64 research outputs found
On linear convergence of a distributed dual gradient algorithm for linearly constrained separable convex problems
In this paper we propose a distributed dual gradient algorithm for minimizing
linearly constrained separable convex problems and analyze its rate of
convergence. In particular, we prove that under the assumption of strong
convexity and Lipshitz continuity of the gradient of the primal objective
function we have a global error bound type property for the dual problem. Using
this error bound property we devise a fully distributed dual gradient scheme,
i.e. a gradient scheme based on a weighted step size, for which we derive
global linear rate of convergence for both dual and primal suboptimality and
for primal feasibility violation. Many real applications, e.g. distributed
model predictive control, network utility maximization or optimal power flow,
can be posed as linearly constrained separable convex problems for which dual
gradient type methods from literature have sublinear convergence rate. In the
present paper we prove for the first time that in fact we can achieve linear
convergence rate for such algorithms when they are used for solving these
applications. Numerical simulations are also provided to confirm our theory.Comment: 14 pages, 4 figures, submitted to Automatica Journal, February 2014.
arXiv admin note: substantial text overlap with arXiv:1401.4398. We revised
the paper, adding more simulations and checking for typo
Rate analysis of inexact dual first order methods: Application to distributed MPC for network systems
In this paper we propose and analyze two dual methods based on inexact
gradient information and averaging that generate approximate primal solutions
for smooth convex optimization problems. The complicating constraints are moved
into the cost using the Lagrange multipliers. The dual problem is solved by
inexact first order methods based on approximate gradients and we prove
sublinear rate of convergence for these methods. In particular, we provide, for
the first time, estimates on the primal feasibility violation and primal and
dual suboptimality of the generated approximate primal and dual solutions.
Moreover, we solve approximately the inner problems with a parallel coordinate
descent algorithm and we show that it has linear convergence rate. In our
analysis we rely on the Lipschitz property of the dual function and inexact
dual gradients. Further, we apply these methods to distributed model predictive
control for network systems. By tightening the complicating constraints we are
also able to ensure the primal feasibility of the approximate solutions
generated by the proposed algorithms. We obtain a distributed control strategy
that has the following features: state and input constraints are satisfied,
stability of the plant is guaranteed, whilst the number of iterations for the
suboptimal solution can be precisely determined.Comment: 26 pages, 2 figure
A procedure for an accurate estimation of the natural frequencies of structures
The paper presents a procedure to precisely estimate the natural frequencies of structures. It implies the acoustic excitation of the structure and the evaluation of the frequencies from the response signals, involving an advanced method developed by the authors. The study is performed on a cantilever beam. To demonstrate the efficiency of the contrived procedure, the values of the frequencies by applying this procedure are compared whit those obtained by standard frequency estimation made for the response to an impulsive excitation
Abordări microchirurgicale ale pterigionului recidivant
Introducere: Pterigionul recidivant este o afecțiune degenerativă a suprafeței oculare constând
în apariția unui strat triunghiular de țesut fibrovascular cu baza spre conjunctivă și vârful spre
cornee după operațiile de înlăturare a pterigionului.
Scopul: De a studia eficiența unei tehnici operatorii combinate în pterigionul recidivant stadiul
III.
Material și metode: Studiul a inclus 10 pacienți (5 bărbați și 5 femei) cu pterigion recidivant
stadiul III, cu vârstă cuprinsă între 20-71 ani, supuși intervenției microchirurgicale printr-o
metoda combinată. Metoda constă din formarea unui lambou liber conjunctival, dreptunghiular
5x3 mm, inferior, paralimbal. Ulterior lamboul este fixat conjunctival, nazal în zona corpului
pterigionului translocat în fornixul inferior. Este important ca lamboul conjunctival transplantat
să posede o orientare limbală. La finele intervenției, subconjunctival se introduce 0,1 ml-5% 5-
fluoruracil.
Rezultate: Reabilitarea postoperatorie a fost rapidă. Pe parcursul a 10-14 zile postoperator s-a
instalat o iritare conjunctivală determinată de suturile de fixare ale lamboului conjunctival
transplantat. Pe perioada menționată sunt indicate antibiotice, antiinflamatoare și lubrifiante. La
3 luni după intervenția microchirurgicală, la biomicroscopie semne ale recidivei pterigionului nu
s-au depistat.
Concluzie: Metoda combinată efectuată în cadrul pterigionului recidivant, stadiul III este
eficientă, sigură, determinată de lipsa recidivării pterigionului
Analysis of a low-voltage operating microgrid located in a residential area
The paper aims at providing the analysis of domestic energy generation and consumption within residential areas. The topic of this study is twofold: theoretical and experimental by addressing aspects related to the operation of a microgrid connected to the low-voltage distribution grid. In order to achieve the power quality analysis for various scenarios, an appropriate testing stand was developed by using the Chauvin Arnoux CA 8435 analyser. There is envisaged the modelling and design of a mixed microgrid characterized by two line sections established by three main energy consumption nodes. There have been integrated several connection points related to the distributed generation sources and to the photovoltaic power plants, respectively, and also several supply points for the household end-users. 13 operation scenarios have been developed and recorded by analysing the voltage variation within the microgrid. Furthermore, the paper envisages the stabilization impact of the microgrid voltage variation in the presence of distributed generation sources
CEACAM1: Expression and Role in Melanocyte Transformation
Metastases represent the main cause of death in melanoma patients. Despite the current optimized targeted therapy or immune checkpoint inhibitors the treatment of metastatic melanoma is unsatisfactory. Because of the poor prognosis of advanced melanoma there is an urgent need to identify new biomarkers to differentiate melanoma cells from normal melanocytes, to stratify patients according to their risk, and to identify subgroups of patients that require close follow-up or more aggressive therapy. Furthermore, melanoma progression has been associated with the dysregulation of cell adhesion molecules. We have reviewed the literature and have discussed the important role of the expression of the carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) in the development of melanoma. Thus, novel insights into CEACAM1 may lead to promising strategies in melanoma treatment, in monitoring melanoma patients, in assessing the response to immunotherapy, and in completing the standard immunohistochemical panel used in melanoma examination
Limited duration of vaccine poliovirus and other enterovirus excretion among human immunodeficiency virus infected children in Kenya
<p>Abstract</p> <p>Background</p> <p>Immunodeficient persons with persistent vaccine-related poliovirus infection may serve as a potential reservoir for reintroduction of polioviruses after wild poliovirus eradication, posing a risk of their further circulation in inadequately immunized populations.</p> <p>Methods</p> <p>To estimate the potential for vaccine-related poliovirus persistence among HIV-infected persons, we studied poliovirus excretion following vaccination among children at an orphanage in Kenya. For 12 months after national immunization days, we collected serial stool specimens from orphanage residents aged <5 years at enrollment and recorded their HIV status and demographic, clinical, immunological, and immunization data. To detect and characterize isolated polioviruses and non-polio enteroviruses (NPEV), we used viral culture, typing and intratypic differentiation of isolates by PCR, ELISA, and nucleic acid sequencing. Long-term persistence was defined as shedding for ≥ 6 months.</p> <p>Results</p> <p>Twenty-four children (15 HIV-infected, 9 HIV-uninfected) were enrolled, and 255 specimens (170 from HIV-infected, 85 from HIV-uninfected) were collected. All HIV-infected children had mildly or moderately symptomatic HIV-disease and moderate-to-severe immunosuppression. Fifteen participants shed vaccine-related polioviruses, and 22 shed NPEV at some point during the study period. Of 46 poliovirus-positive specimens, 31 were from HIV-infected, and 15 from HIV-uninfected children. No participant shed polioviruses for ≥ 6 months. Genomic sequencing of poliovirus isolates did not reveal any genetic evidence of long-term shedding. There was no long-term shedding of NPEV.</p> <p>Conclusion</p> <p>The results indicate that mildly to moderately symptomatic HIV-infected children retain the ability to clear enteroviruses, including vaccine-related poliovirus. Larger studies are needed to confirm and generalize these findings.</p
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