A large portion of this waste consists of recyclable materials. If managed correctly, it provides both economic and environmental benefits. By using mathematical models, it is possible to predict the spread of these wastes and develop strategies. In this paper, a discrete-time compartmental model is introduced for the cycle of processing the waste plastic management in the ocean. The model comprises three compartments plastic waste, marine debris, and recycled materials. A system of difference equations is formulated for this process according to the transmissions of materials between compartments. Then two equilibria for the model are obtained;the marine debris-free equilibrium point and the marine debris-included equilibrium point. Also, the basic reproduction number for the model is given, then its stability is investigated and stated in terms of this quantity. Furthermore, the bifurcations of the model including transcritical, period- doubling, and Neimark-Sacker bifurcation, are studied and the conditions for their occurrence are given. The obtained theoretical results are verified via several examples and simulations.

关键词： Waste plastic cycle discrete-time model Compartmental model Basic reproduction number Asymptotic stability Bifurcations

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discrete-time model for digital communications over a frequency-selective Rician fading WSSUS channel

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IEE PROCEEDINGS-COMMUNICATIONS 1996年第1期143卷 37-42页

作者： Yip, KW Ng, TS Department of Electrical and Electronic Engineering Yhe University of Hong Kong Hong Kong

The paper develops a discrete-time model for digital communications via a frequency-selective Rician fading, wide-sense-stationary uncorrelated-scattering (WSSUS) channel with arbitrary pulse shaping and receiver filtering. As a special case, the discrete-time model is also applicable to a frequency-selective Rayleigh fading WSSUS channel. The model is expressed in the form Xi(k) = N-k + Sigma b(k-m)g(m)(t), where Xi(k) is the complex-valued receiver output, b(k-m) is the transmitted symbol, N-k is the complex-valued output noise due to AWGN, and g(m)(t) is the time-varying gain of b(k-m) Statistical characteristics of N-k and g(m)(t) are derived. It is found that {N-k} is a zero-mean complex Gaussian sequence, and g(m)(t)s For All m follow a wide-sense-stationary, jointly complex GAussian random process. Simple closed-form formulas computing statistical parameters of N-k and g(m)(t)s are derived. Several aspects regarding the use of the proposed model to analytic works and efficient computer simulations are discussed. Finally, three illustrative examples are given.

关键词： discrete-time model frequency-selective Rician fading WSSUS channel intersymbol interference

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Community detection in signed networks based on discrete-time model

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Chinese Physics B 2017年第1期26卷 574-583页

作者： Jianrui Chen Li Zhang Weiwei Liu Zaizai Yan College of Science Inner Mongolia University of Technology Hohhot 010051 China

Community detection in signed networks has been studied widely in recent years. In this paper, a discrete difference equation is proposed to imitate the consistently changing phases of the nodes. During the interaction, each node will update its phase based on the difference equation. Each node has many different nodes connected with it, and these neighbors have different influences on it. The similarity between two nodes is applied to describe the influences between them. Nodes with high positive similarities will get together and nodes with negative similarities will be far away from each *** are detected ultimately when the phases of the nodes are stable. Experiments on real world and synthetic signed networks show the efficiency of detection performance. Moreover, the presented method gains better detection performance than two existing good algorithms.

关键词： community detection signed networks discrete-time model similarity

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A REPRESENTATIVE discrete-time model FOR UNCOVERING SLOW AND FAST SCALE INSTABILITIES IN BOOST POWER FACTOR CORRECTION AC-DC PRE-REGULATORS

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INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS 2008年第10期18卷 3073-3092页

作者： El Aroudi, Abdelali Orabi, Mohamed Martinez-Salamero, Luis Univ Rovira & Virgili Dept Engn Elect Elect & Automat Tarragona Spain

Boost Power Factor Correction (PFC) AC-DC converter under fixed frequency average current control is a nonlinear and nonautonomous dynamical system characterized by two different forcing periods and thus by two different scales of time. Four different kinds of standard instability phenomena are possible for this system, depending on the parameters of the circuit. A combination of more than one instability phenomenon can also take place. In this paper, we carry out a careful and an accurate modeling of the system. First, we put into evidence most of the nonlinear behaviors that could occur in the system by using the switched circuit-based model and then we derive a unified representative discrete-time model that is able to predict accurately all these behaviors.

关键词： PFC applications stability analysis discrete-time model bifurcations AC-DC boost pre-regulators torus doubling

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Discretization of Nonautonomous Nonlinear Systems Based on Continualization of an Exact discrete-time model

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JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME 2014年第2期136卷 021004页

作者： Triet Nguyen-Van Hori, Noriyuki Univ Tsukuba Digital Control Lab Grad Sch Syst & Informat Engn Tsukuba Ibaraki 3058573 Japan

An innovative approach is proposed for generating discrete-time models of a class of continuous-time, nonautonomous, and nonlinear systems. By continualizing a given discrete-time system, sufficient conditions are presented for it to be an exact model of a continuous-time system for any sampling periods. This condition can be solved exactly for linear and certain nonlinear systems, in which case exact discrete-time models can be found. A new model is proposed by approximately solving this condition, which can always be found as long as a Jacobian matrix of the nonlinear system exists. As an example of the proposed method, a van der Pol oscillator driven by a forcing sinusoidal function is discretized and simulated under various conditions, which show that the proposed model tends to retain such key features as limit cycles and space-filling oscillations even for large sampling periods, and out-performs the forward difference model, which is a well-known, widely-used, and on-line computable model.

关键词： discretization continualization nonlinear system discrete-time model van der Pol oscillator

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An Improved discrete-time model for Heterogeneous High-Speed Train Traffic Flow

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Communications in Theoretical Physics 2016年第3期65卷 381-392页

作者：许琰贾斌李明华李新刚 State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University School of Traffic and Transportation Beijing Jiaotong University

This paper aims to present a simulation model for heterogeneous high-speed train traffic flow based on an improved discrete-time model（IDTM）.In the proposed simulation model,four train control strategies,including departing strategy,traveling strategy,braking strategy,overtaking strategy,are well defined to optimize train *** on the proposed simulation model,some characteristics of train traffic flow are *** results indicate that the departure time intervals,the station dwell time,the section length,and the ratio of fast trains have different influence on traffic capacity and train average *** results can provide some theoretical support for the strategy making of railway departments.

关键词： discrete-time model heterogeneous train traffic flow control strategy simulation

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A discrete-time model for common lifetime inventory systems

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MATHEMATICS OF OPERATIONS RESEARCH 2005年第3期30卷 718-732页

作者： Lian, ZT Liu, LM Neuts, MF Univ Macau Fac Business Adm Macao Peoples R China Hong Kong Univ Sci & Technol Dept Ind Engn & Engn Management Hong Kong Hong Kong Peoples R China Univ Arizona Dept Syst & Ind Engn Tucson AZ 85721 USA

We consider a discrete-time (s, S) inventory model in which the stored items have a random common lifetime with a discrete phase-type distribution. Demands arrive in batches following a discrete phase-type renewal process. With zero lead time and allowing backlogs, we construct a multidimensional Markov chain to model the inventory-level process. We obtain a closed-form expected cost function. Numerical results demonstrate some properties of optimal ordering policies and cost functions. When compared with the results for the constant lifetime model, the variance of the lifetime significantly affects the system behavior. Thus, the formalism that we create here adds a new dimension to the research in perishable inventory control under uncertainty in lifetime.

关键词： perishable inventory random common lifetime discrete-time model optimization

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Sensorless predictive current control with a charge balance current estimator for boost converters based on discrete-time model considering current ripple

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IET POWER ELECTRONICS 2018年第13期11卷 2063-2071页

作者： Chen, Chen Tong, Qiaoling Min, Run Zhang, Qiao Zou, Xuecheng Liu, Zhenglin Wuhan Univ Sci & Technol Sch Informat Sci & Engn Wuhan 430081 Hubei Peoples R China Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Hubei Peoples R China Wuhan Univ Technol Sch Automat Wuhan 430070 Hubei Peoples R China

The performance of a sensorless predictive current controlled boost converter is usually susceptible to the accuracy of the employed converter and current estimator models. Since the accuracy of conventional current estimator would be degraded due to parasitic parameter variations, a charge balance current estimator (CBCE) is proposed to overcome this issue. Its estimation of peak inductor current is based on the charge balance principle of output capacitor and characteristics of inductor current ripple. Only one parasitic parameter - capacitor equivalent series resistance (ESR) is used in CBCE. Furthermore, the capacitor ESR is also estimated together with output load by a proposed equivalent load estimation scheme which can improve the current estimation accuracy. Besides, to achieve a high dynamic performance digital control, a discrete-time model considering current ripple is developed, in which the ripple is taken into account rather than treats inductor current as a constant in each switching cycle. It can achieve a higher accuracy than conventional averaged model, especially in the high-frequency region. Finally, its effectiveness is verified by simulation and experiment results.

关键词： capacitors switching convertors predictive control electric current control inductors digital control DC-DC power convertors power convertors charge balance principle inductor current ripple parasitic parameter - capacitor equivalent series resistance equivalent load estimation scheme current estimation accuracy high dynamic performance digital control discrete-time model current control charge balance current estimator boost converters sensorless predictive current controlled boost converter employed converter current estimator models conventional current estimator peak inductor current

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Stability connection between sampled-data fuzzy control systems with quantization and their approximate discrete-time model

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AUTOMATICA 2009年第6期45卷 1518-1523页

作者： Kim, Do Wan Lee, Ho Jae Inha Univ Sch Elect Engn Inchon 402751 South Korea Yonsei Univ Dept Elect & Elect Engn Seoul 120749 South Korea

This paper concerns the stability of a sampled-data Takagi-Sugeno (T-S) fuzzy control system with quantization, when a controller design is based on an approximate discrete-time model of the plant without quantization. The motivations come from the facts that digital devices for interfacing a plant with a controller quantize signals and an exact discrete-time model of the T-S fuzzy system is generally not amenable to synthesis process. We show that the concerned system is Lagrange stabilizable by the controller asymptotically stabilizing the approximate discrete-time model. A constructive design algorithm for the developed stability analysis is proposed in terms of linear matrix inequalities. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Takagi-Sugeno (T-S) fuzzy system Sampled-data control discrete-time model Quantization Stability

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Active stabilisation design of DC-DC converters with constant power load using a sampled discrete-time model: stability analysis and experimental verification

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IET POWER ELECTRONICS 2018年第9期11卷 1519-1528页

作者： Gavagsaz-Ghoachani, Roghayeh Saublet, Louis-Marie Phattanasak, Matheepot Martin, Jean-Philippe Nahid-mobarakeh, Babak Pierfederici, Serge Shahid Beheshti Univ Dept Renewable Energies Engn Tehran Iran Univ Lorraine GREEN Vandoeuvre Les Nancy France King Mongkuts Univ Technol RERC North Bangkok Thailand Univ Lorraine LEMTA Vandoeuvre Les Nancy France

Instabilities of cascade converters with an LC filter in between in power electronic systems have been known, and many answers have been proposed. The load converters are tightly regulated, acting as constant power loads (CPLs). Average models are generally utilised to study the behavior of the converters. For embedded applications, the weight and the volume should be reduced. Consequently, in this case, the limitations of the average method are reached when the cut-off frequency of the LC input filter is close to the switching frequency. Then, other tools are necessary to study this type of system. To overcome this problem, a discrete-time model was developed to study the behavior of the system, taking into account the switching effect. The aim was to enlarge the power range of the stability zone for a DC system composed of a DC-DC boost converter as a source converter, which was connected to the power load via an LC input filter. For this purpose, a stabilisation expression is integrated in the command of the source converter. The stability analysis by the eigenvalues of the system is described using the proposed model. Simulation and experimental results are discussed to verify the proposed stabiliser in different cases.

关键词： power convertors power electronics DC-DC power convertors eigenvalues and eigenfunctions active stabilisation design DC-DC converters constant power load discrete-time model stability analysis experimental verification cascade converters load converter filter power electronic systems average models average method cut-off frequency LC input filter switching frequency account the switching effect power range stability zone DC system DC-DC boost converter source converter

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