Carlos Chaves - Academia.edu (original) (raw)

Papers by Carlos Chaves

Proceedings of the 8th International Symposium on Solid Mechanics

Anales de la Facultad de Medicina

Introducción. El ingreso del linaje II del DENV-2 americano/asiático en la región Loreto de la Am... more Introducción. El ingreso del linaje II del DENV-2 americano/asiático en la región Loreto de la Amazonia Peruana, coincidió con un incremento súbito de los casos de dengue con necesidad de hospitalización. Sin embargo, las estadísticas oficiales reportaron pocos casos graves. Se postula, que existió una subnotificación de los casos graves en los reportes oficiales del Ministerio de Salud. Objetivos. Conocer la frecuencia de pacientes con signos de gravedad entre los pacientes hospitalizados por dengue probable durante el brote del 2011 en el Hospital Iquitos, Perú. Métodos. Se realizó un estudio longitudinal, aplicando una lista de chequeo diaria, sobre la presencia de signos de gravedad durante la estancia hospitalaria, a un grupo de pacientes hospitalizados en la unidad de dengue del Hospital Iquitos. Resultados. De 178 pacientes evaluados 66 (37%, IC: 29,9 – 44,6%) presentaron algún signo de gravedad, la mayor parte por shock (75,7%). Este resultado contrasta con el número de paci...

Operational Research

We consider the multi-server, single-channel queue, i.e., a G/G/k queue with k identical servers ... more We consider the multi-server, single-channel queue, i.e., a G/G/k queue with k identical servers in parallel, under the first-come-first-served discipline in which the inter-arrival process is non-Poisson, the service time has any given distribution, and traffic is of medium intensity. Such queues are common in factories, airports, and hospitals, where the inter-arrival times and service times are typically not exponentially distributed, but rather have double-tapering distributions whose probability density functions taper on both sides, e.g., gamma, triangular etc. For these conditions, a new closed-form approximation based on only the mean and variance of the two inputs, the inter-arrival and service times, is presented. Determining distributions of inputs typically requires additional human effort in terms of histogram-fitting and running a goodness-of-fit test, which is avoided here. The new approximation is tested on a variety of scenarios and its performance is benchmarked against simulation. Further, the new approximation is also implemented on a ventilator case study from the recent COVID-19 pandemic to demonstrate its utility in optimizing server capacity. The approximation provides errors typically in the range 1-15% and 31% in the worst case. In systems where data change rapidly and decisions must be made quickly, this approximation will be particularly useful.

This works records all the abstracts presented at the 3rd Brazilian Seismology Symposium. It also... more This works records all the abstracts presented at the 3rd Brazilian Seismology Symposium. It also documents the number of participants, pre-symposium course and mini-courses. It also records the number of participants, webpages associated and serves as a citation to all the work developed during the conference.

Volume 10: Fluids Engineering, 2021

The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a s... more The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a small South-American country, was not an exception. This work results from the urgent need to reopen universities, schools, and other academic institutions to resume teaching activities in light of restrictive access to online learning in Paraguay. In order to contain the spread of this virus, school activities such as course lectures were placed on hold indefinitely. Inappropriate airflow in an enclosed space is one of the main factors in the spread of this virus. When combined with personal protective equipment, proper air ventilation and air replacement can significantly reduce this airborne virus’s spread. Potential sources of contaminant accumulation are stagnant locations of air in a closed volume. It is, therefore, essential to first identify these hot spots. Utilizing computational tools, such as CFD, an airflow analysis can be conducted to see any potential stagnant point. In the...

| This a preprint and has not been peer reviewed. Data may be preliminary.

Revista Uniabeu, 2017

Este trabalho apresenta de maneira didatica o Principio de Saint-Venant utilizando o Metodo dos E... more Este trabalho apresenta de maneira didatica o Principio de Saint-Venant utilizando o Metodo dos Elementos Finitos, tornando o seu entendimento bastante simples e visual atraves dos resultados qualitativos e quantitativos apresentados pelo software Abaqus CAE. O principio de Saint-Venant tem grande importância na formulacao de problemas de elasticidade, pois em muitos casos, permite atraves de modelos matematicos simplificados, a obtencao de solucoes globais de interesse pratico. Esse principio estabelece que um sistema de forcas externas em equilibrio, agindo sobre uma proporcao pequena da peca em relacao ao todo, produz tensoes elevadas apenas nas imediacoes da regiao de aplicacao dessas forcas, sejam elas de acao ou reacao.

En el actual escenario internacional, China se configura como una potencia mundial en ascenso, co... more En el actual escenario internacional, China se configura como una potencia mundial en ascenso, con tendencia a liderar los procesos de globalizacion politica y economica en el siglo XXI, lo cual implica nuevos desafios para la insercion internacional de America Latina en general, y de Colombia en particular con la nueva potencia. En el marco de cuatro decadas de relaciones oficiales entre Colombia y China, resulta de suma importancia efectuar un diagnostico de los logros, falencias y retos presentes en las relaciones diplomaticas bilaterales, con miras a identificar los obstaculos y las posibilidades que tiene Colombia para lograr el estatus de socio estrategico de China en el contexto de las relaciones sino-latinoamericanas y de las transformaciones y apuestas de la politica exterior colombiana. A partir de un enfoque cualitativo de tipo descriptivo y analitico se propone un analisis critico de las relaciones colombo-chinas con enfasis en la dimension politica, sustentado a partir ...

The multidisciplinary teaching team in the Faculty of Pharmacy, from his creation 8 years ago, pa... more The multidisciplinary teaching team in the Faculty of Pharmacy, from his creation 8 years ago, participates in all the actions focused in the support and formation of the beginner professor and in the improvement of the teaching of the University of Granada. Nowadays, the teaching team is constituted by 7 experienced professors (with 20 years of experience in teaching, coordinating grade level curricula, tutorial action plans, teaching innovation projects and implementation and monitoring of quality assurance systems in undergraduate degrees) and 14 beginner professors of different departments with different professional categories teaching in three degrees of the faculty: “Pharmacy”, “Human Nutrition and Dietetic”, “Food Science and Technology”. In every academic course, new beginner professors are incorporated to the team. The methodology followed in the present work has focused on: Detection and analysis of the formative needs of the new professors, design and coordination of the...

EDULEARN18 Proceedings, 2018

Engineering Research: technical reports, 2017

The "Engineering Research" is a publication with purpose of technical and academic knowledge diss... more The "Engineering Research" is a publication with purpose of technical and academic knowledge dissemination.

Brazilian Review of Finance, 2019

We examine the impact of expected inflation on stock returns. We use inflation forecasts from the... more We examine the impact of expected inflation on stock returns. We use inflation forecasts from the Focus survey and real returns of Ibovespa (the index of B3, the Brazilian stock exchange). In our main specification, an increase of 1 percentage point in expected inflation for the next 12 months is associated with a decline of 0.57 percentage points in stock returns. Stock returns react negatively to the 5-year CDS volatility and the VIX index. A simulated portfolio with a strategy based on changes in inflation expectations from 2003 to 2016 has cumulated real returns of 135 percent while cumulated real Ibovespa returns are 48 percent. The strategy implies higher cumulated real returns compared with Ibovespa in 69 percent of the period.

Acta Scientiae Veterinariae, 2018

Background: Subclinical endometritis (SE) have a negative impact on fertility due to an absence o... more Background: Subclinical endometritis (SE) have a negative impact on fertility due to an absence of clinical signs which difficult its diagnosis and treatment. The prevalence and impact of the disease on the reproductive status of dairy herds is not known in the region, the objective of the present study was to determine the prevalence of the disease and its effect on the reproductive efficiency in cows of the dairy area from Putumayo State, Colombia.Materials, Methods & Results: Cross-sectional study was made of 166 dairy cows from 30 days postpartum in the municipalities: Santiago, Sibundoy, Colon, and San Francisco. Reproductive evaluation and endometrial cytology were made to establish the SE prevalence determining subsequently the number of open days. Cow whit more than 120 days in milk (DIM) and without confirmed pregnancy was defined as “not reproductive efficiency”. Association between SE and reproductive efficiency was established through Odds Ratio from contingency tables. ...

Anales de la Facultad de Medicina, 2014

En el Instituto Nacional de Enfermedades Neoplásicas se realizó un estudio prospectivo con el fin... more En el Instituto Nacional de Enfermedades Neoplásicas se realizó un estudio prospectivo con el fin de brindar un tratamiento multidisciplinario a pacientes con cáncer de mama en estadio clínico III, utilizando quimioterapia (QTX) primaria o neoadyuvante, y luego sometiendo a las pacientes, aleatoriamente, a una terapia loco-regional, pudiendo ser ésta cirugía (mastectomia radical) o radioterapia, con el posterior uso de QTX coadyuvante en ambos grupos. Éste es un trabajo piloto de investigación clínica, aleatorizado, prospectivo, de intervención, descriptivo y analítico. La respuesta clínica a la QTX primaria fue positiva en el 80,23% de casos, siendo ésta completa en el 18,60%, parcial en el 61,63% y negativa en el 19,77% de casos. Anatomopatológicamente, no se encontró neoplasia residual en el 8,33% de los casos quirúrgicos. Se demostró que la QTX primaria a altas dosis, con sólo 2 drogas (ciclofosfamida y 5-fluoruracilo), usada en nuestro medio por su bajo costo, ha dado resultado...

EDULEARN16 Proceedings, 2016

Geochemistry, Geophysics, Geosystems, 2016

Province are high. • High density precludes a depleted cratonic lithosphere and indicates referti... more Province are high. • High density precludes a depleted cratonic lithosphere and indicates refertilized lithospheric mantle. • Basalt magmatism suggests refertilized mantle with asthenospheric components from mantle wedge.

Especulo Revista De Estudios Literarios, 2007

Cultura Cientifica, Nov 10, 2011

This investigation is an approach to the operation and the current state of the micro, small and ... more This investigation is an approach to the operation and the current state of the micro, small and medium enterprises Pymes- of the metal mechanic sector in the industrial corridor of Boyaca. This study design the model of the financial structure and describe the economic situation of this kind of enterprises for the knowledge of its reality, articulate the basic elements of the financial structure appropriateto the model, bearing in mind the most important financing variables: wealth net profit, bank interest, third parties interest, suppliers interest and development credits interest. Additionally, the validation of the model is shown starting from the construction of different scenarios: pessimist, optimistic and more probable, estimating the current financial market rates to calculate the cost pondered average of capital. This model is veryuseful for this sector's business man because it sapplication would allow to increase the productivity of its companies as a competitiveness viable strategyin view of the markets liberation phenomenon present at the moment in Colombia and the world.

e-xacta, 2016

Grades são equipamentos de grande importância porque são responsáveis pela proteção das turbinas ... more Grades são equipamentos de grande importância porque são responsáveis pela proteção das turbinas de usinas hidroelétricas contra impacto de corpos flutuantes. O objetivo do presente trabalho é analisar grades submetidas à ação de fluxo de água. Ou seja, analisar as respostas da estrutura e o comportamento do escoamento da água utilizando os cálculos de dinâmica de estruturas acopladas às técnicas de dinâmica de fluidos computacional (CFD), para um regime turbulento, mediante o uso do software comercial CFX versão 14. Tais análises são elaboradas mediante o processo de interação fluido-estrutura. Um modelo estrutural simplificado das barras verticais das grades é elaborado a partir de dados de projeto conhecidos. A partir desse modelo definese um volume de controle que representa o escoamento do fluido. Devido ao número de Reynolds calculado, utiliza-se o modelo de turbulência para obtenção dos resultados tais como tensões e deslocamentos nas barras verticais; e perfil de velocidades do escoamento. PALAVRAS-CHAVE: Grade de proteção de turbina. Interação fluido-estrutura. Escoamento turbulento.