Cascarano, PasqualePiccolomini, Elena LoliMorotti, ElenaSebastiani, Andrea...
15页
查看更多>>摘要：Blur and noise corrupting Computed Tomography (CT) images can hide or distort small but important details, negatively affecting the consequent diagnosis. In this paper, we present a novel gradient-based Plug-and-Play (PnP) algorithm and we apply it to restore CT images. The plugged denoiser is implemented as a deep Convolutional Neural Network (CNN) trained on the gradient domain (and not on the image one, as in state-of-the-art works) and it induces an external prior onto the restoration model. We further consider a hybrid scheme which combines the gradient-based external denoiser with an internal one, obtained from the Total Variation functional. The proposed frameworks rely on the Half Quadratic Splitting scheme and we prove a general fixed-point convergence theorem, under weak assumptions on both the denoisers. The experiments confirm the effectiveness of the proposed gradient-based approach in restoring blurred noisy CT images, both in simulated and real medical settings. The obtained performances outperform the achievements of many state-of-the-art methods. (c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：A Cayley digraph Cay(G, S) of a finite group G with respect to a subset S of G , where S does not contain the identity 1 of G , is said to be a CI-digraph, if Cay(G,S) expressionpproximexpressiontely equexpressionl to Cay(G, T ) implies that G has an automorphism mapping S to T . The group G is called a DCI-group or an NDCI-group if all Cayley digraphs or normal Cayley digraphs of G are CI-digraphs. We prove in this paper that a generalized quaternion group Q(4n) of order 4 n is an NDCI-group if and only if n = 2 or n is odd. As a result, we show that if Q(4n) is a DCI-group then n = 2 or n is odd-square-free. (c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：While there are a large variety of effective methods developed for solving more traditional minimization problems, much less success has been reported in solving the mini max problem minmax(u is an element of U v is an element of V) f (u, v ) where U x V is a fixed interval domain in R-n . Most of the existing work deal with a discrete V or even a finite V . Continuous minimax problems can be applied to engineering, finance, and other fields. Sainz in 2008 proposed a modal interval algorithm based on their semantic extensions to solve continuous minimax problems. We developed an improved algorithm using modal intervals to solve unconstrained continuous minimax problems. A new interval method is introduced by taking advantage of both the original minimax problem and its dual problem. After theoretical analysis of major issues, the new algorithm is implemented in the framework of uniform partition of the search domain. Various improvement techniques including more bisecting choices, sampling methods, and deletion conditions are applied to make the new method more powerful. Preliminary numerical results provide promising evidence of its effectiveness. (c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：Tuberculosis is a chronic infectious disease with a high death rate, which has attracted worldwide attention. In this paper, we focus on the annual data of tuberculosis in the United States from 1988 to 2019. Firstly, we propose an SV EIT R dynamical model with vaccination, fast and slow progression, incomplete treatment, and relapse. Mathematical analyses show that the disease-free equilibrium is globally asymptotically stable (unstable) if R 0 <= 1 (if R 0 > 1 ). There exists a unique endemic equilibrium that is globally asymptotically stable when R 0 > 1 . Next, we use the Markov-chain Monte-Carlo (MCMC) method to acquire the model's optimal parameters. From R 0 = 1 . 3763 , tuberculosis will not be eliminated without control measures taken in the United States. Through partial rank correlation analysis, the most sensitive parameters to the basic reproduction number are found. Based on this, we take the actual epidemic situation of tuberculosis in the United States into considerations to get the required conditions for optimal control using Pontryagin's maximum principle and cost-effectiveness analysis. Implementation of three public health measures: tuberculosis prevention and control education, timely treatment, and enhanced efficacy can reduce the prevalence of tuberculosis in the United States. But at present, it is challenging for us to achieve the goal of eliminating tuberculosis by 2030 as called for by WHO.(c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：This article addresses the adaptive event-triggered output-feedback control issue for a class of switched stochastic nonlinear systems (SSNSs) under arbitrary switchings. To cope with the unknown growth rate, two dynamic gains are introduced. Different from most exist-ing event-triggered strategies, the developed dynamic event-triggered strategy can be dy-namically adjusted, which is delicately designed by exploiting two dynamic gains and a decaying function. Then, a new event-triggered output-feedback controller (ETOFC) is es-tablished, which can guarantee that all states of the closed-loop system converge to the origin almost surely (a.s.). Finally, two examples are given to verify the effectiveness of the presented control scheme.(c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：This paper intents to investigate the problem of mean-square stability analysis of Markovian jump systems with generally unknown and uncertain transition rates. Different from pervious works that the transition rates from one mode to others may be partially unknown or uncertain, in this note, the case that the transition rates from one mode to others are totally unknown will be investigated. By means of transition rate estimation, two ways are provided to tackle with the totally unknown case. In general, five cases in the transition rates matrix are studied for the mean-square stability analysis, which almost have covered all types of generally unknown and uncertain transition rates. Simultaneously, corresponding conditions for checking the mean-square stability of the considered Markovian jump systems are developed for the five studied cases. Finally, numerical examples are provided to verify the effectiveness of the proposed results. (c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：Under the semi-tensor product method, this paper investigates the robust set stability and robust set stabilization problems for a class of probabilistic Boolean control networks (PBCNs) with disturbances. First, an algorithm to determine the largest robust invariant set (LRIS) of a given set for a PBN with probability one is proposed, and the necessary and suf-ficient conditions to detect whether the PBN is globally finite-time stable to this invariant set with probability one are established. Second, the PBNs with control inputs are consid-ered, and an algorithm for the largest robust control invariant set (LRCIS) with probability one is provided, based on which, some necessary and sufficient conditions for finite-time robust set stabilization with probability one of PBCNs are presented. Furthermore, the de-sign scheme of time-optimal state feedback stabilizers via antecedence solution technique is derived. The study of illustrative examples shows the effectiveness of the obtained new results.(c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：The propagation of a current-fed string in 3-dimensional space interacting with an external magnetic field is described by the system of coupled Konno-Oono equations. Present research deals with the formation of one, two, and three dimensional optimal sub-algebras of the system. Then invariants are decided by using the Killing form. Similarity reductions and their solutions are determined for each sub-algebra. For strong integrability of the system, conserved vectors are also attained by using Noether's theorem. The novelty of analytical solutions can be demonstrated by the fact that in earlier studies, all researchers solved coupled Konno-Oono equations involving only two components of the water wave, but in this study, the authors solved its more general form. Some comments are also made to demonstrate that the results in this article are preferable to those in previous studies. To make the solutions physically meaningful, they are reinforced with numerical simulation. Periodic, single soliton, doubly bright, bright and dark multisolitons, asymptotic, travelling waves with dark soliton, progressive, highly progressive, and stationary solutions can be seen in the profiles. Such solutions can be beneficial in optical nonlinearity, electromagnetics, and quantum fields.(c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：New integral equations are proposed to determine first-passage-time densities for timeinhomogeneous birth-death processes. Such equations, particularly suitable for computational purposes, are also used to obtain closed-form expressions for the first-passage-time densities of special birth-death processes of interest in various application fields.(c) 2022 Elsevier Inc. All rights reserved.
查看更多>>摘要：In this paper, distributed output feedback consensus tracking control of multiple nonholonomic mobile robots with limited information of leader is studied. Different from the existing results, the considered consensus problem has the following features: (i) each robot is described by a second-order dynamic model with parametric uncertainty and external disturbances, (ii) the global information of the directed graphs is not required, (iii) only the position of the leader is available for a subset of robots and thus its velocity information is no longer needed. To solve such a problem, an adaptive output feedback control scheme which involves estimator, observer and controller design is proposed. A fully distributed estimator is constructed to estimate the position of the leader for each robot. Based on the estimated information, an adaptive observer-based output feedback controller is designed to realize consensus tracking. It is shown that the boundedness of all the signals in the resulting closed-loop system is guaranteed, and the consensus tracking error of the system converges to an adjustable neighborhood of zero by appropriately choosing design parameters. Simulation results are provided to verify the effectiveness of the proposed scheme. (c) 2022 Elsevier Inc. All rights reserved.
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