University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

La actividad proteolítica de los venenos de serpientes de Costa Rica sobre la caseína

Abstract: Experimental conditions for the comparative measurement of proteolytic activity of Costa Rican snake venoms on casein are established, and the activity of 13 different venoms is described Venoms showed marked differences in activity not only between species, but between specimens of the same species captured in different geographic regions of Costa Rica

Seismicity related to the glacier of Cotopaxi Volcano, Ecuador

Abstract: [1] Significant seismic activity is generally recorded on volcanoes covered by an icecap. This work was carried out in order to quantify the role of the glaciers in the generation of seismicity for Cotopaxi volcano. We compared the seismic activity registered on the glacier and on the rock near the snout of the north flank glacier. We focused on the analysis of low frequency events (<5 Hz) similar to volcanic LP events when recorded on rock base. The particle motion analysis helps to estimate source locations, which are distributed in crevasses areas. High incident angles suggest a superficial origin. These events are interpreted as icequakes for which we propose as source mechanism a fluid-driven crack model triggered by ice cracking or hydraulic transients. The low quality factor values estimated are consistent with the resonance of an ice crack filled with water. This work shows that low frequency icequakes can be confusingly taken as volcanic LP events.

An Enhanced $dq$-Based Vector Control System for Modular Multilevel Converters Feeding Variable-Speed Drives

Abstract: Modular multilevel converters (M $^{\text{2}}$ C) are considered an attractive solution for high power drive applications. However, energy balancing within the converter is complex to achieve, particularly when the machine is operating at low rotational speeds. In this paper, a new control system, based on cascaded control loops and a vector-power-voltage ( $vPV$ ) model of the M $^{\text{2}}$ C, is proposed. The control system is implemented in a $dq$ -synchronous frame rotating at $\omega _e$ rad/s with the external loop regulating the capacitor voltages using proportional-integral (PI) controllers. The internal loop controls the converter currents using PI and resonant controllers. In addition, the control systems required to operate the machine at other points, i.e., at medium and high rotational speeds, are also discussed in this paper. Experimental results obtained with an M $^{\text{2}}$ C-based drive laboratory prototype with 18 power cells are presented in this paper.