Technological University of Pereira
Pereira, Colombia

The Technological University of Pereira is a public, national, coeducational research university based in the city of Pereira, Risaralda, Colombia. The university is located in the southeast of the city.The university offers studies in Engineering ; Science and Technology ; Liberal arts ; Child pedagogy; and Sports science and recreation. Wikipedia.

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Garcia-Reyes G.,Technological University of Pereira
General Relativity and Gravitation | Year: 2017

By starting with a seed Newtonian potential–density pair we construct relativistic thick spherical shell models for a Majumdar–Papapetrou type conformastatic spacetime. As a simple example, we considerer a family of Plummer–Hernquist type relativistic spherical shells. As a second application, these structures are then used to model a system composite by a dust disk and a halo of matter. We study the equatorial circular motion of test particles around such configurations. Also the stability of the orbits is analyzed for radial perturbation using an extension of the Rayleigh criterion. The models considered satisfying all the energy conditions. © 2017, Springer Science+Business Media New York.

Garces A.,Technological University of Pereira
Electric Power Systems Research | Year: 2017

Low voltage direct current (LVDC) is a promising technology for future power distribution grids and smart grids applications. Power flow in these grids is a non-linear problem just as its counterpart AC. This paper demonstrates that, unlike in AC grids, convergence and uniqueness of the solution can be guaranteed in this type of grid under well defined practical considerations. The result is neither a linearization nor an approximation, but an analysis of the set of non-linear algebraic equations, which is valid for any LVDC grid regardless its size, topology or load condition. Computer simulation corroborates the theoretical analysis. © 2017 Elsevier B.V.

News Article | March 9, 2016

Researchers have found Colombia's first cases of birth defects linked to the Zika virus, Nature has learned — which are likely forerunners of a widely anticipated wave of Zika-related birth defects in the country. The discovery is perhaps no surprise: the virus arrived in Colombia last September, and the country is second only to Brazil in terms of the number of people infected with Zika. But Colombian researchers hope that plans put in place to closely monitor pregnant women can help to better establish the magnitude of the threat posed to fetuses by Zika. That is a crucial question that scientists have not so far been able to answer with the data from Brazil. Researchers have diagnosed one newborn with microcephaly — an abnormally small head — and two others with congenital brain abnormalities, says Alfonso Rodriguez-Morales, who chairs the Colombian Collaborative Network on Zika (RECOLZIKA), which made the diagnoses. All three tested positive for the presence of Zika virus. The researchers have submitted a report of their detections to a scientific journal. Rodriguez-Morales, an infectious-diseases epidemiologist at the Technological University of Pereira in western Colombia, says that he expects to see a rise in cases of Zika-linked birth defects starting in two or three months' time. The RECOLZIKA group — a network of researchers and public-health institutions across Colombia — are already investigating a handful of other suspected cases of microcephaly, which have a possible link to Zika. Brazil is the only country so far to report a large surge in newborns with microcephaly that coincides with outbreaks of Zika virus. By the time the alarm over a possible microcephaly link was raised there (in October 2015), Zika infections had already peaked in many parts of the country, because the virus first reached Brazil at the beginning of last year. In Colombia, by contrast, researchers detected the first Zika cases in September, and by December had set up national tracking programmes to monitor pregnant women for signs of infection, and to spot early signs of birth defects in fetuses. Since then, researchers have been waiting attentively to see whether their country might experience a similar rise in birth defects. The true size of Brazil's surge in microcephaly cases is unknown. The country's health ministry says that 5,909 suspected microcephaly cases have been registered since early November, but only 1,687 of them have been investigated so far. Of those, 1,046 have been discarded as false positives, and 641 have been confirmed. (A link with the Zika virus has been confirmed by molecular-lab tests in 82 cases.) Given that Brazil reported only 147 cases of microcephaly in 2014, the reported increase in cases since November suggests a marked rise in the number of babies born with the condition. But the 2014 figure is a “huge underestimate”, says Lavinia Schüler-Faccini, a geneticist who specialises in birth defects at the Federal University of Rio Grande do Sul, Brazil, and president of the Brazilian Society of Genetic Medicine. She says that according to the frequency of microcephaly typically observed in regions around the world, one would expect to see 300–600 cases of severe microcephaly in any given year in Brazil, and around 1,500 less-severe ones. The search for cases of microcephaly in Brazil since October is probably turning up many mild cases that previously went unnoticed — so that the reported surge looks higher than it really is. Still, Schüler-Faccini and other clinicians say there is a real problem. They have observed first-hand a marked increase in the number of unusually severe cases of microcephaly, they say. To be prepared to better interpret any imminent peak in birth defects in Colombia, RECOLZIKA plans to look at historical cases to establish a baseline for the annual numbers of birth defects in different regions. It is also setting up a study to analyse patterns in the distribution of head-circumference measurements recorded in obstetrics units regionally throughout the country, to get a better idea of the local range of normal values. It has also not been possible so far from Brazilian data to quantify the extent to which Zika virus is linked to the rise in microcephaly. The latest data from Brazil's ministry of health show that increased cases of microcephaly and/or congenital malformations of the central nervous system are still concentrated in the northeast — raising questions as to whether other factors, perhaps specific to this region, might also be in play. Clinical evidence leaves little doubt that a link between Zika and microcephaly exists: the virus has been detected in amniotic fluid, in the cerebrospinal fluid of affected babies and in the brains of stillborn fetuses and those aborted after the detection of severe malformations during pregnancy. But there are also many other possible causes of microcephaly, including a group of infections that are collectively called STORCH (syphilis, toxoplasmosis, other infections, rubella, cytomegalovirus infection and herpes simplex), which are known to cause birth defects. Exposure to toxic chemicals and the consumption of alcohol during pregnancy can also cause the condition. “There is a clear need for a full assessment of other detailed causes of microcephaly, such as STORCH, and even non-infectious causes,” says Rodriguez-Morales. Brazil’s health ministry has stated that it is carrying out tests for such causes, but it has not made public how many of the confirmed microcephaly cases are attributable to these. A key question in assessing the scale of the threat that Zika may pose to fetuses is how many pregnant women infected with Zika — in particular during the first trimester, when the fetus is most vulnerable — nonetheless give birth to healthy babies. RECOLZIKA researchers hope to help to answer this through their monitoring programme. The risk posed by Zika may well be lower than that of other diseases that are known to cause microcephaly such as toxoplasmosis and rubella, says Rodriguez-Morales. That is a preliminary estimate, he says, based on back-of-the-envelope calculations of the reported numbers of confirmed cases of microcephaly and congenital disorders, compared to the number of pregnant women in regions experiencing Zika epidemics. But even if its risk does turn out to be low, Zika could still lead to many cases because a large number of pregnant women in the Americas are likely to become infected with the virus. The biggest risk to pregnant women is right now, rather than in the long term. The epidemic is sweeping so quickly through the Americas that much of the population, including young women, will become naturally vaccinated by their exposure to the virus. As population immunity increases, the Zika epidemic is likely to fade quickly, and it will become endemic with only occasional flare ups. In a modelling study posted to the preprint server bioRxiv1 on 29 February, US researchers noted that the risk of prenatal Zika virus exposure “should decrease dramatically following the initial wave of disease, reaching almost undetectable levels”.

Alvarez M.A.,Technological University of Pereira | Rosasco L.,Italian Institute of Technology | Lawrence N.D.,University of Sheffield
Foundations and Trends in Machine Learning | Year: 2011

Kernel methods are among the most popular techniques in machine learning. From a regularization perspective they play a central role in regularization theory as they provide a natural choice for the hypotheses space and the regularization functional through the notion of reproducing kernel Hilbert spaces. From a probabilistic perspective they are the key in the context of Gaussian processes, where the kernel function is known as the covariance function. Traditionally, kernel methods have been used in supervised learning problems with scalar outputs and indeed there has been a considerable amount of work devoted to designing and learning kernels. More recently there has been an increasing interest in methods that deal with multiple outputs, motivated partially by frameworks like multitask learning. In this monograph, we review different methods to design or learn valid kernel functions for multiple outputs, paying particular attention to the connection between probabilistic and functional methods. © 2012 M. A. Álvarez, L. Rosasco and N. D. Lawrence.

Garces A.,Norwegian University of Science and Technology | Garces A.,Technological University of Pereira | Molinas M.,Norwegian University of Science and Technology
IEEE Transactions on Industrial Electronics | Year: 2012

Reduced matrix converter (RMC) is a convenient topology for offshore wind farm due to its potential to reduce the size and weight of the converter, to improve the reliability by removing the electrolytic capacitor, and to increase the efficiency inherent to less stages of conversion. Moreover, it is a very flexible topology which permits different types of operation with a simpler modulation compared with conventional three-phase matrix converter. This paper investigates different modulation strategies applied to RMC for offshore wind farms, focused on efficiency improvement of the entire convention system. Simulation results using a detailed loss model for high-power level are presented. Four cases are investigated according to the modulation strategies (space vector modulation and carrier-based modulation) and the operation principle (current source converter or voltage source converter). Losses in the clamp circuit are also calculated. Different wind velocities are considered in the simulations. Results show that current source operation with space vector modulation presents minimum losses at nominal wind velocity. This operation is suitable for series connection of offshore wind farms which has been reported as the most efficient alternative from the grid losses point of view. © 2011 IEEE.

Garces A.,Technological University of Pereira
IEEE Transactions on Power Systems | Year: 2016

This letter proposes a linear load flow for three-phase power distribution systems. Balanced and unbalanced operation are considered as well as the ZIP models of the loads. The methodology does not require any assumption related to the R/X ratio. Despite its simplicity, it is very accurate compared to the conventional back-forward sweep algorithm. © 1969-2012 IEEE.

Rodriguez-Morales A.J.,Technological University of Pereira
Recent patents on anti-infective drug discovery | Year: 2014

BACKGROUND: Despite efforts in prevention and control of dengue, it is still a public health problem in the region. There are estimations of 13 million people affected in the Americas, therefore, it is of outmost importance to research it. An assessment on the Latin- American contributions on dengue was done.METHODS: Bibliometric study at SCI (1980- 2013), MEDLINE/GOPUBMED (1802-2013), Scopus (1959-2013), SCIELO (2004-2013), LILACS (1980- 2013). Different study types, characterized by years, city/country of origin, journals and more productive authors, by country, cites and H index have been conducted.RESULTS: At SCI, 2598 articles were retrieved (21% of the total). Brazil was found to be the highest contributor (31.2%), then Puerto Rico (12.9%) and Mexico (10.7%). At Scopus, there are 2646 articles (16.7% of the total), 31.2% Brazil, 11.1% Mexico, 9.3% Cuba; the region received 41881 citations, 25.4% from Brazil (H index=45), 14.4% Cuba (H index=35) and 12.88% Puerto Rico (H index=38); 9.1% in Brazil were from Fundação Oswaldo Cruz; 1.6% of Mexico corresponded to Instituto Nacional de Salud Publica, 4.9% of Cuba are from Instituto de Medicina Tropical Pedro Kouri. At Medline, there are 2799 records (33.9% from Brazil). At SciELO there are 825 records (46.6% Brazil). At LILACS, there are 1178 records (46.8% Brazil).CONCLUSIONS: Brazil is the best producer in the region. In Puerto Rico and Brazil, there observed the epidemiologic burden of the disease. Scientific production in bibliographical data bases, particularly regional, is low, as compared to the high impact of the disease of in urban zones of the region.

Rodriguez-Morales A.J.,Technological University of Pereira
Recent patents on anti-infective drug discovery | Year: 2014

RESULTS: At SCI, 2,806 articles were retrieved (5.13% of the total). Brazil was the highest producer (31.41%), followed by Colombia (14.3%) and Mexico (9.5%). The region received 39,894 citations, 32.2% from Brazil (H index=51), 12.75% Mexico (H index=38), 11.2% Colombia (H index=33). At Scopus, there are 4,150 articles (4.9% of the total), 33.0% Brazil, 11.3% Colombia and 8.8% Mexico; 17% in Brazil were from Universidad de São Paulo; 23.6% of Colombia from Universidad de Antioquia; 15.4% of Mexico from Instituto Nacional de Salud Pública. At Medline there were 4,278 records (36.8% Brazil). At SciELO there are 792 records (45.3% Brazil). At LILACS there were 1744 records (34.3% Brazil).CONCLUSIONS: Brazil has the highest output of the region, as Venezuela the scientific production in Malaria was related with the burden of disease. This was not the case for Colombia. Scientific production at bibliographical databases, particularly regionals, is low, compared to the high incidence of this disease that requires more research and control.BACKGROUND: Malaria is a parasitic disease of high global impact in public health, including Latin America. There should be more researched, particularly in this region. A bibliometric assessment of the Latin American contributions about malaria was done.METHODS: Bibliometric study at SCI (1980-2013), MEDLINE/ GOPUBMED (1802-2013), Scopus (1959-2013), SCIELO (2004-2013), LILACS (1980-2013). The studies were characterized by study type, year of publication, city/country of origin, journals and more productive authors, citations and H index.

Giraldo E.,Technological University of Pereira | Garces A.,Technological University of Pereira
IEEE Transactions on Power Systems | Year: 2014

This paper proposes a new adaptive control strategy for a wind energy conversion system based on a permanent magnet synchronous generator and a pulse-width modulated current source converter. Most of the studies on wind farms are based on double fed induction technology. Nevertheless, the proposed conversion system is a good alternative due to its high efficiency and reliability. Electrolytic capacitors are not required in this type of converter and the voltage in the DC-link as well as the generated reactive power can be dynamically modified according to the wind velocity, being even negative if required. However, it is challenging from the control and stability standpoint. Capacitive filters placed on the AC side, which are required for safe commutation, can create resonances with the power grid. Reactive power is generated according to the capacity of the converter, the wind velocity and the load profile. The adaptive control strategy uses an adaptive PI which is self-tuned based on a linear approximation of the power system calculated at each sample time. A model reference is also proposed in order to reduce the post-fault voltages. Simulation results demonstrate the advantages of the proposed control. © 2014 IEEE.

De Los Rios Trejos and Technological University of Pereira | Date: 2012-10-24

The present invention is related with a process for the production of a great variety of building materials from the paper waste, that consumes a high quantity of this industrial waste, which implies a decrease in the deposit of these polluting wastes and therefore, the decrease of the adverse effects that such wastes cause on the environment.

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