Pontifical Catholic University of Rio de Janeiro

Rio de Janeiro, Brazil

The Pontifícia Universidade Católica do Rio de Janeiro is a major private and non-profit Catholic university, located in Rio de Janeiro, the second largest city of Brazil. It is maintained by the Catholic Archdiocese of Rio de Janeiro and the Society of Jesus. Wikipedia.

Time filter
Source Type

Lima R.,Pontifical Catholic University of Rio de Janeiro | Sampaio R.,Pontifical Catholic University of Rio de Janeiro
Mechanical Systems and Signal Processing | Year: 2017

In this paper the dynamics of a dry-friction oscillator driven by a stochastic base motion has been analyzed. The system consists of a simple oscillator (mass-spring) moving on a base with a rough surface. This roughness induces a dry-frictional force between the mass and the base which is modeled as a Coulomb friction. It is considered that the base has an imposed stochastic bang-bang motion which excites the system in a stochastic way. The non-smooth behavior of the dry-frictional force associated with the non-smooth stochastic base motion induces in the system stochastic stick-slip oscillations. A statistical model is constructed for the stick-slip dynamics of the system. The objective is to characterize, from a statistical view point, the response of the dry-friction oscillator composed by a sequence of stick and slip-modes. Defined a time interval for analysis, some of the variables which appear in this statistical model are the number of time intervals in which stick and slip occur, the instants at which they begin and their duration. These variables are modeled as stochastic objects. Statistics of them, as mean, variance and entropy, and histograms, are computed by the integration of the dynamics equations of the system using independent samples of the base movement generated with the Monte Carlo method. © 2016

Molinaro M.,Pontifical Catholic University of Rio de Janeiro
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2017

We consider the problem of online load balancing under p-norms: sequential jobs need to be assigned to one of the machines and the goal is to minimize the p-norm of the machine loads. This generalizes the classical problem of scheduling for makespan minimization (case 1) and has been thoroughly studied. However, despite the recent push for beyond worst-case analyses, no such results are known for this problem. In this paper we provide algorithms with simultaneous guarantees for the worst-case model as well as for the random-order (i.e. secretary) model, where an arbitrary set of jobs comes in random order. First, we show that the greedy algorithm (with restart), known to have optimal O(p) worst-case guarantee, also has a (typically) improved random-order guarantee. However, the behavior of this algorithm in the random-order model degrades with p. We then propose algorithm SIMULTANEOUSLB that has simultaneously optimal guarantees (within constants) in both worst-case and randomorder models. In particular, the random-order guarantee of SIMULTANEOUSLB improves as p increases. One of the main components is a new algorithm with improved regret for Online Linear Optimization (OLO) over the non-negative vectors in the q ball. Interestingly, this OLO algorithm is also used to prove a purely probabilistic inequality that controls the correlations arising in the random-order model, a common source of difficulty for the analysis. Another important component used in both SIMULTANEOUSLB and our OLO algorithm is a smoothing of the p-norm that may be of independent interest. This smoothness property allows us to see algorithm SIMULTANEOUSLB as essentially a greedy one in the worst-case model and as a primal-dual one in the random-order model, which is instrumental for its simultaneous guarantees. Copyright © by SIAM.

Dias F.L.,Pontifical Catholic University of Rio de Janeiro
Current Opinion in Oncology | Year: 2017

PURPOSE OF REVIEW: The rising incidence of oropharyngeal squamous cell carcinoma (OPSCC), in large part as a result of the human papillomavirus (HPV), has driven a movement for the change in the management strategies. Renewed interest in minimally invasive approaches of endoscopic head and neck surgery led to introduction of transoral surgery, including transoral robotic surgery (TORS). RECENT FINDINGS: Several recent studies, based on large multi-institutional studies and systematic reviews of the literature, have shown excellent oncologic and functional outcomes with TORS for OPSCC. Also, a growing amount of clinical evidence supports the use of TORS in the management of carcinoma of unknown primary site and in selected patients with recurrent OPSCC with acceptable oncologic and better functional outcomes in comparison with traditional surgical approaches. Comparative studies with other therapeutic modalities (conventional surgical and nonsurgical) showed that TORS can be used to treat OPSCC, reducing morbidity and treatment costs, while providing equivalent oncologic results. SUMMARY: Large and robust data available in the literature supports the role of TORS within the multidisciplinary treatment paradigm for the management of OPSCC. Information from ongoing randomized clinical trials comparing TORS with and without dose-reduced radiotherapy or with and without intensified adjuvant treatment for high-risk OPSCC patients is necessary to determine the role of de-escalation of therapy in the era of HPV and OPSCC. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.

Vidal T.,Pontifical Catholic University of Rio de Janeiro
Operations Research | Year: 2017

This article explores a structural neighborhood decomposition for arc routing problems, in which the decisions about traversal orientations during services are made optimally as part of neighbor evaluation procedures. Using memory structures, bidirectional dynamic programming, and lower bounds, we show that a large neighborhood involving classical moves on the sequences of services along with optimal orientation decisions can be searched in amortized O(1) time per move evaluation instead of O(n) as in previous works. Because of its generality and now-reduced complexity, this approach can be efficiently applied to several variants of arc routing problems, extended into large neighborhoods such as ejection chains, and integrated into two classical metaheuristics. Our computational experiments lead to solutions of high quality on the main benchmark sets for thecapacitated arc routing problem (CARP), the mixed capacitated general routing problem (MCGRP), the periodic CARP, the multidepot CARP, and the min-max k-vehicles windy rural postman problem, with a total of 1,528 instances. We also report sensitivity analyses for new MCGRP instances with turn penalties, which are uncommonly challenging yet critical for many practical applications. © 2017 INFORMS.

Miranda O.G.,CINVESTAV | Nunokawa H.,Pontifical Catholic University of Rio de Janeiro
New Journal of Physics | Year: 2015

Neutrino oscillations have become well-known phenomena; the measurements of neutrino mixing angles and mass squared differences are continuously improving. Future oscillation experiments will eventually determine the remaining unknown neutrino parameters, namely, the mass ordering, normal or inverted, and the CP-violating phase. On the other hand, the absolute mass scale of neutrinos could be probed by cosmological observations, single beta decay as well as by neutrinoless double beta decay experiments. Furthermore, the last one may shed light on the nature of neutrinos, Dirac or Majorana, by measuring the effective Majorana mass of neutrinos. However, the neutrino mass generation mechanism remains unknown. A well-motivated phenomenological approach to search for new physics, in the neutrino sector, is that of non-standard interactions. In this short review, the current constraints in this picture, as well as the perspectives from future experiments, are discussed. © 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

De Lamare R.C.,Pontifical Catholic University of Rio de Janeiro | De Lamare R.C.,University of York
IEEE Transactions on Wireless Communications | Year: 2013

In this work, decision feedback (DF) detection algorithms based on multiple processing branches for multi-input multi-output (MIMO) spatial multiplexing systems are proposed. The proposed detector employs multiple cancellation branches with receive filters that are obtained from a common matrix inverse and achieves a performance close to the maximum likelihood detector (MLD). Constrained minimum mean-squared error (MMSE) receive filters designed with constraints on the shape and magnitude of the feedback filters for the multi-branch MMSE DF (MB-MMSE-DF) receivers are presented. An adaptive implementation of the proposed MB-MMSE-DF detector is developed along with a recursive least squares-type algorithm for estimating the parameters of the receive filters when the channel is time-varying. A soft-output version of the MB-MMSE-DF detector is also proposed as a component of an iterative detection and decoding receiver structure. A computational complexity analysis shows that the MB-MMSE-DF detector does not require a significant additional complexity over the conventional MMSE-DF detector, whereas a diversity analysis discusses the diversity order achieved by the MB-MMSE-DF detector. Simulation results show that the MB-MMSE-DF detector achieves a performance superior to existing suboptimal detectors and close to the MLD, while requiring significantly lower complexity. © 2013 IEEE.

Godoy-Matos A.F.,Pontifical Catholic University of Rio de Janeiro
Diabetology and Metabolic Syndrome | Year: 2014

The opposite effects of insulin and glucagon in fuel homeostasis, the paracrine/endocrine inhibitory effects of insulin on glucagon secretion and the hyperglucagonemia in the pathogenesis of type 2 diabetes (T2D) have long been recognized. Inappropriately increased alpha-cell function importantly contributes to hyperglycemia and reflects the loss of tonic restraint normally exerted by high local concentrations of insulin on alpha-cells, possibly as a result of beta-cell failure and alpha-cell insulin resistance, but additional mechanisms, such as the participation of incretin hormones in this response, have also been suggested. Three classes of drugs already available for clinical use address the abnormalities of glucagon secretion in T2D, namely, the GLP-1 receptor agonists (GLP-1RA), the inhibitors of dipeptidyl peptidase-4 (DPP-4i) and the amylin agonist pramlintide; it has been proposed that the glucagonostatic and insulinotropic effects of GLP-1RA equally contribute to their hypoglycemic efficacy. In this review, the control of glucagon secretion and its participation in T2D pathogenesis are summarized. © 2014 Godoy-Matos; licensee BioMed Central Ltd.

Costa E.,Pontifical Catholic University of Rio de Janeiro
IEEE Transactions on Intelligent Transportation Systems | Year: 2011

A simulation model is proposed to represent the channel of the Global Positioning System (GPS). Initially, a digital elevation model, building databases, and a vegetation model are processed to generate azimuth-elevation maps of path states (clear, shadowed, and blocked) for a large number of observers. At each simulation step, satellite positions are updated, and azimuths and elevations of paths from observers to satellites are calculated. Signal strengths and range errors are assigned to paths with the aid of random number generators for each path state. This information is processed to determine the statistics of the channel. It will be shown that model predictions are able to display good agreement with the results from an experimental campaign carried out for validation purposes. The simulation model will then be applied to a large number of observers deployed along two routes in densely urbanized areas in the city of Rio de Janeiro, Brazil (22.8° S, 43.3° W), with buildings displaying different height distributions to quantitatively show how the most probable number of available satellites, the probability that four or more satellites are simultaneously available (that is, that positions can be fixed), and the position errors change with the average building height and for vehicles in static and kinematic modes. In combination with the comparison between measurement and prediction results, this indicates that the simulation model is an efficient and flexible tool for studying and planning satellite-based location and navigation applications with accuracy and sensitivity, which will be used in future developments of mitigation techniques of multipath effects, leading to improved performance of intelligent transportation systems. © 2006 IEEE.

De Souza Mendes P.R.,Pontifical Catholic University of Rio de Janeiro
Soft Matter | Year: 2011

A constitutive model for structured fluids is presented. Its predictive capability includes thixotropy, viscoelasticity and yielding behavior. It is composed by two differential equations, one for the stress and the other for the structure parameter - a scalar quantity that represents the structuring level of the fluid. The equation for stress is obtained in accordance with a simple mechanical analog composed by a structuring-level-dependent Maxwell element in parallel with a Newtonian element, leading to an equation of the same form as the Jeffreys (or Oldroyd-B) equation. The relaxation and retardation times that arise are functions of the structure parameter. The ideas found in de Souza Mendes, J. Non-Newtonian Fluid Mech., 2009, 164, 66 are employed for the structure parameter equation as well as for the dependencies on the structure parameter of the structural viscosity and structural shear modulus. The model is employed in constant-rate, constant-stress, and oscillatory shear flows, and its predictive capability is shown to be excellent for all cases. © 2011 The Royal Society of Chemistry.

News Article | October 28, 2016
Site: www.reuters.com

RIO DE JANEIRO (Reuters) - Brazilian health officials say they do not expect a second wave of widespread Zika infections similar to that of a year ago, despite warming temperatures causing a rebound in reproduction of the mosquito responsible for transmitting the virus.

Loading Pontifical Catholic University of Rio de Janeiro collaborators
Loading Pontifical Catholic University of Rio de Janeiro collaborators