1,721,492 research outputs found
Model-based and data-based frequency domain design of fixed structure robust controller: a polynomial optimization approach
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A Unified Framework for the <i>H</i><sub>∞</sub> Mixed-Sensitivity Design of Fixed Structure Controllers through Putinar Positivstellensatz
Full text linkIn this paper, we present a novel technique to design fixed structure controllers, for both continuous-time and discrete-time systems, through an H∞ mixed sensitivity approach. We first define the feasible controller parameter set, which is the set of the controller parameters that guarantee robust stability of the closed-loop system and the achievement of the nominal performance requirements. Then, thanks to Putinar positivstellensatz, we compute a convex relaxation of the original feasible controller parameter set and we formulate the original H∞ controller design problem as the non-emptiness test of a set defined by sum-of-squares polynomials. Two numerical simulations and one experimental example show the effectiveness of the proposed approach
Wheat Markets and Price Stabilisation in Pakistan: An Analysis of Policy Options
Full text linkThis article provides a quantitative analysis of the effects of Pakistan government domestic wheat procurement, sales, and trade policies on wheat supply, demand, prices, and overall inflation. Analysis of price multipliers indicates that increases in wheat procurement prices (one means of promoting domestic procurement) have relatively small effects on overall price levels. Partial equilibrium analysis of wheat markets suggests that fluctuations in production, rather than market manipulation, are plausible explanations for price increases in recent years. Comparisons of domestic and international prices suggest that promoting private sector imports is one alternative for increasing supply and stabilising market prices, particularly in years of production shortfalls. Overall, this paper concludes that market forces play a dominant role in price determination in Pakistan, and that policies that promote the private sector wheat trade can both increase price stability and reduce fiscal costs.Wheat; Agricultural prices; Pakistan
Transcatheter closure of tubular patent ductus arteriosus using muscular ventricular septal defect devices in infants and small children with congestive heart failure
No full textBackground. - Transcatheter closure of a patent ductus arteriosus in children is widely performed to reduce symptoms and decrease the risk of endocarditis. Most arterial ducts are closed successfully with dedicated devices. However, in a tubular or "type C'' patent ductus with congestive heart failure, the occlusion is more challenging with these devices, with a higher risk of complications, such as aortic or left pulmonary stenosis and deviceembolization.Aim. - To report our experience with muscular ventricular septal defect devices for patentductus arteriosus occlusion in small children.Methods. - Retrospective observational series of patients weighing < 10 kg, with a tubularpatent ductus arteriosus (type C) and congestive heart failure, who underwent transcatheterclosure with a muscular ventricular septal defect device between 2017 and 2019.Results. - Eight patients were included. The mean age and weight at closure were 6.3 months( range 1-18 months) and 5.3 kg (range 2.4-8.2 kg), respectively. All patent ductus arteriosuswere occluded successfully using Occlutech (R) (N = 3) or Amplatzer (R) (N = 5) muscular ventricularseptal defect devices. In four cases, the muscular ventricular septal defect device was used afterfailure to close the patent ductus arteriosus with a dedicated patent ductus arteriosus device. Two patients had mild left pulmonary artery stenosis, with a maximum velocity on continuousDoppler of 3 m/s and 2.7 m/s, respectively. After a mean follow-up of 28 months (range 14-41months), all patients were asymptomatic with excellent results. The mild pulmonary stenosisimproved, with a maximum velocity of 2.3 m/s in both patients.Conclusions. - Closure of tubular patent ductus arteriosus in small children with congestiveheart failure using a muscular ventricular septal defect device is safe in this preliminary experience. Further studies with more patients are warranted. (c) 2022 Published by Elsevier Masson SAS
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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