On December 31, 2019, the Chinese authorities reported to the World Health Organization (WHO) the outbreak of a new strain of coronavirus that causes a serious disease in the city of Wuhan, China. This outbreak was classified as SARS-CoV2 and is the cause of the COVID-19 disease. On March 11, 2020, the WHO declares it a Pandemic and today it is considered the greatest challenge in global health that humanity has faced since World War II and it is estimated that between 40 and 60% of the population worldwide will catch the virus. This has caused enormous challenges in countries around the world in social, economic, environmental and obviously health issues. These challenges are mainly due to the effects of the established quarantines in almost all capitals and major cities around the world, from Asia, Europe to America. However, these lockdown which began worldwide from January 23, have had a significant impact on the environment and on the air quality of cities as recently reported by NASA (National Aeronautics and Space Administration) and ESA (European Space Agency), with reductions according to them of up to 30% in some of the epicenters such as the case of Wuhan. Knowing that air pollution causes approximately 29% of lung cancer deaths, 43% of COPD deaths, and 25% of ischemic heart disease deaths, it is important to know the effects of quarantines in cities regarding air quality to take measures that favor populations and urban ecosystems when the emergency ends. Therefore, this paper describes the behavior of PM 2.5 emissions particulate matter from the 50 most polluted capital cities in the world according to the WHO, measured before-after the start of the quarantine. Likewise, the impact at the local and global level of this emissions behavior, which averaged 12% of PM 2.5 decrease in these cities.

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Currently, developed countries have been implementing sustainable development policies specifically in Sustainable Consumption and Production (SCP). Therefore, companies consider the products and services life cycle, where Green Procurement (GP) represents a key tool for sustainability in the Supply Chain (SC). Moreover, the future on green policies in countries like Colombia has a long way to go on issues such as energy production, consumption and processes within the supply chain. In the GP area, there are three relevant issues in sustainable development policies in Colombia: 1) issues linked to barriers in the implementation such as tariffs, taxes, incentives and promotion; 2) motivation and drivers for the implementation for both public and private sector and 3) performance impacts related to the models used in order to implement in companies. The latter one is the main interest of this paper. Regarding this work, it identifies the mathematical models most widely used in SC processes, especially the issues associated with purchase processes, selection and hiring of suppliers in large and medium-sized enterprises; public or private. Moreover, the paper analyzes the models regarding their advantages and disadvantages on which some of these can be used in GP processes due its high impact. Finally, a possible mathematical model used in GP processes based on petri nets (PN) for to their characteristics and application in complex systems.

Naphtha is an important distillation product of crude oil, and is used as a raw material for first-generation products such as ethylene, propylene, gasoline, xylene (BTX), and others. However, due to the different sources of crude oil, differences in naphtha composition impact the quality of conversion processes. Parameters such as pressure, charge flow, and temperature need to be adjusted for conversion efficiency. This work aims to compare naphtha samples from different origins, through the analysis of distillation curve (ASTM D86), density (ASTM D4052), total sulfur (ASTM D4294), and n-paraffins, iso-paraffins, olefins, naphthene, and aromatics (PIONA, ASTM D5134). Among these parameters evaluated in naphtha, the ones that showed the greatest correlation with the type of oil and its origin was the amount of total sulfur, number of aromatics, and paraffins. The three imported evaluated naphtha presented values greater than 200 mg/kg of total sulfur, aromatics above 9%w, and paraffins (P + I) below 76%w, while the national naphtha presented sulfur contents of at most 141 mg/kg, aromatics below 7%w, and paraffins (P + I) above 78%w. Finally, the study of this type of hydrocarbon enables the understanding of the needs of Latin American refineries and the world in relation to its treatment. National petrochemical companies have more difficulty in processing this product, causing an increase in naphtha importation by 108.51% from 2020/2021 in Brazil. Given this scenario, the Brazilian government should invest more in its petrochemical plants to reduce these imports, which, in the long term, would have a positive impact on the quality and value of naphtha byproducts.

This paper presents a fault diagnosis application of the Latent Nestling Method to IGBTs. The paper extends the Latent Nestling Method based in Coloured Petri Nets (CPNs) to hybrid systems in such a manner that IGBTs performance can be modeled. CPNs allow for an enhanced capability for synthesis and modeling in contrast to the classical phenomena of combinational state explosion when Finite State Machine methods are applied. We present an IGBT model with different fault modes including those of intermittent nature that can be used advantageously as predictive symptoms within a predictive maintenance strategy. Ageing stress tests have been experimentally applied to the IGBTs modules and intermittent faults are diagnosed as precursors of permanent failures. In addition, ageing is validated with morphological analysis (Scanning Electron Microscopy) and semiqualitative analysis (Energy Dispersive Spectrometry).

This paper presents one of the most important and representative projects in the country concerning isolated energy systems. The Institute of Planning and Promotion of Energy Solutions (IPSE) conducted this project for noninterconnected zones under the Ministry of Mines and Energy of Colombia. This project targets two main objectives: To increase the hours of electricity supply to the population and reduce the hours of use of diesel plants. This project allows for the production of electricity from solar radiation through "preinstalled solar trackers -100kWp installed power" and a new solar farm which supplies 220kWp, plus a battery room with 480 cells and installed capacity storage 3,148kWh. Finally, the facility has been supported by two 308kW diesel plants.This paper presents the largest PV system isolated from Colombia so far. First, we make a geographical description of the area of project implementation, also an approach to the indigenous community, their customs and their social and technological issues. Likewise, the paper presents some of the challenges and difficulties of setting up the project in an isolated area of difficult access and complex environmental conditions. In addition, the stages of assembly and some technical details of installation are presented, highlighting the design features and implementation with respect to civil works, electrical works and the main