16,251 research outputs found
Order reduction approaches for the algebraic Riccati equation and the LQR problem
We explore order reduction techniques for solving the algebraic Riccati
equation (ARE), and investigating the numerical solution of the
linear-quadratic regulator problem (LQR). A classical approach is to build a
surrogate low dimensional model of the dynamical system, for instance by means
of balanced truncation, and then solve the corresponding ARE. Alternatively,
iterative methods can be used to directly solve the ARE and use its approximate
solution to estimate quantities associated with the LQR. We propose a class of
Petrov-Galerkin strategies that simultaneously reduce the dynamical system
while approximately solving the ARE by projection. This methodology
significantly generalizes a recently developed Galerkin method by using a pair
of projection spaces, as it is often done in model order reduction of dynamical
systems. Numerical experiments illustrate the advantages of the new class of
methods over classical approaches when dealing with large matrices
Modulation of a surface plasmon-polariton resonance by sub-terahertz diffracted coherent phonons
Coherent sub-THz phonons incident on a gold grating that is deposited on a
dielectric substrate undergo diffraction and thereby induce an alteration of
the surface plasmon-polariton resonance. This results in efficient
high-frequency modulation (up to 110 GHz) of the structure's reflectivity for
visible light in the vicinity of the plasmon-polariton resonance. High
modulation efficiency is achieved by designing a periodic nanostructure which
provides both plasmon-polariton and phonon resonances. Our theoretical analysis
shows that the dynamical alteration of the plasmon-polariton resonance is
governed by modulation of the slit widths within the grating at the frequencies
of higher-order phonon resonances.Comment: 5 pages, 4 figure
Scientific complications and controversies noted in the field of CdS/CdTe thin film solar cells and the way forward for further development
Cadmium telluride-based solar cell is the most successfully commercialised thin film solar cell today. The laboratory-scale small devices have achieved ~â22%, and commercial solar panels have reached ~â18% conversion efficiencies. However, there are various technical complications and some notable scientific contradictions that appear in the scientific literature published since the early 1970s. This review paper discusses some of these major complications and controversies in order to focus future research on issues of material growth and characterisation, post-growth processing, device architectures and interpretation of the results. Although CdTe can be grown using more than 14 different growth techniques, successful commercialisation has been taken place using close-space sublimation and electrodeposition techniques only. The experimental results presented in this review are mainly based on electrodeposition. Historical trends of research and commercial successes have also been discussed compared to the timeline of novel breakthroughs in this field. Deeper understanding of these issues may lead to further increase in conversion efficiencies of this solar cell. Some novel ideas for further development of thin film solar cells are also discussed towards the end of this paper
Historical geography II: traces remain
The second report in this series turns to focus on the trace in relation to life-writing and biography in historical geography and beyond. Through attention to tracing journeys, located moments and listening to the presence of ghosts (Ogborn, 2005), this report seeks to highlight the range of different ways in which historical geographers have explored lives, deaths, and their transient traces through varied biographical terrains. Continuing to draw attention in historical geography to the darkest of histories, this piece will pivot on moments of discovering the dead to showcase the nuanced ways in which historical geography is opening doors into uncharted lives and unspoken histories
Increased use of malaria rapid diagnostic tests improves targeting of anti-malarial treatment in rural Tanzania: implications for nationwide rollout of malaria rapid diagnostic tests.
ABSTRACT: BACKGROUND: The World Health Organization recommends parasitological confirmation of all malaria cases. Tanzania is implementing a phased rollout of malaria rapid diagnostic tests (RDTs) for routine use in all levels of care as one strategy to increase parasitological confirmation of malaria diagnosis. This study was carried out to evaluated artemisinin combination therapy (ACT) prescribing patterns in febrile patients with and without uncomplicated malaria in one pre-RDT implementation and one post-RDT implementation area. METHODS: A cross-sectional health facility surveys was conducted during high and low malaria transmission seasons in 2010 in both areas. Clinical information and a reference blood film on all patients presenting for an initial illness consultation were collected. Malaria was defined as a history of fever in the past 48 hours and microscopically confirmed parasitaemia. Routine diagnostic testing was defined as RDT or microscopy ordered by the health worker and performed at the health facility as part of the health worker-patient consultation. Correct diagnostic testing was defined as febrile patient tested with RDT or microscopy. Over-testing was defined as a febrile patient tested with RDT or microscopy. Correct treatment was defined as patient with malaria prescribed ACT. Over-treatment was defined as patient without malaria prescribed ACT. RESULTS: A total of 1,247 febrile patients (627 from pre-implementation area and 620 from post-implementation area) were included in the analysis. In the post-RDT implementation area, 80.9% (95% CI, 68.2-89.3) of patients with malaria received recommended treatment with ACT compared to 70.3% (95% CI, 54.7-82.2) of patients in the pre-RDT implementation area. Correct treatment was significantly higher in the post-implementation area during high transmission season (85.9% (95%CI, 72.0-93.6) compared to 58.3% (95%CI, 39.4-75.1) in pre-implementation area (p=0.01). Over-treatment with ACT of patients without malaria was less common in the post-RDT implementation area (20.9%; 95% CI, 14.7-28.8) compared to the pre-RDT implementation area (45.8%; 95% CI, 37.2-54.6) (p<0.01) in high transmission. The odds of overtreatment was significantly lower in post- RDT area (adjusted Odds Ratio (OR: 95%CI) 0.57(0.36-0.89); and much higher with clinical diagnosis adjusted OR (95%CI) 2.24(1.37-3.67) CONCLUSION: Implementation of RDTs increased use of RDTs for parasitological confirmation and reduced over-treatment with ACT during high malaria transmission season in one area in Tanzania. Continued monitoring of the national RDT rollout will be needed to assess whether these changes in case management practices will be replicated in other areas and sustained over time. Additional measures (such as refresher trainings, closer supervisions, etc) may be needed to improve ACT targeting during low transmission seasons
Importance of implant technique on risk of major paravalvular leak (PVL) after St. Jude mechanical heart valve replacement: a report from the Artificial Valve Endocarditis Reduction Trial (AVERT)
Objective: To examine risk factors for major paravalvular leak (PVL) events after mechanical heart valve replacement. Methods: We analyzed outcome of 807 patients randomized into the Artificial Valve Endocarditis Reduction Trial (AVERT). The mean follow-up time was 30.6 months and 21 major PVL events were reported. Three additional major PVL events associated with endocarditis were excluded from analysis. All baseline medical history variables, as well as operative parameters (including use of pledgets and suture technique) were examined using Cox regression. Results: Major PVL was reported after 11 aortic, 9 mitral, and 1 double valve replacement. 6/404 (1.5%) patients with conventional valves experienced a major PVL event versus 15/403 (3.7%) in the Silzone group. 10/172 (5.8%) patients with valve suture technique without pledgets experienced a major PVL event versus 11/635 (1.7%) patients with pledgets. Final multivariable model showed that only suture technique without pledgets (p = 0.005) was an independent significant risk factor for major PVL events. Silzone cuff showed a strong trend (p = 0.055). Conclusions: Suture technique without pledgets is an independent significant risk factor for major PVL events. In this study, use of pledgets during valve replacement had a protective effect against subsequent paravalvular leak, supporting the use of buttress reinforcement for valve suture. The use of Silzone cuff, although not statistically significant, showed a strong trend as a risk facto
A global fit of and elastic scattering in ChPT with dispersion relations
We apply the one-loop results of the ChPT suplemented
with the inverse amplitude method to fit the available experimental data on
and scattering. With esentially only three parameters we
describe accurately data corresponding to six different channels, namely
and . In addition we
reproduce the first resonances of the and channel with the
right mass corresponding to the and the particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9
Lessons from Love-Locks: The archaeology of a contemporary assemblage
This document is the Accepted Manuscript version. The final, definitive version of this paper has been published in Journal of Material Culture, November 2017, published by SAGE Publishing, All rights reserved.Loss of context is a challenge, if not the bane, of the ritual archaeologistâs craft. Those who research ritual frequently encounter difficulties in the interpretation of its often tantalisingly incomplete material record. Careful analysis of material remains may afford us glimpses into past ritual activity, but our often vast chronological separation from the ritual practitioners themselves prevent us from seeing the whole picture. The archaeologist engaging with structured deposits, for instance, is often forced to study ritual assemblages post-accumulation. Many nuances of its formation, therefore, may be lost in interpretation. This paper considers what insights an archaeologist could gain into the place, people, pace, and purpose of deposition by recording an accumulation of structured deposits during its formation, rather than after. To answer this, the paper will focus on a contemporary depositional practice: the love-lock. This custom involves the inscribing of names/initials onto a padlock, its attachment to a bridge or other public structure, and the deposition of the corresponding key into the water below; a ritual often enacted by a couple as a statement of their romantic commitment. Drawing on empirical data from a three-year diachronic site-specific investigation into a love-lock bridge in Manchester, UK, the author demonstrates the value of contemporary archaeology in engaging with the often enigmatic material culture of ritual accumulations.Peer reviewe
Justice at Sea: Fishersâ politics and marine conservation in coastal Odisha, India
This is a paper about the politics of fishing rights in and around the Gahirmatha marine sanctuary in coastal Odisha, in eastern India. Claims to the resources of this sanctuary are politicised through the creation of a particularly damaging narrative by influential Odiya environmental actors about Bengalis, as illegal immigrants who have hurt the ecosystem through their fishing practices. Anchored within a theoretical framework of justice as recognition, the paper considers the making of a regional Odiya environmentalism that is, potentially, deeply exclusionary. It details how an argument about âillegal Bengalisâ depriving âindigenous Odiyasâ of their legitimate âtraditional fishing rightsâ derives from particular notions of indigeneity and territory. But the paper also shows that such environmentalism is tenuous, and fits uneasily with the everyday social landscape of fishing in coastal Odisha. It concludes that a wider class conflict between small fishers and the state over a sanctuary sets the context in which questions about legitimate resource rights are raised, sometimes with important effects, like when out at sea
Existence of Heavy Fermions in the Antiferromagnetic Phase of CeIn3
We report the pressure-dependent optical conductivity spectra of a heavy
fermion (HF) compound CeIn3 below the Neel temperature of 10 K to investigate
the existence of the HF state in the antiferromagnetic (AFM) phase. The peak
due to the interband transition in the hybridization gap between the conduction
band and nearly localized 4f states (c-f hybridization) appears at the photon
energy of about 20 meV not only in the HF regime but also in the AFM regime.
Both the energy and intensity of the c-f hybridization peak continuously
increase with the application of pressure from the AFM to the HF regime. This
result suggests that the c-f hybridization, as well as the heavy fermions,
exists even in the AFM phase of CeIn3.Comment: 5 pages, 3 figure
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