33 results on '"Sierra Aguilar"'
Search Results
2. Risk assessment of occupational skin cancer among outdoor workers in southern Spain: local pilot study
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Magdalena de Troya Martín, Sierra Aguilar, José Aguilera-Arjona, Francisco Rivas-Ruiz, Alba Rodríguez-Martínez, Guillermo de Castro-Maqueda, Jacobo Cambil-Martín, Victoria de Gálvez-Aranda, and Nuria Blázquez-Sánchez
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Occupational Diseases ,Cross-Sectional Studies ,Skin Neoplasms ,Spain ,Ultraviolet Rays ,Occupational Exposure ,Public Health, Environmental and Occupational Health ,Humans ,Sunburn ,Pilot Projects ,Risk Assessment - Abstract
ObjectiveOverexposure to ultraviolet (UV) radiation is the main preventable cause of skin cancer. Outdoor workers, exposed to the sun for many hours throughout their working lives, are at special risk. The aim of this study is to determine occupational photoexposure and photoprotection among outdoor workers employed by a municipality in southern Spain.MethodsCross-sectional descriptive study focusing on outdoor workers employed by the municipality of Fuengirola (in areas such as construction, gardening, urban cleaning and beach maintenance). The participants were monitored by personal dosimetry, participated in a dermatological check-up and answered a validated questionnaire (CHACES) on their habits, attitudes and knowledge related to sun exposure.ResultsThe median effective erythema dose of exposure to solar UV radiation during the working day (n=20) was 379.4 J/m2, equivalent to 3.8 standard erythema doses, almost 3 times higher than the recommended limits for an 8-hour workday. Skin examination (n=128) revealed the presence of actinic lentigines (79.7%), actinic keratoses (8.6%) and skin cancer (3.9%). The CHACES questionnaire (n=128) revealed a sunburn rate of 50.0%. Photoprotection practices were markedly deficient: only 16.7% of the survey respondents sought protection in the shade, 20.3% avoided exposure during the peak exposure hours and 33.1% applied sunscreen.ConclusionsThis is the first study to evaluate UV radiation exposure, occupational sun protection practices, sunburn and actinic injuries of different outdoor workers in one of the sunniest regions of Spain and underlines the need for effective interventions to protect outdoor workers’ health.
- Published
- 2022
3. A Multi-Period Optimal Reactive Power Dispatch Approach Considering Multiple Operative Goals
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Jairo A. Morán-Burgos, Juan E. Sierra-Aguilar, Walter M. Villa-Acevedo, and Jesús M. López-Lezama
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maneuvers ,control actions ,pilot nodes ,multi-period ,reactive power reserves ,reactive power dispatch ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The optimal reactive power dispatch (ORPD) problem plays a key role in daily power system operations. This paper presents a novel multi-period approach for the ORPD that takes into account three operative goals. These consist of minimizing total voltage deviations from set point values of pilot nodes and maneuvers on transformers taps and reactive power compensators. The ORPD is formulated in GAMS (General Algebraic Modeling System) software as a mixed integer nonlinear programming problem, comprising both continuous and discrete control variables, and is solved using the BONMIN solver. The most outstanding benefit of the proposed ORPD model is the fact that it allows optimal reactive power control throughout a multi-period horizon, guaranteeing compliance with the programmed active power dispatch. Additionally, the minimization of maneuvers on reactors and capacitor banks contributes to preserving the useful life of these devices. Furthermore, the selection of pilot nodes for voltage control reduces the computational burden and allows the algorithm to provide fast solutions. The results of the IEEE 118 bus test system show the applicability and effectiveness of the proposed approach.
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- 2021
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4. Diseño de un centro educativo para 120 estudiantes en la zona rural del municipio de Matanza, Santander
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Sierra Aguilar, María Paula and Barrientos Monsalve, Ender José
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local progress ,escuela nueva ,progreso local ,new school ,Centros educativos - arquitectura ,Zonas escolares - arquitectura ,zona rural ,educational center ,aprendizaje ,rural area ,learning ,centro educativo ,Salones escolares - arquitectura - Abstract
El siguiente trabajo contiene la propuesta de diseño de un centro educativo para la zona rural del municipio de Matanza con el objetivo de generar un espacio que permita el desarrollo del proceso enseñanza / aprendizaje, promueva el desarrollo infantil integral de niños y jóvenes y contribuya al progreso de la localidad, la propuesta se desarrollara a partir del modelo educativo escuela nueva, la aplicación de normativa correspondiente, el análisis tipológico de referentes, comprendiendo el funcionamiento y distribución espacial de los equipamientos educativos y la observación directa del lugar para conocer las determinantes del sitio, las necesidades existentes de la comunidad educativa y las características del usuario, dando como resultado un proyecto enfocado en generar espacios arquitectónicos funcionales y accesibles que garanticen una formación digna y exitosa a partir de la implementación de áreas que desarrollen sus dimensiones corporal, cognitiva y socio-afectiva, además de una integración en la comunidad logrando un mayor interés en el proceso de aprendizaje de los estudiantes. The following work contains the design proposal of an educational center for the rural area of the municipality of Matanza with the objective of generating a space that allows the development of the teaching / learning process, promotes the integral child development of children and young people and contributes to the progress of the locality, the proposal will be developed from the new school educational model, the application of corresponding regulations, the typological analysis of references, understanding the functioning and spatial distribution of the educational facilities and the direct observation of the place to know the determinants of the site, the existing needs of the educational community and the characteristics of the user, resulting in a project focused on generating functional and accessible architectural spaces that guarantee a dignified and successful training from the implementation of areas that develop their physical, cognitive and socio-affective dimensions, in addition to an integration in the community achieving a greater interest in the learning process of the students. Arquitecto http://www.ustabuca.edu.co/ustabmanga/presentacion Pregrado
- Published
- 2023
5. A New Affinely Adjustable Robust Model for Security Constrained Unit Commitment under Uncertainty
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Juan Esteban Sierra-Aguilar, Cristian Camilo Marín-Cano, Jesús M. López-Lezama, Álvaro Jaramillo-Duque, and Juan G. Villegas
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power system ,security-constraint unit commitment ,robust optimization ,uncertainty ,renewable energy sources ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Currently, optimization models for the safe and reliable operation of power systems deal with two major challenges: the first one is the reduction of the computational load when considering N−1 contingencies; the second one is the adequate modeling of the uncertainty of intermittent generation and demand. This paper proposes a new affinely adjustable robust model to solve the security constrained unit commitment problem considering these sources of uncertainty. Linear decision rules, which take into account the forecasts and forecast errors of the different sources of uncertainty, are used for the affine formulation of the dispatch variables, thus allowing the tractability of the model. Another major novelty is that the evaluation of the N−1 security constraints is performed by incorporating a novel method, proposed in the literature, based on the user-cuts concept. This method efficiently and dynamically adds only the binding N−1 security constraints, increasing the computational efficiency of the model when transmission line contingencies are considered. Finally, Monte Carlo simulations on the post-optimization results were run to demonstrate the effectiveness, feasibility and robustness of the solutions provided by the proposed model.
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- 2021
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6. A Novel Strategy to Reduce Computational Burden of the Stochastic Security Constrained Unit Commitment Problem
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Cristian Camilo Marín-Cano, Juan Esteban Sierra-Aguilar, Jesús M. López-Lezama, Álvaro Jaramillo-Duque, and Juan G. Villegas
- Subjects
power system optimization ,Security-Constraint Unit Commitment ,progressive hedging algorithm ,Technology - Abstract
The uncertainty related to the massive integration of intermittent energy sources (e.g., wind and solar generation) is one of the biggest challenges for the economic, safe and reliable operation of current power systems. One way to tackle this challenge is through a stochastic security constraint unit commitment (SSCUC) model. However, the SSCUC is a mixed-integer linear programming problem with high computational and dimensional complexity in large-scale power systems. This feature hinders the reaction times required for decision making to ensure a proper operation of the system. As an alternative, this paper presents a joint strategy to efficiently solve a SSCUC model. The solution strategy combines the use of linear sensitivity factors (LSF) to compute power flows in a quick and reliable way and a method, which dynamically identifies and adds as user cuts those active security constraints N − 1 that establish the feasible region of the model. These two components are embedded within a progressive hedging algorithm (PHA), which breaks down the SSCUC problem into computationally more tractable subproblems by relaxing the coupling constraints between scenarios. The numerical results on the IEEE RTS-96 system show that the proposed strategy provides high quality solutions, up to 50 times faster compared to the extensive formulation (EF) of the SSCUC. Additionally, the solution strategy identifies the most affected (overloaded) lines before contingencies, as well as the most critical contingencies in the system. Two metrics that provide valuable information for decision making during transmission system expansion are studied.
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- 2020
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7. Metodología computacionalmente eficiente para resolver el despacho económico multiperiodo estocástico con restricciones de seguridad
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Alvaro Jaramillo Duque, Juan Esteban Sierra Aguilar, Jesús María López Lezama, and Cristian Camilo Marín Cano
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Welfare economics ,Mathematics - Abstract
espanolObjetivo: Validar una metodologia computacionalmente eficiente para resolver el problema de despacho economico multiperiodo estocastico con restricciones de seguridad. Metodologia: Se utilizan factores lineales de sensibilidad para calcular flujos de carga de forma rapida y precisa. Tambien se usa un metodo iterativo, que identifica y agrega como cortes de usuario, las restricciones de seguridad activas. Estas restricciones establecen la region factible de un modelo embebido dentro de un algoritmo Progressive Hedging, el cual descompone el problema principal en un conjunto de sub-problemas computacionalmente mas tratables, al relajar las restricciones de acoplamiento entre escenarios. Resultados: Los resultados numericos sobre el sistema IEEE RTS96, muestran que la estrategia propuesta entrega soluciones de alta calidad en bajos tiempos de calculo. Conclusiones: La metodologia propuesta permite solucionar el despacho economico multiperiodo estocastico seguro hasta 50 veces mas rapido cuando se compara con su formulacion extensiva. EnglishObjective: Validate a computationally efficient approach to solve the stochastic security constraint unit commitment problem. Methodology: Linear sensitivity factors are used to compute power flows in a fast and accurate way. It is also used an iterative method that identifies and adds as user cuts the set of active constraints. These constraints establish the feasible region of a model embedded within a Progressive Hedging algorithm, which decomposes the main problem into a set of computationally more tractable sub-problems by relaxing the coupling constraints between scenarios. Results: The numerical results on the IEEE RTS96 system show that the proposed strategy provides high quality solutions with low calculation times. Conclusions: The proposed methodology allows the stochastic security-constraint unit commitment problem to be solved up to 50 times faster when compared to its extensive formulation.
- Published
- 2021
8. Carpal Tunnel Syndrome: Assessment of Surgeon and Patient Preferences and Priorities for Decision-Making
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Abzug, Joshua M., Adams, Julie, Arbelaez, Gallo Fabio, Aspard, T., Balfour, George W., Bamberger, H. Brent, Barreto, Romero Jose Camilo, Baskies, Michael, Batson, W. Arnold, Baxamusa, Taizoon, de Bedout, Ramon, Beldner, Steven, Benhaim, Prosper, Benson, Leon, Boretto, G. Jorge, Boyer, Martin, Dee Byrd, Gregory, Calfee, Ryan P., Zambrano, Gladys Cecilia, Cassidy, Charles, Catalano, Louis, III, Chivers, Karel, Costanzo, Ralph M., Dantuluri, Phani, DeSilva, Gregory, Dodds, Seth, Evans, John P., Felipe, Naquira Escobar Luis, Fernandes, C.H., Fischer, Thomas J., Fischer, Jochen, Fricker, M. Renato, Frykman, Gary K., Garcia, Aida E., Gaston, R. Glenn, Di Giovanni, José Fernando, Goldfarb, Charles A., Grafe, Michael W., Grunwald, H.W., Hammert, Warren C., Hauck, Randy, Hernandez, Ricardo German, Hofmeister, Eric, Hutchison, Richard L., Ilyas, Asif, Isaacs, Jonathan, Jacoby, Sidney M., Jebson, Peter, Jones, Christopher M., Jones, Michael, Kakar, Sanjeev, Kalainov, David M., Kaplan, Thomas D., Kaplan, Saul, Katolik, Leonid, Kennedy, Stephen A., Kessler, Michael W., Kimball, Hervey L., Kraan, G.A., Martineau, Paul A., McAuliffe, John, McCabe, Steven J., McKee, Desirae M., Merrell, Greg, Metzger, Charles, Nancollas, Michael, Nelson, David L., Nyszkiewicz, Ralf, Ortiz, Jose A., Owens, Patrick W., Palmer, Jason M., Paz, Lior, Pess, Gary, Polatsch, Daniel, Raia, Frank J., Richard, Marc J., Rizzo, Marco, Rozental, Ruchelsman, David, Semenkin, Oleg M., Sierra, Aguilar Javier Francisco, Siff, Todd, Sodha, Samir, Spath, Catherine, Spruijt, Sander, Stackhouse, Thomas F., Swigart, Carrie, Szabo, Robert, Taras, John, Tavakolian, Jason, Terrono, Andrew, Varecka, Thomas F., Wahegaonkar, Abhijeet L., Walsh, Christopher J., Walter, Frank L., Weiss, Lawrence, Wills, Brian P.D., Wilson, Chris, Wilson, Christopher, Wolf, Jennifer Moriatis, Wood, Megan, Young, Colby, Hageman, Michiel G.J.S., Kinaci, Ahmet, Ju, Kevin, Guitton, Thierry G., Mudgal, Chaitanya S., and Ring, David
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- 2014
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9. Implementation of User Cuts and Linear Sensitivity Factors to Improve the Computational Performance of the Security-Constrained Unit Commitment Problem
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Cristian Camilo Marín-Cano, Juan Esteban Sierra-Aguilar, Jesús M. López-Lezama, Álvaro Jaramillo-Duque, and Walter M. Villa-Acevedo
- Subjects
optimization ,power system ,Security-Constraint Unit Commitment ,sensitivity factors ,user cuts ,Technology - Abstract
Power system operators must schedule the available generation resources required to achieve an economical, reliable, and secure energy production in power systems. This is usually achieved by solving a security-constrained unit commitment (SCUC) problem. Through a SCUC the System Operator determines which generation units must be on and off-line over a time horizon of typically 24 h. The SCUC is a challenging problem that features high computational cost due to the amount and nature of the variables involved. This paper presents an alternative formulation to the SCUC problem aimed at reducing its computational cost using sensitivity factors and user cuts. Power Transfer Distribution Factors (PTDF) and Line Outage Distribution Factors (LODF) sensitivity factors allow a fast computation of power flows (in normal operative conditions and under contingencies), while the implementation of user cuts reduces computational burden by considering only biding N-1 security constraints. Several tests were performed with the IEEE RTS-96 power system showing the applicability and effectiveness of the proposed modelling approach. It was found that the use of Linear Sensitivity Factors (LSF) together with user cuts as proposed in this paper, reduces the computation time of the SCUC problem up to 97% when compared with its classical formulation. Furthermore, the proposed modelling allows a straightforward identification of the most critical lines in terms of the overloads they produce in other elements after an outage, and the number of times they are overloaded by a fault. Such information is valuable to system planners when deciding future network expansion projects.
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- 2019
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10. Despacho económico multiperiodo con restricciones de seguridad usando los factores de sensibilidad PTDF y LODF
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Cristian Camilo Marin, Jesús María López Lezama, Juan Esteban Sierra Aguilar, and Alvaro Jaramillo Duque
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General Medicine - Abstract
espanolEl problema de despacho economico multiperiodo (DEM) consiste en determinar de manera optima que unidades de generacion deben suministrar potencia al sistema en un horizonte de tiempo tipico de 24 horas. El DEM con restricciones de seguridad (SCUC por sus siglas en ingles) es un problema de alto costo computacional debido a la cantidad y naturaleza de las variables involucradas. En este articulo se presenta una formulacion alternativa del SCUC para reducir su costo computacional, mediante el uso de los factores de sensibilidad PTDF y LODF. En contraste con las formulaciones clasicas, el uso de estos factores permite calcular flujos de carga sin necesidad de utilizar los angulos nodales, reduciendo el numero de variables y restricciones del modelo. Ademas, se implementa una metodologia de filtro de contingencias activas N-1 que reduce aun mas la carga computacional, a traves de cortes de usuario. Se presentan resultados para el sistema IEEE-RTS96 que evidencian la robustez y aplicabilidad del modelo propuesto. Se encontro que el uso de los factores de sensibilidad PTDF y LODF, en conjunto con la metodologia de filtros de contingencias, reduce el costo computacional hasta en un 86% con respecto a su formulacion convencional. Adicionalmente, la metodologia propuesta identifica que lineas son mas vulnerables debido a sobrecargas, y cuales lineas causan mayores impactos al sistema cuando fallan. EnglishThe unit commitment (UC)problemconsists in optimally determining which generation units must supply power to the system in a typical time horizon of 24 hours. The security-constrained unit commitment (SCUC) is a problem of high computational cost due to the quantity and nature of the variables involved. This paper presents an alternative formulation of the SCUC to reduce its computational cost, by using the PTDF and LODF sensitivity factors. In contrast toclassic formulations, the use of these factors allows calculating powerflows without using nodal angles, reducing the number of variables and constraints of the model. In addition, an N-1 active contingency filter methodology is implemented that further reduces the computational burden through user cuts. Results are presented for theIEEE-RTS96 system that demonstrates the robustness and applicability of the proposed approach. It was found that the use of PTDF and LODF sensitivity factors, in conjunction with the contingency filter methodology, reduces the computational cost by up to 86% with respect to its conventional formulation. Additionally, the proposed methodology identifies which lines are more vulnerable due to overloads, and which lines cause the greatest impacts to the system when they fail.
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- 2020
11. Despacho económico robusto ante fuentes renovables intermitentes con incertidumbre
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Sierra Aguilar, Juan Esteban, Jaramillo Duque, Álvaro, and Mejía Giraldo, Diego Adolfo
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Optimization ,vocabularies.unesco.org/thesaurus/concept6659 [http] ,Renewable energy ,Despacho económico ,Statistical uncertainty ,agrovoc:c_25719 ,Consumo de energía eléctrica ,agrovoc:c_28975 ,Energía renovable ,Optimización ,Demanda de energía ,Incertidumbre estadística ,Economía de la energía - Abstract
RESUMEN : La presencia cada vez más significativa de las Fuentes de Energía Renovables Intermitentes (FREI) en los sistemas eléctricos ha hecho que se deban considerar nuevas estrategias para coordinar la operación del sistema. A nivel del UC, uno de los mayores retos para un Operador del Sistema (System operator) (SO) corresponde a la implementación de algoritmos capaces de considerar la incertidumbre de los recursos intermitentes y de las variaciones de la demanda. Este trabajo presenta un modelo robusto afín ajustable para mitigar la incertidumbre de las fuentes renovables intermitentes, permitiendo una operación no solo segura, sino también económica.
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- 2022
12. A Multi-Period Optimal Reactive Power Dispatch Approach Considering Multiple Operative Goals
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Morán-Burgos, Jairo A., primary, Sierra-Aguilar, Juan E., additional, Villa-Acevedo, Walter M., additional, and López-Lezama, Jesús M., additional
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- 2021
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13. Metodología computacionalmente eficiente para resolver el despacho económico multiperiodo estocástico con restricciones de seguridad
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López Lezama, Jesús María, primary, Sierra Aguilar, Juan Esteban, additional, Marín Cano, Cristian Camilo, additional, and Jaramillo Duque, Alvaro, additional
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- 2021
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14. Forma Óptima de un Buen Gobierno Corporativo
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Sierra Aguilar, Ivonne Alexandra, Carreño Dueñas, Dalia, and Restrepo Restrepo, Jose Arturo
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Responsabilidades ,Government ,Estructura ,Optimo ,autoridad ,Structure ,Optimal ,Economy ,Gobierno ,authority ,Responsibilities ,Economía - Abstract
El artículo estructura conceptualmente las diferentes formas de gobierno corporativo, principalmente con su respectiva definición, seguido de la interrogante del texto acerca de, si existe una objetiva y excelente forma óptima de un Gobierno Corporativo, su consecuencia en la organización y desempeño de las empresas, conjuntamente de revisarse el resultado de la estructura financiera y corporativa referente el desempeño económico, el modo de conseguir una estructura específica de gobierno corporativo, contiguo a aspectos en los cuales se entiende superior la puesta en marcha y efecto del gobierno corporativo cuando las empresas funcionan en economías emergentes, y finaliza, reflejando como es el Gobierno Corporativo en Chile, existiendo diferencias en el ámbito corporativo entre este y países más desarrollados. The article conceptually structures the different forms of corporate governance, mainly with its respective definition, followed by the question of the text about, if there is an objective and excellent optimal form of Corporate Governance, its consequence in the organization and performance of the companies, together with reviewing the result of the financial and corporate structure regarding economic performance, how to achieve a specific corporate governance structure, adjacent to aspects in which it is understood the start-up and effect of corporate governance superior when companies operate in emerging economies, and ends, reflecting how is the Corporate Governance in Chile, existing differences in the corporate sphere between this and more developed countries. Abogado Pregrado
- Published
- 2021
15. Metodología computacionalmente eficiente para resolver el despacho económico multiperiodo estocástico con restricciones de seguridad
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López Lezama, Jesús María, Sierra Aguilar, Juan Esteban, Marín Cano, Cristian Camilo, Jaramillo Duque, Alvaro, López Lezama, Jesús María, Sierra Aguilar, Juan Esteban, Marín Cano, Cristian Camilo, and Jaramillo Duque, Alvaro
- Abstract
Objective: Validate a computationally efficient approach to solve the stochastic security constraint unit commitment problem. Methodology: Linear sensitivity factors are used to compute power flows in a fast and accurate way. It is also used an iterative method that identifies and adds as user cuts the set of active constraints. These constraints establish the feasible region of a model embedded within a Progressive Hedging algorithm, which decomposes the main problem into a set of computationally more tractable sub-problems by relaxing the coupling constraints between scenarios. Results: The numerical results on the IEEE RTS96 system show that the proposed strategy provides high quality solutions with low calculation times. Conclusions: The proposed methodology allows the stochastic security-constraint unit commitment problem to be solved up to 50 times faster when compared to its extensive formulation., Objetivo: Validar una metodología computacionalmente eficiente para resolver el problema de despacho económico multiperiodo estocástico con restricciones de seguridad. Metodología: Se utilizan factores lineales de sensibilidad para calcular flujos de carga de forma rápida y precisa. También se usa un método iterativo, que identifica y agrega como cortes de usuario, las restricciones de seguridad activas. Estas restricciones establecen la región factible de un modelo embebido dentro de un algoritmo Progressive Hedging, el cual descompone el problema principal en un conjunto de sub-problemas computacionalmente más tratables, al relajar las restricciones de acoplamiento entre escenarios. Resultados: Los resultados numéricos sobre el sistema IEEE RTS96, muestran que la estrategia propuesta entrega soluciones de alta calidad en bajos tiempos de cálculo. Conclusiones: La metodología propuesta permite solucionar el despacho económico multiperiodo estocástico seguro hasta 50 veces más rápido cuando se compara con su formulación extensiva.
- Published
- 2021
16. A New Affinely Adjustable Robust Model for Security Constrained Unit Commitment under Uncertainty
- Author
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Sierra-Aguilar, Juan Esteban, primary, Marín-Cano, Cristian Camilo, additional, López-Lezama, Jesús M., additional, Jaramillo-Duque, Álvaro, additional, and Villegas, Juan G., additional
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- 2021
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17. Security-Constrained unit commitment using PTDF and LODF sensibility factors
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Marin, Cristian Camilo, López Lezama, Jesús María, Sierra Aguilar, Juan Esteban, Jaramillo Duque, Alvaro, Marin, Cristian Camilo, López Lezama, Jesús María, Sierra Aguilar, Juan Esteban, and Jaramillo Duque, Alvaro
- Abstract
The unit commitment (UC) problem consists in optimally determining which generation units must supply power to the system in a typical time horizon of 24 hours. The security- constrained unit commitment (SCUC) is a problem of high computational cost due to the quantity and nature of the variables involved. This paper presents an alternative formulation of the SCUC to reduce its computational cost, by using the PTDF and LODF sensitivity factors. In contrast to classic formulations, the use of these factors allows calculating power flows without using nodal angles, reducing the number of variables and constraints of the model. In addition, an N-1 active contingency filter methodology is implemented that further reduces the computational burden through user cuts. Results are presented for the IEEE-RTS96 system that demonstrates the robustness and applicability of the proposed approach. It was found that the use of PTDF and LODF sensitivity factors, in conjunction with the contingency filter methodology, reduces the computational cost by up to 86% with respect to its conventional formulation. Additionally, the proposed methodology identifies which lines are more vulnerable due to overloads, and which lines cause the greatest impacts to the system when they fail., El problema de despacho económico multiperiodo (DEM) consiste en determinar de manera óptima que unidades de generación deben suministrar potencia al sistema en un horizonte de tiempo típico de 24 horas. El DEM con restricciones de seguridad (SCUC por sus siglas en inglés) es un problema de alto costo computacional debido a la cantidad y naturaleza de las variables involucradas. En este artículo se presenta una formulación alternativa del SCUC para reducir su costo computacional, mediante el uso de los factores de sensibilidad PTDF y LODF. En contraste con las formulaciones clásicas, el uso de estos factores permite calcular flujos de carga sin necesidad de utilizar los ángulos nodales, reduciendo el número de variables y restricciones del modelo. Además, se implementa una metodología de filtro de contingencias activas N-1 que reduce aún más la carga computacional, a través de cortes de usuario. Se presentan resultados para el sistema IEEE-RTS96 que evidencian la robustez y aplicabilidad del modelo propuesto. Se encontró que el uso de los factores de sensibilidad PTDF y LODF, en conjunto con la metodología de filtros de contingencias, reduce el costo computacional hasta en un 86% con respecto a su formulación convencional. Adicionalmente, la metodología propuesta identifica que líneas son más vulnerables debido a sobrecargas, y cuales líneas causan mayores impactos al sistema cuando fallan.
- Published
- 2020
18. Despacho Económico Multiperiodo con Restricciones de Seguridad Usando los Factores de Sensibilidad PTDF y LODF
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Marín Cano, Cristian Camilo, López Lezama, Jesús María, Sierra Aguilar, Juan Esteban, Jaramillo Duque, Alvaro, Marín Cano, Cristian Camilo, López Lezama, Jesús María, Sierra Aguilar, Juan Esteban, and Jaramillo Duque, Alvaro
- Abstract
El problema de despacho económico multiperiodo (DEM) consiste en determinar de manera óptima que unidades de generación deben suministrar potencia al sistema en un horizonte de tiempo típico de 24 horas. El DEM con restricciones de seguridad (SCUC por sus siglas en inglés) es un problema de alto costo computacional debido a la cantidad y naturaleza de las variables involucradas. En este artículo se presenta una formulación alternativa del SCUC para reducir su costo computacional, mediante el uso de los factores de sensibilidad PTDF y LODF. En contraste con las formulaciones clásicas, el uso de estos factores permite calcular flujos de carga sin necesidad de utilizar los ángulos nodales, reduciendo el número de variables y restricciones del modelo. Además, se implementa una metodología de filtro de contingencias activas N-1 que reduce aún más la carga computacional, a través de cortes de usuario. Se presentan resultados para el sistema IEEE-RTS96 que evidencian la robustez y aplicabilidad del modelo propuesto. Se encontró que el uso de los factores de sensibilidad PTDF y LODF, en conjunto con la metodología de filtros de contingencias, reduce el costo computacional hasta en un 86% con respecto a su formulación convencional. Adicionalmente, la metodología propuesta identifica que líneas son más vulnerables debido a sobrecargas, y cuales líneas causan mayores impactos al sistema cuando fallan., The unit commitment (UC)problemconsists in optimally determining which generation units must supply power to the system in a typical time horizon of 24 hours. The security-constrained unit commitment (SCUC) is a problem of high computational cost due to the quantity and nature of the variables involved. This paper presents an alternative formulation of the SCUC to reduce its computational cost, by using the PTDF and LODF sensitivity factors. In contrast toclassic formulations, the use of these factors allows calculating powerflows without using nodal angles, reducing the number of variables and constraints of the model. In addition, an N-1 active contingency filter methodology is implemented that further reduces the computational burden through user cuts. Results are presented for theIEEE-RTS96 system that demonstrates the robustness and applicability of the proposed approach. It was found that the use of PTDF and LODF sensitivity factors, in conjunction with the contingency filter methodology, reduces the computational cost by up to 86% with respect to its conventional formulation. Additionally, the proposed methodology identifies which lines are more vulnerable due to overloads, and which lines cause the greatest impacts to the system when they fail.
- Published
- 2020
19. Despacho económico multiperiodo con restricciones de seguridad usando los factores de sensibilidad PTDF y LODF
- Author
-
Marin, Cristian Camilo, primary, López Lezama, Jesús María, primary, Sierra Aguilar, Juan Esteban, primary, and Jaramillo Duque, Alvaro, primary
- Published
- 2020
- Full Text
- View/download PDF
20. A Novel Strategy to Reduce Computational Burden of the Stochastic Security Constrained Unit Commitment Problem
- Author
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Marín-Cano, Cristian Camilo, primary, Sierra-Aguilar, Juan Esteban, additional, López-Lezama, Jesús M., additional, Jaramillo-Duque, Álvaro, additional, and Villegas, Juan G., additional
- Published
- 2020
- Full Text
- View/download PDF
21. Producción de enzimas ligninolíticas por basidiomicetes incubados en rastrojo de maíz y análisis de la biomasa resultante como alimento en rumiantes
- Author
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Yveet Sierra Aguilar, José Herrera Camacho, and Gerardo Vázquez Marrufo
- Subjects
Esquilmo agrícola ,6 [cti] ,Enzimas ligninolíticas ,Pretratamiento ,IIAF-M-2018-1196 - Abstract
Instituto de Investigaciones Agropecuarias y Forestales. Facultad de Biología. Facultad de Medicina Veterinaria y Zootecnia. Facultad de Agrobiología. Facultad de Químico Farmacobiología. Programa Institucional de Maestría en Ciencias Biológicas Extracellular Laccase (Lac) and Manganese (MnP) enzyme production was evaluated from the strain of basidiomycetes: Trametes versicolor, Irpex lacteus, Ganoderma sp. and Phlebiopsis sp, they were inoculated in corn stover (Zea mays L.), in liquid medium (ML) and solid-state fermentation (SSF) assay. Chemical changes on the cell wall after fungal corn stover preteatment were quantified and their performan in vitro for ruminal feed aplications. The activity of Lac and MnP was significantly lower in FSS assays. Maximum Lac and MnP production was detected on T. versicolor, folded 27.79 and 32 times respective (P?0.05). I. lacteus and Phlebiopsis sp. did not show Lac activity. There was changes in cell wall in both mediums. Ganoderma sp. caused the higher delignification with 2.29%. There was a lost from 10 to 20% of non-structural carbohydrates. The resulting biomass was subjected to ruminal fermentation by the gas production in vitro technique, decrease the true digestibility 54% in corn stover with I. lacteus, increasted the methane production compared with control (P?0.05). The results show that corn stover induces activity of Lac and MnP. Also there are a lost of non-structural carbohydrates, decreasing their nutritional quality, according to the ruminal fermentation values in vitro. It is not reject that subsequent studies with modified incubation conditions in order to optimize the delignification of the corn sover by the strains of the study, increase the nutritional value of corn stover for feeding of ruminants. Se analizó la inducción enzimática extracelular de lacasa (Lac) y manganeso peroxidasa (MnP) de los basidiomicetes: Trametes versicolor, Irpex lacteus, Ganoderma sp. y Phlebiopsis sp. inoculados en rastrojo de maíz (Zea mays L.), en medio líquido (ML) y sólido (FSS). Cuantificando los cambios químicos de la pared celular del pretratamiento resultante y su desempeño in vitro como alimento para rumiantes. La producción de enzimas fue mayor en ML en comparación al FSS. La mayor producción de Lac y MnP la tuvo T. versicolor, aumentando su producción 27 y 34 veces respectivamente (P?0.05). I lacteus y Phlebiopsis sp. no presentaron actividad de Lac. Hubo cambios en la pared celular en ambos medios de cultivo. En SSF la mayor pérdida de lignina fue con Ganoderma sp. en 2.29 %. Disminuyó la cantidad de carbohidratos no estructurales en el rastrojo inoculado con las cepas de 10 a 20%. La biomasa resultante se sometió a fermentación ruminal por la técnica de producción de gas in vitro, donde disminuyo la digestibilidad verdadera 54% en el rastrojo tratado con I. lacteus, aumentando la producción de metano comparado con el control (P?0.05). Lo anterior muestra que el rastrojo de maíz induce la actividad enzimática de Lac y MnP. Debido a la perdida de carbohidratos no estructurales, la biomasa resultante es de poco valor nutricional de acuerdo a los valores de fermentación in vitro para los rumiantes. No se descarta que en estudios posteriores, modificando las condiciones de cultivo y con las cepas de hongos aquí empleadas, incrementen el valor nutricional del rastrojo de maíz para su uso en la alimentación de rumiantes.
- Published
- 2018
22. Hernia de Bochdalek: A Challenging Diagnosis
- Author
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Sierra-Aguilar S Ivana, Mejia-Martinez Lessdy Aarely, Campos-Sanchez Eduardo Jose, Juan Francisco Ayestas, and Avila-De La Puente Claudia
- Subjects
medicine.medical_specialty ,business.industry ,Thoracic cavity ,medicine.medical_treatment ,Diaphragmatic breathing ,Abdominal cavity ,medicine.disease ,Hypochondrium ,Surgery ,Bochdalek hernia ,medicine.anatomical_structure ,Laparotomy ,Medicine ,Diaphragmatic hernia ,Hernia ,business - Abstract
Diaphragmatic hernias are defined as a transposition of abdominal organs into the thoracic cavity through a defect in the phrenic muscle. They can be classified as congenital, acquired, or post traumatic. The Bochdalek hernia is congenital, it is produced by an alteration in the embryological development of the diaphragm, causing a zone of anatomical weakness that allows the protrusion of intraabdominal organs into the thoracic cavity. The prevalence of the Bochdalek hernia is 1 in 2,200 births and is located on the left side 80%-90% of the time, only 5%-10% remain undetectable during childhood. Less than 100 cases have been reported in adults. In Honduras there have been few cases reported in pediatrics, and none in adults. We present the case of a 38-year-old patient that seeks at the Hospital Escuela Universitario in Tegucigalpa, Honduras, due to abdominal pain located in the left iliac fosse that irradiates to the right flank and hypochondrium over the past two months, accompanied by dyspnea and paroxistic episodes of cough. At thoracic auscultation wheezing was found with predominance in the left lung, with hypoventilation and the presence of intestinal sounds. A thoracoabdominal tomography with contrast was performed, finding the presence of a diaphragmatic hernia occupying the whole left hemithorax, including the spleen, colon and stomach. The data is corroborated by a diagnostic laparoscopy, but because the organs could not be reduced to the abdominal cavity a laparotomy was performed. The findings correspond to the organs that are commonly herniated in the left Bochdalek hernia. After the laparotomy the patient had a satisfying progress, with subsequent hospital discharge. It is important to have a timely diagnosis and adequate treatment for this type of hernia to prevent complications that could compromise the life of the patient.
- Published
- 2018
23. Dimensionando la calidad de vida de las personas con Alzheimer. Una propuesta de aplicación
- Author
-
Sierra Aguilar, Sara, Lucas García, Jezabel Amparo, and Universidad de Valladolid. Facultad de Educación y Trabajo Social
- Subjects
Demencia ,FUMAT ,Alzheimer, Enfermedad de ,Escalas de calidad de vida - Abstract
Un estudio de la calidad de vida de las personas que padecen la enfermedad de Alzheimer, y a su vez son usuarias de un centro diurno especializado de los servicios sociales, permitirá establecer las bases para el desarrollo de una correcta adecuación de las intervenciones que en él se realicen. Por ello se plantea el uso de instrumentos de medida de la calidad de vida, que puedan ser aplicados en un contexto complejo como es el compuesto por las personas que padecen Alzheimer. Una vez formulada la escala FUMAT como instrumento cuya viabilidad en el contexto es aprobada por las características que presenta, se ha realizado una propuesta de modificación de dicho instrumento que posteriormente se ha analizado con el objetivo de obtener una mayor aproximación a la calidad de vida que estos usuarios y usuarias presentan., Departamento de Sociología y Trabajo Social, Máster en Psicopedagogía
- Published
- 2018
24. Implementation of User Cuts and Linear Sensitivity Factors to Improve the Computational Performance of the Security-Constrained Unit Commitment Problem
- Author
-
Marín-Cano, Cristian Camilo, primary, Sierra-Aguilar, Juan Esteban, additional, López-Lezama, Jesús M., additional, Jaramillo-Duque, Álvaro, additional, and Villa-Acevedo, Walter M., additional
- Published
- 2019
- Full Text
- View/download PDF
25. Study of feasibility and feasibility of the organic urban house in the balconies of the Tangara II set, in the locality of Bosa of the city of Bogotá
- Author
-
Sierra Aguilar, Erika Marcela and Roa Rodríguez, Guillermo
- Subjects
Balcones ,Tamaño de proyecto ,CULTIVOS HORTICOLAS ,Localidad de Bosa ,Huerta ,Technical study ,Proyect size ,Market study ,Working capital ,Presupuesto ,Rentabilidad ,ESTUDIOS DE FACTIBILIDAD ,Tangara II residential complex ,Capital de trabajo ,Break even point ,Punto de equilibrio ,Balconies ,Estudio tecnico ,Garden ,Estudio de mercado ,Budget ,Profitability ,ADMINISTRACION DE PROYECTOS ,Conjunto Tangara II - Abstract
25 páginas : gráficos, tablas. El presente proyecto identifica toda el ciclo de pre-inversión en la creación de una huerta urbanística orgánica en los balcones del conjunto residencial Tangara II ubicado en la localidad de Bosa en la ciudad de Bogotá, se inicia con el estudio de mercado, el cual permite recolectar analizar y procesar los datos e identificar las variables que definieron la aceptación del producto, se cuantifica la demanda. Se procede con las especificaciones técnicas y poder determinar la capacidad instalada y los requerimientos que necesitan en la realización de la huerto, se realiza el costeo de los suministros, equipos que se requieren para colar en marcha la idea, la última etapa es análisis financiero donde se tiene en cuenta los rubros de inversión, capital de trabajo, precio de venta y el presupuesto de ventas. Con la información obtenida se elaboran el estado de pérdidas y ganancia, se determina el punto equilibrio y la rentabilidad, se concluye que el proyecto es viable y factible. The present proyect identifies the entire pre-investment cycle in the creation of an organic urban garden in the balconies of the residential complex Tangara II, located in locality of Bosa in Bogotá city. It iniciates with the market study, which allows to collect, analyse and process the data and identify the variables that defined the product’s acceptance, then the demand is quantified. Later we proceed with the technical specifications to be able to determine the instaled capacity and the necessary requirements for the realization of the garden. The cost of the equipment and supplies is carried out to start the idea. The last stage is the financial analysis where the investment items, working capital, sales price and sales budget are taken into account. With the obtained information the profit and loss statement is elaborated, the profitability and break-even point are determined and finally it is concluded that the proyect is viable and feasible.
- Published
- 2017
26. Hernia de Bochdalek diagnosticada en la edad adulta: Reporte de caso
- Author
-
Campos Sánchez, EJ, Mejia Martínez, Lessdy Aarely, Sierra Aguilar, SI, Ayestas, Juan Francisco, Ávila De la Puente, Claudia, Campos Sánchez, EJ, Mejia Martínez, Lessdy Aarely, Sierra Aguilar, SI, Ayestas, Juan Francisco, and Ávila De la Puente, Claudia
- Abstract
Diaphragmatic hernias are defined as a transposition of abdominal organs into the thoracic cavity through a defect in the phrenic muscle. They can be classified as congenital, acquired, or post traumatic. The Bochdalek hernia is congenital, it is produced by an alteration in the embryological development of the diaphragm, causing a zone of anatomical weakness that allows the protrusion of intraabdominal organs into the thoracic cavity. The prevalence of the Bochdalek hernia is 1 in 2,200 births and is located on the left side 80-90% of the time, only 5-10% remain undetectable during childhood. Less than 100 cases have been reported in adults. In Honduras there have been few cases reported in pediatrics, and none in adults. We present the case a 38 year old patient that seeks the surgery emergency room at Hospital Escuela Universitario in Tegucigalpa, Honduras, due to abdominal pain located in the left iliac fosse that irradiates to the right flank and hypochondrium over the past two months, accompanied by dyspnea and paroxistic episodes of cough. At the thoracic auscultation wheezing was found with predominance in the left lung, with hypoventilation and the presence of intestinal sounds. A thoracoabdominal tomography with contrast is performed, finding the presence of a diaphragmatic hernia occupying the whole left hemithorax, including the spleen, colon and stomach. The data is corroborated by a diagnostic laparoscopy, but because the organs could not be reduced to the abdominal cavity a laparotomy was performed. The findings correspond to the organs that are commonly herniated in the left Bochdalek hernia. After the laparotomy the patient had a satisfying progress, with subsequent hospital discharge. It is important to have a timely diagnosis and adequate treatment for this type of hernia to prevent complications that could compromise the life of the patient., Las hernias diafragmáticas se definen como la transposición de órganos abdominales a la caja torácica, a través de defectos del músculo frénico. Pueden clasificarse como congénitas, adquiridas o post traumáticas. La hernia de Bochdalek es congénita, se produce por una alteración en el desarrollo embriológico del diafragma, causando una zona de debilidad anatómica que permite la protrusión de órganos intra-abdominales hacia la caja torácica. La prevalencia de la hernia de Bochdalek es de 1 en 2,200 nacimientos y se ubica en el lado izquierdo en un 80- 90%, solo el 5-10% permanece indetectable en la niñez. Menos de 100 casos han sido reportados en adultos. En Honduras hay pocos casos reportados en pediatría y ningún caso reportado en adultos. Presentamos el caso de una paciente de 38 años que acude a la emergencia de cirugía del Hospital Escuela Universitario en Tegucigalpa, Honduras, por dolor abdominal de dos meses de evolución en fosa iliaca izquierda irradiado a flanco e hipocondrio derecho, acompañado de disnea y episodios paroxísticos de tos. A la auscultación torácica se encuentran sibilancias de predominio pulmonar izquierdo, con hipoventilación y presencia de ruidos intestinales. Se realiza una tomografía toracoabdominal con medio de contraste, encontrando la presencia de una hernia diafragmática que ocupa la totalidad del hemitórax izquierdo con inclusión de bazo, colon y estómago. Los datos se corroboran mediante laparoscopia diagnostica y al no poder reducir los órganos a la cavidad abdominal se procede a realizar una laparotomía. Los hallazgos concuerdan con los órganos que comúnmente se hernian en la hernia de Bochdalek izquierda. Después de la laparotomía la paciente presenta una evolución satisfactoria, con posterior egreso hospitalario. Es importante el diagnóstico oportuno y tratamiento adecuado de este tipo de hernia para prevenir complicaciones que puedan poner en riesgo la vida del paciente.
- Published
- 2018
27. Security-Constrained Unit Commitment using PTDF and LODF Sensibility Factors.
- Author
-
Marín, C. C., Sierra-Aguilar, J. E., Jaramillo-Duque, Á., and López-Lezama, J. M.
- Subjects
- *
TIME perspective , *POWER resources - Abstract
The unit commitment (UC) problem consists in optimally determining which generation units must supply power to the system in a typical time horizon of 24 hours. The securityconstrained unit commitment (SCUC) is a problem of high computational cost due to the quantity and nature of the variables involved. This paper presents an alternative formulation of the SCUC to reduce its computational cost, by using the PTDF and LODF sensitivity factors. In contrast to classic formulations, the use of these factors allows calculating power flows without using nodal angles, reducing the number of variables and constraints of the model. In addition, an N-1 active contingency filter methodology is implemented that further reduces the computational burden through user cuts. Results are presented for the IEEE-RTS96 system that demonstrates the robustness and applicability of the proposed approach. It was found that the use of PTDF and LODF sensitivity factors, in conjunction with the contingency filter methodology, reduces the computational cost by up to 86% with respect to its conventional formulation. Additionally, the proposed methodology identifies which lines are more vulnerable due to overloads, and which lines cause the greatest impacts to the system when they fail. [ABSTRACT FROM AUTHOR]
- Published
- 2020
28. Hernia de Bochdalek: A Challenging Diagnosis
- Author
-
Eduardo Jose, Campos-Sanchez, primary, Lessdy Aarely, Mejia-Martinez, additional, Ivana, Sierra-Aguilar S, additional, Puente Claudia, Avila-De La, additional, and Ayestas, Juan Francisco, additional
- Published
- 2018
- Full Text
- View/download PDF
29. Unified method for teaching how to solve the equivalent circuit of transformers.
- Author
-
ORTIZ-CASTRILLÓN, José R., JARAMILLO-DUQUE, Álvaro, MUÑOZ-GALEANO, Nicolás, SIERRA-AGUILAR, Juan E., and LOPEZ-LEZAMA, Jesús M.
- Subjects
ELECTRIC transformers ,TEACHING ,ECONOMIC decision making ,PYTHON programming language ,COMPUTER simulation - Abstract
Copyright of Revista Espacios is the property of Talleres de Impresos Oma and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
30. Propuesta educativa para la promoción del desarrollo humano y la prevención de problemas psicosociales en los colegios, Institución Educativa Empresarial y Agroindustrial los Andes ´Inseandes´ Institución Educativa Silvestre Arenas, Colegio Técnico en Administración Microempresarial cuidad del sol mediante habilidades para la vida
- Author
-
Sierra Aguilar, Claudia Patricia and Avendaño Zorro, Luz Miryam
- Subjects
Educación media ,Sustancias psicoactivas ,Desarrollo físico y mental ,Embarazo en adolecentes ,Resiliencia ,Influencias sociales ,Adolescentes ,Conflicto generacional ,Bienestar personal y social ,Ambientes escolares - Abstract
Imágenes, Tablas y Gráficas El objetivo del presente proyecto fue fortalecer las habilidades para la vida de los estudiantes de los colegios de Sogamoso mediante el acompañamiento psicosocial que les permita actuar asertivamente a las influencias sociales, ambientales e individuales de cada contexto. Basados en desarrollo y conocimiento de habilidades para la vida para promover un desarrollo físico y mental saludable. Se realizó la aplicación del test de Resiliencia para jóvenes de 13 a 17 años de Wagnild & Young. Los resultados de ese estudio señalan la importancia de la adquisición y fortalecimiento de habilidades para la vida para un buen bienestar personal y social. Palabras claves: habilidades para la vida, prevención, promoción, resiliencia, niños, niñas, adolescentes. This resecar Project alims to strengthen the students´abilities from the Sogamoso city schools.It was carried out through a psychosocial support base don encourage a physical and mentaldevelopment in students in orden that admit in a positive way the social, environmental and individual influences of each context. A resiliencia test was appied to student between 13 to 17 years odl from Wagnild & Young.the findings revealed that the acquisition of abilities allow a good personal and social welfare. Key Word: life, habilites, preventios, promotion, resilience, teenagers, children.
- Published
- 2014
31. Uso de productos derivados en los portafolios de inversión de las SIEFORES
- Author
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Sierra Aguilar, Miriam Xóchitl and Morales Castro, Jóse Antonio
- Subjects
Ciencias Sociales - Published
- 2013
32. Alternativas de aprovechamiento de la cascarilla de arroz en Colombia
- Author
-
Sierra Aguilar, Jaider
- Subjects
Cascarilla de Arroz Como Fuente de Energía ,Energía Biomasica ,Recursos Energéticos - Abstract
Crear conciencia del uso racional de los recursos naturales por parte de los seres humanos es un compromiso que ha trascendido las fronteras nacionales para convertirse en una causa global. Uno de los mecanismos a la mano es el uso de los subproductos de los procesos industriales o agroindustriales de los cuales se generan una serie de residuos que en cierto grado se pueden aprovechar y con ello se apunta a mejorar dos condiciones, una de ellas es el manejo de las basuras y otra, qué al aprovecharlos oportunamente se disminuye el uso de recursos energéticos tales como el petróleo, la madera, que cada día incrementan sus costos y tienden a escasearse. Con la realización de esta monografía, centramos la atención en la cascarilla de arroz como alternativa de uso en niveles energéticos y constructivos dada sus características de aislante térmico, combustible alternativo entre otras posibilidades .Se hace referencia así a todos las aproximaciones tecnológicas e investigativas a nivel de Latinoamérica y Colombia y la contribución de las mismas a la problemática generada por el destino final de dicho subproducto., Vergara Garay Carlos, Pregrado, Ingeniero(a) Agrícola
- Published
- 2009
33. Unified method for teaching how to solve the equivalent circuit of transformers
- Author
-
Ortiz-Castrillón, J. R., Jaramillo-Duque, Á, Nicolás Muñoz-Galeano, Sierra-Aguilar, J. E., and Lopez-Lezama, J. M.
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