El cambio climático en la América ecuatorial

El cambio climático afectará diferentes regiones del planeta, como América ecuatorial, las que tienen estrecha relación con las condiciones ambientales dentro de las cuales el clima es factor importante. En este artículo, partiendo del Sexto Informe de Evaluación del IPCC, se visibilizan las tendencias de largo plazo en la temperatura media del aire y de la precipitación y las posibles condiciones futuras en estas variables y en el nivel medio del mar para América ecuatorial. Se reflexiona acerca de las acciones en la que debería enfatizar la región: presionar en la política global por metas más ambiciosas y efectivas para la reducción drástica en el corto plazo de emisiones de gases de efecto invernadero, promover la innovación tecnológica para la mitigación y adaptación, fortalecer la red de observación del clima y optimizar los sistemas de alerta temprana con mayor apoyo del pronóstico del tiempo y predicción climática

Mechanical behavior of low density concrete mixtures with thermally expanded clay from the metropolitan area of Cúcuta: Comportamiento mecánico de mezclas de concreto de baja densidad con arcilla expandida térmicamente del área metropolitana de

In order to develop construction materials with greater efficiency and performance than conventional materials, mixtures of lightweight concrete (LWC) made from thermally expanded clay (TEC) have been generated. In this article we study the mechanical properties (equilibrium density, compressive strength) of the LWC mixtures produced with raw material from the metropolitan area of Cúcuta, contrasting their characteristics with conventional concrete (CC) mixtures. For this, the lightweight aggregates were developed by calcining clay pellets in a rotary kiln at a pilot plant scale at a temperature of 1050 ° C, generating an expansion of 1.60 times of its initial size. Following the methodology ACI 211.2-98 two concrete mixtures were designed: the first, with fine and coarse aggregate of TEC; and the second, with coarse aggregate of TEC and fine aggregate of sand. It was determined that the LWC mixture with the highest efficiency is the one that uses fine and coarse aggregate of TEC, since the density of the LWC decreased by 25% with respect to the density of the CC, maintaining the resistance to compression after 28 days Under the same conditions. In conclusion, LWC mixtures made from TEC with raw materials from the metropolitan area of Cúcuta have a lower equilibrium density and compressive strength similar to that of CC.In order to develop construction materials with greater efficiency and performance than conventional materials, mixtures of lightweight concrete (LWC) made from thermally expanded clay (TEC) have been generated. In this article we study the mechanical properties (equilibrium density, compressive strength) of the LWC mixtures produced with raw material from the metropolitan area of Cúcuta, contrasting their characteristics with conventional concrete (CC) mixtures. For this, the lightweight aggregates were developed by calcining clay pellets in a rotary kiln at a pilot plant scale at a temperature of 1050 ° C, generating an expansion of 1.60 times of its initial size. Following the methodology ACI 211.2-98 two concrete mixtures were designed: the first, with fine and coarse aggregate of TEC; and the second, with coarse aggregate of TEC and fine aggregate of sand. It was determined that the LWC mixture with the highest efficiency is the one that uses fine and coarse aggregate of TEC, since the density of the LWC decreased by 25% with respect to the density of the CC, maintaining the resistance to compression after 28 days Under the same conditions. In conclusion, LWC mixtures made from TEC with raw materials from the metropolitan area of Cúcuta have a lower equilibrium density and compressive strength similar to that of CC

Mechanical behavior of low density concrete mixtures with thermally expanded clay from the metropolitan area of Cúcuta: Comportamiento mecánico de mezclas de concreto de baja densidad con arcilla expandida térmicamente del área metropolitana de

In order to develop construction materials with greater efficiency and performance than conventional materials, mixtures of lightweight concrete (LWC) made from thermally expanded clay (TEC) have been generated. In this article we study the mechanical properties (equilibrium density, compressive strength) of the LWC mixtures produced with raw material from the metropolitan area of Cúcuta, contrasting their characteristics with conventional concrete (CC) mixtures. For this, the lightweight aggregates were developed by calcining clay pellets in a rotary kiln at a pilot plant scale at a temperature of 1050 ° C, generating an expansion of 1.60 times of its initial size. Following the methodology ACI 211.2-98 two concrete mixtures were designed: the first, with fine and coarse aggregate of TEC; and the second, with coarse aggregate of TEC and fine aggregate of sand. It was determined that the LWC mixture with the highest efficiency is the one that uses fine and coarse aggregate of TEC, since the density of the LWC decreased by 25% with respect to the density of the CC, maintaining the resistance to compression after 28 days Under the same conditions. In conclusion, LWC mixtures made from TEC with raw materials from the metropolitan area of Cúcuta have a lower equilibrium density and compressive strength similar to that of CC.In order to develop construction materials with greater efficiency and performance than conventional materials, mixtures of lightweight concrete (LWC) made from thermally expanded clay (TEC) have been generated. In this article we study the mechanical properties (equilibrium density, compressive strength) of the LWC mixtures produced with raw material from the metropolitan area of Cúcuta, contrasting their characteristics with conventional concrete (CC) mixtures. For this, the lightweight aggregates were developed by calcining clay pellets in a rotary kiln at a pilot plant scale at a temperature of 1050 ° C, generating an expansion of 1.60 times of its initial size. Following the methodology ACI 211.2-98 two concrete mixtures were designed: the first, with fine and coarse aggregate of TEC; and the second, with coarse aggregate of TEC and fine aggregate of sand. It was determined that the LWC mixture with the highest efficiency is the one that uses fine and coarse aggregate of TEC, since the density of the LWC decreased by 25% with respect to the density of the CC, maintaining the resistance to compression after 28 days Under the same conditions. In conclusion, LWC mixtures made from TEC with raw materials from the metropolitan area of Cúcuta have a lower equilibrium density and compressive strength similar to that of CC

Efecto de los fenómenos de El Niño y La Niña en la precipitación y su impacto en la producción agrícola del departamento del Atlántico (Colombia)

En la región, bajo condiciones de El Niño, se registran volúmenes deprecipitación (VP) subnormales; y con La Niña, hay lluvias superiores a la normal. Se encontró que el ajonjolí y el plátano aumentan rendimientos si se presentan VP por encima de lo normal (generalmente bajo La Niña) durante el veranillo y en las dos estaciones de lluvias. Los VP por encima de lo normal en la estación seca inciden positivamente en los rendimientos de la yuca. El maíz incrementa sus rendimientos si en el veranillo se registran VP por encima de lo normal, y los reduce si se registran en la segunda temporada lluviosa. El fríjol disminuye rendimientos si los VP en la 1.ª y 2.ª estación lluviosa están por encima de lo normal, y aumenta los rendimientos si estos lo están en el veranillo. Para el algodón los VP por encima de lo normal en la 2.ª estación lluviosa disminuyen los rendimientos. Elsorgo no presentó respuesta notoria a las anomalías en la precipitación

Intraseasonal variability of rainfall over northern south america and caribbean region

Based on decadal (amounts for each ten days) precipitation data from meteorological stations situated in Northern South America and Caribbean region, a decadal precipitation index (DPI) was calculated in order to study the intraseasonal variability (ISV) of regional rainfall. The spectral analysis of DPI allows to identify signals with20-25, 30, 40 and 50-60 days period. According to the analysis of their spatial distribution these signals are well defined over the Caribbean island and coastal sector such as in some sectors of the Andean region; the 60-days signal is presented only over Caribbean region and in some places in the Pacific sector; in the eastern lowlandsof Orinoco and Amazon basin these signals are not clearly expressed.Exploring the relationship between regional ISV and Madden-Julian Oscillation correlation analysis was made.Due to the presence of signals different of 30-60 days, the correlation coefficients were very low. Considering this situation, high frequency smoothing was applied to DPI time series; after that, a relative correlation was detected between smoothed DPI and Madden-Julian Index (MJI)

Impacto socioeconómico dos fenômenos el niño e a la niña na sabana de bogotá durante o século xx

Apresentam-se os resultados de análises da variabilidade climática associada ao ciclo ENOS para a savana de Bogotá. Para a análise tomaram-se os dados das anomalias da temperatura superficial do mar nas zonas EN 1+2, 3, 4 e 3 + 4 do Pacífico tropical, a temperatura média mensal do ar e de precipitação mensal. Identificou-se uma relação inversa entre as anomalias de TSM e a precipitação: condições cálidas (anomalia positiva  de  TSM)  reduzem  a  precipitação  regional,  enquanto  as  condições  frias  (anomalias  negativas associadas a La Niña) a incrementaram. No caso da relação das variações de TSM e a TMMA se observou uma correspondência direta, isto é, a elevação da TSM no Pacífico tropical corresponde a elevação da TMMA da savana de Bogotá. Este efeito climático do ciclo ENOS na Savana de Bogotá durante o século XX trouxe impactos socioeconômicos consideráveis á região. O evento El Niño desencadeou na região limitações na disponibilidade de água para diferentes propósitos (abastecimento a população, agricultura, a indústria) o que afetou a produção agrícola e tem levado ao incremento temporal de preços ao consumidor. Sobre o efeito climático do fenômeno El Niño se incrementa a freqüência dos incêndios da cobertura vegetal, o que afeta de maneira especial os ecossistemas da região. As condições de La Niña, por sua parte, trazem crescentes deslizamentos  inesperados  (nas  zonas  de  alta  declividade  das  montanhas  orientais,  principalmente)  e inundações nas partes baixas (em especial das ribeirinhas dos rios Bogotá, Tunjuelo e San Cristóbal), assim como alagamentos de terrenos. Isso impacta diretamente as moradias e a população de setores urbanos e rurais.Se presentan los resultados del análisis de la variabilidad climática asociada al ciclo ENOS para la Sabana de Bogotá. Para el análisis se tomaron los datos de anomalías de temperatura superficial del mar en  las zonas EN 1+2, 3, 4 y 3+4 del Pacífico tropical, la temperatura media mensual del aire y de precipitación mensual.  Se  identificó  una  relación  inversa  entre  las  anomalías  de  TSM  y  la  precipitación:  condiciones cálidas (anomalías positivas de TSM) reducen la precipitación regional, mientras que las condiciones frías (anomalías negativas asociadas a La Niña) la incrementan. En el caso de la relación de las anomalías de TSM y la TMMA se observó una correspondencia directa, es decir, a ascenso de la TSM en el Pacifico tropical corresponden  ascensos  en  la  TMMA  de  la  Sabana  de  Bogotá.  Este  efecto  climático  del  ciclo  ENOS  en  la  Sabana  de  Bogotá  durante  el  siglo  XX  ha  traído  impactos  socioeconómicos  considerables  a  la  región.  El evento El Niño desencadena en la región limitaciones en la disponibilidad de agua para diferentes propósitos  (abastecimiento a la población, agricultura, industria), lo que ha afectado la producción agrícola y ha llevado al incremento temporal de precios al consumidor. Bajo el efecto climático del fenómeno El Niño se incrementa la frecuencia de los incendios de la cobertura vegetal, lo que afecta de manera especial los ecosistemas de la región. Las condiciones La Niña traen crecientes súbitas y deslizamientos (en las zonas de alta pendiente de los cerros orientales, principalmente) e inundaciones en las partes bajas (en especial en las zonas ribereñas de los ríos Bogotá, Tunjuelo y San Cristóbal), así como anegamiento de terrenos. Esto impacta directamente en las viviendas y la población de sectores urbanos y rurales.The  results  of  an  analysis  of  climate  variability  associated  to  the  ENSO  cycle  for  the  Bogotá Highlands are presented. For this analysis we used data of sea surface temperature (SST) anomalies from the EN1+2, 3, and 3+4 sectors of the tropical Pacific, regional monthly mean air temperature and monthly precipitation. An inverse relationship between SST anomalies and precipitation in the Bogotá Highlands was identified: warm conditions (positive SST anomalies related to El Niño) reduce regional precipitation, while cold conditions (negative anomalies associated to La Niña) increase it. The regional air temperature anomalies have a direct relationship with SST anomalies: a rise of the Pacific SST anomalies correspond to positive air temperature anomalies in the Bogotá Highlands region. The climatic effect of the ENSO cycle over the Bogotá Highlands during 20th century has had important socioeconomic impacts on the region. The El Niño event trigger problems by reducing water resources availability for different uses (supply for population, agriculture, industry), that affects agricultural production and leads to a rise in prices. Under El Niño conditions, the frequency of forest fires increases, which directly affects the regional ecosystems. During  La  Niña  conditions  flashfloods,  landslides  (in  zones  with  steep  slopes),  and  floods  in  lowlands (especially the sectors near the Bogotá, Tunjuelo and San Cristobal rivers) occur; these phenomena directly affect properties in rural and urban areas

El cambio climático y la distribución espacial de las formaciones vegetales en Colombia

Vegetation change under two climate change scenarios in different periods of the 21st Century are modeled for Colombia. Vegetation for the years 1970 to 2000 was reproduced using the Holdridge model with climate data with a spatial resolution of 900 meters. The vegetation types that occupied the most territory were sub-humid tropical forest, tropical dry forest and Andean wet forest. These results were validated by comparing with the Colombian ecosystem map (SINA, 2007), which confirmed a high degree of similarity between the modeled spatial vegetation patterns and modern ecosystem distributions. Future vegetation maps were simulated using data generated by a regional climate model under two scenarios (A2 and B2; IPCC, 2007) for the periods 2011-2040 and 2070-2100. Based on our predictions high altitude vegetation will convert to that of lower altitudes and drier provinces with the most dramatic change occurring in the A2 scenario from 2070-2100. The most affected areas are the páramo and other high Andean vegetation types, which in the timeframe of the explored scenarios will disappear by the middle of the 21st Century.Se analizaron los cambios en  la distribución espacial de la vegetación sobre el territorio colombiano bajo dos escenarios de cambio climático en diferentes períodos del siglo XXI. Así, se reprodujo la distribución de la vegetación del país utilizando el modelo de Holdridge y datos climatológicos del período de referencia 1970-2000 en resolución espacial de 900 metros; en esta reconstrucción la vegetación con mayor ocupación territorial correspondió al bosque subhúmedo  tropical,  el  bosque  seco  tropical  y  el  bosque andino bajo húmedo.  Se efectuó la validación de los resultados mediante la comparación de la distribución obtenida y el mapa de ecosistemas del país producido por el Sistema de Información Nacional Ambiental (SINA), lo que corroboró un alto grado de aproximación entre los patrones espaciales modelados y  los ecosistemas del país. Adicionalmente, se tomaron las variables climatológicas generadas para Colombia por un modelo climático regional en  dos escenarios (A2 y B2 de IPCC, 2007) para los periodos 2011-2040 y 2070-2100 y se generó la distribución de la vegetación correspondiente a esos períodos y escenarios. Mediante la comparación de las distribuciones  de los períodos actual (1970-2000) y futuros (2011-2040 y 2070-2100) se establecieron los cambios que habría en la vegetación hacia esos períodos.La vegetación tiende hacia pisos altitudinales más bajos y provincias de humedad más secas;  el cambio más drástico ocurre en el escenario A2 para el periodo 2070-2100. La vegetación que más se afectan es el páramo y las alto andinas, que según los escenarios climáticos explorados, desaparecerían ya a mediados del siglo XXI.

ESTADO DEL ARTE DE LAS CELDAS DE COMBUSTIBLE

Las celdas de combustible han sido implementadas desde hace varias décadas, la NASA desde 1960 las ha usado en sus programas espaciales, sin embargo, no se le ha dado la importancia que esta tecnología debería tener al ser una opción ambientalista y eficiente en su conversión y aporte energético. Este trabajo presenta una conceptualización y revisión de la literatura de las pilas, células o celdas de combustible con el objetivo de comprender fácilmente su comportamiento para contribuir con su divulgación en Colombia. Los temas enunciados en este documento son la clasificación de estos dispositivos, permitiendo identificar las características y el principio de funcionamiento; también se realiza una revisión de diferentes proyectos y artículos que evidencian los avances y aplicaciones desde el área académica hasta la industria, los documentos examinados fueron 57, estas investigaciones realizadas cubren un periodo de tiempo desde el año 2004 hasta 2018

IMPLEMENTATION OF THE ELECTRICAL-ELECTRONIC SYSTEM AND SOFTWARE SYSTEM OF A CNC MACHINE

This article presents the operation of a CNC router controlled by a free open source firmware (GRBL) that runs on the Arduino Uno R3 card, thus describing and justifying the components that are part of the electrical-electronic system and the computer programs that constitute the software system for the machining of printed circuit boards. The tests performed recorded an estimated time of 21: 86 in minutes: seconds divided into the three processes of engraving (paths 13:12, holes 6:48 and contour 2:26 given in minutes: seconds), these values can vary depending on the dimensions of the required PCB, even so it turns out to be more efficient in quality and time compared to the conventional method of chemical attack