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Sample records for ciclos brayton totalmente

  1. Back work ratio of Brayton cycle; La relacion de trabajo de retroceso de un ciclo Brayton

    Energy Technology Data Exchange (ETDEWEB)

    Malaver de la Fuente, M. [Universidad Maritima del Caribe (Venezuela)]. E-mail: mmf_umc@hotmail.com

    2010-07-15

    This paper analyzes the existing relation between temperatures, back work ratio and net work of Brayton cycle, a cycle that describes gas turbine engines performance. The application of computational software helps to show the influence of back work ratio or coupling ratio, compressor and turbine inlet temperatures in an ideal thermodynamical cycle. The results lead to deduce that the maximum value reached in back work ratio will depend on the ranges of maximum and minimal temperatures of Brayton cycle. [Spanish] En este articulo se estudia la relacion que existe entre las temperaturas, la relacion de trabajo de retroceso y el trabajo neto en el ciclo Brayton, que es el ciclo ideal que describe el comportamiento de los motores de turbina de gas. La aplicacion de programas computarizados ayuda a mostrar la influencia de la relacion de trabajo de retroceso o relacion de acoplamiento, la temperatura de entrada al compresor y la temperatura de entrada a la turbina en este ciclo termodinamico ideal. Los resultados obtenidos permiten deducir que el valor maximo que alcanza la relacion de trabajo de retroceso dependera de los limites de temperatura maxima y minima impuestos en el ciclo Brayton.

  2. Tres lecciones en combinatoria algebraica. I. Matrices totalmente no negativas y funciones sim\\'etricas

    OpenAIRE

    Ardila, Federico; Leon, Emerson; Rosas, Mercedes; Skandera, Mark

    2013-01-01

    En esta serie de tres articulos, damos una exposicion de varios resultados y problemas abiertos en tres areas de la combinatoria algebraica y geometrica: las matrices totalmente no negativas, las representaciones del grupo simetrico, y los arreglos de hiperplanos. Esta primera parte presenta una introduccion a las matrices totalmente no negativas, y su relacion con las funciones simetricas. In this series of three articles, we give an exposition of various results and open problems in three a...

  3. Sistema experto aplicado a la enseñanza de ciclos termodinámicos

    OpenAIRE

    Beraudo, Vanina; Gago, Luis Alberto; Echeverria, Martín H.; Stark, Natalia

    2007-01-01

    El presente artículo trata la aplicación de un sistema experto capaz de determinar la factibilidad de funcionamiento de una máquina térmica desde el punto de vista termodinámico, mediante el análisis del diseño de un ciclo de potencia, el ciclo Joule Brayton; y ofrecer a estudiantes de Termodinámica, en especial, una herramienta innovadora que les permita aprender principios fundamentales del dominio, en base tanto a sus aciertos como a sus errores, detectando diseños físicamente imposibles y...

  4. Examination of the performance of an unconventional combination of Rankine, Brayton, and Inverse Brayton cycles

    Energy Technology Data Exchange (ETDEWEB)

    Alabdoadaim, M.; Agnew, B.; Potts, I. [University of Newcastle-upon-Tyne (United Kingdom). School of Mechanics and Systems Engineering

    2006-07-01

    The study presented in this article examined the thermodynamic performance of a proposed system constructed from Brayton, inverse Brayton, and steam Rankine cycles. The theoretical examination was performed by varying the Brayton cycle pressure ratio for different values of inlet pressure and expansion pressures of the inverse Brayton cycle and for different ratios of the inverse Brayton power turbine mass flow to the gas generator mass flow. The results indicated that for the three values of mass flow ratio examined, better performance could be achieved when the proposed system is operated at high Brayton cycle pressure ratio (high maximum system temperature and the highest value of inverse Brayton cycle expansion pressure). It was revealed that in the case of the mass flow equal to 0.25, the proposed system achieved the highest value of Brayton cycle pressure ratio and attained a maximum thermal efficiency of 57.7 per cent. (author)

  5. A hybrid Brayton engine concept

    Science.gov (United States)

    Six, L. D.; Elkins, R.

    1980-01-01

    A first generation open cycle Brayton engine concept for use in full scale solar module testing was defined. The concept extended to include solar/fossil hybrid capability. The combustion system defined for hybrid operation consists of a wide range combustor liner, a single airblast atomizer, an ignitor and a high-voltage ignition unit. Wide range combustor operation would be achieved through combining pilot and primary zones. The hybrid control mode and the solar only control mode are both based on the concept of maintaining constant turbine inlet temperature and varying the engine speed for part-power operation. In addition, the hybrid control concept will allow the operator to set a minimum thermal power input to the engine by setting a corresponding minimum engine speed. When the solar thermal power input falls below this minimum, fossil fuel would be utilized to augment the solar thermal power input.

  6. Back Work Ratio of Brayton Cycle

    Directory of Open Access Journals (Sweden)

    Malaver de la Fuente M.

    2010-07-01

    Full Text Available This paper analizes the existing relation between temperatures, back work ratio and net work of Brayton cycle, a cycle that describes gas turbine engines performance. The application of computational soft ware helps to show the influence of back work ratio or coupling ratio, compressor and turbine in let temperatures in an ideal thermodynamical cycle. The results lead to deduce that the maximum value reached in back work ratio will depend on the ranges of maximum and minimal temperatures of Brayton cycle.

  7. On Brayton and Moser's missing stability theorem

    NARCIS (Netherlands)

    Jeltsema, D.; Scherpen, J. M. A.

    2005-01-01

    In the early 1960s, Brayton and Moser proved three theorems concerning the stability of nonlinear electrical circuits. The applicability of each theorem depends on three different conditions on the type of admissible nonlinearities in circuit. Roughly speaking, this means that the theorems apply to

  8. Brayton Isotope Power System (BIPS) facility specification

    Energy Technology Data Exchange (ETDEWEB)

    1976-05-31

    General requirements for the Brayton Isotope Power System (BIPS)/Ground Demonstration System (GDS) assembly and test facility are defined. The facility will include provisions for a complete test laboratory for GDS checkout, performance, and endurance testing, and a contamination-controlled area for assembly, fabrication, storage, and storage preparation of GDS components. Specifications, schedules, and drawings are included.

  9. Brayton Isotope Power System (BIPS) facility specification

    International Nuclear Information System (INIS)

    General requirements for the Brayton Isotope Power System (BIPS)/Ground Demonstration System (GDS) assembly and test facility are defined. The facility will include provisions for a complete test laboratory for GDS checkout, performance, and endurance testing, and a contamination-controlled area for assembly, fabrication, storage, and storage preparation of GDS components. Specifications, schedules, and drawings are included

  10. Binary Brayton cycle with two isothermal processes

    International Nuclear Information System (INIS)

    Highlights: • This paper presents binary Brayton cycle with two isothermal processes. • Different parameters affecting the cycle performance have been studied. • The present cycle is a promising cycle for future power generation. - Abstract: The literature introduced isothermal concept and binary Brayton cycle as two promising methods used to enhance the performance of the gas turbine. Consequently, this work presents a cycle based on the blending of the two methods. This cycle is composed of gas turbine topping cycle with isothermal combustion and air turbine bottoming cycle with isothermal heating. Different parameters affecting the cycle performance have been studied. Simulations demonstrate that the present cycle achieves drastic enhancement in performance. The cycle merits justify its potential utilization for future power generation

  11. Brayton heat exchange unit development program

    Science.gov (United States)

    Morse, C. J.; Richard, C. E.; Duncan, J. D.

    1971-01-01

    A Brayton Heat Exchanger Unit (BHXU), consisting of a recuperator, a heat sink heat exchanger and a gas ducting system, was designed, fabricated, and tested. The design was formulated to provide a high performance unit suitable for use in a long-life Brayton-cycle powerplant. A parametric analysis and design study was performed to establish the optimum component configurations to achieve low weight and size and high reliability, while meeting the requirements of high effectiveness and low pressure drop. Layout studies and detailed mechanical and structural design were performed to obtain a flight-type packaging arrangement. Evaluation testing was conducted from which it is estimated that near-design performance can be expected with the use of He-Xe as the working fluid.

  12. Teresa Brayton: In an Irish Twilight

    OpenAIRE

    Morrin, Ms. Olive

    2002-01-01

    Teresa Brayton, poet, literary nationalist, author of "The Old Bog Road" was born in Kilbrook, Kilcock in 1868. She emigrated to America in 1895 and became well known in Irish-American circles. She published extensively in many American newspapers and magazines and was closely associated with the 1916 Rising. In 1913 she published her first book of poetry called "Songs of the Dawn, The Flame of Ireland" appeared in 1926 and "Christmas Verses" in 1934. Her main themes were the exile's nost...

  13. Quantum Brayton cycle with coupled systems as working substance

    Science.gov (United States)

    Huang, X. L.; Wang, L. C.; Yi, X. X.

    2013-01-01

    We explore the quantum version of the Brayton cycle with a composite system as the working substance. The actual Brayton cycle consists of two adiabatic and two isobaric processes. Two pressures can be defined in our isobaric process; one corresponds to the external magnetic field (characterized by Fx) exerted on the system, while the other corresponds to the coupling constant between the subsystems (characterized by Fy). As a consequence, we can define two types of quantum Brayton cycle for the composite system. We find that the subsystem experiences a quantum Brayton cycle in one quantum Brayton cycle (characterized by Fx), whereas the subsystem's cycle is quantum Otto cycle in another Brayton cycle (characterized by Fy). The efficiency for the composite system equals to that for the subsystem in both cases, but the work done by the total system is usually larger than the sum of the work done by the two subsystems. The other interesting finding is that for the cycle characterized by Fy, the subsystem can be a refrigerator, while the total system is a heat engine. The result in this paper can be generalized to a quantum Brayton cycle with a general coupled system as the working substance.

  14. Analisis termodinamico de los ciclos de rankine

    OpenAIRE

    Fuste Paredes, Sergi

    2015-01-01

    Este proyecto final de grado tiene como objetivo general el estudio y análisis termodinámico del ciclo de Rankine y sus modificaciones. Pretende dar un enfoque general de los distintos parámetros que intervienen y afectan en el aumento del rendimiento de las instalaciones que trabajen con él, así como de las variaciones del ciclo de Rankine para instalaciones de gran potencia, como son el ciclo Rankine con recalentamiento y el ciclo regenerativo de Rankine. En definitiva, la finalidad de este...

  15. Multi-objective optimization of combined Brayton and inverse Brayton cycles using advanced optimization algorithms

    Science.gov (United States)

    Venkata Rao, R.; Patel, Vivek

    2012-08-01

    This study explores the use of teaching-learning-based optimization (TLBO) and artificial bee colony (ABC) algorithms for determining the optimum operating conditions of combined Brayton and inverse Brayton cycles. Maximization of thermal efficiency and specific work of the system are considered as the objective functions and are treated simultaneously for multi-objective optimization. Upper cycle pressure ratio and bottom cycle expansion pressure of the system are considered as design variables for the multi-objective optimization. An application example is presented to demonstrate the effectiveness and accuracy of the proposed algorithms. The results of optimization using the proposed algorithms are validated by comparing with those obtained by using the genetic algorithm (GA) and particle swarm optimization (PSO) on the same example. Improvement in the results is obtained by the proposed algorithms. The results of effect of variation of the algorithm parameters on the convergence and fitness values of the objective functions are reported.

  16. Capitulo XVI. Del ciclo agricola al ciclo vital

    OpenAIRE

    Erikson, Philippe

    2014-01-01

    Figura 63. Figuritas de palmas que representan a las presas de caza Los mariwin, héroes de los capítulos precedentes, se presentan en ellos como aparecidos que mantienen vínculos simbióticos con las últimas plantas comestibles, que crecen en los restos de un sitio de poda: por supuesto, las piñas, pero sobre todo los pijuayos (wani). En otras palabras, se presentaban como metáforas del fin del ciclo vital y agrícola, lo que explicaría que se “vistan” de helechos, plantas vivaces, prontas para...

  17. Alternative analysis to increase the power in combined-cycle power plants; Analisis de alternativas para el incremento de potencia en plantas termoelectricas de Ciclo Combinado

    Energy Technology Data Exchange (ETDEWEB)

    Pacheco Cruz, Hector; Arriola Medellin, Alejandro M. [Gerencia de Procesos Termicos, Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)]. E-mail: hpacheco@iie.org.mx; aarriola@iie.org.mx

    2010-11-15

    The electricity industry traditionally had two thermodynamic cycles for power generation: conventional steam turbine (Rankine cycle) used to supply a base load during the day, and gas turbines (Brayton cycle), for its speed response, normally used to cover peak loads. However, to provide variable peak loads, the gas turbine, as a volumetric machine is affected by the change in air density by changing the combustion temperature. This paper shows the scheme of integration of both systems, that it's known as combined cycle and the different options that would have these power plants, to maintain or increase their power in variable ambient conditions. It analyzes different options, such as: 1. Supplementary fire in the stove. 2. Air cooling intake in the gas turbine (evaporation system or mechanical system). 3. Steam injection in the combustion chamber. [Spanish] La industria electrica tradicionalmente a contado con dos ciclos termodinamicos para generacion electrica: las turbinas convencionales de vapor (ciclo de Rankine) se utilizan para suministrar una carga base durante el dia, y las turbinas de gas (ciclo de Brayton), por su rapidez de respuesta, se utilizan normalmente para cubrir las cargas pico. Sin embargo, para suministrar las cargas variables pico, la turbina a gas, por ser una maquina volumetrica, se ve afectada por el cambio de la densidad del aire de combustion al cambiar la temperatura ambiente. En este trabajo se muestra el esquema de integracion de ambos sistemas, en lo que se conoce como ciclo combinado y las diferentes opciones que tendrian estas plantas de generacion electrica para mantener o incrementar su potencia en condiciones ambiente variable. Para ello se analizan diferentes opciones, tales como: 1.- Combustion suplementaria en el recuperador de calor. 2.- Enfriamiento del aire de admision a la turbina de gas (mediante un sistema de evaporacion o mediante un sistema mecanico). 3.- Inyeccion de vapor a la camara de combustion. Palabras

  18. Vidas precarias y Ciclo Vital

    OpenAIRE

    Salinas, Adán

    2014-01-01

    El artículo propone entender la precariedad en un análisis que sobrepase las condiciones laborales, y que observe la formación de un ciclo vital atravesado por sistemas generales de administración de los medios de subsistencia. Estos sistemas en el contexto neoliberal se han transformado profundamente a través del crédito y la capitalización individual. De modo que el conjunto vital de la población queda precarizado. Se trata entonces de...

  19. Dynamic simulation of a reverse Brayton refrigerator

    Energy Technology Data Exchange (ETDEWEB)

    Peng, N.; Xiong, L. Y.; Dong, B.; Liu, L. Q. [State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, CAS, Beijing, 100190 (China); Lei, L. L.; Tang, J. C. [State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, CAS, Beijing, 100190 China and Graduate University of Chinese Academy of Sciences, Beijing, 100190 (China)

    2014-01-29

    A test refrigerator based on the modified Reverse Brayton cycle has been developed in the Chinese Academy of Sciences recently. To study the behaviors of this test refrigerator, a dynamic simulation has been carried out. The numerical model comprises the typical components of the test refrigerator: compressor, valves, heat exchangers, expander and heater. This simulator is based on the oriented-object approach and each component is represented by a set of differential and algebraic equations. The control system of the test refrigerator is also simulated, which can be used to optimize the control strategies. This paper describes all the models and shows the simulation results. Comparisons between simulation results and experimental data are also presented. Experimental validation on the test refrigerator gives satisfactory results.

  20. Dynamic simulation of a reverse Brayton refrigerator

    International Nuclear Information System (INIS)

    A test refrigerator based on the modified Reverse Brayton cycle has been developed in the Chinese Academy of Sciences recently. To study the behaviors of this test refrigerator, a dynamic simulation has been carried out. The numerical model comprises the typical components of the test refrigerator: compressor, valves, heat exchangers, expander and heater. This simulator is based on the oriented-object approach and each component is represented by a set of differential and algebraic equations. The control system of the test refrigerator is also simulated, which can be used to optimize the control strategies. This paper describes all the models and shows the simulation results. Comparisons between simulation results and experimental data are also presented. Experimental validation on the test refrigerator gives satisfactory results

  1. Performance comparison of different supercritical carbon dioxide Brayton cycles integrated with a solar power tower

    International Nuclear Information System (INIS)

    In this study, a thermodynamic comparison of five supercritical carbon dioxide Brayton cycles integrated with a solar power tower was conducted. The Brayton cycles analyzed were simple Brayton cycle, regenerative Brayton cycle, recompression Brayton cycle, pre-compression Brayton cycle, and split expansion Brayton cycle. A complete mathematical code was developed to carry out the analysis. A heliostat field layout was generated and then optimized on an annual basis using the differential evolution method, which is an evolutionary algorithm. The heliostat field was optimized for optical performance and then integrated with the supercritical CO2 Brayton cycles. Using the results of the optimization, a comparison of net power outputs and thermal efficiencies for these cycles was performed. The findings demonstrated that the highest thermal efficiency was achieved using the recompression Brayton cycle, at June noontime. The maximum integrated system thermal efficiency using this cycle was 40% while the maximum thermal efficiency of this cycle alone was 52%. The regenerative Brayton cycle, although simpler in configuration, shows comparable performance to the recompression Brayton cycle. This analysis was carried out for Dhahran, Saudi Arabia. - Highlights: • The heliostat field of the solar power tower optimized and its optical efficiency identified. • Performance of the solar power tower integrated with five sCO2 Brayton Cycles was assessed. • Recompression supercritical CO2 Brayton cycle has the best performance. • The regenerative supercritical CO2 Brayton cycle has the second best performance

  2. Thermodynamic Optimization of Supercritical CO2 Brayton Cycles

    International Nuclear Information System (INIS)

    The supercritical CO2 Brayton cycle has been studied for nuclear applications, mainly for one of the alternative power conversion systems of the sodium cooled fast reactor, since 1960's. Although the supercritical CO2 Brayton cycle has not been expected to show higher efficiency at lower turbine inlet temperature over the conventional steam Rankine cycle, the higher density of supercritical CO2 like a liquid in the supercritical region could reduce turbo-machinery sizes, and the potential problem of sodium-water reaction with the sodium cooled fast reactor might be solved with the use of CO2 instead of water. The supercritical CO2 recompression Brayton cycle was proposed for the better thermodynamic efficiency than for the simple supercritical CO2 Brayton cycle. Thus this paper presents the efficiencies of the supercritical CO2 recompression Brayton cycle along with several decision variables for the thermodynamic optimization of the supercritical CO2 recompression Brayton cycle. The analytic results in this study show that the system efficiency reaches its maximum value at a compressor outlet pressure of 200 bars and a recycle fraction of 30 %, and the lower minimum temperature approach at the two heat exchangers shows higher system efficiency as expected

  3. Thermodynamic Optimization of Supercritical CO{sub 2} Brayton Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Dong-Ryul; Park, Sung-Ho; Kim, Su-Hyun; Yeom, Choong-Sub [Institute for Advanced Engineering, Yongin (Korea, Republic of)

    2015-05-15

    The supercritical CO{sub 2} Brayton cycle has been studied for nuclear applications, mainly for one of the alternative power conversion systems of the sodium cooled fast reactor, since 1960's. Although the supercritical CO{sub 2} Brayton cycle has not been expected to show higher efficiency at lower turbine inlet temperature over the conventional steam Rankine cycle, the higher density of supercritical CO{sub 2} like a liquid in the supercritical region could reduce turbo-machinery sizes, and the potential problem of sodium-water reaction with the sodium cooled fast reactor might be solved with the use of CO{sub 2} instead of water. The supercritical CO{sub 2} recompression Brayton cycle was proposed for the better thermodynamic efficiency than for the simple supercritical CO{sub 2} Brayton cycle. Thus this paper presents the efficiencies of the supercritical CO{sub 2} recompression Brayton cycle along with several decision variables for the thermodynamic optimization of the supercritical CO{sub 2} recompression Brayton cycle. The analytic results in this study show that the system efficiency reaches its maximum value at a compressor outlet pressure of 200 bars and a recycle fraction of 30 %, and the lower minimum temperature approach at the two heat exchangers shows higher system efficiency as expected.

  4. Advanced Supercritical Carbon Dioxide Brayton Cycle Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark [Univ. of Wisconsin, Madison, WI (United States); Sienicki, James [Argonne National Lab. (ANL), Argonne, IL (United States); Moisseytsev, Anton [Argonne National Lab. (ANL), Argonne, IL (United States); Nellis, Gregory [Univ. of Wisconsin, Madison, WI (United States); Klein, Sanford [Univ. of Wisconsin, Madison, WI (United States)

    2015-10-21

    -through labyrinth seals was proposed. A stepped labyrinth seal, which mimics the behavior of the labyrinth seal used in the Sandia National Laboratory (SNL) S-CO2 Brayton cycle, was also tested in the experiment along with simulations performed. The rest of this study demonstrates the difference of valves' behavior under supercritical fluid and normal fluid conditions. A small-scale valve was tested in the experiment facility using S-CO2. Different percentages of opening valves were tested, and the measured mass flow rate agreed with simulation predictions. Two transients from a real S-CO2 Brayton cycle design provided the data for valve selection. The selected valve was studied using numerical simulation, as experimental data is not available.

  5. Systems Analyses of Advanced Brayton Cycles

    Energy Technology Data Exchange (ETDEWEB)

    A.D. Rao; D.J. Francuz; J.D. Maclay; J. Brouwer; A. Verma; M. Li; G.S. Samuelsen

    2008-09-30

    The main objective is to identify and assess advanced improvements to the Brayton Cycle (such as but not limited to firing temperature, pressure ratio, combustion techniques, intercooling, fuel or combustion air augmentation, enhanced blade cooling schemes) that will lead to significant performance improvements in coal based power systems. This assessment is conducted in the context of conceptual design studies (systems studies) that advance state-of-art Brayton cycles and result in coal based efficiencies equivalent to 65% + on natural gas basis (LHV), or approximately an 8% reduction in heat rate of an IGCC plant utilizing the H class steam cooled gas turbine. H class gas turbines are commercially offered by General Electric and Mitsubishi for natural gas based combined cycle applications with 60% efficiency (LHV) and it is expected that such machine will be offered for syngas applications within the next 10 years. The studies are being sufficiently detailed so that third parties will be able to validate portions or all of the studies. The designs and system studies are based on plants for near zero emissions (including CO{sub 2}). Also included in this program is the performance evaluation of other advanced technologies such as advanced compression concepts and the fuel cell based combined cycle. The objective of the fuel cell based combined cycle task is to identify the desired performance characteristics and design basis for a gas turbine that will be integrated with an SOFC in Integrated Gasification Fuel Cell (IGFC) applications. The goal is the conceptualization of near zero emission (including CO{sub 2} capture) integrated gasification power plants producing electricity as the principle product. The capability of such plants to coproduce H{sub 2} is qualitatively addressed. Since a total systems solution is critical to establishing a plant configuration worthy of a comprehensive market interest, a baseline IGCC plant scheme is developed and used to study

  6. Power enhancement of the Brayton cycle by steam utilization

    Science.gov (United States)

    Jesionek, Krzysztof; Chrzczonowski, Andrzej; Ziółkowski, Paweł; Badur, Janusz

    2012-09-01

    The paper presents thermodynamic analysis of the gas-steam unit of the 65 MWe combined heat and power station. Numerical analyses of the station was performed for the nominal operation conditions determining the Brayton and combined cycle. Furthermore, steam utilization for the gas turbine propulsion in the Cheng cycle was analysed. In the considered modernization, steam generated in the heat recovery steam generator unit is directed into the gas turbine combustion chamber, resulting in the Brayton cycle power increase. Computational flow mechanics codes were used in the analysis of the thermodynamic and operational parameters of the unit.

  7. Combined-Brayton cycle, space nuclear power systems

    International Nuclear Information System (INIS)

    Because it is a widely recognized dynamic space conversion system, the Brayton cycle has been studied in France since several years, especially within the framework of a limited space program. A recuperated cycle of 20 to 30 kWe has been considered so far. However, possible applications could evolve and the need for an extended, diversified utilization of the Brayton cycle could appear. So, for Lunar or Mars bases which would accept large radiators and can benefit from a certain gravity level, combined cycle systems could be proposed. Following a reference to past works on space combined cycles, a possible association of a Brayton cycle with a thermoionic reactor is presented. The power level of a 'Topaz-2' type space nuclear system can be boosted from 8 kWe to around 36 to 53 kWe, at the expense of a large radiator of course. Furthermore, combined Brayton-Rankine, organic (toluene) or steam, cycles can pave the way to a simpler gas-cooled, particle bed reactor concept. A particular arrangement of HeXe heater and boiler or steam generator in series is proposed. It makes it possible to lower the reactor inlet temperature, which is quite adequate for the use of light water as moderator. Oustanding net efficiencies of 25.8 to 27.6 per cent, given the reactor temperature profile, are obtained. Consequences on the reactor design are mentioned

  8. SP-100 reactor with Brayton conversion for lunar surface applications

    International Nuclear Information System (INIS)

    Examined here is the potential for integrating Brayton-cycle power conversion with the SP-100 reactor for lunar surface power system applications. Two designs were characterized and modeled. The first design integrates a 100-kWe SP-100 Brayton power system with a lunar lander. This system is intended to meet early lunar mission power needs while minimizing on-site installation requirements. Man-rated radiation protection is provided by an integral multilayer, cylindrical lithium hydride/tungsten (LiH/W) shield encircling the reactor vessel. Design emphasis is on ease of deployment, safety, and reliability, while utilizing relatively near-term technology. The second design combines Brayton conversion with the SP-100 reactor in a erectable 550-kWe powerplant concept intended to satisfy later-phase lunar base power requirements. This system capitalizes on experience gained from operating the initial 100-kWe module and incorporates some technology improvements. For this system, the reactor is emplaced in a lunar regolith excavation to provide man-rated shielding, and the Brayton engines and radiators are mounted on the lunar surface and extend radially from the central reactor. Design emphasis is on performance, safety, long life, and operational flexibility

  9. Nuclear reactor closed Brayton cycle space power conversion systems

    International Nuclear Information System (INIS)

    This paper presents the past history, present status and future prospects for closed Brayton cycle power conversion systems to be used in space when requirements have been established. Since there is a classic lack of coordination between advanced technology and its perceived need that can be strongly affected by associated factors, recommendations will be made to assist in the current situation. 4 refs

  10. Perspectiva temporal futura y ciclo vital

    OpenAIRE

    Díaz Morales, Juan Francisco

    2006-01-01

    El propósito de este estudio es describir qué cambios se producen en la perspectiva temporal futura (PTF) durante el ciclo vital. Para evaluar la PTF a lo largo del ciclo vital se ha utilizado el modelo de Nurmi (1989), que consta de tres componentes: motivación, planificación y evaluación prospectiva. En el estudio participaron cuatro grupos de personas de diferentes edades: 130 adolescentes (15-18 años), 150 estudiantes universitarios (19-28 años), 100 personas de mediana edad (30-59 años) ...

  11. Atuação da enfermagem na utilização do catéter venoso totalmente implantável (CVTI

    Directory of Open Access Journals (Sweden)

    Rosemeire A. Mendes Lopes

    1993-06-01

    Full Text Available As autoras fizeram um levantamento de 41 casos de utilização do cateter venoso totalmente implantável usados para tratamento com drogas antineoplásicas. Descreveram os motivos que levaram o serviço a utilizar este sistema para infusão e analisaram sua utilização, seu controle e as intercorrências. Os resultados, embora tenham mostrado um índice de complicações de 29%, incluindo falhas na técnica de implantação e no manuseio, apresentaram um bom índice de aproveitamento, ou seja, 61%.

  12. Closed Brayton cycle power conversion systems for nuclear reactors :

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven A.; Lipinski, Ronald J.; Vernon, Milton E.; Sanchez, Travis

    2006-04-01

    This report describes the results of a Sandia National Laboratories internally funded research program to study the coupling of nuclear reactors to gas dynamic Brayton power conversion systems. The research focused on developing integrated dynamic system models, fabricating a 10-30 kWe closed loop Brayton cycle, and validating these models by operating the Brayton test-loop. The work tasks were performed in three major areas. First, the system equations and dynamic models for reactors and Closed Brayton Cycle (CBC) systems were developed and implemented in SIMULINKTM. Within this effort, both steady state and dynamic system models for all the components (turbines, compressors, reactors, ducting, alternators, heat exchangers, and space based radiators) were developed and assembled into complete systems for gas cooled reactors, liquid metal reactors, and electrically heated simulators. Various control modules that use proportional-integral-differential (PID) feedback loops for the reactor and the power-conversion shaft speed were also developed and implemented. The simulation code is called RPCSIM (Reactor Power and Control Simulator). In the second task an open cycle commercially available Capstone C30 micro-turbine power generator was modified to provide a small inexpensive closed Brayton cycle test loop called the Sandia Brayton test-Loop (SBL-30). The Capstone gas-turbine unit housing was modified to permit the attachment of an electrical heater and a water cooled chiller to form a closed loop. The Capstone turbine, compressor, and alternator were used without modification. The Capstone systems nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system also were reused. The rotational speed of the turbo-machinery is controlled by adjusting the alternator load by using the electrical grid as the load bank. The SBL-30 test loop was operated at

  13. Operation and analysis of a supercritical CO2 Brayton cycle.

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven Alan; Radel, Ross F.; Vernon, Milton E.; Pickard, Paul S.; Rochau, Gary Eugene

    2010-09-01

    Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for use with solar, nuclear or fossil heat sources. The focus of this work has been on the supercritical CO{sub 2} cycle (S-CO2) which has the potential for high efficiency in the temperature range of interest for these heat sources, and is also very compact, with the potential for lower capital costs. The first step in the development of these advanced cycles was the construction of a small scale Brayton cycle loop, funded by the Laboratory Directed Research & Development program, to study the key issue of compression near the critical point of CO{sub 2}. This document outlines the design of the small scale loop, describes the major components, presents models of system performance, including losses, leakage, windage, compressor performance, and flow map predictions, and finally describes the experimental results that have been generated.

  14. Rankline-Brayton engine powered solar thermal aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Charles L. (Livermore, CA)

    2012-03-13

    A solar thermal powered aircraft powered by heat energy from the sun. A Rankine-Brayton hybrid cycle heat engine is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller or other mechanism for enabling sustained free flight. The Rankine-Brayton engine has a thermal battery, preferably containing a lithium-hydride and lithium mixture, operably connected to it so that heat is supplied from the thermal battery to a working fluid. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

  15. Rankine-Brayton engine powered solar thermal aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Charles L. (Livermore, CA)

    2009-12-29

    A solar thermal powered aircraft powered by heat energy from the sun. A Rankine-Brayton hybrid cycle heat engine is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller or other mechanism for enabling sustained free flight. The Rankine-Brayton engine has a thermal battery, preferably containing a lithium-hydride and lithium mixture, operably connected to it so that heat is supplied from the thermal battery to a working fluid. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

  16. Cold startup and low temperature performance of the Brayton cycle electrical subsystem

    Science.gov (United States)

    Vrancik, J. E.; Bainbridge, R. C.

    1971-01-01

    Cold performance tests and startup tests were conducted on the Brayton-cycle inverter, motor-driven pump, dc supply, speed control with parasitic load resistor and the Brayton control system. These tests were performed with the components in a vacuum and mounted on coldplates. A temperature range of ?25 to -50 C was used for the tests. No failures occurred, and component performance gave no indication that there would be any problem with the safe operation of the Brayton power generating system.

  17. Modeling and Simulation of a Desiccant Assisted Brayton Refrigeration Cycle

    OpenAIRE

    Nobrega, Carlos E.L.; Sphaier, Leandro Alcoforado

    2012-01-01

    The phase-out of CFCs has shed a new light over natural refrigerants, which have null global warming potentials. Air would be a natural choice, and although the Brayton cycle usually exhibits a lower coefficient of performance when compared to vapor-compression systems of same capacity, it has been considered in applications other than aircraft cooling. These include gas separation, food processing and preservation, refrigerated containers and train air-conditioning. Price perspectives in the...

  18. Thermal analysis of the heat recuperator of a combined cycle thermoelectric central; Analisis termico del recuperador de calor de una central termoelectrica de ciclo combinado

    Energy Technology Data Exchange (ETDEWEB)

    Romero Paredes, Hernando; Sanchez, I.; Lazcano, L. C.; Ambriz, Juan Jose; Alvarez, M. [Universidad Autonoma Metropolitana-Iztapalapa, Mexico, D. F. (Mexico); Gonzalez, O. [Comision Federal de Electricidad, Tula (Mexico)

    1996-12-31

    The thermoelectric centrals of the combined cycle type (Brayton Cycle and Rankine Cycle) present a series of opportunities to increase the efficiency of the combined cycle or of the generated power. This paper shows the methodology for the performance of energy balances in a heat recuperator (H. R.), typically employed in the combined cycle stations operating in Mexico, for the assessment of the energy harnessing in the different sections conforming a H. R. The effect of the installation of evaporative coolers and/or an absorption cooling system at the gas turbine compressor intake on the steam generation in the heat recuperator, is evaluated. This extra generation of steam is quantified for its potential use in the same absorption refrigeration system. From the assessment, it follows up that the steam generation in the H.R. is inversely proportional to the ambient temperature and that, although the increased amount of steam generated can not be harnessed in total by the steam turbine, the remaining fraction is good enough to cover the heat demand for the operation of the refrigeration system. [Espanol] Las centrales termoelectricas del tipo ciclo combinado (ciclo Brayton y ciclo Rankine) presentan un conjunto de oportunidades para incrementar la eficiencia del ciclo combinado o bien la potencia generada. En el presente trabajo se expone la metodologia para realizar los balances de energia en un recuperador de calor (R.C.) tipicamente utilizado en las Centrales de Ciclo Combinado (CCC) que operan en Mexico, para evaluar el aprovechamiento de la energia en las diferentes secciones que conforman un R.C. Se evalua el efecto que tiene la instalacion de enfriadores evaporativos y/o un sistema de enfriamiento por absorcion en la succion del compresor de la turbina de gas sobre la generacion de vapor en el recuperador de calor. Se cuantifica esta generacion extra de vapor para su posible utilizacion en el mismo sistema de refrigeracion por absorcion. De la evaluacion se

  19. Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

    International Nuclear Information System (INIS)

    This report contains the description of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For system development, a computer code was developed to calculate heat balance of 100% power operation condition. Based on the computer code, the S-CO2 Brayton cycle energy conversion system was constructed for the KALIMER-600. Using the developed turbomachinery models, the off-design characteristics and the sensitivities of the S-CO2 turbomachinery were investigated. For the development of PCHE models, a one-dimensional analysis computer code was developed to evaluate the performance of the PCHE. Possible control schemes for power control in the KALIMER-600 S-CO2 Brayton cycle were investigated by using the MARS code. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na/CO2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO2 gas. The long term behavior of a Na/CO2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

  20. Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jae Eun; Kim, S. O.; Seong, S. H.; Eoh, J. H.; Lee, T. H.; Choi, S. K.; Han, J. W.; Bae, S. W

    2007-12-15

    This report contains the description of the S-CO{sub 2} Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For system development, a computer code was developed to calculate heat balance of 100% power operation condition. Based on the computer code, the S-CO{sub 2} Brayton cycle energy conversion system was constructed for the KALIMER-600. Using the developed turbomachinery models, the off-design characteristics and the sensitivities of the S-CO{sub 2} turbomachinery were investigated. For the development of PCHE models, a one-dimensional analysis computer code was developed to evaluate the performance of the PCHE. Possible control schemes for power control in the KALIMER-600 S-CO{sub 2} Brayton cycle were investigated by using the MARS code. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na/CO{sub 2} boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO{sub 2} gas. The long term behavior of a Na/CO{sub 2} boundary failure event and its consequences which lead to a system pressure transient were evaluated.

  1. Applications of Brayton Cycle technology to space power

    International Nuclear Information System (INIS)

    The Closed Brayton (CBC) power conversion cycle can be used with a wide range of heat sources for space power applications. These heat source include solar concentrator, radioisotope, and reactor. With a solar concentrator, a solar dynamic ground demonstration test using existing Brayton components is being assembled for testing at NASA Lewis Research Center (LeRC). This 2-kWe system has a turbine inlet temperature of 1,015 K and is a complete end-to-end simulation of the Space Station Freedom solar dynamic design. With a radioisotope heat source, a 1-kWe Dynamic Isotope Power System (DIPS) is under development using an existing turbo alternator compressor (TAC) for testing at the same NASA-LeRC facility. This DIPS unit is being developed as a replacement to Radioisotopic Thermoelectric Generators (RTGs) to conserve the Pu-238 supply for interplanetary exploration. With a reactor heat source, many studies have been performed coupling the SP-100 reactor with a Brayton power conversion cycle. Applications for this reactor/CBC system include global communications satellites and electric propulsion for interplanetary exploration

  2. Simulation of CO2 Brayton Cycle for Engine Exhaust Heat Recovery under Various Operating Loads

    Institute of Scientific and Technical Information of China (English)

    舒歌群; 张承宇; 田华; 高媛媛; 李团兵; 仇荣赓

    2015-01-01

    A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9%and the system has a better performance at the engine’s high operating load. The thermal efficiency can be as large as 24.83%under 100%operating load, accordingly, the net output power of 14.86 kW is obtained.

  3. A Brayton cycle solar dynamic heat receiver for space

    Science.gov (United States)

    Sedgwick, L. M.; Nordwall, H. L.; Kaufmann, K. J.; Johnson, S. D.

    1989-01-01

    The detailed design of a heat receiver developed to meet the requirements of the Space Station Freedom, which will be assembled and operated in low earth orbit beginning in the mid-1990's, is described. The heat receiver supplies thermal energy to a nominal 25-kW closed-Brayton-cycle power conversion unit. The receiver employs an integral thermal energy storage system utilizing the latent heat of a eutectic-salt phase-change mixture to store energy for eclipse operation. The salt is contained within a felt metal matrix which enhances heat transfer and controls the salt void distribution during solidification.

  4. Personalidad sana en el ciclo vital

    OpenAIRE

    Fierro Bardají, Alfredo

    2015-01-01

    En el desarrollo de la personalidad, de la persona, en su devenir hacia la madurez, la psicología se interesa, desde luego, por los cambios comportamentales debidos al ciclo biológico, pero, no menos, a los que se siguen de un determinado curso de experiencias y de acciones de la persona individual. En este último sentido la personalidad no sólo crece o se desarrolla; asimismo aprende y en algún sentido se hace a sí misma, contribuye al curso de su propia vida. Universidad de Málaga. Campu...

  5. Autorrelatos do amor no ciclo vital adulto

    OpenAIRE

    José Augusto Evangelho Hernandez; Sinele Valle da Costa; Juliana Ramos Ribeiro; Caroline Almeida Areias; Karina Nascimento Valladares dos Santos

    2015-01-01

    Esta pesquisa transversal comparou grupos de pessoas de diferentes faixas etárias, adultos jovens, maduros e maiores de 50 anos. Foram verificadas possíveis modificações do amor ao longo do ciclo vital adulto. Participaram 211 sujeitos de ambos os sexos, envolvidos em tipos variados de relações amorosas, que responderam à Escala Triangular do Amor de Sternberg. Os resultados da análise de variância multivariada mostraram interações significativas entre os componentes do amor e as faixas etári...

  6. Ciclo de vida del entomonematodo nativo

    OpenAIRE

    Sáenz, Adriana; Luque, Jesús Emilio

    2011-01-01

    En el laboratorio de Control Biológico de la Facultad de Agronomía de la Universidad Nacional, sede Bogotá, se estudio la biología básica del entomonemátodo nativo Steinernema feltiae Filipjev, 1934 (Rhabditida: Steinemematidae). Utilizando larvas de último instar de la polilla mayor de las colmenas Galleria mellonella, expuestas a 8000 juveniles infectivos/caja de petri y realizando disecciones diariamente, se determinaron los estados de desarrollo, duración del ciclo vida y relación de sexo...

  7. Thermodynamic Modeling for Open Combined Regenerative Brayton and Inverse Brayton Cycles with Regeneration before the Inverse Cycle

    Directory of Open Access Journals (Sweden)

    Lingen Chen

    2012-01-01

    Full Text Available A thermodynamic model of an open combined regenerative Brayton and inverse Brayton cycles with regeneration before the inverse cycle is established in this paper by using thermodynamic optimization theory. The flow processes of the working fluid with the pressure drops and the size constraint of the real power plant are modeled. There are 13 flow resistances encountered by the working fluid stream for the cycle model. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining nine flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, regenerator inlet and outlet, combustion chamber inlet and outlet, turbine outlet of the top cycle, turbine outlet of the bottom cycle, heat exchanger inlet, and compressor inlet of the bottom cycle. These resistances associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle, and control the air flow rate, the net power output and the thermal efficiency. The analytical formulae about the power output, efficiency and other coefficients are derived with 13 pressure drop losses. It is found that the combined cycle with regenerator can reach higher thermal efficiency but smaller power output than those of the base combined cycle at small compressor inlet relative pressure drop of the top cycle.

  8. Key Factors Influencing the Decision on the Number of Brayton Units for the Prometheus Space Reactor

    Science.gov (United States)

    Ashcroft, John; Belanger, Sean; Burdge, Wayne; Clementoni, Eric; Jensen, Krista; Proctor, N. Beth; Zemo-Fulkerson, Annie

    2007-01-01

    The Naval Reactors (NR) Program and its DOE Laboratories, KAPL and Bettis, were assigned responsibility to develop space reactor systems for the Prometheus Program. After investigating all of the potential reactor and energy conversion options, KAPL and Bettis selected a direct gas Brayton system as the reference approach for the nuclear electric propulsion missions, including the Jupiter Icy Moons Orbiter (JIMO). In order to determine the optimal plant architecture for the direct gas system, KAPL and Bettis investigated systems with one or two active Brayton units and up to two spare units. No final decision was made on the optimal system configuration for the NEP gas-Brayton system prior to closeout of the project. The two most promising options appear to be a single system without spares and a three Brayton system with two operating units, each producing half of the required load, with a single spare unit. The studies show that a single Brayton system, without spares, offers the lowest mass system, with potential for lower operating temperature, and a minimum of system and operational complexity. The lower required mass and increased system efficiency inherent in the single Brayton system may be exploited to satisfy other design objectives such as reduced reactor and radiator operating temperatures. While Brayton system lifetimes applicable to a JIMO or other nuclear electric propulsion (NEP) mission have not been demonstrated, there is no fundamental limit on the lifetime of the Brayton hardware. Use of additional Brayton units with installed spares will allow for continued operation in the event of a failure of an individual Brayton unit. However, preliminary system reliability evaluations do not point to any substantial reliability benefit provided by carrying spare Brayton units. If a spare unit is used, operating two of the units at full power with an unpowered spare proved more efficient than operating all three units at a reduced power and temperature

  9. Gas Foil Bearing Technology Advancements for Closed Brayton Cycle Turbines

    Science.gov (United States)

    Howard, Samuel A.; Bruckner, Robert J.; DellaCorte, Christopher; Radil, Kevin C.

    2007-01-01

    Closed Brayton Cycle (CBC) turbine systems are under consideration for future space electric power generation. CBC turbines convert thermal energy from a nuclear reactor, or other heat source, to electrical power using a closed-loop cycle. The operating fluid in the closed-loop is commonly a high pressure inert gas mixture that cannot tolerate contamination. One source of potential contamination in a system such as this is the lubricant used in the turbomachine bearings. Gas Foil Bearings (GFB) represent a bearing technology that eliminates the possibility of contamination by using the working fluid as the lubricant. Thus, foil bearings are well suited to application in space power CBC turbine systems. NASA Glenn Research Center is actively researching GFB technology for use in these CBC power turbines. A power loss model has been developed, and the effects of a very high ambient pressure, start-up torque, and misalignment, have been observed and are reported here.

  10. Solar/gas Brayton/Rankine cycle heat pump assessment

    Science.gov (United States)

    Rousseau, J.; Liu, A. Y.

    1982-05-01

    A 10-ton gas-fired heat pump is currently under development at AiResearch under joint DOE and GRI sponsorship. This heat pump features a highly efficient, recuperated, subatmospheric Brayton-cycle engine which drives the centrifugal compressor of a reversible vapor compression heat pump. The investigations under this program were concerned initially with the integration of this machine with a parabolic dish-type solar collector. Computer models were developed to accurately describe the performance of the heat pump packaged in this fashion. The study determined that (1) only a small portion (20 to 50 percent) of the available solar energy could be used because of a fundamental mismatch between the heating and cooling demand and the availability of solar energy, and (2) the simple pay back period, by comparison to the baseline non-solar gas-fired heat pump, was unacceptable (15 to 36 years).

  11. Evaluation of Silicon Nitride for Brayton Turbine Wheel Application

    Science.gov (United States)

    Freedman, Marc R.

    2008-01-01

    Silicon nitride (Si3N4) is being evaluated as a risk-reduction alternative for a Jupiter Icy Moons Orbiter Brayton turbine wheel in the event that the Prometheus program design requirements exceed the creep strength of the baseline metallic superalloys. Five Si3N4 ceramics, each processed by a different method, were screened based on the Weibull distribution of bend strength at 1700 F (927 C). Three of the Si3N4 ceramics, Honeywell AS800, Kyocera SN282, and Saint-Gobain NT154, had bend strengths in excess of 87 ksi (600 MPa) at 1700 F (927 C). These were chosen for further assessment and consideration for future subcomponent and component fabrication and testing.

  12. Brayton isotope power system. Volume II. System evaluation attributes

    Energy Technology Data Exchange (ETDEWEB)

    1978-03-15

    This volume of the Brayton Isotope Power System, Phase II Plan, contains the self-evaluation by AiResearch, GE, and TECO, addressing Section 3 of The Dynamic Systems Evaluation Criteria and Procedures established by the Department of Energy. These evaluation criteria addresses: Component Feasibility; Flight System Design Performance; GDS Test Results; Reliability and Practicality; Safety; Spacecraft Integration; and Cost and Risk. Included in each of these general categories are several attributes, each of which addresses a separate component, feature, or area of interest related to the power system, its development status, degree of preparedness for proceeding into a flight program, and/or the contractors' performance during Phase I. The key elements which indicate the readiness of a radioisotope power system to progress into a flight qualification program are: an advanced state of development of the power conversion system; demonstrated or exhibited potential for space systems standards of reliability; evident capability of meeting system safety requirements; favorable cost/benefit tradeoff considering projected missions and technology advancement potential; and proven feasibility of fabricating and qualifying a flight system and integrating it with a candidate spacecraft and launch vehicle. As a result of considerable government investment in Brayton system component development, the MHW isotope heat source and the BIPS Phase I Ground Demonstration System, the BIPS is a more advanced state of development than any previous radioisotope power system technology. Evidence of this is presented along with a complete review of the attributes, the contractor recommended ratings, and the rationale for the self-evaluation.

  13. Calculation principles of humid air in a reversed Brayton cycle

    Energy Technology Data Exchange (ETDEWEB)

    Backman, J. [Lappeenranta Univ. of Technology (Finland). Dept. of Energy Technology

    1997-12-31

    The article presents a calculation method for reversed Brayton cycle that uses humid air as working medium. The reversed Brayton cycle can be employed as an air dryer, a heat pump or a refrigerating machine. In this research the use of humid air as a working fluid has an environmental advantage, as well. In this method especially the expansion process in the turbine is important because of the condensation of the water vapour in the humid air. This physical phenomena can have significant effects on the level of performance of the application. The expansion process differs physically from the compression process, when the water vapour in the humid air begins to condensate. In the thermodynamic equilibrium of the flow, the water vapour pressure in humid air cannot exceed the pressure of saturated water vapour in corresponding temperature. Expansion calculation during operation around the saturation zone is based on a quasistatic expansion, in which the system after the turbine is in thermodynamical equilibrium. The state parameters are at every moment defined by the equation of state, and there is no supercooling in the vapour. Following simplifications are used in the calculations: The system is assumed to be adiabatic. This means that there is no heat transfer to the surroundings. This is a common practice, when the temperature differences are moderate as here; The power of the cooling is omitted. The cooling construction is very dependent on the machine and the distribution of the losses; The flow is assumed to be one-dimensional, steady-state and homogenous. The water vapour condensing in the turbine can cause errors, but the errors are mainly included in the efficiency calculation. (author) 11 refs.

  14. Development of a 77K Reverse-Brayton Cryocooler with Multiple Coldheads Project

    Data.gov (United States)

    National Aeronautics and Space Administration — RTI will design and optimize an 80 W, 77K cryocooler based on the reverse turbo Brayton cycle (RTBC) with four identical coldheads for distributed cooling. Based on...

  15. Automatic Control Strategy Development for the Supercritical CO2 Brayton Cycle for LFR Autonomous Load Following

    International Nuclear Information System (INIS)

    The supercritical carbon dioxide (S-CO2) Brayton cycle is a promising advanced alternative to the Rankine saturated steam cycle and ideal gas Brayton cycle for the energy converters of specific reactor concepts belonging to the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. A new plant dynamics analysis computer code has been developed for simulation of the S-CO2 Brayton cycle coupled to an autonomous Lead-Cooled Fast Reactor (LFR). The plant dynamics code was used to develop an automatic control strategy for the whole plant in response to changes in the demand from the electrical grid. The specific features of the S-CO2 Brayton cycle that result in limitations on the control range and speed of specific control mechanisms are discussed. Calculations of whole-plant responses to plant operational transients involving step and continuous changes in grid demand are demonstrated. (authors)

  16. Phase I: controls preliminary design report for Brayton Isotope Power System (BIPS)

    International Nuclear Information System (INIS)

    Background analyses of three control systems capable of controlling the speed, output voltage, and start rate of Brayton Isotope Power Systems (BIPS) are presented. Conclusions of all functions considered are summarized

  17. System design specification Brayton Isotope Power System (BIPS) Flight System (FS), and Ground Demonstration System (GDS)

    Energy Technology Data Exchange (ETDEWEB)

    1976-06-14

    The system design specification for ground demonstration, development, and flight qualification of a Brayton Isotope Power System (BIPS) is presented. The requirements for both a BIPS conceptual Flight System (FS) and a Ground Demonstration System (GDS) are defined.

  18. System design specification Brayton Isotope Power System (BIPS) Flight System (FS), and Ground Demonstration System (GDS)

    International Nuclear Information System (INIS)

    The system design specification for ground demonstration, development, and flight qualification of a Brayton Isotope Power System (BIPS) is presented. The requirements for both a BIPS conceptual Flight System (FS) and a Ground Demonstration System (GDS) are defined

  19. Phase I: controls preliminary design report for Brayton Isotope Power System (BIPS)

    Energy Technology Data Exchange (ETDEWEB)

    1976-08-20

    Background analyses of three control systems capable of controlling the speed, output voltage, and start rate of Brayton Isotope Power Systems (BIPS) are presented. Conclusions of all functions considered are summarized. (TFD)

  20. Optimization of the performance characteristics in an irreversible regeneration magnetic Brayton refrigeration cycle

    Science.gov (United States)

    Wang, Hao; Wu, GuoXing

    2012-02-01

    A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established, in which the regeneration problem in two constant-magnetic field processes and the irreversibility in two adiabatic processes are considered synthetically. Expressions for the COP, cooling rate, power input, the minimum ratio of the two magnetic fields, etc., are derived. It is found that the influence of the irreversibility and the regeneration on the main performance parameters of the magnetic Brayton refrigerator is remarkable. It is important that we have obtained several optimal criteria, which may provide some theoretical basis for the optimal design and operation of the Brayton refrigerator. The results obtained in the paper can provide some new theoretical information for the optimal design and performance improvement of real Brayton refrigerators.

  1. Influência do ciclo lunar na captura de morcegos Phyllostomidae Influence of moon cycle in phyllostomid bat capture

    Directory of Open Access Journals (Sweden)

    Carlos E. L. Esbérard

    2007-03-01

    Full Text Available A influência da luz da lua no padrão de atividade de morcegos já foi documentada em algumas espécies. Geralmente os morcegos reagem ao aumento da iluminação reduzindo o uso de espaços abertos e restringindo a atividade de forrageio ou a duração do período de atividade. Para estabelecer a influência do ciclo lunar na eficiência de captura de morcegos, foi realizada uma análise com 28 noites de capturas no sudeste do Brasil. A taxa de captura e a riqueza de espécies apresentaram relação linear inversa com a porção iluminada pela lua. Das espécies mais freqüentemente capturadas, apenas duas apresentaram relação significativa e negativa com o aumento da iluminação pela lua. Maiores variações na riqueza de espécies foram observadas em morcegos catadores e nectarívoros. Os dias após a lua nova são os mais produtivos em relação a capturas e riqueza. A riqueza local não pode ser totalmente amostrada se a amostragem for restrita a qualquer período do ciclo lunar. Para estudar a comunidade de morcegos é mais apropriado realizar amostragem durante todo o ciclo lunar.The influence of moonlight on the activity patterns of bats has been reported to some species. In general, bats react to the increase of nocturnal illumination by reducing the use of open spaces, by limiting foraging activity or by shortening the activity periods. To determine the influence of moon cycle on the efficiency of bat netting, captures of 28 night-samplings were analyzed in southeastern Brazil. The capture rate and species richness were inversely related to the moonlight intensity. Among the most frequently netted species, only two showed significant and negative relation with increasing moonlight. The highest variation in species richness was observed in gleaners and nectarivorous species. The days following new moon were the most productive in terms of capture rate and species richness. The local species richness was not archived when sampling was

  2. Exergy analyses of an endoreversible closed regenerative Brayton cycle CCHP plant

    OpenAIRE

    Bo Yang, Lingen Chen, Fengrui Sun

    2014-01-01

    An endoreversible closed regenerative Brayton cycle CCHP (combined cooling, heating and power) plant coupled to constant-temperature heat reservoirs is presented using finite time thermodynamics (FTT). The CCHP plant includes an endoreversible closed regenerative Brayton cycle, an endoreversible four-heat-reservoir absorption refrigerator and a heat recovery device of thermal consumer. The heat-resistance losses in the hot-, cold-, thermal consumer-, generator-, condenser-, evaporator- and ab...

  3. Assessing the potential of hybrid fossil–solar thermal plants for energy policy making: Brayton cycles

    International Nuclear Information System (INIS)

    This paper proposes a first study in-depth of solar–fossil hybridization from a general perspective. It develops a set of useful parameters for analyzing and comparing hybrid plants, it studies the case of hybridizing Brayton cycles with current solar technologies and shows a tentative extrapolation of the results to integrated combined cycle systems (ISCSS). In particular, three points have been analyzed: the technical requirements for solar technologies to be hybridized with Brayton cycles, the temperatures and pressures at which hybridization would produce maximum power per unit of fossil fuel, and their mapping to current solar technologies and Brayton cycles. Major conclusions are that a hybrid plant works in optimum conditions which are not equal to those of the solar or power blocks considered independently, and that hybridizing at the Brayton cycle of a combined cycle could be energetically advantageous. -- Highlights: •We model a generic solar–fossil hybrid Brayton cycle. •We calculate the operating conditions for maximum ratio power/fuel consumption. •Best hybrid plant conditions are not the same as solar or power blocks separately. •We study potential for hybridization with current solar technologies. •Hybridization at the Brayton in a combined cycle may achieve high power/fuel ratio

  4. Manejo do cateter venoso central totalmente implantado em pacientes oncológicos: revisão integrative Manejo del catéter venoso central totalmente implantado en pacientes oncológicos: revisión integrativa Management of totally implanted catheter in patients with cancer: an integrative review

    Directory of Open Access Journals (Sweden)

    Christiane Inocêncio Vasques

    2009-10-01

    Full Text Available O cateter totalmente implantado é amplamente utilizado durante o tratamento de pacientes com câncer e é capaz de minimizar complicações decorrentes da terapia intravenosa periférica. Assim, buscou-se identificar os cuidados de enfermagem relacionados ao manuseio de cateter totalmente implantado nesses pacientes. Para tanto, realizou-se revisão integrativa da literatura que resultou na análise de 15 artigos. O conhecimento produzido está direcionado para o tempo de permanência do cateter, complicações inerentes ao uso, manuseio do dispositivo, percepção do paciente em relação ao cateter e informações ao paciente. Além de demonstrar a complexidade da assistência de enfermagem no manuseio desses dispositivos, os achados podem auxiliar, igualmente, os profissionais que não atuam em oncologia, na aplicação de conhecimentos na prática clínica.El catéter totalmente implantado es ampliamente utilizado durante el tratamiento de pacientes con cáncer y es capaz de minimizar las complicaciones consecuentes de la terapia intravenosa periférica. Así, en este trabajo, se buscó identificar los cuidados de enfermería relacionados a la manipulación del catéter totalmente implantado en esos pacientes. Para tal efecto, se realizó una revisión integrativa de la literatura dando como resultado el análisis de 15 artículos. El conocimiento producido está orientado hacia el tiempo de permanencia del catetér, complicaciones inherentes al uso, manipulación del dispositivo, informaciones y percepción del paciente en relación al catéter. Aparte de demostrar la complejidad de la asistencia de enfermería en la manipulación de esos dispositivos, los hallazgos pueden auxiliar, igualmente, a los profesionales que no actúan en oncología, en la aplicación de conocimientos en la práctica clínica.Totally implanted catheter, which is effective in deceasing complications related to peripheral intravenous therapy, is widely used in

  5. Performance improvement options for the supercritical carbon dioxide brayton cycle

    International Nuclear Information System (INIS)

    The supercritical carbon dioxide (S-CO2) Brayton cycle is under development at Argonne National Laboratory as an advanced power conversion technology for Sodium-Cooled Fast Reactors (SFRs) as well as other Generation IV advanced reactors as an alternative to the traditional Rankine steam cycle. For SFRs, the S-CO2 Brayton cycle eliminates the need to consider sodium-water reactions in the licensing and safety evaluation, reduces the capital cost of the SFR plant, and increases the SFR plant efficiency. Even though the S-CO2 cycle has been under development for some time and optimal sets of operating parameters have been determined, those earlier development and optimization studies have largely been directed at applications to other systems such as gas-cooled reactors which have higher operating temperatures than SFRs. In addition, little analysis has been carried out to investigate cycle configurations deviating from the selected 'recompression' S-CO2 cycle configuration. In this work, several possible ways to improve S-CO2 cycle performance for SFR applications have been identified and analyzed. One set of options incorporates optimization approaches investigated previously, such as variations in the maximum and minimum cycle pressure and minimum cycle temperature, as well as a tradeoff between the component sizes and the cycle performance. In addition, the present investigation also covers options which have received little or no attention in the previous studies. Specific options include a 'multiple-recompression' cycle configuration, intercooling and reheating, as well as liquid-phase CO2 compression (pumping) either by CO2 condensation or by a direct transition from the supercritical to the liquid phase. Some of the options considered did not improve the cycle efficiency as could be anticipated beforehand. Those options include: a double recompression cycle, intercooling between the compressor stages, and reheating between the turbine stages. Analyses carried

  6. Brayton-Cycle Baseload Power Tower CSP System

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Bruce

    2013-12-31

    The primary objectives of Phase 2 of this Project were: 1. Engineer, fabricate, and conduct preliminary testing on a low-pressure, air-heating solar receiver capable of powering a microturbine system to produce 300kWe while the sun is shining while simultaneously storing enough energy thermally to power the system for up to 13 hours thereafter. 2. Cycle-test a high-temperature super alloy, Haynes HR214, to determine its efficacy for the system’s high-temperature heat exchanger. 3. Engineer the thermal energy storage system This Phase 2 followed Wilson’s Phase 1, which primarily was an engineering feasibility study to determine a practical and innovative approach to a full Brayton-cycle system configuration that could meet DOE’s targets. Below is a summary table of the DOE targets with Wilson’s Phase 1 Project results. The results showed that a Brayton system with an innovative (low pressure) solar receiver with ~13 hours of dry (i.e., not phase change materials or molten salts but rather firebrick, stone, or ceramics) has the potential to meet or exceed DOE targets. Such systems would consist of pre-engineered, standardized, factory-produced modules to minimize on-site costs while driving down costs through mass production. System sizes most carefully analyzed were in the range of 300 kWe to 2 MWe. Such systems would also use off-the-shelf towers, blowers, piping, microturbine packages, and heliostats. Per DOE’s instructions, LCOEs are based on the elevation and DNI levels of Daggett, CA, for a 100 MWe power plant following 2 GWe of factory production of the various system components. Success criteria DOE targets Wilson system LCOE DOE’s gas price $6.75/MBtu 9 cents/kWh 7.7 cents/kWh LCOE Current gas price $4.71/MBtu NA 6.9 cents/kWh Capacity factor 75% (6500hr) 75-100% Solar fraction 85% (5585hr) >5585hr Receiver cost $170/kWe $50/kWe Thermal storage cost $20/kWhth $13/kWhth Heliostat cost $120/m2 $89.8/m2

  7. Ciclos reais brasileiros em dois setores

    Directory of Open Access Journals (Sweden)

    Fabio Kanczuk

    2004-03-01

    Full Text Available Construímos um modelo de equilíbrio geral dinâmico de dois setores com o intuito de investigar o comportamento dos ciclos reais brasileiros. Quando os investimentos dos dois setores são agregados de acordo com uma Cobb-Douglas para formação de capital, o modelo é consistente com as volatilidades cíclicas dos componentes das contas nacionais e com a natureza contracíclica das exportações líquidas e do câmbio real. Caso a elasticidade de substituição entre o consumo de comercializáveis e de não comercializáveis seja baixa, o modelo também reproduz a volatilidade observada no câmbio real.We construct a two-sector dynamic general equilibrium model to investigate the behavior of the Brazilian business cycles. When investments from each sector are aggregated according to a Cobb-Douglas for capital formation, the model is consistent with the cyclical volatilities of national income components as well as with the countercyclical character of net exports and real exchange rates. If the elasticity of substitution between consumptions of tradeables and non-tradeables is low, the model can also reproduce the observed real exchange rates volatilities.

  8. Neon turbo-Brayton cycle refrigerator for HTS power machines

    Science.gov (United States)

    Hirai, Hirokazu; Hirokawa, M.; Yoshida, Shigeru; Nara, N.; Ozaki, S.; Hayashi, H.; Okamoto, H.; Shiohara, Y.

    2012-06-01

    We developed a prototype turbo-Brayton refrigerator whose working fluid is neon gas. The refrigerator is designed for a HTS (High Temperature Superconducting) power transformer and its cooling power is more than 2 kW at 65 K. The refrigerator has a turboexpander and a turbo-compressor, which utilize magnetic bearings. These rotational machines have no rubbing parts and no oil-components. Those make a long maintenance interval of the refrigerator. The refrigerator is very compact because our newly developed turbo-compressor is volumetrically smaller than a displacement type compressor in same operating specification. Another feature of the refrigerator is a wide range operation capability for various heat-loads. Cooling power is controlled by the input-power of the turbo-compressor instead of the conventional method of using an electric heater. The rotational speed of the compressor motor is adjusted by an inverter. This system is expected to be more efficient. We show design details, specification and cooling test results of the new refrigerator in this paper.

  9. Thermo-economic performance of HTGR Brayton power cycles

    International Nuclear Information System (INIS)

    High temperature reached in High and Very High Temperature Reactors (VHTRs) results in thermal efficiencies substantially higher than those of actual nuclear power plants. A number of studies mainly driven by achieving optimum thermal performance have explored several layout. However, economic assessments of cycle power configurations for innovative systems, although necessarily uncertain at this time, may bring valuable information in relative terms concerning power cycle optimization. This paper investigates the thermal and economic performance direct Brayton cycles. Based on the available parameters and settings of different designs of HTGR power plants (GTHTR-300 and PBMR) and using the first and second laws of thermodynamics, the effects of compressor inter-cooling and of the compressor-turbine arrangement (i.e., single vs. multiple axes) on thermal efficiency have been estimated. The economic analysis has been based on the El-Sayed methodology and on the indirect derivation of the reactor capital investment. The results of the study suggest that a 1-axis inter-cooled power cycle has a similar thermal performance to the 3-axes one (around 50%) and, what's more, it is substantially less taxed. A sensitivity study allowed assessing the potential impact of optimizing several variables on cycle performance. Further than that, the cycle components costs have been estimated and compared. (authors)

  10. A treatment of thermal efficiency improvement in the Brayton cycle

    International Nuclear Information System (INIS)

    So far, as the working fluid for power-generating plants, mainly water and air (combustion gas) have been used. In this study, in regeneration and isothermal compression processes being considered as the means for the efficiency improvement in Brayton cycle, the investigation of equivalent graphical presentation method with T-S diagrams, the introduction of the new characteristic number expressing the possibility of thermal efficiency improvement by regeneration, and the investigation of the effect of the difference of working fluid on thermal efficiency were carried out. Next, as the cycle approximately realizing isothermal compression process with condensation process, the super-critical pressure cycle with liquid phase compression was rated, and four working fluids, NH3, SO2, CO2 and H2O were examined as perfect gas and real gas. The advantage of CO2 regeneration for the thermal efficiency improvement was clarified by using the dimensionless characteristic number. The graphical presentation of effective work, the thermal efficiency improvement by regeneration, the thermal efficiency improvement by making compression process isothermal, the effect on thermal efficiency due to various factors and working fluids, the characteristic number by regeneration, and the application to real working fluids are reported. (Kako, I.)

  11. Calidad de vida y características psicológicas de una población de pacientes hipoacúsicos implantados quirúrgicamente con la Prótesis Totalmente Implantable

    OpenAIRE

    Cortijo Torres, Marta

    2016-01-01

    Valorar la calidad de vida de una población de pacientes que han sido implantados quirúrgicamente con la prótesis totalmente implantable de oído medio, y detectar sintomatología psicopatológica que pudiera suponer un obstáculo para la consecución de resultados en el proceso de adaptación al implante auditivo.

  12. Brayton isotope power system. Phase I (Ground demonstration system) configuration control document (CCD)

    Energy Technology Data Exchange (ETDEWEB)

    1975-09-25

    The Brayton Isotope Power System (BIPS) Ground Demonstration System (GDS) configuration is defined. The GDS is configured to be similar to a conceptual flight system design referred to herein as the BIPS Flight System (FS). The Brayton Isotope Power System is being developed by the ERDA as a 500 to 2000 W/sub e/, 7 year life 3.5 W/sub e/ per pound space power system. The system was a closed Brayton dynamic system to convert energy from an isotope heat source at a net efficiency exceeding 25%. This CCD is for the first phase of the ERDA program to have a qualified system ready for launch by June 30, 1981. Phase I is a 36 month effort to provide a conceptual design of the flight system and design, fabricate and test a ground demonstration system. The baseline system is predicated on using two of the multihundred-watt isotope heat sources being developed for the ERDA by GE. The Ground Demonstration System will simulate, as closely as possible, the Brayton Isotope Power Flight System and will utilize components and technology being developed by NASA for the Mini-Brayton rotating unit (AIRPHX), recuperator (AIRLA) and heat source assembly (GE). The Ground Demonstration System includes a performance test and a 1000-hour endurance test.

  13. Preliminary design of the supercritical CO2 Brayton cycle energy conversion system

    International Nuclear Information System (INIS)

    The supercritical CO2 Brayton cycle energy conversion system is presented as a promising alternative to the present Rankine cycle. The principal advantage of the S-CO2 gas is a good efficiency at a modest temperature and a compact size of its components. The S-CO2 Brayton cycle coupled to a SFR also excludes the possibilities of a SWR (Sodium-Water Reaction) which is a major safety-related event, so that the safety of a SFR can be improved. KAERI is conducting a feasibility study for the supercritical carbon dioxide (S-CO2) Brayton cycle power conversion system coupled to KALIMER(Korea Advanced LIquid MEtal Reactor). The purpose of this research is to develop S-CO2 Brayton cycle energy conversion systems and evaluate their performance when they are coupled to advanced nuclear reactor concepts of the type under investigation in the Generation IV Nuclear Energy Systems. This paper contains the research overview of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system

  14. Rotational accuracy of all-ceramic restorations on ceraone components =Liberdade rotacional de restaurações totalmente cerâmicas sobre componentes ceraone

    Directory of Open Access Journals (Sweden)

    Webster, Jacqueline et al.

    2005-01-01

    Full Text Available Objetivo: Este estudo avaliou a desadaptação interna de sistemas cerâmicos em prótese sobre implantes em relação à liberdade rotacional das restaurações após várias cocções da porcelana. Materiais e métodos: Foram analisados três sistemas cerâmicos: Procera AllCeram, In-Ceram e CeraOne sobre análogo e intermediário CeraOne. A liberdade rotacional foi medida com um dispositivo acoplado a um relógio comparador em quatro tempos: fase de coifa, após aplicação do corpo da porcelana e glaze, e após duas queimas adicionais. Os dados foram analisados por testes de Friedman, de Kruskal-Wallis e de Wilcoxon, α = 0,01. Resultados: As médias de liberdade rotacional em graus foram: 0,08 para In-Ceram/Análogo; 1,64 para Procera/ Intermediário; 1,72 para CeraOne/Intermediário; 1,88 para CeraOne/Análogo e 1,97 para Procera/Análogo. O sistema In-Ceram sobre o análogo apresentou níveis de liberdade rotacional dez a vinte vezes menores que CeraOne e Procera. Não houve diferença entre as fases de confecção da restauração para In-Ceram. O comportamento de CeraOne e Procera foi similar, com aumento da liberdade rotacional sobre intermediário e análogo com a progressão da confecção da restauração. A liberdade rotacional sobre intermediário foi menor que sobre análogo. Conclusão: A liberdade rotacional variou em função da etapa do processo de fabricação dependendo do sistema totalmente cerâmico.

  15. Herniorrafia inguinal laparoscópica totalmente extraperitoneal: vinte e sete complicações graves após 4565 operações consecutivas

    Directory of Open Access Journals (Sweden)

    Alberto Meyer

    2013-02-01

    Full Text Available OBJETIVO: identificar e avaliar as complicações do tratamento da hérnia inguinal com a colocação de tela totalmente extraperitoneal. MÉTODOS: Foram incluídos, em uma série consecutiva de 4565 reparos de hérnia laparoscópica, pacientes que haviam sido submetidos ao procedimento TEP entre janeiro de 2001 e janeiro de 2011. Os critérios de inclusão foram: diagnóstico com hérnia inguinal sintomática, incluindo recorrência após correção de hérnia inguinal e cirurgia prévia em abdômen inferior e pelve. Todos os pacientes > 18 anos de idade. Pacientes com hérnia encarcerada na urgência foram excluídos do estudo. RESULTADOS: Um total de 4565 hérnias foram incluídas no estudo. Ocorreram 27 complicações graves (0,6%: 12 hemorragias (0,25%, duas lesões da bexiga (0,04%, cinco oclusões (0,11%, quatro perfurações intestinais (0,09%, uma lesão da veia ilíaca (0,02%, uma lesão do nervo femoral (0,02%, duas lesões dos vasos deferentes (0,04% e dois óbitos (0,02% (embolia pulmonar, peritonite. CONCLUSÃO: A taxa de complicações com o procedimento TEP é baixa. Correção de hérnia laparoscópica é uma técnica reprodutível e confiável. Em nossa experiência, existem contraindicações para o procedimento de TEP. A técnica TEP deve ser minuciosa para evitar complicações intraoperatórias (diatermia bipolar. As complicações podem ocorrer mesmo após o cirurgião ter adquirido experiência substancial.

  16. Preliminary Failure Modes, Effects and Criticality Analysis (FMECA) of the conceptual Brayton Isotope Power System (BIPS) Flight System

    International Nuclear Information System (INIS)

    A failure modes, effects and criticality analysis (FMECA) was made of the Brayton Isotope Power System Flight System (BIPS-FS) as presently conceived. The components analyzed include: Mini-BRU; Heat Source Assembly (HSA); Mini-Brayton Recuperator (MBR); Space Radiator; Ducts and Bellows, Insulation System; Controls; and Isotope Heat Source (IHS)

  17. Cost and price estimate of Brayton and Stirling engines in selected production volumes

    Science.gov (United States)

    Fortgang, H. R.; Mayers, H. F.

    1980-01-01

    The methods used to determine the production costs and required selling price of Brayton and Stirling engines modified for use in solar power conversion units are presented. Each engine part, component and assembly was examined and evaluated to determine the costs of its material and the method of manufacture based on specific annual production volumes. Cost estimates are presented for both the Stirling and Brayton engines in annual production volumes of 1,000, 25,000, 100,000 and 400,000. At annual production volumes above 50,000 units, the costs of both engines are similar, although the Stirling engine costs are somewhat lower. It is concluded that modifications to both the Brayton and Stirling engine designs could reduce the estimated costs.

  18. Exergy analyses of an endoreversible closed regenerative Brayton cycle CCHP plant

    Directory of Open Access Journals (Sweden)

    Bo Yang, Lingen Chen, Yanlin Ge, Fengrui Sun

    2014-01-01

    Full Text Available An endoreversible closed regenerative Brayton cycle CCHP (combined cooling, heating and power plant coupled to constant-temperature heat reservoirs is presented using finite time thermodynamics (FTT. The CCHP plant includes an endoreversible closed regenerative Brayton cycle, an endoreversible four-heat-reservoir absorption refrigerator and a heat recovery device of thermal consumer. The heat-resistance losses in the hot-, cold-, thermal consumer-, generator-, condenser-, evaporator- and absorber-side heat exchangers and regenerator are considered. The performance of the CCHP plant is studied from the exergetic perspective, and the analytical formulae about exergy output rate and exergy efficiency are derived. Through numerical calculations, the pressure ratio of regenerative Brayton cycle is optimized, the effects of heat conductance of regenerator and ratio of heat demanded by the thermal consumer to power output on dimensionless exergy output rate and exergy efficiency are analyzed.

  19. Thermodynamic design of 10 kW Brayton cryocooler for HTS cable

    Science.gov (United States)

    Chang, Ho-Myung; Park, C. W.; Yang, H. S.; Sohn, Song Ho; Lim, Ji Hyun; Oh, S. R.; Hwang, Si Dole

    2012-06-01

    Thermodynamic design of Brayton cryocooler is presented as part of an ongoing governmental project in Korea, aiming at 1 km HTS power cable in the transmission grid. The refrigeration requirement is 10 kW for continuously sub-cooling liquid nitrogen from 72 K to 65 K. An ideal Brayton cycle for this application is first investigated to examine the fundamental features. Then a practical cycle for a Brayton cryocooler is designed, taking into account the performance of compressor, expander, and heat exchangers. Commercial software (Aspen HYSYS) is used for simulating the refrigeration cycle with real fluid properties of refrigerant. Helium is selected as a refrigerant, as it is superior to neon in thermodynamic efficiency. The operating pressure and flow rate of refrigerant are decided with a constraint to avoid the freezing of liquid nitrogen

  20. Thermodynamic analysis of the double Brayton cycle with the use of oxy combustion and capture of CO2

    Science.gov (United States)

    Ziółkowski, Paweł; Zakrzewski, Witold; Kaczmarczyk, Oktawia; Badur, Janusz

    2013-06-01

    In this paper, thermodynamic analysis of a proposed innovative double Brayton cycle with the use of oxy combustion and capture of CO2, is presented. For that purpose, the computation flow mechanics (CFM) approach has been developed. The double Brayton cycle (DBC) consists of primary Brayton and secondary inverse Brayton cycle. Inversion means that the role of the compressor and the gas turbine is changed and firstly we have expansion before compression. Additionally, the workingfluid in the DBC with the use of oxy combustion and CO2 capture contains a great amount of H2O and CO2, and the condensation process of steam (H2O) overlaps in negative pressure conditions. The analysis has been done for variants values of the compression ratio, which determines the lowest pressure in the double Brayton cycle.

  1. Comparison of Direct and Indirect Gas Reactor Brayton Systems for Nuclear Electric Space Propulsion

    International Nuclear Information System (INIS)

    Gas reactor systems are being considered as candidates for use in generating power for the Prometheus-1 spacecraft, along with other NASA missions as part of the Prometheus program. Gas reactors offer a benign coolant, which increases core and structural materials options. However, the gas coolant has inferior thermal transport properties, relative to other coolant candidates such as liquid metals. This leads to concerns for providing effective heat transfer and for minimizing pressure drop within the reactor core. In direct gas Brayton systems, i.e. those with one or more Brayton turbines in the reactor cooling loop, the ability to provide effective core cooling and low pressure drop is further constrained by the need for a low pressure, high molecular weight gas, typically a mixture of helium and xenon. Use of separate primary and secondary gas loops, one for the reactor and one or more for the Brayton system(s) separated by heat exchanger(s), allows for independent optimization of the pressure and gas composition of each loop. The reactor loop can use higher pressure pure helium, which provides improved heat transfer and heat transport properties, while the Brayton loop can utilize lower pressure He-Xe. However, this approach requires a separate primary gas circulator and also requires gas to gas heat exchangers. This paper focuses on the trade-offs between the direct gas reactor Brayton system and the indirect gas Brayton system. It discusses heat exchanger arrangement and materials options and projects heat exchanger mass based on heat transfer area and structural design needs. Analysis indicates that these heat exchangers add considerable mass, but result in reactor cooling and system resiliency improvements

  2. Operational Curves for HTGR's Coupled to Closed Brayton Cycle Power Conversion Systems

    International Nuclear Information System (INIS)

    Gas Cooled Reactors (GCR) that drive Closed Brayton Cycle (CBC) systems are being evaluated by the Department of Energy (DOE) Next Generation Program for high-efficiency electricity generation. This paper describes the operational performance of measured and predicted closed Brayton cycles. The measured results were obtained from an electrically driven closed Brayton cycle test loop that Sandia fabricated and has operating within the laboratories. The predicted behavior is based on integrated dynamic system models that are capable of predicting both the transient and steady state behavior of reactor driven Brayton cycle systems. Sandia contracted Barber Nichols Corporation to modify a Capstone C30 open-cycle Brayton engine so that it could be operated in a closed loop. We are currently operating the test loop to validate the models and to study control issues. Operation of the test-loop and developing the system models has allowed Sandia to develop and validate a set of tools and models that are being used to determine how nuclear reactors operate with gas turbine power conversion systems. Both measured and modeled operational performance curves will be presented to show how the electrical load (or power generated) varies as a function of shaft speed for various turbine inlet temperatures and for a fixed fill gas inventory. The measured and modeled behavior of the test loop both reveal the non-linear nature of the reactor and Brayton cycle loop because for a fixed electrical load there are two shaft speeds that can produce this steady-state power. Closer examination of the system of equations shows that only one of these steady-state solutions is dynamically stable. An active electronic control system will be required to operate at the more efficient but dynamically unstable point, and some means of controlling the flow via inventory control or bypass flow valves will also be required. (authors)

  3. Volatile organic compound recovery by Brayton cycle Heat Pump

    International Nuclear Information System (INIS)

    Organic solvent emissions from industrial processes are a major source of volatile organic compounds (VOCs). VOCs contribute to the formation of photochemical ozone, a major component of smog. Over 90 percent of the organic solvents used in industry are emitted. Not only does this represent a significant source of air pollution, but it also represents a waste of energy resources. A pound of solvent requires an average of 23,000 Btu of energy to produce, in the form of the feedstock and processing energy expenditures. In 1988, the total amount of solvents emitted in the United States was over 4 billion pounds and represent 100 trillion Btu in energy loss. In the mid-1970's, the 3M Company began developing the Brayton Cycle Heat Pump for solvent recovery (BCSRHP). In 1979, the US Department of Energy (DOE) began a project to fabricate and install a BCSRHP in a 3M plant in Hutchinson, Minnesota. DOE has continued sponsoring the development of a large BCSRHP system with 3M, and NUCON International (NUCON). In 1989 DOE and NUCON, with cosponsorship from the Electric Power Research Institute and Southern California Edison Company began development of a small-scale system for use by small emitters. To obtain data for design of the small-scale system, a small, mobile pilot plant was built by NUCON. Between 1990 and 1991, the pilot plant was demonstrated at four industrial sites in Southern California. The operation of the pilot plant was continuously monitored during the demonstrations, and its ability to remove VOCS, utility consumption and other operating characteristics were recorded and its performance quantified

  4. Concept definition study of small Brayton cycle engines for dispersed solar electric power systems

    Science.gov (United States)

    Six, L. D.; Ashe, T. L.; Dobler, F. X.; Elkins, R. T.

    1980-01-01

    Three first-generation Brayton cycle engine types were studied for solar application: a near-term open cycle (configuration A), a near-term closed cycle (configuration B), and a longer-term open cycle (configuration C). A parametric performance analysis was carried out to select engine designs for the three configurations. The interface requirements for the Brayton cycle engine/generator and solar receivers were determined. A technology assessment was then carried out to define production costs, durability, and growth potential for the selected engine types.

  5. NASA 30,000 hour test demonstration of closed Brayton cycle reliability

    Science.gov (United States)

    Mccormick, J. E.; Dunn, J. H.

    1977-01-01

    Four Brayton rotating units (BRU) developed by an American company were tested in connection with studies concerning the feasibility to use closed Brayton power conversion systems for space applications. The rotating assembly operates at a speed of 36,000 rpm and consists of a radial outflow compressor, a four-pole Rice alternator/motor, and a radial inflow turbine. The cycle working fluid consists of a mixture of helium and xenon. After 20,000 hours of operation, there was no apparent wear on failure mode to prevent attainment of the 5-year BRU design life objective.

  6. Exergy Analysis and Second Law Efficiency of a Regenerative Brayton Cycle with Isothermal Heat Addition

    Directory of Open Access Journals (Sweden)

    Naser M. Jubeh

    2005-07-01

    Full Text Available Abstract: The effect of two heat additions, rather than one, in a gas turbine engine is analyzed from the second law of thermodynamics point of view. A regenerative Brayton cycle model is used for this study, and compared with other models of Brayton cycle. All fluid friction losses in the compressor and turbine are quantified by an isentropic efficiency term. The effect of pressure ratio, turbine inlet temperature, ambient temperature, altitude, and altitude with variable ambient temperature on irreversibility "exergy destroyed" and second law efficiency was investigated and compared for all models. The results are given graphically with the appropriate discussion and conclusion.

  7. Ciclos electorales en política fiscal

    OpenAIRE

    Lema, Daniel; Streb, Jorge M.

    2013-01-01

    Primero usamos casos empíricos concretos para motivar la discusión de los ciclos electorales en política fiscal. Luego presentamos una revisión teórica y econométrica de la literatura. Teóricamente, los ciclos se pueden interpretar en términos de un problema de inconsistencia temporal que enfrentan los gobiernos bajo información asimétrica: no es creíble que los gobiernos respeten una regla de presupuesto equilibrado antes de las elecciones, a menos que existan actores de veto legislativos qu...

  8. Computational analysis of supercritical CO2 Brayton cycle power conversion system for fusion reactor

    International Nuclear Information System (INIS)

    Highlights: ► Computational analysis of S-CO2 Brayton cycle power conversion system. ► Validation of numerical model with literature data. ► Recompression S-CO2 Brayton cycle thermal efficiency of 42.44%. ► Reheating concept to enhance the cycle thermal efficiency. ► Higher efficiency achieved by the proposed concept. - Abstract: The Optimized Supercritical Cycle Analysis (OSCA) code is being developed to analyze the design of a supercritical carbon dioxide (S-CO2) driven Brayton cycle for a fusion reactor as part of the Modular Optimal Balance Integral System (MOBIS). This system is based on a recompression Brayton cycle. S-CO2 is adopted as the working fluid for MOBIS because of its easy availability, high density and low chemical reactivity. The reheating concept is introduced to enhance the cycle thermal efficiency. The helium-cooled lithium lead model AB of DEMO fusion reactor is used as reference in this paper.

  9. Experimental and Analytical Performance of a Dual Brayton Power Conversion System

    Science.gov (United States)

    Lavelle, Thomas A.; Hervol, David S.; Briggs, Maxwell; Owen, A. Karl

    2009-01-01

    The interactions between two closed Brayton cycle (CBC) power conversion units (PCU) which share a common gas inventory and heat source have been studied experimentally using the Dual Brayton Power Conversion System (DBPCS) and analytically using the Closed- Cycle System Simulation (CCSS) computer code. Selected operating modes include steady-state operation at equal and unequal shaft speeds and various start-up scenarios. Equal shaft speed steady-state tests were conducted for heater exit temperatures of 840 to 950 K and speeds of 50 to 90 krpm, providing a system performance map. Unequal shaft speed steady-state testing over the same operating conditions shows that the power produced by each Brayton is sensitive to the operating conditions of the other due to redistribution of gas inventory. Startup scenarios show that starting the engines one at a time can dramatically reduce the required motoring energy. Although the DBPCS is not considered a flight-like system, these insights, as well as the operational experience gained from operating and modeling this system provide valuable information for the future development of Brayton systems.

  10. Specification requirements summary for the Brayton Isotope Power System (BIPS) Ground Demonstration System (GDS)

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, E.E.

    1976-02-10

    This document provides a summary of the required program specifications and procedures for the ERDA Phase I Brayton Isotope Power System (BIPS) Program. Also included are document definitions, descriptions, and formats, and a listing of commonly used abbreviations. This document is intended to be used as a guide in document preparation and control.

  11. Overview of CNES-CEA joint program on space nuclear Brayton systems

    International Nuclear Information System (INIS)

    In this paper French studies on 20-kWe space nuclear power systems are presented. The gas-cooled reactor nuclear systems, some investigations on advanced thermal neutron spectrum systems, a support work on materials, parameters optimization and operating transient analysis, and Brayton cycle-thermoelectric and nuclear-non nuclear systems comparisons

  12. Brayton-Cycle Heat Recovery System Characterization Program. Glass-furnace facility test plan

    Energy Technology Data Exchange (ETDEWEB)

    1980-08-29

    The test plan for development of a system to recover waste heat and produce electricity and preheated combustion air from the exhaust gases of an industrial glass furnace is described. The approach is to use a subatmospheric turbocompressor in a Brayton-cycle system. The operational furnace test requirements, the operational furnace environment, and the facility design approach are discussed. (MCW)

  13. Influence of irreversible losses on the performance of a two-stage magnetic Brayton refrigeration cycle

    International Nuclear Information System (INIS)

    The general performance characteristics of a two-stage magnetic Brayton refrigeration cycle consisting of three constant magnetic fields and three irreversible adiabatic processes are investigated. Based on the thermodynamic properties of a magnetic material and the irreversible cycle model of a two-stage Brayton refrigerator, expressions for the cooling load and coefficient of performance of the refrigeration system are derived. The influence of the finite-rate heat transfer in the heat exchange processes, irreversibilities in the three adiabatic processes, ratios of two magnetic fields in the three constant magnetic field processes, and heat leak losses between two heat reservoirs on the performance of the two-stage magnetic Brayton refrigeration cycle are analyzed in detail. Some important performance curves, which can reveal the general characteristics of the refrigeration system, are presented and the maximum values of cooling load and coefficient of performance are numerically calculated. The optimal choices and matches of other parameters at the maximum cooling load or the maximum coefficient of performance are discussed and the optimally operating regions of some important parameters in the refrigeration system are determined. The results obtained here are compared with those derived from other models of the magnetic Brayton refrigeration cycles, and consequently, the advantage of an inter-cooled process is expounded.

  14. Isotope Brayton ground demonstration testing and flight qualification program. Volume 1. Technical program

    Energy Technology Data Exchange (ETDEWEB)

    1974-12-09

    A proposal for the demonstration, development and production of the Isotope Brayton Flight System for space vehicles is presented with details on the technical requirements for designing and testing a ground demonstration system and on the program organization and personnel. (LCL)

  15. Sensitivity study on nitrogen Brayton cycle coupled with a small ultra-long cycle fast reactor

    International Nuclear Information System (INIS)

    The main characteristics of UCFR are constant neutron flux and power density. They move their positions every moment at constant speed along with axial position of fuel rod for 60 years. Simultaneously with the development of the reactors, a new power conversion system has been considered. To solve existing issues of vigorous sodium-water reaction in SFR with steam power cycle, many researchers suggested a closed Brayton cycle as an alternative technique for SFR power conversion system. Many inactive gases are selected as a working fluid in Brayton power cycle, mainly supercritical CO2 (S-CO2). However, S-CO2 still has potential for reaction with sodium. CO2-sodium reaction produces solid product, which has possibility to have an auto ignition reaction around 600 .deg. C. Thus, instead of S-CO2, CEA in France has developed nitrogen power cycle for ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration). In addition to inactive characteristic of nitrogen with sodium, its thermal and physical similarity with air enables to easily adopt to existing air Brayton cycle technology. In this study, for an optimized power conversion system for UCFR, a nitrogen Brayton cycle was analyzed in thermodynamic aspect. Based on subchannel analysis data of UCFR-100, a parametric study for thermal performance of nitrogen Brayton cycle was achieved. The system maximum pressure significantly affects to the overall efficiency of cycle, while other parameters show little effects. Little differences of the overall efficiencies for all cases between three stages (BOC, MOC, EOC) indicate that the power cycle of UCFR-100 maintains its performance during the operation

  16. Hydrological cycle Ciclo hidrológico

    Directory of Open Access Journals (Sweden)

    HC Gonçalves

    2011-04-01

    Full Text Available The Pantanal hydrological cycle holds an important meaning in the Alto Paraguay Basin, comprising two areas with considerably diverse conditions regarding natural and water resources: the Plateau and the Plains. From the perspective of the ecosystem function, the hydrological flow in the relationship between plateau and plains is important for the creation of reproductive and feeding niches for the regional biodiversity. In general, river declivity in the plateau is 0.6 m/km while declivity on the plains varies from 0.1 to 0.3 m/km. The environment in the plains is characteristically seasonal and is home to an exuberant and abundant diversity of species, including some animals threatened with extinction. When the flat surface meets the plains there is a diminished water flow on the riverbeds and, during the rainy season the rivers overflow their banks, flooding the lowlands. Average annual precipitation in the Basin is 1,396 mm, ranging from 800 mm to 1,600 mm, and the heaviest rainfall occurs in the plateau region. The low drainage capacity of the rivers and lakes that shape the Pantanal, coupled with the climate in the region, produce very high evaporation: approximately 60% of all the waters coming from the plateau are lost through evaporation. The Alto Paraguay Basin, including the Pantanal, while boasting an abundant availability of water resources, also has some spots with water scarcity in some sub-basins, at different times of the year. Climate conditions alone are not enough to explain the differences observed in the Paraguay River regime and some of its tributaries. The complexity of the hydrologic regime of the Paraguay River is due to the low declivity of the lands that comprise the Mato Grosso plains and plateau (50 to 30 cm/km from east to west and 3 to 1.5 cm/km from north to south as well as the area's dimension, which remains periodically flooded with a large volume of water.O ciclo hidrológico do Pantanal guarda um significado

  17. Parametric Investigation and Thermoeconomic Optimization of a Combined Cycle for Recovering the Waste Heat from Nuclear Closed Brayton Cycle

    Directory of Open Access Journals (Sweden)

    Lihuang Luo

    2016-01-01

    Full Text Available A combined cycle that combines AWM cycle with a nuclear closed Brayton cycle is proposed to recover the waste heat rejected from the precooler of a nuclear closed Brayton cycle in this paper. The detailed thermodynamic and economic analyses are carried out for the combined cycle. The effects of several important parameters, such as the absorber pressure, the turbine inlet pressure, the turbine inlet temperature, the ammonia mass fraction, and the ambient temperature, are investigated. The combined cycle performance is also optimized based on a multiobjective function. Compared with the closed Brayton cycle, the optimized power output and overall efficiency of the combined cycle are higher by 2.41% and 2.43%, respectively. The optimized LEC of the combined cycle is 0.73% lower than that of the closed Brayton cycle.

  18. The role of real gas Brayton cycles for the use of liquid natural gas physical exergy

    International Nuclear Information System (INIS)

    When using the cooling capacity of LNG several thermodynamic schemes are proposable employing conventional and non conventional conversion cycles. All conventional systems make use of organic working fluids such as methane or propane in series of Rankine cycles used in a cascading mode. A simpler system is available, using a single cycle and a single fluid in a Brayton cycle. However ordinary Brayton cycles exhibit a modest efficiency. Resorting to Brayton cycles with strong real gas effects (which is possible selecting the base parameters of pressure and temperature in the vicinity of the critical point) improves considerable cycle performance. Since the level of cold in a LNG flow is thermodynamically predetermined, working fluids must be selected with a critical point which fit the LNG thermal capacity, i.e. some 5-15 C higher than the usual LNG temperature which is around -160 oC. Nitrogen was found as the best fluid to exploit real gas effects with efficiencies above 63% while perfect gas cycles give efficiencies around 56%. However, in real gas cycles the cooling capacity of LNG is only partially exploited: a better exploitation is obtained from perfect gas cycles or for more complex cascading Rankine cycle. Selecting working fluids with a higher critical temperature than nitrogen, as for example argon, the efficiency decreases to 58% respect to 63% for nitrogen, but the utilization of the cold of LNG improves from 0.30 MW/(kg/s) to 0.75 MW/(kg/s). Obviously as heat rejection temperature increases a larger fraction of cold in the LNG flow can be utilized. Combined cycles making use of a gas turbine offer also a good performance. The merits of real gas effect Brayton cycles also in this case remains evident. Finally, it is theoretically possible to use real gas effect Brayton cycles at low temperatures, which are typical of waste heat (say 100-150 oC: in this case cycle efficiency remain good, but power obtainable from a unit flow of LNG is modest. - Research

  19. Comparison of Analytical Predictions and Experimental Results for a Dual Brayton Power System (Discussion on Test Hardware and Computer Model for a Dual Brayton System)

    Science.gov (United States)

    Johnson, Paul K.

    2007-01-01

    NASA Glenn Research Center (GRC) contracted Barber-Nichols, Arvada, CO to construct a dual Brayton power conversion system for use as a hardware proof of concept and to validate results from a computational code known as the Closed Cycle System Simulation (CCSS). Initial checkout tests were performed at Barber- Nichols to ready the system for delivery to GRC. This presentation describes the system hardware components and lists the types of checkout tests performed along with a couple issues encountered while conducting the tests. A description of the CCSS model is also presented. The checkout tests did not focus on generating data, therefore, no test data or model analyses are presented.

  20. Comparison of various Brayton cycles for a Sodium-cooled Fast Reactor

    International Nuclear Information System (INIS)

    The nuclear energy is considered as one of the most realistic energy sources for both reducing the carbon dioxide emission and attaining sufficient and stable electricity supply for economy development. As a part of the nuclear energy development, many countries around the world are focusing on the next generation reactor development. One of the next generation reactors that is seriously being considered is the Sodium-cooled Fast Reactor (SFR). However, current SFR design faces the difficulty in public acceptance due to the potential threat from sodium-water reaction (SWR) when the current conventional steam Rankine cycle is utilized as a power conversion system for SFR. To substitute the violent sodium-water reaction with milder or no reaction, several Brayton cycle concepts including the S-CO2 cycle, helium cycle and nitrogen cycle are considered by many research organizations. This paper discusses these Brayton cycles'performance for SFR application compared to the current steam Rankine cycle

  1. Phase 2 Brayton/Rankine 10-ton gas-fired space-conditioning system

    Science.gov (United States)

    1982-07-01

    The technical accomplishments to date in the design, development, and demonstration program leading to commercialization of a 10 ton heat actuated space conditioning system for light commercialization of a 10 ton heat actuated space conditioning system for light commercial building applications are summarized. The system consists of a natural gas powered Brayton cycle engine and a Rankine cycle heat pump, combined in a single roof top package. The heat actuated space conditioning system provides more efficient use of natural gas and is intended as an all gas alternative to the electric heat pump. The system employs a subatmospheric natural gas fired heat pump. A centrifugal R-12 refrigerant compressor is driven directly from the Brayton engine rotating group through a hermetically sealed coupling. Unique features that offer high life cycle performance include a permanent magnet coupling, foil bearings, an atmospheric in-line combustor, and a high temperature recuperator.

  2. Super-critical carbon dioxide based brayton cycle for Indian High Temperature Reactors

    International Nuclear Information System (INIS)

    The most effective way to improve economic competitiveness of NPPs is to enhance its efficiency which has remained static at around 33% since the first commercial LWR came into operation. New generation reactor designs including the six Gen-IV reactor concepts aim to increase the NPPs efficiency to almost 50%. This is proposed to be achieved by high temperature designs using Brayton cycle based power conversion systems. World over, Super-critical Carbon dioxide Brayton Cycle (SCBC) for power generation is an important R and D area. High efficiency SCBC power conversion system is proposed as power conversion system for Indian Molten Salt Breeder Reactor (IMSBR) and Innovative High Temperature Reactor (IHTR). This section provides the details regarding design and development of SCBC for these reactors. (author)

  3. Design Development Analyses in Support of a Heatpipe-Brayton Cycle Heat Exchanger

    Science.gov (United States)

    Steeve, Brian E.; Kapernick, Richard J.

    2004-01-01

    One of the power systems under consideration for nuclear electric propulsion or as a planetary surface power source is a heatpipe-cooled reactor coupled to a Brayton cycle. In this system, power is transferred from the heatpipes to the Brayton gas via a heat exchanger attached to the heatpipes. This paper discusses the fluid, thermal and structural analyses that were performed in support of the design of the heat exchanger to be tested in the SAFE-100 experimental program at the Marshall Space Flight Center: An important consideration throughout the design development of the heat exchanger w its capability to be utilized for higher power and temperature applications. This paper also discusses this aspect of the design and presents designs for specific applications that are under consideration.

  4. Optimum criteria of an irreversible quantum Brayton refrigeration cycle with an ideal Bose gas

    International Nuclear Information System (INIS)

    An irreversible cycle model of the quantum Brayton refrigeration cycle is established, in which finite-time processes and irreversibility in the two adiabatic processes are taken into account. On the basis of the thermodynamic properties of an ideal Bose gas, by using the optimal control-theory, the mathematical expressions for several important performance parameters, such as the coefficient of performance, power input and cooling load, are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of a Bose-Brayton refrigeration cycle are obtained and analyzed. Furthermore, some optimal operating regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail

  5. Supercritical carbon dioxide Brayton power conversion cycle for battery optimized reactor integral system

    International Nuclear Information System (INIS)

    Supercritical carbon dioxide (SCO2) promises a high power conversion efficiency of the recompression Brayton cycle due to its excellent compressibility reducing the compression work at the bottom of the cycle and to a higher density than helium or steam decreasing the component size. The SCO2 Brayton cycle efficiency as high as 45% furnishes small sized nuclear reactors with economical benefits on the plant construction and maintenance. A 23 MWth lead-cooled Battery Optimized Reactor Integral System (BORIS) is being developed as an ultra-long-life, versatile-purpose, fast-spectrum reactor. BORIS is coupled to the SCO2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO2 Brayton cycle of BORIS consists of a 16 MW turbine, a 32 MW high temperature recuperator, a 14 MW low temperature recuperator, an 11 MW precooler and 2 and 2.8 MW compressors. Entering six heat exchangers between primary and secondary system at 19.9 MPa and 663 K, the SCO2 leaves the heat exchangers at 19.9 MPa and 823 K. The promising secondary system efficiency of 45% was calculated by a theoretical method in which the main parameters include pressure, temperature, heater power, the turbine's, recuperators' and compressors' efficiencies, and the flow split ratio of SCO2 going out from the low temperature recuperator. Development of Modular Optimized Brayton Integral System (MOBIS) is being devised as the SCO2 Brayton cycle energy conversion cycle for BORIS. MOBIS consists of Loop Operating Brayton Optimization Study (LOBOS) for experimental Brayton cycle loop and Gas Advanced Turbine Operation Study (GATOS) for the SCO2 turbine. Liquid-metal Energy Exchanger Integral System (LEXIS) serves to couple BORIS and MOBIS. LEXIS comprises Physical Aspect Thermal Operation System (PATOS) for SCO2 thermal hydraulic characteristics, Shell-and-tube Overall Layout Optimization Study (SOLOS) for shell-and-tube heat exchanger, Printed-circuit Overall

  6. Supercritical CO2 Brayton Cycle Energy Conversion System Coupled with SFR

    International Nuclear Information System (INIS)

    This report contains the description of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For a system development, a computer code was developed to calculate heat balance of normal operation condition. Based on the computer code, the S-CO2 Brayton cycle energy conversion system was constructed for the KALIMER-600. Computer codes were developed to analysis for the S-CO2 turbomachinery. Based on the design codes, the design parameters were prepared to configure the KALIMER-600 S-CO2 turbomachinery models. A one-dimensional analysis computer code was developed to evaluate the performance of the previous PCHE heat exchangers and a design data for the typical type PCHE was produced. In parallel with the PCHE-type heat exchanger design, an airfoil shape fin PCHE heat exchanger was newly designed. The new design concept was evaluated by three-dimensional CFD analyses. Possible control schemes for power control in the KALIMER-600 S-CO2 Brayton cycle were investigated by using the MARS code. The MMS-LMR code was also developed to analyze the transient phenomena in a SFR with a supercritical CO2 Brayton cycle to develop the control logic. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na-CO2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO2 gas. The long term behavior of a Na-CO2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

  7. Techno-economic studies of environmentally friendly Brayton cycles in the petrochemical industry

    OpenAIRE

    Nkoi, Barinyima

    2014-01-01

    Brayton cycles are open gas turbine cycles extensively used in aviation and industrial applications because of their advantageous volume and weight characteristics. With the bulk of waste exhaust heat and engine emissions associated, there is need to be mindful of environmentally-friendliness of these engine cycles, not compromising good technical performance, and economic viability. This research considers assessment of power plants in helicopters, and aeroderivative ind...

  8. Ecological Optimization and Parametric Study of an Irreversible Regenerative Modified Brayton Cycle with Isothermal Heat Addition

    OpenAIRE

    Vivek Tiwari; Subhash Chandra Kaushik; Sudhir Kumar Tyagi

    2003-01-01

    Abstract: An ecological optimization along with a detailed parametric study of an irreversible regenerative Brayton heat engine with isothermal heat addition have been carried out with external as well as internal irreversibilities. The ecological function is defined as the power output minus the power loss (irreversibility) which is ambient temperature times the entropy generation rate. The external irreversibility is due to finite temperature difference between the heat engine and the exter...

  9. Preheating of fluid in a supercritical Brayton cycle power generation system at cold startup

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven A.; Fuller, Robert L.

    2016-07-12

    Various technologies pertaining to causing fluid in a supercritical Brayton cycle power generation system to flow in a desired direction at cold startup of the system are described herein. A sensor is positioned at an inlet of a turbine, wherein the sensor is configured to output sensed temperatures of fluid at the inlet of the turbine. If the sensed temperature surpasses a predefined threshold, at least one operating parameter of the power generation system is altered.

  10. A parametric study of motor starting for a 2- to 10-kilowatt Brayton power system

    Science.gov (United States)

    Cantoni, D. A.

    1971-01-01

    A study of the motor starting of a Brayton cycle power system was conducted to provide estimates of system sensitivity to several controllable parameters. These sensitivity estimates were used as a basis for selection of an optimum motor-start scheme to be implemented on the 2- to 10-kilowatt Brayton power system designed and presently under test. The studies were conducted with an analog simulation of the Brayton power system and covered a range of frequencies from 400 Hz (33 percent design) to 1200 Hz (design), voltage-to-frequency ratios of 0.050 (50 percent design) to 0.100 (design), turbine-inlet temperatures of 800 K (1440 R, 70 percent design) to 1140 K (2060 deg R, design), and prestart pressure levels of 14.5 psia to 29.0 psia. These studies have shown the effect of selected system variables on motor starting. The final selection of motor-start variables can therefore be made on the basis of motor-start inverter complexity, battery size and weight, desired steady-state pressure level after startup, and other operational limitations. In general, the study showed the time required for motor starting to be inversely proportional to motor frequency, voltage, turbine-inlet temperature, and pressure level. An increase in any of these parameters decreases startup time.

  11. Coupling a Supercritical Carbon Dioxide Brayton Cycle to a Helium-Cooled Reactor.

    Energy Technology Data Exchange (ETDEWEB)

    Middleton, Bobby [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pasch, James Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kruizenga, Alan Michael [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Walker, Matthew [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2016-01-01

    This report outlines the thermodynamics of a supercritical carbon dioxide (sCO2) recompression closed Brayton cycle (RCBC) coupled to a Helium-cooled nuclear reactor. The baseline reactor design for the study is the AREVA High Temperature Gas-Cooled Reactor (HTGR). Using the AREVA HTGR nominal operating parameters, an initial thermodynamic study was performed using Sandia's deterministic RCBC analysis program. Utilizing the output of the RCBC thermodynamic analysis, preliminary values of reactor power and of Helium flow rate through the reactor were calculated in Sandia's HelCO2 code. Some research regarding materials requirements was then conducted to determine aspects of corrosion related to both Helium and to sCO2 , as well as some mechanical considerations for pressures and temperatures that will be seen by the piping and other components. This analysis resulted in a list of materials-related research items that need to be conducted in the future. A short assessment of dry heat rejection advantages of sCO2> Brayton cycles was also included. This assessment lists some items that should be investigated in the future to better understand how sCO2 Brayton cycles and nuclear can maximally contribute to optimizing the water efficiency of carbon free power generation

  12. Brayton cycle conversion and additional French investigations on space nuclear power systems

    International Nuclear Information System (INIS)

    The French studies on space nuclear power systems were relatively active the past six years. It was anticipated that 20-kWe should have to be supplied to a spacecraft as soon as in 2005 and a reference near term liquid metal-cooled reactor using available terrestrial technologies as much as possible was mainly investigated. A Brayton cycle heat conversion has been adopted from the beginning and it remains considered. Because first applications are delayed, more attractive concepts can be contemplated. The basic idea is to take advantage of the Brayton cycle specific properties and for instance to use them for the temperature conditioning of the moderator of a thermal spectrum reactor. At first, the utilization of ZrH was thought mandatory, but recent proposals have prompted to use the conventional, effective light water material for that purpose. A gas cycle high pressure (HP) derivation technique makes it possible to maintain water within an adequate temperature range. A Brayton cycle adaptation and an example of a gas-cooled, particle bed fuel elements, H2O moderated reactor are briefly described. Key comparison data are given. Such concepts should be attractive from fuel inventory, mass, radition shielding and control points of view

  13. Brayton cycle conversion system and temperature conditioning of small space nuclear reactors

    International Nuclear Information System (INIS)

    A companion paper (Carre et al. 1989) presented at this symposium gives an overview of the French preliminary studies on space nuclear power systems in progress within the framework of a three-year (1986-1989) program. Other papers (Proust et al. 1988, Tilliette et al. 1988, Tilliette IECEC 1988) supplement the information on this activity. Low power levels of about 20-KWe and both liquid metal- and gas-cooled reactors are concerned. The Brayton cycle is currently selected as the conversion subsystem. Critical issues like safety, reliability, radiation shielding and reactor concept and technology have to be addressed more and more carefully and relevant temperature conditions are crucial. It is shown in this paper that the Brayton cycle can offer a valuable flexibility which allows the desired thermal environment. For instance, it is possible to significantly decrease the reactor inlet temperature and consequently, also given an adequate design, to favourably put forward convenient solutions for the lateral and axial bottom reflector, the shadow shield, the control drums drives and safety rods actuators and penetrations as well as for the possibility of using efficient moderator materials like metal hydrides (ZrH or 7LiH), which is worth being investigated as far as low power levels are concerned. Examples of Brayton cycle conversion subsystems and possible reactor arrangements are presented for both gas-cooled and liquid metal (NaK or Na)-cooled reactor heat sources. The study follows up the research described by Thilliette (1988, IECEC)

  14. Compressor and Turbine Models of Brayton Units for Space Nuclear Power Systems

    Science.gov (United States)

    Gallo, Bruno M.; El-Genk, Mohamed S.; Tournier, Jean-Michel

    2007-01-01

    Closed Brayton Cycles with centrifugal flow, single-shaft turbo-machines are being considered, with gas cooled nuclear reactors, to provide 10's to 100's of electrical power to support future space exploration missions and Lunar and Mars outposts. Such power system analysis is typically based on the cycle thermodynamics, for given operating pressures and temperatures and assumed polytropic efficiencies of the compressor and turbine of the Brayton energy conversion units. Thus the analysis results not suitable for modeling operation transients such as startup and changes in the electric load. To simulate these transients, accurate models of the turbine and compressor in the Brayton rotating unit, which calculate the changes in the compressor and turbine efficiencies with system operation are needed. This paper presents flow models that account for the design and dimensions of the compressor impeller and diffuser, and the turbine stator and rotor blades. These models calculate the various enthalpy losses and the polytropic efficiencies along with the pressure ratios of the turbine and compressor. The predictions of these models compare well with reported performance data of actual hardware. In addition, the results of a parametric analysis to map the operations of the compressor and turbine, as functions of the rotating shaft speed and inlet Mach number of the gas working fluid, are presented and discussed. The analysis used a binary mixture of He-Xe with a molecular weight of 40 g/mole as the working fluid.

  15. Optimal analysis on the performance of an irreversible harmonic quantum Brayton refrigeration cycle.

    Science.gov (United States)

    Lin, Bihong; Chen, Jincan

    2003-11-01

    An irreversible model of a quantum refrigeration cycle working with many noninteracting harmonic oscillators is established. The refrigeration cycle consists of two adiabatic and two constant-frequency processes. The general performance characteristics of the cycle are investigated, based on the quantum master equation and the semigroup approach. The expressions for several important performance parameters such as the coefficient of performance, cooling rate, power input, and rate of entropy production are derived. By using numerical solutions, the cooling rate of the refrigeration cycle subject to finite cycle duration is optimized. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal region of the coefficient of performance and the optimal ranges of temperatures of the working substance and times spent on the two constant-frequency processes are determined. Moreover, the optimal performance of the cycle in the high-temperature limit is compared with that of a classical Brayton refrigerator working with an ideal gas. The results obtained here show that in the high-temperature limit a harmonic quantum Brayton cycle may be equivalent to a classical Brayton cycle. PMID:14682856

  16. The Brayton Cycle heat pump for solvent recovery and pollution control

    International Nuclear Information System (INIS)

    The Brayton Cycle heat pump technology for the recovery of solvent and prevention of emissions is relatively new. Like most new technologies, it is a combination of older concepts, ideas and types of processes put together in a unique way. As a result, proven equipment enables achievement of extremely low condensing temperatures at relatively low cost. The Brayton Cycle is a thermodynamic principle. It was used first for a turbine engine, but more recently it has been used for a variety of other kinds of processes including refrigeration. A great variety of methods are used for emission control including adsorption, direct condensation, absorption in a fluid, and incineration or destruction. The Brayton Cycle technology actually fits into two of these categories, adsorption and direct condensation. Since it is a refrigeration process, it can be used to condense solvents from a solvent-laden air stream. The advantage of this particular process over other refrigeration methods is that lower temperatures can be achieved more easily. In fact, temperatures as low as -150 degrees F have been used to recover solvents in this manner. That happens to be the freezing point of methylene chloride which is a very volatile compound. High recovery efficiencies can be obtained for a whole variety of organic materials. 8 figs., 1 tab

  17. Nuclear reactor closed Brayton cycle power conversion system optimization trends for extra-terrestrial applications

    International Nuclear Information System (INIS)

    Extra-terrestrial exploration and development missions of the next century will require reliable, low-mass power generation modules of 100 kWe and more. These modules will be required to support both fixed-base and manned rover/explorer power needs. Low insolation levels at and beyond Mars and long periods of darkness on the moon make solar conversion less desirable for surface missions. For these missions, a closed Brayton cycle energy conversion system coupled with a reactor heat source is a very attractive approach. The authors conducted parametric studies to assess optimized system design trends for nuclear-Brayton systems as a function of operating environment and user requirements. The inherent design flexibility of the closed Brayton cycle energy conversion system permits ready adaptation of the system to future design constraints. This paper describes a dramatic contrast between system designs requiring man-rated shielding. The paper also considers the ramification of using indigenous materials to provide reactor shielding for a fixed-base power source

  18. Performance analysis and parametric optimal criteria of an irreversible magnetic Brayton-refrigerator

    International Nuclear Information System (INIS)

    An irreversible magnetic Brayton refrigeration-cycle model is established, in which the thermal resistance and irreversibility in the two adiabatic processes are taken into account. Based on the model, the performance characteristics of the magnetic Brayton refrigeration-cycle are investigated and the effects of the irreversibilities and the ratio of the magnetic fields in the two iso-field processes on the performance of the refrigeration cycle are revealed. On the basis of the thermodynamic properties of a paramagnetic material, by using the optimal control-theory, the mathematical expressions for the cooling load and the coefficient of performance are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of the magnetic Brayton refrigeration-cycle are obtained and analyzed. Furthermore, some optimal operating-regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail

  19. Determinantes y caracteristicas de los ciclos economicos en Mexico y estimacion del PIB potencial

    OpenAIRE

    Cecilia Posadas; Ociel Hernandez

    2007-01-01

    En un entorno en el que la prolongada estabilidad en los ciclos economicos de nuestro principal socio comercial es tema de gran debate por la incertidumbre que genera su sostenibilidad, conviene analizar el tema de los ciclos y el crecimiento potencial de nuestra economia considerando los cambios en la estructura productiva en los anos posteriores a la entrada en vigor del TLCAN. El presente texto se divide en dos partes; en la primera, dedicada a los ciclos economicos, se especula sobre las ...

  20. Afrontamiento, resiliencia y bienestar a lo largo del ciclo vital

    OpenAIRE

    Mayordomo Rodriguez, Teresa

    2013-01-01

    El ser humano a lo largo del ciclo vital se enfrenta situaciones y sucesos para los que debe poner en marcha estrategias de afrontamiento que faciliten su adaptación y generen bienestar. La mayoría de los teóricos del afrontamiento (Carver, Scheier y Weintraub, 1989; Lazarus y Folkman, 1984; Moos, 1988; Moos y Billing, 1982), concuerdan en clasificar tres dominios generales de las estrategias según cómo éstas estén dirigidas a: la valoración (afrontamiento cognitivo), un intento de encontr...

  1. Trocas gasosas e ciclo fotossintético da figueira 'Roxo de Valinhos' Gas exchanges and cycle fhotosynthetic in fig tree 'Roxo de Valinhos'

    Directory of Open Access Journals (Sweden)

    Andréa Carvalho da Silva

    2010-06-01

    Full Text Available No presente trabalho, determinaram-se as trocas gasosas de folhas de figueira 'Roxo de valinhos' e o ciclo fotossintético por meio da relação isotópica 12C/13C. Essas medidas foram realizadas sempre na região mediana das folhas, completamente expandidas e totalmente expostas à radiação solar, no período das 09h00min às 10h30min. As folhas fotossinteticamente ativas da figueira apresentaram área foliar em torno de 160cm², com uma assimilação de 14,38µmol m-2 s-1 de CO2, cujos valores isotópicos médios no ramo 1 e no 2 são -28,98±0,69‰ e -29,28±0,85‰, respectivamente. Com base nos valores da fotossíntese máxima e na discriminação isotópica do 13C, evidenciou-se que a figueira pode ser considerada uma planta do ciclo fotossintético C3.In the present research, it was determined the gas exchange of the 'Roxo de Valinhos' fig tree and the cycle photosynthetic through the isotopic relation 12C/13C. These measures were always carried in the average region of the leaves, completely expanded, entirely displayed to the solar radiation, in the period from 09h00min to 10h30min. The sheets photosynthetic active leaf area had around 160cm², with 14.38 -2 s-1 assimilation CO2, and mean isotopic values in the branch 1 and 2 of -28.98±0.69‰ and -29.28±0,85‰, respectively. Based in the values of the maximum photosynthesis and in the discrimination isotopic of the 13C, the fig tree can be considered a plant which belongs to photosynthetic C3 cycle.

  2. Solar (superíndice) 2, remisión de V. ciclo solar .

    OpenAIRE

    2011-01-01

    [ES] Definición del término Solar (superíndice) 2, remisión de V. ciclo solar . en el diccionario Dicter. [EN] Definition of the word Solar (superíndice) 2, remisión de V. ciclo solar . in the dictionary Dicter.

  3. Preliminary Design of S-CO{sub 2} Brayton Cycle for KAIST Micro Modular Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong Gu; Kim, Min Gil; Bae, Seong Jun; Lee, Jeong Ik [Korea Advanced Institue of Science and Technology, Daejeon (Korea, Republic of)

    2013-10-15

    This paper suggests a complete modular reactor with an innovative concept of reactor cooling by using a supercritical carbon dioxide directly. Authors propose the supercritical CO{sub 2} Brayton cycle (S-CO{sub 2} cycle) as a power conversion system to achieve small volume of power conversion unit (PCU) and to contain the core and PCU in one vessel for the full modularization. This study suggests a conceptual design of small modular reactor including PCU which is named as KAIST Micro Modular Reactor (MMR). As a part of ongoing research of conceptual design of KAIST MMR, preliminary design of power generation cycle was performed in this study. Since the targets of MMR are full modularization of a reactor system with S-CO{sub 2} coolant, authors selected a simple recuperated S-CO{sub 2} Brayton cycle as a power conversion system for KAIST MMR. The size of components of the S-CO{sub 2} cycle is much smaller than existing helium Brayton cycle and steam Rankine cycle, and whole power conversion system can be contained with core and safety system in one containment vessel. From the investigation of the power conversion cycle, recompressing recuperated cycle showed higher efficiency than the simple recuperated cycle. However the volume of heat exchanger for recompressing cycle is too large so more space will be occupied by heat exchanger in the recompressing cycle than the simple recuperated cycle. Thus, authors consider that the simple recuperated cycle is more suitable for MMR. More research for the KAIST MMR will be followed in the future and detailed information of reactor core and safety system will be developed down the road. More refined cycle layout and design of turbomachinery and heat exchanger will be performed in the future study.

  4. Scaling considerations for a multi-megawatt class supercritical CO2 brayton cycle and commercialization.

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Darryn D.; Holschuh, Thomas Vernon,; Conboy, Thomas M.; Pasch, James Jay; Wright, Steven Alan; Rochau, Gary Eugene; Fuller, Robert Lynn [Barber-Nichols, Inc., Arvada, CO

    2013-11-01

    Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHXs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However, there were many problems that were encountered, such as high rotational speeds in the units. Additionally, the turbomachinery in the test loops need to identify issues concerning the bearings, seals, thermal boundaries, and motor controller problems in order to be proved a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ~10 MWe supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.

  5. Motor starting a Brayton cycle power conversion system using a static inverter

    Science.gov (United States)

    Curreri, J. S.; Edkin, R. A.; Kruchowy, R.

    1973-01-01

    The power conversion module of a 2- to 15-kWe Brayton engine was motor started using a three-phase, 400-hertz static inverter as the power source. Motor-static tests were conducted for initial gas loop pressures of 10, 14, and 17 N/sq cm (15, 20, and 25 psia) over a range of initial turbine inlet temperatures from 366 to 550 K (200 to 530 F). The data are presented to show the effects of temperature and pressure on the motor-start characteristics of the rotating unit. Electrical characteristics during motoring are also discussed.

  6. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Nuclear Space Power Systems: A Feasibility Assessment

    Science.gov (United States)

    Barrett, Michael J.; Johnson, Paul K.

    2004-01-01

    The feasibility of using carbon-carbon recuperators in closed-Brayton-cycle (CBC) nuclear space power conversion systems (PCS) was assessed. Recuperator performance expectations were forecast based on projected thermodynamic cycle state values for a planetary mission. Resulting thermal performance, mass and volume for a plate-fin carbon-carbon recuperator were estimated and quantitatively compared with values for a conventional offset-strip-fin metallic design. Material compatibility issues regarding carbon-carbon surfaces exposed to the working fluid in the CBC PCS were also discussed.

  7. Comparison of Analytical Predictions and Experimental Results for a Dual Brayton Power System

    Science.gov (United States)

    Johnson, Paul

    2007-01-01

    NASA Glenn Research Center (GRC) contracted Barber- Nichols, Arvada, CO to construct a dual Brayton power conversion system for use as a hardware proof of concept and to validate results from a computational code known as the Closed Cycle System Simulation (CCSS). Initial checkout tests were performed at Barber- Nichols to ready the system for delivery to GRC. This presentation describes the system hardware components and lists the types of checkout tests performed along with a couple issues encountered while conducting the tests. A description of the CCSS model is also presented. The checkout tests did not focus on generating data, therefore, no test data or model analyses are presented.

  8. Restrictions on linear heat capacities from Joule-Brayton maximum-work cycle efficiency.

    Science.gov (United States)

    Angulo-Brown, F; Gonzalez-Ayala, Julian; Arias-Hernandez, L A

    2014-02-01

    This paper discusses the possibility of using the Joule-Brayton cycle to determine the accessible value range for the coefficients a and b of the heat capacity at constant pressure C(p), expressed as C(p) = a + bT (with T the absolute temperature) by using the Carnot theorem. This is made for several gases which operate as the working fluids. Moreover, the landmark role of the Curzon-Ahlborn efficiency for this type of cycle is established. PMID:25353449

  9. Supercritical Carbon Dioxide Brayton Power Conversion Cycle Design for Optimized Battery-Type Integral Reactor System

    International Nuclear Information System (INIS)

    Supercritical carbon dioxide (SCO2) promises a high power conversion efficiency of the recompression Brayton cycle due to its excellent compressibility reducing the compression work at the bottom of the cycle and to a higher density than helium or steam decreasing the component size. Therefore, the high SCO2 Brayton cycle efficiency as high as 45 % furnishes small sized nuclear reactors with economical benefits on the plant construction and maintenance. A 23 MWth BORIS (Battery Optimized Reactor Integral System) is being developed as a multipurpose reactor. BORIS, an integral-type optimized fast reactor with an ultra long life core, is coupled to the SCO2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO2 Brayton cycle of BORIS consists of a 16 MW turbine, a 32 MW high temperature recuperator, a 14 MW low temperature recuperator, an 11 MW pre-cooler and 2 and 2.8 MW compressors. Entering six heat exchangers between primary and secondary system at 19.9 MPa and 663 K, the SCO2 leaves the heat exchangers at 19.9 MPa and 823 K. The promising secondary system efficiency of 45 % was calculated by a theoretical method in which the main parameters include pressure, temperature, heater power, the turbine's, recuperators' and compressors' efficiencies, and the flow split ratio of SCO2 going out from the low temperature recuperator. Test loop SOLOS (Shell-and-tube Overall Layout Optimization Study) is utilized to develop advanced techniques needed to adopt the shell-and-tube type heat exchanger in the secondary loop of BORIS by studying the SCO2 behavior from both thermal and hydrodynamic points of view. Concurrently, a computational fluid dynamics (CFD) code analysis is being conducted to develop an optimal analytical method of the SCO2 turbine efficiency having the parameters of flow characteristics of SCO2 passing through buckets of the turbine. These simultaneous experimental and analytical methods for designing

  10. Quantum-mechanical Brayton engine working with a particle in a one-dimensional harmonic trap

    Science.gov (United States)

    Wang, H.

    2013-05-01

    Based on the quantum version of thermodynamic processes, a quantum-mechanical Brayton engine model has been established. Expressions for the power output and efficiency of the engine are derived. Some fundamental optimal relations and general performance characteristic curves of the cycle are obtained. Furthermore, we note that it is possible to resist the reduction in efficiency, caused by compression of the adiabatic process, by decreasing the amount of energy levels of the quantum system. The results obtained here will provide theoretical guidance for the design of some new quantum-mechanical engines.

  11. Progress in investigating Brayton cycle conversion systems for future French Ariane 5 space power applications

    International Nuclear Information System (INIS)

    The present consideration of performance capabilities and system design requirements for a Brayton cycle conversion system usable by future Ariane 5 launch vehicle applications gives attention to such a power system's matching to available radiator concepts and dimensions, the use of direct or indirect waste heat transfer to the radiator and of simple or intercooled cycles, as well the consequences of gas cycle selection on reactor technology. The results presented are expected to be useful in the optimization of a 20-30 kW(e) system employing a liquid metal-cooled nuclear reactor in conjunction with a gas turbine energy conversion system. 10 references

  12. Preliminary market analysis for Brayton cycle heat recovery system characterization program. Subtask 5. 2 of phase I program plan

    Energy Technology Data Exchange (ETDEWEB)

    1980-08-31

    The purpose of the task is to determine the market potential of the Brayton-cycle Subatmospheric System (SAS), especially as applied to the glass processing industry. Areas which impact the sales of the Brayton-cycle systems examined are: market size; opportunities for waste heat system installation (furnace rebuild and repair); pollution control on glass furnaces; equipment costs; equipment performance; and market growth potential. Supporting data were compiled for the glass industry inventory and are presented in Appendix A. Emission control techniques in the glass industry are discussed in Appendix B. (MCW)

  13. Exergetic efficiency optimization for an irreversible heat pump working on reversed Brayton cycle

    Indian Academy of Sciences (India)

    Yuehong Bi; Lingen Chen; Fengrui Sun

    2010-03-01

    This paper deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle with constant-temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The irreversibilities considered in the system include heat resistance losses in the hot- and cold-side heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating load, coefficient of performance (COP) and exergetic efficiency for the heat pumps are derived. The results are compared with those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working fluid on the exergetic efficiency of the heat pumps are analysed by numerical calculations. The results show that the exergetic efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on reversed Brayton cycle.

  14. Heat exchanger design for hot air ericsson-brayton piston engine

    Directory of Open Access Journals (Sweden)

    Ďurčanský P.

    2014-03-01

    Full Text Available One of the solutions without negative consequences for the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration. Currently it is looking for different solutions and there are many possible ways. Cogeneration is known for long time and is widely used. But the installations are often large and the installed output is more suitable for cities or industry companies. When we will speak about decentralization, the small machines have to be used. The article deals with the principle of hot-air engines, their use in combined heat and electricity production from biomass and with heat exchangers as primary energy transforming element. In the article is hot air engine presented as a heat engine that allows the conversion of heat into mechanical energy while heat supply can be external. In the contribution are compared cycles of hot-air engine. Then are compared suitable heat exchangers for use with hot air Ericsson-Brayton engine. In the final part is proposal of heat exchanger for use in closed Ericsson-Brayton cycle.

  15. Creep Property Characterization of Potential Brayton Cycle Impeller and Duct Materials

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, John; Garg, Anita

    2007-01-01

    Cast superalloys have potential applications in space as impellers within closed-loop Brayton cycle nuclear power generation systems. Likewise wrought superalloys are good candidates for ducts and heat exchangers transporting the inert working gas in a Brayton-based power plant. Two cast superalloys, Mar-M247LC and IN792, and a NASA GRC powder metallurgy superalloy, LSHR, have been screened to compare their respective capabilities for impeller applications. Mar-M247LC has been selected for additional long term evaluations. Initial tests in helium indicate this inert environment may debit long term creep resistance of this alloy. Several wrought superalloys including Hastelloy® X, Inconel® 617, Inconel® 740, Nimonic® 263, Incoloy® MA956, and Haynes 230 are also being screened to compare their capabilities for duct applications. Haynes 230 has been selected for additional long term evaluations. Initial tests in helium are just underway for this alloy. These proposed applications would require sufficient strength and creep resistance for long term service at temperatures up to 1200 K, with service times to 100,000 h or more. Therefore, long term microstructural stability is also being screened.

  16. Creep Property Characterization of Potential Brayton Cycle Impeller and Duct Materials

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, john; Garg, Anita

    2007-01-01

    Cast superalloys have potential applications in space as impellers within closed-loop Brayton cycle nuclear power generation systems. Likewise wrought superalloys are good candidates for ducts and heat exchangers transporting the inert working gas in a Brayton-based power plant. Two cast superalloys, Mar-M247LC and IN792, and a NASA GRC powder metallurgy superalloy, LSHR, have been screened to compare their respective capabilities for impeller applications. Mar-M247LC has been selected for additional long term evaluations. Initial tests in helium indicate this inert environment may debit long term creep resistance of this alloy. Several wrought superalloys including Hastelloy(Registered TradeMark) X, Inconel(Registered TradeMark) 617, Inconel(Registered TradeMark) 740, Nimonic(Registered TradeMark) 263, Incoloy(Registered TradeMark) MA956, and Haynes 230 are also being screened to compare their capabilities for duct applications. Haynes 230 has been selected for additional long term evaluations. Initial tests in helium are just underway for this alloy. These proposed applications would require sufficient strength and creep resistance for long term service at temperatures up to 1200 K, with service times to 100,000 h or more. Therefore, long term microstructural stability is also being screened.

  17. Tensile and Creep Property Characterization of Potential Brayton Cycle Impeller and Duct Materials

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, John

    2006-01-01

    This paper represents a status report documenting the work on creep of superalloys performed under Project Prometheus. Cast superalloys have potential applications in space as impellers within closed-loop Brayton cycle nuclear power generation systems. Likewise wrought superalloys are good candidates for ducts and heat exchangers transporting the inert working gas in a Brayton-based power plant. Two cast superalloys, Mar-M247LC and IN792, and a NASA GRC powder metallurgy superalloy, LSHR, are being screened to compare their respective capabilities for impeller applications. Several wrought superalloys including Hastelloy X, (Haynes International, Inc., Kokomo, IN), Inconel 617, Inconel 740, Nimonic 263, and Incoloy MA956 (Special Metals Corporation, Huntington, WV) are also being screened to compare their capabilities for duct applications. These proposed applications would require sufficient strength and creep resistance for long term service at temperatures up to 1200 K, with service times to 100,000 h or more. Conventional tensile and creep tests were performed at temperatures up to 1200 K on specimens extracted from the materials. Initial microstructure evaluations were also undertaken.

  18. Brayton Power Conversion System Study to Advance Technology Readiness for Nuclear Electric Propulsion — Phase I

    Science.gov (United States)

    Frye, Patrick E.; Allen, Robert; Delventhal, Rex

    2005-02-01

    To investigate and mature space based nuclear power conversion technologies NASA awarded several contracts under Prometheus, the Nuclear Systems Program. The studies described in this paper were performed under one of those contracts, which was to investigate the use of a nuclear power conversion system based on the closed Brayton cycle (CBC). The conceptual design effort performed included BPCS (Brayton power conversion system) trade studies to minimize system weight and radiator area and advance the state of the art of BPCS technology. The primary requirements for studies were a power level of 100 kWe (to the PPU), a low overall power system mass (with a target of less than 3000 kg), and a lifetime of 15 years (10 years full power). For the radiation environment, the system was to operate in the generic space environment and withstand the extreme environments within the Jovian system. The studies defined a BPCS design traceable to NBP (Nuclear Electric Propulsion) requirements and suitable for future potential missions with a sound technology plan for TRL (Technical Readiness Level) advancement identified. The studies assumed a turbine inlet temperature ˜ 100C above the current the state of the art capabilities with materials issues identified and an approach for resolution developed. Analyses and evaluations of six HRS (heat rejection subsystem) concepts and PMAD (Power Management and Distribution) architecture trades will be discussed in the paper.

  19. A four-year investigation of Brayton cycle systems for future French space power applications

    International Nuclear Information System (INIS)

    Within the framework of a joint program initiated in 1983 by the two French Government Agencies C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique), in order to study space nuclear power systems for future ARIANE 5 applications, extensive investigations have dealt with the Brayton cycle, which has been selected as the energy conversion system. Several aspects can be mentioned in this field: matching of the power system to the available radiator dimensions up to 200 kWe, direct or indirect waste heat transfer to the radiator, the use of a recuperator, recent work on moderate (25 kWe) power levels, simulation studies related to various operating conditions, and general system optimization. A limited experimental program is starting on some crucial technology areas including a first contract to the Industry concerning the turbogenerator. Particular attention is being paid to the significance of the adoption of a Brayton cycle for space applications involving a nuclear heat source, which can be either a liquid-metal-cooled or a gas-cooled reactor. For a gas-cooled reactor, direct-cycle system, the relevance to the reactor technology and the concept for moderator thermal conditioning is particularly addressed

  20. Improvement of supercritical CO2 Brayton cycle using binary gas mixture

    International Nuclear Information System (INIS)

    A Sodium-cooled Fast Reactor (SFR) is one of the strongest candidates for the next generation nuclear reactor. However, the conventional design of a SFR concept with an indirect Rankine cycle is inevitably subjected to a sodium-water reaction. To prevent hazardous situation caused by sodium-water reaction, the SFR with Brayton cycle using Supercritical Carbon dioxide (S-CO2 cycle) as a working fluid can be an alternative approach. The S-CO2 Brayton cycle is more sensitive to the critical point of working fluids than other Brayton cycles. This is because compressor work significantly decreases at slightly above the critical point due to high density near the boundary between the supercritical state and the subcritical state. For this reason, the minimum temperature and pressure of cycle are just above the CO2 critical point. The critical point acts as a limitation of the lowest operating condition of the cycle. In general, lowering the rejection temperature of a thermodynamic cycle increases the efficiency and thus, changing the critical point of CO2 can result in an improvement of the total cycle efficiency with the same cycle layout. Modifying the critical point of the working fluid can be done by adding other gases to CO2. The direction and range of the CO2 critical point variation depends on the mixed component and its amount. In particular, chemical reactivity of the gas mixture itself and the gas mixture with sodium at high temperatures are of interest. To modify the critical point of the working fluid, several gases were chosen as candidates by which chemical stability with sodium within the interested range of cycle operating condition was assured: CO2 was mixed with N2, O2, He, Ar and Xe. To evaluate the effect of shifting the critical point and changes in the properties of the S-CO2 Brayton cycle, a supercritical Brayton cycle analysis code connected with the REFPROP program from the NIST was developed. The developed code is for evaluating simple

  1. Study on the matching performance of a low temperature reverse Brayton air refrigerator

    International Nuclear Information System (INIS)

    Highlights: • A relation between operation parameters of expander and brake pressure was obtained. • A matching model was got based on the theoretical analysis and simulation. • Brake pressure feedback control was proposed and applied in the experiment. • The minimum free-load refrigerating temperature of 99.6 K was reached. - Abstract: A small reverse Brayton cycle air refrigerator was designed and fabricated. Bump-type air journal foil bearing, pressurized thrust gas bearing and centrifugal blower as brake were employed in the turboexpander. Usually, constant brake inlet pressure is set in a reverse Brayton refrigerator. However, the unchanged brake inlet pressure cannot adapt to the changing temperature and expansion ratio during the cooling down process, which could go against the system performance. In this article, the relationship between the turboexpander operation parameters and brake pressure was disclosed through theoretical analysis. The performance curve was analyzed through numerical simulation using CFX. A matching model was established based on the theoretical analysis and numerical simulation. Brake pressure feedback control was then proposed and applied in the experimental study. Thermal performance of the refrigerator was tested under varied operating conditions (different expansion ratios, temperatures and brake pressures). The results indicated that the appropriate brake pressure facilitated system good thermal performance under both design and off-design conditions, and the theoretical results agreed well with the experimental data

  2. Dynamic simulation of 10 kW Brayton cryocooler for HTS cable

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Ho-Myung; Park, Chan Woo [Hong Ik University, Department of Mechanical Engineering, Seoul, 121-791 (Korea, Republic of); Yang, Hyung Suk; Hwang, Si Dole [KEPCO Research Institute, Daejeon, 305-760 (Korea, Republic of)

    2014-01-29

    Dynamic simulation of a Brayton cryocooler is presented as a partial effort of a Korean governmental project to develop 1∼3 km HTS cable systems at transmission level in Jeju Island. Thermodynamic design of a 10 kW Brayton cryocooler was completed, and a prototype construction is underway with a basis of steady-state operation. This study is the next step to investigate the transient behavior of cryocooler for two purposes. The first is to simulate and design the cool-down process after scheduled or unscheduled stoppage. The second is to predict the transient behavior following the variation of external conditions such as cryogenic load or outdoor temperature. The detailed specifications of key components, including plate-fin heat exchangers and cryogenic turbo-expanders are incorporated into a commercial software (Aspen HYSYS) to estimate the temporal change of temperature and flow rate over the cryocooler. An initial cool-down scenario and some examples on daily variation of cryocooler are presented and discussed, aiming at stable control schemes of a long cable system.

  3. Closed Brayton Cycle Power Conversion Unit for Fission Surface Power Phase I Final Report

    Science.gov (United States)

    Fuller, Robert L.

    2010-01-01

    A Closed Brayton cycle power conversion system has been developed to support the NASA fission surface power program. The goal is to provide electricity from a small nuclear reactor heat source for surface power production for lunar and Mars environments. The selected media for a heat source is NaK 78 with water as a cooling source. The closed Brayton cycle power was selected to be 12 kWe output from the generator terminals. A heat source NaK temperature of 850 K plus or minus 25 K was selected. The cold source water was selected at 375 K plus or minus 25 K. A vacuum radiation environment of 200 K is specified for environmental operation. The major components of the system are the power converter, the power controller, and the top level data acquisition and control unit. The power converter with associated sensors resides in the vacuum radiation environment. The power controller and data acquisition system reside in an ambient laboratory environment. Signals and power are supplied across the pressure boundary electrically with hermetic connectors installed on the vacuum vessel. System level analyses were performed on working fluids, cycle design parameters, heater and cooling temperatures, and heat exchanger options that best meet the needs of the power converter specification. The goal is to provide a cost effective system that has high thermal-to-electric efficiency in a compact, lightweight package.

  4. Dynamic simulation of 10 kW Brayton cryocooler for HTS cable

    Science.gov (United States)

    Chang, Ho-Myung; Park, Chan Woo; Yang, Hyung Suk; Hwang, Si Dole

    2014-01-01

    Dynamic simulation of a Brayton cryocooler is presented as a partial effort of a Korean governmental project to develop 1˜3 km HTS cable systems at transmission level in Jeju Island. Thermodynamic design of a 10 kW Brayton cryocooler was completed, and a prototype construction is underway with a basis of steady-state operation. This study is the next step to investigate the transient behavior of cryocooler for two purposes. The first is to simulate and design the cool-down process after scheduled or unscheduled stoppage. The second is to predict the transient behavior following the variation of external conditions such as cryogenic load or outdoor temperature. The detailed specifications of key components, including plate-fin heat exchangers and cryogenic turbo-expanders are incorporated into a commercial software (Aspen HYSYS) to estimate the temporal change of temperature and flow rate over the cryocooler. An initial cool-down scenario and some examples on daily variation of cryocooler are presented and discussed, aiming at stable control schemes of a long cable system.

  5. Optimum performance analysis of a two-stage irreversible magnetization Brayton refrigeration system

    International Nuclear Information System (INIS)

    A two-stage magnetization Brayton refrigeration cycle model using a paramagnetic material as the working substance is established, in which the regeneration and the irreversibility in the adiabatic processes are taken into account. On the basis of the thermodynamic properties of a paramagnetic material, the expressions of some important parameters such as the coefficient of performance, refrigeration load and work input are derived and used to analyse the performance characteristics of the refrigeration cycle. The influence of the inter-magnetization process, irreversibility in the adiabatic processes and regeneration on the performance of the cycle is discussed in detail. The advantage of adding the inter-magnetization process is expounded and the magnetic field ratio related to the inter-magnetization process is optimized. Moreover, the optimal values of the temperatures of the working substance at different state points and the optimally operating region of the cycle are determined. The results obtained here are compared with those derived from some relevant magnetic Brayton refrigeration cycles, and consequently, some significant conclusions are obtained

  6. El autoconcepto físico durante el ciclo vital

    OpenAIRE

    Esnaola Etxaniz, Igor

    2008-01-01

    El objetivo de esta investigación ha sido analizar el autoconcepto físico durante el ciclo vital. La muestra está compuesta por 1.259 participantes divididos en cuatro tramos de edad: adolescencia (12-18 años), juventud (19-30 años), edad adulta (31-49 años) y personas mayores de 55 años. Tanto en la muestra de mujeres como en la de varones, los resultados indican que las percepciones en las escalas de habilidad física y condición física van disminuyendo desde la adolescencia hasta las person...

  7. TOTALMENTE DIVERSO”: SAN TOMMASO

    Directory of Open Access Journals (Sweden)

    IOSIF TAMAŞ

    2011-05-01

    Full Text Available In order to synthesize the exploration of above presented ideas, wesuggest the following conclusions: Pope John Paul II cherished Saint Thomas as representing „that eternal novelty of thinking” which brought us close to the ontic space of knowledge, the dynamic principle of which is Being. The climax of this condition would be the moment of embracing the truth, which would trigger that vital necessity for metaphysics. According to the stated objective ofthe necessary and indispensable ratio between reason and faith, we see that Tomas suggested the vision of the objective, transcendent and universal truth. This fact determined Pope John Paul II to appreciate that “passion” for truth. The man of our time must walk again towards the light of this truth. In this sense, Saint Thomas’ philosophy represents the guide above all. Its philosophic importance, meaning that “it is truly the philosophy of Being, and not the philosophy of a simple epiphany”, confirms its aim to provide a constant answerto many of the problems that concerns the human mind: the problems ofknowledge and Being, the problems of speaking and doing, the problems of the world, and the problems related with Man and God.

  8. Regulação dos ciclos celulares alternativos de Oikoleura dioica

    OpenAIRE

    Rendeiro, André Figueiredo

    2014-01-01

    O ciclo celular eucariótico é um dos processos biológicos mais estudados. No entanto, variações ao ciclo celular canónico têm sido descobertas e são mais predominantes do que anteriormente previsto. Endoreplicação e endociclos - duas variantes ao ciclo celular canónico - produzem células poliplóides, o que confere vantagens em crescimento e em resistência a stress genotóxico. Apesar de alguns dos princípios regulatórios de endociclos estarem a ser descobertos, ainda pouco é ...

  9. El pensamiento de Keynes sobre los ciclos económicos

    OpenAIRE

    Fernández Lorenzo, Daniel

    2014-01-01

    En este trabajo se realiza una breve revisión histórica del inicio del pensamiento keynesiano sobre los ciclos económicos y su herencia posterior. En primer lugar se exponen los fundamentos macroeconómicos de la teoría keynesiana, que servirán de base para la explicación de cualquier modelo keynesiano del ciclo. Estos principios teóricos los podemos encontrar principalmente en los capítulos 3, 10 y 11 de su Teoría General. A continuación se expone la teoría original de Keynes sobre los ciclos...

  10. Thermal hydraulic feasibility of supercritical carbon dioxide Brayton cycle power conversion for the KALIMER-150 sodium-cooled fast reactor

    International Nuclear Information System (INIS)

    One possible approach to achieving a significant reduction in the overnight and operating costs of a sodium-cooled fast reactor is to replace the traditional Rankine steam cycle with an advanced power converter that consists of a gas turbine Brayton cycle that utilizes supercritical carbon dioxide (S-CO2) as the working fluid. A joint project between Argonne National Laboratory and the Korea Atomic Energy Research Institute has been initiated to investigate the thermal-hydraulic feasibility of coupling the S-CO2 Brayton cycle to the KALIMAR-150 sodium-cooled fast reactor conceptual design. As an initial step in investigating the system aspects of coupling the reactor to the S-CO2 Brayton cycle, the case is investigated in which the intermediate heat transfer loop is eliminated in order to achieve additional cost reductions. The main objectives are to determine the potential gain in plant efficiency and to estimate the size of the key Brayton cycle components. A S-CO2 Brayton cycle efficiency of 43.2% is calculated. Accounting for primary pump power and other in-house loads, a net plant efficiency of 40.8% is obtained, compared to 38.2% for the current (Rankine cycle) plant. If higher Na temperatures could be accommodated, then a 1% gain in plant efficiency could be obtained for each 20degC incremental increase in sodium core outlet temperature. Further investigation of the thermal sizing of the Na/S-Co2 heat exchanger is also carried out; parametric sensitivity studies are performed for the case in which the intermediate heat transport system is retained as well as the case in which it is eliminated. (author)

  11. Importancia de los acontecimientos vitales como factores de cambio en el ciclo vital

    OpenAIRE

    Melero Marcos, Luis; Ventola Barrado, María Luisa I.

    1995-01-01

    RESUMEN: A lo largo del ciclo vital, los individuos experimentan una serie de acontecimientos que, sin duda, influyen en su desarrollo individual y colectivo. Tales acontecimientos parecen introducir cambios en la vida de los sujetos. El presente trabajo pretende analizar la importancia de los acontecimientos vitales como factores de cambio, desde la consideración de que el estudio de los mismos es consustancial con el estudio del ciclo vital. Desde este punto de partida, se ha establecido la...

  12. Ingeniería de sistemas y automática en las asignaturas obligatorias de los nuevos planes de estudio de ciclo largo y segundo ciclo

    OpenAIRE

    Candelas Herías, Francisco Andrés; Puente Méndez, Santiago Timoteo; Ortiz Zamora, Francisco Gabriel; Gil Vázquez, Pablo; Torres Medina, Fernando

    2000-01-01

    Este artículo presenta un estudio sobre la vinculación de asignaturas obligatorias en las universidades públicas españolas al Área de Ingeniería de Sistemas y Automática. Las titulaciones estudiadas son Ingeniero en Automática y Electrónica Industrial (de solo segundo ciclo), Ingeniero Industrial e Ingeniero en Informática (de ciclo largo) de los nuevos planes de estudio. Estas son las titulaciones donde el Área tiene mayor presencia en materias troncales.

  13. Dynamic response simulation for high temperature gas-cooled reactor with indirect closed Brayton cycle

    International Nuclear Information System (INIS)

    A transient simulation program is developed in order to study dynamic characteristics of high temperature gas-cooled reactor with indirect closed Brayton cycle. After the brief introduction to such a plant, detailed mathematical models for important installations are described in the paper. By inducing step positive reactivity into the reactor, it looks like that the powers of turbo machine installations have a different growth rate accompanied with small increase of reactor power. Furthermore, this paper shows the temperature changes of reactor and heat exchangers. For the heat exchangers of the whole secondary loop, the pressure changes behave quite differently for those three sections divided by turbine, low pressure compressor and high pressure compressor. For all these equipments, the simulation program gives reasonable results and is in accordance with dynamic characteristics of their own. (authors)

  14. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

    Science.gov (United States)

    Barrett, Michael J.; Johnson, Paul K.; Naples, Andrew G.

    2006-01-01

    The feasibility of using carbon-carbon (C-C) recuperators in conceptual closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance expectations were forecast based on notional thermodynamic cycle state values for potential planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 30 to 60 percent were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25 to 1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, 60 percent savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed.

  15. Carbon-Carbon Composites as Recuperator Materials for Direct Gas Brayton Systems

    International Nuclear Information System (INIS)

    Of the numerous energy conversion options available for a space nuclear power plant (SNPP), one that shows promise in attaining reliable operation and high efficiency is the direct gas Brayton (GB) system. In order to increase efficiency, the GB system incorporates a recuperator that accounts for nearly half the weight of the energy conversion system (ECS). Therefore, development of a recuperator that is lighter and provides better performance than current heat exchangers could prove to be advantageous. The feasibility of a carbon-carbon (C/C) composite recuperator core has been assessed and a mass savings of 60% and volume penalty of 20% were projected. The excellent thermal properties, high-temperature capabilities, and low density of carbon-carbon materials make them attractive in the GB system, but development issues such as material compatibility with other structural materials in the system, such as refractory metals and superalloys, permeability, corrosion, joining, and fabrication must be addressed

  16. Brayton Isotope Power System. Phase I. (Ground demonstration system) Configuration Control Document (CCD)

    International Nuclear Information System (INIS)

    The configuration control document (CCD) defines the BIPS-GDS configuration. The GDS configuration is similar to a conceptual flight system design, referred to as the BIPS-FS, which is discussed in App. I. The BIPS is being developed by ERDA as a 500 to 2000 W(e), 7-y life, space power system utilizing a closed Brayton cycle gas turbine engine to convert thermal energy (from an isotope heat source) to electrical energy at a net efficiency exceeding 25 percent. The CCD relates to Phase I of an ERDA Program to qualify a dynamic system for launch in the early 1980's. Phase I is a 35-month effort to provide an FS conceptual design and GDS design, fabrication, and test. The baseline is a 7-year life, 450-pound, 4800 W(t), 1300 W(e) system which will use two multihundred watt (MHW) isotope heat sources being developed

  17. Brayton Isotope Power System. Phase I. (Ground demonstration system) Configuration Control Document (CCD)

    Energy Technology Data Exchange (ETDEWEB)

    1976-03-15

    The configuration control document (CCD) defines the BIPS-GDS configuration. The GDS configuration is similar to a conceptual flight system design, referred to as the BIPS-FS, which is discussed in App. I. The BIPS is being developed by ERDA as a 500 to 2000 W(e), 7-y life, space power system utilizing a closed Brayton cycle gas turbine engine to convert thermal energy (from an isotope heat source) to electrical energy at a net efficiency exceeding 25 percent. The CCD relates to Phase I of an ERDA Program to qualify a dynamic system for launch in the early 1980's. Phase I is a 35-month effort to provide an FS conceptual design and GDS design, fabrication, and test. The baseline is a 7-year life, 450-pound, 4800 W(t), 1300 W(e) system which will use two multihundred watt (MHW) isotope heat sources being developed.

  18. Heat exchanger optimization of a closed Brayton cycle for nuclear space propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Guilherme B.; Guimaraes, Lamartine N.F.; Braz Filho, Francisco A., E-mail: gbribeiro@ieav.cta.br, E-mail: guimarae@ieav.cta.br, E-mail: braz@ieav.cta.br [Instituto de Estudos Avancados (IEAV), Sao Jose dos Campos, SP (Brazil). Divisao de Energia Nuclear

    2015-07-01

    Nuclear power systems turned to space electric propulsion differs strongly from usual ground-based power systems regarding the importance of overall size and weight. For propulsion power systems, weight and efficiency are essential drivers that should be managed during conception phase. Considering that, this paper aims the development of a thermal model of a closed Brayton cycle that applies the thermal conductance of heat exchangers in order to predict the energy conversion performance. The centrifugal-flow turbine and compressor characterization were achieved using algebraic equations from literature data. The binary mixture of He-Xe with molecular weight of 40 g/mole is applied and the impact of heat exchanger optimization in thermodynamic irreversibilities is evaluated in this paper. (author)

  19. Brayton cycle conversion and additional French investigations on space nuclear power systems

    International Nuclear Information System (INIS)

    French activities in the field of space nuclear power systems have proceeded in anticipation that spacecraft would require such systems for the provision of 20 kW(e) by the year 2005. A liquid metal-cooled reactor patterned on well tested terrestrial technologies has been investigated which employs a Brayton-cycle heat-conversion system in such a way as to allow temperature conditioning of the moderator for a thermal-spectrum reactor. A high pressure gas cycle derivation technique makes it possible to maintain water within the requisite temperature range. The concept thus evolved is attractive in light of fuel inventory, mass, radiation shielding, and control points considerations. 7 refs

  20. Carbon-Carbon Composites as Recuperator Material for Direct Gas Brayton Systems

    Energy Technology Data Exchange (ETDEWEB)

    RA Wolf

    2006-07-19

    Of the numerous energy conversion options available for a space nuclear power plant (SNPP), one that shows promise in attaining reliable operation and high efficiency is the direct gas Brayton (GB) system. In order to increase efficiency, the GB system incorporates a recuperator that accounts for nearly half the weight of the energy conversion system (ECS). Therefore, development of a recuperator that is lighter and provides better performance than current heat exchangers could prove to be advantageous. The feasibility of a carbon-carbon (C/C) composite recuperator core has been assessed and a mass savings of 60% and volume penalty of 20% were projected. The excellent thermal properties, high-temperature capabilities, and low density of carbon-carbon materials make them attractive in the GB system, but development issues such as material compatibility with other structural materials in the system, such as refractory metals and superalloys, permeability, corrosion, joining, and fabrication must be addressed.

  1. Isotope Brayton ground demonstration testing and flight qualification. Volume 1. Technical program

    Energy Technology Data Exchange (ETDEWEB)

    1974-12-09

    A program is proposed for the ground demonstration, development, and flight qualification of a radioisotope nuclear heated dynamic power system for use on space missions beginning in the 1980's. This type of electrical power system is based upon and combines two aerospace technologies currently under intense development; namely, the MHW isotope heat source and the closed Brayton cycle gas turbine. This power system represents the next generation of reliable, efficient economic electrical power equipment for space, and will be capable of providing 0.5 to 2.0 kW of electric power to a wide variety of spacecraft for earth orbital and interplanetary missions. The immediate design will be based upon the requirements for the Air Force SURVSATCOM mission. The proposal is presented in three volumes plus an Executive Summary. This volume describes the tasks in the technical program.

  2. Heat exchanger optimization of a closed Brayton cycle for nuclear space propulsion

    International Nuclear Information System (INIS)

    Nuclear power systems turned to space electric propulsion differs strongly from usual ground-based power systems regarding the importance of overall size and weight. For propulsion power systems, weight and efficiency are essential drivers that should be managed during conception phase. Considering that, this paper aims the development of a thermal model of a closed Brayton cycle that applies the thermal conductance of heat exchangers in order to predict the energy conversion performance. The centrifugal-flow turbine and compressor characterization were achieved using algebraic equations from literature data. The binary mixture of He-Xe with molecular weight of 40 g/mole is applied and the impact of heat exchanger optimization in thermodynamic irreversibilities is evaluated in this paper. (author)

  3. Conceptual Design of S-CO2 Brayton Cycle Radial Turbomachinery for KAIST Micro Modular Reactor

    International Nuclear Information System (INIS)

    KAIST proposed a new SMR design, which utilizes S-CO2 as the working fluid. It was named as KAIST MMR. Compared with existing SMR concepts, KAIST MMR has advantages of achieving smaller volume of power conversion unit (PCU) and containing the core and PCU in one vessel for the complete modularization. Authors noticed that the compressor and turbine assumed performances of KAIST MMR were conservatively selected previously. Thus, this paper tries to address the best estimate values of each turbomachinery in 10MWe class KAIST MMR. The turbomachinery size of the S-CO2 cycle is smaller than helium Brayton cycle and steam Rankine cycle. The suggested SMR concept adopts passive cooling system by using air. This method can cool reactor without external electricity supply. Small size and more flexible installation in the inland area will be necessary characteristics for the future nuclear application in the water limited region. KAIST MMR meets all these requirements by utilizing S-CO2 as a working fluid. This paper presents the work for further increasing the system performance by estimating the component efficiency more realistically. The cycle layout adopted for the application is S-CO2 recuperated Brayton cycle. The best efficiency of compressor and turbine was evaluated to be 84.94% and 90.94%, respectively. By using KAIST in-house code, thermal efficiency and net output were increased to 35.81% and 12.45MWe, respectively, for the same core thermal power. More refined cycle layout and suitable turbomachinery design will be performed in the near future

  4. Optimization of Brayton cycles for low-to-moderate grade thermal energy sources

    International Nuclear Information System (INIS)

    Future electricity generation will involve low or moderate temperature technologies. In such a scenario, optimisation of thermodynamic cycles will be a key task. This work presents a systematic analysis to find the operating regime where Brayton cycles reach the highest efficiency, using real substances and given heat source and sink temperatures. Several configurations using fluids close to its critical point at the compressor inlet are considered. Irreversibility sources are carefully analysed, as well as the type of working fluid. The analysis is performed by means of a theoretical approach to obtain some trends, which are afterwards validated with real gases. Results show that the efficiency and the specific work improve if the compressor inlet is close to the critical point. Furthermore, these cycles are less sensitive to pressure drops and politropic efficiencies than those working with ideal gases. The above features are more evident when the ratio of heat source and heat sink temperatures is low. The selection of the gas becomes a fundamental issue in this quest. Critical temperature should be close to ambient temperature, low critical pressure is advisable and the R/cp factor measured at the ideal gas condition should be low to further enhance the efficiency. - Highlights: • Performance analysis of Brayton cycles with the compressor inlet close to the critical point. • Cycles are not very sensitive to pressure drops and isentropic efficiencies of the compressor. • Gas selection becomes important, regarding the critical pressure and temperature as well as the kind of fluid. • R/cp factor measured at the ideal gas condition should be as low as possible

  5. Performance analysis of a large-scale helium Brayton cryo-refrigerator with static gas bearing turboexpander

    International Nuclear Information System (INIS)

    Highlights: • A 2 kW at 20.0 K helium Brayton cryo-refrigerator is built in China. • A series of tests have been systematically conducted to investigate the performance of the cryo-refrigerator. • Maximum heat conductance proportion (90.7%) appears in the heat exchangers of cold box rather than those of heat reservoirs. • A model of helium Brayton cryo-refrigerator/cycle is presented according to finite-time thermodynamics. - Abstract: Large-scale helium cryo-refrigerator is widely used in superconducting systems, nuclear fusion engineering, and scientific researches, etc., however, its energy efficiency is quite low. First, a 2 kW at 20.0 K helium Brayton cryo-refrigerator is built, and a series of tests have been systematically conducted to investigate the performance of the cryo-refrigerator. It is found that maximum heat conductance proportion (90.7%) appears in the heat exchangers of cold box rather than those of heat reservoirs, which is the main characteristic of the helium Brayton cryo-refrigerator/cycle different from the air Brayton refrigerator/cycle. Other three characteristics also lie in the configuration of refrigerant helium bypass, internal purifier and non-linearity of specific heat of helium. Second, a model of helium Brayton cryo-refrigerator/cycle is presented according to finite-time thermodynamics. The assumption named internal purification temperature depth (PTD) is introduced, and the heat capacity rate of whole cycle is divided into three different regions in accordance with the PTD: room temperature region, upper internal purification temperature region and lower one. Analytical expressions of cooling capacity and COP are obtained, and we found that the expressions are piecewise functions. Further, comparison between the model and the experimental results for cooling capacity of the helium cryo-refrigerator shows that error is less than 7.6%. The PTD not only helps to achieve the analytical formulae and indicates the working

  6. Sobre el ciclo maya de 819 días

    Directory of Open Access Journals (Sweden)

    Huberto Quiñones Garza

    2011-01-01

    Full Text Available Algunos autores consideran que los mayas manejaban un ciclo de 819 días, que habría tenido un carácter mágico o ritual, sin descartar alguna manifestación astrológica o astronómica. Un enfoque que no ha sido tomado en cuenta hasta hoy, es el puramente aritmético, el posible interés del sacerdocio maya en este número como tal. Se especula aquí que el número 819 está relacionado con el valor de TT, además de la probable vinculación que esta cifra podría guardar con sus sistemas numérico y calendárico. Dos situaciones se vislumbran como importantes contribuciones, el planteamiento epistemológico implícito y los resultados obtenidos como información básica para futuras investigaciones dentro de la etnomatemática y la antropología.

  7. Modelo de ciclo de vida de empreendimentos sociais

    Directory of Open Access Journals (Sweden)

    Alexandre Meira de Vasconcelos

    2012-08-01

    Full Text Available Este artigo apresenta um modelo de ciclo de vida de empreendimentos sociais. Os dados primários foram obtidos em entrevistas com fundadores de 10 empreendimentos sociais de Curitiba (PR acerca da história de vida da organização. A análise qualitativa dos dados identificou cinco etapas de evolução (Ação Social, Associação, Visibilidade Social, Rede Social e Representatividade Social com, respectivamente, seis momentos de crise que determinam a passagem para uma etapa posterior (Desequilíbrio Social, Identidade, Foco, Controle, Responsabilização e Ética. O estudo reafirma as diferenças entre o empreendedorismo social e o privado e justifica o tratamento diferenciado entre eles. O modelo pode subsidiar a decisão dos gestores sobre o futuro da organização, bem como de financiadores públicos e privados, gestores de redes sociais, pesquisadores, consultores, administradores públicos, entre outros stakeholders, e abre caminho para outros estudos sobre o tema.

  8. Movimientos correctos a la velocidad correcta sobre los ciclos correctos

    Directory of Open Access Journals (Sweden)

    Jorge Enrique Mejía Q.

    2006-05-01

    Full Text Available El propósito del estudio fue explicar cómo una pequeña empresa colombiana compite en el mercado de telecomunicaciones de Estados Unidos. Esto fue posible usando el modelo de la Doble Hélice de Fine, que muestra los ciclos estructurales de cambios tecnológicos, sobre los que la compañía tuvo que tomar las decisiones estratégicas correctas para seguir la dinámica sectorial a la velocidad correcta. El estudio de caso consistió en una síntesis histórica sectorial y de la empresa, incluyendo hitos claves, después, la velocidad fue medida y finalmente una decisión fue recomendada para poder sobrevivir sobre el patrón de movimientos y cambios sectoriales. / The purpose of this study was to explain how a little Colombian company competes in the dynamic US telecomm market. It was possible by using Fine´s Double Helix Model that shows two structural cycles to explain technological movements, in each cycle, the company studied had to do the correct strategic decisions to follow the industrial dynamics at the right clockspeed. The case study consisted of an industrial and a company historical synthesis, including key issues, afterwards, clockspeed is measured and finally a decision is recommended to survive on the pattern of industrial changes and movements.

  9. Niveles de progesterona durante el ciclo normal y silencioso en bovinos en el trópico colombiano

    OpenAIRE

    Henry Grajales L; Aureliano Hernández V; Esperanza Prieto

    2010-01-01

    Objetivo. Determinar la secuencia de cambios en los niveles de progesterona (NP) durante el Ciclo Normal (CN) y Ciclo Silencioso (CS). Materiales y métodos. 94 Hembras de los grupos raciales Holstein x Cebú (HC), Simmental x Cebú (SC), Romosinuano (R) y Cebú (C) se estudiaron desde la pubertad y durante los tres primeros ciclos estrales. Se tomaron muestras de sangre para determinar las concentraciones de progesterona mediante Radioinmunoanálisis, se determinaron...

  10. CICLO DE VIDA: JUEGO EDUCATIVO MOVIL “EDUCAMOVIL”

    Directory of Open Access Journals (Sweden)

    Judith del Pilar Rodríguez

    2013-12-01

    Full Text Available El presente artículo describe la creación de un modelo de ciclo de vida para el desarrollo de juegos educativos en plataformas móviles, teniendo en cuenta las consideraciones para su construcción como un software de calidad. El modelo para el desarrollo de juegos educativos en plataformas móviles es una guía enmarcada en un entorno pedagógico que facilitará la creación de juegos educativos, abriendo las puertas al desarrollo de videojuegos como prácticas de laboratorio, exploración de ambientes virtuales sin necesidad de materiales costosos y así poder transmitir conocimientos a los estudiantes. La metodología desarrollada se logró a través de la recopilación de información de los distintos modelos de desarrollo de software existentes, en ambientes educativos y su enfoque a plataformas móviles, realizando un estudio de ventajas y desventajas, recomendaciones y algunos recursos de los modelos actuales y su adaptación a estos dispositivos; buscando establecer los pasos básicos, coherentes, involucrados en las fases de análisis, diseño, implementación y pruebas para la creación de juegos, enmarcados en un contexto de estrategias pedagógicas de los modelos existentes y dando la respectiva documentación para el desarrollo en plataformas móviles.

  11. Expectativa y ciclo: hacia una dinámica keynesiana

    Directory of Open Access Journals (Sweden)

    García Molina Mario

    1991-06-01

    Full Text Available

    In chapter 17 of the General Theory, Keynes introduced the concept of the own-rates of interest in order to study a monetary economy of production, under an implicit assumption of equilibrium. This paper extends this concept for the analysis of a monetary economy in permanent disequilibrium and upon essential uncertainty. It is shown how the theories of liquidity preference and of finance are taken as complementary explanations. Differences between actual and expected own rates help to explain short term phenomena. and the behavior of capitalist along the business cycle. Depressions appear as a possibility which, in the case of ocurring it is necessary either state intervention or any other exogenous element to the same market in order to overcome them.

    En el capitulo 17 de la Teoría General, Keynes introduce el concepto de tasa propia de interés para estudiar una economía monetaria bajo un supuesto implícito de equilibrio. En este trabajo se aplica el mismo concepto al análisis de una economía monetaria en desequilibrio permanente y con una incertidumbre irreductible. Se muestra que las teorías de la preferencia por la liquidez y la de financiamiento constituyen explicaciones complementarias. Las diferencias entre tasas propias esperadas y realizadas ayudan a explicar los fenómenos de corto plazo y el comportamiento de los inversionistas a lo largo del ciclo de negocios. Las depresiones aparecen como una posibilidad que, en caso de ocurrir, no pueden ser superadas sin intervención del Estado o de otro elemento exógeno al mercado mismo.

  12. Análisis cuantitativo de los ciclos económicos

    Directory of Open Access Journals (Sweden)

    Álvarez Vázquez, Nelson J.

    2003-01-01

    Full Text Available El análisis clásico de series temporales asumía que la serie histórica era la suma de tendencia, ciclo regular, estacional y perturbación aleatoria, movimientos que pueden reducirse a tendencia y ciclo. La descomposición en tendencia y ciclo permitía un análisis separado de ambos tipos de movimientos. Esta aproximación suponía que el ciclo era una desviación respecto de la tendencia (determinista a largo plazo, a la cual revertían aquellos ciclos. Cualquier shock aleatorio tenía sólo un efecto transitorio que se agotaba en uno o unos pocos periodos. Este enfoque ha sido hoy abandonado y sustituido por otro de naturaleza probabilística. En particular el artículo de Nelson y Plosser (1982 habría significado el fin de una aproximación ya cuestionada. En este trabajo, los autores contrastaron la hipótesis de raíz unitaria para diversas series macroeconómicas norteamericanas, encontrando que era imposible rechazarla. Mientras que en la primitiva visión, las fluctuaciones se contemplaban como desviaciones respecto a la tendencia determinista, la existencia de raíz unitaria significa que todas las fluctuaciones representan cambios 2 permanentes en la tendencia a largo plazo, dado que el efecto de cualquier shock, permanece indefinidamente, en lugar de agotarse con el paso del tiempo. De ahí la importancia de la existencia de raíz unitaria en el análisis cuantitativo del ciclo. Sólo mediante la diferenciación se alcanzaría la estacionariedad. En caso contrario, es decir si se elimina una tendencia temporal a una serie generada por un proceso de camino aleatorio (el ejemplo paradigmático de tendencia estocástica, se obtendrán inferencias espurias sobre el ciclo (Nelson y Kang, 1981. En esta cuestión como en tantas otras, es perceptible la evolución metodológica experimentada por la econometría, que se ha desplazado desde un enfoque determinista, donde lo que importaban eran cuestiones como la obtención de la cronolog

  13. Enhanced arrangement for recuperators in supercritical CO2 Brayton power cycle for energy conversion in fusion reactors

    International Nuclear Information System (INIS)

    Highlights: •We propose an enhanced power conversion system layout for a Model C fusion reactor. •Proposed layout is based on a modified recompression supercritical CO2 Brayton cycle. •New arrangement in recuperators regards to classical cycle is used. •High efficiency is achieved, comparable with the best obtained in complex solutions. -- Abstract: A domestic research program called TECNOFUS was launched in Spain in 2009 to support technological developments related to a dual coolant breeding blanket concept for fusion reactors. This concept of blanket uses Helium (300 °C/400 °C) to cool part of it and a liquid metal (480 °C/700 °C) to cool the rest; it also includes high temperature (700 °C/800 °C) and medium temperature (566 °C/700 °C) Helium cooling circuits for divertor. This paper proposes a new layout of the classical recompression supercritical CO2 Brayton cycle which replaces one of the recuperators (the one with the highest temperature) by another which by-passes the low temperature blanket source. This arrangement allows reaching high turbine inlet temperatures (around 600 °C) with medium pressures (around 225 bar) and achieving high cycle efficiencies (close to 46.5%). So, the proposed cycle reveals as a promising design because it integrates all the available thermal sources in a compact layout achieving high efficiencies with the usual parameters prescribed in classical recompression supercritical CO2 Brayton cycles

  14. Application of exergetic sustainability index to a nano-scale irreversible Brayton cycle operating with ideal Bose and Fermi gasses

    International Nuclear Information System (INIS)

    Highlights: • An irreversible Brayton cycle operating quantum gasses is considered. • Exergetic sustainability index is derived for nano-scale cycles. • Nano-scale effects are considered. • Calculation are conducted for irreversible cycles. • Numerical results are presented and discussed. - Abstract: In this study, a nano-scale irreversible Brayton cycle operating with quantum gasses including Bose and Fermi gasses is researched. Developments in the nano-technology cause searching the nano-scale machines including thermal systems to be unavoidable. Thermodynamic analysis of a nano-scale irreversible Brayton cycle operating with Bose and Fermi gasses was performed (especially using exergetic sustainability index). In addition, thermodynamic analysis involving classical evaluation parameters such as work output, exergy output, entropy generation, energy and exergy efficiencies were conducted. Results are submitted numerically and finally some useful recommendations were conducted. Some important results are: entropy generation and exergetic sustainability index are affected mostly for Bose gas and power output and exergy output are affected mostly for the Fermi gas by x. At the high temperature conditions, work output and entropy generation have high values comparing with other degeneracy conditions

  15. Use of Multiple Reheat Helium Brayton Cycles to Eliminate the Intermediate Heat Transfer Loop for Advanced Loop Type SFRs

    Energy Technology Data Exchange (ETDEWEB)

    Haihua Zhao; Hongbin Zhang; Samuel E. Bays

    2009-05-01

    The sodium intermediate heat transfer loop is used in existing sodium cooled fast reactor (SFR) plant design as a necessary safety measure to separate the radioactive primary loop sodium from the water of the steam Rankine power cycle. However, the intermediate heat transfer loop significantly increases the SFR plant cost and decreases the plant reliability due to the relatively high possibility of sodium leakage. A previous study shows that helium Brayton cycles with multiple reheat and intercooling for SFRs with reactor outlet temperature in the range of 510°C to 650°C can achieve thermal efficiencies comparable to or higher than steam cycles or recently proposed supercritical CO2 cycles. Use of inert helium as the power conversion working fluid provides major advantages over steam or CO2 by removing the requirement for safety systems to prevent and mitigate the sodium-water or sodium-CO2 reactions. A helium Brayton cycle power conversion system therefore makes the elimination of the intermediate heat transfer loop possible. This paper presents a pre-conceptual design of multiple reheat helium Brayton cycle for an advanced loop type SFR. This design widely refers the new horizontal shaft distributed PBMR helium power conversion design features. For a loop type SFR with reactor outlet temperature 550°C, the design achieves 42.4% thermal efficiency with favorable power density comparing with high temperature gas cooled reactors.

  16. Application of exergetic sustainability index to a nano-scale irreversible Brayton cycle operating with ideal Bose and Fermi gasses

    Energy Technology Data Exchange (ETDEWEB)

    Açıkkalp, Emin, E-mail: eacikkalp@gmail.com [Department of Mechanical and Manufacturing Engineering, Engineering Faculty, Bilecik S.E. University, Bilecik (Turkey); Caner, Necmettin [Department of Chemistry, Faculty of Arts and Sciences, Eskisehir Osmangazi University, Eskisehir (Turkey)

    2015-09-25

    Highlights: • An irreversible Brayton cycle operating quantum gasses is considered. • Exergetic sustainability index is derived for nano-scale cycles. • Nano-scale effects are considered. • Calculation are conducted for irreversible cycles. • Numerical results are presented and discussed. - Abstract: In this study, a nano-scale irreversible Brayton cycle operating with quantum gasses including Bose and Fermi gasses is researched. Developments in the nano-technology cause searching the nano-scale machines including thermal systems to be unavoidable. Thermodynamic analysis of a nano-scale irreversible Brayton cycle operating with Bose and Fermi gasses was performed (especially using exergetic sustainability index). In addition, thermodynamic analysis involving classical evaluation parameters such as work output, exergy output, entropy generation, energy and exergy efficiencies were conducted. Results are submitted numerically and finally some useful recommendations were conducted. Some important results are: entropy generation and exergetic sustainability index are affected mostly for Bose gas and power output and exergy output are affected mostly for the Fermi gas by x. At the high temperature conditions, work output and entropy generation have high values comparing with other degeneracy conditions.

  17. Use of fully covered self-expanding metal stents for the management of benign biliary conditions Utilización de prótesis metálicas autoexpandibles totalmente recubiertas en procesos biliares benignos

    Directory of Open Access Journals (Sweden)

    J. García-Cano

    2010-09-01

    pequeños y proporcionar, al abrirse completamente, diámetros grandes para el drenaje biliar. Su utilización en procesos benignos ha estado muy limitada, fundamentalmente por la dificultad en su extracción. Presentamos nuestra experiencia inicial con una PMAB totalmente recubierta (Wallflex para tratar patología benigna de la vía biliar. Pacientes y métodos: en un estudio descriptivo prospectivo se insertaron por CPRE prótesis de 8 mm de diámetro y 4, 6 u 8 cm de longitud, cuando se consideró que para el drenaje biliar eran precisos diámetros superiores a 10 french (3,3 mm. Las prótesis se retiraron también por endoscopia varios meses después según se consideró oportuno clínicamente. Resultados: se insertaron 20 PMAB. Los motivos fueron: gran fístula biliar intrahepática tras cirugía de quiste hidatídico (1, perforación del área papilar por esfinterotomía endoscópica (2, recanalización de prótesis no recubiertas insertadas en procesos benignos (3, estenosis benignas (7, coledocolitiasis múltiples y de gran tamaño con afilamiento-estenosis del colédoco distal que no pudieron extraerse (7. En todos los casos se logró un drenaje biliar satisfactorio y no se produjeron complicaciones por la inserción. Las prótesis se extrajeron con facilidad a los 132 días de media (36-270. La resolución completa de los procesos se obtuvo en 14 pacientes (70%. Conclusiones: en nuestra experiencia inicial, la prótesis Wallflex biliar totalmente recubierta pudo extraerse sin complicaciones tras permanecer en el colédoco hasta una media de más cuatro meses, por lo que podría utilizarse en el tratamiento de procesos biliares benignos.

  18. La teoria del ciclo vitale del risparmio di Modigliani cinquant’anni dopo

    Directory of Open Access Journals (Sweden)

    Mauro Baranzini

    2005-06-01

    Full Text Available Nei primi anni ’50 Franco Modigliani, insieme a Richard Brumberg e ad Albert Ando, formulò lateoria del ciclo vitale del consumo e del risparmio, che ha riscosso un enorme e indiscussosuccesso per almeno tre decenni. Tuttavia, a partire dai primi anni ’80 la teoria del ciclo vitale èstata criticata in modo sempre più serrato, per almeno quattro ragioni. La prima consistenell’esistenza di una significativa trasmissione intergenerazionale della ricchezza, da ricondurre acause esogene al modello del ciclo vitale. La seconda ragione è rappresentata dalla crescenteevidenza che i ricchi continuano a risparmiare in misura maggiore rispetto ai meno fortunati,come, in effetti, Keynes sosteneva. Il terzo motivo è che vi sono prove sempre più evidenti,almeno nell’Europa occidentale e in Giappone, che le famiglie giovani, durante i venti e i trentaanni di età, risparmiano una quota positiva e crescente del proprio reddito, e ciò si pone indeciso contrasto con la versione originaria della teoria del ciclo vitale. Infine, numerosi lavoriempirici hanno rilevato che i pensionati accantonano una parte elevata del proprio reddito. Ciòimpone un serio ripensamento dell’approccio della teoria del ciclo vitale, che interessa sia l’analisieconomica sia la politica economica.

  19. A Closed Brayton Power Conversion Unit Concept for Nuclear Electric Propulsion for Deep Space Missions

    Science.gov (United States)

    Joyner, Claude Russell; Fowler, Bruce; Matthews, John

    2003-01-01

    In space, whether in a stable satellite orbit around a planetary body or traveling as a deep space exploration craft, power is just as important as the propulsion. The need for power is especially important for in-space vehicles that use Electric Propulsion. Using nuclear power with electric propulsion has the potential to provide increased payload fractions and reduced mission times to the outer planets. One of the critical engineering and design aspects of nuclear electric propulsion at required mission optimized power levels is the mechanism that is used to convert the thermal energy of the reactor to electrical power. The use of closed Brayton cycles has been studied over the past 30 or years and shown to be the optimum approach for power requirements that range from ten to hundreds of kilowatts of power. It also has been found to be scalable to higher power levels. The Closed Brayton Cycle (CBC) engine power conversion unit (PCU) is the most flexible for a wide range of power conversion needs and uses state-of-the-art, demonstrated engineering approaches. It also is in use with many commercial power plants today. The long life requirements and need for uninterrupted operation for nuclear electric propulsion demands high reliability from a CBC engine. A CBC engine design for use with a Nuclear Electric Propulsion (NEP) system has been defined based on Pratt & Whitney's data from designing long-life turbo-machines such as the Space Shuttle turbopumps and military gas turbines and the use of proven integrated control/health management systems (EHMS). An integrated CBC and EHMS design that is focused on using low-risk and proven technologies will over come many of the life-related design issues. This paper will discuss the use of a CBC engine as the power conversion unit coupled to a gas-cooled nuclear reactor and the design trends relative to its use for powering electric thrusters in the 25 kWe to 100kWe power level.

  20. Nuclear Air-Brayton Combined Cycle Power Conversion Design, Physical Performance Estimation and Economic Assessment

    Science.gov (United States)

    Andreades, Charalampos

    The combination of an increased demand for electricity for economic development in parallel with the widespread push for adoption of renewable energy sources and the trend toward liberalized markets has placed a tremendous amount of stress on generators, system operators, and consumers. Non-guaranteed cost recovery, intermittent capacity, and highly volatile market prices are all part of new electricity grids. In order to try and remediate some of these effects, this dissertation proposes and studies the design and performance, both physical and economic, of a novel power conversion system, the Nuclear Air-Brayton Combined Cycle (NACC). The NACC is a power conversion system that takes a conventional industrial frame type gas turbine, modifies it to accept external nuclear heat at 670°C, while also maintaining its ability to co-fire with natural gas to increase temperature and power output at a very quick ramp rate. The NACC addresses the above issues by allowing the generator to gain extra revenue through the provision of ancillary services in addition to energy payments, the grid operator to have a highly flexible source of capacity to back up intermittent renewable energy sources, and the consumer to possibly see less volatile electricity prices and a reduced probability of black/brown outs. This dissertation is split into six sections that delve into specific design and economic issues related to the NACC. The first section describes the basic design and modifications necessary to create a functional externally heated gas turbine, sets a baseline design based upon the GE 7FB, and estimates its physical performance under nominal conditions. The second section explores the off-nominal performance of the NACC and characterizes its startup and shutdown sequences, along with some of its safety measures. The third section deals with the power ramp rate estimation of the NACC, a key performance parameter in a renewable-heavy grid that needs flexible capacity. The

  1. A closed Brayton power conversion unit concept for nuclear electric propulsion for deep space missions

    International Nuclear Information System (INIS)

    In space, whether in a stable satellite orbit around a planetary body or traveling as a deep space exploration craft, power is just as important as the propulsion. The need for power is especially important for in-space vehicles that use Electric Propulsion. Using nuclear power with electric propulsion has the potential to provide increased payload fractions and reduced mission times to the outer planets. One of the critical engineering and design aspects of nuclear electric propulsion at required mission optimized power levels is the mechanism that is used to convert the thermal energy of the reactor to electrical power. The use of closed Brayton cycles has been studied over the past 30 or years and shown to be the optimum approach for power requirements that range from ten to hundreds of kilowatts of power. It also has been found to be scalable to higher power levels. The Closed Brayton Cycle (CBC) engine power conversion unit (PCU) is the most flexible for a wide range of power conversion needs and uses state-of-the-art, demonstrated engineering approaches. It also is in use with many commercial power plants today. The long life requirements and need for uninterrupted operation for nuclear electric propulsion demands high reliability from a CBC engine. A CBC engine design for use with a Nuclear Electric Propulsion (NEP) system has been defined based on Pratt and Whitney's data from designing long-life turbo-machines such as the Space Shuttle turbopumps and military gas turbines and the use of proven integrated control/health management systems (EHMS). An integrated CBC and EHMS design that is focused on using low-risk and proven technologies will over come many of the life-related design issues. This paper will discuss the use of a CBC engine as the power conversion unit coupled to a gas-cooled nuclear reactor and the design trends relative to its use for powering electric thrusters in the 25 kWe to 100kWe power level

  2. Ciclos de desenvolvimento humano e formação de educadores

    Directory of Open Access Journals (Sweden)

    Arroyo Miguel G.

    1999-01-01

    Full Text Available Os ciclos não são mais uma proposta isolada de algumas escolas, a nova LDB os legitimou e estão sendo adotados por muitas redes escolares. Este texto se pergunta pelo tipo de profissional que está sendo formado nessa modalidade de organização do trabalho pedagógico. A reflexão está estruturada em duas partes. A primeira reflete sobre o caráter formador do repensar das concepções e práticas de formação que acontecem na implantação dos ciclos. A segunda parte reflete sobre as virtualidades formadoras de todo o processo de desconstrução de uma estrutura centrada nas Temporalidades ou Ciclos do Desenvolvimento Humano.

  3. Ignimbritas riolíticas neoproterozoicas en la Sierra Norte de Córdoba: ¿evidencia de un arco magmático temprano en el ciclo Pampeano?

    Directory of Open Access Journals (Sweden)

    EJ Llambías

    2003-12-01

    Full Text Available La Sierra Norte forma parte de las Sierras Pampeanas de Córdoba por lo cual las principales intrusiones graníticas y el metamorfismo están relacionadas al ciclo orogénico Pampeano. La mayor diferencia con las Sierras de Córdoba es que en Sierra Norte el grado metamórfico es bajo y las intrusiones son superficiales. La Sierra Norte está compuesta por pequeños afloramientos de metasedimentitas, plutones de granodiorita y granito y cuerpos subvolcánicos relacionados a los últimos estadios del batolito. En este trabajo describimos mantos de ignimbritas intercalados en los metaconglomerados de la Formación La Lidia. Las ignimbritas están moderadamente soldadas y está compuestas por aproximadamente 15 % de porfiroclastos de cuarzo, feldespato potásico y plagioclasa totalmente alterada. La pasta consiste de trizas vítreas devitrificadas. La edad U/Pb convencional en circones dio 584+22/-14 Ma y es interpretada como la edad de cristalización. Tanto las ignimbritas como la roca de caja han sido afectadas por un metamorfismo en facies prehnita-pumpellita que alteró la plagioclasa en zoicita, sericita y pumpellita. Las ignimbritas silícicas neoproterozoicas, conjuntamente con el batolito calcoalcalino que le suceden sugiere la existencia de un arco magmático asociado al margen continental activo de Gondwana. Este arco habría estado activo desde el Neoproterozoico hasta el Cámbrico, con una duración de más de 60 Ma. La correlación de las metasedimentitas y volcanitas neoproterozoicas con la Formación Puncoviscana es posible.

  4. Fully covered self-expanding metal stents in the management of difficult common bile duct stones Prótesis metálicas autoexpandibles totalmente recubiertas en el tratamiento de coledocolitiasis difíciles

    Directory of Open Access Journals (Sweden)

    Jesús García-Cano

    2013-01-01

    Full Text Available Background and objectives: plastic biliary stents are often used after an ERCP session without complete common bile duct stones (CBDS extraction. Sometimes, the volume of biliary drainage with these stents may be insufficient. We present our experience with the use of fully covered self-expanding metal stents (FCSEMS in the setting of incomplete CBDS extraction. Patients and methods: after an ERCP session with difficult CBDS not completely removed, biliary FCSEMS (Wallflex were inserted in some patients when it was deemed that biliary sphincterotomy and a single plastic stent would not provide an adequate drainage. Results: a retrospective study was performed. Biliary FCSEMS were inserted in 29 patients, mean age 81 years. CBDS could not be extracted through a biliary sphincterotomy due to its large size (n = 18 or because of the presence of inflammatory distal strictures (n = 11. The greatest biliary drainage with shortest ERCP time was considered mandatory due to clinical instability of patients and/or poor tolerance to conscious sedation administered by the endoscopist. Successful biliary drainage was obtained in all cases. FCSEMS were removed after a median of 199.5 days in 16 patients with a complete CBDS extraction in 15 (93.7%. FCSEMS were not removed in the remaining 13 patients due to their clinical condition, and a wait-and-see strategy was undertaken. Conclusions: in selected cases, utilization of removable FCSEMS can be a good option for a quick and adequate biliary drainage in the setting of difficult CBDS. Because of the higher cost of these stents its use needs to be individualized.Introducción y objetivos: las prótesis biliares plásticas suelen emplearse tras una sesión de CPRE sin extracción completa de coledocolitiasis. En ocasiones, el calibre de drenaje con estas prótesis puede ser insuficiente. Presentamos nuestra experiencia en la utilización de prótesis metálicas autoexpandibles totalmente recubiertas (PMATR en

  5. Status of the CNES-CEA joint program on space nuclear Brayton systems

    International Nuclear Information System (INIS)

    A cooperative program between the French Centre National d'Etudes Spatiales (CNES) and the Commissariat a l'Energie Atomique (CEA) was initiated in 1983, to investigate the possible development of 20 to 200 kWe space nuclear power systems to be launched by the next version of the European launcher, Ariane V. After completion in 1986 of preliminary conceptual studies of a reference 200 kWe turbo-electric power system, an additional 3 year study phase was decided, with the double objective of assessing the potential advantage of nuclear power systems versus solar photovoltaic or dynamic systems in the 20 kWe power range, and comparing various reactor candidate technologies and system options for 20 kWe space nuclear power systems, likely to meet the projected energy needs of future European space missions. A comprehensive program including conceptual design studies, operating transient analyses and technology base assessment, is currently applied to a few reference concepts of 20 kWe nuclear Brayton and thermoelectric systems, in order to establish sound technical and economical bases for selecting the design options and the development strategy of a first space nuclear power system in Europe

  6. Design and optimization of a single stage centrifugal compressor for a solar dish-Brayton system

    Science.gov (United States)

    Wang, Yongsheng; Wang, Kai; Tong, Zhiting; Lin, Feng; Nie, Chaoqun; Engeda, Abraham

    2013-10-01

    According to the requirements of a solar dish-Brayton system, a centrifugal compressor stage with a minimum total pressure ratio of 5, an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed. A single stage, which consists of impeller, radial vaned diffuser, 90° crossover and two rows of axial stators, was chosen to satisfy this system. To achieve the stage performance, an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program. Radial vaned diffuser was applied downstream of the impeller. Two rows of axial stators after 90° crossover were added to guide the flow into axial direction. Since jet-wake flow, shockwave and boundary layer separation coexisted in the impeller-diffuser region, optimization on the radius ratio of radial diffuser vane inlet to impeller exit, diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point. Finally, an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance. Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6. The surge margin was 15%. The performance map including 80%, 90% and 100% design speed was also presented.

  7. A Mass Computation Model for Lightweight Brayton Cycle Regenerator Heat Exchangers

    Science.gov (United States)

    Juhasz, Albert J.

    2010-01-01

    Based on a theoretical analysis of convective heat transfer across large internal surface areas, this paper discusses the design implications for generating lightweight gas-gas heat exchanger designs by packaging such areas into compact three-dimensional shapes. Allowances are made for hot and cold inlet and outlet headers for assembly of completed regenerator (or recuperator) heat exchanger units into closed cycle gas turbine flow ducting. Surface area and resulting volume and mass requirements are computed for a range of heat exchanger effectiveness values and internal heat transfer coefficients. Benefit cost curves show the effect of increasing heat exchanger effectiveness on Brayton cycle thermodynamic efficiency on the plus side, while also illustrating the cost in heat exchanger required surface area, volume, and mass requirements as effectiveness is increased. The equations derived for counterflow and crossflow configurations show that as effectiveness values approach unity, or 100 percent, the required surface area, and hence heat exchanger volume and mass tend toward infinity, since the implication is that heat is transferred at a zero temperature difference. To verify the dimensional accuracy of the regenerator mass computational procedure, calculation of a regenerator specific mass, that is, heat exchanger weight per unit working fluid mass flow, is performed in both English and SI units. Identical numerical values for the specific mass parameter, whether expressed in lb/(lb/sec) or kg/ (kg/sec), show the dimensional consistency of overall results.

  8. Numerical simulations of LNG vapor dispersion in Brayton Fire Training Field tests with ANSYS CFX

    International Nuclear Information System (INIS)

    Federal safety regulations require the use of validated consequence models to determine the vapor cloud dispersion exclusion zones for accidental liquefied natural gas (LNG) releases. One tool that is being developed in industry for exclusion zone determination and LNG vapor dispersion modeling is computational fluid dynamics (CFD). This paper uses the ANSYS CFX CFD code to model LNG vapor dispersion in the atmosphere. Discussed are important parameters that are essential inputs to the ANSYS CFX simulations, including the atmospheric conditions, LNG evaporation rate and pool area, turbulence in the source term, ground surface temperature and roughness height, and effects of obstacles. A sensitivity analysis was conducted to illustrate uncertainties in the simulation results arising from the mesh size and source term turbulence intensity. In addition, a set of medium-scale LNG spill tests were performed at the Brayton Fire Training Field to collect data for validating the ANSYS CFX prediction results. A comparison of test data with simulation results demonstrated that CFX was able to describe the dense gas behavior of LNG vapor cloud, and its prediction results of downwind gas concentrations close to ground level were in approximate agreement with the test data.

  9. Acacia: A small scale power plant with pebble bed cartridge reactor and indirect Brayton cycle

    International Nuclear Information System (INIS)

    For markets other than large-scale electricity production a 60 MWth, 23 MWe (max.) nuclear plant design with an indirect Brayton cycle is proposed for application on the short to medium term. The reactor will be cooled by helium, whereas for the secondary cycle nitrogen is proposed as a heat carrier. In this way, a conventional air based gas turbine can be applied, while at the same time excluding the scenario of air ingress in the reactor core through a heat exchanger leak. Two variations of cycle design will be discussed: co-generation and maximized electricity production. The cogeneration mode will be elaborated for the application of seawater desalination. The reactor core geometry is annular with a central graphite reflector region, creating an optimal location for burnable poison. Optimization calculations on burnable poison distribution show that burnup of fuel and poison are balancing each other into a fairly constant reactivity behaviour during the entire core lifetime. Also, the two most important safety transient scenarios for pebble bed reactors, Pressurised and Depressurised Loss Of Forced Cooling, will be discussed. It will be shown that the maximum fuel temperatures will stay below the level where fuel damage starts for any point in time. (author)

  10. Finite-thermal reservoir effects on ecologically optimized closed regenerative Joule-Brayton power cycles

    Energy Technology Data Exchange (ETDEWEB)

    Khaliq, A. [Jamia Millia Islamia, New Delhi (India). Dept. of Mechanical Engineering

    2006-07-01

    A finite-time thermodynamic analysis based on a new kind of optimization criterion has been carried out for an endoreversible and regenerative Joule-Brayton power cycle coupled with variable temperature thermal reservoirs. The optimal performance and design parameters that maximize the ecological function are investigated. In this context, the optimal temperatures of the working fluid, the optimum power output, the optimum thermal efficiency, and the optimum second-law efficiency are determined in terms of technical parameters. Results are reported for the effect of regeneration, hot-cold temperature ratio, and the number of heat transfer units in hot and cold exchangers on the optimal performance parameters. The power and efficiency at maximum ecological function are found to be less than the maximum power and Curzon-Ahlborn efficiency. Power output increases significantly with increasing hot-cold side temperature ratio. However, it slightly increased as the number of heat transfer units in the regenerator increases. The optimization of ecological function leads to the improvement in exergetic efficiency and thermal efficiency, especially for low hot-cold side temperature ratios. Moreover, the thermal efficiency at maximum ecological function is less than the average of the finite time or maximum power efficiency and reversible Carnot efficiency. (author)

  11. Optimization of a Brayton cryocooler for ZBO liquid hydrogen storage in space

    Science.gov (United States)

    Deserranno, D.; Zagarola, M.; Li, X.; Mustafi, S.

    2014-11-01

    NASA is evaluating and developing technology for long-term storage of cryogenic propellant in space. A key technology is a cryogenic refrigerator which intercepts heat loads to the storage tank, resulting in a reduced- or zero-boil-off condition. Turbo-Brayton cryocoolers are particularly well suited for cryogen storage applications because the technology scales well to high capacities and low temperatures. In addition, the continuous-flow nature of the cycle allows direct cooling of the cryogen storage tank without mass and power penalties associated with a cryogenic heat transport system. To quantify the benefits and mature the cryocooler technology, Creare Inc. performed a design study and technology demonstration effort for NASA on a 20 W, 20 K cryocooler for liquid hydrogen storage. During the design study, we optimized these key components: three centrifugal compressors, a modular high-capacity plate-fin recuperator, and a single-stage turboalternator. The optimization of the compressors and turboalternator were supported by component testing. The optimized cryocooler has an overall flight mass of 88 kg and a specific power of 61 W/W. The coefficient of performance of the cryocooler is 23% of the Carnot cycle. This is significantly better performance than any 20 K space cryocooler existing or under development.

  12. High Temperature Fusion Reactor Cooling Using Brayton Cycle Based Partial Energy Conversion

    Science.gov (United States)

    Juhasz, Albert J.; Sawicki, Jerzy T.

    2003-01-01

    For some future space power systems using high temperature nuclear heat sources most of the output energy will be used in other than electrical form, and only a fraction of the total thermal energy generated will need to be converted to electrical work. The paper describes the conceptual design of such a partial energy conversion system, consisting of a high temperature fusion reactor operating in series with a high temperature radiator and in parallel with dual closed cycle gas turbine (CCGT) power systems, also referred to as closed Brayton cycle (CBC) systems, which are supplied with a fraction of the reactor thermal energy for conversion to electric power. Most of the fusion reactor's output is in the form of charged plasma which is expanded through a magnetic nozzle of the interplanetary propulsion system. Reactor heat energy is ducted to the high temperature series radiator utilizing the electric power generated to drive a helium gas circulation fan. In addition to discussing the thermodynamic aspects of the system design the authors include a brief overview of the gas turbine and fan rotor-dynamics and proposed bearing support technology along with performance characteristics of the three phase AC electric power generator and fan drive motor.

  13. Estudio de la eficiencia del ciclo de un motor de encendido Por chispa de 5 tiempos

    OpenAIRE

    Mad riñán Molina, Santiago

    2015-01-01

    El presente trabajo tiene por objetivo estudiar de forma teórica y experimental la eficiencia de un motor que opere en un ciclo de 5 tiempos (ciclo Otto más una carrera de expansión adicional). Para desarrollar el estudio se realizó una simulación cero-dimensional utilizando el modelo de gas ideal para un motor de 5 tiempos y se comparó con su equivalente de 4 tiempos. Posteriormente se ejecutó la fase experimental en la cual fue necesario adaptar un banco de pruebas, en el cua...

  14. El ciclo económico en el Perú.

    OpenAIRE

    Marco Terrones; César Calderón

    1993-01-01

    El estudio realiza una caracterización del ciclo económico en el Perú, usando información de los últimos cincuenta años. Se ha estudiado el comportamiento cíclico de los principales precios y agregados macroeconómico (reales y monetarios) de la economía peruana. Se encuentra que, a partir de 1978 y como resultado de la crisis derivada del problema de la deuda externa, la estructura del ciclo económico en el Perú experimenta un cambio, observándose una mayor volatilidad absoluta de la mayoría ...

  15. Propuesta de Ciclo de vida de los proyectos de Desarrollo Empresarial

    OpenAIRE

    Antonio M. Navarro López

    2009-01-01

    Todo proyecto se divide en distintas fases, habitualmente secuenciales, que permiten un control sobre la evolución del proyecto y habilitan su gestión. El conjunto de fases de un proyecto se denomina "ciclo de vida"; de un proyecto, se expone una serie de puntos de vista de diferentes autores sobre el ciclo de vida de los proyectos, incluyendo la caracterización que el autor propone para los proyectos de Desarrollo Empresarial que aplican el Perfeccionamiento Empresarial y que gestionan la In...

  16. Estrategias alternativas en el ciclo de vida de tres hormigas mediterráneas

    OpenAIRE

    Cerdá, Xim; Retana Alumbreros, Javier

    1992-01-01

    Se ha estudiado el ciclo biológico de tres especies de hormigas mediterráneas, y se han constatado importantes diferencias entre ellas. Cataglyphis cursor hibema sin descendencia y completa un ciclo de nidada entre los meses de abril y septiembre. Aphaenogaster senilis hibema sin nidada y produce pupas durante un amplio periodo de tiempo, desde abril hasta octubre, aunque los valores mtiximos (que coinciden con el pico de actividad exterior) se dan en primavera y principio de verano. Ambas es...

  17. L’ipotesi del ciclo vitale, la politica fiscale e la previdenza sociale

    Directory of Open Access Journals (Sweden)

    Tullio Jappelli

    2005-06-01

    Full Text Available Il lavoro riassume le principali implicazioni dell’ipotesi del ciclo vitale per quanto riguarda il risparmio individuale e aggregato, la politica fiscale e la previdenza sociale, soffermandosi sui contributi più importanti di Modigliani su questi temi. Anche se non è facile conciliare alcuni risultati empirici recenti con l’ipotesi del ciclo vitale, soprattutto gli aspetti di inerzia, miopia e comportamento irrazionale documentati nella letteratura comportamentale, gli studi di Modigliani rappresentano ancora oggi la base di riferimento principale per studiare le decisioni dirisparmio individuali e per operare scelte di politica economica.

  18. Ciclo de desarrollo de Trigona (Tetragonisca angustula, Latreille 1811 (Hymenoptera, Trigonini

    Directory of Open Access Journals (Sweden)

    Villa Lopera Antonio

    1989-06-01

    Full Text Available

    Se estudió el ciclo de desarrollo de una abeja sin aguijón: Trigona (Tetragonisca angustula. Latreille 1811 (Hymenoptera. Trigonini. Los resultados fueron los siguientes: El periodo comprendido entre la postura del huevo y la emergencia del imago, es, en las obreras, de 36.5 días en promedio. La duración del ciclo se hace mayor a medida que las celdas se alejan del centro del panal. Se determinaron 3 instares larvales y 5 fases pupales para obreras.

  19. Ciclo vital da família e envelhecimento: contextos e desafios

    OpenAIRE

    Maria Henriqueta de Jesus Silva Figueiredo; Maria Manuela Ferreira Pereira da Silva Martins; Luzia Wilma Santana da Silva; Palmira da Conceição Martins de Oliveira

    2011-01-01

    Os focos dos cuidados de enfermagem têm vindo a apresentar configurações diferentes face às mudanças sociais que exigem novas necessidades de saúde. O ciclo vital da família caracteriza-se por padrões de regularidade funcional, associados às funções, estrutura e processos interacionais. Nesta perspectiva a compreensão destes padrões na última etapa do ciclo vital, que se caracteriza pela adaptação ao envelhecimento, permitirá interacções mais ajustadas à promoção da saúde familiar....

  20. Identificación de nuevos reguladores del ciclo celular en Schizosaccharmoyces Pombe

    OpenAIRE

    Chica Balaguera, Nathalia

    2014-01-01

    [ES] Los complejos CDK-ciclina controlan el ciclo celular eucariótico y en el caso de S. pombe una única CDK, llamada cdc2, es suficiente para regularlo. Los niveles de la CDK varían a lo largo del ciclo celular y a su vez confiere direccionalidad a los eventos que lo componen. Uno de los sistemas de control de los niveles de actividad mas estudiado en este organismo, comprende la activación e inactivación de la CDK por parte de la quinasa Wee1 y la fosfatasa Cdc25 respectivamente, durante la...

  1. Reseña del ciclo Escuelas Argentinas emitido por Canal Encuentro

    OpenAIRE

    Trotta, Lucía; Santucci, Claudia

    2010-01-01

    El ciclo Escuelas Argentinas, como el plural de su título lo indica, hace referencia a la diversidad de experiencias educativas. La idea central no consiste en hablar del modelo de escuela argentina tradicional sino de la forma particular que adquiere la institución escuela en cada contexto en el que está inmersa. Escuelas Argentinas consta de dos temporadas con 13 capítulos cada una, de 30 minutos de duración. La producción fue dirigida por Bruno Stagnaro entre los años 2006 y 2008. El ciclo...

  2. Endeudamiento y ciclos políticos presupuestarios : el caso de los ayuntamientos catalanes

    OpenAIRE

    Escudero Fernández, Pedro; Prior Jiménez, Diego

    2002-01-01

    Este trabajo de investigación se dirige sobre el ámbito de los gobiernos locales y su objetivo es el de analizar cuál es el papel del endeudamiento en los ciclos políticos presupuestarios, contrastando si, en la utilización de este instrumento financiero, se da una distribución temporal estratégica en torno a las citas electorales, y si la existencia de estos ciclos puede resultar un factor explicativo del endeudamiento acumulado en los gobiernos locales. Para el contraste empírico se utiliza...

  3. Use of RELAP5-3D for Dynamic Analysis of a Closed-Loop Brayton Cycle Coupled To a Nuclear Reactor

    International Nuclear Information System (INIS)

    This paper describes results of a dynamic system model for a pair of closed Brayton-cycle (CBC) loops running in parallel that are connected to a nuclear gas reactor. The model assumes direct coupling between the reactor and the Brayton-cycle loops. The RELAP5-3D (version 2.4.1) computer program was used to perform the analysis. Few reactors have ever been coupled to closed Brayton-cycle systems. As such their behavior under dynamically varying loads, startup and shut down conditions, and requirements for safe and autonomous operation are largely unknown. The model described in this paper represents the reactor, turbine, compressor, recuperator, heat rejection system and alternator. The initial results of the model indicate stable operation of the reactor-driven Brayton-cycle system. However, for analysts with mostly pressurized water reactor experience, the Brayton cycle loops coupled to a gas-cooled reactor also indicate some counter-intuitive behavior for the complete coupled system. This model has provided crucial information in evaluating the reactor design and would have been further developed for use in developing procedures for safe start up, shut down, safe-standby, and other autonomous operating modes had the plant development cycle been completed

  4. Thermal analysis on N2 and S-CO2 Brayton cycle for the energy conversion system of small scale ultra-long cycle fast reactor

    International Nuclear Information System (INIS)

    An ultra-long cycle fast reactor (UCFR) is one of the SFR designs operating in a long cycle without refueling. The operational mechanism of long cycle fast reactor is once-through fuel cycle through breed and burn system. The benefits of long cycle fast reactor include capital/operation cost reductions, low proliferation risk, and the interim storage of light water reactor (LWR) spent fuel. For the power conversion system of next generation nuclear reactor, Brayton cycle has been mainly considered. Brayton cycle not only increases overall thermal efficiency in corresponding temperature range of GenIV reactors, but also solves sodium-water reaction issues. As a working fluid in Brayton cycle, many inactive gases are selected. For the power conversion system of next generation nuclear reactor, Brayton cycle has been mainly considered. Among the candidates for working fluid in Brayton power cycle, S-CO2 and N2 are analyzed in thermal aspect. For the major parameters including maximum system pressure, isentropic efficiencies of compressor and turbine, and pinch point, S-CO2 cycle shows the highest thermal performance. However, N2 cycle without intermediate loop gives comparable thermal performance, if high pressure around 70 bar and high isentropic efficiency of each component are maintained

  5. Gasification integrated to combined cycles; Gasificacion integrada a ciclos combinados

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez M, Manuel F; Alcaraz C, Agustin M [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2001-07-01

    de metales. Finalmente, en los nuevos esquemas de refinacion del petroleo se preve utilizar la coquizacion para aprovechar mejor el ondo de barril. El residuo producto de este proceso, conocido como coque de refineria, tiene un bajo valor comercial, un poder calorifico elevado y un alto contenido de azufre y metales. La gasificacion ha sido desarrollada en las ultimas dos decadas, en los paises altamente industrializados, como una alternativa para la generacion eficiente y limpia de electricidad a partir de combustibles sucios, asi como para la obtencion de ciertos combustibles en lugares donde no se tiene acceso al petroleo, pero si al carbon. Esta tecnologia cumple los reglamentos mas estrictos del mundo en lo que a emisiones contaminantes se refiere y es la unica solucion, junto a los lechos fluidizados, para los problemas que presentan algunos combustibles que son dificiles de quemar con tecnologias convencionales, como el carbon mineral, el coque de petroleo e incluso los residuos liquidos de la refinacion. Con base en los anterior, es posible pensar en la integracion de esta tecnologia a una planta de ciclo combinado para la generacion de electricidad o a una refineria generando vapor, energia electrica, hidrogeno y otros insumos a un costo competitivo, de manera tal que se resuelven los problemas de manejo y almacenamiento de los residuos; por otro lado se maximiza el aprovechamiento de los recursos energeticos primarios en el pais.

  6. Performance characteristics of an irreversible regenerative magnetic Brayton refrigeration cycle using Gd0.74Tb0.26 as the working substance

    Science.gov (United States)

    Diguet, Gildas; Lin, Guoxing; Chen, Jincan

    2012-10-01

    The cycle model of an irreversible regenerative magnetic Brayton refrigerator using Gd0.74Tb0.26 as the working substance is established. Based on the experimental characteristics of iso-field heat capacities of the material Gd0.74Tb0.26 at 0 T and 2 T, the corresponding iso-field entropies are calculated and the thermodynamic performance of an irreversible regenerative magnetic Brayton refrigeration cycle is investigated. The effects of the irreversibilities in the two adiabatic processes and non-perfect regenerative process of the magnetic Brayton refrigeration cycle on the cooling quantity, the heat quantity released to the hot reservoir, the net cooling quantity and the coefficient of performance are discussed in detail. Some significant results are obtained.

  7. Avaliação de Ciclo de Vida: Ferramenta do Pensamento Sistêmico

    Directory of Open Access Journals (Sweden)

    Maria Beatriz Maury de Carvalho

    2010-10-01

    Full Text Available RESENHA CALDEIRA-PIRES Armando, SOUZA-PAULA Maria Carlota de, VILAS BOAS Roberto C. (orgs. Avaliação do Ciclo de Vida a ISO 14040 na America Latina. Brasília: Abipti, 2005, 337 p. 21,5 cm. Apoio CNPq, CYTED, UnB. ISBN 85-89263-04-5.

  8. Preliminary design of a Brayton cycle as a standalone Decay Heat Removal system for the Gas-cooled Fast Reactor

    International Nuclear Information System (INIS)

    This paper reports a preliminary design study of a Brayton cycle which would be a dedicated, standalone Decay Heat Removal (DHR) loop of the Gas-cooled Fast Reactor (GFR). In comparison to the DHR reference strategy developed during the GFR pre-conceptual design phase (which was completed by the CEA at the end of 2007), the salient feature of this alternative device would be to combine the energetic autonomy of the natural convection process - which is foreseen for operation at high and medium pressures - to the efficiency of the forced convection process which is foreseen for operation down to very low pressures. An analytical model, the so-called 'Brayton scoping' model, is described in the paper. This is based on simplified thermodynamical and aerodynamical equations and was developed to highlight design choices. First simulations of the proposed device's performance during loss-of-coolant-accident (LOCA) transients have been performed using the CATHARE code, and these are also reported. Analysis of the simulation results are consistent with the first insights obtained from usage of the 'Brayton scoping' model, e.g. the turbomachine accelerates during the depressurization process to tend towards a steady rotational speed value which is inversely proportional to the pressure. For small break LOCA events, the device operates successfully as regards its safety function and delivers to the core a relatively unperturbed cooling mass flowrate as a function of pressure change. However, further studies are required for medium to large break sizes, since certain stability concerns have been met in such cases. For example, an unexpected turbomachine stoppage was induced during the transients, resulting in loss of the necessary core cooling mass flow. (author)

  9. Modeling the small-scale dish-mounted solar thermal Brayton cycle

    Science.gov (United States)

    Le Roux, Willem G.; Meyer, Josua P.

    2016-05-01

    The small-scale dish-mounted solar thermal Brayton cycle (STBC) makes use of a sun-tracking dish reflector, solar receiver, recuperator and micro-turbine to generate power in the range of 1-20 kW. The modeling of such a system, using a turbocharger as micro-turbine, is required so that optimisation and further development of an experimental setup can be done. As a validation, an analytical model of the small-scale STBC in Matlab, where the net power output is determined from an exergy analysis, is compared with Flownex, an integrated systems CFD code. A 4.8 m diameter parabolic dish with open-cavity tubular receiver and plate-type counterflow recuperator is considered, based on previous work. A dish optical error of 10 mrad, a tracking error of 1° and a receiver aperture area of 0.25 m × 0.25 m are considered. Since the recuperator operates at a very high average temperature, the recuperator is modeled using an updated ɛ-NTU method which takes heat loss to the environment into consideration. Compressor and turbine maps from standard off-the-shelf Garrett turbochargers are used. The results show that for the calculation of the steady-state temperatures and pressures, there is good comparison between the Matlab and Flownex results (within 8%) except for the recuperator outlet temperature, which is due to the use of different ɛ-NTU methods. With the use of Matlab and Flownex, it is shown that the small-scale open STBC with an existing off-the-shelf turbocharger could generate a positive net power output with solar-to-mechanical efficiency of up to 12%, with much room for improvement.

  10. Transient analysis of an FHR coupled to a helium Brayton power cycle

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Minghui [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Kim, In Hun [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Sun, Xiaodong [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Christensen, Richard [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Utgikar, Vivek [Univ. of Idaho, Idaho Falls, ID (United States); Sabharwall, Piyush [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-08-01

    The Fluoride salt-cooled High-temperature Reactor (FHR) features a passive decay heat removal system and a high-efficiency Brayton cycle for electricity generation. It typically employs an intermediate loop, consisting of an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX), to couple the primary system with the power conversion unit (PCU). In this study, a preliminary dynamic system model is developed to simulate transient characteristics of a prototypic 20-MWth Fluoride salt-cooled High-temperature Test Reactor (FHTR). The model consists of a series of differential conservation equations that are numerically solved using the MATLAB platform. For the reactor, a point neutron kinetics model is adopted. For the IHX and SHX, a fluted tube heat exchanger and an offset strip-fin heat exchanger are selected, respectively. Detailed geometric parameters of each component in the FHTR are determined based on the FHTR nominal steady-state operating conditions. Three initiating events are simulated in this study, including a positive reactivity insertion, a step increase in the mass flow rate of the PCU helium flow, and a step increase in the PCU helium inlet temperature to the SHX. The simulation results show that the reactor has inherent safety features for those three simulated scenarios. It is observed that the increase in the temperatures of the fuel pebbles and primary coolant is mitigated by the decrease in the reactor power due to negative temperature feedbacks. The results also indicate that the intermediate loop with the two heat exchangers plays a significant role in the transient progression of the integral reactor system.

  11. Innovative biomass to power conversion systems based on cascaded supercritical CO2 Brayton cycles

    International Nuclear Information System (INIS)

    In the small to medium power range the main technologies for the conversion of biomass sources into electricity are based either on reciprocating internal combustion or organic Rankine cycle engines. Relatively low energy conversion efficiencies are obtained in both systems due to the thermodynamic losses in the conversion of biomass into syngas in the former, and to the high temperature difference in the heat transfer between combustion gases and working fluid in the latter. The aim of this paper is to demonstrate that higher efficiencies in the conversion of biomass sources into electricity can be obtained using systems based on the supercritical closed CO2 Brayton cycles (s-CO2). The s-CO2 system analysed here includes two cascaded supercritical CO2 cycles which enable to overcome the intrinsic limitation of the single cycle in the effective utilization of the whole heat available from flue gases. Both part-flow and simple supercritical CO2 cycle configurations are considered and four boiler arrangements are investigated to explore the thermodynamic performance of such systems. These power plant configurations, which were never explored in the literature for biomass conversion into electricity, are demonstrated here to be viable options to increase the energy conversion efficiency of small-to-medium biomass fired power plants. Results of the optimization procedure show that a maximum biomass to electricity conversion efficiency of 36% can be achieved using the cascaded configuration including a part flow topping cycle, which is approximately 10%-points higher than that of the existing biomass power plants in the small to medium power range. - Highlights: • Supercritical CO2 cycles are proposed for biomass to electricity conversion. • Four boiler design options are considered. • High total system efficiency is due to the part-flow cascaded configuration. • The efficiency is higher than that of other small/medium size alternative systems

  12. Development of 0.5-5 W, 10K Reverse Brayton Cycle Cryocoolers - Phase II Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Doty, F. D.; Boman, A.; Arnold, S.; Spitzmesser, J. B.; Jones, D.; McCree, D.; Hacker, L. J.

    2001-10-15

    Miniature cryocoolers for the 8-30 K range are needed to provide 0.5-5 w of cooling to high sensitivity detectors (for long-wave-length IR, magnetism, mm-wave, X-ray, dark matter, and possibly y-ray detection) while maintaining low mass, ultra-low vibration, and good efficiency. This project presents a new approach to eliminating the problems normally encountered in efforts to build low-vibration, fieldable, miniature cryocoolers. Using the reverse Brayton Cycle (RBC), the approach applies and expands on existing spinner technology previously used only in Nuclear Magnetic Resonance (NMR) probes.

  13. A review of test results on solar thermal power modules with dish-mounted Stirling and Brayton cycle engines

    Science.gov (United States)

    Jaffe, Leonard D.

    1988-01-01

    This paper presents results of development tests of various solar thermal parabolic dish modules and assemblies that used dish-mounted Brayton or Stirling cycle engines for production of electric power. These tests indicate that early modules achieve net efficiencies up to 29 percent in converting sunlight to electricity, as delivered to the grid. Various equipment deficiencies were observed and a number of malfunctions occurred. The performance measurements, as well as the malfunctions and other test experience, provided information that should be of value in developing systems with improved performance and reduced maintenance.

  14. The efficiency of an open-cavity tubular solar receiver for a small-scale solar thermal Brayton cycle

    International Nuclear Information System (INIS)

    Highlights: • Results show efficiencies of a low-cost stainless steel tubular cavity receiver. • Optimum ratio of 0.0035 is found for receiver aperture area to concentrator area. • Smaller receiver tube and higher mass flow rate increase receiver efficiency. • Larger tube and smaller mass flow rate increase second law efficiency. • Large-tube receiver performs better in the small-scale solar thermal Brayton cycle. - Abstract: The first law and second law efficiencies are determined for a stainless steel closed-tube open rectangular cavity solar receiver. It is to be used in a small-scale solar thermal Brayton cycle using a micro-turbine with low compressor pressure ratios. There are many different variables at play to model the air temperature increase of the air running through such a receiver. These variables include concentrator shape, concentrator diameter, concentrator rim angle, concentrator reflectivity, concentrator optical error, solar tracking error, receiver aperture area, receiver material, effect of wind, receiver tube diameter, inlet temperature and mass flow rate through the receiver. All these variables are considered in this paper. The Brayton cycle requires very high receiver surface temperatures in order to be successful. These high temperatures, however, have many disadvantages in terms of heat loss from the receiver, especially radiation heat loss. With the help of ray-tracing software, SolTrace, and receiver modelling techniques, an optimum receiver-to-concentrator-area ratio of A′ ≈ 0.0035 was found for a concentrator with 45° rim angle, 10 mrad optical error and 1° tracking error. A method to determine the temperature profile and net heat transfer rate along the length of the receiver tube is presented. Receiver efficiencies are shown in terms of mass flow rate, receiver tube diameter, pressure drop, maximum receiver surface temperature and inlet temperature of the working fluid. For a 4.8 m diameter parabolic dish, the

  15. Effects of backlash and dead band on temperature control of the primary loop of a conceptual nuclear Brayton space powerplant

    Science.gov (United States)

    Petrick, E. J.

    1973-01-01

    An analytical study was made of the stability of a closed-loop liquid-lithium temperature control of the primary loop of a conceptual nuclear Brayton space powerplant. The operating point was varied from 20 to 120 percent of design. A describing-function technique was used to evaluate the effects of temperature dead band and control coupling backlash. From the system investigation, it was predicted that a limit cycle will not exist with a temperature dead band, but a limit cycle will not exist when backlash is present. The results compare favorably with a digital computer simulation.

  16. El ciclo celular y su papel en el desarrollo, crecimiento, restitución y reparación de tejidos. Propuesta de aula para los estudiantes de ciclo tres

    OpenAIRE

    Peña Cruz, Yeny Yubely

    2013-01-01

    La propuesta de aula: el ciclo celular y su papel en el desarrollo, crecimiento, restitución y reparación de tejidos, es diseñada para estudiantes de ciclo tres, tiene como población de estudio, los estudiantes de grado séptimo de la institución educativa Jesús María Aguirre Charry, La propuesta de aula se inicia con un diagnóstico de los conceptos previos esenciales para la comprensión del ciclo celular; a partir del cual se definen los problemas cognitivos presente en los estudiantes. Duran...

  17. Sincronización de los Ciclos Económicos: el Caso de Colombia, Ecuador y Venezuela

    Directory of Open Access Journals (Sweden)

    Salamanca Lugo Andrés

    2012-11-01

    Full Text Available

    En este documento se investiga acerca de la existencia y la identificación de un ciclo 
    económico común entre Colombia, Ecuador y Venezuela. Se busca una evidencia de la
    sincronización de los ciclos económicos de estos países, a través de diferentes medidas 
    no paramétricas, en conformidad con los ciclos y mediante la construcción de un ciclo 
    común de referencia. De acuerdo con esto, se ajusta un modelo de Markov-Switching
    autoregresivo multivariado (MS-VAR que confirma la existencia de dicho ciclo
    Finalmente, la cronología del ciclo común es reconstruida a partir de las probabilidades 
    suavizadas del modelo y es contrastada con el ciclo común de referencia.

  18. An isotope heat source integrated with a 7 kW/e/ to 25 kW/e/ Brayton cycle space power supply.

    Science.gov (United States)

    Ryan, R. L.; Graham, J. W.; Coombs, M. G.; Bloomfield, H. S.

    1972-01-01

    The power system described is intended for applications in a manned space mission. The Isotope Reentry Vehicle (IRV) developed is considered together with the Heat Source (HS), the Heat Source Heat Exchanger and the Brayton Cycle Power Conversion Module. Other subjects discussed include the IRV/Brayton cycle spacecraft integration concept, abort and deorbit mechanization, emergency cooling methods, and crew shielding requirements. Mounting and integration for the IRV is to a large degree controlled by nuclear safety requirements. Another major factor in the installation concept is the type of emergency cooling or passive heat dump mode used in rejection of HS energy.

  19. Development and validation of models for simulation of supercritical carbon dioxide Brayton cycles and application to self-propelling heat removal systems in boiling water reactors

    OpenAIRE

    Venker, Jeanne

    2015-01-01

    The objective of the current work was to develop a model that is able to describe the transient behavior of supercritical carbon dioxide (sCO2) Brayton cycles, to be applied to self-propelling residual heat removal systems in boiling water reactors. The developed model has been implemented into the thermohydraulic system code ATHLET. By means of this improved ATHLET version, novel residual heat removal systems, which are based on closed sCO2 Brayton cycles, can be assessed as a retrofit measu...

  20. Psicología del ciclo vital: hacia una visión comprehensiva de la vida humana

    OpenAIRE

    Elisa Dulcey Ruiz; Cecilia Uribe Valdivieso

    2002-01-01

    Se propone que la psicología del ciclo vital es más amplia que la psicología del desarrollo. Coherente con una visión integral del curso del ciclo vital esta psicología enfatiza la irrelevancia de la edad, los cambios permanentes, la multidimensionalidad, y la plasticidad, también como la importancia del contexto y la historia. Se refiere al proceso de envejecimiento, a la adultez, la vejez y la muerte en el marco del ciclo vital; enfatiza posibilidades relacionadas con el enve...

  1. Psicología del ciclo vital: hacia una visión comprehensiva de la vida humana

    OpenAIRE

    Elisa Dulcey Ruiz; Cecilia Uribe Valdivieso

    2002-01-01

    Se propone que la psicología del ciclo vital es más amplia que la psicología del desarrollo. Coherente con una visión integral del curso del ciclo vital esta psicología enfatiza la irrelevancia de la edad, los cambios permanentes, la multidimensionalidad, y la plasticidad, también como la importancia del contexto y la historia. Se refiere al proceso de envejecimiento, a la adultez, la vejez y la muerte en el marco del ciclo vital; enfatiza posibilidades relacionadas con el envejecimiento exit...

  2. Influencia de las condiciones de curado en el comportamiento del hormigón sometido a ciclos hielo-deshielo

    OpenAIRE

    Al‐Assadi, Ghaida

    2009-01-01

    El efecto de los ciclos hielo-deshielo es una de las causas principales de la degradación del hormigón en las regiones frías. En Europa Central y Oriental las condiciones climáticas en el invierno son particularmente graves para el hormigón estructural. Los sucesivos ciclos de hielo-deshielo causan tanto el empeoramiento del hormigón externo como el daño interno. En una temporada de invierno habitual en estas zonas, puede haber más de 100 ciclos hielo-deshielo, con el consiguiente deterioro d...

  3. Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving VHTR Efficiency and Testing Material Compatibility - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Chang H. Oh

    2006-06-01

    Generation IV reactors will need to be intrinsically safe, having a proliferation-resistant fuel cycle and several advantages relative to existing light water reactor (LWR). They, however, must still overcome certain technical issues and the cost barrier before it can be built in the U.S. The establishment of a nuclear power cost goal of 3.3 cents/kWh is desirable in order to compete with fossil combined-cycle, gas turbine power generation. This goal requires approximately a 30 percent reduction in power cost for stateof-the-art nuclear plants. It has been demonstrated that this large cost differential can be overcome only by technology improvements that lead to a combination of better efficiency and more compatible reactor materials. The objectives of this research are (1) to develop a supercritical carbon dioxide Brayton cycle in the secondary power conversion side that can be applied to the Very-High-Temperature Gas-Cooled Reactor (VHTR), (2) to improve the plant net efficiency by using the carbon dioxide Brayton cycle, and (3) to test material compatibility at high temperatures and pressures. The reduced volumetric flow rate of carbon dioxide due to higher density compared to helium will reduce compression work, which eventually increase plant net efficiency.

  4. Optimum performance of the small-scale open and direct solar thermal Brayton cycle at various environmental conditions and constraints

    International Nuclear Information System (INIS)

    The Brayton cycle's heat source can be obtained from solar energy instead of the combustion of fuel. The irreversibilities of the open and direct solar thermal Brayton cycle with recuperator are mainly due to heat transfer across a finite temperature difference and fluid friction, which limit the net power output of such a system. In this work, the method of total entropy generation minimisation is applied to optimise the geometries of the receiver and recuperator at various steady-state weather conditions. For each steady-state weather condition, the optimum turbine operating point is also found. The authors specifically investigate the effect of wind and solar irradiance on the maximum net power output of the system. The effects of other conditions and constraints, on the maximum net power output, are also investigated. These include concentrator error, concentrator reflectivity and maximum allowable surface temperature of the receiver. Results show how changed solar beam irradiance and wind speed affect the system net power output and optimum operating point of the micro-turbine. A dish concentrator with fixed focal length, an off-the-shelf micro-turbine and a modified cavity receiver is considered. -- Highlights: ► An off-the-shelf micro-turbine and a modified cavity receiver are considered. ► We investigate the optimum operating point of micro-turbine in various situations. ► Optimum mass flow rate and exhaust temperature increase with beam irradiance. ► Optimum exhaust temperature increases as wind speed increases.

  5. Optimization performance and thermodynamic analysis of an irreversible nano scale Brayton cycle operating with Maxwell–Boltzmann gas

    International Nuclear Information System (INIS)

    Highlights: • Performance analysis of irreversible nano scale Brayton cycle operating with Maxwell–Boltzmann gas is studied. • Multi-objective optimization approach is carried out for performance optimization. • 3 decision-making methods are employed to select final answers. - Abstract: In last decades, nano technology developed. Since, nano scale thermal cycles will be possibly employed in the near future. In this research, a nano scale irreversible Brayton cycle is investigated thermodynamically for optimizing the performance of the aforementioned cycle. Ideal Maxwell–Boltzmann gas is employed as a working fluid in the system. In this paper, two scenarios are employed in the multi-objective optimization process; however, the outcomes of each of the scenarios are evaluated independently. In the first scenario, in order to maximize the dimensionless Maximum available work and energy efficiency of the system, multi-objective optimization algorithms is employed. Furthermore, in the second scenario, two objective functions comprising the dimensionless Maximum available work and the dimensionless Ecological function are maximized concurrently via employing multi objective optimization algorithms. The multi objective evolutionary approaches on the basis of non-dominated sorting genetic algorithm method are employed in this paper. Decision making is done via three methods including linear programming techniques for multidimensional analysis of preference and Technique for order of preference by similarity to ideal solution and Bellman–Zadeh. Finally, error analysis is implemented on the results obtained from each scenario

  6. An Experimental Programme to Evaluate the Feasibility of Jet Compressors for Closed Brayton Cycle MPD Systems

    International Nuclear Information System (INIS)

    The application of jet compressors to closed Brayton cycle MPD systems has been suggested previously. In the present paper the feasibility of jet compression for MPD systems is investigated and some preliminary test results from a single-stage jet compressor loop are given. Thepurposeoftheexperimentalprogrammeis, (1) to simulate the operation of a jet compressor under conditions comparable to those of an actual MPD plant, and (2) to study the physics of momentum transfer of two high velocity gas (or vapour) streams of very different molecular weights. A jet compressor in which both gases mix at equal forward velocity has the same theoretical compression ratio as a reversible engine. The upper limit for the compression ratio achievable for a given set of input parameters (stagnation properties of both gases) can be calculated from purely thermodynamic principles. The expressions for the performance of an ideal jet compressor were applied to two typical high temperature MPD cycles. The overall cycle efficiency is somewhat lower than obtainable with rotating machinery, but acceptable for special applications. In the experimental programme a single-stage test facility was designed and operated. The driving gas was caesium vapour, the driven gas helium. In the design of the system the objective was to simulate the temperatures, pressures and working media of an MPD plant on a small scale. The facility is capable of handling up to 12 g/sec of the primary stream (caesium) and up to 2.5 g of the secondary stream (helium). The caesium is fed by a diaphragm pump into a refractory metal boiler at a pressure of up to 8.0 atmospheres and then superheated to approximately 1700°K. The superheated vapour expands in a supersonic nozzle and transfers part of its momentum to the low temperature helium stream. The helium is circulated in a closed loop which is equipped with a throttle valve to simulate the pressure drop which would occur in an MPD generator. During some preliminary

  7. Proposal for an advanced heat source assembly for the Isotope Brayton Power System. Volume 1. Technical program and statement of work

    Energy Technology Data Exchange (ETDEWEB)

    1974-12-09

    The technical program plan for evaluating the performance and safety of a radioisotope-fueled Brayton power system for space vehicles is presented with schedules for evaluating heat source design and safety, for specifying power system requirements, and for the development and operation of a ground demonstration system. (LCL)

  8. Ciclo vital da família e envelhecimento: contextos e desafios

    Directory of Open Access Journals (Sweden)

    Maria Henriqueta de Jesus Silva Figueiredo

    2011-08-01

    Full Text Available Os focos dos cuidados de enfermagem têm vindo a apresentar configurações diferentes face às mudanças sociais que exigem novas necessidades de saúde. O ciclo vital da família caracteriza-se por padrões de regularidade funcional, associados às funções, estrutura e processos interacionais. Nesta perspectiva a compreensão destes padrões na última etapa do ciclo vital, que se caracteriza pela adaptação ao envelhecimento, permitirá interacções mais ajustadas à promoção da saúde familiar.

  9. Família e ciclo vital: a fase de aquisição

    OpenAIRE

    Juliana Peterle Ronchi; Luziane Zacché Avellar

    2011-01-01

    Esta pesquisa objetivou descrever as características da fase deaquisição, primeira fase do ciclo vital familiar, marcada pela uniãodo casal e a convivência com os filhos pequenos. O estudo foirealizado com 50 famílias de classe média, na fase de aquisição dociclo vital da família, da cidade de Vitória-ES. Os participantesresponderam ao questionário baseado na pesquisa Ciclo vital dafamília paulista, que se mostrou adequado para compreender adinâmica e os valores das famílias da cidade de Vitó...

  10. Caracterización de genes rsf implicados en el control del ciclo celular en levadura

    OpenAIRE

    Queralt Badía, Ethelvina

    2003-01-01

    En S. cerevisiae, al igual que en células de mamífero, el principal control durante el ciclo celular está situado al final de la fase G1, en un punto llamado START (Cross 1995). En START se coordina el crecimiento con la división celular la célula solo entrará en un nuevo ciclo celular si ha alcanzado un tamaño crítico y las condiciones medioambientales son apropiadas. Un proceso clave en START es la activación de un programa de transcripción específico de la fase G1 tardía. Dos factores de t...

  11. Ciclo y dinámica económica en Europa

    OpenAIRE

    Pérez Vázquez, Pedro José

    1999-01-01

    RESUMEN El objeto de estudio de la tesis son los ciclos económicos, realizándose cuatro estudios empíricos utilizando técnicas de series temporales. La tesis consta de cuatro capítulos, a los que se añade un apartado final de conclusiones El objetivo del primer capítulo es determinar si el ciclo económico es un fenómeno con características similares en las principales economías de mercado, para ello se caracterizan las propiedades cíclicas de un grupo amplio de países (países del G-7 má...

  12. Estudio termoeconómico de diferentes configuraciones de ciclo combinado integrado con una planta solar

    Directory of Open Access Journals (Sweden)

    María Dolores Durán García

    2014-01-01

    Full Text Available Se presenta el análisis termoeconómico de una planta de ciclo combinado integrada con una planta solar de canal parabólico, considerada como una sección de la caldera de recuperación de calor, con el objetivo de conseguir un diseño óptimo al determinar los parámetros de diseño optimizados para ambos sistemas. Se aplica una metodología empleada en trabajos previos para la optimización de ciclos combinados, pero ahora con una planta solar. Como resultado, a partir de un análisis de sensibilidad, se obtiene el desempeño de varias configuraciones bajo diferentes condiciones de radiación solar.

  13. Propuesta de Ciclo de vida de los proyectos de Desarrollo Empresarial

    Directory of Open Access Journals (Sweden)

    Antonio M. Navarro López

    2009-01-01

    Full Text Available Todo proyecto se divide en distintas fases, habitualmente secuenciales, que permiten un control sobre la evolución del proyecto y habilitan su gestión. El conjunto de fases de un proyecto se denomina "ciclo de vida"; de un proyecto, se expone una serie de puntos de vista de diferentes autores sobre el ciclo de vida de los proyectos, incluyendo la caracterización que el autor propone para los proyectos de Desarrollo Empresarial que aplican el Perfeccionamiento Empresarial y que gestionan la Innovación por Proyectos de Desarrollo. Definiéndose algunos de los Beneficios de la Gestión de proyectos.

  14. Currículo en el nivel preescolar costarricense: El Ciclo Materno Infantil (CMI

    Directory of Open Access Journals (Sweden)

    Ana Lucía Chaves Álvarez

    2009-12-01

    Full Text Available

    Recibido 20 de abril de 2009 • Aprobado 14 de setiembre de 2009 • Corregido 15 de octubre de 2009

     

    Resumen. Este artículo aborda la conceptuación y la descripción del Ciclo Materno Infantil como parte del nivel de preescolar del sistema educativo formal costarricense. Con el propósito de tener una visión más amplia de este Ciclo, se hace un repaso por el concepto de currículo, así como de los elementos que lo conforman, y, luego, se detallan específicamente los aspectos relacionados con el currículo de preescolar costarricense del Ciclo Materno Infantil, tomando como punto de partida el Programa de Estudio que se elaboró para atender este Ciclo en el sistema educativo de Costa Rica.

     

    Abstract. The present article tackles the conceptualization and description of the Infantile Maternal Cycle as p The present article tackles the conceptualization and description of the Infantile Maternal Cycle as part of the preschool level of the Costa Rican educational system. With the intention of having a wider vision of this Cycle, a revision is done for the curriculum concept, as well as, for the elements that shape it, and then there is a detailed description of specific aspects related to the preschool Costa Rican curriculum of the Infantile Maternal Cycle, taking as a starting point the Program of Study that was designed to attend the above Cycle in the Costa Rican educational system.

  15. La teoria del ciclo vitale del risparmio di Modigliani cinquant’anni dopo

    Directory of Open Access Journals (Sweden)

    Mauro Baranzini

    2012-04-01

    Full Text Available In the early 50s Franco Modigliani and Richard Brumberg and Albert Ando, ​​formulated the life-cycle theory of consumption and saving, which has been a huge success and undisputed for at least three decades. However, since the early 80s the life-cycle theory has been criticized in an increasingly tight for at least four reasons. The first is the existence of a significant intergenerational transmission of wealth, due to factors exogenous to the model of the life cycle. The second reason is the increasing evidence that the rich continue to save a greater extent than the less fortunate, as, in fact, Keynes argued. The third reason is that there is increasing evidence, at least in Western Europe and Japan, young families, during twenty and thirty years of age, save a positive and growing share of their income, which arises in decided contrast to the original version of the life-cycle theory. Finally, a number of empirical studies have found that retirees dismiss a high proportion of their income. This requires a serious rethinking of the approach of the life-cycle theory, which affects both the economic analysis and economic policy. Nei primi anni ’50 Franco Modigliani, insieme a Richard Brumberg e ad Albert Ando, formulò la teoria del ciclo vitale del consumo e del risparmio, che ha riscosso un enorme e indiscusso successo per almeno tre decenni. Tuttavia, a partire dai primi anni ’80 la teoria del ciclo vitale è stata criticata in modo sempre più serrato, per almeno quattro ragioni. La prima consiste nell’esistenza di una significativa trasmissione intergenerazionale della ricchezza, da ricondurre a cause esogene al modello del ciclo vitale. La seconda ragione è rappresentata dalla crescente evidenza che i ricchi continuano a risparmiare in misura maggiore rispetto ai meno fortunati, come, in effetti, Keynes sosteneva. Il terzo motivo è che vi sono prove sempre più evidenti, almeno nell’Europa occidentale e in Giappone

  16. Advanced thermal-energy-storage concept-definition study for solar Brayton power plants. Final technical report, Volume I

    Energy Technology Data Exchange (ETDEWEB)

    1976-01-01

    The detailed results are presented of a technical and economic assessment of phase change and thermochemical energy storage systems in a solar power plant employing a high temperature Brayton cycle thermal engine with helium as the heat transport fluid. The assessment included an examination of the storage system operation, efficiency, power plant interaction, design, materials, safety, maintenance, environmental impact, system life, and economics. These considerations are implemented in the conceptual design of three baseline storage systems and their components for use in a solar power plant module of 50 megawatt electrical power output. Rationale is provided to support the configuration, operation and material choices. A preliminary assessment of the technology development and experimental test program requirements are also included. The report is contained in four separate volumes. This volume is the technical report.

  17. Conceptual Design of S-CO{sub 2} Brayton Cycle Radial Turbomachinery for KAIST Micro Modular Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seongkuk; Kim, Seong Gu; Lee, Jekyoung; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-05-15

    KAIST proposed a new SMR design, which utilizes S-CO{sub 2} as the working fluid. It was named as KAIST MMR. Compared with existing SMR concepts, KAIST MMR has advantages of achieving smaller volume of power conversion unit (PCU) and containing the core and PCU in one vessel for the complete modularization. Authors noticed that the compressor and turbine assumed performances of KAIST MMR were conservatively selected previously. Thus, this paper tries to address the best estimate values of each turbomachinery in 10MWe class KAIST MMR. The turbomachinery size of the S-CO{sub 2} cycle is smaller than helium Brayton cycle and steam Rankine cycle. The suggested SMR concept adopts passive cooling system by using air. This method can cool reactor without external electricity supply. Small size and more flexible installation in the inland area will be necessary characteristics for the future nuclear application in the water limited region. KAIST MMR meets all these requirements by utilizing S-CO{sub 2} as a working fluid. This paper presents the work for further increasing the system performance by estimating the component efficiency more realistically. The cycle layout adopted for the application is S-CO{sub 2} recuperated Brayton cycle. The best efficiency of compressor and turbine was evaluated to be 84.94% and 90.94%, respectively. By using KAIST in-house code, thermal efficiency and net output were increased to 35.81% and 12.45MWe, respectively, for the same core thermal power. More refined cycle layout and suitable turbomachinery design will be performed in the near future.

  18. Supercritical CO2 Brayton power cycles for DEMO fusion reactor based on Helium Cooled Lithium Lead blanket

    International Nuclear Information System (INIS)

    Fusion energy is one of the most promising solutions to the world energy supply. This paper presents an exploratory analysis of the suitability of supercritical CO2 Brayton power cycles (S-CO2) for low-temperature divertor fusion reactors cooled by helium (as defined by EFDA). Integration of three thermal sources (i.e., blanket, divertor and vacuum vessel) has been studied through proposing and analyzing a number of alternative layouts, achieving an improvement on power production higher than 5% over the baseline case, which entails to a gross efficiency (before self-consumptions) higher than 42%. In spite of this achievement, the assessment of power consumption for the circulating heat transfer fluids results in a penalty of 20% in the electricity production. Once the most suitable layout has been selected an optimization process has been conducted to adjust the key parameters to balance performance and size, achieving an electrical efficiency (electricity without taking into account auxiliary consumptions due to operation of the fusion reactor) higher than 33% and a reduction in overall size of heat exchangers of 1/3. Some relevant conclusions can be drawn from the present work: the potential of S-CO2 cycles as suitable converters of thermal energy to power in fusion reactors; the significance of a suitable integration of thermal sources to maximize power output; the high penalty of pumping power; and the convenience of identifying the key components of the layout as a way to optimize the whole cycle performance. - Highlights: • Supercritical CO2 Brayton cycles have been proposed for BoP of HCLL fusion reactor. • Low temperature sources have been successfully integrated with high temperature ones. • Optimization of thermal sources integration improves 5% the electricity production. • Assessment of pumping power with sources and sink loops results on 20% of gross power. • Matching of key parameters has conducted to 1/3 of reduction in heat exchangers

  19. Operating conditions of an open and direct solar thermal Brayton cycle with optimised cavity receiver and recuperator

    International Nuclear Information System (INIS)

    The small-scale open and direct solar thermal Brayton cycle with recuperator has several advantages, including low cost, low operation and maintenance costs and it is highly recommended. The main disadvantages of this cycle are the pressure losses in the recuperator and receiver, turbomachine efficiencies and recuperator effectiveness, which limit the net power output of such a system. The irreversibilities of the solar thermal Brayton cycle are mainly due to heat transfer across a finite temperature difference and fluid friction. In this paper, thermodynamic optimisation is applied to concentrate on these disadvantages in order to optimise the receiver and recuperator and to maximise the net power output of the system at various steady-state conditions, limited to various constraints. The effects of wind, receiver inclination, rim angle, atmospheric temperature and pressure, recuperator height, solar irradiance and concentration ratio on the optimum geometries and performance were investigated. The dynamic trajectory optimisation method was applied. Operating points of a standard micro-turbine operating at its highest compressor efficiency and a parabolic dish concentrator diameter of 16 m were considered. The optimum geometries, minimum irreversibility rates and maximum receiver surface temperatures of the optimised systems are shown. For an environment with specific conditions and constraints, there exists an optimum receiver and recuperator geometry so that the system produces maximum net power output. -- Highlights: → Optimum geometries exist such that the system produces maximum net power output. → Optimum operating conditions are shown. → Minimum irreversibility rates and minimum entropy generation rates are shown. → Net power output was described in terms of total entropy generation rate. → Effects such as wind, recuperator height and irradiance were investigated.

  20. Os medos dos alunos do 1.º Ciclo do Ensino Básico

    OpenAIRE

    Roberto, Rafaela; Miranda, Tatiana; Bento CAVADAS

    2012-01-01

    O sentimento de medo pauta, desde o nascimento, vários momentos da vida do ser humano. Constitui, essencialmente, um mecanismo de sobrevivência. O objetivo fulcral deste estudo foi identificar os medos dos alunos do 1.º Ciclo do Ensino Básico. Como as representações iconográficas são um meio da criança relatar com mais facilidade as suas ideias e vivências, foram recolhidos desenhos de 129 alunos sobre o seu maior medo. Os desenhos mostraram que os alunos representaram essencialme...

  1. CICLO ECONÓMICO Y MORA LEGAL EN EL SISTEMA FINANCIERO COSTARRICENSE

    OpenAIRE

    Chacón, Marlon Yong; Soto Jiménez, Max Alberto

    2013-01-01

    Este artículo analiza el comportamiento de la mora del sistema financiero costarricense durante el periodo 1999-2010, en particular, de los bancos estatales y privados en el periodo reciente de la crisis económica internacional. Para hacerlo, se utilizan modelos económicos para investigar las relaciones de causalidad entre la mora, el ciclo económico real y el financiero. Se concluye que la calidad de la cartera de crédito del sector financiero de Costa Rica se relaciona con el nivel de activ...

  2. Projecto Rodentia : etologia aplicada na sala de aula do 1º Ciclo

    OpenAIRE

    Franco, N. H.; Olosson, A.; J.B. Santos; Brosseron, F.; Pinto, A.; Ricardo, E.

    2008-01-01

    p. 275-279 O Projecto Rodentia, implementado no ano 2006/2007, visa promover a cultura científica em alunos do 1º ciclo do Ensino Básico, familiarizando-os com o Método Científico e desenvolvendo competências conceptuais, processuais e atitudinais, com base na Etologia Aplicada e na reflexão ética sobre o bem-estar animal. Foram instalados em três salas de aula habitats especialmente desenhados, contendo cada um dois ratos de laboratório. Inicialmente orien...

  3. Ciclos en la economía peruana y exigencias de política

    OpenAIRE

    Javier Iguíñiz Echeverría

    1986-01-01

    Estudiar una economía a partir de sus ciclos económicos implica una cierta confianza en la simultaneidad fundamental de las variaciones de los diversos componentes de esa economía. En otros términos, se supone un tipo de integración de la economía nacional que liga a sus partes de manera indisoluble aunque flexible. La experiencia peruana sugiere la necesidad de tener cierta cautela en tomo a la pertinencia de análisis muy agregados, sobre todo cuando se van a tener en cuenta las implicancias...

  4. La teoría del consumo y de los ciclos en Thorstein Veblen

    OpenAIRE

    Hernán Alejandro Morero; Alberto José Figueras

    2013-01-01

    Thorstein Veblen (1857-1929) fue uno de los fundadores de la economía institucional norteamericana. Este artículo presenta su teoría del consumo basada en los hábitos expuesta en la Teoría de la clase ociosa, y su teoría de los ciclos económicos y las crisis expuesta en la Teoría de la empresa de negocios. Para situarlas en contexto se esboza una síntesis de su pensamiento y de sus críticas a la economía ortodoxa.

  5. Revisión teórica del modelo de ciclo de vida organizacional

    OpenAIRE

    Laura Angélica Décaro Santiago; Juana Gabriela Soriano Hernández

    2014-01-01

    Los Modelos de Ciclo de Vida Organizacional (OLC, por sus siglas en inglés) tienen por objetivo representar el nivel de desarrollo de la empresa a través de una serie de etapas consecutivas; diferenciadas por características propias y retos por resolver. Los autores que se han dedicado al estudio del tema consideran que un buen entendimiento sobre el nivel de desarrollo de la empresa, permite tener un visión más amplia de las características y necesidades de la misma para con ello, auxilia...

  6. A dislexia no Terceiro Ciclo: perspetiva dos principais intervenientes no contexto escolar

    OpenAIRE

    Ferreira, Martinha Vieira

    2012-01-01

    Atualmente, os professores deparam-se com a necessidade de trabalhar com turmas muito heterogéneas, nas quais estão incluídos alunos com dislexia que exigem uma atenção redobrada devido às necessidades individuais de aprendizagem. A dislexia é uma deficiência com uma incidência importante, estimando-se que de 10 a 15% dos jovens apresentam esta problemática, sendo que cerca de metade desta percentagem chega ao terceiro ciclo sem saber que as suas dificuldades de aprendizagem têm origem na ...

  7. Mapas concetuais sobre a digestão (2.º Ciclo do Ensino Básico)

    OpenAIRE

    Belindro, Joana Cristina Rocha

    2013-01-01

    Dissertação de mest., Ensino do 1.º e 2.º ciclos do Ensino Básico, Escola Superior de Educação e Comunicação, Univ. do Algarve, 2013 O presente relatório foi elaborado como parte integrante da Prática de Ensino Supervisionada do Mestrado em Ensino do 1.º e 2.º CEB, com o objetivo de refletir e avaliar o meu percurso formativo e profissional, bem como as situações de aprendizagem, desafios, processos e desempenhos do quotidiano profissional experienciado. A capacidade de tira...

  8. Estudio comparativo del autoconcepto físico a lo largo del ciclo vital

    OpenAIRE

    David Molero; Mar\\u00EDa Luisa Zagalaz-S\\u00E1nchez; Javier Cach\\u00F3n-Zagalaz

    2013-01-01

    El propósito de esta investigación ha sido estudiar el autoconcepto físico y sus componentes a lo largo del ciclo vital, conocer si las valoraciones de cada una de las escalas están correlacionadas entre sí y comprobar la existencia de diferencias significativas a nivel estadístico en los resultados obtenidos en función de la edad y el sexo de los encuestados. La muestra está compuesta por 152 participantes distribuidos en tres grupos de edad (adolescentes, adultos y personas mayores de 50 añ...

  9. Necessidades e preocupações dos pais em diferentes etapas do ciclo vital

    OpenAIRE

    Bárbara Tarouco da Silva; Mara Regina Santos da Silva

    2014-01-01

    Objetivo: identificar as necessidades e as preocupações prioritárias, manifestadas pelos pais no desempenho do seu papel, em três etapas do ciclo vital: adolescência, idade produtiva e idade madura. Metodologia: estudo exploratório com abordagem qualitativa, desenvolvido com quatorze pais residentes em um município no extremo sul do Brasil. Os dados foram coletados entre maio e agosto de 2011, por meio de entrevista em profundidade. Através da técnica da análise textual discursiva e da matr...

  10. Un ciclo cerrado: el patrimonio nobiliario construido en la ciudad de Murcia

    OpenAIRE

    Calvo García-Tornel, Francisco

    2011-01-01

    La presencia en el tejido urbano de la ciudad de Murcia de las viviendas o palacios de la nobleza, está directamente relacionado con la evolución patrimonial de este grupo social. Cerrado el ciclo en el que el poder social nobiliario fue decisivo en la vida regional, su memoria se conserva básicamente a través de sus casas-palacio, un patrimonio histórico y, en buena medida, también artístico que ha sufrido una suerte muy desigual hasta el presente.

  11. Máquina de refrigeración de ciclo en cascada con un solo compresor

    OpenAIRE

    Martínez Mur, Cristina; Simón León, Javier

    2010-01-01

    El objetivo del presente documento ha sido obtener una nueva tecnología para un ciclo termodinámico de obtención de frío, del tipo refrigeración en cascada con un solo compresor, que puede alcanzar un amplio rango de temperaturas frías. La particularidad reside en que la tecnología utilizada permite obtener el frío de una manera más eficiente que las que ahora se utilizan, logrando un ahorro en el consumo. Se ha centrado el proyecto en una industria de alimentos congelados, con...

  12. Trastornos del ciclo de la metilación en pacientes con fenilcetonuria

    OpenAIRE

    López Suárez, Olalla Elena

    2016-01-01

    En este trabajo demostramos que los pacientes con fenilcetonuria (PKU) que siguen un tratamiento dietético estricto, con escasos aportes de proteínas naturales y alto aporte de suplementos dietéticos exentos de fenilalanina y enriquecidos en vitaminas y minerales, reciben una cantidad excesiva de vitamina B12 y de ácido fólico que conlleva una alteración en el ciclo de la metilación. Así, se produce un aumento de la vía de la remetilación, que se pone de manifiesto en el des...

  13. Incidencia de los Movimientos Oculares en el proceso lector de alumnos de Primer ciclo de Primaria.

    OpenAIRE

    Alejo-Ramos, Cristina

    2013-01-01

    Los movimientos oculares en la lectura son importantes para el proceso de aprendizaje de los niños. Este trabajo de investigación tiene como objetivo, conocer la influencia de los movimientos oculares en la lectura. Para ello se llevó a cabo un estudio, con una muestra de 30 alumnos del Primer ciclo de Primaria, es decir, Primero y Segundo, del mismo centro educativo. Una vez que se realizaron las pruebas oportunas, se pudo comprobar cómo estaban relacionadas motricidad ocular y lectura...

  14. Realização de uma cantata em contexto de 2º ciclo

    OpenAIRE

    Anjo, Vítor Marcelo Nunes Martins

    2015-01-01

    Este projeto centra-se na realização de uma cantata original, composta pelo presente autor denominada “À procura das Índias”, cantada e tocada pelas crianças com uma orquestra de guitarras e cavaquinhos e contando também com a participação de músicos profissionais no piano e bateria. O projeto educativo desenvolveu-se no colégio Guadalupe, situado no Seixal, e foi realizado numa turma de 2º ciclo, 5º ano de escolaridade, onde foi possível desenvolver, ao longo de treze sessõ...

  15. estudo exploratório com estudantes do 1º ciclo do ensino superior

    OpenAIRE

    Rodrigues, Maria do Rosário Queirós

    2012-01-01

    Dissertação apresentada à Universidade Fernando Pessoa, como parte dos requisitos para a obtenção do grau de Mestre em Psicologia, especialização em Psicologia do Trabalho e das Organizações Este trabalho apresenta um estudo exploratório sobre as atividades de aprendizagem e as perceções de literacia no ensino superior, tendo sido concretizado com estudantes universitários do 1º ciclo de estudos (Licenciatura) em três instituições de ensino superior, públicas e privadas, do norte do país. ...

  16. Estudio de proteínas reguladoras del ciclo celular en psoriasis mediante matrices tisulares

    OpenAIRE

    Roncero Riesco, Mónica

    2013-01-01

    [ES] Antecedentes. La psoriasis es una enfermedad inflamatoria crónica caracterizada histológicamente por la hiperproliferación y la diferenciación anómala de los queratinocitos epidérmicos. Los queratinocitos sufren alteraciones en la regulación del ciclo celular que pueden ser demostrables mediante el estudio de expresión de sus proteínas reguladoras. Los patrones de expresión de estas proteínas podrían ser empleados como herramienta diagnóstica en casos donde la clínica, la histopa...

  17. Genotoxicidade de Mercurio em Pisum sativum: ciclo celular e dano no ADN

    OpenAIRE

    Silva, Raquel Azevedo da

    2011-01-01

    O Mercúrio (Hg) é um contaminante ubíquo no meio ambiente e que causa mutagenese e clastogenese em animais. É sabido que este metal tem efeitos prejudiciais para as plantas mas esse efeito está pouco estudado, sendo portanto urgente o estudo e avaliação do efeito deste metal ao nível do ADN. Com o intuito de determinar se a exposição in vivo de mercúrio pode induzir efeitos genotoxicos, foram avaliados os seguintes parâmetros: nível de ploidia, progressão do ciclo celular e danos no ADN. Para...

  18. Efecto in vitro de olomoucina en el ciclo celular de linfocitos humanos

    OpenAIRE

    Camargo M.; López C.

    2001-01-01

    La olomoucina, un derivado de purina relacionado con el ATP, ha sido reportado como uneficiente inhibidor del ciclo celular de células animales y vegetales, debido a su alta especificidadpor las ciclinas dependientes de kinasa (CDK) CDK1 y CDK2, su capacidad radica en inhibir elciclo celular en las transiciones G2/M y G1/S respectivamente. Con el objetivo de explorar lapotencial aplicación de la olomoucina en el análisis citogenético de alta resolución y estudiosde proliferación celular en cu...

  19. Las relaciones de amor a lo largo del ciclo vital: cambios generacionales

    OpenAIRE

    Calatayud Arenes, Mari Paz

    2009-01-01

    RESUMEN La investigación que sustenta esta Tesis Doctoral parte de una concepción del Desarrollo Humano propia de la Psicología Evolutiva del Ciclo Vital, y se apoya sobre tres pilares: las vinculaciones afectivas (como inicio de los estudios científicos del amor), las relaciones de amor (especialmente, las aportaciones de Robert J. Sternberg: la Teoría Triangular del Amor, y la concepción del Amor como una Historia), y la memoria autobiográfica (es decir, la capacidad de almacenar y recup...

  20. Ecodiseño de alimentos mediante análisis de ciclo de vida

    OpenAIRE

    Ramos Fernández, Saioa

    2015-01-01

    246 p. La creciente demanda de producción de alimentos debida al aumento de la población mundial, ejerce una gran presión sobre los ecosistemas y el medio ambiente del planeta. Los alimentos, a lo largo de su ciclo de vida utilizan una gran cantidad de recursos (suelo, agua, energía y materiales) y emiten muchas sustancias al medio (CO2, pesticidas, etc.) que tienen un impacto directo en el medio ambiente. Con el fin de evaluar el impacto ambiental asociado a la producción comercialización...

  1. Estudio de la motivación en los ciclos formativos de administración

    OpenAIRE

    Ollo Uhalte, Mikel

    2014-01-01

    La falta de motivación no es un problema que sólo afecte a alumnos de educación obligatoria. Afecta, de la misma manera, a los estudiantes de estudios postobligatorios, como en nuestro caso particular son los distintos ciclos formativos de administración. Muchos son los factores posibles que pueden influir en el grado de motivación de un alumno y la mayoría de ellos distintos entre sí. Sin embargo, pocas son las consecuencias académicas que puede originar la falta de motivación y, entre e...

  2. ¿Cómo enseñar a dividir? Secuencia de actividades para Ciclo 2

    OpenAIRE

    Zambrano, Jennyfer Alejandra; Gónzalez, Jenny

    2011-01-01

    Esta es una experiencia de aula llevada a cabo en el ciclo 2, la cual estuvo a cargo de dos profesoras practicantes quienes promovieron la estructura multiplicativa hasta identificar los múltiplos y divisores de un número, dicha experiencia se rigió desde lo metodológico por la estructura propuesta por el grupo DECA (); a nivel conceptual por varios autores como Verganud, Maza (1991),y otros; y finalmente el marco legal por los Estándares Básicos (2007) y los Lineamientos (1998. Se realizaron...

  3. El estudio de las rocas y minerales en el ciclo medio de la EGB

    Directory of Open Access Journals (Sweden)

    Juan GONZÁLEZ CRESPO

    2009-11-01

    Full Text Available El estudio de las rocas y minerales ha sido generalmente escaso en estos niveles de EGB. La mayoría de las veces se limita a conceptos teóricos elementales y en no pocas ocasiones a contenidos ajenos a la experiencia del alumnado. Quizá esto se deba a la indudable complejidad en algunos aspectos de estas materias, dificultad terminológica que presenta en no pocas ocasiones, escasez de recursos en los centros ... Todo lo cual ha llevado a que estas materias se consideren más propias de niveles superiores y, por tanto, algo ajeno para los alumnos de este ciclo.

  4. Impacto de un programa intervención em alunos del segundo ciclo

    OpenAIRE

    Melo, Marta; Pereira, M. Graça; Silvério, Jorge Manuel Amaral

    2014-01-01

    O objetivo do presente estudo consistiuem avaliar um programa de intervenção junto a alunos do 2º ciclo de escolaridade nas seguintes dimensões: tomada de decisão, conhecimentos sobre sexualidade, competências sociais, assertividade e autoconceito. Metodologia: Participaram 145 alunos, distribuídos pelos grupos controle e experimental. Os instrumentos utilizados foram: TCU Decision-Making; Questionário de Conhecimentos sobre Sexualidade; Assertion Self-Statement Test- Revised; Questionário de...

  5. O jogo no 2º ciclo do ensino básico

    OpenAIRE

    Lopes, Ana Catarina Moreira

    2012-01-01

    Mestrado em Ensino do 1º E 2º Ciclos do Ensino Básico Este trabalho traz uma ampla visão da importância dos jogos no processo ensino-aprendizagem e na formação da personalidade da criança. A devida valorização desta temática cabe ao professor, que se torna responsável pela aprendizagem e, por isso, deve promover um crescimento integral para a criança, nomeadamente os aspetos biológicos, cognitivos, sociais e afetivos. No jogo, o professor encontra um forte aliado para a supe...

  6. Los ciclos económicos departamentales en Colombia, 1960-2011

    OpenAIRE

    Fredy Vásquez Bedoya; Sergio Iván Restrepo Ochoa; Mauricio Lopera Castaño; María Isabel Restrepo Estrada

    2014-01-01

    En este trabajo se estima el ciclo del PIB nacional y de algunos departamentos entre 1960 y 2011 usando el modelo de tendencia lineal local de Nelson y Plosser, así como el coeficiente de correlación entre el componente cíclico de las series del PIB departamental y nacional para clasificar sus co-movimientos. El estudio revela una diversidad de comportamientos de las fluctuaciones económicas departamentales con respecto a la nacional y, además, que las economías departamentales fuertemente pr...

  7. La impulsividad en el primer ciclo de educación infantil

    OpenAIRE

    González, María Soledad

    2011-01-01

    Este trabajo trata sobre las relaciones sociales en el primer ciclo de Educación Infantil, centrándonos en las conductas impulsivas, las causas que las provocan y la forma de evitarlas. Tiene como finalidad mejorar las relaciones sociales en el aula, evitando y modificando las conductas impulsivas desde las edades más tempranas, ya que es en esta etapa cuando los niños y niñas están formando su personalidad. Por ello, es muy importante ayudar a los pequeños a modificar el comportamiento...

  8. State space model extraction of thermohydraulic systems Part II: a linear graph approach applied to a Brayton cycle–based power conversion unit

    OpenAIRE

    Uren, Kenneth Richard; Schoor, George van

    2013-01-01

    This second paper in a two part series presents the application of a developed state space model extraction methodology applied to a Brayton cycle-based PCU (power conversion unit) of a PBMR (pebble bed modular reactor). The goal is to investigate if the state space extraction methodology can cope with larger and more complex thermohydraulic systems. In Part I the state space model extraction methodology for the purpose of control was described in detail and a state space represen...

  9. Investigation on the performance of the supercritical Brayton cycle with CO2-based binary mixture as working fluid for an energy transportation system of a nuclear reactor

    International Nuclear Information System (INIS)

    In this study, the performance of a SBC (supercritical gas Brayton cycle) using CO2-based binary mixtures as the working fluids have been studied. Based on the thermodynamic analyses, an in-house code has been developed to determine the cycle efficiency and the amounts of heat transfer in the HTR (high temperature recuperator) and the LTR (low temperature recuperator) with different CO2/additive gas ratios. Several gases are selected as potential additives, including O2, He, Ar, Kr, butane and cyclohexane. Compared with the Brayton cycle with pure S–CO2 (supercritical carbon dioxide) as the working fluid, it is found that both CO2–He and CO2–Kr mixtures can improve the thermodynamic performances of the SBC by increasing the cycle efficiency and decreasing the amounts of heat transfer in the HTR and LTR. For the cycles with the pure S–CO2 mixture, CO2–butane mixture and CO2–cyclohexane mixture as the working fluids, the cycle efficiencies decrease with increasing main compressor inlet temperature. However, when the main compressor inlet temperature is above the critical temperature of pure CO2, the cycle efficiencies of the cycles with CO2–butane mixture and CO2–cyclohexane mixture are higher than that of the cycle with pure CO2 as the working fluid. For the cycles with CO2-based binary mixtures and pure S–CO2 as the working fluids, the higher reactor outlet temperature always results into higher cycle efficiencies and larger amount of heat transfer in the HTR and smaller amount of heat transfer in the LTR. - Highlights: • The Brayton cycle performance with different mixtures as working fluids is studied. • Thermodynamic analysis is carried out to evaluate cycle efficiency and heat transfer in HTR and LTR. • The optimum working parameters of the Brayton cycle is proposed to improve working performance

  10. Development of cooling system for 66/6.9kV-20MVA REBCO superconducting transformers with Ne turbo-Brayton refrigerator and subcooled liquid nitrogen

    Science.gov (United States)

    Iwakuma, M.; Adachi, K.; Yun, K.; Yoshida, K.; Sato, S.; Suzuki, Y.; Umeno, T.; Konno, M.; Hayashi, H.; Eguchi, T.; Izumi, T.; Shiohara, Y.

    2015-12-01

    We developed a turbo-Brayton refrigerator with Ne gas as a working fluid for a 3 ϕ- 66/6.9kV-2MVA superconducting transformer with coated conductors which was bath-cooled with subcooled LN2. The two-stage compressor and expansion turbine had non-contact magnetic bearings for a long maintenance interval. In the future, we intend to directly install a heat exchanger into the Glass-Fiber-Reinforced-Plastics cryostat of a transformer and make a heat exchange between the working fluid gas and subcooled LN2. In this paper we investigate the behaviour of subcooled LN2 in a test cryostat, in which heater coils were arranged side by side with a flat plate finned-tube heat exchanger. Here a He turbo-Brayton refrigerator was used as a substitute for a Ne turbo-Brayton one. The pressure at the surface of LN2 in the cryostat was one atmosphere. Just under the LN2 surface, a stationary layer of LN2 was created over the depth of 20 cm and temperature dropped from 77 K to 65 K with depth while, in the lower level than that, a natural convection flow of LN2 was formed and temperature was almost uniform over 1 m depth. The boundary plane between the stationary layer and the natural convection region was visible.

  11. Transient Accident Analysis of a Supercritical Carbon Dioxide Brayton Cycle Energy Converter Coupled to an Autonomous Lead-Cooled Fast Reactor

    International Nuclear Information System (INIS)

    The Supercritical Carbon Dioxide (S-CO2) Brayton Cycle is a promising advanced alternative to the Rankine saturated steam cycle and recuperated gas Brayton cycle for the energy converters of specific reactor concepts belonging to the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. A new plant dynamics analysis computer code has been developed for simulation of the S-CO2 Brayton cycle coupled to an autonomous, natural circulation Lead-Cooled Fast Reactor (LFR). The plant dynamics code was used to simulate the whole-plant response to accident conditions. The specific design features of the reactor concept influencing passive safety are discussed and accident scenarios are identified for analysis. Results of calculations of the whole-plant response to loss-of-heat sink, loss-of-load, and pipe break accidents are demonstrated. The passive safety performance of the reactor concept is confirmed by the results of the plant dynamics code calculations for the selected accident scenarios. (authors)

  12. Detailed analysis of the effect of the turbine and compressor isentropic efficiency on the thermal and exergy efficiency of a Brayton cycle

    Directory of Open Access Journals (Sweden)

    Živić Marija

    2014-01-01

    Full Text Available Energy and exergy analysis of a Brayton cycle with an ideal gas is given. The irreversibility of the adiabatic processes in turbine and compressor is taken into account through their isentropic efficiencies. The net work per cycle, the thermal efficiency and the two exergy efficiencies are expressed as functions of the four dimensionless variables: the isentropic efficiencies of turbine and compressor, the pressure ratio, and the temperature ratio. It is shown that the maximal values of the net work per cycle, the thermal and the exergy efficiency are achieved when the isentropic efficiencies and temperature ratio are as high as possible, while the different values of pressure ratio that maximize the net work per cycle, the thermal and the exergy efficiencies exist. These pressure ratios increase with the increase of the temperature ratio and the isentropic efficiency of compressor and turbine. The increase of the turbine isentropic efficiency has a greater impact on the increase of the net work per cycle and the thermal efficiency of a Brayton cycle than the same increase of compressor isentropic efficiency. Finally, two goal functions are proposed for thermodynamic optimization of a Brayton cycle for given values of the temperature ratio and the compressor and turbine isentropic efficiencies. The first maximizes the sum of the net work per cycle and thermal efficiency while the second the net work per cycle and exergy efficiency. In both cases the optimal pressure ratio is closer to the pressure ratio that maximizes the net work per cycle.

  13. TALLER DE CUENTOS PARA TRABAJAR HABILIDADES SOCIALES RELACIONADAS CON LOS SENTIMIENTOS EN EL PRIMER CICLO DE EDUCACION INFANTIL.

    OpenAIRE

    Andrada-Bastit, Auxiliadora

    2014-01-01

    El planteamiento de esta propuesta educativa responde a una inquietud por acercar desde un planteamiento práctico, el mundo de las habilidades sociales a los niños del primer ciclo de educación infantil. Después de constatar entre profesionales del segundo ciclo una cierta carencia en sus aulas de este tipo de conductas, se plantea la posibilidad de diseñar un taller con el que fomentar la adquisición de ciertas estrategias que ayuden a los niños a comprender mejor las emociones y mejorar su ...

  14. Ciclo de vida y conducta de adultos de cinco especies de Phyllophaga Harris, 1827 (Coleoptera: Melolonthidae; Melolonthinae)

    OpenAIRE

    Agustín Aragón García; Miguel Ángel Morón; Jesús Francisco López Olguín; Luis Manuel Cervantes Peredo

    2005-01-01

    Se describe el ciclo de vida de Phyllophaga ravida (Blanchard), P. macrocera Bates, P. vetula (Horn), P.ilhuicaminai Morón, y P. obsoleta (Blanchard), en condiciones de laboratorio, a partir de adultos en cópula obtenidos en localidades del estado de Puebla, México. Las larvas se mantuvieron en un cuarto de cría a temperatura de 26 ± 2 oC y humedad relativa de 70 ± 5%, dentro de recipientes con suelo y se alimentaron con rodajas de zanahoria. El ciclo de vida para las cinco especies es anual;...

  15. Implicaciones del estudio de inestabilidad del ciclo celular en la biología del cáncer.

    OpenAIRE

    Luis Tume-Farfán

    2014-01-01

    Todas las células poseen mecanismos para mantener la integridad genómica que es vital para la supervivencia celular y la proliferación. Las células se dividen a tasas normale s durante su tiempo de vida, cuando esta tasa sobrepasa los límites normales ocurren alteraciones a nivel genético que afectan el control del ciclo celular por lo tanto estas células crecen y se dividen sin control y ya no responden a señalización extrace lular que indica la detención del ciclo y la apoptosis, estos meca...

  16. Modelo estocástico para planificar cadenas de suministro con productos de ciclos de vida cortos

    Directory of Open Access Journals (Sweden)

    Jairo Coronado-Hernandez

    2010-07-01

    Full Text Available En este trabajo se presenta un modelo de optimización estocástica para la planificación de cadenas de suministros para productos con ciclo de vida corto, a través de la decisión de reservar la capacidad a contratar en los recursos de los proveedores antes de tener certeza del comportamiento de la demanda. Se consideran recursos alternativos, múltiples productos con lista de materiales complejas, demanda distribuida a lo largo de periodos consecutivos, ciclos de vida cortos, lead time largos y altos niveles de incertidumbre representados en forma de escenarios.

  17. Análisis del Comportamiento de un Ciclo Tipo Carnot Analysis of the Behavior of a Carnot Type Cycle

    OpenAIRE

    Delfino Ladino-Luna

    2010-01-01

    Se hace un análisis de las regiones de existencia de la función potencia de salida y función ecológica, que dan lugar a la forma de las respectivas eficiencias para un ciclo tipo Carnot, llamado ciclo endorreversible, a potencia de salida máxima y función ecológica máxima. Se muestra la importancia dichas regiones de existencia de estas funciones para diversos resultados de la literatura relacionada con la termodinámica de tiempos finitos. Se concluye que para modelar gráficamente el desempeñ...

  18. Modelo estocástico para planificar cadenas de suministro con productos de ciclos de vida cortos

    OpenAIRE

    Jairo Coronado-Hernandez; Jose P. Garcia-Sabater

    2010-01-01

    En este trabajo se presenta un modelo de optimización estocástica para la planificación de cadenas de suministros para productos con ciclo de vida corto, a través de la decisión de reservar la capacidad a contratar en los recursos de los proveedores antes de tener certeza del comportamiento de la demanda. Se consideran recursos alternativos, múltiples productos con lista de materiales complejas, demanda distribuida a lo largo de periodos consecutivos, ciclos de vida cortos, lead time largos y...

  19. Niveles plasmáticos de beta-endorfina en el ciclo menstrual y en la dismenorrea

    OpenAIRE

    Martínez-Guisasola Campa, Francisco Javier

    1993-01-01

    Se realiza la valoración de las concentraciones plasmáticas de beta-endorfina en el ciclo menstrual y en la mujer dismenorreica, para lo que se estudian un grupo de jóvenes fértiles, todas ellas voluntarias, no estando ninguna sometida a tratamiento hormonal ni a anticoncepción. La sangre obtenida en días concretos del ciclo por punción venosa es analizada por RIA para obtener las concentraciones del opiáceo, determinándose las gonadotropinas y los esteroides ováricos por ELISA. La beta-endor...

  20. Estudio técnico-económico de una central híbrida solar-ciclo combinado (ISCC)

    OpenAIRE

    Hidalgo Cebrián, Lucía

    2012-01-01

    El objetivo de este proyecto es estudiar la viabilidad de una central híbrida solar-ciclo combinado (ISCC) en Argelia. La planta consiste en un ciclo combinado basado en dos turbinas de gas de 42 MW cada una y una turbina de vapor de 60 MW de los cuales 20 MW se deben al campo solar, siendo la potencia eléctrica de la planta 144 MW. El campo solar se ha dimensionado para obtener una contribución solar del 5% sobre la producción eléctrica anual de la instalación. La tecnología solar utilizada ...

  1. ¿Están sincronizados los ciclos económicos en Latinoamérica?

    OpenAIRE

    Juliana Ávila Vélez; Álvaro José Pinzón Giraldo

    2015-01-01

    Se identifican los ciclos económicos de Brasil, Chile, Colombia, Ecuador, México, Perú y Venezuela, utilizando el criterio del CEPR y el algoritmo Bry-Boschan (1971), aplicado al Producto Interno Bruto (PIB) y al Índice de Producción Industrial (IPI), respectivamente. Se mide el grado de sincronización del ciclo de dichas economías por medio del indicador de Harding y Pagan (2006) y de las correlaciones cruzadas de los componentes transitorios de las variables. El periodo muestral inicia en 1...

  2. CICLO DE VIDA ORGANIZACIONAL E CONTROLE GERENCIAL: UMA ANÁLISE DOS ARTIGOS EM PERIÓDICOS INTERNACIONAIS DE CONTABILIDADE

    OpenAIRE

    Paulo Roberto da Cunha; Roberto Carlos Klann; Carlos Eduardo Facin Lavarda

    2013-01-01

    O objetivo deste estudo é analisar os artigos sobre a abordagem do ciclo de vida organizacional em nível internacional, levantando os principais tópicos associados com os controles gerenciais. Em pesquisa a 67 periódicos, chegou-se a uma amostra inicial de 39 artigos. Após a leitura dos resumos para identificação dos artigos que relacionassem ciclo de vida organizacional com controles gerenciais, a amostra ficou em sete artigos. O periódico internacional de contabilidade que mais publicou art...

  3. SEGUIMIENTO DEL CICLO DE VIDA DE WOODSIA MOLLIS (KAULF.) J. SM. (ATHYRIACEAE-PTERIDOPHYTA) EN TRES SUSTRATOS NATURALES

    OpenAIRE

    Janet Vivero-Barón; María de la Luz Arreguín-Sánchez; David Leonor Quiroz-García; Rafael Fernández-Nava; Salvador Acosta-Castellanos

    2012-01-01

    Se describe el ciclo de vida de Woodsia mollis (Kaulf.) J. Sm. Los especímenes fueron colectados en un bosque mesófi lo de montaña al Sur de Coajomulco, Municipio de Huitzilac, Estado de Morelos, México. Las esporas fueron sembradas en frascos de vidrio en tres medios de cultivo (tierra de hoja, maquique y musgo). El ciclo fue isospórico con desarrollo del protalo tipo Drynaria. En la fase cordada se apreciaron gametofi tos cordados y cordados-circulares, los anteridios se formaron a los 99 d...

  4. Morfogénesis cortical y ciclo celular en "histriculus y gastróstyla" (ciliados hipótrico)

    OpenAIRE

    Nieto Gutiérrez, Joaquín José

    1980-01-01

    La norma morfogenética cortical de división en H. similisy H. muscorum es similar a la descrita para otros oxytriquidos aunque difieren en el origen del cirro bucal del protero y en el numero de primordios de la ciliación dorsal. La morfogénesis de regeneración subsiguiente al tratamiento con urea en estas dos especies y en G. steinii presenta algunas diferencias con respecto a la morfogénesis de división no totalmente explicables por la hipótesis de la coexistencia de los gradientes de ac...

  5. Crescimento de raízes de cana crua e queimada em dois ciclos

    Directory of Open Access Journals (Sweden)

    Alvarez Ivan André

    2000-01-01

    Full Text Available Este trabalho teve como objetivos comparar o crescimento de raízes de cana colhida crua, mecanizada e de cana após a queima, colhida manualmente; avaliar a influência do clima sobre as duas condições de crescimento e analisar o comportamento do crescimento de raízes de cana crua e cana queimada nos 1º e 2º anos de rebrota, através de curvas adaptadas. A pesquisa foi realizada no município de Morro Agudo, SP, de julho de 1995 a julho de 1997. A cultivar utilizada foi a SP 70-1143. Utilizou-se como indicadores de crescimento das raízes a matéria seca e o perfil delas no solo. Avaliou-se a influência das temperaturas e das umidades do ar e do solo sobre os tratamentos. Observou-se que o crescimento, no primeiro e no segundo ciclo, não apresentou curvas que indicassem um padrão semelhante, tanto para cana crua, como para cana queimada, os fatores climatológicos, isoladamente, não provocaram mudanças nos ciclos de crescimento de maneira que se identificasse uma tendência geral. As raízes aparecem em maior quantidade em todas camadas do solo em cana crua do que em cana queimada, no primeiro ano e no segundo ano aparecem maiores em cana queimada.

  6. Família e ciclo vital: a fase de aquisição

    Directory of Open Access Journals (Sweden)

    Juliana Peterle Ronchi

    2011-08-01

    Full Text Available Esta pesquisa objetivou descrever as características da fase deaquisição, primeira fase do ciclo vital familiar, marcada pela uniãodo casal e a convivência com os filhos pequenos. O estudo foirealizado com 50 famílias de classe média, na fase de aquisição dociclo vital da família, da cidade de Vitória-ES. Os participantesresponderam ao questionário baseado na pesquisa Ciclo vital dafamília paulista, que se mostrou adequado para compreender adinâmica e os valores das famílias da cidade de Vitória. Os dadoscoletados foram submetidos ao programa SPSS para Windows e,em seguida, realizamos análise qualitativa dos dados. Em Vitória,a família em fase de aquisição se mostrou mais tradicional, comconflitos relacionados a assuntos de extradinâmica familiar, comodinheiro e satisfação profissional.

  7. Quase adulta, quase velha: por que antecipar as fases do ciclo vital?

    Directory of Open Access Journals (Sweden)

    Russel Parry Scott

    2001-02-01

    Full Text Available A partir de duas observações em gerações diferentes, identifica-se um fenômeno de antecipação da passagem pelas fases do ciclo vital que merece uma interpretação. Muitas jovens engravidam, casando ou não, e se tornam mães. Muitas mulheres na faixa de quarenta e cinco a cinqüenta anos ingressam em "grupos de idosos". A interpretação oferecida examina as conseqüências 1 da transição demográfica (e decorrente envelhecimento populacional em dar visibilidade especial a estas gerações examinadas, 2 do mercado de trabalho que é excludente, 3 da atuação do Estado, 4 do individualismo crescente e 5 da lógica das relações de geração e gênero em grupos domésticos. Para explicar as ações das quase adultas e das quase velhas que antecipam as fases do ciclo vital, recorre-se à conjunção destes fatores que culmina numa criação de uma condição de liminaridade geracional, própria dos ritos de passagem, e na construção de processos de desritualização e re-ritualização da sociedade contemporânea.

  8. Investigation of alternative layouts for the supercritical carbon dioxide Brayton cycle for a sodium-cooled fast reactor

    International Nuclear Information System (INIS)

    Analyses of supercritical carbon dioxide (S-CO2) Brayton cycle performance have largely settled on the recompression supercritical cycle (or Feher cycle) incorporating a flow split between the main compressor downstream of heat rejection, a recompressing compressor providing direct compression without heat rejection, and high and low temperature recuperators to raise the effectiveness of recuperation and the cycle efficiency. Alternative cycle layouts have been previously examined by Angelino (Politecnico, Milan), by MIT (Dostal, Hejzlar, and Driscoll), and possibly others but not for sodium-cooled fast reactors (SFRs) operating at relatively low core outlet temperature. Thus, the present authors could not be sure that the recompression cycle is an optimal arrangement for application to the SFR. To ensure that an advantageous alternative layout has not been overlooked, several alternative cycle layouts have been investigated for a S-CO2 Brayton cycle coupled to the Advanced Burner Test Reactor (ABTR) SFR preconceptual design having a 510 deg. C core outlet temperature and a 470 deg. C turbine inlet temperature to determine if they provide any benefit in cycle performance (e.g., enhanced cycle efficiency). No such benefits were identified, consistent with the previous examinations, such that attention was devoted to optimizing the recompression supercritical cycle. The effects of optimizing the cycle minimum temperature and pressure are investigated including minimum temperatures and/or pressures below the critical values. It is found that improvements in the cycle efficiency of 1% or greater relative to previous analyses which arbitrarily fixed the minimum temperature and pressure can be realized through an optimal choice of the combination of the minimum cycle temperature and pressure (e.g., for a fixed minimum temperature there is an optimal minimum pressure). However, this leads to a requirement for a larger cooler for heat rejection which may impact the

  9. Alteraciones del ciclo circadiano en las enfermedades psiquiátricas: papel sincronizador de la melatonina en el ciclo sueño-vigilia y la polaridad neuronal

    Directory of Open Access Journals (Sweden)

    Graciela Jiménez-Rubio

    2011-01-01

    Full Text Available Los ritmos circadianos son patrones de oscilación con un periodo cercano a 24h que se observan en los procesos fisiológicos. En los mamíferos se han descrito funciones biológicas con regulación circádica tal como el ciclo sueño-vigilia. La administración de la melatonina, una indolamina secretada por la glándula pineal, sincroniza los ritmos circadianos. En los humanos, este efecto se ha estudiado en sujetos con síndrome de «fase de retraso de sueño», personas que sufren el síndrome de jet lag, en los trabajadores nocturnos y en los invidentes. La melatonina puede reducir los síntomas de jet lag y mejorar la calidad del sueño, además de acelerar la sincronización de la fase circadiana al tiempo local. Los niveles de la melatonina disminuyen con la edad y en las enfermedades neurodegenerativas y psiquiátricas. Los pacientes con enfermedad de Alzheimer muestran alteraciones del sueño como cambios en su ritmicidad y en su estructura. La administración de la melatonina a estos pacientes provoca mejoría en los síntomas de agitación que se presentan al atardecer. Los pacientes con trastorno bipolar manifiestan insomnio asociado con la fase de manía e hipersomnia durante la fase de depresión. Estas alteraciones en el sueño se relacionan con un desfasamiento del ritmo circadiano y/o arritmia. En pacientes con depresión y con esquizofrenia existe una disminución en los niveles plasmáticos de la melatonina en ambas fases del ciclo luz-oscuridad. La administración de melatonina incrementa la eficiencia del sueño en ellos. Además de las alteraciones en el sueño y en el ritmo de secreción de la melatonina observado en pacientes neuropsiquiátricos, existen cambios estructurales y funcionales en regiones específicas cerebrales que son producidas por la pérdida neuronal o por alteraciones de la polaridad y de la morfología neuronal, que son funciones reguladas por el citoesqueleto. A pesar de la información que existe

  10. Analysis of Superimposed Elementary Thermodynamic Cycles: from the Brayton-Joule to Advanced Mixed (Auto-Combined Cycles

    Directory of Open Access Journals (Sweden)

    Giovanni Manente

    2009-09-01

    Full Text Available

    The need for efficiency improvement in energy conversion systems leads to a stricter functional integration among system components. This results in structures of increasing complexity, the high performance of which are often difficult to be understood easily. To make the comprehension of these structures easier, a new approach is followed in this paper, consisting in their representation as partial or total superimposition of elementary thermodynamic cycles. Although system performance cannot, in general, be evaluated as the sum of the performance of the separate thermodynamic cycles, this kind of representation and analysis can be of great help in understanding directions of development followed in the literature for the construction of advanced energy systems, and could suggest new potential directions of work. The evolution from the simple Brayton-Joule cycle to the so called “mixed” cycles, in which heat at the turbine discharge is exploited using internal heat sinks only without using a separate bottoming section, is used to demonstrate the potentiality of the approach. Mixed cycles are named here "auto-combined cycles” to highlight the combination of different (gas and steam cycles within the same system components.

    • This paper is an updated version of a paper published in the ECOS'08 proceedings. 

  11. A preliminary assessment of reactor candidate technologies for a 20 kWe space nuclear Brayton system

    International Nuclear Information System (INIS)

    In 1983, a cooperative program between the French Centre National d'Etudes Spaciales (CNES) and the Commissariat a l'Energie Atomique (CEA) was initiated to investigate the possible development of 20 to 200 kWe Brayton nuclear space systems. After the completion of the preliminary design of a reference 200 kWe turboelectric power system known as ERATO in 1986 (Carre et al. 1987), a second 3-year study phase was initiated. The objective of this phase was to assess the various reactor candidate technologies and system design options for 20 kWe power level for meeting the projected electric needs of the first European space missions (Carre et al. 1988). This paper presents the results of the design studies of three reference design concepts of 20 kWe turboelectric power systems covering a wide range of reactor temperatures and relevant material and reactor design technologies. Additionally the critical technology issues of the candidate systems, and other criteria relevant to the space missions are identified. The participation of the French industry in the present design activity is so far restricted to predesign studies of crucial components such as the turbomachinery and the reactor control actuators, and integration studies of the power system into the Ariane V launcher

  12. Exergoeconomic performance optimization of an endoreversible intercooled regenerated Brayton cogeneration plant. Part 2: Heat conductance allocation and pressure ratio optimization

    Directory of Open Access Journals (Sweden)

    Bo Yang, Lingen Chen, Fengrui Sun

    2011-03-01

    Full Text Available Finite time exergoeconomic performance of an endoreversible intercooled regenerative Brayton cogeneration plant is optimized based on the model which is established using finite time thermodynamic in Part 1 of this paper. It is found that the optimal heat conductance allocation of the regenerator is zero. When the total pressure ratio and the heat conductance allocation of the regenerator are fixed, it is shown that there exist an optimal intercooling pressure ratio, and a group of optimal heat conductance allocations among the hot-, cold- and consumer-side heat exchangers and the intercooler, which correspond to a maximum dimensionless profit rate. When the total pressure ratio is variable, there exists an optimal total pressure ratio which corresponds to a double-maximum dimensionless profit rate, and the corresponding exergetic efficiency is obtained. The effects of the total heat exchanger conductance, price ratios and the consumer-side temperature on the double-maximum dimensionless profit rate and the corresponding exergetic efficiency are discussed. It is found that there exists an optimal consumer-side temperature which corresponds to a thrice-maximum dimensionless profit rate.

  13. Exergoeconomic performance optimization of an endoreversible intercooled regenerated Brayton cogeneration plant. Part 1: Thermodynamic model and parameter analyses

    Directory of Open Access Journals (Sweden)

    Lingen Chen, Bo Yang, Fengrui Sun

    2011-03-01

    Full Text Available A thermodynamic model of an endoreversible intercooled regenerative Brayton heat and power cogeneration plant coupled to constant-temperature heat reservoirs is established by using finite time thermodynamics in Part 1 of this paper. The heat resistance losses in the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator are taken into account. The finite time exergoeconomic performance of the cogeneration plant is investigated. The analytical formulae about dimensionless profit rate and exergetic efficiency are derived. The numerical examples show that there exists an optimal value of intercooling pressure ratio which leads to an optimal value of dimensionless profit rate for the fixed total pressure ratio. There also exists an optimal total pressure ratio which leads to a maximum profit rate for the variable total pressure ratio. The effects of intercooling, regeneration and the ratio of the hot-side heat reservoir temperature to environment temperature on dimensionless profit rate and the corresponding exergetic efficiency are analyzed. At last, it is found that there exists an optimal consumer-side temperature which leads to a double-maximum dimensionless profit rate. The profit rate of the model cycle is optimized by optimal allocation of the heat conductance of the heat exchangers in Part 2 of this paper.

  14. Design of automatic startup and shutdown logic for a Brayton-cycle 2- to 15-kilowatt engine

    Science.gov (United States)

    Vrancik, J. E.; Bainbridge, R. C.

    1975-01-01

    The NASA Lewis Research Center is conducting a closed-Brayton-cycle power conversion system technology program in which a complete power system (engine) has been designed and demonstrated. This report discusses the design of automatic startup and shutdown logic circuits as a modification to the control system presently used in this demonstration engine. This modification was primarily intended to make starting the engine as simple and safe as possible and to allow the engine to be run unattended. In the modified configuration the engine is started by turning the control console power on and pushing the start button after preheating the gas loop. No other operator action is required to effect a complete startup. Shutdown, if one is required, is also effected by a simple stop button. The automatic startup and shutdown of the engine have been successfully and purposefully demonstrated more than 50 times at the Lewis Research Center during 10,000 hours of unattended operation. The net effect of this modification is an engine that can be safely started and stopped by relatively untrained personnel. The approach lends itself directly to remote unattended operation.

  15. Reactor dynamics and stability analysis of a burst-mode gas core reactor, Brayton cycle space power system

    International Nuclear Information System (INIS)

    Reactor dynamics and system stability studies are performed on a conceptual burst-mode gaseous core reactor space nuclear power system. This concept operates on a closed Brayton cycle in the burst mode (on the order of 100-MW output for a few thousand seconds) using a disk magnetohydrodynamic generator for energy conversion. The fuel is a gaseous mixture of UF4 or UF6 and helium. Nonlinear dynamic analysis is performed using circulating-fuel, point-reactor-kinetics equations along with thermodynamic, lumped-parameter heat transfer and one-dimensional isentropic flow equations. The gaseous nature of the fuel plus the fact that the fuel is circulating lead to dynamic behavior that is quite different from that of conventional solid-core systems. For the transients examined, Doppler fuel temperature and moderator temperature feedbacks are insignificant when compared with reactivity feedback associated with fuel gas density variations. The gaseous fuel density power coefficient of reactivity is capable of rapidly stabilizing the system, within a few seconds, even when large positive reactivity insertions are imposed; however, because of the strength of this feedback, standard external reactivity insertions alone are inadequate to bring about significant power level changes during normal reactor operation. Additional methods of reactivity control, such as changes in the gaseous of fuel mass flow rate or core inlet pressure, are required to achieve desired power level control. Finally, linear stability analysis gives results that are qualitatively in agreement with the nonlinear analysis

  16. Integrated solar thermal Brayton cycles with either one or two regenerative heat exchangers for maximum power output

    International Nuclear Information System (INIS)

    The main objective of this paper is to optimise the open-air solar-thermal Brayton cycle by considering the implementation of the second law of thermodynamics and how it relates to the design of the heat exchanging components within it. These components included one or more regenerators (in the form of cross-flow heat exchangers) and the receiver of a parabolic dish concentrator where the system heat was absorbed. The generation of entropy was considered as it was associated with the destruction of exergy or available work. The dimensions of some components were used to optimise the cycles under investigation. EGM (Entropy Generation Minimisation) was employed to optimise the system parameters by considering their influence on the total generation of entropy (destruction of exergy). Various assumptions and constraints were considered and discussed. The total entropy generation rate and irreversibilities were determined by considering the individual components and ducts of the system, as well as their respective inlet and outlet conditions. The major system parameters were evaluated as functions of the mass flow rate to allow for a proper discussion of the system performance. The performances of both systems were investigated, and characteristics were listed for both. Finally, a comparison is made to shed light on the differences in performance. - Highlights: • Implementation of the second law of thermodynamics. • Design of heat exchanging and collecting equipment. • Utilisation of Entropy Generation Minimization. • Presentation of a multi-objective optimization. • Raise efficiency with more regeneration

  17. System Mass Variation and Entropy Generation in 100-kWe Closed-Brayton-Cycle Space Power Systems

    Science.gov (United States)

    Barrett, Michael J.; Reid, Bryan M.

    2004-02-01

    State-of-the-art closed-Brayton-cycle (CBC) space power systems were modeled to study performance trends in a trade space characteristic of interplanetary orbiters. For working-fluid molar masses of 48.6, 39.9 and 11.9 kg/kmol, peak system pressures of 1.38 and 3.0 MPa and compressor pressure ratios ranging from 1.6 to 2.4, total system masses were estimated. System mass increased as peak operating pressure increased for all compressor pressure ratios and molar mass values examined. Minimum mass point comparison between 72% He at 1.38 MPa peak and 94% He at 3.0 MPa peak showed an increase in system mass of 14%. Converter flow loop entropy generation rates were calculated for 1.38 and 3.0 MPa peak pressure cases. Physical system behavior was approximated using a pedigreed NASA-Glenn modeling code, Closed Cycle Engine Program (CCEP), which included realistic performance prediction for heat exchangers, radiators and turbomachinery.

  18. Mecanismos do ciclo sono-vigília Sleep-wake cycle mechanisms

    Directory of Open Access Journals (Sweden)

    Flávio Alóe

    2005-05-01

    Full Text Available Três sub-divisões hipotalâmicas são importantes no ciclo sono-vigília: o hipotálamo anterior (núcleos gabaérgicos e núcleos supraquiasmáticos, o hipotálamo posterior (núcleo túbero-mamilar histaminérgico e o hipotálamo lateral (sistema hipocretinas. O sistema gabaérgico inibitório do núcleo pré-óptico ventro-lateral (VLPO do hipotálamo anterior é responsável pelo início e manutenção do sono NREM. Os neurônios supraquiasmáticos (NSQs do hipotálamo anterior são responsáveis pelo ritmo circadiano do ciclo sono-vigília. Os núcleos aminérgicos, histaminérgicos, as hipocretinas e núcleos colinérgicos do prosencéfalo basal apresentam-se ativos durante a vigília, inibindo o núcleo pré-óptico ventro-lateral, promovendo a vigília. O processo de inibição-estimulação é a base do modelo da interação recíproca entre os grupos de células wake-off-sleep-on e células wake-off-sleep-on reguladores do ciclo sono-vigília. O modelo da interação recíproca também se aplica aos núcleos colinérgicos (células REM-on e aminérgicos (células REM-off do tronco cerebral no controle temporal do sono REM-NREM.Neurochemically distinct systems interact regulating sleep and wakefulness. Wakefulness is promoted by aminergic, acetylcholinergic brainstem and hypothalamic systems. Each of these arousal systems supports wakefulness and coordinated activity is required for alertness and EEG activation. Neurons in the pons and preoptic area control rapid eye movement and non-rapid eye movement sleep. Mutual inhibition between these wake- and sleep-regulating systems generate behavioral states. An up-to-date understanding of these systems should allow clinicians and researchers to better understand the effects of drugs, lesions, and neurologic disease on sleep and wakefulness.

  19. Aspectos nutricionais relacionados ao ciclo menstrual Nutritional aspects related to menstrual cycle

    Directory of Open Access Journals (Sweden)

    Helena Alves de Carvalho SAMPAIO

    2002-09-01

    Full Text Available O objetivo da presente revisão é apresentar os principais tópicos discutidos na literatura quanto à associação da nutrição com o ciclo menstrual, contribuindo para a implementação do atendimento nutricional de mulheres. São revisados aspectos referentes à fisiologia da menstruação, alterações metabólicas durante o ciclo menstrual e comportamentos alimentares associados a ele. Considerando-se o ciclo menstrual dividido em duas fases, a folicular e a lútea, é nesta última que são descritas mais alterações, como retenção de água, elevação de peso, aumento de demanda energética, modificações no perfil lipídico e no metabolismo de vitamina D, cálcio, magnésio e ferro, hipersensibilidade emocional, dores generalizadas e mudança do comportamento alimentar. Em relação a este último item, podem ocorrer maior ingestão energética e o desenvolvimento de compulsões alimentares, principalmente por chocolate, doces e alimentos muito salgados. É fundamental que todos os aspectos citados sejam investigados durante a consulta nutricional, a fim de serem adotadas condutas mais específicas.The aim of the present review is to show the most important topics discussed in literature about the association between nutrition and menstrual cycle, contributing to improve the nutritional care for women. Aspects related to physiology of the menstruation, metabolic changes and feeding behavior during the menstrual cycle are reviewed. Considering the menstrual cycle divided in two phases, follicular and luteal, it is in this last one that more alterations are described, like fluid retention, weight gain, increase in caloric needs, modifications in the lipid profile and in the metabolism of vitamin D, calcium, magnesium and iron, emotional hypersensitivity, aches and changes in feeding behavior. In relation to this last item, it can occur a higher caloric intake and the development of food cravings, mainly for chocolate, candies and

  20. Fosfolipasa A2-II sérica durante el ciclo menstrual, embarazo y puerperio

    Directory of Open Access Journals (Sweden)

    Eduardo Reyna-Villasmil

    2003-07-01

    Full Text Available Objetivo: Evaluar los niveles circulantes de fosfolipasa A2-II durante el ciclo menstrual normal y determinar sus alteraciones en las concentraciones maternas circulantes durante el ciclo menstrual, el embarazo y el puerperio. Método: Las concentraciones séricas de fosfolipasa A2-II se compararon entre 28 mujeres no embarazadas con ciclo menstruales normales, 57 embarazadas normales y 11 mujeres en el séptimo día del posparto normal. También se cuantificó en 8 pacientes con amenaza de parto pretérmino. Los niveles de fosfolipasa A2-II antes y después del parto se cuantificaron para determinar las diferencias en 8 neonatos obtenidos por vía vaginal y 8 por cesárea selectiva. Se tomó una muestra de sangre de 10 mL en la mañana y se realizó una prueba inmunorradiométrica, usando la combinación de dos anticuerpos monoclonales, para determinar la fosfolipasa A2-II en el suero. Resultados: Las concentraciones séricas de fosfolipasa A2-II en la fase lútea fueron significativamente menores que en la fase menstrual o folicular (pObjective: To evaluate phospholipaseA2-II circulating levels during normal menstrual cycle and determine alterations in maternal circulating phospholipaseA2-II concentrations during menstrual cycle, pregnancy and puerperium. Method: Serum phospholipaseA2-II concentrations were compared among 28 non-pregnant women with normal menstrual cycle, 57 normal pregnant women and 11 women at seventh day of puerperium. Also were measured in 8 patients with threatened premature labor. phospholipaseA2-II levels before and after delivery were made to determine differences in 8 neonates delivered vaginally and 8 neonates delivered by cesarean section. A 10-mL blood sample was obtained in the morning and an immunoradiometric assay, using two monoclonal antibodies, to determine serum phospholipaseA2-II. Results: Serum phospholipaseA2-II concentrations at luteal phase were significantly lower than those at menstrual o follicular

  1. Implicaciones del estudio de inestabilidad del ciclo celular en la biología del cáncer.

    Directory of Open Access Journals (Sweden)

    Luis Tume-Farfán

    2014-01-01

    Full Text Available Todas las células poseen mecanismos para mantener la integridad genómica que es vital para la supervivencia celular y la proliferación. Las células se dividen a tasas normale s durante su tiempo de vida, cuando esta tasa sobrepasa los límites normales ocurren alteraciones a nivel genético que afectan el control del ciclo celular por lo tanto estas células crecen y se dividen sin control y ya no responden a señalización extrace lular que indica la detención del ciclo y la apoptosis, estos mecanismos son los encargados de la prevención del cáncer que por lo generales se produce a través de la regulación estricta del ciclo celular por grupos de proteínas que interactúan entre sí e n una secuencia muy específica de eventos. Son estos acontecimientos los que determinan si el ciclo celular seguirá adelante o quedará estancado entre etapas. La falta de eficiencia en la replicación del ADN y el mantenimiento de esta macromolécula puede s er consecuencia de mutaciones deletéreas que conducen a la muerte celular o, en los organismos multicelulares a cáncer. El objetivo de esta revisión es discutir las vías de transducción de señales conocidas que regulan la progresión del ciclo celular y los mecanismos que las células emplean para asegurar la estabilidad del ADN, así como los avances que se están alcanzando en una forma de evitar esta proliferación descontrolada en las células con tendencia a ser cancerosa

  2. Efecto in vitro de olomoucina en el ciclo celular de linfocitos humanos

    Directory of Open Access Journals (Sweden)

    Camargo M.

    2001-06-01

    Full Text Available La olomoucina, un derivado de purina relacionado con el ATP, ha sido reportado como uneficiente inhibidor del ciclo celular de células animales y vegetales, debido a su alta especificidadpor las ciclinas dependientes de kinasa (CDK CDK1 y CDK2, su capacidad radica en inhibir elciclo celular en las transiciones G2/M y G1/S respectivamente. Con el objetivo de explorar lapotencial aplicación de la olomoucina en el análisis citogenético de alta resolución y estudiosde proliferación celular en cultivos primarios, linfocitos humanos fueron cultivados en RPMI1640 suplementado con suero bovino fetal al 5%, estimuladas durante 72 horas con PHA yposteriormente tratadas con concentraciones de 50, 100 y 200 mM durante 12 y 24 horas.

  3. Mecanismos do ciclo sono-vigília Sleep-wake cycle mechanisms

    OpenAIRE

    Flávio Alóe; Alexandre Pinto de Azevedo; Rosa Hasan

    2005-01-01

    Três sub-divisões hipotalâmicas são importantes no ciclo sono-vigília: o hipotálamo anterior (núcleos gabaérgicos e núcleos supraquiasmáticos), o hipotálamo posterior (núcleo túbero-mamilar histaminérgico) e o hipotálamo lateral (sistema hipocretinas). O sistema gabaérgico inibitório do núcleo pré-óptico ventro-lateral (VLPO) do hipotálamo anterior é responsável pelo início e manutenção do sono NREM. Os neurônios supraquiasmáticos (NSQs) do hipotálamo anterior são responsáveis pelo ritmo circ...

  4. La sostenibilidad en la arquitectura industrializada: cerrando el ciclo de los materiales

    Directory of Open Access Journals (Sweden)

    Wadel, G.

    2010-03-01

    Full Text Available The condition of sustainability, from a physical point of view, can be defined as the closure of the material cycle. This is reached in determined systems, in the absence of residual flows, and in which resources are constantly recycled. Such systems can encounter serious obstacles in the productive model that characterises the majority of contemporary industry. The productive model, born during the Industrial Revolution, can be summarised by the following lineal sequence: extraction > manufacture > use > residue. In contrast, this research focuses on a productive model from the ecological industry, based on the example of the biosphere as a recycling machine. Requiring the elimination of the concept of residues, the system can be summarised by the following continuous cycle: recycling-manufacturing-use-recycling. The hypothesis posed is as follows: using technology presently available, represented by the lightweight modular construction that is commercialised by renting (making it possible to return the modules to the factory once their useful life is over, therefore recuperating resources, a management system capable to close the material cycle at least to 90% can be developed. (conventional building construction currently manages a recycling value of 10% of used resources.

    La condición de sostenibilidad, desde el punto de vista físico, puede ser definida como el cierre de los ciclos materiales, alcanzándose éste en un sistema determinado cuando no existen flujos de residuos sino que los recursos se reciclan constantemente. Tal condición encuentra un fuerte obstáculo en el modelo productivo que caracteriza a la mayor parte de la industria contemporánea, nacido en la revolución industrial, que puede sintetizarse en la secuencia lineal extracción > fabricación > uso > residuo. En oposición a ello, el modelo productivo en el que se centra la investigación que aquí se presenta es la ecología industrial y se basa en el

  5. La persistencia de la desigualdad en la última fase del ciclo vital

    OpenAIRE

    Rodríguez Alemán, Rosalía

    2011-01-01

    Desde el marco analítico de la perspectiva de género, se analiza la satisfacción en la última etapa del ciclo vital. Se parte del hecho de que las mujeres son más longevas que los varones, por lo que es factible suponer que en la tercera edad pueden acceder a una autorrealización postergada al no estar sometidas a la satisfacción de las necesidades ajenas (familiares y/o comunitarias), lo que les permitiría vivir la vejez de manera más satisfactoria que sus coetáneos. La investigación, sin...

  6. Quase adulta, quase velha: por que antecipar as fases do ciclo vital?

    OpenAIRE

    Russel Parry Scott

    2001-01-01

    A partir de duas observações em gerações diferentes, identifica-se um fenômeno de antecipação da passagem pelas fases do ciclo vital que merece uma interpretação. Muitas jovens engravidam, casando ou não, e se tornam mães. Muitas mulheres na faixa de quarenta e cinco a cinqüenta anos ingressam em "grupos de idosos". A interpretação oferecida examina as conseqüências 1) da transição demográfica (e decorrente envelhecimento populacional) em dar visibilidade especial a estas gerações examinadas,...

  7. Guías preventivas por ciclo vital individual en Colombia

    OpenAIRE

    Carlos Andrés Pineda

    2006-01-01

    Las guías preventivas son una condensación de las diferentes intervenciones en promoción de la salud y prevención de la enfermedad que se hacen para intervenir las poblaciones. Contienen estrategias de consejería, filtrado y medidas específicas de protección. Se menciona las características de una prueba de cribado. Se presentan las guías preventivas por cada ciclo vital individual en cuanto a medidas de consejería, protección específica y filtro. Así, se ofrece una guía concreta sobre las ...

  8. Desenvolvimento de um sistema de controlo para um motor a funcionar segundo um Ciclo de Otto

    OpenAIRE

    Abrantes, Ricardo Afonso Pereira Braz

    2008-01-01

    O presente trabalho tinha o como propósito o desenvolvimento de um sistema de controlo para gerir um grupo propulsor constituído por um motor a funcionar segundo o ciclo de Otto e uma caixa de velocidades. Era também objectivo do trabalho testar as soluções propostas. Neste trabalho é sugerido um método de teste de injectores, um método de gestão do motor e da caixa de velocidades. No método de gestão do motor incluem-se rotinas de geração de mistura e posterior igniç...

  9. Los ciclos económicos departamentales en Colombia, 1960-2011

    Directory of Open Access Journals (Sweden)

    Fredy Vásquez Bedoya

    2014-06-01

    Full Text Available En este trabajo se estima el ciclo del PIB nacional y de algunos departamentos entre 1960 y 2011 usando el modelo de tendencia lineal local de Nelson y Plosser, así como el coeficiente de correlación entre el componente cíclico de las series del PIB departamental y nacional para clasificar sus co-movimientos. El estudio revela una diversidad de comportamientos de las fluctuaciones económicas departamentales con respecto a la nacional y, además, que las economías departamentales fuertemente procíclicas son las más diversificadas y más ricas.

  10. Tipos de hogar, ciclo de vida familiar y pobreza en Costa Rica 1987-2002

    Directory of Open Access Journals (Sweden)

    Barquero, Jorge

    2004-07-01

    Full Text Available El propósito de este estudio fue el de explorar las condiciones vulnerabilidad sociodemográfica en Costa Rica, a partir del análisis de los cambios en los tipos de hogar y el ciclo de vida de las familias en condiciones de pobreza, utilizando información de las Encuestas de Hogares de 1987, 1994 y 2002. Los principales hallazgos revelan modificaciones importantes en la estructura y composición de los hogares y familias en el periodo de estudio, asociado a cambios en la dinámica sociodemográfica de la sociedad costarricense. La evolución en la incidencia de la pobreza por tipo de hogar muestra que ésta es mayor entre los hogares nucleares que cuentan con hijos y al convertirse en monoparentales. La incidencia es más alta en 1987, se reduce para 1994 y prácticamente se mantiene para el 2002. No obstante que en todas las fases del ciclo de vida familiar la incidencia de la pobreza disminuyó en el periodo 1987-1994, en el periodo más reciente al 2002 la incidencia es mayor en las etapas en que las familias poseen más hijos dependientes menores de 18 años, lo que expone a estas familias a una mayor vulnerabilidad a situaciones de pobreza. Los hogares y familias con mayor riesgo de vulnerabilidad ante la pobreza, se hallaron entre aquellos con mayor cantidad de miembros dependientes menores de edad y jefeados por mujeres. No se encontraron evidencias significativas para afirmar que el estancamiento observado en los niveles de pobreza en el país hasta el 2002, fuese producto de los cambios encontrados en los patrones familiares, aunque ciertamente se hace necesario profundizar el análisis de las interrelaciones entre pobreza y cambios demográficos.

  11. Ciclos y determinantes del crecimiento económico: Perú 1950-1996

    Directory of Open Access Journals (Sweden)

    Félix Jiménez

    1997-12-01

    Full Text Available En este ensayo se analiza el crecimiento económico y sus fluctuacionesdurante el período 1950-1995, así como el estancamiento prolongado queempieza en los años 1975-1978, apoyados en la hipótesis de que la dinámicade este crecimiento obedece al carácter desequilibrado del proceso de industrializacióny a un comportamiento de la inversión que no estuvo sujeta alproceso sustitutivo. Con un vector de inversiones que no estimula el mercadodoméstico, el crecimiento y los ciclos son determinados por impulsos dedemanda que provienen del sector público y/o de aquellos mercados externosdonde la producción manufacturera doméstica resulta competitiva. Como elaumento de la demanda repercute en un mayor déficit externo, ei crecimientosostenido a largo plazo resulta imposible si no se resuelven los problemasestructurales del sector manufacturero. Una vez corroborada la importancia deeste sector y dadas sus correlaciones significativas con los otros sectoresdeterminados por demanda, se construye una serie de producción no primaria,para luego explicar su comportamiento en el largo plazo, sometiendo a pruebala importancia del gasto del Estado en la generación de los ciclos y tendenciadel producto, utilizando la metodología de la cointegración. Por último, seestima el valor del producto potencial no-primario que permite corroborar lahipótesis del largo estancamiento en el período de agotamiento del procesosustitutivo.

  12. El análisis del ciclo de vida en la cuantificación de desechos de dos productos elaborados a partir de langosta

    OpenAIRE

    Cruz Núñez, G.

    2010-01-01

    El Análisis del Ciclo de Vida (ACV) es un método para analizar y evaluar los efectos y cargas ambientales causados por un producto, proceso o actividad durante su ciclo de vida completo “de la cuna a la tumba”, constituye una herramienta integral orientada hacia el producto y analiza las consecuencias potenciales que el mismo pueda causar para el medio ambiente a lo largo de su ciclo de vida. En el trabajo se realiza, de manera preliminar, el ACV a dos productos elaborados a parti...

  13. Estudio de Reducción del Consumo de Agua desmineralizada de una Central Térmica de Ciclo Combinado Aplicando la Estrategia Six Sigma

    OpenAIRE

    Vila González, Carlos Jesús

    2013-01-01

    Este proyecto fin de carrera surge de la necesidad de reducir el consumo de agua desmineralizada de caldera en una central de ciclo combinado. La fabricación y aportación al ciclo de agua desmineralizada, así como su adecuación química al proceso, hace que sea un elemento que interviene de forma importante en los costes de producción del proceso, por lo que se hace indispensable reducir su consumo. La central térmica de ciclo combinado que nos ocupa consta de un solo tren de potencia, fo...

  14. Simulation of operational an accidental behaviour of modular high temperature reactors with Brayton cycle Power Conversion Unit

    International Nuclear Information System (INIS)

    The present work analyses and investigates the behaviour of a High Temperature Reactor (HTR) with a Pebble Bed core connected to a Brayton cycle Power Conversion Unit (PCU) during operational and accident conditions. The modelling of a complete circuit including both the PCU and the Pebble Bed Reactor has been performed with the commercial thermal-fluid analysis simulation code Flownex. Flownex has been developed for High Temperature Pebble Bed Reactor applications, and has been exten-sively validated against other codes. As the reactor core model incorporated in Flownex is a simplified model based on 0D point kinetics, the extended 1D WKIND core model was implemented in the analysis calculations using a special coupling methodology. This study introduces a new sub-routine which enables the cou-pling of the WKIND reactor core model to the Flownex PCU model via an external interface. The interface facilitates the data exchange between the two codes, allowing for necessary manipulations and synchronisation of the coupled codes. By doing so, the 1D diffusion equation solution implemented in WKIND core model replaces the point kinetics model implemented in Flownex. This replacement allows for a detailed accurate solution even for very fast transients, through the treatment of the space-dependent heat conduction from the graphite matrix to helium. Flownex component models have been validated against the experimental results of the 50 MWel direct helium turbine facility Energieversorgung Oberhausen (EVO II). This provided the opportunity to validate Flownex calculations against experimental data derived from a large-scale helium Brayton cycle installation. Small differences observed in the results could be explained. Based upon steady state and transient analysis it is concluded that Flownex models simulate accurately the behaviour of the components integrated in the EVO II plant. Such models could be applied to analyse the transient behaviour of the total system of the

  15. Off-design performance prediction of Radial Compressor of Supercritical CO2 Brayton Cycle for KAIST Micro Modular Reactor

    International Nuclear Information System (INIS)

    KAIST research team suggested a new concept of SMR, which utilizes S-CO2 as the operating fluid and coolant. It was named as KAIST MMR(Micro Modular Reactor). Compared with existing SMR concepts, this reactor has advantages of achieving smaller volume of power conversion unit (PCU) containing the core and PCU in one vessel for the complete modularization passive air-cooling system more flexible installation in the inland area. In previous study, performance of turbomachinery in PCU was considered only on-design. But, off-design performances of each component can affect not only PCU but also the core because this reactor adopts the direct S-CO2 loop in GFR. Nuclear system is applied by relatively conservative criteria of safety. Thus, off-design performances of each component should be considered in order to be more realistic reactor. The suggested turbomachinery size of the S-CO2 cycle is relatively smaller than those of helium Brayton cycle and steam Rankine cycle. Performance analysis of compressor is conducted by KAIST-TMD in case of on-design and off-design. Compressor efficiency in on-design conditions is obtained 84.51 %. But compressor performance in off-design conditions decreases certainly. This means that more heat than existing prediction is rejected by air-cooling system. KAIST-TMD will be verified with more experiment data for providing the results of more accurate analysis. Also, this code will be modified to couple with safety analysis codes and S-CO2 cycle analysis codes in the future. Furthermore, authors will consider aerodynamic performance analysis and various losses for more realization

  16. Design of a three-phase, 15-kilovolt-ampere static inverter for motor-starting a Brayton space power system

    Science.gov (United States)

    Frye, R. J.; Birchenough, A. G.

    1971-01-01

    The design of a three-phase, 400-Hz, 15-kVA static inverter for motor-starting the 2- to 15-kWe Brayton electrical space power system is described. The inverter operates from a nominal 56-V dc source to provide a 28-V, rms, quasi-square-wave output. The inverter is capable of supplying a 200-A peak current. Integrated circuitry is used to generate the three-phase, 400-Hz reference signals. Performance data for a drive stage that improves switching speed and provides efficient operation over a range of output current and drive supply voltage are presented. A transformerless, transistor output stage is used.

  17. Experimental life cycle of Lagochilascaris minor Leiper, 1909 Ciclo evolutivo experimental de Lagochilascaris minor, Leiper 1909

    Directory of Open Access Journals (Sweden)

    Dulcinéa Maria Barbosa Campos

    1992-08-01

    Full Text Available The life cycle of Lagochilascaris minor was studied using material collected from human lesion and applying the experimental model: rodents (mice, hamsters, and carnivorae (cats, dogs. In mice given infective eggs, orally, hatch of the third stage larvae was noted in the gut wall, with migration to liver, lungs, skeletal musculature and subcutaneous tissue becoming, soon after, encysted. In cats infected with skinned carcasses of mice (60 to 235 days of infection it was observed: hatch of third stage larvae from the nodules (cysts in the stomach, migration through the oesophagus, pharynx, trachea, related tissues (rhino-oropharynx, and cervical lymphonodes developing to the mature stage in any of these sites on days 9-20 post inoculation (P.I.. There was no parasite development up to the mature stage in cats inoculated orally with infective eggs, which indicates that the life cycle of this parasite includes an obligatory intermediate host. In one of the cats (fed carcass of infected mice necropsied on day 43 P.I., it was observed the occurence of the self-infective cycle of L. minor in the lung tissues and in the cervical region which was characterized by the finding of eggs in different stages of development, third stage larvae and mature worms. It's believed that some component of the carnivorae gastrointestinal tracts may preclude the development of third stage larvae from L. minor eggs what explains the interruption of the life cycle in animals fed infective eggs. It's also pointed out the role of the intermediate host in the first stages of the life cycle of this helminth.A partir de material colhido de lesões humanas estudou-se o ciclo evolutivo de Lagochilascaris minor empregando-se o modelo experimental: roedores (camundongos, hamster e carnívoros (gatos, cão. Em camundongos inoculados com ovos infectantes, por via oral, observou-se eclosão de larvas de 3º estágio na parede do intestino, migração das mesmas para o fígado, pulm

  18. Estudo comparativo do ciclo evolutivo de Rhodnius neglectus alimentados em pombos ou camundongos

    Directory of Open Access Journals (Sweden)

    Liléia Diotaiuti

    1987-06-01

    Full Text Available Baseados no encontro de 77,2% de reação de precipitina positiva para soro antiave de R. neglectus capturados em palmeiras da periferia de Belo Horizonte, estudamos o ciclo evolutivo de uma colonia recém-estabelecida no laboratório alimentada com sangue de pombo ou camundongo, na expectativa de demonstrarmos maior adaptação deste triatomíneo ao sangue da ave. Para comparação, estudamos o ciclo evolutivo destes insetos numa colônia há muito mantida em insetário. Nossos resultados mostram um desenvolvimento mais rápido da colônia recém- estabelecida, assim como do lote de triatomíneos alimentado em camundongo. Esses achados sugerem menor potencial biológico para triatomíneos criados por longo tempo em insetário em comparação a novas colônias. Sendo as aves os principais habitantes das palmeiras, a aparente preferência alimentar por sangue de aves demonstrada pela reação de precipitina parece ser circunstancial e não seletiva na busca do sangue com o qual o triatomíneo obteria melhor desenvolvimento.Feeding pattems of R. neglectus collected in palm trees around Belo Horizonte (Minas Gerais, Brazil were investigated. Precipitin tests showed 77.2% of avian blood. In view of these results, a new colony of R. neglectus established in the laboratory was fed regularly on pigeons or mice, in order to verify a possible better adaptation of this insect to the avian blood. As a control group a colony of R neglectus which has been maintained for several years in the laboratory was also observed. The results show a better development of the “new" colony in comparison with the old one, and of those bugs nourished with mice blood. Such findings suggest a poorer biological potential for triatomines maintained for long time in artificial conditions, in comparison with those living in the natural environment. As birds are the main vertebrate inhabitants of palm trees (the natural ecotope of R neglectus, the apparent feeding preference of

  19. Importancia de los acontecimientos vitales como factores de cambio en el ciclo vital

    Directory of Open Access Journals (Sweden)

    Luis MELERO MARCOS

    2009-11-01

    Full Text Available RESUMEN: A lo largo del ciclo vital, los individuos experimentan una serie de acontecimientos que, sin duda, influyen en su desarrollo individual y colectivo. Tales acontecimientos parecen introducir cambios en la vida de los sujetos. El presente trabajo pretende analizar la importancia de los acontecimientos vitales como factores de cambio, desde la consideración de que el estudio de los mismos es consustancial con el estudio del ciclo vital. Desde este punto de partida, se ha establecido la existencia de diversos tipos de clasificaciones de acontecimientos, como la aportada por Rodrigo (1985, que plantea la existencia de tres tipos de eventos, eventos normativos relacionados con la edad, eventos normativos relacionados con el tiempo histórico, y finalmente, un tercer tipo de acontecimientos considerados como no normativos, que solamente son experimentados por algunos sujetos a lo largo de su vida. Analizaremos aquellos factores que adquieren significado en el desarrollo de los acontecimientos vitales y en la forma como los perciben los individuos que los experimentan, desde la revisión de los principales modelos explicativos, polarizados en dos grandes paradigmas, organicista y mecanicista, así como el intento de aproximación a través de modelos contextúales-dialécticos a una posición intermedia entre el paradigma organicista y el paradigma mecanicista.ABSTRACT: Throughout the vital cycle, individuals undergo experiences which no doubt exert an influence on their development. The present article analyzes the importance of vital events as change factors. We assume their inseparability. Adopting the classification established by Rodrigo (1985 we distinguish three classes of events, namely, normative events related to age, normative events related to historical time and non normative events which are not universally experienced by all subjects. We will analyze those factors which have relevant meaning in the development of vital events

  20. Niveles de progesterona durante el ciclo normal y silencioso en bovinos en el trópico colombiano

    Directory of Open Access Journals (Sweden)

    Henry Grajales L

    2010-08-01

    Full Text Available Objetivo. Determinar la secuencia de cambios en los niveles de progesterona (NP durante el Ciclo Normal (CN y Ciclo Silencioso (CS. Materiales y métodos. 94 Hembras de los grupos raciales Holstein x Cebú (HC, Simmental x Cebú (SC, Romosinuano (R y Cebú (C se estudiaron desde la pubertad y durante los tres primeros ciclos estrales. Se tomaron muestras de sangre para determinar las concentraciones de progesterona mediante Radioinmunoanálisis, se determinaron 184 perfiles de progesterona para CN y 153 para CS. Para el análisis de la información se utilizó el programa estadístico SAS. Resultados. El grupo R presenta un patrón de variaciones de los NP a través de las fases del CN que tienediferencias significativas con el comportamiento de los NP en las fases del CN de los grupos SC, HC y C. Los niveles de progesterona en cada fase del CS coinciden con una fase luteal con bajos niveles de progesterona. Solo se encontraron diferencias significativas en la fase luteal tardía al comparar el CN con el CS, sin embargo se presentan diferencias numéricas en todas las fases entre estos dos tipos de ciclos. Conclusiones. Las concentraciones de progesterona tienen un marcado efecto sobre la presentación del CS, no obstante es difícil definir una concentración de progesterona que caracterice cada evento (CN o CS, sin embargo, es evidente que la progesterona influye sobre las probabilidades para que se de una respuesta reproductiva favorable o desfavorable.

  1. Uma aplicação de software educativo no 1º ciclo do ensino básico

    OpenAIRE

    Pequeneza, Tânia Vanessa Costa

    2013-01-01

    Relatório de Estágio apresentado à Escola Superior de Educação do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré-Escolar e Ensino do 1º Ciclo do Ensino Básico

  2. CICLO DE VIDA ORGANIZACIONAL E CONTROLE GERENCIAL: UMA ANÁLISE DOS ARTIGOS EM PERIÓDICOS INTERNACIONAIS DE CONTABILIDADE

    Directory of Open Access Journals (Sweden)

    Paulo Roberto da Cunha

    2013-12-01

    Full Text Available O objetivo deste estudo é analisar os artigos sobre a abordagem do ciclo de vida organizacional em nível internacional, levantando os principais tópicos associados com os controles gerenciais. Em pesquisa a 67 periódicos, chegou-se a uma amostra inicial de 39 artigos. Após a leitura dos resumos para identificação dos artigos que relacionassem ciclo de vida organizacional com controles gerenciais, a amostra ficou em sete artigos. O periódico internacional de contabilidade que mais publicou artigos relacionados a ciclo de vida organizacional foi o Management Accounting Research. As publicações são recentes, dois artigos em 2005 e três artigos em 2008. Destaca-se que nos artigos publicados em 2008, todos são de autoria ou co-autoria de Hanna Silvola. O pequeno número de estudos encontrados permite que o tema possa ser objeto de mais pesquisas, contribuindo com as organizações, gestores e outros interessados a entender melhor como esses controles são utilizados e se modificam com a evolução da empresa. 

  3. Monitoramento do ciclo estral de cutias (Dasyprocta leporina Lichtenstein, 1823 através de citologia esfoliativa vaginal e ultrassonografia

    Directory of Open Access Journals (Sweden)

    Lívia B. Campos

    2015-02-01

    Full Text Available O objetivo deste estudo foi monitorar o ciclo estral em cutias (Dasyprocta leporina criadas em cativeiro no semiárido brasileiro. Durante 70 dias, cinco cutias foram diariamente submetidas a citologia esfoliativa vaginal, e o monitoramento ultrassonográfico ovariano foi realizado a cada três dias. Um total de 8 ciclos estrais foi completamente monitorado, com duração de 28,2±0,7 dias, variando de 24 a 31 dias. Pela citologia esfoliativa vaginal, houve uma predominância de células superficiais nas fases de proestro e estro (P0,05. Os folículos foram identificados durante as fases estrogênicas (proestro e estro, com diâmetro médio de 1±0,5mm. Em apenas 12,5% das fases luteais, corpos lúteos medindo 1,4±0,9mm foram identificados. Conclui-se que a associação da citologia vaginal e da ultrassonografia ovariana constitui uma alternativa viável para o monitoramento de ciclos estrais e identificação das fases estrogênicas em cutias da espécie Dasyprocta leporina

  4. ESTUDO DO PRIMEIRO CICLO PRODUTIVO DA BANANEIRA `NANICÃO' (Musa sp. DESENVOLVIDA A PARTIR DE DIFERENTES TIPOS DE MUDA

    Directory of Open Access Journals (Sweden)

    SCARPARE FILHO J.A.

    1998-01-01

    Full Text Available Para avaliar o primeiro ciclo produtivo de bananeira `Nanicão' foram utilizados 5 tipos de muda: "chifrinho" e "chifrão" (brotações laterais com folhas lanceoladas, "guarda-chuva" (brotações separadas da planta mãe, com folhas normais, pedaços de rizoma e mudas micropropagadas. Foram avaliados o peso dos cachos, o número de pencas, o número de frutos por cacho e número de dias decorridos do plantio até a colheita. Os melhores desempenhos foram obtidos com as mudas "chifrinho" e "chifrão", que apresentaram maior equilíbrio das variáveis estudadas. As mudas constituidas de pedaços de rizoma, embora com uma produção alta, mostraram-se tardias no primeiro ciclo. O pior desempenho foi verificado nas mudas micropropagadas, com produções inferiores aos demais tratamentos, apresentando primeiro ciclo tardio e alta taxa de variação somaclonal.

  5. Development of the ANL plant dynamics code and control strategies for the supercritical carbon dioxide Brayton cycle and code validation with data from the Sandia small-scale supercritical carbon dioxide Brayton cycle test loop

    International Nuclear Information System (INIS)

    Significant progress has been made in the ongoing development of the Argonne National Laboratory (ANL) Plant Dynamics Code (PDC), the ongoing investigation and development of control strategies, and the analysis of system transient behavior for supercritical carbon dioxide (S-CO2) Brayton cycles. Several code modifications have been introduced during FY2011 to extend the range of applicability of the PDC and to improve its calculational stability and speed. A new and innovative approach was developed to couple the Plant Dynamics Code for S-CO2 cycle calculations with SAS4A/SASSYS-1 Liquid Metal Reactor Code System calculations for the transient system level behavior on the reactor side of a Sodium-Cooled Fast Reactor (SFR) or Lead-Cooled Fast Reactor (LFR). The new code system allows use of the full capabilities of both codes such that whole-plant transients can now be simulated without additional user interaction. Several other code modifications, including the introduction of compressor surge control, a new approach for determining the solution time step for efficient computational speed, an updated treatment of S-CO2 cycle flow mergers and splits, a modified enthalpy equation to improve the treatment of negative flow, and a revised solution of the reactor heat exchanger (RHX) equations coupling the S-CO2 cycle to the reactor, were introduced to the PDC in FY2011. All of these modifications have improved the code computational stability and computational speed, while not significantly affecting the results of transient calculations. The improved PDC was used to continue the investigation of S-CO2 cycle control and transient behavior. The coupled PDC-SAS4A/SASSYS-1 code capability was used to study the dynamic characteristics of a S-CO2 cycle coupled to a SFR plant. Cycle control was investigated in terms of the ability of the cycle to respond to a linear reduction in the electrical grid demand from 100% to 0% at a rate of 5%/minute. It was determined that

  6. Development of the ANL plant dynamics code and control strategies for the supercritical carbon dioxide Brayton cycle and code validation with data from the Sandia small-scale supercritical carbon dioxide Brayton cycle test loop.

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A.; Sienicki, J. J. (Nuclear Engineering Division)

    2011-11-07

    Significant progress has been made in the ongoing development of the Argonne National Laboratory (ANL) Plant Dynamics Code (PDC), the ongoing investigation and development of control strategies, and the analysis of system transient behavior for supercritical carbon dioxide (S-CO{sub 2}) Brayton cycles. Several code modifications have been introduced during FY2011 to extend the range of applicability of the PDC and to improve its calculational stability and speed. A new and innovative approach was developed to couple the Plant Dynamics Code for S-CO{sub 2} cycle calculations with SAS4A/SASSYS-1 Liquid Metal Reactor Code System calculations for the transient system level behavior on the reactor side of a Sodium-Cooled Fast Reactor (SFR) or Lead-Cooled Fast Reactor (LFR). The new code system allows use of the full capabilities of both codes such that whole-plant transients can now be simulated without additional user interaction. Several other code modifications, including the introduction of compressor surge control, a new approach for determining the solution time step for efficient computational speed, an updated treatment of S-CO{sub 2} cycle flow mergers and splits, a modified enthalpy equation to improve the treatment of negative flow, and a revised solution of the reactor heat exchanger (RHX) equations coupling the S-CO{sub 2} cycle to the reactor, were introduced to the PDC in FY2011. All of these modifications have improved the code computational stability and computational speed, while not significantly affecting the results of transient calculations. The improved PDC was used to continue the investigation of S-CO{sub 2} cycle control and transient behavior. The coupled PDC-SAS4A/SASSYS-1 code capability was used to study the dynamic characteristics of a S-CO{sub 2} cycle coupled to a SFR plant. Cycle control was investigated in terms of the ability of the cycle to respond to a linear reduction in the electrical grid demand from 100% to 0% at a rate of 5

  7. Una nueva copla sefardí antigua del ciclo de la reina Ester (Purim

    Directory of Open Access Journals (Sweden)

    Hassán, Iacob M.

    2007-12-01

    Full Text Available In this posthumous article (edited by Elena Romero, the author tries to determine the classical corpus of the Purim “Coplas” of the Queen Esther cycle, referring to their strophic structure, their authors and the problems of edition and diffusion. Likewise, this study represents a significant step in the establishment of a corpus of Purim “Coplas” known as “novísimas.” An edition is presented here of an hitherto unknown “Copla” belonging to the first group: La bebienda de Purim.

    En el presente artículo (postumo y editado por Elena Romero se determina el corpus clásico de las coplas de Purim del «ciclo de la reina Ester», aludiendo a su estrofismo, autores y problemt mática de las ediciones y su difusión; asimismo se avanza en la determinación del corpus de las coplas de Purim llamadas «novísimas». Finalmente se lleva a cabo la edición de una copla del primer grupo hasta ahora desconocida: La bebienda de Purim.

  8. Envejecimiento saludable: perspectiva de género y de ciclo vital

    Directory of Open Access Journals (Sweden)

    Mª Pilar Montero-López

    2015-04-01

    Full Text Available Objetivo: Identificar factores bioculturales y sociales que actúan en diferentes etapas del ciclo vital, implicados en la forma de envejecer de mujeres y hombres mayores de 65 años. Material y Método: 213 personas; edad media 73.9 (std=5.8 en mujeres y 74.8 (std=6.6 en hombres. Datos recogidos en Centros Culturales y de Ocio de la Comunidad de Madrid. El envejecimiento saludable (a partir del número de enfermedades diagnosticadas, percepción de la salud, satisfacción con la vida y estado auditivo y bucal,fue considerado como variable dependiente. La edad, sexo, nivel de estudios, talla sentado, envergadura, edad de primera maternidad y número total de hijos fueron consideradas como variables independientes. Se utilizaron modelos de regresión lineal múltiple para analizar la relación de estas variables con la calidad del envejecimiento. Resultados: El envejecimiento saludable se asocia negativamente con edad y directamente con talla sentado en hombres. En mujeres el envejecimiento saludable se asocia positivamente con años de educación, cuando se incluye la edad de primera maternidad,ésta es la única variable con efecto significativo. Conclusiones: Existen diferentes factores que actúan a lo largo de la vida de los hombres y de las mujeres y que afectan de manera distinta a su forma de envejecer.

  9. Necessidades e preocupações dos pais em diferentes etapas do ciclo vital

    Directory of Open Access Journals (Sweden)

    Bárbara Tarouco da Silva

    2014-12-01

    Full Text Available Objetivo: identificar as necessidades e as preocupações prioritárias, manifestadas pelos pais no desempenho do seu papel, em três etapas do ciclo vital: adolescência, idade produtiva e idade madura. Metodologia: estudo exploratório com abordagem qualitativa, desenvolvido com quatorze pais residentes em um município no extremo sul do Brasil. Os dados foram coletados entre maio e agosto de 2011, por meio de entrevista em profundidade. Através da técnica da análise textual discursiva e da matriz construída com base na teoria bioecológica de Bronfenbrenner, foram construídas três categorias: Necessidades/preocupações do pai, geradas em sua relação com o mundo do trabalho; Necessidades/preocupações que emergem da relação de cuidado com os filhos e Preocupações dos pais com relação ao futuro dos filhos. Conclusão: identificou-se que a preocupação com o futuro dos filhos foi apontada por pais de todas as faixas-etárias investigadas.

  10. Revisión teórica del modelo de ciclo de vida organizacional

    Directory of Open Access Journals (Sweden)

    Laura Angélica Décaro Santiago

    2014-06-01

    Full Text Available Los Modelos de Ciclo de Vida Organizacional (OLC, por sus siglas en inglés tienen por objetivo representar el nivel de desarrollo de la empresa a través de una serie de etapas consecutivas; diferenciadas por características propias y retos por resolver. Los autores que se han dedicado al estudio del tema consideran que un buen entendimiento sobre el nivel de desarrollo de la empresa, permite tener un visión más amplia de las características y necesidades de la misma para con ello, auxiliar a la toma de decisiones y por ende, prepararse para los retos presentes y futuros. Desde su aparición, en los años 50´s, OLC ha sido abordado por un gran número de académicos, investigadores, consultores y asesores de empresas. En la literatura se muestran tres periodos de estudio; la conceptualización, la evidencia empírica y la aplicación de nuevas metodologías de investigación; así como el estudio de sujetos y subsistemas más específicos. Así bien, este documento describe los modelos más representativos, sus adaptaciones y aplicaciones a lo largo de estos tres periodos; generando así una investigación de alcance descriptivo.

  11. Evidencias del ciclo Pampeano en el basamento del sector noroccidental de la sierra de San Luis

    Directory of Open Access Journals (Sweden)

    GI Vujovich

    2003-12-01

    Full Text Available Se presenta una edad preliminar U-Pb sobre circones de un gneis biotítico feldespático perteneciente al Complejo Nogolí aflorante en las cercanías de San Francisco del Monte de Oro, sierra de San Luis. Los resultados indican una edad de cristalización para el mismo de 554 ± 4,8 Ma, representando un interesante hallazgo del ciclo Pampeano en el marco geológico considerado. Se postula además la existencia de un proceso de pérdida episódica de Pb durante el Cretácico inferior (112 ± 23 Ma, reflejado en la intersección inferior de la recta de discordia. Esta edad inferior podría asociarse con gradientes térmicos anómalos relacionados con los procesos distensivos generalizados que afectaron al Gondwana durante la apertura del océano Atlántico Sur.

  12. A avaliação formativa por meio do feedback escrito no processo de ensino-aprendizagem de alunos de 2.º ciclo em matemática

    OpenAIRE

    Bento, Ana

    2016-01-01

    Relatório final apresentado para a obtenção do grau de mestre em Ensino do 1.º ciclo e do 2.º ciclo do ensino básico O presente relatório de estágio foi realizado no âmbito do Mestrado em Ensino do 1.º Ciclo e do 2.º Ciclos do Ensino Básico na Escola Superior de Educação do Instituto Politécnico de Santarém. Foca diversas experiências, trabalhos e atividades desenvolvidos nos estágios em 1.º ciclo e 2.º ciclo do ensino básico, que contribuíram para a minha formação profissional. Além disso...

  13. Investigation of plant control strategies for the supercritical C02Brayton cycle for a sodium-cooled fast reactor using the plant dynamics code

    International Nuclear Information System (INIS)

    The development of a control strategy for the supercritical CO2 (S-CO2) Brayton cycle has been extended to the investigation of alternate control strategies for a Sodium-Cooled Fast Reactor (SFR) nuclear power plant incorporating a S-CO2 Brayton cycle power converter. The SFR assumed is the 400 MWe (1000 MWt) ABR-1000 preconceptual design incorporating metallic fuel. Three alternative idealized schemes for controlling the reactor side of the plant in combination with the existing automatic control strategy for the S-CO2 Brayton cycle are explored using the ANL Plant Dynamics Code together with the SAS4A/SASSYS-1 Liquid Metal Reactor (LMR) Analysis Code System coupled together using the iterative coupling formulation previously developed and implemented into the Plant Dynamics Code. The first option assumes that the reactor side can be ideally controlled through movement of control rods and changing the speeds of both the primary and intermediate coolant system sodium pumps such that the intermediate sodium flow rate and inlet temperature to the sodium-to-CO2 heat exchanger (RHX) remain unvarying while the intermediate sodium outlet temperature changes as the load demand from the electric grid changes and the S-CO2 cycle conditions adjust according to the S-CO2 cycle control strategy. For this option, the reactor plant follows an assumed change in load demand from 100 to 0 % nominal at 5 % reduction per minute in a suitable fashion. The second option allows the reactor core power and primary and intermediate coolant system sodium pump flow rates to change autonomously in response to the strong reactivity feedbacks of the metallic fueled core and assumed constant pump torques representing unchanging output from the pump electric motors. The plant behavior to the assumed load demand reduction is surprising close to that calculated for the first option. The only negative result observed is a slight increase in the intermediate inlet sodium temperatures by about 10 C

  14. Trauma & the reproductive lifecycle in women Trauma e o ciclo reprodutivo feminino

    Directory of Open Access Journals (Sweden)

    Leslie Born

    2005-10-01

    Full Text Available Women are at significantly higher risk for developing post-traumatic stress disorder (PTSD than men, resulting in increased psychosocial burden and healthcare related costs. Recent research has shown complex interactions between the impact of traumatic experiences, and the reproductive lifecycle in women. For example, women suffering from premenstrual dysphoric disorder (PMDD who also report a history of sexual or physical abuse are more likely to present with different neuroendocrine reactivity to stressors, when compared to premenstrual dysphoric disorder subjects without prior history of trauma or abuse or non-premenstrual dysphoric disorder subjects. In addition, women with a history of abuse or trauma may experience re-emergence of symptoms during pregnancy. Lastly, females who experience miscarriage may present with even higher prevalence rates of post-traumatic stress disorder symptoms. In this manuscript we examine the existing data on gender differences in post-traumatic stress disorder, with particular focus on psychological and physiological factors that might be relevant to the development of symptoms after exposure to traumatic events associated with the reproductive life cycle. Current options available for the treatment of such symptoms, including group and counselling therapies and debriefing are critically reviewed.Mulheres estão sujeitas a um maior risco para o desenvolvimento de transtorno de estresse pós-traumático (TEPT do que os homens, o que acarreta prejuízos e custos significativos do ponto de vista psicossocial e de saúde pública. Estudos recentes mostram interações complexas entre o impacto de experiências traumáticas e o ciclo reprodutivo feminino. Por exemplo, mulheres com transtorno disfórico pré-menstrual (TDPM, que também relatam histórico de trauma ou abuso físico, estão mais sujeitas a apresentar uma resposta neuroendócrina diferenciada após exposição a um fator ou evento estressante, quando

  15. Estudio comparativo del autoconcepto físico a lo largo del ciclo vital

    Directory of Open Access Journals (Sweden)

    David Molero

    2013-01-01

    Full Text Available El propósito de esta investigación ha sido estudiar el autoconcepto físico y sus componentes a lo largo del ciclo vital, conocer si las valoraciones de cada una de las escalas están correlacionadas entre sí y comprobar la existencia de diferencias significativas a nivel estadístico en los resultados obtenidos en función de la edad y el sexo de los encuestados. La muestra está compuesta por 152 participantes distribuidos en tres grupos de edad (adolescentes, adultos y personas mayores de 50 años, los cuales contestaron al Cuestionario de Autoconcepto Físico (–CAF– Goñi, Ruiz de Azúa y Rodríguez, 2006. Los datos fueron analizados mediante el análisis de las puntuaciones medias, correlaciones y varianzas para las distintas escalas consideradas. Los resultados globales indican que el Autoconcepto Físico General mejora paulatinamente con el aumento de edad. Se han encontrado correlaciones positivas (p < .01 entre todas las escalas del instrumento empleado. En el grupo de hombres no existen diferencias significativas en las valoraciones realizadas en ninguno de los componentes del autoconcepto físico en función de los grupos de edad pero sí en la muestra de mujeres en las sub-escalas Habilidad Física y Fuerza (p < .05. El estudio de regresión realizado nos indica que la sub-escala que más predice el Autoconcepto Físico General es el Atractivo Físico, seguido de la Habilidad Física, Condición Física y Fuerza.

  16. Ciclos económicos y retórica administrativa. Dualidad ideológica en Colombia Ciclos económicos y retórica administrativa. Dualidad ideológica en Colombia

    OpenAIRE

    César Alexander Toro Suárez; Claudia Janeth Gómez David

    2007-01-01

    En 1992, Stephen R. Barley y Gideon Kunda, profesores de la universidad deStanford y de la universidad de Tel Aviv respectivamente, publicaron un estudiotitulado: “Desing and devotion: surges of rational and normative ideologies ofcontrol in managerial discourse”* en el que encontraron que en Estados Unidos,las teorías administrativas se presentan en oleadas de retórica en correspondenciadirecta con los ciclos económicos. De esta manera, las teorías de contenido racional(dirigidas al control ...

  17. The effects of intercooling and regeneration on the thermo-ecological performance analysis of an irreversible-closed Brayton heat engine with variable-temperature thermal reservoirs

    International Nuclear Information System (INIS)

    A thermo-ecological performance analysis of an irreversible intercooled and regenerated closed Brayton heat engine exchanging heat with variable-temperature thermal reservoirs is presented. The effects of intercooling and regeneration are given special emphasis and investigated in detail. A comparative performance analysis considering the objective functions of an ecological coefficient of performance, an ecological function proposed by Angulo-Brown and power output is also carried out. The results indicate that the optimal total isentropic temperature ratio and intercooling isentropic temperature ratio at the maximum ecological coefficient of performance conditions (ECOPmax) are always less than those of at the maximum ecological function ( E-dotmax ) and the maximum power output conditions ( W-dotmax ) leading to a design that requires less investment cost. It is also concluded that a design at ECOPmax conditions has the advantage of higher thermal efficiency and a lesser entropy generation rate, but at the cost of a slight power loss

  18. Análisis comparativo por ciclo de vida de tres tipos de luminarias empleadas en los interiores de edificios

    Directory of Open Access Journals (Sweden)

    Silverio Hernández Moreno

    2015-01-01

    Full Text Available Este trabajo consiste en la realización de un análisis comparativo por ciclo de vida entre tres tipos de luminarias usadas comúnmente en la actualidad en proyectos arquitectónicos y de iluminación artificial para interiores de edificios; comparando sus impactos ambientales para conocer cómo contribuyen de manera cuantitativa al calentamiento global principalmente por emisiones de CO2 a la atmósfera. El análisis se hizo a través de la información derivada de un Software de simulación del ciclo de vida de productos (GaBi®, usando particularmente la metodología llamada Evaluación por Ciclo de Vida (ECV que se enfoca principalmente en evaluar los impactos ambientales asociados a un producto a través de toda su vida útil, en concordancia con la norma técnica internacional ISO 14040 (referente a la metodología de Análisis por Ciclo de Vida. Los resultados muestran que el consumo eléctrico de la incandescente fue de 5.55 veces más que la luminaria fluorescente y 8.10 veces más que la de LED; la producción, uso y disposición final de la luminaria incandescente (49,334.4 CO2e en el ejemplo del presente estudio, contribuye al calentamiento global 29.87 veces más que la fluorescente (1,651.2 Kg. CO2e y 146.82 veces más que la de LED (336 Kg. CO2e. Se concluye que la luminaria LED es la mejor opción tomando en consideración todo el ciclo de vida completo del producto incluyendo el costo. Por otro lado, si solamente se valorara la fase de producción, la mejor opción sería la incandescente, pero por supuesto que sería un parámetro muy limitado porque se deben tomar en cuenta todas las fases del ciclo de vida incluyendo el análisis de costo por cada fase (de producción; de uso y mantenimiento y de fin de vida útil y disposición final. Respecto a la luminaria fluorescente podría ser la mejor opción ya que existe una amplia gama de productos en donde varian significativamente los precios y podría ser una buena opci

  19. Thermodynamic analysis of a Brayton cycle and Rankine cycle arranged in series exploiting the cold exergy of LNG (liquefied natural gas)

    International Nuclear Information System (INIS)

    The LNG (liquefied natural gas) regasification process is a source of cold exergy capable of being exploited to improve the efficiency of energy conversion. This paper presents a novel power plant consisting of a combination of a CBC (closed Brayton cycle) with a SRC (steam Rankine cycle), arranged in series with regard to the power source, while exploiting the cold exergy available in the regasification process of LNG. The power plant is fuelled by a combustion system of natural gas where the flue gases firstly yield heat to the CBC, then to the SRC and finally to the combustion air by means of a heat recovery process. The LNG cold exergy is exploited to cool the He used in the CBC to cryogenic temperatures at the compressor inlet as well as for generating electric power through direct expansion. The power plant is thermodynamically modelled and simulated using EES (Engineering Equation Solver). An energy and exergy analysis is carried out to evaluate the effect of some key parameters on the efficiency such as the temperature at the compressor inlet, the compression ratio, the temperature at the CBC turbine inlet and the LNG pressure during the regasification process. The outcome is a high efficiency power plant. - Highlights: • A closed Brayton cycle and a steam Rankine cycle arranged in series. • Exploitation of LNG cold exergy to increase power plant efficiency. • Thermodynamic analysis to evaluate the effect of the key parameters on the efficiency. • Energy and exergy efficiency of the power plant is respectively 56.72% and 55.09%. • The exergy available in the LNG represents 20.34% of the fuel exergy

  20. Análisis de contenidos de ecosistemas y ciclos geoquímicos en los manuales portugueses

    Directory of Open Access Journals (Sweden)

    Rosa Branca Cameira TRACANA

    2015-03-01

    Full Text Available Son muchos los estudios, en los últimos tiempos, sobre el tema Ecosistemas y ciclos geoquímicos. Pretendemos analizar la transposición didáctica del tema Ecosistemas y ciclos geoquímicos, en los manuales escolares, en el sistema de enseñanza portugués. Fueron analizados manuales de ciencias naturales, ciencia de la naturaleza, biología, geología y geografía, en el sistema educativo portugués y aun estudios sociales, química, biología, ciencias naturales, geología, geografía y ecología. En lo que se refiere a los manuales, constatamos que los del Tiempo I (1991-2000 se presentan más desarrollados en la presentación de los temas cuando se comparan con los del Tiempo II (2000-2006. En el tema Ecosistemas y ciclos geoquímicos, el abordaje de los manuales es esencialmente ecocéntrico. Sin embargo, nuestros resultados llevan a cuestionar la calidad de los manuales al respecto de este tema, porque no sólo es necesario tratarlo de modo más profundo, sino también se deben incluir en los manuales las competencias en educación ambiental para así poder transmitirlas a las generaciones futuras, y de este modo contribuir a una mejora de la calidad de vida en la Tierra.

  1. Explorando la Geometría en el segundo curso del primer ciclo de educación Primaria

    OpenAIRE

    Sedó-Beneyto, Marta

    2016-01-01

    El objetivo general de este trabajo fue crear una propuesta de actividades lúdicas con la finalidad de mejorar el razonamiento geométrico de alumnos de segundo curso de primer ciclo de la etapa Primaria mediante proyectos, talleres y juegos contextualizados en su vida cotidiana. La mayoría de estas actividades fomentan la resolución de problemas para favorecer el desarrollo del pensamiento matemático y, más concretamente, del razonamiento geométrico del niño, potenciando la motivación, la coo...

  2. El desarrollo del lenguaje en el segundo ciclo de educación infantil: propuesta didáctica

    OpenAIRE

    Cea Pérez de, María Elena

    2014-01-01

    El trabajo que se presenta a continuación se basa en la importancia que tiene el lenguaje, tanto oral como escrito, en el segundo ciclo de educación infantil, ya que a través de su utilización los niños serán capaces de expresar sus intereses, emociones, sentimientos, etc. y comunicarse con ellos mismos y con las personas de su entorno, para lograr integrarse en la sociedad en la que viven. Una vez expuesto el desarrollo del lenguaje, propongo una unidad didáctica que puede llevarse a cab...

  3. Las interacciones ciencia, tecnología y sociedad en los ciclos formativos de sistemas eléctricos.

    OpenAIRE

    Ríos Tarazona, Emilio

    2004-01-01

    RESUMEN Se estudian e investigan las concepciones de los alumnos de Formación Profesional de Ciclos Superiores sobre las relaciones entre Ciencia, Tecnología y Sociedad (CTS), y el provecho didáctico que la realización de actividades que tratan esas interacciones puede introducir para mejorar dichas concepciones, las actitudes y el interés de los alumnos hacía la Ciencia y la Tecnología. El problema se puede plantear del siguiente modo: 1. ¿Qué concepciones poseen los alumnos de Formaci...

  4. Regulación biótica del ciclo hidrológico en múltiples escalas

    OpenAIRE

    Salazar Villegas, Juan Fernando

    2011-01-01

    El papel de la biota en el funcionamiento del sistema terrestre ha sido motivo de un amplio debate científico. No se discute la existencia de tal papel sino su entendimiento a profundidad y sus implicaciones. En este contexto se encuentra la idea de la regulación del medio ambiente por parte de la biota, o regulación biótica del medio ambiente; y enmarcada por esta idea se formula la pregunta que sirve como punto de partida para la presente tesis: ¿El ciclo hidrológico es regulado (no sólo af...

  5. Imagens da diversidade intralinguística no 1º ciclo do ensino básico

    OpenAIRE

    Dias, Jacinta Raquel Bondoso

    2007-01-01

    Com este estudo pretende-se diagnosticar e descrever as imagens da diversidade intralinguística, veiculadas por alunos do 4º ano do 1º Ciclo do Ensino Básico, de uma escola de Lisboa, no ano lectivo de 2005/2006. O enquadramento teórico encontra-se dividido em duas partes. Na primeira, é focado o aspecto da variação linguística do português europeu (PE) utilizado em Portugal continental e insular, tendo em conta que todas as formas que a língua assume, na sua variação, têm o...

  6. Interagir e experimentar para aprender Física: desenvolvimento de um projecto com professores e alunos do 1º ciclo

    OpenAIRE

    Afonso, Isabel Maria Rosa, 1966-

    2003-01-01

    Dissertação de Mestrado, Física para Ensino, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2003 A educação científica e, concretamente, o trabalho experimental são vectores que aparecem claramente enfatizados no Programa do 1° Ciclo. Neste contexto, delineou-se o presente estudo com as seguintes finalidades: avaliar as concepções e práticas dos professores em termos do ensino da Física; avaliar os eleitos de um programa de formação que tinha em vista implementar ...

  7. Un marco de trabajo para analizar y mejorar la calidad de datos dentro de su ciclo de vida

    OpenAIRE

    Domingo, Gonzalo; Buccella, Agustina; Cechich, Alejandra

    2007-01-01

    En la actualidad pocas empresas en la Argentina tienen en cuenta a la calidad de datos como requisito fundamental en todo desarrollo, implementación y uso del sistema. Es muy común que al momento de diseñar la aplicación, la calidad de datos sea muchas veces obviada y no exista una metodología o técnicas para su análisis. En este trabajo se propone una metodología orientada a pensar los sistemas desde la óptica de la calidad de los datos durante todo el ciclo de vida de un desarrollo de softw...

  8. Conceções dos alunos do 1.º Ciclo do Ensino Básico sobre o sistema digestivo

    OpenAIRE

    Moreira, Dalila; Almeida, Liliana; Lopes, Mónica; Veiga, Vânia; Cavadas, Bento

    2012-01-01

    Este estudo exploratório teve como objetivo determinar os conhecimentos dos alunos do 1º Ciclo do Ensino Básico (1.º CEB) sobre o sistema digestivo. Usou-se uma adaptação do método seguido por Dantas (2006). O instrumento de recolha de dados utilizado foi o desenho. Solicitou-se a 69 alunos (37 raparigas e 32 rapazes) do 4.º ano, de quatro escolas do distrito de Santarém, que elaborassem um desenho sobre a constituição do aparelho digestivo humano. Os alunos fizeram os desenhos em sala de aul...

  9. Análisis de recursos digitales de Matemáticas para el primer ciclo de la ESO

    OpenAIRE

    Fraile-Bravo, María

    2012-01-01

    Este trabajo tiene la intención de crear un lugar dónde se recopilen recursos didácticos de matemáticas para el primer ciclo de la ESO, por el momento, con el propósito de seleccionar y recomendar los más adecuados para cada unidad o tema que se trabaja en esos dos cursos escolares. Existen muchas páginas en la red que contienen catálogos de recursos educativos, quizás demasiadas. Lo que este proyecto intenta aportar es que los recursos didácticos se presenten clasificados segú...

  10. La importancia del ciclo de caja y cálculo del capital de trabajo en la gerencia PYME

    OpenAIRE

    Jorge Iván Jiménez Sánchez; Farley Saray Rojas Restrepo; Heidy Julieth Ospina Galvis

    2014-01-01

     El artículo aborda las finanzas en la pyme moderna, la cual necesita de un gerente dinámico y hábil en la gestión administrativa, la información contable y las finanzas, con conocimiento de los días necesarios para cubrir el ciclo de caja y el capital que se requiere para operar a corto plazo, calculo necesario para determinar si va a alcanzar el dinero o si va a necesitar financiación y su valor exacto. Las cifras de fracaso de las pymes en América Latina son abrumadoras, ochenta por ciento...

  11. El ciclo vital revisado: las vidas de las mujeres mayores a la luz de los cambios sociales

    OpenAIRE

    Anna Freixas Farré; Bárbara Luque; Amalia Reina

    2012-01-01

    El aumento de la esperanza de vida ha revolucionado la explicación del ciclo vital humano. En el caso de las mujeres podemos identificar en el envejecer elementos diferenciales que tienen su origen en los cambios sociales de los últimos cincuenta años. Las características de la vida de las mujeres y su gran variabilidad interindividual hacen difícil el análisis de su experiencia en términos de las etapas evolutivas clásicas. Las mujeres mayores de los próximos veinte años, beneficiarias de la...

  12. Programa de modificación de conducta escolar (Educación Infantil y Primer Ciclo de Primaria)

    OpenAIRE

    De la Torre Ramírez, Carmelo

    2003-01-01

    Este artículo describe paso a paso la aplicación práctica de un programa completo de modificación de conducta escolar. Dicho programa pretende dar respuesta a una demanda concreta, la necesidad que presentan los docentes de solventar adecuadamente los problemas disruptivos y de convivencia que afloran en el aula. Se trata de un instrumento válido para ser aplicado principalmente en Educación Infantil y en el primer ciclo de la Educación Primaria

  13. Sincronías entre ciclos educativos, métodos pedagógicos y arquitecturas escolares

    OpenAIRE

    Martínez-Medina, Andrés; Oliva Meyer, Justo; Oliver, Jose L.

    2015-01-01

    I.- Enseñanza, pedagogía y arquitectura escolar. ¿Existe alguna relación entre ciclos de enseñanza, metodologías docentes y construcciones escolares? Esta parece ser la obsesión que ha guiado a los expertos de estos tres frentes en el siglo XX con el fin de definir la concreción física de los lugares para la transmisión de conocimientos y la formación de los alumnos. Y los tres frentes han ido cambiando: de la docencia informativa y dirigida a la formativa y participativa, del aprendizaje imp...

  14. Dificultades de aprendizaje de la geometría por parte de alumnos del primer ciclo de la ESO

    OpenAIRE

    Roca Cuffí, Marta

    2014-01-01

    El objetivo principal de este trabajo es investigar qué dificultades se encuentran los alumnos del primer ciclo de la ESO en el aprendizaje de la geometría, y cómo se puede incidir para ayudarlos en la superación de estas dificultades. Nuestro análisis del aprendizaje de la geometría se centra en tres aspectos (siguiendo el documento “Pensamiento Geométrico y Tecnologías Computacionales” del Ministerio de Educación Nacional de la República de Colombia): visualización, justifica...

  15. Sistema de almacenamiento de energía eléctrica en central de ciclo combinado

    OpenAIRE

    Saez Muñiz, Javier

    2016-01-01

    El presente Proyecto Final de Carrera estudia la implantación de un sistema de almacenamiento de energía eléctrica, adecuado para la instalación en una Central Eléctrica de Ciclo Combinado. Así mismo, su estructura podrá ser aplicable a otros tipos de centrales eléctricas, industrias, o instalaciones con mínimas modificaciones. El objeto incluye el estudio, cálculo y diseño del sistema de almacenamiento de energía, evaluando diferentes tipos de tecnologías existentes en la actu...

  16. El ciclo global del carbono y sus consecuencias en la fotosíntesis en el Altiplano boliviano

    OpenAIRE

    Saugier, B.; Pontailler, J.Y.

    2006-01-01

    El ciclo global del carbono se describe tomando en cuenta los intercambios entre la atmósfera y la biosfera continental, así como las modificaciones causadas por las actividades humanas: deposiciones nitrogenadas, aumento del CO2 atmosférico y el calentamiento climático inducido. Estos cambios globales tienen como consecuencia un aumento de producción vegetal y un almacenamiento de carbono en la biomasa de los árboles y en la materia orgánica del suelo. Como todos los ecosistemas terrestres, ...

  17. Proceso de ingeniería de software para el desarrollo del ciclo de vida de un objeto de aprendizaje

    OpenAIRE

    Rodríguez Rodríguez, Verónica

    2007-01-01

    Los Objetos de Aprendizaje han permitido plantear una nueva forma de desarrollo de material educativo, lo cual implica nuevas metodologías para la creación de los mismos. Para que se pueda establecer metodológicamente de manera completa el ciclo de vida de un Objeto de Aprendizaje es necesario definir un proceso de Ingeniería de Software y, además, determinar la secuencia completa de etapas que se presentan en un Objeto de Aprendizaje durante su diseño y desarrollo hasta su ...

  18. La enseñanza de estrategias de pensamiento en segundo ciclo de educación primaria

    OpenAIRE

    Choppi, María Marcela

    2013-01-01

    El motivo de éste trabajo surge a partir de la lectura del Diseño Curricular y el fundamento de su reforma que hace referencia a la centralidad de la enseñanza. Ésta lectura despertó la necesidad de averiguar si en los segundos ciclos de escuelas primarias, existen docentes que desarrollan estrategias de pensamiento en sus aulas. El objetivo central consistió en determinar la importancia que dichos docentes le otorgan a la enseñanza de estrategias de pensamiento. A tal efecto se confecc...

  19. El suelo, un sistema organizado que sustenta la vida terrestre, una propuesta de aula para ciclo I

    OpenAIRE

    Ramírez Mora, Yenny Patricia

    2012-01-01

    El siguiente trabajo tiene como objetivo diseñar una propuesta de aula donde se integren conceptualmente la estructura, y los procesos: físicos, químicos, biológicos y sociales, que inciden en el desarrollo y protección del suelo, con el fin de lograr un aprendizaje significativo, el desarrollo de habilidades de pensamiento y una conciencia del cuidado de éste en los estudiantes del ciclo I, del colegio Gerardo Molina Ramírez IED. Se realizó una prueba diagnóstica con el fin de identificar la...

  20. Asimetrías en la demanda por trabajo en Colombia: el papel del ciclo económico

    OpenAIRE

    Jorge Andrés Tamayo Castaño

    2012-01-01

    Este trabajo tiene como objetivo estimar las elasticidades de demanda de empleo moderno total y no calificado, haciendo énfasis en las asimetrías presentes en las distintas fases del ciclo económico colombiano. Para tal fin, se estiman modelos MS-VAR(p) siguiendo la metodología propuesta por Krolzig (1997) y Clements y Krolzig (2003). Los resultados confirman la existencia de dichas asimetrías en las demandas por empleo moderno total y no calificado, las cuales varían dependiendo del comporta...

  1. Autoperceções, contexto familiar e aspirações vocacionais de alunos do 2º ciclo

    OpenAIRE

    Paulino, Diana Sofia Rodrigues

    2013-01-01

    Tendo como base teórica as perspetivas desenvolvimentistas de Super (1995) e Gottfredson (1981,2005) e a sociocognitiva de Lent, Brown e Hackett (1994,2002), a presente investigação tem como objetivo estudar as aspirações vocacionais de adolescentes do 2º ciclo e as suas relações com as autoperceções e com variáveis do contexto familiar (NSE e aspirações parentais). A amostra inclui 146 participantes de duas escolas do distrito de Lisboa, onde foram aplicados o Questionário de Aspirações d...

  2. Flotabilidad y similitud del nado de Manta birostris(Elasmobranchii: Myliobatidae con el ciclo de vuelo de Columba livia(Aves: Columbidae

    Directory of Open Access Journals (Sweden)

    Iván Meza Vélez

    2013-12-01

    Full Text Available Se analizó la física de la flotación en la mantarraya Manta birostrisy se comparó el nado con el ciclo de vuelo de la paloma doméstica Columba livia, con la finalidad de encontrar similitudes y diferencias en las locomociones y las leyes físicas que intervienen. Se demostró que uno de los dos ciclos de nado estudiados de esta especie posee tres de las cuatro fases principales del ciclo de vuelo de la paloma doméstica. También se demostró un “efecto paracaídas” en M. birostris, el cual le ofrece una ventaja en su locomoción. Adicionalmente, se describió cómo el concepto físico de torque se aplica al giro de esta especie.

  3. Modelado de un ciclo de potencia de CO2 supercrítico para reactores de fusión utilizando RELAP5-3D

    OpenAIRE

    Batet Miracle, Lluís; Álvarez Fernández, Josep Maria; Mas de les Valls Ortiz, Elisabet; Pérez, Marina; Martínez Quiroga, Víctor; Reventós Puigjaner, Francesc Josep; Sedano Miguel, Luis Angel

    2013-01-01

    En el marco del programa español de Tecnología de Fusión TECNO_FUS se ha avanzado en la definición de sistemas para DEMO, entre ellos las unidades reproductoras de tritio y el ciclo de potencia. Para las primeras, se ha propuesto un diseño modular a doble refrigerante (PbLi-He). Para la conversión de potencia térmica a eléctrica se han investigado ciclos de CO2 supercrítico. Mediante el código de sistema RELAP5-3D© se ha simulado un ciclo de potencia de CO2 supercrítico con recompresión. E...

  4. Psicología del desarrollo y Psicología del ciclo vital. Un intento de integración a debate

    OpenAIRE

    Perinat, Adolfo

    1981-01-01

    En la década de 1970 ha surgido con ímpetu el nuevo dominio de la psicología del ciclo vital (lqe-span developmental psychology). Uno de sus postulados básicos es que el hombre continúa desarrollándose y cambiando en el decurso de la vida. En este artículo se discute, en primer lugar, hasta qué punto es lícito extrapolar el concepto de desarrollo a todo el ciclo vital humano. En segundo lugar se valora la crítica que la psicología del ciclo vital hace de la idea de cambio asociado a la edad, ...

  5. Diseño de un ciclo de producción de frío para uso de climatización movido por motor Stirling

    OpenAIRE

    González Saucedo, Francisco José

    2016-01-01

    El objetivo del presente Trabajo Fin de Grado se basa en la integración de un motor de ciclo Stirling en un sistema de refrigeración por compresión mecánica. Se ha llevado a cabo el diseño de un sistema de refrigeración por compresión mecánica, incluyendo el motor de ciclo Stirling y el tipo de fuente de calor externa para su funcionamiento, y se ha comparado con un sistema de refrigeración por absorción y un sistema de bomba de calor por ciclo de compresión a gas, operando bajo las misma...

  6. El estado de ánimo de la mujer durante su ciclo reproductivo

    Directory of Open Access Journals (Sweden)

    María Raquel Huerta Franco

    2000-01-01

    Full Text Available Los frecuentes hallazgos de las investigaciones internacionales y en la población mexicana en el campo de la psiquiatría, confirman repetidamente que los trastornos afectivos de la mujer sobrepasan en número a los reportados en el hombre. La mujer, por el solo hecho de pertenecer al sexo femenino, tiene más riesgo de experimentar con mayor frecuencia síntomas de depresión y ansiedad, lo que sólo puede ser superado por los antecedentes familiares de alteraciones afectivas. A pesar de que hay una clara asociación en el sexo femenino con la mayor frecuencia con que se presenta la ansiedad, los cambios en el comportamiento y la baja autoestima, la causa no se ha definido completamente. Las razones son complejas y se dispersan debido a las limitaciones metodológicas que impiden estudiar los factores que hacen que la mujer sea más susceptible a presentar estos problemas. Actualmente diversas hipótesis intentan explicar las causas, la incidencia y la prevalencia de los problemas afectivos desde varias perspectivas (biológica, psicológica y sociocultural. En este artículo se presentan los resultados de los estudios en la población femenina mexicana y de la de diversas partes del mundo. Se dan datos sobre la frecuencia y el grado de intensidad de los síntomas de depresión, ansiedad, estrés, no específicos de la depresión, premenstruales, y caraterísticos de la autoestima de la mujer durante las diferentes etapas de su ciclo reproductivo. Se comparan los resultados de algunos estudios en hombres y mujeres. Además, se discute el efecto de los factores biológicos, como las hormonas gonadales y sus metabolitos, en la modulación de los neurotrasmisores y sus relaciones con las alteraciones afectivas. También se tratan otros factores, como los ambientales y los del estilo de vida propia de la mujer.

  7. PRODUCCIÓN DE FITOMASA POR Coffea canephora Pierre ex Froehner EN DOS CICLOS PRODUCTIVOS

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    Carlos Bustamante González

    2015-01-01

    Full Text Available En áreas de la Estación Central de Investigaciones de Café y Cacao ubicadas en La Mandarina, municipio Tercer Frente, provincia Santiago de Cuba y La Alcarraza, municipio Sagua de Tánamo, provincia Holguín, se evaluó la producción de biomasa de Coffea canephora Pierre ex Froehner var. Robusta desde la plantación hasta el cuarto año en ambas localidades y luego de la poda baja y hasta el cuarto año en la Alcarraza. Los cafetos fueron plantados a 3 x 1,5 m en suelos Pardos bajo sombra de Samanea saman Jerr en la primera localidad y Leucaena leucocephala Lam de Wit en la segunda. La fitomasa se separó en hojas, ramas, tallos, frutos y raíces. A partir de los 24 meses y al año después de la poda se recolectaron mensualmente las hojas del cafeto caídas. Para el estudio del sistema radical se extrajeron bloques de suelo de 25 x 25 x 25 cm, en un área formada por 1,5 m (distancia hacia la calle y 0,75 m (entre plantas, en todos los casos centrado en relación con la planta y hasta un metro de profundidad. El volumen del suelo extraído representó ¼ del volumen ocupado por la planta. Se determinó la masa seca de cada órgano. La producción de fitomasa alcanzó valores de 25 toneladas de masa seca ha -1 independientemente de la fase de la plantación. Hasta el cuarto año el sistema radical predominó en la fitomasa, seguido de las hojas y luego los tallos. La participación de los frutos se incrementó en la etapa de cosecha y al concluir el experimento los cafetos habían destinado para su formación entre el 16-20 % de la masa seca total, independientemente del ciclo de desarrollo

  8. Acerca del ciclo evolutivo del Trypanosoma (Schizotrypanum cruzi Chagas 1909, en sus fases tisular y hematica

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    Cecilio Romaña

    1956-06-01

    Full Text Available El autor pasa en revista los trabajos publicados sobre el ciclo evolutivo del Trypanosoma (S. cruzi en el huésped vertebrado, desde el descubrimiento de la enfermedad hasta nuestros días. Luego analiza las ideas de los autores modernos, fundadas en gran parte en las observaciones que ya en 1914 realizaron MAYER y ROCHA LIMA de las cuales participan actualmente ROMAÑA y MEYER, ELKELES y WOOD. Finalmente expressa que a partir de los tripanosomas infectantes los parásitos que penetram en el protoplasma celular pueden seguir dos mecanismos en su evolución hacia cuerpos leishmanioides: 1.º Por "regresión fusiforme" y 2.º por "regresión orbicular"; llegados a la forma leishmanioide los parásitos se multiplican por división binaria, una vez lleno el protoplasma celular, siguen un processo inverso de transformación hacia tripanosoma que puede seguir igualmente dos mecanismos diversos: 1. "progresión fusiforme" y 2.º "progresión orbicular". Estos diversos mecanismos de transformación están esquematizados en la fig. N.º 1 del trabajo.The author reviews published works about the evolutive cycle of the Trypanosoma cruzi in the vertebrate host, from the discovery of the disease to our days. Then, he analyzes the ideas of the modern authors who based themselves on the observations made formerly, in 1914, by MAYER & ROCHA LIMA, ideas that ROMAÑA and MEYER, ELKELES and WOOD agree at the present time. Last, he states that, from the infective trypanosomas, the parasites which enter the cellular protoplasma may follow two systems to perform their evolution up to leishmanioid bodies: 1.] by fusiform regression, 2.º by an orbicular regression. Once the parasites reach the leishmanioid forms, they multiply by binary division. When the celular protoplasm is filled up with the parasites, these follow an inverted transformation up to trypanosoma state, following also two systems; similar to the repression 1.º a fusiform progression, 2.º an

  9. Treino do oral formal : entrevista e exposição no 3º ciclo do ensino básico

    OpenAIRE

    Silva, Maria de Fátima Freitas da

    2008-01-01

    Falar de competências linguísticas para o 3º ciclo do Ensino Básico é convocar obrigatoriamente a competÊncia de compreensão e expressão oral, na dupla vertente do ouvir-falar, dada a relação intrínseca que se estabelece entre estas duas capacidades. No domínio da oralidade, defende-se, para este ciclo de ensino, a promoção do treino e aprendizagem da competência comunicativa verbal oral, mormente dos usos formais e, aprendizagem da competência comunicativa verbal oral, mormente dos usos form...

  10. Evaluación medioambiental de productos de hormigón mediante el análisis de ciclo de vida.

    OpenAIRE

    Carrascón Ortiz, Sergio; Aguado de Cea, Antonio; Josa Garcia-Tornel, Alejandro

    2007-01-01

    El Análisis de Ciclo de Vida (ACV) es una herramienta básica para evaluar cuantitativamente el impacto medioambiental de un producto. Se debe considerar el ciclo de vida completo, debido a que los impactos se pueden producir en cualquier momento de la vida de este producto (desde el momento de la obtención de las materias primas hasta su deposición definitiva o final de su vida útil). Los elementos básicos de un ACV son un inventario (ICV) de aspectos medioambientales (entradas y sal...

  11. CICLO BIOLÓGICO Y ANÁLISIS DE RIESGO DE Leptoglossus zonatus DALLAS (HETEROPTERA: COREIDAE) PARA EL SORGO EN EL ESTADO DE MORELOS

    OpenAIRE

    Tepole García, Rosa Elba

    2015-01-01

    Leptoglossus zonatus es una especie generalista, a pesar de su importancia económica en sorgo, nogal y piñón mexicano, en México no hay estudios de su ciclo biológico ni métodos de prevención. Por lo que en el presente trabajo se estudió la supervivencia de L. zonatus alimentadas con cuatro hospederas, para el establecimiento de una cría, su ciclo de vida en cinco condiciones y el riesgo de su incidencia para el cultivo de sorgo en el estado de Morelos. Se alimentó con maíz (elote), frijol (e...

  12. Dificultades en el aprendizaje de la lectoescritura en el primer ciclo de educación primaria. Intervención en el aula

    OpenAIRE

    Martín Gómez, María Cristina

    2013-01-01

    El presente trabajo parte con la idea de ser una guía útil para los maestros de primaria sobre los trastornos de aprendizaje de la lectura y escritura que se dan en el primer ciclo. En muchas ocasiones el maestro del primer ciclo se ve sin la formación necesaria sobre este tema y sin los recursos necesarios para prevenir y corregir los errores que este proceso de aprendizaje implican, bien como parte del mismo o bien porque aparecen los primeros síntomas de diversos tipos de dificultades que ...

  13. A Representação do ciclo vital dos documentos: uma discussão sob a ótica da gestão de documentos

    OpenAIRE

    Nilcéia Lage Medeiros; Cléia Gomes Amaral

    2010-01-01

    Este artigo tem por objetivo suscitar, sob a ótica da gestão de documentos, questionamentos acerca das concepções que fundamentam as diferentes fases que constituem o ciclo vital dos documentos e a teoria das três idades. Assim, são apresentadas as representações das três fases do arquivamento por que passam os documentos (corrente, intermediária e permanente) e a do ciclo vital de documentos proposta por James Rhoads (1989) (nascimento, vida ativa/ produtiva, morte ou destruição, e reencarna...

  14. Primeros datos sobre el desarrollo del ciclo de vida del díptero de importancia forense Sarcophaga cultellata Pandellé, 1896 (Sarcophagidae)

    OpenAIRE

    M.I. Arnaldos Sanabria; B. Torres Tomás; M.D. García García

    2013-01-01

    Se aportan los primeros datos conocidos sobre el desarrollo del ciclo vital del díptero de importancia forense Sarcophaga cultellata Pandellé, 1896, en condiciones controladas. En condiciones de 25ºC y 50% humedad relativa la duración media del desarrollo larvario fue de 148,8±10,73 h y la duración media del ciclo vital completo, hasta la aparición de los primeros adultos, de 330±12 h. A efectos forenses, la duración del desarrollo larvario, entendido hasta la completa pupación, es de 6,2 día...

  15. Consumo de Servicios y Ciclo Vital: Un análisis de los hogares españoles con datos de corte transversal

    OpenAIRE

    Jose A. Camacho Ballesta; Manuel Hernández Peinado

    2006-01-01

    En las últimas décadas, como consecuencia del avance hacia una sociedad cada día más consumista, simultáneamente ha aumentado el interés por parte de los economistas acerca de las relaciones entre consumo y la renta dando lugar a múltiples teorías e interpretaciones. Así, el ciclo vital ha pasado a ser uno de los principales factores explicativos del comportamiento del gasto de las familias. Este trabajo aborda la influencia del ciclo vital familiar sobre las pautas de consumo de servicios y ...

  16. Satisfação conjugal, amor romântico, coping diádico e sensibilidade olfativa ao longo do ciclo vital do casal: estudo comparativo

    OpenAIRE

    Vilas, Lília Solangue Rodrigues

    2015-01-01

    A complexidade e paradoxalidade inerente à díade conjugal dificultam a sua investigação ao longo do ciclo vital do casal. A fim de contribuir para o conhecimento em torno desta temática, o presente estudo recorreu a uma amostra de 234 indivíduos casados portugueses com o objetivo geral de estudar a satisfação conjugal, o amor romântico, o coping diádico e a sensibilidade olfativa ao longo do ciclo vital do casal (fase da fusão, autonomia e empatia), de acordo com a teoria de Franck-Lynch (198...

  17. Control del ciclo celular y fisiopatología vascular: Papel de los supresores de crecimiento p27Kip1 y p53.

    OpenAIRE

    Silvia M. Sanz-González

    2006-01-01

    RESUMEN El ciclo celular en mamíferos está regulado positivamente por holoenzimas formadas por una subunidad reguladora (denominada ciclina) y quinasas dependientes de ciclinas (CDK). Estos complejos ciclina/CDK se activan e inhiben secuencialmente en las diferentes fases del ciclo celular. Las proteínas inhibidoras de las CDKs, CKIs, constituyen una familia importante de supresores de cecimiento celular. La proteína p27Kip1 es una CKI de la familia CIP/KIP que actúa como inhibidor univers...

  18. Ciclo celular y neurodegeneración: implicación de la E3 ubitiquina ligasa APC/C-Cdh1en la excitotoxicidad

    OpenAIRE

    Maestre Ferrín, Carolina

    2009-01-01

    [ES]La división celular es un proceso esencial que permite el desarrollo de un individuo pluricelular adulto a partir de una única célula, así como la regeneración de los tejidos, que necesitan el reemplazo de las células que van perdiendo.Durante el ciclo celular, todos los componentes de la célula madre deben duplicarse y repartirse entre las células hijas. El DNA ha de replicarse una única vez en cada ciclo y de forma exacta, y las cromátidas hermanas producidas han de segregarse a cada un...

  19. Consumo de servicios y ciclo vital : un análisis de los hogares españoles con datos de corte transversal

    OpenAIRE

    Camacho Ballesta, José Antonio; Manuel HERNÁNDEZ PEINADO

    2006-01-01

    En las últimas décadas, como consecuencia del avance hacia una sociedad más cada día más consumista, simultáneamente ha aumentado el interés por parte de los economistas acerca de las relaciones entre consumo y la renta dando lugar a múltiples teorías e interpretaciones. Así, el ciclo vital ha pasado a ser uno de los principales factores explicativos del comportamiento del gasto de las familias. Este trabajo aborda la influencia del ciclo vital familiar sobre las pautas de consumo de servi...

  20. Análisis del ciclo de vida comparativo de una mermelada de naranja ecológica y no ecológica

    OpenAIRE

    Pérez Gutiérrez, Francisco Alberto

    2013-01-01

    En este proyecto pretendemos realizar el Análisis del Ciclo de Vida (ACV) comparativo de dos productos. Este término también podremos encontrarlo en la variada bibliografía con las siglas inglesas LCA (Life Cycle Assessment.) Hasta el momento actual se han realizado múltiples ACV sobre distintos productos industriales: por ejemplo el Análisis del Ciclo de Vida de un disco de freno ventilado (Montaña Vallinas, 2004) o el ACV comparativo entre una instalación de calefacción por suelo radiante y...

  1. Trabalho por turnos na indústria: alterações do ciclo sono-vigília e impacto no quotidiano, individual e social, dos trabalhadores

    OpenAIRE

    Alves, Bartolomeu Tiago Rasteiro

    2013-01-01

    Resumo O trabalho por turnos pode provocar dessincronizações dos ciclos biológicos endógenos, como o ciclo sono/vigília. Esta desorganização do ritmo circadiano do sono, assim como de outros ritmos biológicos, provocado pelo trabalho por turnos e noturno, podem levar a sérios comprometimentos das funções fisiológicas e psicológicas, afetando a qualidade de vida do trabalhador. Associando outros riscos inerentes à atividade profissional, como o ruído e a iluminação, poder-se-á culminar em c...

  2. Los estudios del tercer ciclo en el Departamento de Psicología de la Universidad de Huelva : reflexiones y propuestas de mejora

    OpenAIRE

    Aguaded Gómez, María Cinta; Castillo Fernández, Joaquina; Martín Cabrera, Margarita; Pulgarín Medina, María del Carmen; Sauci Muñoz, Dolores

    1999-01-01

    Este trabajo pretende analizar la situación actual de los estudios de Tercer Ciclo. Para ello, nos centraremos en una experiencia concreta como alumnas del programa de Doctorado del Departamento de Psicología de la Universidad de Huelva. “Investigación psicológica en el ámbito educativo”, durante el bienio 1995/1997. En primer lugar, revisaremos la normativa vigente en torno a los estudios de Tercer Ciclo de las Universidades españolas: marco legislativo, cursos y seminarios, elaboración d...

  3. Hacia la institucionalización de la medición del ciclo económico colombiano: una propuesta

    OpenAIRE

    Rodríguez, Jorge Armando

    2011-01-01

    Este artículo propone institucionalizar la medición del ciclo económico colombiano mediante la creación de un comité no partidista, cuyos miembros provendrían principalmente de las universidades públicas y privadas. Con el objeto de asegurar un grado importante de diversidad regional, un mínimo de miembros del comité provendría de lugares distintos a Bogotá. En adición a la tradicional medición del ciclo basada en el PIB, se propone instaurar una medición basada en el nivel de emp...

  4. Los claroscuros de la sincronización internacional de los ciclos económicos: evidencia sobre la manufactura de México

    OpenAIRE

    Pablo Mejía Reyes; Elías E. Gutiérrez Alva; José A. Pérez Díaz

    2006-01-01

    Se analiza la sincronización de las fluctuaciones cíclicas de la división manufacturera de México con el ciclo estadounidense. Se utiliza el enfoque tradicional de los ciclos de crecimiento para el periodo 1980-2004 en submuestras de cinco años que se desplazan en el tiempo, lo cual permite estudiar la evolución temporal del proceso. Los resultados sugieren que la sincronización se ha incrementado sustancialmente en el marco del TLCAN, pero ha sido heterogénea...

  5. Implementación de la reorganización curricular por ciclos (Caso: Colegio Técnico Tomás Rueda Vargas I.E.D.)

    OpenAIRE

    Niño Cerinza, Sonia

    2013-01-01

    Esta investigación constituye un estudio de caso en el que se busca realizar un balance de la implementación de la política de ciclos (RCC) en un Colegio Público de la ciudad de Bogotá, se abordó en la localidad cuarta de San Cristóbal el Colegio Técnico Tomás Rueda Vargas, por ser considerado desde la Secretaria de Educación, una de las propuestas exitosas en la implementación de la Reorganización Curricular por Ciclos. Lo que se persiguió principalmente en este ejercicio fue identificar los...

  6. La Arquitectura de Software en el Proceso de Desarrollo: Integrando MDA al Ciclo de Vida en Espiral

    Directory of Open Access Journals (Sweden)

    Valeria S. Meaurio

    2013-08-01

    Full Text Available En la actualidad el desarrollo de software debe enfrentarse a una serie de problemas, por ejemplo, la rapidez con que el software debe estar disponible para su uso, el alto grado de evolución de los sistemas actuales y el nivel de complejidad de los mismos, entre otros. Contar con un modelo de la arquitectura en etapas tempranas se hace evidente, puesto que anticiparnos a la especificación detallada del sistema nos permite contar con un modelo de alto nivel de la alternativa de solución a los requerimientos planteados, que en sucesivos refinamientos conducirán al producto final. En vistas de estos problemas la propuesta de la OMG arquitectura dirigida por modelos (Model Driven Architecture - MDA propone la construcción de software como la trasformación sucesiva de modelos, desde un alto nivel de abstracción hasta el nivel de implementación en una plataforma concreta. El objetivo del presente trabajo propone aplicar el modelo MDA dentro del ciclo de vida en espiral propuesto por Bohem a fin de establecer el impacto de la arquitectura de software en las distintas etapas de este ciclo de vida y como MDA minimiza el riesgo.

  7. Análisis del Comportamiento de un Ciclo Tipo Carnot Analysis of the Behavior of a Carnot Type Cycle

    Directory of Open Access Journals (Sweden)

    Delfino Ladino-Luna

    2010-01-01

    Full Text Available Se hace un análisis de las regiones de existencia de la función potencia de salida y función ecológica, que dan lugar a la forma de las respectivas eficiencias para un ciclo tipo Carnot, llamado ciclo endorreversible, a potencia de salida máxima y función ecológica máxima. Se muestra la importancia dichas regiones de existencia de estas funciones para diversos resultados de la literatura relacionada con la termodinámica de tiempos finitos. Se concluye que para modelar gráficamente el desempeño de una máquina térmica, es necesario hacer un análisis de las regiones de existencia de los parámetros importantes que describen el comportamiento de la maquina.An analysis of the regions of existence of power output and ecological function, that give the form of respective efficiencies for a Carnot type cycle, called endorreversible cycle, at maximum power output and at maximum ecological function is done. The importance of these regions of existence of these functions is shown, for different results from the literature on finite time thermodynamics. It is concluded that for graphically modeling the performance of a heat engine, it is necessary to perform an analysis of the regions of existence of the most important parameters that describe this behavior of the engine

  8. El ciclo de vida femenino en el saber biomédico: construyendo corporalidades para las mujeres de mediana edad

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    Ana Leticia Fitte

    2011-08-01

    Full Text Available En este trabajo se exploran tanto las nociones del climaterio y la menopausia, elaborados por el modelo biomédico, así como los presupuestos que lo estructuran. Para ello se toman, por un lado, como referente empírico, los relatos de médicos y médicas especialistas en ginecología que desempeñan su labor en consultorios privados de la ciudad de La Plata, Argentina y, por otro lado, la literatura disponible sobre el tema elaborada desde las ciencias sociales. El propósito de dicho análisis es identificar los criterios utilizados para segmentar el ciclo de vida femenino dentro del saber biomédico entendiendo que dichas conceptualizaciones han creado y legitimado un modelo hegemónico acerca de la corporalidad femenina y que las relaciones de género no están desvinculadas de un ciclo vital estandarizado para hombres y mujeres, dentro del cual derechos, obligaciones y posibles usos del cuerpo difieren de una edad a otra.

  9. 27 de febrero de 1989: 25 años de un ciclo de conmoción social

    Directory of Open Access Journals (Sweden)

    Luis J. González Oquendo

    2014-01-01

    Full Text Available El objetivo del presente trabajo es sistematizar elementos factuales y teóricos para desarrollar puntos de reflexión claves para el abordaje analítico de los sucesos del 27 de febrero y días subsiguientes [27F]. La parte corresponde a una descripción de los eventos asociados a todo el ciclo de protesta, tratando de delimitar diferentes etapas a lo largo del mismo utilizando dos criterios: el tipo de violencia y la naturaleza de actores involucrados. La segunda parte del trabajo considera a los diferentes tipos de explicación generadas para dar cuenta del 27F como ciclo de protesta: (a las tesis que se basan en factores sociales y psicosociales; b las tesis que sostienen la existencia de acción conspirativa. Finalmente, en la tercera parte se abordan las consecuencias que el 27F tuvo para el devenir de los procesos políticos venezolanos a partir de entonces.

  10. Visualização dos padrões de variação da taxa de mortalidade infantil no Rio Grande do Sul, Brasil: comparação entre as abordagens Bayesiana Empírica e Totalmente Bayesiana Patterns of variation in the infant mortality rate in Rio Grande do Sul State, Brazil: comparison of empirical Bayesian and fully Bayesian approaches

    Directory of Open Access Journals (Sweden)

    Sabrina Letícia Couto da Silva

    2011-07-01

    Full Text Available A mortalidade infantil é um sensível indicador de saúde. Conhecer o seu perfil geográfico auxilia na formulação de estratégias de saúde pública. O mapeamento de doenças tem por objetivo descrever a distribuição geográfica das taxas de mortalidade ou incidência de doenças por intermédio de mapas. Em razão da alta instabilidade das taxas brutas quando há pequenas áreas, utilizam-se os métodos de suavização bayesiana, que se valem de informações de toda a região ou da vizinhança para estimar as taxas. O artigo faz a comparação entre os métodos Bayesiano Empírico e Totalmente Bayesiano para as taxas de mortalidade infantil (dados acumulados de 2001 a 2004 no Rio Grande do Sul, Brasil. O trabalho aponta as vantagens do uso dos estimadores bayesianos na visualização espacial dos mapas. Os métodos Bayesianos Empíricos apresentaram resultados muito semelhantes aos dos métodos Totalmente Bayesianos e possuem a grande vantagem de ser de fácil utilização por profissionais da área de saúde, destacando igualmente os principais padrões espaciais da taxa de mortalidade no Rio Grande do Sul no período estudado.Infant mortality is considered a sensitive health indicator, and knowledge of its geographical profile is essential for formulating appropriate public health policies. Disease mapping aims to describe the geographical distribution of disease incidence and mortality rates. Due to the heavy instability of crude rates in small areas, methods involving Bayesian smoothing of rates are used, drawing on information for the whole area or neighborhood to estimate the event rate. The current study compares empirical Bayesian (EB and fully Bayesian (FB methods for infant mortality rates (accumulated data from 2001 to 2004 in Rio Grande do Sul State, Brazil. This study highlights the advantages of Bayesian estimators for viewing and interpreting maps. For the problem at hand, EB and FB methods showed quite similar results and

  11. Fluctuaciones estacionales y ciclos de vida de los anfípodos [crustacea : peracarida : amphipoda] del Estrecho de Gibraltar aplicaciones en acuicultura

    OpenAIRE

    Baeza-Rojano Pageo, Elena

    2013-01-01

    Esta memoria versa sobre las fluctuaciones naturales y los ciclos de vida bajo condiciones controladas de las especies de anfípodos más representativas del sur de la Península Ibérica, así como de sus posibles aplicaciones en la acuicultura. Los anfípodos

  12. La robótica como herramienta educativa para la introducción a la programación en centros de secundaria y ciclos formativos

    OpenAIRE

    BESER IRANZO, ISABEL

    2011-01-01

    Beser Iranzo, I. (2011). La robótica como herramienta educativa para la introducción a la programación en centros de secundaria y ciclos formativos. http://hdl.handle.net/10251/10949. Archivo delegado

  13. Núcleo central e periferia das representações sociais de ciclos de aprendizagem entre professores Centro y periferia de las representaciones sociales de ciclos de aprendizaje entre maestros Core and periphery of social representation cycles between learning teachers

    Directory of Open Access Journals (Sweden)

    Laêda Bezerra Machado

    2010-06-01

    Full Text Available Este artigo identifica as representações sociais de ciclos de aprendizagem entre professores de Recife e suas implicações práticas, demarcando a saliência e estrutura dessas representações. Participaram do estudo 103 professores. O procedimento de coleta utilizado foi a associação livre de palavras. Os dados foram processados pelo software EVOC, que oferece um gráfico com quatro quadrantes onde localizamos o provável núcleo central e sistema periférico da representação social. Os resultados apontam um discurso racionalizado, ou seja, a saliência dessa representação permite afirmar que os docentes, embora na prática critiquem e rechacem os ciclos de aprendizagem, nas suas representações revelam sintonia com a proposta da rede municipal. Sugerimos, portanto, estudos mais densos das práticas cotidianas desses docentes, para depreender aspectos das representações sociais que nos pareceram pouco revelados.El artículo identifica las representaciones sociales de los ciclos de aprendizaje entre los profesores de Recife y sus implicaciones prácticas, señalando la importancia y la estructura de estas representaciones. Los participantes fueron 103 docentes. El procedimiento de recolección utilizado fue la asociación libre de palabras. Los datos fueron procesados por software EVOC, que ofrece un gráfico con cuatro cuadrantes donde localizamos el probable núcleo central y sistema periférico de la representación social. Los resultados muestran un discurso racional, es decir, la importancia de esta representación permite afirmar que los profesores, aunque en la práctica critican y niegan los ciclos de aprendizaje, en sus representaciones muestran de acuerdo con la propuesta de la red municipal. Sugerimos, por lo tanto, los estudios más densos de las prácticas cotidianas de los profesores, para inferir aspectos de las representaciones sociales que nos parezcan poco revelados.This article identifies the social

  14. Ciclos de vida comparados de Aedes aegypti (Diptera, Culicidae do semiárido da Paraíba

    Directory of Open Access Journals (Sweden)

    Francisco P. de Castro Jr.

    2013-06-01

    Full Text Available O presente trabalho teve como objetivo comparar os ciclos de vida entre amostras de populações de Aedes aegypti (Linnaeus, 1762 coletadas em dez municípios localizados no semiárido paraibano. Os ciclos de vida foram estudados a uma temperatura de 26 ± 2ºC, umidade relativa de 60 ± 10% e fotofase de 12 horas. Diariamente foram avaliados os períodos de desenvolvimentos e as viabilidades das fases de ovo, larva e pupa, bem como a razão sexual, longevidade, tamanho e fecundidade dos adultos. Foi realizada uma análise de agrupamento, utilizando-se uma matriz de distância euclidiana através do método da média não-ponderada. As durações e viabilidades para as fases de ovo, larva e pupa apresentaram respectivamente, uma variação média de 3,7 a 4,7 dias e 82,8% a 97,7%, 9,1 a 10,8 dias e 91,2% a 99,2% e de 2,1 a 2,5 dias e 93,5% a 98,4%. O comprimento alar foi de 5,13 a 5,34 mm para as fêmeas e de 4,18 a 4,25 mm para os machos. A menor fecundidade (153,6 ovos/fêmea ocorreu na população de A. aegypti oriunda de Pedra Lavrada, enquanto que a maior fecundidade (310,6 ovos/fêmea foi constatada para A. aegypti de Campina Grande. A análise de agrupamento com base na similaridade dos dados biológicos revelou a formação de dois grandes grupos distintos, onde as populações de A. aegypti de Serra Branca e Cuité apresentam maior similaridade entre si. As diferenças de ciclos biológicos verificadas entre as populações de A. aegypti demonstra a capacidade dessa espécie de sofrer variações na sua biologia e se adaptar às diferentes condições ambientais, favorecendo a permanência deste inseto nessas áreas com aumento do risco de transmissão do vírus da dengue.

  15. Analysis of transient coolant void formation during a guillotine-type HX tube rupture event in the Star-LM system employing a supercritical CO2 Brayton cycle

    International Nuclear Information System (INIS)

    One proposed concept for the STAR-LM Lead Fast Reactor (LFR) incorporates a supercritical CO2 gas turbine Brayton cycle to achieve high cycle efficiency and reduced plant footprint. In this design, 100+% of core full power is transferred by natural circulation from the core, located at the bottom of the reactor vessel, to in-vessel heat exchangers (HXs) located at the top of the vessel in the annulus between the core shroud and vessel inner wall. Although this approach extremely simplifies the plant design, the presence of the HXs within the vessel raises concerns regarding the potential rupture of a HX tube that would initiate a high-pressure blowdown of CO2 into the lead coolant. The principal issue is to what extent, if any, is void entrained downwards with the coolant and then upwards through the core where adverse reactivity effects or degraded heat removal could result. To address this question, a scoping analysis of transient void formation during a guillotine-type HX tube rupture event in the STAR-LM employing a supercritical CO2 Brayton cycle has been performed. The void formation process is evaluated by solving a coupled set of ordinary differential equations describing: i) the supercritical CO2 blowdown, ii) bubble center-of-mass trajectory, iii) bubble growth rate, iv) bubble gas internal energy, and v) discrete bubble formation rate due to Taylor instability at the bubble/coolant interface. The results indicate that for thermal hydraulic conditions consistent with the current STAR-LM design, the peak blowdown rate from a single tube rupture is ∼ 2.5 kg/sec. The void formation process is dominated by large coherent gas bubbles that penetrate minimally downwards into the coolant due to the large coolant density. Rather, the gas pockets are predicted to periodically rise due to buoyancy and vent to the core cover gas region, as opposed to being swept downwards with the coolant. Moreover, the total CO2 fraction that is rendered in the form of discrete

  16. La integración en el ciclo superior y su continuación en el mundo laboral

    OpenAIRE

    Rosa RODRÍGUEZ ALONSO

    2009-01-01

    RESUMEN: En este artículo se pretende explicar de manera muy suscinta el trabajo que desarrolló el equipo de profesores del colegio Ntra. Sra. de Montserrat con la investigación «La Integración en el Ciclo Superior y su continuación en el mundo laboral». Esta idea surgió a partir de la puesta en marcha de un Proyecto de Innovación Educativa en el centro de EGB y FP (hoy en día reconvertido en Primaria y Secundaría) durante los cursos 1991-93. En primer lugar hacemos un estudio de los alumnos ...

  17. Influência do ciclo lunar na captura de morcegos Phyllostomidae Influence of moon cycle in phyllostomid bat capture

    OpenAIRE

    Carlos E. L. Esbérard

    2007-01-01

    A influência da luz da lua no padrão de atividade de morcegos já foi documentada em algumas espécies. Geralmente os morcegos reagem ao aumento da iluminação reduzindo o uso de espaços abertos e restringindo a atividade de forrageio ou a duração do período de atividade. Para estabelecer a influência do ciclo lunar na eficiência de captura de morcegos, foi realizada uma análise com 28 noites de capturas no sudeste do Brasil. A taxa de captura e a riqueza de espécies apresentaram relação linear ...

  18. O ciclo circadiano na suscetibilidade para patologias oncológicas e na sua terapêutica

    OpenAIRE

    Marcos, Alexandra Filipa Sousa

    2012-01-01

    O ciclo circadiano é um ritmo biológico controlado pelo núcleo supraquiasmático presente no hipotálamo e regula, de uma forma rítmica ao longo de vinte e quatro horas, todos os processos homeostáticos dos seres vivos. A desregulação deste ritmo está associada ao aparecimento de várias patologias, entre elas o cancro, uma vez que a divisão celular, reparação do ADN e apoptose são controladas pela expressão circadiana de genes, os genes clock. Para além de ser um fator importante na susce...

  19. A seleção e o uso da gramática no 1º ciclo

    OpenAIRE

    Assis, Maria Cristina Estiveira Encarnado

    2013-01-01

    O presente estudo enquadra-se na dissertação para a obtenção do grau de Mestre em Ciências da Educação― Supervisão Pedagógica. Os objetivos são conhecer as representações dos professores que lecionam no 1.º Ciclo do Ensino Básico no concelho de Abrantes no ano letivo 2012/2013 sobre a seleção e uso do manual de gramática em contexto pedagógico. O quadro conceptual mostra a existência de diferentes significados do conceito de gramática, de norma gramatical e de transposição didáctica e a abord...

  20. Ciencia y experimentación en Segundo Ciclo de Educación Infantil. Descubrir el agua

    OpenAIRE

    González-Souto, M. Teresa

    2016-01-01

    Hacer ciencia en las aulas de educación infantil permite que los niños puedan aprender interactuando con el entorno a través de la experimentación y la observación. Si además se hace a partir de elementos cercanos en la vida de los alumnos, como es el agua, estarán más motivados a reflexionar y dialogar con sus compañeros para construir sus conocimientos desde la propia acción resultando aprendizajes más significativos. Esta propuesta, para niños de tercer curso del Segundo ciclo de Educac...

  1. Trabajar los problemas matemáticos mediante materiales lúdico-manipulativos en segundo ciclo de Primaria

    OpenAIRE

    Salas-Fortià, Anna

    2013-01-01

    El presente trabajo pretende ser una propuesta metodológica sobre cómo enfocar la didáctica de los problemas matemáticos con niños de segundo ciclo de primaria, aspecto en el que a menudo presentan dificultades. Con la aplicación de los recursos y métodos aquí propuestos se pretenderá lograr un mayor éxito en la resolución de problemas matemáticos, así como aumentar la motivación de los alumnos en relación a la asignatura de matemáticas. Para elaborar esta propuesta partimos de dos premisas b...

  2. HIPERAMONEMIA NEONATAL CAUSADA POR DEFECTOS DEL CICLO DE LA UREA Neonatal hyperammonemia in urea cycle disorders patients

    Directory of Open Access Journals (Sweden)

    Yolanda Cifuentes C

    2010-12-01

    Full Text Available Los defectos del ciclo de la úrea se deben a deficiencias de diferentes enzimas; las manifestaciones clínicas son similares y están relacionadas con la hiperamonemia. Se presentan las historias clínicas de tres neonatos a término, sin evidencia de alteración al nacimiento. Se les detectó hiperamonemia y se sospechó enfermedad metabólica. La cromatografía de aminoácidos sugirió defectos del ciclo de la úrea. El manejo incluyó dieta con restricción de proteínas, administración de benzoato de sodio, exsanguinotransfusión y diálisis peritoneal pese a lo cual fallecieron. Se revisan las causas de hiperamonemia en el neonato y se propone una secuencia para su diagnósticoThe urea cycle disorders result from deficiency of activity of enzymes N-acetyl glutamate synthetase, carbamyl phosphate synthase, ornithine transcarbamylase, argininosuccinic acid synthetase, argininosuccinic acid lyase and arginase. Except for the last one, the clinical features are similar and related with the hiperammonaemia. It reports three full term, newborn cases, they had encephalopathy and needed respiratory support after be well in neonatal period. They had hyperammonemia as inborn error. The thin layer amino acids chromatography showed alanine and glutamine, in the siblings appeared citruline, suggesting urea cycle disorders. Despite protein restriction diet, sodium benzoate administration, blood exchange and peritoneal dialysis,babies died. High argininosuccinic acid levels in the first case and high citrulline levels with argininosuccinic acid absence in the third case, which was diagnosed as argininosuccinic aciduria with citrullinemia. This report provide an overview of neonatal hyperammonemia causes and propose a secuency for diagnosis

  3. Modelo LUDO: el gobierno abierto desde la perspectiva del ciclo de las políticas públicas

    Directory of Open Access Journals (Sweden)

    Ortiz de Zárate, Alberto

    2012-06-01

    Full Text Available En este artículo se ofrece un modelo descriptivo que permite entender y ordenar las iniciativas de gobierno abierto en el marco del ciclo de creación de las políticas públicas. Este modelo se denomina “modelo LUDO de gobierno abierto”. Se trata de una forma de entender y de clasificar las iniciativas institucionales de transparencia, participación y colaboración. Podemos decir que tras el modelo LUDO subyace la tesis de que la transparencia, la participación y la colaboración necesitan de un buen diseño para alcanzar sus objetivos. Una de las claves de ese diseño es comprender el momento del ciclo de las políticas públicas en que se está aplicando. Otra clave es definir bien el grado de apertura –la cantidad de poder que se devuelve a la ciudadanía. El modelo LUDO pretende aportar claridad y diseño a las iniciativas de gobierno abierto, de manera que la dimensión “abierta” se pueda incorporar en la gestión de lo público sistemáticamente y que se establezca un contrato claro entre los poderes públicos y la ciudadanía. En el artículo se avanzará paso a paso a través de las distintas variables que conforman el modelo LUDO y se ofrecerá un par de ejemplos prácticos de cómo llevarlo a la práctica

  4. Os ciclos de formação como alternativa para a inclusão escolar

    Directory of Open Access Journals (Sweden)

    Ângela Imaculada Loureiro de Freitas Dalben

    2009-01-01

    Full Text Available A partir de la década de 1980, la cultura escolar pasó a ser foco de los debates sobre las necesidades urgentes de la construcción de una escuela capaz de abrigar y escolarizar la diversidad de la población del país, para enfrentar el fracaso escolar y resolver el problema del analfabetismo y de las desigualdades de acceso a los bienes culturales de la humanidad. Dentro de las alternativas, la organización de la escuela por ciclos pasó a ser una de las alternativas presentadas por las propuestas más osadas de transformación de esta cultura. Este trabajo discute parte de esta cuestión, posicionando la siguiente pregunta :¿sería la modificación del trabajo escolar de la seriación para la escuela ciclada la alternativa para el enfrentamiento del fracaso escolar en la escuela pública? Tomamos por base las pesquisas realizadas junto a la red municipal de Belo Horizonte, en los procesos de implantación e implementación del Proyecto Político Pedagógico Escuela Plural, en escena desde 1995. La pesquisa que dió soporte a esas reflexiones discute las experiencias prácticas de implementación de la organización por ciclos en las escuelas y las dificultades y desafíos vividos delante de las condiciones de trabajo en una red que decidió alterar la organización del trabajo en todo el sistema de una sola vez.

  5. Nuevos Patrones de Reconocimiento Visual en el Ciclo Cardiaco New Patterns of Visual Recognize in the Cardiac Cycle

    Directory of Open Access Journals (Sweden)

    Estela Audelo

    2007-01-01

    Full Text Available El objetivo de este trabajo es aplicar el análisis no lineal en el estudio del ciclo cardiaco. Se analizaron 30 series de tiempo con diferentes tipos de ritmo cardiaco (10 de sujetos en ritmo sinusal normal, 10 de sujetos con fibrilación atrial y 10 de sujetos con arritmia supraventricular, con las herramientas de análisis computacional, de la teoría del caos y la dinámica no lineal, para conocer la complejidad del sistema y encontrar patrones de reconocimiento visual. Se encontró que el ciclo cardiaco es un sistema con un comportamiento dinámico mixto (periódico-caótico y que las representaciones en el espacio-fase (atractores, obtenidas a partir de la relación entre la señal original (x(t y la primera derivada, pueden ser utilizadas como patrones de reconocimiento visual en la identificación de los tres ritmos cardiacos estudiados.Time series (30 with different heart rate were analyzed (10 of subjects in normal sinus rhythm, 10 of subjects with atrial fibrillation and 10 of subjects with supraventricular arrhythmia, with analysis computational of chaos and nonlinear dynamics theory in order to know the complexity of system and find visual recognize patterns. It was found that cardiac cycle is a mixed dynamic behavior system (periodic-chaotic and the representations (attractors in space phase obtained from the relation between the original signal (x(t and first derived, can be used like visual recognize patterns in the identification of the three studied heart rhythms.

  6. Finite time exergy analysis and multi-objective ecological optimization of a regenerative Brayton cycle considering the impact of flow rate variations

    International Nuclear Information System (INIS)

    Highlights: • Defining a dimensionless parameter includes the finite-time and size concepts. • Inserting the concept of exergy of fluid streams into finite-time thermodynamics. • Defining, drawing and modifying of maximum ecological function curve. • Suggesting the appropriate performance zone, according to maximum ecological curve. - Abstract: In this study, the optimal performance of a regenerative Brayton cycle is sought through power and then ecological function maximization using finite-time thermodynamic concept and finite-size components. Multi-objective optimization is used for maximizing the ecological function. Optimizations are performed using genetic algorithm. In order to take into account the finite-time and finite-size concepts in current problem, a dimensionless mass-flow parameter is introduced deploying time variations. The variations of output power, total exergy destruction of the system, and decision variables for the optimum state (maximum ecological function state) are compared to the maximum power state using the dimensionless parameter. The modified ecological function in optimum state is obtained and plotted relating to the dimensionless mass-flow parameter. One can see that the modified ecological function study results in a better performance than that obtained with the maximum power state. Finally, the appropriate performance zone of the heat engine will be obtained

  7. Exergoeconomic performance optimization of an endoreversible intercooled regenerative Brayton combined heat and power plant coupled to variable-temperature heat reservoirs

    Directory of Open Access Journals (Sweden)

    Bo Yang, Lingen Chen, Fengrui Sun

    2012-01-01

    Full Text Available An endoreversible intercooled regenerative Brayton combined heat and power (CHP plant model coupled to variable-temperature heat reservoirs is established. The exergoeconomic performance of the CHP plant is investigated using finite time thermodynamics. The analytical formulae about dimensionless profit rate and exergy efficiency of the CHP plant with the heat resistance losses in the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator are deduced. By taking the maximum profit rate as the objective, the heat conductance allocation among the five heat exchangers and the choice of intercooling pressure ratio are optimized by numerical examples, the characteristic of the optimal dimensionless profit rate versus corresponding exergy efficiency is investigated. When the optimization is performed further with respect to the total pressure ratio, a double-maximum profit rate is obtained. The effects of the design parameters on the double-maximum dimensionless profit rate and corresponding exergy efficiency, optimal total pressure ratio and optimal intercooling pressure ratio are analyzed in detail, and it is found that there exist an optimal consumer-side temperature and an optimal thermal capacitance rate matching between the working fluid and the heat reservoir, respectively, corresponding to a thrice-maximum dimensionless profit rate.

  8. Exergoeconomic performance optimization of an endoreversible intercooled regenerative Brayton combined heat and power plant coupled to variable-temperature heat reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bo; Chen, Lingen; Sun, Fengrui [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)

    2012-07-01

    An endoreversible intercooled regenerative Brayton combined heat and power (CHP) plant model coupled to variable-temperature heat reservoirs is established. The exergoeconomic performance of the CHP plant is investigated using finite time thermodynamics. The analytical formulae about dimensionless profit rate and exergy efficiency of the CHP plant with the heat resistance losses in the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator are deduced. By taking the maximum profit rate as the objective, the heat conductance allocation among the five heat exchangers and the choice of intercooling pressure ratio are optimized by numerical examples, the characteristic of the optimal dimensionless profit rate versus corresponding exergy efficiency is investigated. When the optimization is performed further with respect to the total pressure ratio, a double-maximum profit rate is obtained. The effects of the design parameters on the double-maximum dimensionless profit rate and corresponding exergy efficiency, optimal total pressure ratio and optimal intercooling pressure ratio are analyzed in detail, and it is found that there exist an optimal consumer-side temperature and an optimal thermal capacitance rate matching between the working fluid and the heat reservoir, respectively, corresponding to a thrice-maximum dimensionless profit rate.

  9. Performance comparison of an irreversible closed variable-temperature heat reservoir Brayton cycle under maximum power density and maximum power conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, L.; Zheng, J.; Sun, F. [Naval University of Engineering, Wuhan (China); Wu, C. [US Naval Academy, Annapolis, MD (United States). Dept. of Mechanical Engineering

    2005-11-15

    The power density is taken as an objective for performance analysis of an irreversible closed Brayton cycle coupled to variable-temperature heat reservoirs. The analytical formulas about the relationship between power density and working fluid temperature ratio (pressure ratio) are derived with the heat resistance losses in the hot- and cold-side heat exchangers, the irreversible compression and expansion losses in the compressor and turbine, and the effect of the finite thermal capacity rate of the heat reservoirs. The obtained results are compared with those results obtained by using the maximum power criterion. The influences of some design parameters, including the temperature ratio of the heat reservoirs, the effectivenesses of the heat exchangers between the working fluid and the heat reservoirs, and the efficiencies of the compressor and the turbine, on the maximum power density are provided by numerical examples, and the advantages and disadvantages of maximum power density design are analysed. The power plant design with maximum power density leads to a higher efficiency and smaller size. When the heat transfers between the working fluid and the heat reservoirs are carried out ideally and the thermal capacity rates of the heat reservoirs are infinite, the results of this article become similar to those obtained in the recent literature. (author)

  10. Processing of red ceramic using a fast-firing cycle Processamento de cerâmica vermelha usando um ciclo de queima rápido

    Directory of Open Access Journals (Sweden)

    G. T. Saleiro

    2012-09-01

    Full Text Available This work reports on the processing of red ceramic for civil construction using fast-firing cycles. The firing cycle is an important variable in the processing of red ceramic materials, which contributes to a high consumption of energy. The red ceramic pieces were prepared by industrial extrusion and fired at firing temperatures varying from 700 ºC to 1100 ºC using different firing cycles (slow-firing cycle - 1º C/min and fast-firing cycle - 10 ºC/min and 20 °C/min. The technological properties (linear shrinkage, water absorption, apparent porosity, apparent density, and flexural strength as function of the firing temperature and firing cycle are investigated. The development of the microstructure was followed by SEM/SEI. The results showed that fast-firing red ceramics exhibits technological properties and microstructure comparable to conventionally fired red ceramics, resulting in great advantages in energy saving.Este trabalho descreve o processamento de cerâmica vermelha para construção civil usando ciclos de queima rápido. O ciclo de queima é uma variável importante no processamento de materiais de cerâmica vermelha, o qual contribui para um alto consumo de energia. As peças de cerâmica vermelha foram preparadas por extrusão industrial e queimadas nas temperaturas de queima variando de 700 ºC a 1100 ºC utilizando diferentes ciclos de queima (ciclo de queima lento - 1 ºC/min e ciclos de queima rápidos - 10 ºC/ min e 20 ºC/min. As propriedades tecnológicas (retração linear, absorção de água, porosidade aparente, massa específica aparente e tensão de ruptura à flexão em função da temperatura de queima e ciclo de queima são investigadas. O desenvolvimento da microestrutura foi avaliado por SEM/SEI. Os resultados mostraram que as peças de cerâmica vermelha obtidas via processo de queima rápida exibiram propriedades tecnológicas e microestrutura comparáveis àquelas convencionalmente obtidas via queima lenta

  11. RELAÇÕES HÍDRICAS EM DOIS HÍBRIDOS DE MILHO SOB DOIS CICLOS DE DEFICIÊNCIA HÍDRICA WATER RELATIONS IN TWO HYBRIDS OF CORN UNDER TWO CYCLES OF WATER STRESS

    OpenAIRE

    CARLOS PIMENTEL

    1999-01-01

    Neste trabalho foram estudadas as relações hídricas de dois híbridos de milho (Zea mays L.), em casa de vegetação: o IAC 8222 (híbrido com tolerância ambiental) e o DINA 10 (híbrido comum); submetidos a um ou a dois ciclos de estresse, aos 30 e 46 DAP. O IAC 8222 manteve o potencial hídrico de folha (psihf) superior ao do DINA no primeiro ciclo de estresse e no segundo ciclo, em plantas que sofreram os dois ciclos (com endurecimento), no sexto e último dia de deficiência hídrica, não havendo ...

  12. Ciclos económicos y retórica administrativa. Dualidad ideológica en Colombia Ciclos económicos y retórica administrativa. Dualidad ideológica en Colombia

    Directory of Open Access Journals (Sweden)

    César Alexander Toro Suárez

    2007-06-01

    Full Text Available En 1992, Stephen R. Barley y Gideon Kunda, profesores de la universidad deStanford y de la universidad de Tel Aviv respectivamente, publicaron un estudiotitulado: “Desing and devotion: surges of rational and normative ideologies ofcontrol in managerial discourse”* en el que encontraron que en Estados Unidos,las teorías administrativas se presentan en oleadas de retórica en correspondenciadirecta con los ciclos económicos. De esta manera, las teorías de contenido racional(dirigidas al control del trabajo sobresalen en períodos de crecimiento, y las decontenido normativo (dirigidas al control del trabajador prevalecen en contraccióneconómica. Partiendo de estos resultados, y retomando la esquematizaciónhistórica del surgimiento de las oleadas de ideología administrativa en Colombiaplanteada por el profesor Francisco López G. (1998, aquí se realizó un estudiosimilar y se encontró que el desarrollo del pensamiento administrativo en Colombiatiene igualmente relación con el ciclo económico, emerge en oleadas y presentacaracterísticas particulares.Professors Stephen R. Barley and Gideon Kunda (1992 conducted a study titled: “Design and Devotion: Surges of Rational and Normative Ideologies of Control in Managerial Discourse” in which they found that in the United States management theories are presented in waves of rhetoric which corresponded directly with economic cycles. In this way, theories with rational content (those directed at controlling work stand out in periods of growth, while those with normative content (those directed at controlling the worker prevail in times of economic shrinking. Based on these results, and returning to the historical scheme of the appearance of waves of management ideology in Colombia proposed by professor Francisco López G. (1998, a similar study was conducted in which the development of management thinking in Colombia was found to also have a relation to the economic cycle, to

  13. Avaliação do ciclo de vida e custeio do ciclo de vida de evaporadores para usinas de açúcar Life cycle assessment and life cycle cost of cugar plants evaporators

    Directory of Open Access Journals (Sweden)

    Lino José Cardoso Santos

    2010-03-01

    Full Text Available As usinas de açúcar no Brasil utilizam aço-carbono, um material de baixo custo, mas com pequena resistência à corrosão. Os aços inoxidáveis são os materiais mais adequados para a sua substituição, entretanto eles são considerados caros. Foi realizada a avaliação ambiental e financeira de tubos para evaporadores de usinas de açúcar construídos em aço-carbono e, comparativamente, com os aços inoxidáveis do tipo AISI 304, 444 e 439. Para a avaliação ambiental, foi utilizada a Avaliação do Ciclo de Vida (ACV, que mostrou que os aços inoxidáveis são ambientalmente mais eficientes. Para a avaliação financeira, foi utilizado o Custeio do Ciclo de Vida (CCV, que mostrou que os tubos em aços inoxidáveis são opções de investimento mais interessantes. O período de tempo dessas avaliações foi igual há trinta anos. Os resultados obtidos mostram que a ACV e o CCV devem ser usados em conjunto, pois mostram que produtos mais seguros ambientalmente podem vir a ser opções de investimentos também mais interessantes.The evaporators of sugar plants in Brazil have used carbon steel intensively because of it is, a low priced material, which possesses inferior corrosion resistance. The materials more indicated for the substitution of carbon steel are stainless steels, however, they are considered expensive. The environmental and financial performances of evaporator pipes constructed with carbon steel and with types AISI 304, 444 and 439 stainless steel were evaluated. For the environmental evaluation, the Life Cycle Assessment (LCA methodology was used and it, revealed that stainless steel is more environmentally efficient than carbon steel. The life cycle costing (LCC technique was the tool chosen for the financial evaluation and it showed that stainless steel is a better investment option compared to carbon steel. The results also indicate that LCA and LCC methodologies must be used together. Therefore, it can be seen that

  14. Estratégias para o desenvolvimento da competência comunicativa em educadores de infância e professores de 1º ciclo

    OpenAIRE

    Vargas, Marisa

    2012-01-01

    Dissertação de mestrado em Ciências da educação - especialização em educação pré-escolar e ensino do 1º ciclo do ensino básico, Instituto Politécnico de Beja, Escola Superior de Educação, 2012. "O presente estudo tem como foco a comunicação na área da educação, mais precisamente direcionado a educadores de infância e professores de 1º ciclo. Pretende conhecer a consciência destes profissionais relativamente às suas competências comunicativas e o impacto das mesmas na sala de aula. A que...

  15. Atividade Ovariana em Fêmeas Bovinas da Raça Holandesa e Mestiças Holandês x Zebu, Durante Dois Ciclos Estrais Normais Consecutivos

    Directory of Open Access Journals (Sweden)

    Alves Nadja Gomes

    2002-01-01

    Full Text Available Foram utilizadas 25 fêmeas, distribuídas de acordo com o grau de sangue Holandês x Zebu nos grupos: I = 1/2 Holandês x Zebu; II = 3/4 Holandês x Zebu; III= 15/16 Holandês x Zebu; IV= Holandês--PB¾PC; e V= 7/8 Holandês x Zebu. Após o segundo estro natural pós-parto, esses animais foram monitorados por exames ultra-sonográficos diários por dois ciclos estrais consecutivos, para verificar a atividade ovariana quanto à dinâmica folicular e à atividade do corpo lúteo. O período interovulatório médio foi de 22,08±2,46 dias, sendo de 21,76±3,33 e 21,94±2,90 dias no primeiro e no segundo ciclo estral, respectivamente, não havendo diferença entre os grupos estudados. Observou-se o crescimento de uma (6%, duas (78% e três (16% ondas foliculares durante o ciclo estral, com a predominância de duas ondas foliculares. O período interovulatório dos ciclos com três ondas mostrou-se mais longo (25,33±4,37 dias, em comparação com uma (16,0±3,6 dias e duas (21,83±1,77 dias ondas foliculares. A duração das ondas foliculares para ciclos estrais com três ondas de crescimento folicular foi de 11,0±3,69; 7,17±1,60; e 8,5±1,52 dias na 1ª, 2ª e 3ª ondas, respectivamente, e de 11,15±1,65 e 12,07±2,32 dias nos ciclos estrais com duas ondas foliculares. Os dias de maior concentração plasmática de progesterona no 1º e 2º ciclos estrais foram, respectivamente, de 13,6±3,0 (7,29±4,3 ng/mL e 11,8±3,4 (5,6±2,0 ng/mL dias, não se mostrando diferentes entre os grupamentos genéticos e ciclos estrais estudados. Pelas análises dos dados, pode-se concluir que os diferentes grupamentos genéticos apresentaram o mesmo comportamento na dinâmica folicular e que as concentrações de progesterona, embora diferentes em números absolutos entre os grupamentos, mostraram-se indicativas de atividade luteal normal.

  16. Os ciclos de Wilson numa perspectiva da CPLP: um contributo para o ensino da Geologia nos países lusófonos

    OpenAIRE

    Dias, Rui; Rocha, Rogério; Kullberg, José Carlos; Ribeiro, António; Fonseca, Marco

    2014-01-01

    A extrema duração dos processos associados a um ciclo de Wilson (que se estendem por algumas centenas de milhões de anos) torna impossível a sua observação em tempo real. Torna-se por isso necessário recorrer ao estudo de exemplos extraídos de diversas partes do Mundo que se pensa representarem diferentes estádios evolutivos de diferentes ciclos de Wilson; a integração dos exemplos permite então a compreensão do processo global; no fundo, uma outra forma de aplicação do p...

  17. Análisis de las transiciones juveniles desde la perspectiva de género: entre la influencia del ciclo vital y el cambio generacional

    Directory of Open Access Journals (Sweden)

    Sara Moreno Colom

    2015-04-01

    Full Text Available El artículo presenta una aproximación a la transición educativa, laboral, domiciliar y familiar de las personas jóvenes desde la perspectiva de género. El objetivo es analizar hasta qué punto la mejora del nivel educativo introduce transformaciones en el carácter tradicionalmente sexuado de las transiciones hacia la vida adulta. El análisis parte del conjunto de factores estructurales que pueden condicionar las transiciones juveniles, si bien atribuye una influencia central a la etapa del ciclo vital. A partir de los datos de la Enquesta a la Juventud de Catalunya 2012, se concluye que el efecto ciclo vital limita el efecto generacional en la transformación de las relaciones de género entre la población joven.

  18. Prática de ensino supervisionada em Educação Pré-Escolar e ensino do 1º Ciclo do Ensino Básico

    OpenAIRE

    Magalhães, Marina Ferreira

    2015-01-01

    O presente relatório surgiu no âmbito da unidade curricular de Prática de Ensino Supervisionada, do curso de mestrado em Educação Pré-escolar e Ensino do 1.º Ciclo do Ensino Básico, e tem como principal objetivo a realização de uma investigação e reflexão sobre a prática em contexto de Educação Pré-escolar e em contexto do 1.º Ciclo do Ensino Básico. A nossa prática foi desenvolvida, em ambos os casos, em contexto urbano, com um grupo de crianças de 3 anos de idade, em contexto de educação pr...

  19. Prática de ensino supervisionada em Educação Pré-escolar e Ensino do 1º Ciclo do Ensino Básico

    OpenAIRE

    Mendes, Ana Rita Vieira de Magalhães Ricardo

    2015-01-01

    O presente relatório foi realizado no âmbito da unidade curricular de Prática de Ensino Supervisionada (PES), inserida no plano de estudos do curso de Mestrado em Educação Pré-Escolar e Ensino do 1.º Ciclo do Ensino Básico, da Escola Superior de Educação do Instituto Politécnico de Bragança. A intervenção em contexto de Educação Pré-Escolar teve a duração de 180 horas, das quais 24 horas foram em contexto Creche. A intervenção em contexto de 1.º Ciclo do Ensino Básico teve a duração de 180 ho...

  20. Educação musical e animação socioeducativa no 1º ciclo no âmbito das actividades de enriquecimento curricular

    OpenAIRE

    Canto, Helena Maria Portugal do

    2010-01-01

    Dissertação de Mestrado em em Ciências da Educação O presente estudo tem por objectivo, apurar qual o contributo da Expressão e Educação Musical no 1º Ciclo, no âmbito das Actividades de Enriquecimento Curricular, enquanto técnica de Animação Socioeducativa no contexto educativo da escola do 1º Ciclo de Casas dos Montes, face à sua acção enquanto meio de aquisição de conhecimentos e crescimento global e integral da criança. No que concerne à componente teórica, desenvolvemos os seguintes p...

  1. Desempenho de motor ciclo Diesel em bancada dinamométrica utilizando misturas diesel/biodiesel Performance of cycle Diesel engine in dynamometer using diesel/biodiesel mixtures

    OpenAIRE

    Marcio Castellanelli; Samuel N. M. de Souza; Suedêmio L. Silva; Euro K. Kailer

    2008-01-01

    Diante da previsão de escassez do petróleo, o éster etílico (biodiesel) tem-se apresentado como excelente opção de combustível alternativo para motores ciclo Diesel. As características do biodiesel são semelhantes às do diesel em termos de viscosidade e poder calorífico, podendo ser utilizado sem adaptações nos motores. Para a realização deste trabalho, utilizou-se de motor ciclo Diesel, de injeção direta, com quatro cilindros, sem adaptações. O motor foi acoplado a um dinamômetro e sistemas ...

  2. Conceções dos alunos do 1.º Ciclo do Ensino Básico sobre a família

    OpenAIRE

    Bento CAVADAS; Botelho, Irina; Pereira, Susana; Pereira, Tânia; Cortesão, Vanessa

    2011-01-01

    A família possui uma importância crucial para o desenvolvimento das crianças, sendo uma temática abordada com alguma frequência no 1.º Ciclo do Ensino Básico. O presente estudo teve como principal objetivo aferir as concepções de 90 alunos dos 3.º e 4.º anos de escolaridade do 1.º Ciclo do Ensino Básico sobre a organização da sua família, através da análise iconográfica dos desenhos que elaboraram sobre o assunto. Num primeiro momento, os desenhos foram analisados qualitativamente, organizado...

  3. Estudio de los reguladores del ciclo celular asociados al desarrollo de cáncer oral en una muestra de la provincia de Álava

    OpenAIRE

    Rodríguez Gutierrez, José Carlos

    2010-01-01

    En la última década se ha producido un enorme avance en el conocimiento de los mecanismos de control de la proliferación celular en los que interviene un complejo engranaje de moléculas que actúan favoreciendo unas e inhibiendo otras, la progresión de la célula a lo largo de su ciclo de división. El cáncer conlleva una alteración de sistema de regulación con la consiguiente proliferación incontrolada. Por tanto conocer las alteraciones en las moléculas que intervienen en el control del ciclo ...

  4. Director de turma no 2º ciclo do ensino básico: dimensão de orientação

    OpenAIRE

    Sousa, Lúcia Maria Proença Ribeiro de

    2010-01-01

    A partir de 1968 passou a existir, nas escolas portuguesas do Ciclo Preparató-rio do Ensino Secundário, o cargo de director de turma e desde então vários normativos legais foram publicados relativamente às suas atribuições. Ao director de turma têm competido funções administrativas, de coordenação, de ligação aos pais/encarregados de educação e de orientação. No 2.º ciclo do ensino básico, esta orientação faz-se sobretudo a nível pessoal, social e esco-lar. Como orientador, o director de t...

  5. Prática de ensino supervisionada em Ensino do 1º e do 2º Ciclo do Ensino Básico

    OpenAIRE

    Maciel, Bruna Sofia Alves

    2014-01-01

    O presente relatório foi realizado no âmbito da Unidade Curricular da Prática de Ensino Supervisionada do Mestrado em Ensino do 1.º e 2.º Ciclo do Ensino Básico da Escola Superior de Educação de Bragança, realizada no ano letivo de 2013/2014. Este relatório final apresenta experiências de ensino-aprendizagem desenvolvidas em três instituições escolares públicas da cidade de Bragança: uma do 1.º ciclo, onde asseguramos a lecionação nas áreas curriculares de Matemática, Português, Estudo do ...

  6. State space model extraction of thermohydraulic systems – Part II: A linear graph approach applied to a Brayton cycle-based power conversion unit

    International Nuclear Information System (INIS)

    This second paper in a two part series presents the application of a developed state space model extraction methodology applied to a Brayton cycle-based PCU (power conversion unit) of a PBMR (pebble bed modular reactor). The goal is to investigate if the state space extraction methodology can cope with larger and more complex thermohydraulic systems. In Part I the state space model extraction methodology for the purpose of control was described in detail and a state space representation was extracted for a U-tube system to illustrate the concept. In this paper a 25th order nonlinear state space representation in terms of the different energy domains is extracted. This state space representation is solved and the responses of a number of important states are compared with results obtained from a PBMR PCU Flownex® model. Flownex® is a validated thermo fluid simulation software package. The results show that the state space model closely resembles the dynamics of the PBMR PCU. This kind of model may be used for nonlinear MIMO (multi-input, multi-output) type of control strategies. However, there is still a need for linear state space models since many control system design and analysis techniques require a linear state space model. This issue is also addressed in this paper by showing how a linear state space model can be derived from the extracted nonlinear state space model. The linearised state space model is also validated by comparing the state space model to an existing linear Simulink® model of the PBMR PCU system. - Highlights: • State space model extraction of a pebble bed modular reactor PCU (power conversion unit). • A 25th order nonlinear time varying state space model is obtained. • Linearisation of a nonlinear state space model for use in power output control. • Non-minimum phase characteristic that is challenging in terms of control. • Models derived are useful for MIMO control strategies

  7. Off-design performance prediction of Radial Compressor of Supercritical CO{sub 2} Brayton Cycle for KAIST Micro Modular Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seongkuk; Lee, Jekyoung; Kim, Seong Gu; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-10-15

    KAIST research team suggested a new concept of SMR, which utilizes S-CO{sub 2} as the operating fluid and coolant. It was named as KAIST MMR(Micro Modular Reactor). Compared with existing SMR concepts, this reactor has advantages of achieving smaller volume of power conversion unit (PCU) containing the core and PCU in one vessel for the complete modularization passive air-cooling system more flexible installation in the inland area. In previous study, performance of turbomachinery in PCU was considered only on-design. But, off-design performances of each component can affect not only PCU but also the core because this reactor adopts the direct S-CO{sub 2} loop in GFR. Nuclear system is applied by relatively conservative criteria of safety. Thus, off-design performances of each component should be considered in order to be more realistic reactor. The suggested turbomachinery size of the S-CO{sub 2} cycle is relatively smaller than those of helium Brayton cycle and steam Rankine cycle. Performance analysis of compressor is conducted by KAIST-TMD in case of on-design and off-design. Compressor efficiency in on-design conditions is obtained 84.51 %. But compressor performance in off-design conditions decreases certainly. This means that more heat than existing prediction is rejected by air-cooling system. KAIST-TMD will be verified with more experiment data for providing the results of more accurate analysis. Also, this code will be modified to couple with safety analysis codes and S-CO{sub 2} cycle analysis codes in the future. Furthermore, authors will consider aerodynamic performance analysis and various losses for more realization.

  8. La importancia del ciclo de caja y cálculo del capital de trabajo en la gerencia PYME

    Directory of Open Access Journals (Sweden)

    Jorge Iván Jiménez Sánchez

    2014-01-01

    Full Text Available  El artículo aborda las finanzas en la pyme moderna, la cual necesita de un gerente dinámico y hábil en la gestión administrativa, la información contable y las finanzas, con conocimiento de los días necesarios para cubrir el ciclo de caja y el capital que se requiere para operar a corto plazo, calculo necesario para determinar si va a alcanzar el dinero o si va a necesitar financiación y su valor exacto. Las cifras de fracaso de las pymes en América Latina son abrumadoras, ochenta por ciento de ellas quiebran en menos de cinco años gran parte debido a la mala gestión, se requiere una administración que incluso piense en cómo fortalecer la empresa, con sistemas como el Leasing, el factoring o la triangulación, en Colombia se habla incluso de crear un mercado de capitales y de un mercado alternativo bursátil para la pyme.Palabras Clave: Gerencia pyme; ciclo de caja; capital de trabajo; Mecanismos de financiación; mercados de capitales.AbstractThe importance of cash cycle and calculation of working capital management in smesThe article discusses the modern SME finance, which needsa dynamic and skilled manager in administrative management, the accounting and finance, with knowledge of the days needed to cover the cash cycle and the capital required to operate in the short term, calculation necessary to determine if you have enough money or if you will need financing and its exact value, failure figures of SMEs in Latin America are overwhelming, eighty percent of them go bankrupt in less than five years largely due to poor management, management is required to even think about how to strengthen the company with systems such as leasing, factoring or triangulation, in Colombia there is even talk of creating a capital market and an alternative stock market for SMEs.Keywords: Management SME cash cycle; working capital; financing mechanisms; capital markets. 

  9. Empowerment: ciclo de implementação, dimensões e tipologia Empowerment: implementation cycle, dimensions and typology

    Directory of Open Access Journals (Sweden)

    Claudia Heloisa Ribeiro Rodrigues

    2001-12-01

    Full Text Available O empowerment é uma abordagem de projeto de trabalho que objetiva a delegação de poder de decisão, autonomia e participação dos funcionários na administração das empresas. Este artigo mostra as especificidades do empowerment em termos de suas dimensões, ciclo de implementação e tipologia. Discutem-se as etapas do ciclo de implementação do empowerment com o objetivo de enfatizar sua complexidade e sua natureza estratégica. Como dimensões tratadas têm-se: a visão compartilhada, a estrutura organizacional e o gerenciamento, a responsabilidade pela gestão do conhecimento e aprendizagem, e o reconhecimento institucional dos funcionários. A diversidade do empowerment é analisada em função de dois tipos de autoridade para tomada de decisão: sobre o conteúdo do trabalho e a sobre o contexto do trabalho. Com base nesta análise, os seguintes tipos de empowerment são apresentados: nulo, estabelecimento de atividades, participativo, definição de missão e auto-gerenciamento. Estabelecem-se também relações do empowerment com as configurações organizacionais, os estágios evolutivos das áreas funcionais e a administração de recursos humanos.Empowerment is an approach of work design which aims at delegating decision power, autonomy and employees’ participation in managing the company. This paper shows the peculiarities of empowerment in terms of its dimension, implementation cycle and typology. The steps of its implementation cycle are discussed in order to highlight its complexity and strategic nature. The following dimensions are presented: shared vision, organizational structure and management, responsibility for knowledge management and learning, and employees’ institutional recognition. The diversity of empowerment is analyzed in function of two types of authority for decision-making: over job content and over job context. Based on this analysis, the following typology of empowerment is presented: no discretion

  10. Ciclo de produção e demanda térmica de clones da videira 'Concord' sobre diferentes porta-enxertos

    Directory of Open Access Journals (Sweden)

    Rogério de Sá Borges

    2014-12-01

    Full Text Available O objetivo do trabalho foi determinar a duração do ciclo de produção e a necessidade térmica de seis clones de 'Concord' sobre três porta-enxertos no norte do Paraná. Foram avaliados os clones '22', '28', '49', '202', '211' e '225', obtidos pela Embrapa Uva e Vinho, e enxertados sobre os porta-enxertos 'IAC 766', 'IAC 572' e '420-A'. O trabalho foi realizado em área experimental pertencente ao Centro Tecnológico da COROL - Cooperativa Agroindustrial, localizado no município de Rolândia-PR. O experimento foi realizado em esquema fatorial (6 clones x 3 porta-enxertos, em delineamento inteiramente casualizado, com cinco repetições. As plantas foram conduzidas em sistema de latada, no espaçamento de 4,0 m x 2,0 m, e as avaliações foram realizadas nas safras de 2009/2010 e 2010/2011. Verificou-se que dentre os clones de 'Concord' avaliados, o '202' apresenta a menor duração do ciclo entre a poda e a colheita, sendo portanto o mais precoce. Dentre os porta-enxertos, o '420-A' induz a maior taxa de acúmulo diário de sólidos solúveis do mosto, proporcionando redução do ciclo total e da demanda térmica dos clones de 'Concord', enquanto o 'IAC 572' induz a menor taxa, promovendo aumento do ciclo e da demanda térmica dos clones.

  11. Conocerse a través de los equilibrios y emociones. Proyecto extraescolar dirigido al 2º ciclo de Educación Primaria

    OpenAIRE

    Ramajo González, María

    2014-01-01

    Es un proyecto práctico de carácter extraescolar destinado al segundo ciclo de educación primaria. Se basa en una actividad física que comprende la ejecución de ejercicios específicos del equilibrio y su relación con la manifestación de las emociones mediante las sensaciones que percibe el cuerpo.

  12. Explorações geométricas na cidade : uma experiência de aprendizagem no 1.º ciclo do ensino básico

    OpenAIRE

    Silva, Neuza Carina Martins da

    2015-01-01

    Relatório de Estágio apresentado à Escola Superior de Educação do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré-Escolar e 1.º Ciclo do Ensino Básico.

  13. As potencialidades da utilização em contexto educativo do podcast no 1º ciclo do ensino básico

    OpenAIRE

    Henriques, Joana Rita dos Santos

    2016-01-01

    Relatório de Estágio apresentado à Escola Superior de Educação do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré-Escolar e Ensino do 1º Ciclo do Ensino Básico.

  14. A transmissão dos direitos da criança no 1º Ciclo : o papel dos textos de literatura para a infância

    OpenAIRE

    Afonso, Inês da Conceição Marques

    2014-01-01

    Relatório de Estágio apresentado à Escola Superior de Educação do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré-Escolar e Ensino do 1º Ciclo do Ensino Básico.

  15. Las representaciones de las relaciones de pareja a lo largo del ciclo vital: significados asociados y percepción del cambio evolutivo

    OpenAIRE

    Villamizar Carrillo, Diana Janeth

    2009-01-01

    El objetivo, determinar la satisfacción con las relaciones de pareja, las representaciones que se tienen y significados junto a los cambios evolutivos que perciben las personas en relación a su experiencia amorosa, desde la psicología del ciclo vital y del amor, es un estudio transversal de tipo exploratorio descriptivo, con tres instrumentos: cuestionario de satisfacción marital, cuestionario de frases incompletas para evaluar percepciones y significados, y cuestionario de cambios evolutiv...

  16. Actividades físicas en el medio natural. La orientación con bicicleta en el tercer ciclo de educación primaria

    OpenAIRE

    Rincón Rodrigo, Santos

    2016-01-01

    El trabajo es un plan de intervención de desarrollo de una jornada de orientación llevada a cabo de una forma novedosa, es decir, con la bicicleta, destinada para niños del tercer ciclo de E. Primaria. El trabajo consta de una sesión en la zona de Boca del Asno (Valsaín). Grado en Educación Primaria

  17. Influência do ciclo lunar no parto: mito ou constatação científica? Influencia del ciclo lunar en el parto: mito o constatación científica? Influences of lunar cycle in labor: myth or scientific finding?

    Directory of Open Access Journals (Sweden)

    Aline Bueno

    2010-06-01

    Full Text Available Muitas superstições são encontradas em nossas vidas. Na medicina, uma profissão que se orgulha em métodos baseados em evidências para tratamentos, isso não é uma exceção. Uma superstição que abrange o parto é a influência de determinadas fases do ciclo da lua, mais especificamente a lua cheia. Embora estudos tenham demonstrado que o aumento de partos está relacionado com o ciclo lunar, existe discordância sobre quando ocorre o pico do volume de partos em cada fase da lua. Frente à divergência de resultados existentes na literatura que relaciona os eventos do ciclo lunar com parto, o objetivo desta revisão foi realizar um levantamento bibliográfico na tentativa de esclarecer esta cultura popular com base nos resultados apresentados por diferentes autores.Se encuentran las supersticiones por todas partes en nuestras vidas, y la medicina, una profesión que tiene orgullo acerca de los tratamientos con base en evidencia, no está extinta. La influencia de ciertas fases del ciclo lunar, específicamente la luna llena, es una superstición sobre el parto. Aunque algunos estudios han demostrado un aumento en los partos que se relacionan al ciclo lunar, ha habido discordancia sobre cuando, en el ciclo lunar, el volumen máximo ocurre. Afronte a la divergencia de los resultados existentes en la literatura que relacionan los eventos del ciclo lunar con los partos, el objetivo de esta revisión era explorar la literatura en el esfuerzo de explicar esta cultura popular con la base en los resultados presentado por los diferentes investigadores.Superstitions are found everywhere in our lives, and medicine, a profession that is prides itself on an evidence-based approach to treatment, is not exempt. A superstition that pervades the labor and delivery floor is that it is busier during certain phases of the lunar cycle, specifically the full moon. Although some studies have demonstrated an increase in deliveries that are related to the lunar

  18. A pesquisa sobre a organização da escolaridade em ciclos no Brasil (2000-2006: mapeamento e problematizações

    Directory of Open Access Journals (Sweden)

    Jefferson Mainardes

    2009-01-01

    Full Text Available Este artículo presenta un análisis de 123 tesis y disertaciones sobre la organización de la escolaridad en ciclos en Brasil escritas durante período que abarca del 2000 al 2006. Resulta en una tentantiva por realizar una revisión sistemática de las investigaciones sobre el tema con el objetivo de identificar las principales tendencias, contribuciones, lagunas y problemas con él relacionados. A partir del analisis de estos trabajos el artículo explora dos aspectos específicos: la relación macro y micro y la discusión sobre los fundamentos de la política (escuela en ciclos. El artículo indica que es necesario profundizar aspectos teóricos y metodológicos de la investigación sobre ciclos, considerar las determinaciones más amplias relacionadas a la política, como el sistema de mediaciones, de forma de buscar una comprensión del conjunto de las relaciones que se establecen con los demás fenómenos y con la totalidad.

  19. L’ipotesi del ciclo vitale, la politica fiscale e la previdenza sociale (The hypothesis of the life cycle, fiscal policy and social security

    Directory of Open Access Journals (Sweden)

    Tullio Jappelli

    2012-04-01

    Full Text Available Il lavoro riassume le principali implicazioni dell’ipotesi del ciclo vitale per quanto riguarda il risparmio individuale e aggregato, la politica fiscale e la previdenza sociale, soffermandosi sui contributi più importanti di Modigliani su questi temi. Anche se non è facile conciliare alcuni risultati empirici recenti con l’ipotesi del ciclo vitale, soprattutto gli aspetti di inerzia, miopia e comportamento irrazionale documentati nella letteratura comportamentale, gli studi di Modigliani rappresentano ancora oggi la base di riferimento principale per studiare le decisioni di risparmio individuali e per operare scelte di politica economica.    The paper summarizes the main implications of the life cycle hypothesis regarding the individual and aggregate saving, fiscal policy and social security, focusing on the most important contributions of Modigliani on these issues. Although it is not easy to reconcile some recent empirical results with the hypothesis of the life cycle, especially the aspects of inertia, myopia and irrational behavior documented in the literature behavioral, the studies of Modigliani still represent the basis of reference for the study of individual savings decisions and to make policy choices.  JEL Codes: D91Keywords: ciclo vitale, risparmio, modigliani, politica economica

  20. CICLO DE VIDA DO GOL VW: UMA ANÁLISE DAS UNIDADES VENDIDAS NO MERCADO BRASILEIRO ENTRE OS ANOS 1987 E 2010

    Directory of Open Access Journals (Sweden)

    Paulo de Tarso Braga

    2010-06-01

    Full Text Available Nos últimos anos, o segmento de veículos automotores no Brasil vem sofrendo significativas mudanças em função das transformações do cenário econômico, tanto nacional como internacional. A abertura comercial e financeira do país provocou uma reestruturação do setor, no sentido de globalização da cadeia produtiva e de relações comerciais. A análise do ciclo de vida pode auxiliar a identificar a maturidade do produto, concedendo assim um diferencial em relação às empresas concorrentes. O trabalho tem por objetivo identificar, por meio da observação do comportamento das unidades vendidas do veículo Gol VW (fabricado pela Volkswagen do Brasil no mercado brasileiro no período de 1987 até 2010, a aderência entre o ciclo de vida e as estratégias de renovação do produto por parte da fabricante. O comportamento dos dados sugere fases de ciclo de vida definidas para cada geração e que a empresa utiliza estratégias de prolongamento da permanência do veículo no mercado.

  1. El azúcar en los distintos ciclos de la vida: desde la infancia hasta la vejez

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    Teresa Partearroyo

    2013-07-01

    Full Text Available Se revisa la importancia que tienen los diferentes tipos de azúcares consumidos a través de la dieta y en diferentes fuentes alimentarias en las etapas de la vida y situaciones fisiológicas especiales, y como el consumo moderado de azúcar es compatible con una dieta equilibrada y estilos de vida activos. Se describe también su función en el disfrute y placer de comer, como uno de los pilares básicos también de una alimentación equilibrada. Al mismo tiempo, se evalúan los riesgos del consumo muy insuficiente, principalmente en lo referido a un bajo aporte de glucosa en etapas críticas de la vida, así como las potenciales consecuencias negativas sobre el estado de salud en el ciclo vital cuando la ingesta es excesiva, y la asociación con factores de riesgo en enfermedades crónico-degenerativas, o con complicaciones en el embarazo. Finalmente, se aportan recomendaciones para un correcto consumo desde el punto de vista nutricional que constituyan, finalmente, herramientas válidas para una evaluación beneficio/riesgo a nivel individual o desde el punto de vista de la salud pública.

  2. Teoría austriaca de los ciclos económicos y la economía venezolana

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    Emmanuel Borgucci

    2011-05-01

    Full Text Available Por lo general se piensa que los problemas económicos venezolanos solamente pueden ser descritos por la denominada síntesis neoclásica. Existió a finales del siglo XIX y el siglo XX una serie de aportes que desafiaron las ideas keynesianas y de la Nueva Macroeconomía Clásica desde un punto de vista praxeológico,desligado de la teoría cuantitativa del dinero y consideraba la idea de los precios relativos. En tal sentido se revisó los aportes realizados por Mises (1982 [1912], (2005 [1936] y Hayek (1967[1931] en el tema de los ciclos económicos para realizar una aproximación a los problemas que afectan la economía venezolana. Se concluye que el impulso monetario en el marco de una economía rentística, de políticas públicas intervencionistas y el crédito blando, en un escenario de pocas empresas creadoras de bienes de inversión, generó distorsiones en el sistema de precios, de incentivos a la producción, aumento de las importaciones y deterioro del tipo de cambio; es decir, todo aquello que está en contracorriente con la búsqueda del desarrollo económico.

  3. Regulación del ciclo celular y desarrollo de cáncer: perspectivas terapéuticas

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    PERALTA-ZARAGOZA OSCAR

    1997-01-01

    Full Text Available Durante el proceso de transformación de las células normales a células cancerosas, ocurren varias alteraciones genéticas. En este proceso se presenta la pérdida del control de los mecanismos de replicación y reparación del ADN, así como de la segregación del material genético. Aunque las células normales tienen estrategias de defensa contra el desarrollo del cáncer, las células tumorales activan diferentes vías de escape que permiten la progresión de la neoplasia. Avances recientes han permitido enfocar la investigación del cáncer hacia la identificación de algunos de sus factores etiológicos. El estudio del ciclo celular y su regulación han permitido conocer cómo la fidelidad y la integridad de la replicación del genoma son mantenidas por las funciones coordinadas de los puntos de control y de los sistemas de reparación del ADN. El funcionamiento adecuado de estos procesos puede ser alterado por mutaciones genéticas. Estos hallazgos sugieren que los mecanismos moleculares de regulación que participan en la transformación celular pueden ser empleados como sistemas potenciales para instrumentar nuevas terapias contra el desarrollo del cáncer.

  4. Los ciclos de generación de competencias y su aplicación en las organizaciones

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    Iván Montoya Restrepo

    2004-12-01

    Full Text Available Los nuevos desafíos que enfrentan las empresas y las organizaciones hacen que éstas deban adaptarse y desarrollarse continuamente para alcanzar un éxito sostenido en un entorno en el que la tecnología y el conocimiento se configuran como ejes de la evolución y el desarrollo. Según Hamel (2000. se ha pasado de la era del progreso, a la era de la revolución, del cambio discontinuo, de la reevaluación de conceptos empresariales, del reconocimiento de un mundo no lineal y. al mismo tiempo, de la solución de los problemas desde esquemas no lineales. En este contexto aparecen nuevos patrones como resultado de evoluciones de la empresa moderna, fundamentadas en la gerencia del conocimiento. El presente documento recoge, la noción de ciclos de generación de competencias y algunas aproximaciones para su aplicación a las organizaciones. Para ello, expone brevemente algunos elementos de la teoría de sistemas y acercamientos a las necesidades en las organizaciones para proponer el desarrollo de la idea central.

  5. CICLO DE VIDA DEL CENTRO HISTÓRICO DE LA CIUDAD DE TOLUCA, ESTADO DE MÉXICO

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    Noé Gaspar Sanchez

    2013-01-01

    Full Text Available La caracterización de las fases de desarroUo del centro histórico de la ciudad de Toluca, la realizamos con base en la retrospectiva del ciclo de vida del producco y el análisis de información histórica, arquirectó. nica, económica y recorridos de campo. Los resultados muestran que el proceso evolurivo es discontinuo, y que las fases de introducción y crecimientosaturación se manifestaron en largos períodos de tiempo, la fase de dedivesaturación exhibe la pérdida de imporcancia del comercio tradicional, el congesrionamienco vial y el abatimicmo del consumo, lo que cuestiona la competitividad económica y social del lugar, freme a los nuevos usos y funciones comerciales que se producen como resultado de las preferencias de consumo cada vez más diversas. La reactivación económica es una fase artificial que prerende prolongar la vida del cenrro hisrórico, y se expresa en acciones de intervención urbana aisladas y en el soslayo de la prevención del fururo.

  6. ESTACIONALIDAD, CICLOS Y VOLATILIDAD EN LOS PRECIOS DEL GANADO MACHO DE LEVANTE EN MONTERÍA, COLOMBIA

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    Omar Castillo N

    2007-08-01

    Full Text Available Objetivo. Describir el comportamiento temporal de los precios del ganado vivo machode levante de primera calidad en la ciudad de Montería, Colombia comercializado enlas subastas. Materiales y métodos. Se realizaron análisis de los precios semanalesy mensuales durante el período 1997-2006 utilizando técnicas estadísticas yeconometricas como la media móvil multiplicativa, la tasa de crecimiento sobre mediasanuales, 1212 T , y modelos auto-regresivos heterocedásticos condicionales, ARCH, oGARCH. Resultados. Se encontraron evidencias de estacionalidad y ciclos en losprecios mensuales; no hubo evidencia de comportamientos volátiles en preciossemanales de los ganados de 1,1¼ y 1½ años de edad, pero si para los de 1 año.Conclusiones. A pesar de la presencia de variaciones estacionales y cíclicas, alrededordel 70% del ganado comercializado presentó estabilidad en los precios.

  7. Coordinated control of a combined cycle thermoelectric central; Control coordinado de una central termoelectrica de ciclo combinado

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Parra, Marino; Castelo Cuevas, Luis [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1998-03-01

    In this paper the coordinated control (CC) of the Distributed Control System (Sistema de Control Distribuido) (SICODI) of the Combined Cycle Central of Gomez Palacio, Durango, is presented. The description of the control scheme and its realization in software is made. From the scheme the operation strategies and automation, supervision and control are described in detail. The software components of the programming are described, the program structure and control data and its implementation in working stations VAX 3100 under the operating system VMS (Virtual Memory System), are described. [Espanol] En este articulo se presenta el control coordinado (CC) del Sistema de Control Distribuido (Sicodi) de la central de ciclo combinado Gomez Palacio, Durango. Se describe el esquema de control y su realizacion en software. Del esquema se detallan las estrategias de operacion y automatizacion, supervision y control. Del software se describen los componentes de la programacion, la estructura de programas y datos del control y su implementacion en estaciones de trabajo VAX 3100 bajo el sistema operativo VMS (Virtual Memory System).

  8. Efeito da seleção no primeiro ciclo de postura para produção de ovos sobre o desempenho no segundo ciclo Improvement in second cycle egg production traits as a response of first cycle selection in leghorn layers

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    Gilberto Silber Schmidt

    2004-02-01

    Full Text Available Utilizou-se uma população selecionada (CC e uma controle (CCc, para avaliar o efeito da seleção, no primeiro ciclo de postura, durante 5 gerações, para características produtivas, sobre o desempenho no segundo ciclo. Avaliou-se o peso corporal (PC na 16ª (PC16, 40ª (PC40, 75ª (PC75 e 111ª (PC111 semana, peso médio do ovo (PMO, idade à maturidade sexual (IMS, produção de ovos ave/dia (POAD da IMS até a 64ª semana, a idade de reinício da postura após a muda (RP, a POAD do RP até a 120ª semana , a relação altura x largura dos ovos (REL e a densidade (DENS. Exceto PC111 e REL, as demais características avaliadas no segundo ciclo apresentaram mudanças genéticas significativas decorrentes da seleção para as mesmas características no primeiro ciclo. Houve incremento na POAD e PC e redução na IMS no primeiro ciclo. No segundo ciclo, foram mantidas as diferenças entre CC e CCc, para as características POAD e IMS, indicando resposta correlacionada entre estas características no primeiro e segundo ciclo. Conclui-se que a seleção para aumento do desempenho produtivo das aves durante o primeiro ciclo de postura mostrou ser eficiente para elevar os níveis de produção no segundo ciclo.An experiment was carried out to evaluate the effect of first cycle selection on second cycle egg production traits. The traits evaluated were body weight at 16 (PC16, 40 (PC40, 75 (PC75 and 111 (PC111 weeks of age; average egg weight (PMO; age at on set production (IMS; hen day egg production (POAD from IMS up to 64 weeks of age; age at first egg after moulting (RP; POAD from RP up to 120 weeks of age; egg shape index (REL and density (DENS. Except PC111 and REL all traits were significantly influenced by first cycle selection. The genetic changes increased in egg production and body weight and decreased in age at onset egg prodution. Differences in egg production and age at onset production between CC and CCc remained in second cycle

  9. Analysis of hyaluronic acid concentration in rat vocal folds during estral and gravidic puerperal cycles Análise da concentração do ácido hialurônico nas pregas vocais de ratas durante o ciclo estral e ciclo gravídico-puerperal

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    José Eduardo de Sá Pedroso

    2009-10-01

    Full Text Available Hormone plays an important role in the larynx. Among other substances, vocal folds contain hyaluronic acid, which tissue concentration may vary according to hormone action. AIM: the objective of this study is to analyze hyaluronic acid concentration in the vocal folds during estral and gravidic-puerperal cycles. MATERIALS AND METHODS: Experimental study. 40 adult rats were divided into two groups. In the first group we used 20 rats to establish the concentration of hyaluronic acid during the estral cycle and in the second group, 20 animals were submitted to the same procedure but during the gravidic-puerperal cycle. RESULTS: Variations in hyaluronic acid concentration was not observed during the estral cycle. In the gravidic puerperal cycle group, an increase in hyaluronic acid concentration was observed in the puerperal subgroup. Comparing the two groups of estral and gravidic-puerperal cycles, no difference was observed. CONCLUSIONS: In comparing all subgroups of estral and gravidic-puerperal cycles, an increase in hyaluronic acid concentration was noticed only in the puerperal phase.Os hormônios exercem importante influência sobre a laringe. A prega vocal contém, entre outras substâncias, o ácido hialurônico, cuja concentração nos tecidos pode variar com a ação dos hormônios. OBJETIVO: O objetivo deste trabalho é analisar comparativamente a concentração do ácido hialurônico nas pregas vocais de ratas durante o ciclo estral e ciclo gravídico-puerperal. FORMA DE ESTUDO: Experimental. MATERIAL E MÉTODO: Foram utilizadas 40 ratas adultas, divididas em dois grupos, no primeiro grupo utilizamos 20 ratas para determinação da concentração do ácido hialurônico no ciclo estral, no segundo grupo, também de 20 animais, foi realizado o mesmo experimento no ciclo gravídico-puerperal. RESULTADOS: No grupo do ciclo estral não observou-se variação da concentração do ácido hialurônico. No grupo do ciclo grav

  10. Reproductive cycle and population structure of the deep-water shrimp Aristeus antillensis A. Milne Edwards & Bouvier, 1909 (Decapoda: Aristeidae on southeast Brazilian continental slope Ciclo reproductivo y estructura poblacional del camarón de aguas profundas Aristeus antillensis A. Milne Edwards & Bouvier, 1909 (Decapoda: Aristeidae en el talud continental del sureste de Brasil

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    Paulo Ricardo Pezzuto

    2009-01-01

    brasileña. Un total de 13.797 camarones fueran muestreados en los buques pesqueros por observadores en casi todos los lances de pesca, que correspondieron entre 10 y 20%> de las capturas totales en el período. Machos y hembras están sexualmente maduros a 25,4 y 40,2 mm respectivamente (longitud de carapazón, según el análisis de las proporciones de individuos con petasma unido (machos y telicum con espermatóforo (hembras. La proporción de hembras con espermatóforo fue superior a 80% en todo el año, sugiriendo un ciclo reproductivo continuo. Sin embargo, informaciones preliminares sobre el desarrollo gonadal indican una posible estacionalidad en la reproducción. Generalmente, hembras adultas, que alcanzan tallas mayores que los machos, dominaron las capturas (M:F = 0,12:1. Sin embargo, grupos poblacionales, incluyendo machos e inmaduros de ambos sexos, ocupan los fondos de pesca en diferentes períodos del año, probablemente como reflejo de los movimientos migratorios, cuyas direcciones y fuerzas aún no son totalmente comprendidos. Se discute una posible estructura poblacional estratificada de sexos y tallas por el gradiente batimétrico.

  11. Caracterização pós-colheita de frutos de bananeira 'BRS Platina' de primeiro ciclo, sob regulação do déficit de irrigação Post harvest characterization of bananas 'BRS Platina' first cycle under regulation of irrigation deficit

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    Ariane Castricini

    2012-12-01

    Full Text Available O trabalho teve como objetivo a caracterização pós-colheita de bananas cv BRS Platina (PA42-44, que é um híbrido tetraploide (AAAB desenvolvido pela Embrapa. As mesmas foram produzidas no norte de Minas Gerais, com redução das lâminas (L de água utilizadas na irrigação,a partir dos cinco meses após o plantio. Foram sete os tratamentos avaliados, com combinações de redução da lâmina (55%, 70% e 85% nas fases II e III de desenvolvimento da planta (5 a 7 meses, e 7 a 12 meses após o plantio, caracterizados quanto a: teor de sólidos solúveis totais (sst, despencamento, firmeza da polpa, comprimento e diâmetro do fruto, relação polpa/casca e coloração da casca, definida pelos parâmetros L*, C* e ºh, avaliados quando os frutos estavam totalmente amarelos. O teor de sólidos solúveis totais foi maior nos frutos do tratamento T3, onde houve redução da lâmina de irrigação na fase II (floração para 70% da ETc. A maior relação polpa/casca foi obtida quando a ETc foi reduzida em 25% na fase III, resistência ao despencamento. Os frutos mais firmes foram produzidos quando a ETc na fase II foi reduzida em 45%; já o menor despencamento foi obtido quando esta redução foi de 45% e 30% na fase II, e de 30% na fase III. Os maiores (comprimento e diâmetro e mais pesados frutos foram produzidos na ausência de déficit hídrico durante todo o ciclo da cultura.The study had as objective the post harvest characterization of bananas cultivar BRS Platina that is a tetraployd hybrid AAAB developed by Embrapa. The crop was grown at North of Minas Gerais with reduction of irrigation water depths (L from five months after planting. Seven treatments were evaluated with different combinations of water depth reductions (55%, 70% and 85% during two phases of crop development (5 to 7 months and 7 to 12 months after planting where fruits were characterized when completely yellow by: total soluble solids (tss, dropping, pulp strength

  12. Determinación de los estados del ciclo de muda de la langosta de Juan Fernández (Jasus frontalis Milne Edwards, 1837 Stages of the molting cycle of the Juan Fernández lobster (Jasus frontalis Milne Edwards, 1837

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    Alvaro Elorza

    1996-01-01

    Full Text Available Se caracterizan los estados del ciclo de muda de Jasus frontalis en base a los cambios morfológicos externos y a la formación de nuevas setas en el ápice de los pleópodos, determinando en forma aproximada los días que faltan para la ecdisis. Al inicio del estado AB el exoesqueleto es flácido, pero a medida que transcurre el tiempo éste comienza a endurecerse. En este estado la epidermis está estrechamente asociada a la cutícula, y el lúmen de la seta presenta un protoplasma granular. Durante el estado C el cefalotórax está totalmente rígido. En el estado D ocurren los mayores cambios morfológicos, asociados al reblandecimiento del caparazón y al proceso de setogénesis. Debido a esto, el estado D se divide en cinco subestados (0 a 4. En el transcurso del subestado D2, las placas branquiostegales del caparazón comienzan a reblandecerse, las cuales pueden ser fácilmente deprimidas en el subestado D4. La determinación de características morfológicas externas detectables, constituye un método fácil, rápido y seguro, tanto para predecir la muda en Jasus frontalis, como para detectar hembras potenciales de ser fecundadas, y que por ende, aportarían miles de huevos a la población de langostas. Debido a esto, los resultados de esta investigación permitirían implementar una nueva medida de manejo tendiente a proteger el potencial reproductivo de esta especie. Esta medida debiera consistir en la prohibición de extraer hembras con los márgenes laterales del caparazón reblandecidos, debido a que estas hembras están sexualmente maduras y que están próximas al apareamiento y/o desove.This study characterizes the stages of Jasus frontalis's moult cycle in base to external morphological changes of the caparace, as well as, setal development at tip of pleopods determining, in approximated form, the days that lack for ecdysis. At the beginning of the stage AB the exoeskeleton is found soft, but it begins to harden at the end of

  13. Ignimbritas riolíticas neoproterozoicas en la Sierra Norte de Córdoba: ¿evidencia de un arco magmático temprano en el ciclo Pampeano? Neoproterozoic rhyolite ignimbrites in the Sierra Norte de Córdoba: evidence of an early magmatic arc in the Pampean cycle?

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    EJ Llambías

    2003-12-01

    Full Text Available La Sierra Norte forma parte de las Sierras Pampeanas de Córdoba por lo cual las principales intrusiones graníticas y el metamorfismo están relacionadas al ciclo orogénico Pampeano. La mayor diferencia con las Sierras de Córdoba es que en Sierra Norte el grado metamórfico es bajo y las intrusiones son superficiales. La Sierra Norte está compuesta por pequeños afloramientos de metasedimentitas, plutones de granodiorita y granito y cuerpos subvolcánicos relacionados a los últimos estadios del batolito. En este trabajo describimos mantos de ignimbritas intercalados en los metaconglomerados de la Formación La Lidia. Las ignimbritas están moderadamente soldadas y está compuestas por aproximadamente 15 % de porfiroclastos de cuarzo, feldespato potásico y plagioclasa totalmente alterada. La pasta consiste de trizas vítreas devitrificadas. La edad U/Pb convencional en circones dio 584+22/-14 Ma y es interpretada como la edad de cristalización. Tanto las ignimbritas como la roca de caja han sido afectadas por un metamorfismo en facies prehnita-pumpellita que alteró la plagioclasa en zoicita, sericita y pumpellita. Las ignimbritas silícicas neoproterozoicas, conjuntamente con el batolito calcoalcalino que le suceden sugiere la existencia de un arco magmático asociado al margen continental activo de Gondwana. Este arco habría estado activo desde el Neoproterozoico hasta el Cámbrico, con una duración de más de 60 Ma. La correlación de las metasedimentitas y volcanitas neoproterozoicas con la Formación Puncoviscana es posible.The Sierra Norte belongs to the Sierras Pampeanas of Córdoba and like in the Sierras de Córdoba the main granitic intrusions, metamorphism and deformation are related to the Pampean orogenic cycle. The most important difference with Sierras de Córdoba is that Sierra Norte shows a weaker deformation and a lower grade metamorphism. Sierra Norte consists of small outcrops of metasedimentary rocks intruded by

  14. Avaliação de três características fisiológicas em 4 ciclos de seleção no cultivar de milho BRS-4154 sob o solo encharcado Evaluation of three physiologic characteristics in four cycles of selection in maize cultivar BRS-4154 under tolerance to waterlogging of the soil

    OpenAIRE

    Juliano Lino Ferreira; Paulo César Magalhães; Aluízio Borém

    2008-01-01

    Conduziu-se este trabalho, com o objetivo de avaliar plantas de milho (Zea mays L.) dos diferentes ciclos de seleção recorrentes da variedade de milho BRS 4154 - 'Saracura' quanto aos ganhos genéticos obtidos ao longo dos ciclos de seleção sob encharcamento do solo. Quatro ciclos de seleção da variedade de milho BRS 4154 foram plantados sob delineamento em blocos casualizados nos quais foram avaliados os ciclos 1, 5, 9 e 15, incluindo a variedade BR 107 e o híbrido simples BRS 1010 como teste...

  15. Development of a plant dynamics computer code for analysis of a supercritical carbon dioxide Brayton cycle energy converter coupled to a natural circulation lead-cooled fast reactor.

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A.; Sienicki, J. J.

    2007-03-08

    STAR-LM is a lead-cooled pool-type fast reactor concept operating under natural circulation of the coolant. The reactor core power is 400 MWt. The open-lattice core consists of fuel pins attached to the core support plate, (the does not consist of removable fuel assemblies). The coolant flows outside of the fuel pins. The fuel is transuranic nitride, fabricated from reprocessed LWR spent fuel. The cladding material is HT-9 stainless steel; the steady-state peak cladding temperature is 650 C. The coolant is single-phase liquid lead under atmospheric pressure; the core inlet and outlet temperatures are 438 C and 578 C, respectively. (The Pb coolant freezing and boiling temperatures are 327 C and 1749 C, respectively). The coolant is contained inside of a reactor vessel. The vessel material is Type 316 stainless steel. The reactor is autonomous meaning that the reactor power is self-regulated based on inherent reactivity feedbacks and no external power control (through control rods) is utilized. The shutdown (scram) control rods are used for startup and shutdown and to stop the fission reaction in case of an emergency. The heat from the reactor is transferred to the S-CO{sub 2} Brayton cycle in in-reactor heat exchangers (IRHX) located inside the reactor vessel. The IRHXs are shell-and-tube type heat exchangers with lead flowing downwards on the shell side and CO{sub 2} flowing upwards on the tube side. No intermediate circuit is utilized. The guard vessel surrounds the reactor vessel to contain the coolant, in the very unlikely event of reactor vessel failure. The Reactor Vessel Auxiliary Cooling System (RVACS) implementing the natural circulation of air flowing upwards over the guard vessel is used to cool the reactor, in the case of loss of normal heat removal through the IRHXs. The RVACS is always in operation. The gap between the vessels is filled with liquid lead-bismuth eutectic (LBE) to enhance the heat removal by air by significantly reducing the thermal

  16. Effects of variable loads on equipment and cogeneration cycles performance; Influencia da variacao da carga no rendimento de equipamentos e ciclos de co-geracao

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, Mario A.B.; Balestieri, Jose A.P. [UNESP, Guaratingueta, SP (Brazil). Escola de Engenharia. Dept. de Engenharia Mecanica]. E-mails: basulto1@uol.com.br; basulto@feg.unesp.br; perella@feg.unesp.br

    2000-07-01

    This article presents some aspects relative to the effects of changing loads on steam.generators and turbines. When the equipment solicitation varies due to industrial process demand changes, the equipment work in off-design point, altering its efficiency and the specific fuel rate. This work do not look for a detailed and exhaustive determination of the performance variation with the load but shows that in the selection of equipment this variation can have effects over the consume and the costs. In the present article it is assumed that the load variations are known, and the effects on the equipment efficiency were took from the correlated literature. An example of a Rankine cycle and other of a Brayton cycle are discussed, altering the operational conditions estimating the operating cost for each case. (author)

  17. Recepción televisiva en la adolescencia: ciclo de vida y gramáticas de reconocimiento

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    Lapuente, Mariano

    2010-01-01

    Full Text Available [es] Este trabajo, producto de una investigación realizada en el Instituto de Comunicación y Diseño (INCOD de la Universidad Argentina de la Empresa (UADE, se dirige a describir algunos de los procesos de producción de sentido que guían la selección y preferencia de programas en el telespectador adolescente1. Es intención avanzar aquí sobre los modos en que un ciclo de vida ejerce su influencia modalizando y condicionando el encuentro que mantiene con la televisión. Nos interesa describir especialmente el modo en que la adolescencia se convierte en una vía de aproximación al actor que se encuentra en la recepción de medios. Para ello hacemos explícito primero nuestro enfoque, circunscribimos una programación que constituye «la pantalla adolescente de la televisión de aire local de 2008» y nos detenemos en las reglas que la adolescencia activa en la recepción de sus programas. [en] This work is part of a study being conducted at the Institute of Design and Communication (INCOD at the Universidad Argentina de la Empresa (UADE. Its main objective is to describe the processes by which the adolescent selects and consumes TV programs. In this study, it is our goal to provide an understanding of how the cycle of life influences, modulates and conditions the relation that the consumer has with the television. We are particularly interested in the way the adolescent functions, as a way of approaching the consumer in the act of media reception. Our work is focused on the “adolescent screen in local television in 2008” from which we analyze the rules that teenagers activate upon the reception of some of its programs.

  18. El ciclo vital revisado: las vidas de las mujeres mayores a la luz de los cambios sociales

    Directory of Open Access Journals (Sweden)

    Anna Freixas Farré

    2012-02-01

    Full Text Available El aumento de la esperanza de vida ha revolucionado la explicación del ciclo vital humano. En el caso de las mujeres podemos identificar en el envejecer elementos diferenciales que tienen su origen en los cambios sociales de los últimos cincuenta años. Las características de la vida de las mujeres y su gran variabilidad interindividual hacen difícil el análisis de su experiencia en términos de las etapas evolutivas clásicas. Las mujeres mayores de los próximos veinte años, beneficiarias de las nuevas posiciones feministas, se enfrentarán a la vejez con experiencias laborales, económicas, familiares, de poder y estatus diferentes a las de sus predecesoras y, por lo tanto, dispondrán de mayores recursos económicos, sociales e intelectuales.Explaining the human lifecycle has been radically changed due to the increase in life expectancy. With regard to women, the aging process involves distinctive elements that are deeply rooted in the social changes of the last fifty years. Given the features of women’s lives and their numerous variations among individuals, the analysis of their experience becomes challenging when performed in terms of classic evolutionary psychology. The women living the aging process in the coming twenty years will benefit from the new feminist positions; they will be confronted with aging after having experienced work, economics, family, power and status positions that differ from those of their predecessors. Thus, they will have more financial, social and intellectual resources at their disposal.

  19. Ciclo reprodutivo de Parauchenipterus striatulus (Pisces - Auchenipteridae na represa de Ribeirão das Lajes - RJ

    Directory of Open Access Journals (Sweden)

    Araújo F.G.

    2000-01-01

    Full Text Available Este trabalho teve como objetivo avaliar o ciclo reprodutivo do bagre de água doce Parauchenipterus striatulus, na represa de Ribeirão das Lajes, Rio de Janeiro. Foram descritos aspectos morfológicos dos estádios de maturação gonadal bem como variações no índice gonadossomático, relação peso:comprimento, fator de condição e condição gonadal. A amostragem dos peixes foi feita bimestralmente entre abril de 1996 e maio de 1997 com o uso de redes de espera de 100m de comprimento, 4m de altura e com malha entre 25 e 65mm de distância entrenós. Os 339 indivíduos capturados ao longo do período de amostragem corresponderam a 40% do total de peixes. Cinco estádios de maturação gonadal foram determinados por meio de análise macroscópica para ambos os sexos: imaturo, maturação I, maturação II, maduro, desovado (fêmeas e esvaziado (machos. O índice gonadossomático foi mais elevado entre outubro e março para ambos os sexos, sugerindo amplo período de desova enquanto o fator de condição atingiu seu máximo entre fevereiro e junho, mostrando uma relação inversa entre essas duas características. A relação peso-comprimento para machos foi de W= 0,0095L3,0862 e fêmeas de W= 0,0116L3,0126, não tendo sido encontradas diferenças significativas entre os coeficientes de alometria para ambos os sexos.

  20. Costos de producción en explotaciones porcinas de ciclo completo en el Municipio Mara, estado Zulia, Venezuela

    Directory of Open Access Journals (Sweden)

    Guillermo Rodríguez Medina

    2012-01-01

    Full Text Available El presente artículo tiene como objetivo analizar los costos de producción en las explotaciones porcinas de ciclo completo en elmunicipioMara, estado Zulia,Venezuela, debido a que es un factor clave para la competitividad del sector, además de ser de gran importancia para la soberanía y seguridad alimentaria de la población. El estudio se sustentó en los enfoques o teorías sobre costos de producción y el conocimiento de las fases de producción del sector, expuestos por los autores Gadd (2005, Guzmán (2007, Sábata (2008, Hansen yMowen (2007, Horngren et al (2007, entre otros. El tipo de investigación fue descriptiva, de diseño no experimental, transeccional y de campo, aplicando un cuestionario a propietarios o administradores de las explotaciones objeto de estudio. Los resultados indican que sólo una granja determina su costo de producción, y todas ellas reconocen el alimento comoel recurso de mayor impacto dentro de los costos directos, pero no conocen la ponderación de los elementos que los integran ni los costos indirectos dentro de la estructura de costo; se concluye que el sector estudiado no realiza una buena gestión de sus costos de producción, lo que restringe el éxito en dichas granjas; por lo que se considera deben asumir recomendaciones para potenciarlo

  1. Influência do ciclo lunar no parto: mito ou constatação científica? Influencia del ciclo lunar en el parto: mito o constatación científica? Influences of lunar cycle in labor: myth or scientific finding?

    OpenAIRE

    Aline Bueno; Isabela Lovizutto Iessi; Débora Cristina Damasceno

    2010-01-01

    Muitas superstições são encontradas em nossas vidas. Na medicina, uma profissão que se orgulha em métodos baseados em evidências para tratamentos, isso não é uma exceção. Uma superstição que abrange o parto é a influência de determinadas fases do ciclo da lua, mais especificamente a lua cheia. Embora estudos tenham demonstrado que o aumento de partos está relacionado com o ciclo lunar, existe discordância sobre quando ocorre o pico do volume de partos em cada fase da lua. Frente à divergência...

  2. A influência do ciclo menstrual na flexibilidade em praticantes de ginástica de academia La influencia del ciclo menstrual sobre la flexibilidad en practicantes de gimnasia de academia The influence of the menstrual cycle on the flexibility in practitioners of gymnastics at fitness centers

    Directory of Open Access Journals (Sweden)

    Solange Mattos Melegario

    2006-06-01

    Full Text Available Este estudo teve por objetivo investigar se existem diferenças no grau de flexibilidade nas fases do ciclo menstrual de mulheres adultas jovens praticantes de ginástica de academia. A amostra intencional foi composta de 20 mulheres, com idade de 18 a 35 anos (25,8 ± 6,06, com o ciclo menstrual regular (28 até 32 dias e que não faziam uso de anticoncepcional oral. Dados referentes ao ciclo menstrual e atividade física habitual foram obtidos através da aplicação de um questionário. A flexibilidade foi aferida através da goniometria, utilizando-se oito movimentos, em três fases do ciclo menstrual. Os sujeitos foram submetidos a um teste hormonal, em que foram verificadas as taxas de estrona, estradiol e progesterona. O tratamento estatístico foi feito através de análise descritiva e inferencial (teste de Kolmogorov-Smirnov e ANOVA. Os resultados encontrados demonstraram que não houve diferença significativa (p Este estudio ha tenido por objetivo investigar si existen diferencias en el grado de flexibilidad en las fases del ciclo menstrual de mujeres adultas jóvenes practicantes de gimnasia de academia. La muestra intencional fue compuesta de 20 mujeres, con edades entre 18 a 35 años (25,8 ± 6,06, con ciclo menstrual regular (28 a 32 días y que no hacían uso de anticonceptivo oral. Datos referentes al ciclo menstrual y actividad física habitual fueron obtenidos a través de una encuesta. La flexibilidad fue medida a través de la goniometría, utilizándose ocho movimientos, en tres fases del ciclo menstrual. Los individuos fueron sometidos a un test hormonal, en donde se verificaron la tasa de estrona, estradiol y progesterona. El tratamiento estadístico fue hecho a través del análisis descriptivo y de inferencia (test de Kolmogorov-Smirnov y ANOVA. Los resultados encontrados mostraron que no hubo diferencia significativa (p This study aims to verify if there are differences in the degree of flexibility in the phases of

  3. Ciclo anual de la clorofila-α satelital en el archipiélago de Juan Fernández (33°S, Chile

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    Isabel Andrade

    2012-09-01

    Full Text Available La variabilidad espacial y temporal del ciclo anual de la clorofila-α en el archipiélago de Juan Fernández se analiza usando ocho anos de datos satelitales de clorofila-α, viento, corrientes y nivel del mar. Este archipiélago está conformado por tres islas: Robinson Crusoe-Santa Clara (RC-SC y Alejandro Selkirk (AS. Las islas RC-SC se encuentran en una región de alta energía cinética y mayores concentraciones de clorofila-α definida como Zona de Transición Costera, en cambio la isla AS se encuentra en una región de baja energía cinética y menores concentraciones de clorofila-α denominada Zona Oceánica. RC-SC posee un incremento de las concentraciones de clorofila-a en el lado suroeste, mientras que AS posee sus mayores concentraciones en el lado oeste, indicando la presencia de procesos forzantes diferentes. En ambas islas el ciclo anual de la clorofila es significativo y comienza a incrementar en abril, alcanzando valores relativamente altos entre junio y noviembre, disminuyendo hacia diciembre, hasta alcanzar un mínimo hacia fines de marzo. Este ciclo anual aparece desacoplado con el viento y acoplado con la energía cinética. Incrementos invernales de clorofila-a aparecen vinculados con remolinos de mesoescala provenientes de la zona continental, mientras que incrementos primaverales se podrían asociar a procesos locales vinculados al "efecto masa de isla". En ambas islas existen incrementos significativos de la clorofila-a en la banda anual y cuasi-bianual, pero sólo en AS se encontró una fluctuación significativa en la banda interanual vinculada con el Nino y la Oscilación del Sur.

  4. Consideraciones para la aplicación del procesamiento ciclo estacionario avanzado al diagnóstico de cojinetes de rodamientos.

    Directory of Open Access Journals (Sweden)

    F. E. Hernández Montero

    2007-05-01

    Full Text Available La aplicación del procesamiento ciclo-estacionario tradicional al análisis de vibraciones para el diagnóstico del estado de los cojinetes de rodamientos presenta un serio problema que se relaciona con la ocurrencia de falsas alarmas. En dos recientes trabajos, sus autores han empleado técnicas diferentes para aplicar el procesamiento ciclo-estacionario “puro”, en aras de resolver este problema. En este trabajo se resumen las bases de estos trabajos y se comparan las técnicas más atractivas presentadas en tales investigaciones. Para efectuar la comparación, se simulan las señales de vibración producidas por fallos locales en cojinetes de rodamientos, a partir de un modelo que constituye el más completo y práctico de los establecidos hasta el momento. Se mostró que el enfoque de aplicación del procesamiento ciclo-estacionario basado en la mediana fue el que mejor resultado ofreció.Traditional cyclostationary processing application on vibration analysis for rolling bearings condition diagnosis carries on a serious problem related to false alarms occurrence. Two recent researches describe the use of different techniques, based upon “pure” cyclostationary processing, in order to solve this problem. In this paper, basis of these works are summarized and the most suited techniques are compared. During comparison, vibrations produced by located rolling bearings failures are simulated using a practical and completed model. The cyclostationary processing application based on the median probed to be more effective.

  5. Prática de ensino supervisionada em ensino do 1º e do 2º ciclo do ensino básico

    OpenAIRE

    Fernandes, Maria da Conceição Veiga Moura

    2011-01-01

    Prática de ensino supervisionada em ensino do 1º e do 2º ciclo do ensino básico The aim of this paper is to reflect the training course, the critical and reflective acts about the challenges, processes and performances of everyday life of professional experience. It was conducted at Agrupamento de Escolas Paulo Quintela, in three classes of 5th grade of the 2nd cycle of basic education, in the scientific areas of history and Geography of Portugal and Natural Sciences (5ºE from February to Jun...

  6. A Escola a Tempo Inteiro no 1º Ciclo:Atividades de Enriquecimento Curricular – Que perceção?

    OpenAIRE

    Bento, Susana

    2014-01-01

    Trabalho de Projeto apresentado para a obtenção do grau de Mestre na Área de Administração Educacional.Orientador: Professor Doutor António Manuel Caldas Mesquita Guimarães A presente investigação enquadra-se nos trabalhos de pesquisa dos estudos curriculares. Foi realizada no sentido analisar, descrever e problematizar a implementação do conceito de escola a tempo inteiro no 1º ciclo do Ensino Básico. Procurámos aferir qual a influência das Atividades Extra Curriculares (AEC) no proce...

  7. Programación para el desarrollo de la inteligencia emocional en el segundo ciclo de Educación Infantil

    OpenAIRE

    Matamoros-García, Laura

    2013-01-01

    El presente Trabajo de Fin de Grado pretende, en una primera parte, hacer una revisión histórica de la evolución del concepto de inteligencia hasta llegar a lo que en la actualidad se denomina inteligencia emocional, su definición y los distintos modelos teóricos desde los que se realizan estudios. La segunda parte del trabajo consiste en una Propuesta de Intervención en el aula para el desarrollo de la inteligencia emocional en los alumnos de Segundo Ciclo de Educación Infantil....

  8. La huerta urbana como un laboratorio para la aplicación del concepto de ecosistema y el desarrollo de habilidades cognitivas en estudiantes de ciclo dos

    OpenAIRE

    Pérez Calderón , Olga Lucía

    2013-01-01

    El presente trabajo es una propuesta de aula que sirve a los maestros como herramienta para orientar procesos académicos en el ciclo II (tercero, cuarto y quinto) del sistema educativo colombiano. Esta propuesta busca dar a conocer el importante papel de la huerta urbana como laboratorio experimental en la aplicación de conceptos en el aula de clase y mostrar que las observaciones, prácticas y experiencias en la huerta urbana son una excelente alternativa para la enseñanza de las Ciencias Nat...

  9. Relatório de estágio pedagógico : Escola Secundária c/3º ciclo de Amato Lusitano

    OpenAIRE

    Duarte, Fábio Henrique Dias

    2012-01-01

    Capítulo 1 Em resultado do trabalho desenvolvido, ao longo do ano letivo 2011/12, no âmbito do Estágio Pedagógico em Educação Física efetuado na Escola Secundária c/3º Ciclo de Amato Lusitano, foram abordadas as diversas áreas-chave que fazem parte dos objetivos/pressupostos do mesmo. O objetivo principal foi descrever toda a minha atividade, enquanto professor estagiário, tentando sempre realçar tanto os aspetos positivos como os negativos, de forma construtiva. De uma forma geral, ...

  10. Ciclo de convesrión de efectivo en las grandes empresas de comercio al detal en Colombia (1998-2002)

    OpenAIRE

    Néstor Moreno Meza

    2004-01-01

    El presente artículo estudia las magnitudes y las implicaciones financieras del ciclo de conversión de efectivo (CCE), concepto desarrollado por Richards y Laughlin (1980) para integrar tres indicadores fundamentales del capital de trabajo y de la gestión del circulante en la empresa comercial, como son los días de inventario, los días de cartera y los días de crédito de proveedores. Estimado a partir de los estados financieros de una muestra de cinco grandes ...

  11. Una aproximaci??n biogr??fica al desarrollo profesional de maestros de educaci??n infantil : ciclo vital, identidad, conocimiento y cultura

    OpenAIRE

    Fern??ndez Cruz, Manuel

    1994-01-01

    Se estudia el desarrollo profesional de profesores de educaci??n infantil en su dimensi??n personal y cultural en los siguientes ??mbitos: (a) el proceso de construcci??n de la identidad profesional docente; (b) el desarrollo del conocimiento pr??ctico del profesor; y (c) la influencia de la cultura organizativa del centro en la vida profesional de los profesores el problema central de la investigaci??n es el estudio de los ciclos vitales de los maestros de educaci??n infa...

  12. Cuestionario de evaluación de la personalidad eficaz en segundo y tercer ciclo de educación primaria

    OpenAIRE

    Eva Fueyo Gutiérrez; María Eugenia Martín Palacio; Bianca Dapelo Pellerano

    2010-01-01

    Se presenta un cuestionario de evaluación del constructoPersonalidad eficaz en contextos educativos de segundo y tercer ciclo de la educación primaria, con resultados de fiabilidad 0.797, validez de constructo, validez concurrente con factores de personalidad de segundo orden de CPQ de Porter y Cattell, y normalización en función de la variable género. Cubrimos así el abanico de cuestionarios elaborados en torno al constructo en contextos de educación secundaria, bachillerato, formación profe...

  13. Un estudio de evaluación sobre el tratamiento de las isometrías en el segundo ciclo de la eso en galicia

    OpenAIRE

    Fernández Blanco, M. Teresa; Cajaraville Pegito, José A.

    2007-01-01

    El objeto de este artículo es presentar un análisis cuantitativo y cualitativo de las respuestas, de una muestra representativa de alumnos de 2º ciclo de la ESO de la comunidad gallega, a una serie de ítems relacionados con las isometrías del plano. Los resultados presentados en este trabajo han sido además confrontados con las directrices del currículo ofi cial como guía propuesta por la Administración Educativa, con el desarrollo que se hace de estas directrices en los libros de texto más u...

  14. La organización escolar por ciclos: sus contribuciones y transformaciones en la política de calidad para Bogotá, Distrito Capital (2009 - 2012)

    OpenAIRE

    Novoa Camargo, Edilberto

    2014-01-01

    La tesis presenta una conceptualización inicial sobre los ciclos; luego identifica los retos sobre los cuales los colegios deben reflexionar para su construcción y también las demandas para la administración del sector educativo en la perspectiva de garantizar la implementación. Asimismo, se presentan los resultados y los hallazgos de la investigación, destacando la voz de los directivos docentes y docentes que compartieron su experiencia en el proceso de la implementación de la propuesta de ...

  15. Inventario para la generación del ciclo de vida del sistema de gestión de residuos urbanos de la ciudad de Tepic, Nayarit

    OpenAIRE

    Hernández Rosales , Paz; Saldaña Duran , Claudia E.; Messina , Sarah

    2012-01-01

    Desde la perspectiva de los negocios sustentables, un análisis de ciclo de vida (ACV), o "análisis de la cuna a la tumba" , o, más comúnmente, balance ambiental , es una herramienta de diseño que investiga y evalúa los impactos ambientales de un producto o servicio durante todas las etapas de su existencia (extracción, producción, distribución, uso y desecho). El objetivo de este estudio es levantar el inventario del ACV de la generación de Residuos Urbanos (RU) de la ciudad de Tepic, Nayari...

  16. Diseño de alojamientos en la explotación porcina de ciclo cerrado "Lurbaiz" sita en el término municipal de Ollo (Navarra)

    OpenAIRE

    Pagola Azkarate, Aitziber

    2014-01-01

    Mediante el presente proyecto fin de grado se realiza el diseño de los alojamientos de una explotación con una futura actividad ganadera porcina de ciclo cerrado. Se sitúa en la parcela 206 del polígono 9 del municipio de Ollo, Navarra. También se desarrollan a lo largo de los distintos anejos los diferentes procesos productivos y las necesidades en instalaciones para un correcto funcionamiento de la explotación conforme a la normativa existente y haciendo especial hincapié en ...

  17. Iniciación a la lecto-escritura con el método Jolly Phonics en el primer ciclo de Educación Primaria

    OpenAIRE

    Calvo Pérez, Elena

    2013-01-01

    El presente proyecto de investigación tiene como finalidad ayudar a responder a las necesidades educativas y a los problemas imperantes en el aula, así como mejorar los procesos de enseñanza-aprendizaje de la lengua inglesa, por ello es necesario destacar la funcionalidad de dicha lengua como instrumento de comunicación, y para ello tomaremos como punto esencial de nuestra investigación el tratamiento de la lecto-escritura en el primer ciclo de Educación Primaria. A lo largo de...

  18. ESTUDIO DE LA RELACIÓN ENTRE DESARROLLO MOTOR Y DETERMINADOS ASPECTOS DE LA ESCRITURA EN ALUMNOS DE SEGUNDO CICLO DE EDUCACIÓN PRIMARIA

    OpenAIRE

    García-Hermosa, Francisco Javier

    2012-01-01

    El Siguiente Trabajo Final de Máster se centra en el análisis de la Motricidad y los procesos de lectura y escritura de alumnos de 2º ciclo de Educación Primaria. Tomando como fundamentación teórica las bases neuropsicológicas de la motricidad, las bases neuropsicológicas del proceso escritor y correlacionando la importancia de los patrones motores básicos para el aprendizaje en general y de la escritura en particular. El presente Trabajo Final de Máster tiene como principal objetivo busca...

  19. Prática de ensino supervisionada em Ensino Pré-Escolar e Ensino do 1º Ciclo do Ensino Básico

    OpenAIRE

    Sendim, Paula Joana Rodrigues

    2013-01-01

    O presente relatório final de estágio surge no âmbito da unidade curricular da Prática de Ensino Supervisionada e pretende descrever e analisar dois estágios pedagógicos: um na Educação Pré-escolar e outro no 1.º Ciclo do Ensino Básico, uma vez que estes constituem-se fundamentais para o desenvolvimento e construção de um ser humano integrado numa sociedade A prática profissional foi assumida como uma etapa fundamental para o nosso desempenho profissional futuro. As instituiçõe...

  20. Prevalência da dislexia entre crianças do 1.º Ciclo do Ensino Básico falantes do português europeu

    OpenAIRE

    Vale, Ana Paula; Sucena, Ana; Viana, Fernanda Leopoldina

    2011-01-01

    O objectivo deste estudo foi determinar a prevalência da dislexia entre as crianças portuguesas do 1º Ciclo do Ensino Básico. Foram avaliadas 1460 crianças dos 2.º, 3.º e 4.º anos de escolaridade relativamente ao nível de leitura e, de acordo com os critérios estabelecidos, 155 dessas crianças foram tambémavaliadas relativamente às capacidades cognitivas gerais e à consciência fonológica. As crianças foram testadas colectivamente nos testes de rastreio e individualmente nos outros testes. ...

  1. Dislexia: conhecimentos de educadores e professores do 1º ciclo do ensino básico na Zona Norte de Portugal

    OpenAIRE

    Sacramento, Patrícia Alexandra da Silva

    2015-01-01

    Dissertação de mestrado em Educação Especial (área de especialização em Dificuldades de Aprendizagem Específicas) O presente trabalho tem como finalidade saber se os educadores do préescolar e os professores do primeiro ciclo estão cientificamente preparados para detetar sinais de Dislexia, identificando, avaliando e intervindo junto dos seus alunos no sentido de prevenirem e reduzirem essas dificuldades. Para o efeito, foram recolhidos dados de 1031 participantes, 342 educa...

  2. Manuais escolares de ciências físico-químicas do 3º ciclo de ensino básico

    OpenAIRE

    Pacheco, Maria Teresa dos Santos

    2007-01-01

    As políticas educativas actuais para o 3º ciclo do Ensino Básico (EB) em Portugal e a investigação em Educação em Ciências valorizam, e defendem, a integração do Trabalho Laboratorial (TL) no Ensino das Ciências em geral e da Física em particular. A implementação do TL deverá contribuir para o desenvolvimento de competências transversais e específicas nos e com os alunos. O principal objectivo desta investigação foi caracterizar as actividades laboratoriais propostas em M...

  3. Mejoramiento de la calidad del cascarón con 25 hidroxicolecalciferol [25-(OH)D3] en dietas de gallinas de primero y segundo ciclos

    OpenAIRE

    Miguel García Hernández; René Morales López; Ernesto Ávila González; Ezequiel Sánchez Ramírez

    2001-01-01

    Con el propósito de estudiar si la adición extra a dietas de gallinas de postura con 25-hidroxicolecalciferol [25- (OH)D3] mejora la calidad de cascarón del huevo, se realizaron dos experimentos con gallinas Isa Babcock B-300 de primero y segundo ciclos, se utilizaron diseños completamente aleatorizados, con arreglos factoriales 2 × 2. Los tratamientos fueron para el Experimento 1: 1. Dieta alta en calcio; 2. Como 1 + 69 mg de 25-(OH)D3 puro (equivalente a 2 000 000 UI de vitamina D3/ton; 3. ...

  4. Ciclo de análisis y mejora de las garantías en John Deere Ibérica, S.A.

    OpenAIRE

    Dueñas Cubillo, Mª Esther

    2010-01-01

    El Proyecto Fin De Carrera “Ciclo de Análisis y Mejora de la Garantías en John Deere Ibérica SA” puede dividirse en cinco bloques principales. El primer bloque se corresponde con el capítulo 2 del proyecto:”El sistema agrícola y John Deere ”, donde se incluyen las características principales propias del sector agrario, mediante un análisis a nivel mundial hasta llegar a las particularidades del sistema español; y en segundo lugar se sitúa primeramente a la empresa Deere & Co de...

  5. Evolución metalogenética de las Sierras Pampeanas de Córdoba y sur de Santiago del Estero: Ciclos prepampeano y pampeano

    Directory of Open Access Journals (Sweden)

    D. Mutti

    2005-03-01

    Full Text Available La hipótesis de evolución metalogenética de las Sierras Pampeanas de Córdoba y sur de Santiago del Estero propone cinco estadios metalogenéticos, de los cuales los dos primeros se abordan en este trabajo: el estadio 1 - vinculado con la apertura y expansión neoproterozoica del océano proto-atlántico - forma parte del ciclo extensional prepampeano. Durante el mismo se generaron depósitos volcanogénicos submarinos de Cu-Fe (Zn-Au-Ag-Co en basaltos, W (B-F-Zn en calizas y dolomías impuras y Fe en sedimentos silicoclásticos, y manifestaciones transicionales entre estos y MVT de Cu (Au-Ag y Pb-Zn (Ag-Cu-Au en calizas y dolomías impuras; a él se asocian concentraciones magmáticas de Cr en tectonitas del manto y de Fe-Ti en ultramafitas-mafitas de la zona de transición corteza-manto. En una reconstrucción global neoproterozoica, se establece la distribución de los depósitos prepampeanos y su relación espacial con los principales distritos volcanogénicos submarinos, SEDEX y MVT del océano protoatlántico. El ciclo compresional pampeano - famatiniano comprende dos estadios. El estadio metalogenético 2 (Neoproterozoico - Cámbrico temprano corresponde al ciclo orogénico pampeano, durante el cual se desarrollaron numerosas estructuras deformaciónales y magmatismo, generandose manifestaciones magmático-metamórficas de Fe-Ti en diques ultramáficos y máficos en tectonitas del manto, manifestaciones metasomáticas de Fe-Ti en rodingitas y pegmatitas portadoras de Be-Li-U-ETR, ademas de transformaciones (metamorfismo, deformación, removilización y recristalización en depósitos de Cr, Cu-Fe (Zn-Au-Ag-Co, W (B-F-Zn, Cu (Au-Ag, Pb-Zn (Ag-Cu-Au y Fe, que condicionan su respuesta magnética. Para los depósitos y manifestaciones de los estadios metalogenéticos descriptos se propone una distribución espacial según fajas vinculadas con megaestructuras activas a partir de los ciclos prepampeano y pampeano, y las asociaciones petrogen

  6. Fenologia, exigência térmica e produtividade de videiras 'Niagara Branca', 'Niagara Rosada 'e 'Concord' submetidas a duas safras por ciclo vegetativo

    OpenAIRE

    Rafael Anzanello; Paulo Vitor Dutra de Souza; Pedro Ferreira Coelho

    2012-01-01

    Este trabalho objetivou avaliar a fenologia, a demanda térmica e a produtividade das cvs. Niagara Branca, Niagara Rosada e Concord submetidas a uma poda seca no inverno e a uma poda verde no final da primavera, visando à obtenção de duas safras de uva por ciclo vegetativo. O experimento foi conduzido em vinhedo pertencente à Estação Experimental Agronômica de Eldorado do Sul-RS, na safra de 2007/2008. As plantas foram submetidas a duas épocas de poda de inverno (22-07-07 e 20-08-07), em cordã...

  7. Fenologia, exigência térmica e produtividade de videiras 'Niagara Branca', 'Niagara Rosada 'e 'Concord' submetidas a duas safras por ciclo vegetativo

    Directory of Open Access Journals (Sweden)

    Rafael Anzanello

    2012-06-01

    Full Text Available Este trabalho objetivou avaliar a fenologia, a demanda térmica e a produtividade das cvs. Niagara Branca, Niagara Rosada e Concord submetidas a uma poda seca no inverno e a uma poda verde no final da primavera, visando à obtenção de duas safras de uva por ciclo vegetativo. O experimento foi conduzido em vinhedo pertencente à Estação Experimental Agronômica de Eldorado do Sul-RS, na safra de 2007/2008. As plantas foram submetidas a duas épocas de poda de inverno (22-07-07 e 20-08-07, em cordão esporonado, e duas épocas de poda verde (15-11-07 e 17-12-07, mediante desponte do sarmento a partir da quarta gema acima do último cacho. Os subperíodos fenológicos considerados da videira foram: vegetativo, compreendendo da poda à brotação e da brotação à floração; e reprodutivo, abrangendo da floração à colheita. Os respectivos intervalos tiveram um acompanhamento com base no acúmulo de graus-dia. A produção por planta, sólidos solúveis totais e acidez total titulável foram avaliados em ambas as safras. As cultivares necessitaram aproximadamente de 1.500 graus-dia para completar seu ciclo, tanto na primeira como na segunda safra. A poda de inverno antecipada aumentou a duração do ciclo fenológico das plantas comparativamente à poda de agosto, devido ao aumento do subperíodo poda/floração nas videiras podadas precocemente. A antecipação da poda de inverno antecipou a colheita da primeira safra, possibilitando obter uvas precoces com maior valorização de mercado. A duração do ciclo fenológico da segunda safra foi menor se comparada à primeira safra, devido às temperaturas mais elevadas decorridas no desenvolvimento das plantas submetidas à poda verde. A produtividade da segunda safra foi maior quando a poda seca foi realizada em agosto, associada à poda verde em novembro. Nas plantas submetidas à poda verde, obteve-se uma segunda colheita em meados de março/abril, oferecendo vantagens econômicas ao

  8. Análisis de la función del antiportador Nha1 en la progresión del ciclo celular en Saccharomyces cerevisiae

    OpenAIRE

    Simón Vecilla, Ernesto

    2003-01-01

    Esta tesis está estructurada en forma de dos publicaciones. En la primera de ellas se utiliza una cepa de Saccharomyces cerevisiae que presenta un fenotipo sintético letal condicional que consiste en una parada del ciclo celular en la fase G1 con el fin de identificar genes que en multicopia revierten este fenotipo. La cepa en cuestión presenta una delección del gen que codifica la fosfatasa Sit4 y una sobreactivación de la fosfatasa Ppz1, que se consigue mediante la represión controlable de ...

  9. Análisis de la función del antiportador Nha1 en la progresión del ciclo celular en Saccharomyces cerevisiae

    OpenAIRE

    Simón Vecilla, Ernesto

    2004-01-01

    Consultable des del TDX Títol obtingut de la portada digitalitzada Esta tesis está estructurada en forma de dos publicaciones. En la primera de ellas se utiliza una cepa de Saccharomyces cerevisiae que presenta un fenotipo sintético letal condicional que consiste en una parada del ciclo celular en la fase G1 con el fin de identificar genes que en multicopia revierten este fenotipo. La cepa en cuestión presenta una delección del gen que codifica la fosfatasa Sit4 y una sobreactivación de...

  10. Los ciclos de manejo, una herramienta útil si es dinámica para evaluar el consumo de combustible y las emisiones contaminantes del auto transporte

    OpenAIRE

    Rogelio González Oropeza

    2005-01-01

    Una revisión de la literatura especializada sobre los ciclos de manejo que se han desarrollado y que se siguen desarrollando en distintos países, permite hacer algunas reflexiones sobre el tema, además de comentar sobre las actividades de experimentación que se han llevado a cabo en el Laboratorio de Control de Emisiones de la Facultad de Ingeniería. Los investigadores de distintos países que trabajan sobre este tema, han reportado cambios en los patrones de conducción, el Federal Test Proced...

  11. La generación de empleo por maquiladoras en México y los ciclos económicos de Estados Unidos 1978-1985

    OpenAIRE

    Jesús H. Amozurrutia C.

    1988-01-01

    Este documento presenta y verifica un modelo explicativo de la relación entre ciclo económico en Estados Unidos y empleo en la industria maquiladora mexicana. Menciona la escasez de trabajos que estudien los mecanismos de generación de empleos en este sector, en tanto que muestra cómo la industria maquiladora ha tenido un ritmo de crecimiento mayor y más estable que la industria manufacturera durante el período de estudio. Presenta una metodología para verificación empírica de las hipótesis, ...

  12. Insuficiencias de la teoría del ciclo vital en el comportamiento ahorrador. El caso de la Comunidad Foral de Navarra

    OpenAIRE

    Lera López, Fernando

    1997-01-01

    Esta investigación muestra la insuficiencia de la teoría del ciclo de vida en la explicación del comportamiento ahorrador. Para ello, se muestran diversas ontrastaciones que muestran la existencia e importancia de las herencias y las donaciones intervivos motivadas por un motivo altruista, y la presencia de ahorro entre los mayores de 65 años. La investigación se completa con una aproximación empírica analizando la motivación de ahorro financiero de los particulares en la Comunidad Foral de...

  13. Irrigação suplementar no ciclo do milho "safrinha" sob plantio direto Supplemental irrigation in the cycle of "safrinha" corn under no-tillage system

    OpenAIRE

    Alexander B Pegorare; Euclides Fedatto; Silvio B. Pereira; Luiz C. F. de Souza; Carlos R. Fietz

    2009-01-01

    Propõe-se, neste trabalho, avaliar diferentes lâminas de água aplicadas como irrigação suplementar no ciclo do milho safrinha, sob plantio direto, sua influência na fisiologia, produtividade e viabilidade econômica na região de Dourados, MS. O trabalho foi conduzido na Faculdade de Ciências Agrárias da Universidade Federal da Grande Dourados, UFGD, no período de março a setembro de 2005. Para a análise dos dados foram determinadas as seguintes características fisiológicas: área foliar, altura...

  14. Propuesta de Intervención Programa de Introducción al Pensamiento Computacional para 2º Ciclo de Educación Infantil

    OpenAIRE

    Vilalta-García, Amankay

    2014-01-01

    El presente trabajo trata el acercamiento del pensamiento computacional a niños de Segundo Ciclo de Educación Infantil, entendiendo este concepto como la unión de diferentes formas de pensamiento: ingenieril, matemático y científico, que permiten la resolución de problemas concretos a través de la abstracción formal y del mundo real-cotidiano. Para ello, se ha partido de una revisión bibliográfica que nos ha permitido establecer un marco teórico donde se recogen: la concepci...

  15. Análisis del ciclo de vida y las políticas de desarrollo de los clusters de empresas

    OpenAIRE

    Josep Capó-Vicedo

    2011-01-01

    En el presente trabajo se analizan dos aspectos muy concretos de las teorías que estudian las aglomeraciones territoriales de empresas o clusters; por una parte los factores que propician su desarrollo, estudiando de manera especial su origen y ciclo de vida y, por otra, aquellas políticas y acciones que pueden llevarse a cabo para potenciarlos. El trabajo busca obtener una visión de conjunto de los aspectos mencionados, a partir de estudios significativos realizados tanto desde el mundo acad...

  16. La comunicación de las emociones en los juegos reglados del primer ciclo de Educación Primaria

    OpenAIRE

    Rodríguez San Martín, Carlos

    2014-01-01

    Con este trabajo se pretende abordar los aspectos mas significativo de las emociones y, en especial las que se produces en los juegos reglados de Educación Primaria. Además, se ofrece una herramienta pedagógica virtual para utilizarla con los juegos reglados de Educación Física en el primer ciclo, que tiene como objetivo que los alumnos identifiquen las emociones que sienten durante el juego y que, en ocasiones limitan sus capacidades , como primer paso para buscar el autocontrol emocional. Y...

  17. A interactividade na análise postural: um estudo para crianças do 1º ciclo do ensino básico

    OpenAIRE

    Fidalgo, Carla

    2011-01-01

    Actualmente os educadores e professores devem adoptar uma nova postura no sentido da sua actividade profissional ser cada vez mais inovadora, além de potenciarem a aprendizagem dos seus alunos em diferentes áreas do conhecimento. A ergonomia é uma área que não se encontra incluída especificamente em nenhuma área curricular do 1º ciclo do Ensino Básico, no entanto, é de grande importância no sentido de prevenir situações de desconforto e lesões músculo-esqueléticas originados por posturas inco...

  18. Influencia de perturbaciones ambientales de origen antrópico sobre el ciclo de vida de Chordodes nobilii (Gordiida, Nematomorpha)

    OpenAIRE

    Achiorno, Cecilia

    2011-01-01

    En esta Tesis se evalúa por primera vez la sensibilidad de una especie del Phylum Nematomorpha a contaminantes de origen antrópico. La especie estudiada, Chordodes nobilii, pertenece a la Clase Gordiida. Considerando que en la cuenca del río Sauce Grande (Sierra de la Ventana, Provincia de Buenos Aires) se ha observado una disminución en la abundancia y diversidad de gordiidos y que no existe información previa sobre el efecto de los contaminantes sobre el ciclo vital del grupo, el objetiv...

  19. Actividades experimentais sobre a qualidade da água : uma proposta sobre educação ambiental no 1.º ciclo do ensino básico

    OpenAIRE

    Machado, Deolinda; Lima, Nelson

    2004-01-01

    Com a preocupação crescente do uso sustentável da água como recurso natural renovável, uma proposta educativa para os alunos do 4.º ano do Ensino Básico do 1.º Ciclo foi planificada e desenvolvida em contexto de sala de aula. Para o efeito, avaliou-se as concepções alternativas dos alunos antes das actividades experimentais para, de seguida, se ter avaliado o desempenho que as propostas de actividades experimentais tiveram nesses alunos. Como turma controlo, os conteúdos ensina...

  20. eLearning no 1º ciclo do ensino básico : um estudo sobre o ruído

    OpenAIRE

    Ramos, António Augusto Tarrafa

    2006-01-01

    Cada vez mais se torna importante proporcionar aos alunos, desde os anos iniciais de escolaridade, um contacto adequado com as tecnologias da informação e comunicação, nomeadamente para o tratamento de temas específicos, como é o caso do ruído. Neste contexto, a presente dissertação de Mestrado resulta de um estudo efectuado com alunos do 1º Ciclo do Ensino Básico, no ano lectivo de 2004/2005, que perseguiu, como principal finalidade, criar e avaliar o impacto de um módul...