• Journal of Power Electronics
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• v.19 no.1
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• pp.68-78
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• 2019

The emergence of high voltage conversion applications has resulted in a trend of using semiconductor device series associations. Series associations allow for operation at blocking voltages, which are higher than the nominal voltage for each of the semiconductor devices. The main challenge with these topologies is finding a way to guarantee the voltage balance between devices in both blocking and switching transients. Most of the methods that have been proposed to mitigate static and dynamic voltage unbalances result in increased losses within the device. This paper introduces a new series stack topology, where the voltage unbalances are reduced. This in turn, mitigates the switching losses. The proposed topology consists of a circuit that ensures the soft switching of each device, and one auxiliary circuit that allows for switching energy recovery. The principle for the topology operation is presented and experimental tests are performed for two modules. The topology performs excellently for switching transients on each of the devices. The voltage static unbalances were limited to 10%, while the activation/deactivation delay introduced by the lower module IGBT driver takes place in the dynamic unbalances. Thus, the switching losses are reduced by 40%, when compared to hard switching configurations.

• Asian Journal of Atmospheric Environment
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• v.12 no.3
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• pp.232-243
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• 2018

The construction, development and maintenance of an economically, environmentally and socially sustainable campus involves the integration of measuring tools and technical information that invites and encourages the community to know the actual state to generate positive actions for reducing the negative impacts over the local environment. At the Universidad Nacional de Colombia - Campus $Bogot{\acute{a}}$, a public area with daily traffic of more than 25000 people, the Environmental Management Bureau has committed with the monitoring of the noise pollution and air quality, as support to the campaigns aiming to reduce the pollutant emissions associated to the student's activities and campus operation. The target of this study is based in the implementation of mobile air quality and sonometry monitoring equipment, the mapping of the actual air quality and noise pollution inside the university campus as a novel methodology for a sub-area inside a megacity. This results and mapping are proposed as planning tool for the institution administrative sections. A mobile Kunak$^{(R)}$ Air & OPC air monitoring station with the capability to measure particulate matter $PM_{10}$, $PM_{2.5}$, Ozone ($O_3$), Sulfur Oxide ($SO_2$), Carbon Monoxide (CO) and Nitrogen Oxide ($NO_2$) as well as Temperature, Relative Humidity and Latitude and Longitude coordinates for the data georeferenciation; and a sonometer Cirrus$^{(R)}$ 162B Class 2 were used to perform the measurements. The measurements took place in conditions of academic activity and without it, with the aim of identify the impacts generated by the campus operation. Using the free code geographical information software QGIS$^{(R)}$ 2.18, the maps of each variable measured were developed, and the impacts generated by the operation of the campus were identified qualitative and quantitively. For the measured variables, an increase of around 21% for the $L_{Aeq}$ noise level and around 80% to 90% for air pollution were detected during the operation period.

• Korean Journal of Food Science and Technology
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• v.41 no.4
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• pp.362-368
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• 2009

Roasting may lead to the formation of undesired compounds, such as polycyclic aromatic hydrocarbons (PAHs). In this study, green coffee beans were roasted under controlled conditions and the formation of PAHs during the roasting process was monitored. Roasting was performed in a hot air roaster, with an inlet air temperature varying from 150 to $250^{\circ}C$ for 5, 10, and 20 min. The PAH content of the roasted coffee was then evaluated by HPLC-FLD. The levels of total PAHs in Arabica (Colombia, Brazil) and Robusta (India) coffee samples were 1.26-215.07, 1.85-178.14, and 0.18-2.61 ${\mu}g$/kg, respectively.

• Mineral and Industry
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• v.27
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• pp.50-57
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• 2014

• Geomechanics and Engineering
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• v.15 no.3
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• pp.899-910
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• 2018

Terrace deposits are often encountered in portal areas and tunnels with low overburden. They are challenging to excavate considering their great mechanical and spatial heterogeneity and a very high stiffness contrast within the ground. Terrace deposits are difficult to characterize, considering that samples for laboratory testing are almost unfeasible to obtain, and laboratory tests may not be representative due to scale effects. This paper presents the approach taken for their characterization during the design stage and their posterior validation performed during construction. Lessons learned from several tunnels excavated on terrace deposits on the Bogota-Villavicencio road (central-east Colombia), suggest that based on numerical simulations, laboratory testing and tunnel system behaviour monitoring, an observational approach allows engineers to optimize the excavation and support methods for the encountered ground conditions, resulting in a more economic and safe construction.

• Culinary science and hospitality research
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• v.10 no.3
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• pp.65-82
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• 2004

This research is to make an attempt the analysis award consumption state, import and export in the world coffee market. This research results were as follows. First, The result of the analysis of Korea coffee market, imports of green bean were 1,316,000 bags from export countries in 2000. Re-exports of processed coffee were 71,000 bags in 2000. Main suppliers were Brazil, Viet Nam, Honduras, Colombia, Indonesia. Second, The result of the analysis of United State coffee market, imports of all forms of coffee were 19.29 million bags. Main suppliers were Brazil(15%), Viet Nam(15%), Colombia(17%) etc. Third, The result of the analysis of Japan market, imports of green beans were 6.37million bags in 2001. Re-exports of processed coffee were 166.000million bags. Consumption per head in 2001 was about 3.5 kg and Japanese coffee consumer now drink on average 11.0 cups per week.

• Korean Journal of Veterinary Research
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• v.62 no.4
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• pp.28.1-28.4
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• 2022

Splenic myelolipoma is a rare tumor in dogs with an unclear origin. A male 13-year-old Schnauzer dog was presented because of a bump on the left side of the abdomen. Clinical examination and abdominal ultrasound revealed a mass in the spleen. A total splenectomy was carried out, and histopathology revealed a splenic myelolipoma. Before surgery, the patient showed high serum alanine aminotransferase levels, which returned to normal eight months after the resection. Unfortunately, the postoperative follow-up showed increased serum cholesterol and triglyceride levels, suggesting liver compromise. This is the first report of a splenic myelolipoma in Colombia.

• Korean Journal of Veterinary Research
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• v.63 no.1
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• pp.4.1-4.5
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• 2023

The prevalence of some swine reproductive and zoonotic diseases in Colombia is unknown, making their management difficult. This study assessed the prevalence of porcine circovirus type 3 (PCV3), Leptospira interrogans, pseudorabies virus, and porcine gamma-herpesvirus by polymerase chain reaction in sows in the productive stage, from farms with a history of reproductive failures, at the department of Tolima. The prevalence of PCV3 was 2.6% and 12.6% for L. interrogans, with some samples co-infected with PCV2. Owing to the coinfections with PCV2, it is necessary to establish whether the interactions between these pathogens were related to the presence of reproductive problems.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.539-546
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• 2010

• The Plant Pathology Journal
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• v.34 no.5
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• pp.393-402
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• 2018

Rice world production is affected due to the growing impact of diseases such as bacterial panicle blight, produced by Burkholderia glumae. The pathogen-induced symptoms include seedling rot, grain rot and leafsheath browning in rice plants. It is currently recognized the entrance of this pathogen to the plant, from infected seeds and from environmental sources of the microorganism. However, it is still not fully elucidated the dynamics and permanence of the pathogen in the plant, from its entry until the development of disease symptoms in seedlings or panicles. In this work it was evaluated the infection of B. glumae rice plants, starting from inoculated seeds and substrates, and its subsequent monitoring after infection. Various organs of the plant during the vegetative stage and until the beginning of the reproductive stage, were evaluated. In both inoculation models, the bacteria was maintained in the plant as an endophyte between $1{\times}10^1$ and $1{\times}10^5cfu$ of B. $glumae.g^{-1}$ of plant throughout the vegetative stage. An increase of bacterial population towards initiation of the panicle was observed, and in the maturity of the grain, an endophyte population was identified in the flag leaf at $1{\times}10^6cfu$ of B. $glumae.g^{-1}$ fresh weight of rice plant, conducting towards the symptoms of bacterial panicle blight. The results found, suggest that B. glumae in rice plants developed from infected seeds or from the substrate, can colonize seedlings, establishing and maintaining a bacterial population over time, using rice plants as habitat to survive endophyticly until formation of bacterial panicle blight symptoms.