Model order reduction for neutral systems by moment matching

published_or_final_versio

A decade of vector fitting development: Applications on signal/power integrity

This issue also has title: IAENG transactions on engineering technologies, volume 5: Special Edition of the International MultiConference of Engineers and Computer Scientists 2009International MultiConference of Engineers and Computer Scientists 2010, Hong Kong, China, 17-19 March 2010Vector Fitting (VF) has been introduced as a partial-fraction basis response fitting methodology for over a decade. Because of its reliability and versatility, VF has been applied and extended to a number of areas. In this book chapter, we will discuss the applications of VF in the context of macromodeling of linear structures in signal/power integrity analyses. We will also discuss main features of VF along three directions: data, algorithms and models. Two practical examples are given to demonstrate the merits of VF. An alternative P-norm approximation criterion is proposed to enhance the accuracy of the macromodeling process. © 2010 American Institute of Physics.published_or_final_versio

On Vector Fitting methods in signal/power integrity applications

This conference proceedings appears in: Lecture Notes in Engineering and Computer Science. Open-access online version: http://www.iaeng.org/publication/IMECS2010/Vector Fitting (VF) has been applied to reformulate traditional system identification techniques by introducing a partial-fraction basis to avoid ill-conditioned calculation in broadband system identifications. Because of the reliable and versatility of VF, many extensions and applications have been proposed, for example, the macromodeling of linear structures in signal/power integrity analyses. In this paper, we discuss the macromodeling framework and some main features in VF in terms of data, algorithms and models. Finally, an alternative P-norm approximation criterion is proposed to enhance the macromodeling process.postprintThe International MultiConference of Engineers and Computer Scientists (IMECS 2010), Hong Kong, 17-19 March 2010. In Proceedings of the International MultiConference of Engineers and Computer Scientists, 2010, v. 2, p. 1407-141

Fast nonlinear model order reduction via associated transforms of high-order volterra transfer functions

We present a new and fast way of computing the projection matrices serving high-order Volterra transfer functions in the context of (weakly and strongly) nonlinear model order reduction. The novelty is to perform, for the first time, the association of multivariate (Laplace) variables in high-order multiple-input multiple-output (MIMO) transfer functions to generate the standard single-s transfer functions. The consequence is obvious: instead of finding projection subspaces about every s i, only that about a single s is required. This translates into drastic saving in computation and memory, and much more compact reduced-order nonlinear models, without compromising any accuracy. © 2012 ACM.published_or_final_versio

Alteraçães ponderais, hemodinâmicas e da função vascular do leito arterial caudal em ratas sete dias após o infarto do miocárdio

A área do infarto (AI) é um importante determinante para o desenvolvimento da insuficiência cardíaca (IC). Entretanto, estudos do nosso laboratório vêem mostrando que nem sempre a IC se correlaciona com a AI. O objetivo deste trabalho foi avaliar o desenvolvimento da IC sete dias após o infarto, e suas repercussões sobre a reatividade vascular no leito caudal de ratas. Ratas Wistar foram divididas em grupo controle (CT); cirurgia fictícia (SHAM); e o grupo submetido ao infarto do miocárdio (INF). Posteriormente, o grupo INF foi subdividido entre animais que desenvolveram (INF-IC) ou não (INF) IC. Após sete dias, os animais foram anestesiados e cateterizados para avaliações da pressão arterial e função ventricular esquerda. Em seguida, o leito arterial caudal foi removido e perfundido sob fluxo constante de 2,5 mL/min. Alterações na pressão de perfusão média (PPM) foram obtidas após doses crescentes de fenilefrina (FE 0,0001-300&#956;g), antes e depois da lesão endotelial induzida pelo CHAPS. Para avaliação da liberação basal de óxido nítrico (NO) foi utilizado L-NAME na presença de FE. Concentrações crescentes de acetilcolina (ACh) e nitroprussiato de sódio (NPS), foram perfundidas após pré-contração com KCl (65mM) para avaliação do relaxamento dependente e independente do endotélio vascular, respectivamente. Os dados estão apresentados como média ± erro padrão da média, e a significância estatística fixada em P0,05). A variação do PC durante os sete dias correlacionou-se com a PDFVE (r= -0,592; P<0,05). No leito arterial caudal o grupo INF-IC apresentou redução da resposta máxima (Rmáx) à FE (330,4±13,4 mmHg) quando comparado aos demais grupos (CT: 423,2±25,4; SHAM: 403,6±28; IM: 425,5±30,4; P<0,05). A liberação basal de NO obtida pelo grupo INF-IC (13,35 ± 2,31) foi significativamente maior quando comparado aos demais grupos (CT 7,40 ± 1,36; SHAM 7,23 ± 0,8; INF 3,77 ± 0,7; P< 0,05). O relaxamento a ACh mostrou-se prejudicado nos grupos SHAM e IM (SHAM: 50,0±2,8; INF: 48,4±2,7 %), quando comparados ao grupo CT e INF-IC (CT: 69,1±4,0; INF-IC: 66,9±3,4%; P<0.05). Conclui-se que aos sete dias após o infarto do miocárdio já é possível identificar animais que, com a mesma área de lesão, desenvolvem ou não insuficiência cardíaca precocemente. Além disso, esses animais apresentam diferentes respostas vasculares devido, em parte, a maior biodisponibilidade endotelial de NO

Metasurface-based Modulation with Enhanced Interference Resilience

Reconfigurable Intelligent Surfaces (RISs) have great potential for Internet of Things (IoT) applications due to their cost-effectiveness and energy-efficiency. However, under the application of RIS, current RIS systems cannot actively predict and avoid interference, as evolving interference signals can dynamically change their frequency bands. To address this issue, we develop a learning-based dynamic RIS spectrum access scheme to avoid interference and enhance wireless transmission reliability. An intelligent metasurface-based modulation (MM) is designed for generating and reflecting anti-interference radio-frequency signals. Specifically, a Dyna-Q algorithm is employed at the RIS controller to learn the frequency of interference signals, which is used to determine the frequency of the carrier signals. Experiments are conducted on the proposed RIS demo system to evaluate its anti-interference capability, and the results show that our scheme leads to an increase of at least 50% in the system throughput. These numerical results demonstrate the effectiveness of proposed scheme

Prevalence of acute dizziness and vertigo in cortical stroke

BACKGROUND: In posterior circulation stroke, vertigo can be a presenting feature. However, whether isolated hemispheric strokes present with vertigo is less clear, despite a few single case-reports in the literature. Here we, a) explored the prevalence of vertigo/dizziness in acute stroke and, b) considered the cortical distribution of these lesions in relation to both the known vestibular cortex and evolution of these symptoms. METHODS: We conducted structured interviews in 173 consecutive unselected patients admitted to the hyperacute stroke unit at the University College London Hospitals. The interview was used to evaluate whether the patient was suffering from dizziness and/or vertigo before the onset of the stroke and at the time of the stroke (acute dizziness/vertigo), and the nature of these symptoms. RESULTS: 112 patients had subcortical lesions and 53 patients had cortical infarcts, of which 21 patients reported acute dizziness. Out of these 21, five patients reported rotational vertigo. 17 of the total 53 patients had lesions in known vestibular cortical areas distributed within the insular and parietal opercular cortices. CONCLUSIONS: The prevalence of vertigo in acute cortical strokes was 9%, with no single locus of lesion overlap. There is growing evidence supporting a lateralised vestibular cortex, with speculation that cortical strokes affecting the right hemisphere, are more likely to cause vestibular symptoms than left-hemispheric strokes. We observed a trend for this association, with the right hemisphere affected in four of five patients who reported spinning vertigo at the onset of the stroke